Support for falling back through the list of addresses returned from
[u/mdw/putty] / ssh.c
diff --git a/ssh.c b/ssh.c
index 0edaf93..e693fb6 100644 (file)
--- a/ssh.c
+++ b/ssh.c
@@ -1,4 +1,3 @@
-#include <windows.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <stdarg.h>
 #define TRUE 1
 #endif
 
-#define logevent(s) { logevent(s); \
-                      if ((flags & FLAG_STDERR) && (flags & FLAG_VERBOSE)) \
-                      { fprintf(stderr, "%s\n", s); fflush(stderr); } }
-
-/* logevent, only printf-formatted. */
-void logeventf(char *fmt, ...)
-{
-    va_list ap;
-    char stuff[200];
-
-    va_start(ap, fmt);
-    vsprintf(stuff, fmt, ap);
-    va_end(ap);
-    logevent(stuff);
-}
-
-#define bombout(msg) ( ssh_state = SSH_STATE_CLOSED, \
-                          (s ? sk_close(s), s = NULL : 0), \
-                          logeventf msg, connection_fatal msg )
-
 #define SSH1_MSG_DISCONNECT                       1    /* 0x1 */
 #define SSH1_SMSG_PUBLIC_KEY                      2    /* 0x2 */
 #define SSH1_CMSG_SESSION_KEY                     3    /* 0x3 */
@@ -125,8 +104,9 @@ void logeventf(char *fmt, ...)
  * Packet type contexts, so that ssh2_pkt_type can correctly decode
  * the ambiguous type numbers back into the correct type strings.
  */
-#define SSH2_PKTCTX_DHGROUP1         0x0001
+#define SSH2_PKTCTX_DHGROUP          0x0001
 #define SSH2_PKTCTX_DHGEX            0x0002
+#define SSH2_PKTCTX_KEX_MASK         0x000F
 #define SSH2_PKTCTX_PUBLICKEY        0x0010
 #define SSH2_PKTCTX_PASSWORD         0x0020
 #define SSH2_PKTCTX_KBDINTER         0x0040
@@ -182,12 +162,13 @@ static const char *const ssh2_disconnect_reasons[] = {
 #define BUG_NEEDS_SSH1_PLAIN_PASSWORD            4
 #define BUG_CHOKES_ON_RSA                        8
 #define BUG_SSH2_RSA_PADDING                    16
-
-static int ssh_pkt_ctx = 0;
+#define BUG_SSH2_DERIVEKEY                       32
+#define BUG_SSH2_REKEY                           64
+#define BUG_SSH2_PK_SESSIONID                   128
 
 #define translate(x) if (type == x) return #x
-#define translatec(x,ctx) if (type == x && (ssh_pkt_ctx & ctx)) return #x
-char *ssh1_pkt_type(int type)
+#define translatec(x,ctx) if (type == x && (pkt_ctx & ctx)) return #x
+static char *ssh1_pkt_type(int type)
 {
     translate(SSH1_MSG_DISCONNECT);
     translate(SSH1_SMSG_PUBLIC_KEY);
@@ -232,7 +213,7 @@ char *ssh1_pkt_type(int type)
     translate(SSH1_CMSG_AUTH_CCARD_RESPONSE);
     return "unknown";
 }
-char *ssh2_pkt_type(int type)
+static char *ssh2_pkt_type(int pkt_ctx, int type)
 {
     translate(SSH2_MSG_DISCONNECT);
     translate(SSH2_MSG_IGNORE);
@@ -242,8 +223,8 @@ char *ssh2_pkt_type(int type)
     translate(SSH2_MSG_SERVICE_ACCEPT);
     translate(SSH2_MSG_KEXINIT);
     translate(SSH2_MSG_NEWKEYS);
-    translatec(SSH2_MSG_KEXDH_INIT, SSH2_PKTCTX_DHGROUP1);
-    translatec(SSH2_MSG_KEXDH_REPLY, SSH2_PKTCTX_DHGROUP1);
+    translatec(SSH2_MSG_KEXDH_INIT, SSH2_PKTCTX_DHGROUP);
+    translatec(SSH2_MSG_KEXDH_REPLY, SSH2_PKTCTX_DHGROUP);
     translatec(SSH2_MSG_KEX_DH_GEX_REQUEST, SSH2_PKTCTX_DHGEX);
     translatec(SSH2_MSG_KEX_DH_GEX_GROUP, SSH2_PKTCTX_DHGEX);
     translatec(SSH2_MSG_KEX_DH_GEX_INIT, SSH2_PKTCTX_DHGEX);
@@ -287,53 +268,73 @@ char *ssh2_pkt_type(int type)
     (cp)[2] = (unsigned char)((value) >> 8); \
     (cp)[3] = (unsigned char)(value); }
 
-enum { PKT_END, PKT_INT, PKT_CHAR, PKT_DATA, PKT_STR, PKT_BIGNUM };
+/* Enumeration values for fields in SSH-1 packets */
+enum {
+    PKT_END, PKT_INT, PKT_CHAR, PKT_DATA, PKT_STR, PKT_BIGNUM,
+    /* These values are for communicating relevant semantics of
+     * fields to the packet logging code. */
+    PKTT_OTHER, PKTT_PASSWORD, PKTT_DATA
+};
 
-/* Coroutine mechanics for the sillier bits of the code */
-#define crBegin1       static int crLine = 0;
-#define crBegin2       switch(crLine) { case 0:;
-#define crBegin                crBegin1; crBegin2;
-#define crFinish(z)    } crLine = 0; return (z)
-#define crFinishV      } crLine = 0; return
+/*
+ * Coroutine mechanics for the sillier bits of the code. If these
+ * macros look impenetrable to you, you might find it helpful to
+ * read
+ * 
+ *   http://www.chiark.greenend.org.uk/~sgtatham/coroutines.html
+ * 
+ * which explains the theory behind these macros.
+ * 
+ * In particular, if you are getting `case expression not constant'
+ * errors when building with MS Visual Studio, this is because MS's
+ * Edit and Continue debugging feature causes their compiler to
+ * violate ANSI C. To disable Edit and Continue debugging:
+ * 
+ *  - right-click ssh.c in the FileView
+ *  - click Settings
+ *  - select the C/C++ tab and the General category
+ *  - under `Debug info:', select anything _other_ than `Program
+ *    Database for Edit and Continue'.
+ */
+#define crBegin(v)     { int *crLine = &v; switch(v) { case 0:;
+#define crState(t) \
+    struct t *s; \
+    if (!ssh->t) ssh->t = snew(struct t); \
+    s = ssh->t;
+#define crFinish(z)    } *crLine = 0; return (z); }
+#define crFinishV      } *crLine = 0; return; }
 #define crReturn(z)    \
        do {\
-           crLine=__LINE__; return (z); case __LINE__:;\
+           *crLine =__LINE__; return (z); case __LINE__:;\
        } while (0)
 #define crReturnV      \
        do {\
-           crLine=__LINE__; return; case __LINE__:;\
+           *crLine=__LINE__; return; case __LINE__:;\
        } while (0)
-#define crStop(z)      do{ crLine = 0; return (z); }while(0)
-#define crStopV                do{ crLine = 0; return; }while(0)
+#define crStop(z)      do{ *crLine = 0; return (z); }while(0)
+#define crStopV                do{ *crLine = 0; return; }while(0)
 #define crWaitUntil(c) do { crReturn(0); } while (!(c))
 #define crWaitUntilV(c)        do { crReturnV; } while (!(c))
 
-extern char *x11_init(Socket *, char *, void *);
-extern void x11_close(Socket);
-extern int x11_send(Socket, char *, int);
-extern void x11_invent_auth(char *, int, char *, int);
-extern void x11_unthrottle(Socket s);
-extern void x11_override_throttle(Socket s, int enable);
-
-extern char *pfd_newconnect(Socket * s, char *hostname, int port, void *c);
-extern char *pfd_addforward(char *desthost, int destport, int port);
-extern void pfd_close(Socket s);
-extern int pfd_send(Socket s, char *data, int len);
-extern void pfd_confirm(Socket s);
-extern void pfd_unthrottle(Socket s);
-extern void pfd_override_throttle(Socket s, int enable);
-
-static void ssh2_pkt_init(int pkt_type);
-static void ssh2_pkt_addbool(unsigned char value);
-static void ssh2_pkt_adduint32(unsigned long value);
-static void ssh2_pkt_addstring_start(void);
-static void ssh2_pkt_addstring_str(char *data);
-static void ssh2_pkt_addstring_data(char *data, int len);
-static void ssh2_pkt_addstring(char *data);
-static char *ssh2_mpint_fmt(Bignum b, int *len);
-static void ssh2_pkt_addmp(Bignum b);
-static int ssh2_pkt_construct(void);
-static void ssh2_pkt_send(void);
+typedef struct ssh_tag *Ssh;
+struct Packet;
+
+static struct Packet *ssh2_pkt_init(int pkt_type);
+static void ssh2_pkt_addbool(struct Packet *, unsigned char value);
+static void ssh2_pkt_adduint32(struct Packet *, unsigned long value);
+static void ssh2_pkt_addstring_start(struct Packet *);
+static void ssh2_pkt_addstring_str(struct Packet *, char *data);
+static void ssh2_pkt_addstring_data(struct Packet *, char *data, int len);
+static void ssh2_pkt_addstring(struct Packet *, char *data);
+static unsigned char *ssh2_mpint_fmt(Bignum b, int *len);
+static void ssh2_pkt_addmp(struct Packet *, Bignum b);
+static int ssh2_pkt_construct(Ssh, struct Packet *);
+static void ssh2_pkt_send(Ssh, struct Packet *);
+static void ssh2_pkt_send_noqueue(Ssh, struct Packet *);
+static int do_ssh1_login(Ssh ssh, unsigned char *in, int inlen,
+                        struct Packet *pktin);
+static void do_ssh2_authconn(Ssh ssh, unsigned char *in, int inlen,
+                            struct Packet *pktin);
 
 /*
  * Buffer management constants. There are several of these for
@@ -359,27 +360,32 @@ static void ssh2_pkt_send(void);
 #define SSH1_BUFFER_LIMIT 32768
 #define SSH_MAX_BACKLOG 32768
 #define OUR_V2_WINSIZE 16384
-
-const static struct ssh_kex *kex_algs[] = {
-    &ssh_diffiehellman_gex,
-    &ssh_diffiehellman
-};
+#define OUR_V2_MAXPKT 0x4000UL
 
 const static struct ssh_signkey *hostkey_algs[] = { &ssh_rsa, &ssh_dss };
 
-static void nullmac_key(unsigned char *key)
+static void *nullmac_make_context(void)
+{
+    return NULL;
+}
+static void nullmac_free_context(void *handle)
+{
+}
+static void nullmac_key(void *handle, unsigned char *key)
 {
 }
-static void nullmac_generate(unsigned char *blk, int len,
+static void nullmac_generate(void *handle, unsigned char *blk, int len,
                             unsigned long seq)
 {
 }
-static int nullmac_verify(unsigned char *blk, int len, unsigned long seq)
+static int nullmac_verify(void *handle, unsigned char *blk, int len,
+                         unsigned long seq)
 {
     return 1;
 }
 const static struct ssh_mac ssh_mac_none = {
-    nullmac_key, nullmac_key, nullmac_generate, nullmac_verify, "none", 0
+    nullmac_make_context, nullmac_free_context, nullmac_key,
+    nullmac_generate, nullmac_verify, "none", 0
 };
 const static struct ssh_mac *macs[] = {
     &ssh_sha1, &ssh_md5, &ssh_mac_none
@@ -388,23 +394,27 @@ const static struct ssh_mac *buggymacs[] = {
     &ssh_sha1_buggy, &ssh_md5, &ssh_mac_none
 };
 
-static void ssh_comp_none_init(void)
+static void *ssh_comp_none_init(void)
+{
+    return NULL;
+}
+static void ssh_comp_none_cleanup(void *handle)
 {
 }
-static int ssh_comp_none_block(unsigned char *block, int len,
+static int ssh_comp_none_block(void *handle, unsigned char *block, int len,
                               unsigned char **outblock, int *outlen)
 {
     return 0;
 }
-static int ssh_comp_none_disable(void)
+static int ssh_comp_none_disable(void *handle)
 {
     return 0;
 }
 const static struct ssh_compress ssh_comp_none = {
     "none",
-    ssh_comp_none_init, ssh_comp_none_block,
-    ssh_comp_none_init, ssh_comp_none_block,
-    ssh_comp_none_disable
+    ssh_comp_none_init, ssh_comp_none_cleanup, ssh_comp_none_block,
+    ssh_comp_none_init, ssh_comp_none_cleanup, ssh_comp_none_block,
+    ssh_comp_none_disable, NULL
 };
 extern const struct ssh_compress ssh_zlib;
 const static struct ssh_compress *compressions[] = {
@@ -423,8 +433,19 @@ enum {                                    /* channel types */
  * 2-3-4 tree storing channels.
  */
 struct ssh_channel {
+    Ssh ssh;                          /* pointer back to main context */
     unsigned remoteid, localid;
     int type;
+    /*
+     * In SSH1, this value contains four bits:
+     * 
+     *   1   We have sent SSH1_MSG_CHANNEL_CLOSE.
+     *   2   We have sent SSH1_MSG_CHANNEL_CLOSE_CONFIRMATION.
+     *   4   We have received SSH1_MSG_CHANNEL_CLOSE.
+     *   8   We have received SSH1_MSG_CHANNEL_CLOSE_CONFIRMATION.
+     * 
+     * A channel is completely finished with when all four bits are set.
+     */
     int closes;
     union {
        struct ssh1_data_channel {
@@ -440,7 +461,7 @@ struct ssh_channel {
        struct ssh_agent_channel {
            unsigned char *message;
            unsigned char msglen[4];
-           int lensofar, totallen;
+           unsigned lensofar, totallen;
        } a;
        struct ssh_x11_channel {
            Socket s;
@@ -475,112 +496,308 @@ struct ssh_channel {
  * of its ports was connected to; and _you_ have to remember what
  * local host:port pair went with that port number.
  * 
- * Hence: in SSH 1 this structure stores host:port pairs we intend
- * to allow connections to, and is indexed by those host:port
- * pairs. In SSH 2 it stores a mapping from source port to
- * destination host:port pair, and is indexed by source port.
+ * Hence, in SSH 1 this structure is indexed by destination
+ * host:port pair, whereas in SSH 2 it is indexed by source port.
  */
+struct ssh_portfwd; /* forward declaration */
+
 struct ssh_rportfwd {
     unsigned sport, dport;
     char dhost[256];
+    char *sportdesc;
+    struct ssh_portfwd *pfrec;
+};
+#define free_rportfwd(pf) ( \
+    ((pf) ? (sfree((pf)->sportdesc)) : (void)0 ), sfree(pf) )
+
+/*
+ * Separately to the rportfwd tree (which is for looking up port
+ * open requests from the server), a tree of _these_ structures is
+ * used to keep track of all the currently open port forwardings,
+ * so that we can reconfigure in mid-session if the user requests
+ * it.
+ */
+struct ssh_portfwd {
+    enum { DESTROY, KEEP, CREATE } status;
+    int type;
+    unsigned sport, dport;
+    char *saddr, *daddr;
+    char *sserv, *dserv;
+    struct ssh_rportfwd *remote;
+    int addressfamily;
+    void *local;
 };
+#define free_portfwd(pf) ( \
+    ((pf) ? (sfree((pf)->saddr), sfree((pf)->daddr), \
+            sfree((pf)->sserv), sfree((pf)->dserv)) : (void)0 ), sfree(pf) )
 
 struct Packet {
     long length;
     int type;
+    unsigned long sequence;
     unsigned char *data;
     unsigned char *body;
     long savedpos;
     long maxlen;
-};
+    long encrypted_len;                       /* for SSH2 total-size counting */
 
-static SHA_State exhash, exhashbase;
-
-static Socket s = NULL;
-
-static unsigned char session_key[32];
-static int ssh1_compressing;
-static int ssh1_remote_protoflags;
-static int ssh1_local_protoflags;
-static int ssh_agentfwd_enabled;
-static int ssh_X11_fwd_enabled;
-static int ssh_remote_bugs;
-static const struct ssh_cipher *cipher = NULL;
-static const struct ssh2_cipher *cscipher = NULL;
-static const struct ssh2_cipher *sccipher = NULL;
-static const struct ssh_mac *csmac = NULL;
-static const struct ssh_mac *scmac = NULL;
-static const struct ssh_compress *cscomp = NULL;
-static const struct ssh_compress *sccomp = NULL;
-static const struct ssh_kex *kex = NULL;
-static const struct ssh_signkey *hostkey = NULL;
-static unsigned char ssh2_session_id[20];
-
-static char *savedhost;
-static int savedport;
-static int ssh_send_ok;
-static int ssh_echoing, ssh_editing;
-
-static tree234 *ssh_channels;         /* indexed by local id */
-static struct ssh_channel *mainchan;   /* primary session channel */
-static int ssh_exitcode = -1;
-
-static tree234 *ssh_rportfwds;
-
-static enum {
-    SSH_STATE_PREPACKET,
-    SSH_STATE_BEFORE_SIZE,
-    SSH_STATE_INTERMED,
-    SSH_STATE_SESSION,
-    SSH_STATE_CLOSED
-} ssh_state = SSH_STATE_PREPACKET;
-
-static int size_needed = FALSE, eof_needed = FALSE;
-
-static struct Packet pktin = { 0, 0, NULL, NULL, 0 };
-static struct Packet pktout = { 0, 0, NULL, NULL, 0 };
-static unsigned char *deferred_send_data = NULL;
-static int deferred_len = 0, deferred_size = 0;
+    /*
+     * State associated with packet logging
+     */
+    int logmode;
+    int nblanks;
+    struct logblank_t *blanks;
+};
 
-/*
- * Gross hack: pscp will try to start SFTP but fall back to scp1 if
- * that fails. This variable is the means by which scp.c can reach
- * into the SSH code and find out which one it got.
- */
-int ssh_fallback_cmd = 0;
-
-static int ssh_version;
-static int ssh1_throttle_count;
-static int ssh_overall_bufsize;
-static int ssh_throttled_all;
-static int ssh1_stdout_throttling;
-static void (*ssh_protocol) (unsigned char *in, int inlen, int ispkt);
-static void ssh1_protocol(unsigned char *in, int inlen, int ispkt);
-static void ssh2_protocol(unsigned char *in, int inlen, int ispkt);
-static void ssh_size(void);
-static void ssh_special(Telnet_Special);
+static void ssh1_protocol(Ssh ssh, unsigned char *in, int inlen,
+                         struct Packet *pktin);
+static void ssh2_protocol(Ssh ssh, unsigned char *in, int inlen,
+                         struct Packet *pktin);
+static void ssh1_protocol_setup(Ssh ssh);
+static void ssh2_protocol_setup(Ssh ssh);
+static void ssh_size(void *handle, int width, int height);
+static void ssh_special(void *handle, Telnet_Special);
 static int ssh2_try_send(struct ssh_channel *c);
-static void ssh2_add_channel_data(struct ssh_channel *c, char *buf,
-                                 int len);
-static void ssh_throttle_all(int enable, int bufsize);
+static void ssh2_add_channel_data(struct ssh_channel *c, char *buf, int len);
+static void ssh_throttle_all(Ssh ssh, int enable, int bufsize);
 static void ssh2_set_window(struct ssh_channel *c, unsigned newwin);
-static int (*s_rdpkt) (unsigned char **data, int *datalen);
-static int ssh_sendbuffer(void);
-
-static struct rdpkt1_state_tag {
+static int ssh_sendbuffer(void *handle);
+static int ssh_do_close(Ssh ssh, int notify_exit);
+static unsigned long ssh_pkt_getuint32(struct Packet *pkt);
+static int ssh2_pkt_getbool(struct Packet *pkt);
+static void ssh_pkt_getstring(struct Packet *pkt, char **p, int *length);
+static void ssh2_timer(void *ctx, long now);
+static int do_ssh2_transport(Ssh ssh, unsigned char *in, int inlen,
+                            struct Packet *pktin);
+
+struct rdpkt1_state_tag {
     long len, pad, biglen, to_read;
     unsigned long realcrc, gotcrc;
     unsigned char *p;
     int i;
     int chunk;
-} rdpkt1_state;
+    struct Packet *pktin;
+};
 
-static struct rdpkt2_state_tag {
+struct rdpkt2_state_tag {
     long len, pad, payload, packetlen, maclen;
     int i;
     int cipherblk;
     unsigned long incoming_sequence;
-} rdpkt2_state;
+    struct Packet *pktin;
+};
+
+typedef void (*handler_fn_t)(Ssh ssh, struct Packet *pktin);
+typedef void (*chandler_fn_t)(Ssh ssh, struct Packet *pktin, void *ctx);
+
+struct queued_handler;
+struct queued_handler {
+    int msg1, msg2;
+    chandler_fn_t handler;
+    void *ctx;
+    struct queued_handler *next;
+};
+
+struct ssh_tag {
+    const struct plug_function_table *fn;
+    /* the above field _must_ be first in the structure */
+
+    SHA_State exhash, exhashbase;
+
+    Socket s;
+
+    void *ldisc;
+    void *logctx;
+
+    unsigned char session_key[32];
+    int v1_compressing;
+    int v1_remote_protoflags;
+    int v1_local_protoflags;
+    int agentfwd_enabled;
+    int X11_fwd_enabled;
+    int remote_bugs;
+    const struct ssh_cipher *cipher;
+    void *v1_cipher_ctx;
+    void *crcda_ctx;
+    const struct ssh2_cipher *cscipher, *sccipher;
+    void *cs_cipher_ctx, *sc_cipher_ctx;
+    const struct ssh_mac *csmac, *scmac;
+    void *cs_mac_ctx, *sc_mac_ctx;
+    const struct ssh_compress *cscomp, *sccomp;
+    void *cs_comp_ctx, *sc_comp_ctx;
+    const struct ssh_kex *kex;
+    const struct ssh_signkey *hostkey;
+    unsigned char v2_session_id[20];
+    void *kex_ctx;
+
+    char *savedhost;
+    int savedport;
+    int send_ok;
+    int echoing, editing;
+
+    void *frontend;
+
+    int ospeed, ispeed;                       /* temporaries */
+    int term_width, term_height;
+
+    tree234 *channels;                /* indexed by local id */
+    struct ssh_channel *mainchan;      /* primary session channel */
+    int exitcode;
+    int close_expected;
+
+    tree234 *rportfwds, *portfwds;
+
+    enum {
+       SSH_STATE_PREPACKET,
+       SSH_STATE_BEFORE_SIZE,
+       SSH_STATE_INTERMED,
+       SSH_STATE_SESSION,
+       SSH_STATE_CLOSED
+    } state;
+
+    int size_needed, eof_needed;
+
+    struct Packet **queue;
+    int queuelen, queuesize;
+    int queueing;
+    unsigned char *deferred_send_data;
+    int deferred_len, deferred_size;
+
+    /*
+     * Gross hack: pscp will try to start SFTP but fall back to
+     * scp1 if that fails. This variable is the means by which
+     * scp.c can reach into the SSH code and find out which one it
+     * got.
+     */
+    int fallback_cmd;
+
+    /*
+     * Used for username and password input.
+     */
+    char *userpass_input_buffer;
+    int userpass_input_buflen;
+    int userpass_input_bufpos;
+    int userpass_input_echo;
+
+    int pkt_ctx;
+
+    void *x11auth;
+
+    int version;
+    int v1_throttle_count;
+    int overall_bufsize;
+    int throttled_all;
+    int v1_stdout_throttling;
+    int v2_outgoing_sequence;
+
+    int ssh1_rdpkt_crstate;
+    int ssh2_rdpkt_crstate;
+    int do_ssh_init_crstate;
+    int ssh_gotdata_crstate;
+    int do_ssh1_login_crstate;
+    int do_ssh1_connection_crstate;
+    int do_ssh2_transport_crstate;
+    int do_ssh2_authconn_crstate;
+
+    void *do_ssh_init_state;
+    void *do_ssh1_login_state;
+    void *do_ssh2_transport_state;
+    void *do_ssh2_authconn_state;
+
+    struct rdpkt1_state_tag rdpkt1_state;
+    struct rdpkt2_state_tag rdpkt2_state;
+
+    /* ssh1 and ssh2 use this for different things, but both use it */
+    int protocol_initial_phase_done;
+
+    void (*protocol) (Ssh ssh, unsigned char *in, int inlen,
+                     struct Packet *pkt);
+    struct Packet *(*s_rdpkt) (Ssh ssh, unsigned char **data, int *datalen);
+
+    /*
+     * We maintain a full _copy_ of a Config structure here, not
+     * merely a pointer to it. That way, when we're passed a new
+     * one for reconfiguration, we can check the differences and
+     * potentially reconfigure port forwardings etc in mid-session.
+     */
+    Config cfg;
+
+    /*
+     * Used to transfer data back from async agent callbacks.
+     */
+    void *agent_response;
+    int agent_response_len;
+
+    /*
+     * Dispatch table for packet types that we may have to deal
+     * with at any time.
+     */
+    handler_fn_t packet_dispatch[256];
+
+    /*
+     * Queues of one-off handler functions for success/failure
+     * indications from a request.
+     */
+    struct queued_handler *qhead, *qtail;
+
+    /*
+     * This module deals with sending keepalives.
+     */
+    Pinger pinger;
+
+    /*
+     * Track incoming and outgoing data sizes and time, for
+     * size-based rekeys.
+     */
+    unsigned long incoming_data_size, outgoing_data_size, deferred_data_size;
+    unsigned long max_data_size;
+    int kex_in_progress;
+    long next_rekey, last_rekey;
+    char *deferred_rekey_reason;    /* points to STATIC string; don't free */
+};
+
+#define logevent(s) logevent(ssh->frontend, s)
+
+/* logevent, only printf-formatted. */
+static void logeventf(Ssh ssh, const char *fmt, ...)
+{
+    va_list ap;
+    char *buf;
+
+    va_start(ap, fmt);
+    buf = dupvprintf(fmt, ap);
+    va_end(ap);
+    logevent(buf);
+    sfree(buf);
+}
+
+#define bombout(msg) \
+    do { \
+        char *text = dupprintf msg; \
+       ssh_do_close(ssh, FALSE); \
+        logevent(text); \
+        connection_fatal(ssh->frontend, "%s", text); \
+        sfree(text); \
+    } while (0)
+
+/* Functions to leave bits out of the SSH packet log file. */
+
+static void dont_log_password(Ssh ssh, struct Packet *pkt, int blanktype)
+{
+    if (ssh->cfg.logomitpass)
+       pkt->logmode = blanktype;
+}
+
+static void dont_log_data(Ssh ssh, struct Packet *pkt, int blanktype)
+{
+    if (ssh->cfg.logomitdata)
+       pkt->logmode = blanktype;
+}
+
+static void end_log_omission(Ssh ssh, struct Packet *pkt)
+{
+    pkt->logmode = PKTLOG_EMIT;
+}
 
 static int ssh_channelcmp(void *av, void *bv)
 {
@@ -629,7 +846,52 @@ static int ssh_rportcmp_ssh2(void *av, void *bv)
     return 0;
 }
 
-static int alloc_channel_id(void)
+/*
+ * Special form of strcmp which can cope with NULL inputs. NULL is
+ * defined to sort before even the empty string.
+ */
+static int nullstrcmp(const char *a, const char *b)
+{
+    if (a == NULL && b == NULL)
+       return 0;
+    if (a == NULL)
+       return -1;
+    if (b == NULL)
+       return +1;
+    return strcmp(a, b);
+}
+
+static int ssh_portcmp(void *av, void *bv)
+{
+    struct ssh_portfwd *a = (struct ssh_portfwd *) av;
+    struct ssh_portfwd *b = (struct ssh_portfwd *) bv;
+    int i;
+    if (a->type > b->type)
+       return +1;
+    if (a->type < b->type)
+       return -1;
+    if (a->addressfamily > b->addressfamily)
+       return +1;
+    if (a->addressfamily < b->addressfamily)
+       return -1;
+    if ( (i = nullstrcmp(a->saddr, b->saddr)) != 0)
+       return i < 0 ? -1 : +1;
+    if (a->sport > b->sport)
+       return +1;
+    if (a->sport < b->sport)
+       return -1;
+    if (a->type != 'D') {
+       if ( (i = nullstrcmp(a->daddr, b->daddr)) != 0)
+           return i < 0 ? -1 : +1;
+       if (a->dport > b->dport)
+           return +1;
+       if (a->dport < b->dport)
+           return -1;
+    }
+    return 0;
+}
+
+static int alloc_channel_id(Ssh ssh)
 {
     const unsigned CHANNEL_NUMBER_OFFSET = 256;
     unsigned low, high, mid;
@@ -644,13 +906,13 @@ static int alloc_channel_id(void)
      * everything in that sequence must have ID equal to its tree
      * index plus CHANNEL_NUMBER_OFFSET.)
      */
-    tsize = count234(ssh_channels);
+    tsize = count234(ssh->channels);
 
     low = -1;
     high = tsize;
     while (high - low > 1) {
        mid = (high + low) / 2;
-       c = index234(ssh_channels, mid);
+       c = index234(ssh->channels, mid);
        if (c->localid == mid + CHANNEL_NUMBER_OFFSET)
            low = mid;                 /* this one is fine */
        else
@@ -662,12 +924,12 @@ static int alloc_channel_id(void)
      */
     {
        unsigned i = low + 1 + CHANNEL_NUMBER_OFFSET;
-       assert(NULL == find234(ssh_channels, &i, ssh_channelfind));
+       assert(NULL == find234(ssh->channels, &i, ssh_channelfind));
     }
     return low + 1 + CHANNEL_NUMBER_OFFSET;
 }
 
-static void c_write(char *buf, int len)
+static void c_write(Ssh ssh, const char *buf, int len)
 {
     if ((flags & FLAG_STDERR)) {
        int i;
@@ -676,23 +938,41 @@ static void c_write(char *buf, int len)
                fputc(buf[i], stderr);
        return;
     }
-    from_backend(1, buf, len);
+    from_backend(ssh->frontend, 1, buf, len);
 }
 
-static void c_write_untrusted(char *buf, int len)
+static void c_write_untrusted(Ssh ssh, const char *buf, int len)
 {
     int i;
     for (i = 0; i < len; i++) {
        if (buf[i] == '\n')
-           c_write("\r\n", 2);
+           c_write(ssh, "\r\n", 2);
        else if ((buf[i] & 0x60) || (buf[i] == '\r'))
-           c_write(buf + i, 1);
+           c_write(ssh, buf + i, 1);
     }
 }
 
-static void c_write_str(char *buf)
+static void c_write_str(Ssh ssh, const char *buf)
+{
+    c_write(ssh, buf, strlen(buf));
+}
+
+static void ssh_free_packet(struct Packet *pkt)
+{
+    sfree(pkt->data);
+    sfree(pkt);
+}
+static struct Packet *ssh_new_packet(void)
 {
-    c_write(buf, strlen(buf));
+    struct Packet *pkt = snew(struct Packet);
+
+    pkt->data = NULL;
+    pkt->maxlen = 0;
+    pkt->logmode = PKTLOG_EMIT;
+    pkt->nblanks = 0;
+    pkt->blanks = NULL;
+
+    return pkt;
 }
 
 /*
@@ -700,45 +980,46 @@ static void c_write_str(char *buf)
  * Decipher and verify the packet when it is completely read.
  * Drop SSH1_MSG_DEBUG and SSH1_MSG_IGNORE packets.
  * Update the *data and *datalen variables.
- * Return the additional nr of bytes needed, or 0 when
- * a complete packet is available.
+ * Return a Packet structure when a packet is completed.
  */
-static int ssh1_rdpkt(unsigned char **data, int *datalen)
+static struct Packet *ssh1_rdpkt(Ssh ssh, unsigned char **data, int *datalen)
 {
-    struct rdpkt1_state_tag *st = &rdpkt1_state;
+    struct rdpkt1_state_tag *st = &ssh->rdpkt1_state;
 
-    crBegin;
+    crBegin(ssh->ssh1_rdpkt_crstate);
 
-  next_packet:
+    st->pktin = ssh_new_packet();
 
-    pktin.type = 0;
-    pktin.length = 0;
+    st->pktin->type = 0;
+    st->pktin->length = 0;
 
     for (st->i = st->len = 0; st->i < 4; st->i++) {
        while ((*datalen) == 0)
-           crReturn(4 - st->i);
+           crReturn(NULL);
        st->len = (st->len << 8) + **data;
        (*data)++, (*datalen)--;
     }
 
     st->pad = 8 - (st->len % 8);
     st->biglen = st->len + st->pad;
-    pktin.length = st->len - 5;
+    st->pktin->length = st->len - 5;
 
-    if (pktin.maxlen < st->biglen) {
-       pktin.maxlen = st->biglen;
-       pktin.data = (pktin.data == NULL ? smalloc(st->biglen + APIEXTRA) :
-                     srealloc(pktin.data, st->biglen + APIEXTRA));
-       if (!pktin.data)
-           fatalbox("Out of memory");
+    if (st->biglen < 0) {
+        bombout(("Extremely large packet length from server suggests"
+                " data stream corruption"));
+       ssh_free_packet(st->pktin);
+        crStop(NULL);
     }
 
+    st->pktin->maxlen = st->biglen;
+    st->pktin->data = snewn(st->biglen + APIEXTRA, unsigned char);
+
     st->to_read = st->biglen;
-    st->p = pktin.data;
+    st->p = st->pktin->data;
     while (st->to_read > 0) {
        st->chunk = st->to_read;
        while ((*datalen) == 0)
-           crReturn(st->to_read);
+           crReturn(NULL);
        if (st->chunk > (*datalen))
            st->chunk = (*datalen);
        memcpy(st->p, *data, st->chunk);
@@ -748,121 +1029,103 @@ static int ssh1_rdpkt(unsigned char **data, int *datalen)
        st->to_read -= st->chunk;
     }
 
-    if (cipher && detect_attack(pktin.data, st->biglen, NULL)) {
+    if (ssh->cipher && detect_attack(ssh->crcda_ctx, st->pktin->data,
+                                    st->biglen, NULL)) {
         bombout(("Network attack (CRC compensation) detected!"));
-        crReturn(0);
+       ssh_free_packet(st->pktin);
+        crStop(NULL);
     }
 
-    if (cipher)
-       cipher->decrypt(pktin.data, st->biglen);
+    if (ssh->cipher)
+       ssh->cipher->decrypt(ssh->v1_cipher_ctx, st->pktin->data, st->biglen);
 
-    st->realcrc = crc32(pktin.data, st->biglen - 4);
-    st->gotcrc = GET_32BIT(pktin.data + st->biglen - 4);
+    st->realcrc = crc32_compute(st->pktin->data, st->biglen - 4);
+    st->gotcrc = GET_32BIT(st->pktin->data + st->biglen - 4);
     if (st->gotcrc != st->realcrc) {
        bombout(("Incorrect CRC received on packet"));
-       crReturn(0);
+       ssh_free_packet(st->pktin);
+       crStop(NULL);
     }
 
-    pktin.body = pktin.data + st->pad + 1;
+    st->pktin->body = st->pktin->data + st->pad + 1;
+    st->pktin->savedpos = 0;
 
-    if (ssh1_compressing) {
+    if (ssh->v1_compressing) {
        unsigned char *decompblk;
        int decomplen;
-       zlib_decompress_block(pktin.body - 1, pktin.length + 1,
-                             &decompblk, &decomplen);
-
-       if (pktin.maxlen < st->pad + decomplen) {
-           pktin.maxlen = st->pad + decomplen;
-           pktin.data = srealloc(pktin.data, pktin.maxlen + APIEXTRA);
-           pktin.body = pktin.data + st->pad + 1;
-           if (!pktin.data)
-               fatalbox("Out of memory");
+       if (!zlib_decompress_block(ssh->sc_comp_ctx,
+                                  st->pktin->body - 1, st->pktin->length + 1,
+                                  &decompblk, &decomplen)) {
+           bombout(("Zlib decompression encountered invalid data"));
+           ssh_free_packet(st->pktin);
+           crStop(NULL);
        }
 
-       memcpy(pktin.body - 1, decompblk, decomplen);
+       if (st->pktin->maxlen < st->pad + decomplen) {
+           st->pktin->maxlen = st->pad + decomplen;
+           st->pktin->data = sresize(st->pktin->data,
+                                     st->pktin->maxlen + APIEXTRA,
+                                     unsigned char);
+           st->pktin->body = st->pktin->data + st->pad + 1;
+       }
+
+       memcpy(st->pktin->body - 1, decompblk, decomplen);
        sfree(decompblk);
-       pktin.length = decomplen - 1;
+       st->pktin->length = decomplen - 1;
     }
 
-    pktin.type = pktin.body[-1];
+    st->pktin->type = st->pktin->body[-1];
 
-    log_packet(PKT_INCOMING, pktin.type, ssh1_pkt_type(pktin.type),
-              pktin.body, pktin.length);
-
-    if (pktin.type == SSH1_SMSG_STDOUT_DATA ||
-       pktin.type == SSH1_SMSG_STDERR_DATA ||
-       pktin.type == SSH1_MSG_DEBUG ||
-       pktin.type == SSH1_SMSG_AUTH_TIS_CHALLENGE ||
-       pktin.type == SSH1_SMSG_AUTH_CCARD_CHALLENGE) {
-       long stringlen = GET_32BIT(pktin.body);
-       if (stringlen + 4 != pktin.length) {
-           bombout(("Received data packet with bogus string length"));
-           crReturn(0);
+    /*
+     * Log incoming packet, possibly omitting sensitive fields.
+     */
+    if (ssh->logctx) {
+       int nblanks = 0;
+       struct logblank_t blank;
+       if (ssh->cfg.logomitdata) {
+           int do_blank = FALSE, blank_prefix = 0;
+           /* "Session data" packets - omit the data field */
+           if ((st->pktin->type == SSH1_SMSG_STDOUT_DATA) ||
+               (st->pktin->type == SSH1_SMSG_STDERR_DATA)) {
+               do_blank = TRUE; blank_prefix = 0;
+           } else if (st->pktin->type == SSH1_MSG_CHANNEL_DATA) {
+               do_blank = TRUE; blank_prefix = 4;
+           }
+           if (do_blank) {
+               blank.offset = blank_prefix;
+               blank.len = st->pktin->length;
+               blank.type = PKTLOG_OMIT;
+               nblanks = 1;
+           }
        }
+       log_packet(ssh->logctx,
+                  PKT_INCOMING, st->pktin->type,
+                  ssh1_pkt_type(st->pktin->type),
+                  st->pktin->body, st->pktin->length,
+                  nblanks, &blank);
     }
 
-    if (pktin.type == SSH1_MSG_DEBUG) {
-       /* log debug message */
-       char buf[80];
-       int stringlen = GET_32BIT(pktin.body);
-       strcpy(buf, "Remote: ");
-       if (stringlen > 70)
-           stringlen = 70;
-       memcpy(buf + 8, pktin.body + 4, stringlen);
-       buf[8 + stringlen] = '\0';
-       logevent(buf);
-       goto next_packet;
-    } else if (pktin.type == SSH1_MSG_IGNORE) {
-       /* do nothing */
-       goto next_packet;
-    }
-
-    if (pktin.type == SSH1_MSG_DISCONNECT) {
-       /* log reason code in disconnect message */
-       char buf[256];
-       unsigned msglen = GET_32BIT(pktin.body);
-       unsigned nowlen;
-       strcpy(buf, "Remote sent disconnect: ");
-       nowlen = strlen(buf);
-       if (msglen > sizeof(buf) - nowlen - 1)
-           msglen = sizeof(buf) - nowlen - 1;
-       memcpy(buf + nowlen, pktin.body + 4, msglen);
-       buf[nowlen + msglen] = '\0';
-       /* logevent(buf); (this is now done within the bombout macro) */
-       bombout(("Server sent disconnect message:\n\"%s\"", buf+nowlen));
-       crReturn(0);
-    }
-
-    crFinish(0);
+    crFinish(st->pktin);
 }
 
-static int ssh2_rdpkt(unsigned char **data, int *datalen)
+static struct Packet *ssh2_rdpkt(Ssh ssh, unsigned char **data, int *datalen)
 {
-    struct rdpkt2_state_tag *st = &rdpkt2_state;
+    struct rdpkt2_state_tag *st = &ssh->rdpkt2_state;
 
-    crBegin;
+    crBegin(ssh->ssh2_rdpkt_crstate);
 
-  next_packet:
-    pktin.type = 0;
-    pktin.length = 0;
-    if (sccipher)
-       st->cipherblk = sccipher->blksize;
+    st->pktin = ssh_new_packet();
+
+    st->pktin->type = 0;
+    st->pktin->length = 0;
+    if (ssh->sccipher)
+       st->cipherblk = ssh->sccipher->blksize;
     else
        st->cipherblk = 8;
     if (st->cipherblk < 8)
        st->cipherblk = 8;
 
-    if (pktin.maxlen < st->cipherblk) {
-       pktin.maxlen = st->cipherblk;
-       pktin.data =
-           (pktin.data ==
-            NULL ? smalloc(st->cipherblk +
-                           APIEXTRA) : srealloc(pktin.data,
-                                                st->cipherblk +
-                                                APIEXTRA));
-       if (!pktin.data)
-           fatalbox("Out of memory");
-    }
+    st->pktin->data = snewn(st->cipherblk + APIEXTRA, unsigned char);
 
     /*
      * Acquire and decrypt the first block of the packet. This will
@@ -870,47 +1133,51 @@ static int ssh2_rdpkt(unsigned char **data, int *datalen)
      */
     for (st->i = st->len = 0; st->i < st->cipherblk; st->i++) {
        while ((*datalen) == 0)
-           crReturn(st->cipherblk - st->i);
-       pktin.data[st->i] = *(*data)++;
+           crReturn(NULL);
+       st->pktin->data[st->i] = *(*data)++;
        (*datalen)--;
     }
 
-    if (sccipher)
-       sccipher->decrypt(pktin.data, st->cipherblk);
+    if (ssh->sccipher)
+       ssh->sccipher->decrypt(ssh->sc_cipher_ctx,
+                              st->pktin->data, st->cipherblk);
 
     /*
      * Now get the length and padding figures.
      */
-    st->len = GET_32BIT(pktin.data);
-    st->pad = pktin.data[4];
+    st->len = GET_32BIT(st->pktin->data);
+    st->pad = st->pktin->data[4];
+
+    /*
+     * _Completely_ silly lengths should be stomped on before they
+     * do us any more damage.
+     */
+    if (st->len < 0 || st->pad < 0 || st->len + st->pad < 0) {
+       bombout(("Incoming packet was garbled on decryption"));
+       ssh_free_packet(st->pktin);
+       crStop(NULL);
+    }
 
     /*
      * This enables us to deduce the payload length.
      */
     st->payload = st->len - st->pad - 1;
 
-    pktin.length = st->payload + 5;
+    st->pktin->length = st->payload + 5;
 
     /*
      * So now we can work out the total packet length.
      */
     st->packetlen = st->len + 4;
-    st->maclen = scmac ? scmac->len : 0;
+    st->maclen = ssh->scmac ? ssh->scmac->len : 0;
 
     /*
-     * Adjust memory allocation if packet is too big.
+     * Allocate memory for the rest of the packet.
      */
-    if (pktin.maxlen < st->packetlen + st->maclen) {
-       pktin.maxlen = st->packetlen + st->maclen;
-       pktin.data =
-           (pktin.data ==
-            NULL ? smalloc(pktin.maxlen + APIEXTRA) : srealloc(pktin.data,
-                                                               pktin.maxlen
-                                                               +
-                                                               APIEXTRA));
-       if (!pktin.data)
-           fatalbox("Out of memory");
-    }
+    st->pktin->maxlen = st->packetlen + st->maclen;
+    st->pktin->data = sresize(st->pktin->data,
+                             st->pktin->maxlen + APIEXTRA,
+                             unsigned char);
 
     /*
      * Read and decrypt the remainder of the packet.
@@ -918,25 +1185,30 @@ static int ssh2_rdpkt(unsigned char **data, int *datalen)
     for (st->i = st->cipherblk; st->i < st->packetlen + st->maclen;
         st->i++) {
        while ((*datalen) == 0)
-           crReturn(st->packetlen + st->maclen - st->i);
-       pktin.data[st->i] = *(*data)++;
+           crReturn(NULL);
+       st->pktin->data[st->i] = *(*data)++;
        (*datalen)--;
     }
     /* Decrypt everything _except_ the MAC. */
-    if (sccipher)
-       sccipher->decrypt(pktin.data + st->cipherblk,
-                         st->packetlen - st->cipherblk);
+    if (ssh->sccipher)
+       ssh->sccipher->decrypt(ssh->sc_cipher_ctx,
+                              st->pktin->data + st->cipherblk,
+                              st->packetlen - st->cipherblk);
+
+    st->pktin->encrypted_len = st->packetlen;
 
     /*
      * Check the MAC.
      */
-    if (scmac
-       && !scmac->verify(pktin.data, st->len + 4,
-                         st->incoming_sequence)) {
+    if (ssh->scmac
+       && !ssh->scmac->verify(ssh->sc_mac_ctx, st->pktin->data, st->len + 4,
+                              st->incoming_sequence)) {
        bombout(("Incorrect MAC received on packet"));
-       crReturn(0);
+       ssh_free_packet(st->pktin);
+       crStop(NULL);
     }
-    st->incoming_sequence++;          /* whether or not we MACed */
+
+    st->pktin->sequence = st->incoming_sequence++;
 
     /*
      * Decompress packet payload.
@@ -944,136 +1216,57 @@ static int ssh2_rdpkt(unsigned char **data, int *datalen)
     {
        unsigned char *newpayload;
        int newlen;
-       if (sccomp && sccomp->decompress(pktin.data + 5, pktin.length - 5,
-                                        &newpayload, &newlen)) {
-           if (pktin.maxlen < newlen + 5) {
-               pktin.maxlen = newlen + 5;
-               pktin.data =
-                   (pktin.data ==
-                    NULL ? smalloc(pktin.maxlen +
-                                   APIEXTRA) : srealloc(pktin.data,
-                                                        pktin.maxlen +
-                                                        APIEXTRA));
-               if (!pktin.data)
-                   fatalbox("Out of memory");
+       if (ssh->sccomp &&
+           ssh->sccomp->decompress(ssh->sc_comp_ctx,
+                                   st->pktin->data + 5, st->pktin->length - 5,
+                                   &newpayload, &newlen)) {
+           if (st->pktin->maxlen < newlen + 5) {
+               st->pktin->maxlen = newlen + 5;
+               st->pktin->data = sresize(st->pktin->data,
+                                         st->pktin->maxlen + APIEXTRA,
+                                         unsigned char);
            }
-           pktin.length = 5 + newlen;
-           memcpy(pktin.data + 5, newpayload, newlen);
+           st->pktin->length = 5 + newlen;
+           memcpy(st->pktin->data + 5, newpayload, newlen);
            sfree(newpayload);
        }
     }
 
-    pktin.savedpos = 6;
-    pktin.type = pktin.data[5];
-
-    log_packet(PKT_INCOMING, pktin.type, ssh2_pkt_type(pktin.type),
-              pktin.data+6, pktin.length-6);
+    st->pktin->savedpos = 6;
+    st->pktin->body = st->pktin->data;
+    st->pktin->type = st->pktin->data[5];
 
-    switch (pktin.type) {
-        /*
-         * These packets we must handle instantly.
-         */
-      case SSH2_MSG_DISCONNECT:
-        {
-            /* log reason code in disconnect message */
-            char buf[256];
-            int reason = GET_32BIT(pktin.data + 6);
-            unsigned msglen = GET_32BIT(pktin.data + 10);
-            unsigned nowlen;
-            if (reason > 0 && reason < lenof(ssh2_disconnect_reasons)) {
-                sprintf(buf, "Received disconnect message (%s)",
-                        ssh2_disconnect_reasons[reason]);
-            } else {
-                sprintf(buf, "Received disconnect message (unknown type %d)",
-                        reason);
-            }
-            logevent(buf);
-            strcpy(buf, "Disconnection message text: ");
-            nowlen = strlen(buf);
-            if (msglen > sizeof(buf) - nowlen - 1)
-                msglen = sizeof(buf) - nowlen - 1;
-            memcpy(buf + nowlen, pktin.data + 14, msglen);
-            buf[nowlen + msglen] = '\0';
-            logevent(buf);
-            bombout(("Server sent disconnect message\ntype %d (%s):\n\"%s\"",
-                     reason,
-                     (reason > 0 && reason < lenof(ssh2_disconnect_reasons)) ?
-                     ssh2_disconnect_reasons[reason] : "unknown",
-                     buf+nowlen));
-            crReturn(0);
-        }
-        break;
-      case SSH2_MSG_IGNORE:
-       goto next_packet;
-      case SSH2_MSG_DEBUG:
-       {
-           /* log the debug message */
-           char buf[512];
-           /* int display = pktin.body[6]; */
-           int stringlen = GET_32BIT(pktin.data+7);
-           int prefix;
-           strcpy(buf, "Remote debug message: ");
-           prefix = strlen(buf);
-           if (stringlen > sizeof(buf)-prefix-1)
-               stringlen = sizeof(buf)-prefix-1;
-           memcpy(buf + prefix, pktin.data + 11, stringlen);
-           buf[prefix + stringlen] = '\0';
-           logevent(buf);
+    /*
+     * Log incoming packet, possibly omitting sensitive fields.
+     */
+    if (ssh->logctx) {
+       int nblanks = 0;
+       struct logblank_t blank;
+       if (ssh->cfg.logomitdata) {
+           int do_blank = FALSE, blank_prefix = 0;
+           /* "Session data" packets - omit the data field */
+           if (st->pktin->type == SSH2_MSG_CHANNEL_DATA) {
+               do_blank = TRUE; blank_prefix = 4;
+           } else if (st->pktin->type == SSH2_MSG_CHANNEL_EXTENDED_DATA) {
+               do_blank = TRUE; blank_prefix = 8;
+           }
+           if (do_blank) {
+               blank.offset = blank_prefix;
+               blank.len = (st->pktin->length-6) - blank_prefix;
+               blank.type = PKTLOG_OMIT;
+               nblanks = 1;
+           }
        }
-        goto next_packet;              /* FIXME: print the debug message */
-
-        /*
-         * These packets we need do nothing about here.
-         */
-      case SSH2_MSG_UNIMPLEMENTED:
-      case SSH2_MSG_SERVICE_REQUEST:
-      case SSH2_MSG_SERVICE_ACCEPT:
-      case SSH2_MSG_KEXINIT:
-      case SSH2_MSG_NEWKEYS:
-      case SSH2_MSG_KEXDH_INIT:
-      case SSH2_MSG_KEXDH_REPLY:
-      /* case SSH2_MSG_KEX_DH_GEX_REQUEST: duplicate case value */
-      /* case SSH2_MSG_KEX_DH_GEX_GROUP: duplicate case value */
-      case SSH2_MSG_KEX_DH_GEX_INIT:
-      case SSH2_MSG_KEX_DH_GEX_REPLY:
-      case SSH2_MSG_USERAUTH_REQUEST:
-      case SSH2_MSG_USERAUTH_FAILURE:
-      case SSH2_MSG_USERAUTH_SUCCESS:
-      case SSH2_MSG_USERAUTH_BANNER:
-      case SSH2_MSG_USERAUTH_PK_OK:
-      /* case SSH2_MSG_USERAUTH_PASSWD_CHANGEREQ: duplicate case value */
-      /* case SSH2_MSG_USERAUTH_INFO_REQUEST: duplicate case value */
-      case SSH2_MSG_USERAUTH_INFO_RESPONSE:
-      case SSH2_MSG_GLOBAL_REQUEST:
-      case SSH2_MSG_REQUEST_SUCCESS:
-      case SSH2_MSG_REQUEST_FAILURE:
-      case SSH2_MSG_CHANNEL_OPEN:
-      case SSH2_MSG_CHANNEL_OPEN_CONFIRMATION:
-      case SSH2_MSG_CHANNEL_OPEN_FAILURE:
-      case SSH2_MSG_CHANNEL_WINDOW_ADJUST:
-      case SSH2_MSG_CHANNEL_DATA:
-      case SSH2_MSG_CHANNEL_EXTENDED_DATA:
-      case SSH2_MSG_CHANNEL_EOF:
-      case SSH2_MSG_CHANNEL_CLOSE:
-      case SSH2_MSG_CHANNEL_REQUEST:
-      case SSH2_MSG_CHANNEL_SUCCESS:
-      case SSH2_MSG_CHANNEL_FAILURE:
-        break;
-
-        /*
-         * For anything else we send SSH2_MSG_UNIMPLEMENTED.
-         */
-      default:
-       ssh2_pkt_init(SSH2_MSG_UNIMPLEMENTED);
-       ssh2_pkt_adduint32(st->incoming_sequence - 1);
-       ssh2_pkt_send();
-        break;
+       log_packet(ssh->logctx, PKT_INCOMING, st->pktin->type,
+                  ssh2_pkt_type(ssh->pkt_ctx, st->pktin->type),
+                  st->pktin->data+6, st->pktin->length-6,
+                  nblanks, &blank);
     }
 
-    crFinish(0);
+    crFinish(st->pktin);
 }
 
-static void ssh1_pktout_size(int len)
+static void ssh1_pktout_size(struct Packet *pkt, int len)
 {
     int pad, biglen;
 
@@ -1081,96 +1274,111 @@ static void ssh1_pktout_size(int len)
     pad = 8 - (len % 8);
     biglen = len + pad;
 
-    pktout.length = len - 5;
-    if (pktout.maxlen < biglen) {
-       pktout.maxlen = biglen;
-#ifdef MSCRYPTOAPI
-       /* Allocate enough buffer space for extra block
-        * for MS CryptEncrypt() */
-       pktout.data = (pktout.data == NULL ? smalloc(biglen + 12) :
-                      srealloc(pktout.data, biglen + 12));
-#else
-       pktout.data = (pktout.data == NULL ? smalloc(biglen + 4) :
-                      srealloc(pktout.data, biglen + 4));
-#endif
-       if (!pktout.data)
-           fatalbox("Out of memory");
+    pkt->length = len - 5;
+    if (pkt->maxlen < biglen) {
+       pkt->maxlen = biglen;
+       pkt->data = sresize(pkt->data, biglen + 4 + APIEXTRA, unsigned char);
     }
-    pktout.body = pktout.data + 4 + pad + 1;
+    pkt->body = pkt->data + 4 + pad + 1;
 }
 
-static void s_wrpkt_start(int type, int len)
+static struct Packet *s_wrpkt_start(int type, int len)
 {
-    ssh1_pktout_size(len);
-    pktout.type = type;
+    struct Packet *pkt = ssh_new_packet();
+    ssh1_pktout_size(pkt, len);
+    pkt->type = type;
+    /* Initialise log omission state */
+    pkt->nblanks = 0;
+    pkt->blanks = NULL;
+    return pkt;
 }
 
-static int s_wrpkt_prepare(void)
+static int s_wrpkt_prepare(Ssh ssh, struct Packet *pkt)
 {
-    int pad, len, biglen, i;
+    int pad, biglen, i;
     unsigned long crc;
+#ifdef __SC__
+    /*
+     * XXX various versions of SC (including 8.8.4) screw up the
+     * register allocation in this function and use the same register
+     * (D6) for len and as a temporary, with predictable results.  The
+     * following sledgehammer prevents this.
+     */
+    volatile
+#endif
+    int len;
 
-    pktout.body[-1] = pktout.type;
+    pkt->body[-1] = pkt->type;
 
-    log_packet(PKT_OUTGOING, pktout.type, ssh1_pkt_type(pktout.type),
-              pktout.body, pktout.length);
+    if (ssh->logctx)
+       log_packet(ssh->logctx, PKT_OUTGOING, pkt->type,
+                  ssh1_pkt_type(pkt->type),
+                  pkt->body, pkt->length,
+                  pkt->nblanks, pkt->blanks);
+    sfree(pkt->blanks); pkt->blanks = NULL;
+    pkt->nblanks = 0;
 
-    if (ssh1_compressing) {
+    if (ssh->v1_compressing) {
        unsigned char *compblk;
        int complen;
-       zlib_compress_block(pktout.body - 1, pktout.length + 1,
+       zlib_compress_block(ssh->cs_comp_ctx,
+                           pkt->body - 1, pkt->length + 1,
                            &compblk, &complen);
-       ssh1_pktout_size(complen - 1);
-       memcpy(pktout.body - 1, compblk, complen);
+       ssh1_pktout_size(pkt, complen - 1);
+       memcpy(pkt->body - 1, compblk, complen);
        sfree(compblk);
     }
 
-    len = pktout.length + 5;          /* type and CRC */
+    len = pkt->length + 5;            /* type and CRC */
     pad = 8 - (len % 8);
     biglen = len + pad;
 
     for (i = 0; i < pad; i++)
-       pktout.data[i + 4] = random_byte();
-    crc = crc32(pktout.data + 4, biglen - 4);
-    PUT_32BIT(pktout.data + biglen, crc);
-    PUT_32BIT(pktout.data, len);
+       pkt->data[i + 4] = random_byte();
+    crc = crc32_compute(pkt->data + 4, biglen - 4);
+    PUT_32BIT(pkt->data + biglen, crc);
+    PUT_32BIT(pkt->data, len);
 
-    if (cipher)
-       cipher->encrypt(pktout.data + 4, biglen);
+    if (ssh->cipher)
+       ssh->cipher->encrypt(ssh->v1_cipher_ctx, pkt->data + 4, biglen);
 
     return biglen + 4;
 }
 
-static void s_wrpkt(void)
+static void s_wrpkt(Ssh ssh, struct Packet *pkt)
 {
     int len, backlog;
-    len = s_wrpkt_prepare();
-    backlog = sk_write(s, pktout.data, len);
+    len = s_wrpkt_prepare(ssh, pkt);
+    backlog = sk_write(ssh->s, (char *)pkt->data, len);
     if (backlog > SSH_MAX_BACKLOG)
-       ssh_throttle_all(1, backlog);
+       ssh_throttle_all(ssh, 1, backlog);
 }
 
-static void s_wrpkt_defer(void)
+static void s_wrpkt_defer(Ssh ssh, struct Packet *pkt)
 {
     int len;
-    len = s_wrpkt_prepare();
-    if (deferred_len + len > deferred_size) {
-       deferred_size = deferred_len + len + 128;
-       deferred_send_data = srealloc(deferred_send_data, deferred_size);
+    len = s_wrpkt_prepare(ssh, pkt);
+    if (ssh->deferred_len + len > ssh->deferred_size) {
+       ssh->deferred_size = ssh->deferred_len + len + 128;
+       ssh->deferred_send_data = sresize(ssh->deferred_send_data,
+                                         ssh->deferred_size,
+                                         unsigned char);
     }
-    memcpy(deferred_send_data + deferred_len, pktout.data, len);
-    deferred_len += len;
+    memcpy(ssh->deferred_send_data + ssh->deferred_len, pkt->data, len);
+    ssh->deferred_len += len;
 }
 
 /*
  * Construct a packet with the specified contents.
  */
-static void construct_packet(int pkttype, va_list ap1, va_list ap2)
+static struct Packet *construct_packet(Ssh ssh, int pkttype,
+                                      va_list ap1, va_list ap2)
 {
     unsigned char *p, *argp, argchar;
     unsigned long argint;
     int pktlen, argtype, arglen;
     Bignum bn;
+    struct Packet *pkt;
 
     pktlen = 0;
     while ((argtype = va_arg(ap1, int)) != PKT_END) {
@@ -1180,7 +1388,7 @@ static void construct_packet(int pkttype, va_list ap1, va_list ap2)
            pktlen += 4;
            break;
          case PKT_CHAR:
-           (void) va_arg(ap1, char);
+           (void) va_arg(ap1, int);
            pktlen++;
            break;
          case PKT_DATA:
@@ -1190,70 +1398,107 @@ static void construct_packet(int pkttype, va_list ap1, va_list ap2)
            break;
          case PKT_STR:
            argp = va_arg(ap1, unsigned char *);
-           arglen = strlen(argp);
+           arglen = strlen((char *)argp);
            pktlen += 4 + arglen;
            break;
          case PKT_BIGNUM:
            bn = va_arg(ap1, Bignum);
            pktlen += ssh1_bignum_length(bn);
            break;
+         case PKTT_PASSWORD:
+         case PKTT_DATA:
+         case PKTT_OTHER:
+           /* ignore this pass */
+           break;
          default:
            assert(0);
        }
     }
 
-    s_wrpkt_start(pkttype, pktlen);
-    p = pktout.body;
+    pkt = s_wrpkt_start(pkttype, pktlen);
+    p = pkt->body;
 
     while ((argtype = va_arg(ap2, int)) != PKT_END) {
+       int offset = p - pkt->body, len = 0;
        switch (argtype) {
+         /* Actual fields in the packet */
          case PKT_INT:
            argint = va_arg(ap2, int);
            PUT_32BIT(p, argint);
-           p += 4;
+           len = 4;
            break;
          case PKT_CHAR:
-           argchar = va_arg(ap2, unsigned char);
+           argchar = (unsigned char) va_arg(ap2, int);
            *p = argchar;
-           p++;
+           len = 1;
            break;
          case PKT_DATA:
            argp = va_arg(ap2, unsigned char *);
            arglen = va_arg(ap2, int);
            memcpy(p, argp, arglen);
-           p += arglen;
+           len = arglen;
            break;
          case PKT_STR:
            argp = va_arg(ap2, unsigned char *);
-           arglen = strlen(argp);
+           arglen = strlen((char *)argp);
            PUT_32BIT(p, arglen);
            memcpy(p + 4, argp, arglen);
-           p += 4 + arglen;
+           len = arglen + 4;
            break;
          case PKT_BIGNUM:
            bn = va_arg(ap2, Bignum);
-           p += ssh1_write_bignum(p, bn);
+           len = ssh1_write_bignum(p, bn);
+           break;
+         /* Tokens for modifications to packet logging */
+         case PKTT_PASSWORD:
+           dont_log_password(ssh, pkt, PKTLOG_BLANK);
+           break;
+         case PKTT_DATA:
+           dont_log_data(ssh, pkt, PKTLOG_OMIT);
            break;
+         case PKTT_OTHER:
+           end_log_omission(ssh, pkt);
+           break;
+       }
+       p += len;
+       /* Deal with logfile omission, if required. */
+       if (len && (pkt->logmode != PKTLOG_EMIT)) {
+           pkt->nblanks++;
+           pkt->blanks = sresize(pkt->blanks, pkt->nblanks,
+                                 struct logblank_t);
+           pkt->blanks[pkt->nblanks-1].offset = offset;
+           pkt->blanks[pkt->nblanks-1].len    = len;
+           pkt->blanks[pkt->nblanks-1].type   = pkt->logmode;
        }
     }
+
+    return pkt;
 }
 
-static void send_packet(int pkttype, ...)
+static void send_packet(Ssh ssh, int pkttype, ...)
 {
+    struct Packet *pkt;
     va_list ap1, ap2;
     va_start(ap1, pkttype);
     va_start(ap2, pkttype);
-    construct_packet(pkttype, ap1, ap2);
-    s_wrpkt();
+    pkt = construct_packet(ssh, pkttype, ap1, ap2);
+    va_end(ap2);
+    va_end(ap1);
+    s_wrpkt(ssh, pkt);
+    ssh_free_packet(pkt);
 }
 
-static void defer_packet(int pkttype, ...)
+static void defer_packet(Ssh ssh, int pkttype, ...)
 {
+    struct Packet *pkt;
     va_list ap1, ap2;
     va_start(ap1, pkttype);
     va_start(ap2, pkttype);
-    construct_packet(pkttype, ap1, ap2);
-    s_wrpkt_defer();
+    pkt = construct_packet(ssh, pkttype, ap1, ap2);
+    va_end(ap2);
+    va_end(ap1);
+    s_wrpkt_defer(ssh, pkt);
+    ssh_free_packet(pkt);
 }
 
 static int ssh_versioncmp(char *a, char *b)
@@ -1276,7 +1521,6 @@ static int ssh_versioncmp(char *a, char *b)
     return 0;
 }
 
-
 /*
  * Utility routines for putting an SSH-protocol `string' and
  * `uint32' into a SHA state.
@@ -1300,72 +1544,72 @@ static void sha_uint32(SHA_State * s, unsigned i)
 /*
  * SSH2 packet construction functions.
  */
-static void ssh2_pkt_ensure(int length)
-{
-    if (pktout.maxlen < length) {
-       pktout.maxlen = length + 256;
-       pktout.data =
-           (pktout.data ==
-            NULL ? smalloc(pktout.maxlen +
-                           APIEXTRA) : srealloc(pktout.data,
-                                                pktout.maxlen +
-                                                APIEXTRA));
-       if (!pktout.data)
-           fatalbox("Out of memory");
+static void ssh2_pkt_ensure(struct Packet *pkt, int length)
+{
+    if (pkt->maxlen < length) {
+       pkt->maxlen = length + 256;
+       pkt->data = sresize(pkt->data, pkt->maxlen + APIEXTRA, unsigned char);
     }
 }
-static void ssh2_pkt_adddata(void *data, int len)
+static void ssh2_pkt_adddata(struct Packet *pkt, void *data, int len)
 {
-    pktout.length += len;
-    ssh2_pkt_ensure(pktout.length);
-    memcpy(pktout.data + pktout.length - len, data, len);
+    if (pkt->logmode != PKTLOG_EMIT) {
+       pkt->nblanks++;
+       pkt->blanks = sresize(pkt->blanks, pkt->nblanks, struct logblank_t);
+       pkt->blanks[pkt->nblanks-1].offset = pkt->length - 6;
+       pkt->blanks[pkt->nblanks-1].len = len;
+       pkt->blanks[pkt->nblanks-1].type = pkt->logmode;
+    }
+    pkt->length += len;
+    ssh2_pkt_ensure(pkt, pkt->length);
+    memcpy(pkt->data + pkt->length - len, data, len);
 }
-static void ssh2_pkt_addbyte(unsigned char byte)
+static void ssh2_pkt_addbyte(struct Packet *pkt, unsigned char byte)
 {
-    ssh2_pkt_adddata(&byte, 1);
+    ssh2_pkt_adddata(pkt, &byte, 1);
 }
-static void ssh2_pkt_init(int pkt_type)
+static struct Packet *ssh2_pkt_init(int pkt_type)
 {
-    pktout.length = 5;
-    ssh2_pkt_addbyte((unsigned char) pkt_type);
+    struct Packet *pkt = ssh_new_packet();
+    pkt->length = 5;
+    ssh2_pkt_addbyte(pkt, (unsigned char) pkt_type);
+    return pkt;
 }
-static void ssh2_pkt_addbool(unsigned char value)
+static void ssh2_pkt_addbool(struct Packet *pkt, unsigned char value)
 {
-    ssh2_pkt_adddata(&value, 1);
+    ssh2_pkt_adddata(pkt, &value, 1);
 }
-static void ssh2_pkt_adduint32(unsigned long value)
+static void ssh2_pkt_adduint32(struct Packet *pkt, unsigned long value)
 {
     unsigned char x[4];
     PUT_32BIT(x, value);
-    ssh2_pkt_adddata(x, 4);
+    ssh2_pkt_adddata(pkt, x, 4);
 }
-static void ssh2_pkt_addstring_start(void)
+static void ssh2_pkt_addstring_start(struct Packet *pkt)
 {
-    ssh2_pkt_adduint32(0);
-    pktout.savedpos = pktout.length;
+    ssh2_pkt_adduint32(pkt, 0);
+    pkt->savedpos = pkt->length;
 }
-static void ssh2_pkt_addstring_str(char *data)
+static void ssh2_pkt_addstring_str(struct Packet *pkt, char *data)
 {
-    ssh2_pkt_adddata(data, strlen(data));
-    PUT_32BIT(pktout.data + pktout.savedpos - 4,
-             pktout.length - pktout.savedpos);
+    ssh2_pkt_adddata(pkt, data, strlen(data));
+    PUT_32BIT(pkt->data + pkt->savedpos - 4, pkt->length - pkt->savedpos);
 }
-static void ssh2_pkt_addstring_data(char *data, int len)
+static void ssh2_pkt_addstring_data(struct Packet *pkt, char *data, int len)
 {
-    ssh2_pkt_adddata(data, len);
-    PUT_32BIT(pktout.data + pktout.savedpos - 4,
-             pktout.length - pktout.savedpos);
+    ssh2_pkt_adddata(pkt, data, len);
+    PUT_32BIT(pkt->data + pkt->savedpos - 4, pkt->length - pkt->savedpos);
 }
-static void ssh2_pkt_addstring(char *data)
+static void ssh2_pkt_addstring(struct Packet *pkt, char *data)
 {
-    ssh2_pkt_addstring_start();
-    ssh2_pkt_addstring_str(data);
+    ssh2_pkt_addstring_start(pkt);
+    ssh2_pkt_addstring_str(pkt, data);
 }
-static char *ssh2_mpint_fmt(Bignum b, int *len)
+static unsigned char *ssh2_mpint_fmt(Bignum b, int *len)
 {
     unsigned char *p;
     int i, n = (bignum_bitcount(b) + 7) / 8;
-    p = smalloc(n + 1);
+    p = snewn(n + 1, unsigned char);
     if (!p)
        fatalbox("out of memory");
     p[0] = 0;
@@ -1378,28 +1622,32 @@ static char *ssh2_mpint_fmt(Bignum b, int *len)
     *len = n + 1 - i;
     return p;
 }
-static void ssh2_pkt_addmp(Bignum b)
+static void ssh2_pkt_addmp(struct Packet *pkt, Bignum b)
 {
     unsigned char *p;
     int len;
     p = ssh2_mpint_fmt(b, &len);
-    ssh2_pkt_addstring_start();
-    ssh2_pkt_addstring_data(p, len);
+    ssh2_pkt_addstring_start(pkt);
+    ssh2_pkt_addstring_data(pkt, (char *)p, len);
     sfree(p);
 }
 
 /*
  * Construct an SSH2 final-form packet: compress it, encrypt it,
  * put the MAC on it. Final packet, ready to be sent, is stored in
- * pktout.data. Total length is returned.
+ * pkt->data. Total length is returned.
  */
-static int ssh2_pkt_construct(void)
+static int ssh2_pkt_construct(Ssh ssh, struct Packet *pkt)
 {
     int cipherblk, maclen, padding, i;
-    static unsigned long outgoing_sequence = 0;
 
-    log_packet(PKT_OUTGOING, pktout.data[5], ssh2_pkt_type(pktout.data[5]),
-              pktout.data + 6, pktout.length - 6);
+    if (ssh->logctx)
+       log_packet(ssh->logctx, PKT_OUTGOING, pkt->data[5],
+                  ssh2_pkt_type(ssh->pkt_ctx, pkt->data[5]),
+                  pkt->data + 6, pkt->length - 6,
+                  pkt->nblanks, pkt->blanks);
+    sfree(pkt->blanks); pkt->blanks = NULL;
+    pkt->nblanks = 0;
 
     /*
      * Compress packet payload.
@@ -1407,10 +1655,12 @@ static int ssh2_pkt_construct(void)
     {
        unsigned char *newpayload;
        int newlen;
-       if (cscomp && cscomp->compress(pktout.data + 5, pktout.length - 5,
-                                      &newpayload, &newlen)) {
-           pktout.length = 5;
-           ssh2_pkt_adddata(newpayload, newlen);
+       if (ssh->cscomp &&
+           ssh->cscomp->compress(ssh->cs_comp_ctx, pkt->data + 5,
+                                 pkt->length - 5,
+                                 &newpayload, &newlen)) {
+           pkt->length = 5;
+           ssh2_pkt_adddata(pkt, newpayload, newlen);
            sfree(newpayload);
        }
     }
@@ -1419,77 +1669,188 @@ static int ssh2_pkt_construct(void)
      * Add padding. At least four bytes, and must also bring total
      * length (minus MAC) up to a multiple of the block size.
      */
-    cipherblk = cscipher ? cscipher->blksize : 8;      /* block size */
+    cipherblk = ssh->cscipher ? ssh->cscipher->blksize : 8;  /* block size */
     cipherblk = cipherblk < 8 ? 8 : cipherblk; /* or 8 if blksize < 8 */
     padding = 4;
     padding +=
-       (cipherblk - (pktout.length + padding) % cipherblk) % cipherblk;
-    maclen = csmac ? csmac->len : 0;
-    ssh2_pkt_ensure(pktout.length + padding + maclen);
-    pktout.data[4] = padding;
+       (cipherblk - (pkt->length + padding) % cipherblk) % cipherblk;
+    maclen = ssh->csmac ? ssh->csmac->len : 0;
+    ssh2_pkt_ensure(pkt, pkt->length + padding + maclen);
+    pkt->data[4] = padding;
     for (i = 0; i < padding; i++)
-       pktout.data[pktout.length + i] = random_byte();
-    PUT_32BIT(pktout.data, pktout.length + padding - 4);
-    if (csmac)
-       csmac->generate(pktout.data, pktout.length + padding,
-                       outgoing_sequence);
-    outgoing_sequence++;              /* whether or not we MACed */
-
-    if (cscipher)
-       cscipher->encrypt(pktout.data, pktout.length + padding);
-
-    /* Ready-to-send packet starts at pktout.data. We return length. */
-    return pktout.length + padding + maclen;
+       pkt->data[pkt->length + i] = random_byte();
+    PUT_32BIT(pkt->data, pkt->length + padding - 4);
+    if (ssh->csmac)
+       ssh->csmac->generate(ssh->cs_mac_ctx, pkt->data,
+                            pkt->length + padding,
+                            ssh->v2_outgoing_sequence);
+    ssh->v2_outgoing_sequence++;       /* whether or not we MACed */
+
+    if (ssh->cscipher)
+       ssh->cscipher->encrypt(ssh->cs_cipher_ctx,
+                              pkt->data, pkt->length + padding);
+
+    pkt->encrypted_len = pkt->length + padding;
+
+    /* Ready-to-send packet starts at pkt->data. We return length. */
+    return pkt->length + padding + maclen;
 }
 
 /*
- * Construct and send an SSH2 packet immediately.
+ * Routines called from the main SSH code to send packets. There
+ * are quite a few of these, because we have two separate
+ * mechanisms for delaying the sending of packets:
+ * 
+ *  - In order to send an IGNORE message and a password message in
+ *    a single fixed-length blob, we require the ability to
+ *    concatenate the encrypted forms of those two packets _into_ a
+ *    single blob and then pass it to our <network.h> transport
+ *    layer in one go. Hence, there's a deferment mechanism which
+ *    works after packet encryption.
+ * 
+ *  - In order to avoid sending any connection-layer messages
+ *    during repeat key exchange, we have to queue up any such
+ *    outgoing messages _before_ they are encrypted (and in
+ *    particular before they're allocated sequence numbers), and
+ *    then send them once we've finished.
+ * 
+ * I call these mechanisms `defer' and `queue' respectively, so as
+ * to distinguish them reasonably easily.
+ * 
+ * The functions send_noqueue() and defer_noqueue() free the packet
+ * structure they are passed. Every outgoing packet goes through
+ * precisely one of these functions in its life; packets passed to
+ * ssh2_pkt_send() or ssh2_pkt_defer() either go straight to one of
+ * these or get queued, and then when the queue is later emptied
+ * the packets are all passed to defer_noqueue().
+ */
+
+/*
+ * Send an SSH2 packet immediately, without queuing or deferring.
  */
-static void ssh2_pkt_send(void)
+static void ssh2_pkt_send_noqueue(Ssh ssh, struct Packet *pkt)
 {
     int len;
     int backlog;
-    len = ssh2_pkt_construct();
-    backlog = sk_write(s, pktout.data, len);
+    len = ssh2_pkt_construct(ssh, pkt);
+    backlog = sk_write(ssh->s, (char *)pkt->data, len);
     if (backlog > SSH_MAX_BACKLOG)
-       ssh_throttle_all(1, backlog);
+       ssh_throttle_all(ssh, 1, backlog);
+
+    ssh->outgoing_data_size += pkt->encrypted_len;
+    if (!ssh->kex_in_progress &&
+       ssh->max_data_size != 0 &&
+       ssh->outgoing_data_size > ssh->max_data_size)
+       do_ssh2_transport(ssh, "too much data sent", -1, NULL);
+
+    ssh_free_packet(pkt);
 }
 
 /*
- * Construct an SSH2 packet and add it to a deferred data block.
- * Useful for sending multiple packets in a single sk_write() call,
- * to prevent a traffic-analysing listener from being able to work
- * out the length of any particular packet (such as the password
- * packet).
- * 
- * Note that because SSH2 sequence-numbers its packets, this can
- * NOT be used as an m4-style `defer' allowing packets to be
- * constructed in one order and sent in another.
+ * Defer an SSH2 packet.
+ */
+static void ssh2_pkt_defer_noqueue(Ssh ssh, struct Packet *pkt)
+{
+    int len = ssh2_pkt_construct(ssh, pkt);
+    if (ssh->deferred_len + len > ssh->deferred_size) {
+       ssh->deferred_size = ssh->deferred_len + len + 128;
+       ssh->deferred_send_data = sresize(ssh->deferred_send_data,
+                                         ssh->deferred_size,
+                                         unsigned char);
+    }
+    memcpy(ssh->deferred_send_data + ssh->deferred_len, pkt->data, len);
+    ssh->deferred_len += len;
+    ssh->deferred_data_size += pkt->encrypted_len;
+    ssh_free_packet(pkt);
+}
+
+/*
+ * Queue an SSH2 packet.
  */
-static void ssh2_pkt_defer(void)
+static void ssh2_pkt_queue(Ssh ssh, struct Packet *pkt)
 {
-    int len = ssh2_pkt_construct();
-    if (deferred_len + len > deferred_size) {
-       deferred_size = deferred_len + len + 128;
-       deferred_send_data = srealloc(deferred_send_data, deferred_size);
+    assert(ssh->queueing);
+
+    if (ssh->queuelen >= ssh->queuesize) {
+       ssh->queuesize = ssh->queuelen + 32;
+       ssh->queue = sresize(ssh->queue, ssh->queuesize, struct Packet *);
     }
-    memcpy(deferred_send_data + deferred_len, pktout.data, len);
-    deferred_len += len;
+
+    ssh->queue[ssh->queuelen++] = pkt;
+}
+
+/*
+ * Either queue or send a packet, depending on whether queueing is
+ * set.
+ */
+static void ssh2_pkt_send(Ssh ssh, struct Packet *pkt)
+{
+    if (ssh->queueing)
+       ssh2_pkt_queue(ssh, pkt);
+    else
+       ssh2_pkt_send_noqueue(ssh, pkt);
+}
+
+/*
+ * Either queue or defer a packet, depending on whether queueing is
+ * set.
+ */
+static void ssh2_pkt_defer(Ssh ssh, struct Packet *pkt)
+{
+    if (ssh->queueing)
+       ssh2_pkt_queue(ssh, pkt);
+    else
+       ssh2_pkt_defer_noqueue(ssh, pkt);
 }
 
 /*
  * Send the whole deferred data block constructed by
  * ssh2_pkt_defer() or SSH1's defer_packet().
+ * 
+ * The expected use of the defer mechanism is that you call
+ * ssh2_pkt_defer() a few times, then call ssh_pkt_defersend(). If
+ * not currently queueing, this simply sets up deferred_send_data
+ * and then sends it. If we _are_ currently queueing, the calls to
+ * ssh2_pkt_defer() put the deferred packets on to the queue
+ * instead, and therefore ssh_pkt_defersend() has no deferred data
+ * to send. Hence, there's no need to make it conditional on
+ * ssh->queueing.
  */
-static void ssh_pkt_defersend(void)
+static void ssh_pkt_defersend(Ssh ssh)
 {
     int backlog;
-    backlog = sk_write(s, deferred_send_data, deferred_len);
-    deferred_len = deferred_size = 0;
-    sfree(deferred_send_data);
-    deferred_send_data = NULL;
+    backlog = sk_write(ssh->s, (char *)ssh->deferred_send_data,
+                      ssh->deferred_len);
+    ssh->deferred_len = ssh->deferred_size = 0;
+    sfree(ssh->deferred_send_data);
+    ssh->deferred_send_data = NULL;
     if (backlog > SSH_MAX_BACKLOG)
-       ssh_throttle_all(1, backlog);
+       ssh_throttle_all(ssh, 1, backlog);
+
+    ssh->outgoing_data_size += ssh->deferred_data_size;
+    if (!ssh->kex_in_progress &&
+       ssh->max_data_size != 0 &&
+       ssh->outgoing_data_size > ssh->max_data_size)
+       do_ssh2_transport(ssh, "too much data sent", -1, NULL);
+    ssh->deferred_data_size = 0;
+}
+
+/*
+ * Send all queued SSH2 packets. We send them by means of
+ * ssh2_pkt_defer_noqueue(), in case they included a pair of
+ * packets that needed to be lumped together.
+ */
+static void ssh2_pkt_queuesend(Ssh ssh)
+{
+    int i;
+
+    assert(!ssh->queueing);
+
+    for (i = 0; i < ssh->queuelen; i++)
+       ssh2_pkt_defer_noqueue(ssh, ssh->queue[i]);
+    ssh->queuelen = 0;
+
+    ssh_pkt_defersend(ssh);
 }
 
 #if 0
@@ -1516,53 +1877,93 @@ static void sha_mpint(SHA_State * s, Bignum b)
 }
 
 /*
- * SSH2 packet decode functions.
+ * Packet decode functions for both SSH1 and SSH2.
  */
-static unsigned long ssh2_pkt_getuint32(void)
+static unsigned long ssh_pkt_getuint32(struct Packet *pkt)
 {
     unsigned long value;
-    if (pktin.length - pktin.savedpos < 4)
+    if (pkt->length - pkt->savedpos < 4)
        return 0;                      /* arrgh, no way to decline (FIXME?) */
-    value = GET_32BIT(pktin.data + pktin.savedpos);
-    pktin.savedpos += 4;
+    value = GET_32BIT(pkt->body + pkt->savedpos);
+    pkt->savedpos += 4;
     return value;
 }
-static int ssh2_pkt_getbool(void)
+static int ssh2_pkt_getbool(struct Packet *pkt)
 {
     unsigned long value;
-    if (pktin.length - pktin.savedpos < 1)
+    if (pkt->length - pkt->savedpos < 1)
        return 0;                      /* arrgh, no way to decline (FIXME?) */
-    value = pktin.data[pktin.savedpos] != 0;
-    pktin.savedpos++;
+    value = pkt->body[pkt->savedpos] != 0;
+    pkt->savedpos++;
     return value;
 }
-static void ssh2_pkt_getstring(char **p, int *length)
+static void ssh_pkt_getstring(struct Packet *pkt, char **p, int *length)
 {
+    int len;
     *p = NULL;
     *length = 0;
-    if (pktin.length - pktin.savedpos < 4)
+    if (pkt->length - pkt->savedpos < 4)
        return;
-    *length = GET_32BIT(pktin.data + pktin.savedpos);
-    pktin.savedpos += 4;
-    if (pktin.length - pktin.savedpos < *length)
+    len = GET_32BIT(pkt->body + pkt->savedpos);
+    if (len < 0)
        return;
-    *p = pktin.data + pktin.savedpos;
-    pktin.savedpos += *length;
+    *length = len;
+    pkt->savedpos += 4;
+    if (pkt->length - pkt->savedpos < *length)
+       return;
+    *p = (char *)(pkt->body + pkt->savedpos);
+    pkt->savedpos += *length;
+}
+static void *ssh_pkt_getdata(struct Packet *pkt, int length)
+{
+    if (pkt->length - pkt->savedpos < length)
+       return NULL;
+    pkt->savedpos += length;
+    return pkt->body + (pkt->savedpos - length);
+}
+static int ssh1_pkt_getrsakey(struct Packet *pkt, struct RSAKey *key,
+                             unsigned char **keystr)
+{
+    int j;
+
+    j = makekey(pkt->body + pkt->savedpos,
+               pkt->length - pkt->savedpos,
+               key, keystr, 0);
+
+    if (j < 0)
+       return FALSE;
+    
+    pkt->savedpos += j;
+    assert(pkt->savedpos < pkt->length);
+
+    return TRUE;
+}
+static Bignum ssh1_pkt_getmp(struct Packet *pkt)
+{
+    int j;
+    Bignum b;
+
+    j = ssh1_read_bignum(pkt->body + pkt->savedpos,
+                        pkt->length - pkt->savedpos, &b);
+
+    if (j < 0)
+       return NULL;
+
+    pkt->savedpos += j;
+    return b;
 }
-static Bignum ssh2_pkt_getmp(void)
+static Bignum ssh2_pkt_getmp(struct Packet *pkt)
 {
     char *p;
     int length;
     Bignum b;
 
-    ssh2_pkt_getstring(&p, &length);
+    ssh_pkt_getstring(pkt, &p, &length);
     if (!p)
        return NULL;
-    if (p[0] & 0x80) {
-       bombout(("internal error: Can't handle negative mpints"));
+    if (p[0] & 0x80)
        return NULL;
-    }
-    b = bignum_from_bytes(p, length);
+    b = bignum_from_bytes((unsigned char *)p, length);
     return b;
 }
 
@@ -1573,7 +1974,8 @@ static Bignum ssh2_pkt_getmp(void)
  * fiddle with the signature packet if necessary for
  * BUG_SSH2_RSA_PADDING.
  */
-static void ssh2_add_sigblob(void *pkblob_v, int pkblob_len,
+static void ssh2_add_sigblob(Ssh ssh, struct Packet *pkt,
+                            void *pkblob_v, int pkblob_len,
                             void *sigblob_v, int sigblob_len)
 {
     unsigned char *pkblob = (unsigned char *)pkblob_v;
@@ -1586,7 +1988,7 @@ static void ssh2_add_sigblob(void *pkblob_v, int pkblob_len,
      * See if this is in fact an ssh-rsa signature and a buggy
      * server; otherwise we can just do this the easy way.
      */
-    if ((ssh_remote_bugs & BUG_SSH2_RSA_PADDING) &&
+    if ((ssh->remote_bugs & BUG_SSH2_RSA_PADDING) &&
        (GET_32BIT(pkblob) == 7 && !memcmp(pkblob+4, "ssh-rsa", 7))) {
        int pos, len, siglen;
 
@@ -1611,19 +2013,19 @@ static void ssh2_add_sigblob(void *pkblob_v, int pkblob_len,
 
        if (len != siglen) {
            unsigned char newlen[4];
-           ssh2_pkt_addstring_start();
-           ssh2_pkt_addstring_data(sigblob, pos);
+           ssh2_pkt_addstring_start(pkt);
+           ssh2_pkt_addstring_data(pkt, (char *)sigblob, pos);
            /* dmemdump(sigblob, pos); */
            pos += 4;                  /* point to start of actual sig */
            PUT_32BIT(newlen, len);
-           ssh2_pkt_addstring_data(newlen, 4);
+           ssh2_pkt_addstring_data(pkt, (char *)newlen, 4);
            /* dmemdump(newlen, 4); */
            newlen[0] = 0;
            while (len-- > siglen) {
-               ssh2_pkt_addstring_data(newlen, 1);
+               ssh2_pkt_addstring_data(pkt, (char *)newlen, 1);
                /* dmemdump(newlen, 1); */
            }
-           ssh2_pkt_addstring_data(sigblob+pos, siglen);
+           ssh2_pkt_addstring_data(pkt, (char *)(sigblob+pos), siglen);
            /* dmemdump(sigblob+pos, siglen); */
            return;
        }
@@ -1631,15 +2033,15 @@ static void ssh2_add_sigblob(void *pkblob_v, int pkblob_len,
        /* Otherwise fall through and do it the easy way. */
     }
 
-    ssh2_pkt_addstring_start();
-    ssh2_pkt_addstring_data(sigblob, sigblob_len);
+    ssh2_pkt_addstring_start(pkt);
+    ssh2_pkt_addstring_data(pkt, (char *)sigblob, sigblob_len);
 }
 
 /*
  * Examine the remote side's version string and compare it against
  * a list of known buggy implementations.
  */
-static void ssh_detect_bugs(char *vstring)
+static void ssh_detect_bugs(Ssh ssh, char *vstring)
 {
     char *imp;                        /* pointer to implementation part */
     imp = vstring;
@@ -1648,190 +2050,285 @@ static void ssh_detect_bugs(char *vstring)
     imp += strcspn(imp, "-");
     if (*imp) imp++;
 
-    ssh_remote_bugs = 0;
+    ssh->remote_bugs = 0;
 
-    if (!strcmp(imp, "1.2.18") || !strcmp(imp, "1.2.19") ||
-       !strcmp(imp, "1.2.20") || !strcmp(imp, "1.2.21") ||
-       !strcmp(imp, "1.2.22") || !strcmp(imp, "Cisco-1.25")) {
+    if (ssh->cfg.sshbug_ignore1 == FORCE_ON ||
+       (ssh->cfg.sshbug_ignore1 == AUTO &&
+        (!strcmp(imp, "1.2.18") || !strcmp(imp, "1.2.19") ||
+         !strcmp(imp, "1.2.20") || !strcmp(imp, "1.2.21") ||
+         !strcmp(imp, "1.2.22") || !strcmp(imp, "Cisco-1.25") ||
+         !strcmp(imp, "OSU_1.4alpha3") || !strcmp(imp, "OSU_1.5alpha4")))) {
        /*
         * These versions don't support SSH1_MSG_IGNORE, so we have
         * to use a different defence against password length
         * sniffing.
         */
-       ssh_remote_bugs |= BUG_CHOKES_ON_SSH1_IGNORE;
+       ssh->remote_bugs |= BUG_CHOKES_ON_SSH1_IGNORE;
        logevent("We believe remote version has SSH1 ignore bug");
     }
 
-    if (!strcmp(imp, "Cisco-1.25")) {
+    if (ssh->cfg.sshbug_plainpw1 == FORCE_ON ||
+       (ssh->cfg.sshbug_plainpw1 == AUTO &&
+        (!strcmp(imp, "Cisco-1.25") || !strcmp(imp, "OSU_1.4alpha3")))) {
        /*
         * These versions need a plain password sent; they can't
         * handle having a null and a random length of data after
         * the password.
         */
-       ssh_remote_bugs |= BUG_NEEDS_SSH1_PLAIN_PASSWORD;
+       ssh->remote_bugs |= BUG_NEEDS_SSH1_PLAIN_PASSWORD;
        logevent("We believe remote version needs a plain SSH1 password");
     }
 
-    if (!strcmp(imp, "Cisco-1.25")) {
+    if (ssh->cfg.sshbug_rsa1 == FORCE_ON ||
+       (ssh->cfg.sshbug_rsa1 == AUTO &&
+        (!strcmp(imp, "Cisco-1.25")))) {
        /*
         * These versions apparently have no clue whatever about
         * RSA authentication and will panic and die if they see
         * an AUTH_RSA message.
         */
-       ssh_remote_bugs |= BUG_CHOKES_ON_RSA;
+       ssh->remote_bugs |= BUG_CHOKES_ON_RSA;
        logevent("We believe remote version can't handle RSA authentication");
     }
 
-    if (!strncmp(imp, "2.1.0", 5) || !strncmp(imp, "2.0.", 4) ||
-       !strncmp(imp, "2.2.0", 5) || !strncmp(imp, "2.3.0", 5) ||
-       !strncmp(imp, "2.1 ", 4)) {
+    if (ssh->cfg.sshbug_hmac2 == FORCE_ON ||
+       (ssh->cfg.sshbug_hmac2 == AUTO &&
+        !wc_match("* VShell", imp) &&
+        (wc_match("2.1.0*", imp) || wc_match("2.0.*", imp) ||
+         wc_match("2.2.0*", imp) || wc_match("2.3.0*", imp) ||
+         wc_match("2.1 *", imp)))) {
        /*
         * These versions have the HMAC bug.
         */
-       ssh_remote_bugs |= BUG_SSH2_HMAC;
+       ssh->remote_bugs |= BUG_SSH2_HMAC;
        logevent("We believe remote version has SSH2 HMAC bug");
     }
 
-    if ((!strncmp(imp, "OpenSSH_2.", 10) && imp[10]>='5' && imp[10]<='9') ||
-       (!strncmp(imp, "OpenSSH_3.", 10) && imp[10]>='0' && imp[10]<='2')) {
+    if (ssh->cfg.sshbug_derivekey2 == FORCE_ON ||
+       (ssh->cfg.sshbug_derivekey2 == AUTO &&
+        !wc_match("* VShell", imp) &&
+        (wc_match("2.0.0*", imp) || wc_match("2.0.10*", imp) ))) {
+       /*
+        * These versions have the key-derivation bug (failing to
+        * include the literal shared secret in the hashes that
+        * generate the keys).
+        */
+       ssh->remote_bugs |= BUG_SSH2_DERIVEKEY;
+       logevent("We believe remote version has SSH2 key-derivation bug");
+    }
+
+    if (ssh->cfg.sshbug_rsapad2 == FORCE_ON ||
+       (ssh->cfg.sshbug_rsapad2 == AUTO &&
+        (wc_match("OpenSSH_2.[5-9]*", imp) ||
+         wc_match("OpenSSH_3.[0-2]*", imp)))) {
        /*
         * These versions have the SSH2 RSA padding bug.
         */
-       ssh_remote_bugs |= BUG_SSH2_RSA_PADDING;
+       ssh->remote_bugs |= BUG_SSH2_RSA_PADDING;
        logevent("We believe remote version has SSH2 RSA padding bug");
     }
+
+    if (ssh->cfg.sshbug_pksessid2 == FORCE_ON ||
+       (ssh->cfg.sshbug_pksessid2 == AUTO &&
+        wc_match("OpenSSH_2.[0-2]*", imp))) {
+       /*
+        * These versions have the SSH2 session-ID bug in
+        * public-key authentication.
+        */
+       ssh->remote_bugs |= BUG_SSH2_PK_SESSIONID;
+       logevent("We believe remote version has SSH2 public-key-session-ID bug");
+    }
+
+    if (ssh->cfg.sshbug_rekey2 == FORCE_ON ||
+       (ssh->cfg.sshbug_rekey2 == AUTO &&
+        (wc_match("OpenSSH_2.[0-4]*", imp) ||
+         wc_match("OpenSSH_2.5.[0-3]*", imp) ||
+         wc_match("Sun_SSH_1.0", imp) ||
+         wc_match("Sun_SSH_1.0.1", imp)))) {
+       /*
+        * These versions have the SSH2 rekey bug.
+        */
+       ssh->remote_bugs |= BUG_SSH2_REKEY;
+       logevent("We believe remote version has SSH2 rekey bug");
+    }
+}
+
+/*
+ * The `software version' part of an SSH version string is required
+ * to contain no spaces or minus signs.
+ */
+static void ssh_fix_verstring(char *str)
+{
+    /* Eat "SSH-<protoversion>-". */
+    assert(*str == 'S'); str++;
+    assert(*str == 'S'); str++;
+    assert(*str == 'H'); str++;
+    assert(*str == '-'); str++;
+    while (*str && *str != '-') str++;
+    assert(*str == '-'); str++;
+
+    /* Convert minus signs and spaces in the remaining string into
+     * underscores. */
+    while (*str) {
+        if (*str == '-' || *str == ' ')
+            *str = '_';
+        str++;
+    }
 }
 
-static int do_ssh_init(unsigned char c)
+static int do_ssh_init(Ssh ssh, unsigned char c)
 {
-    static int vslen;
-    static char version[10];
-    static char *vstring;
-    static int vstrsize;
-    static char *vlog;
-    static int i;
-    static int proto1, proto2;
+    struct do_ssh_init_state {
+       int vslen;
+       char version[10];
+       char *vstring;
+       int vstrsize;
+       int i;
+       int proto1, proto2;
+    };
+    crState(do_ssh_init_state);
 
-    crBegin;
+    crBegin(ssh->do_ssh_init_crstate);
 
     /* Search for the string "SSH-" in the input. */
-    i = 0;
+    s->i = 0;
     while (1) {
        static const int transS[] = { 1, 2, 2, 1 };
        static const int transH[] = { 0, 0, 3, 0 };
        static const int transminus[] = { 0, 0, 0, -1 };
        if (c == 'S')
-           i = transS[i];
+           s->i = transS[s->i];
        else if (c == 'H')
-           i = transH[i];
+           s->i = transH[s->i];
        else if (c == '-')
-           i = transminus[i];
+           s->i = transminus[s->i];
        else
-           i = 0;
-       if (i < 0)
+           s->i = 0;
+       if (s->i < 0)
            break;
        crReturn(1);                   /* get another character */
     }
 
-    vstrsize = 16;
-    vstring = smalloc(vstrsize);
-    strcpy(vstring, "SSH-");
-    vslen = 4;
-    i = 0;
+    s->vstrsize = 16;
+    s->vstring = snewn(s->vstrsize, char);
+    strcpy(s->vstring, "SSH-");
+    s->vslen = 4;
+    s->i = 0;
     while (1) {
        crReturn(1);                   /* get another char */
-       if (vslen >= vstrsize - 1) {
-           vstrsize += 16;
-           vstring = srealloc(vstring, vstrsize);
+       if (s->vslen >= s->vstrsize - 1) {
+           s->vstrsize += 16;
+           s->vstring = sresize(s->vstring, s->vstrsize, char);
        }
-       vstring[vslen++] = c;
-       if (i >= 0) {
+       s->vstring[s->vslen++] = c;
+       if (s->i >= 0) {
            if (c == '-') {
-               version[i] = '\0';
-               i = -1;
-           } else if (i < sizeof(version) - 1)
-               version[i++] = c;
-       } else if (c == '\n')
+               s->version[s->i] = '\0';
+               s->i = -1;
+           } else if (s->i < sizeof(s->version) - 1)
+               s->version[s->i++] = c;
+       } else if (c == '\012')
            break;
     }
 
-    ssh_agentfwd_enabled = FALSE;
-    rdpkt2_state.incoming_sequence = 0;
+    ssh->agentfwd_enabled = FALSE;
+    ssh->rdpkt2_state.incoming_sequence = 0;
 
-    vstring[vslen] = 0;
-    vlog = smalloc(20 + vslen);
-    vstring[strcspn (vstring, "\r\n")] = '\0'; /* remove end-of-line chars */
-    sprintf(vlog, "Server version: %s", vstring);
-    logevent(vlog);
-    ssh_detect_bugs(vstring);
-    sfree(vlog);
+    s->vstring[s->vslen] = 0;
+    s->vstring[strcspn(s->vstring, "\015\012")] = '\0';/* remove EOL chars */
+    {
+       char *vlog;
+       vlog = snewn(20 + s->vslen, char);
+       sprintf(vlog, "Server version: %s", s->vstring);
+       logevent(vlog);
+       sfree(vlog);
+    }
+    ssh_detect_bugs(ssh, s->vstring);
 
     /*
      * Decide which SSH protocol version to support.
      */
 
     /* Anything strictly below "2.0" means protocol 1 is supported. */
-    proto1 = ssh_versioncmp(version, "2.0") < 0;
+    s->proto1 = ssh_versioncmp(s->version, "2.0") < 0;
     /* Anything greater or equal to "1.99" means protocol 2 is supported. */
-    proto2 = ssh_versioncmp(version, "1.99") >= 0;
+    s->proto2 = ssh_versioncmp(s->version, "1.99") >= 0;
 
-    if (cfg.sshprot == 0 && !proto1) {
+    if (ssh->cfg.sshprot == 0 && !s->proto1) {
        bombout(("SSH protocol version 1 required by user but not provided by server"));
-       crReturn(0);
+       crStop(0);
     }
-    if (cfg.sshprot == 3 && !proto2) {
+    if (ssh->cfg.sshprot == 3 && !s->proto2) {
        bombout(("SSH protocol version 2 required by user but not provided by server"));
-       crReturn(0);
+       crStop(0);
     }
 
-    if (proto2 && (cfg.sshprot >= 2 || !proto1)) {
-       /*
-        * Use v2 protocol.
-        */
-       char verstring[80], vlog[100];
-       sprintf(verstring, "SSH-2.0-%s", sshver);
-       SHA_Init(&exhashbase);
-       /*
-        * Hash our version string and their version string.
-        */
-       sha_string(&exhashbase, verstring, strlen(verstring));
-       sha_string(&exhashbase, vstring, strcspn(vstring, "\r\n"));
-       sprintf(vlog, "We claim version: %s", verstring);
-       logevent(vlog);
-       strcat(verstring, "\n");
-       logevent("Using SSH protocol version 2");
-       sk_write(s, verstring, strlen(verstring));
-       ssh_protocol = ssh2_protocol;
-       ssh_version = 2;
-       s_rdpkt = ssh2_rdpkt;
-    } else {
-       /*
-        * Use v1 protocol.
-        */
-       char verstring[80], vlog[100];
-       sprintf(verstring, "SSH-%s-%s",
-               (ssh_versioncmp(version, "1.5") <= 0 ? version : "1.5"),
-               sshver);
-       sprintf(vlog, "We claim version: %s", verstring);
-       logevent(vlog);
-       strcat(verstring, "\n");
+    {
+        char *verstring;
+
+        if (s->proto2 && (ssh->cfg.sshprot >= 2 || !s->proto1)) {
+            /*
+             * Construct a v2 version string.
+             */
+            verstring = dupprintf("SSH-2.0-%s\015\012", sshver);
+            ssh->version = 2;
+        } else {
+            /*
+             * Construct a v1 version string.
+             */
+            verstring = dupprintf("SSH-%s-%s\012",
+                                  (ssh_versioncmp(s->version, "1.5") <= 0 ?
+                                   s->version : "1.5"),
+                                  sshver);
+            ssh->version = 1;
+        }
 
-       logevent("Using SSH protocol version 1");
-       sk_write(s, verstring, strlen(verstring));
-       ssh_protocol = ssh1_protocol;
-       ssh_version = 1;
-       s_rdpkt = ssh1_rdpkt;
+        ssh_fix_verstring(verstring);
+
+        if (ssh->version == 2) {
+            /*
+             * Hash our version string and their version string.
+             */
+            SHA_Init(&ssh->exhashbase);
+            sha_string(&ssh->exhashbase, verstring,
+                       strcspn(verstring, "\015\012"));
+            sha_string(&ssh->exhashbase, s->vstring,
+                       strcspn(s->vstring, "\015\012"));
+
+            /*
+             * Initialise SSHv2 protocol.
+             */
+            ssh->protocol = ssh2_protocol;
+            ssh2_protocol_setup(ssh);
+            ssh->s_rdpkt = ssh2_rdpkt;
+        } else {
+            /*
+             * Initialise SSHv1 protocol.
+             */
+            ssh->protocol = ssh1_protocol;
+            ssh1_protocol_setup(ssh);
+            ssh->s_rdpkt = ssh1_rdpkt;
+        }
+        logeventf(ssh, "We claim version: %.*s",
+                  strcspn(verstring, "\015\012"), verstring);
+       sk_write(ssh->s, verstring, strlen(verstring));
+        sfree(verstring);
     }
-    ssh_state = SSH_STATE_BEFORE_SIZE;
 
-    sfree(vstring);
+    logeventf(ssh, "Using SSH protocol version %d", ssh->version);
+
+    update_specials_menu(ssh->frontend);
+    ssh->state = SSH_STATE_BEFORE_SIZE;
+    ssh->pinger = pinger_new(&ssh->cfg, &ssh_backend, ssh);
+
+    sfree(s->vstring);
 
     crFinish(0);
 }
 
-static void ssh_gotdata(unsigned char *data, int datalen)
+static void ssh_gotdata(Ssh ssh, unsigned char *data, int datalen)
 {
-    crBegin;
+    crBegin(ssh->ssh_gotdata_crstate);
 
     /*
      * To begin with, feed the characters one by one to the
@@ -1840,10 +2337,10 @@ static void ssh_gotdata(unsigned char *data, int datalen)
      * exchange and can move on to packet discipline.
      */
     while (1) {
-       int ret;
+       int ret;                       /* need not be kept across crReturn */
        if (datalen == 0)
            crReturnV;                 /* more data please */
-       ret = do_ssh_init(*data);
+       ret = do_ssh_init(ssh, *data);
        data++;
        datalen--;
        if (ret == 0)
@@ -1860,47 +2357,101 @@ static void ssh_gotdata(unsigned char *data, int datalen)
        crReturnV;
     while (1) {
        while (datalen > 0) {
-           if (s_rdpkt(&data, &datalen) == 0) {
-               if (ssh_state == SSH_STATE_CLOSED) {
-                   return;
-               }
-               ssh_protocol(NULL, 0, 1);
-               if (ssh_state == SSH_STATE_CLOSED) {
-                   return;
-               }
+           struct Packet *pktin = ssh->s_rdpkt(ssh, &data, &datalen);
+           if (pktin) {
+               ssh->protocol(ssh, NULL, 0, pktin);
+               ssh_free_packet(pktin);
            }
+           if (ssh->state == SSH_STATE_CLOSED)
+               return;
        }
        crReturnV;
     }
     crFinishV;
 }
 
-static int ssh_closing(Plug plug, char *error_msg, int error_code,
+static int ssh_do_close(Ssh ssh, int notify_exit)
+{
+    int i, ret = 0;
+    struct ssh_channel *c;
+
+    ssh->state = SSH_STATE_CLOSED;
+    if (ssh->s) {
+        sk_close(ssh->s);
+        ssh->s = NULL;
+        if (notify_exit)
+            notify_remote_exit(ssh->frontend);
+        else
+            ret = 1;
+    }
+    /*
+     * Now we must shut down any port and X forwardings going
+     * through this connection.
+     */
+    if (ssh->channels) {
+       for (i = 0; NULL != (c = index234(ssh->channels, i)); i++) {
+           switch (c->type) {
+             case CHAN_X11:
+               x11_close(c->u.x11.s);
+               break;
+             case CHAN_SOCKDATA:
+               pfd_close(c->u.pfd.s);
+               break;
+           }
+           del234(ssh->channels, c);
+           if (ssh->version == 2)
+               bufchain_clear(&c->v.v2.outbuffer);
+           sfree(c);
+       }
+    }
+
+    return ret;
+}
+
+static void ssh_log(Plug plug, int type, SockAddr addr, int port,
+                   const char *error_msg, int error_code)
+{
+    Ssh ssh = (Ssh) plug;
+    char addrbuf[256], *msg;
+
+    sk_getaddr(addr, addrbuf, lenof(addrbuf));
+
+    if (type == 0)
+       msg = dupprintf("Connecting to %s port %d", addrbuf, port);
+    else
+       msg = dupprintf("Failed to connect to %s: %s", addrbuf, error_msg);
+
+    logevent(msg);
+}
+
+static int ssh_closing(Plug plug, const char *error_msg, int error_code,
                       int calling_back)
 {
-    ssh_state = SSH_STATE_CLOSED;
-    if (s) {
-        sk_close(s);
-        s = NULL;
+    Ssh ssh = (Ssh) plug;
+    int need_notify = ssh_do_close(ssh, FALSE);
+
+    if (!error_msg && !ssh->close_expected) {
+        error_msg = "Server unexpectedly closed network connection";
     }
+
     if (error_msg) {
        /* A socket error has occurred. */
        logevent(error_msg);
-       connection_fatal(error_msg);
+       connection_fatal(ssh->frontend, "%s", error_msg);
     } else {
-       /* Otherwise, the remote side closed the connection normally. */
+        logevent("Server closed network connection");
     }
+    if (need_notify)
+        notify_remote_exit(ssh->frontend);
     return 0;
 }
 
 static int ssh_receive(Plug plug, int urgent, char *data, int len)
 {
-    ssh_gotdata(data, len);
-    if (ssh_state == SSH_STATE_CLOSED) {
-       if (s) {
-           sk_close(s);
-           s = NULL;
-       }
+    Ssh ssh = (Ssh) plug;
+    ssh_gotdata(ssh, (unsigned char *)data, len);
+    if (ssh->state == SSH_STATE_CLOSED) {
+       ssh_do_close(ssh, TRUE);
        return 0;
     }
     return 1;
@@ -1908,12 +2459,13 @@ static int ssh_receive(Plug plug, int urgent, char *data, int len)
 
 static void ssh_sent(Plug plug, int bufsize)
 {
+    Ssh ssh = (Ssh) plug;
     /*
      * If the send backlog on the SSH socket itself clears, we
      * should unthrottle the whole world if it was throttled.
      */
     if (bufsize < SSH_MAX_BACKLOG)
-       ssh_throttle_all(0, bufsize);
+       ssh_throttle_all(ssh, 0, bufsize);
 }
 
 /*
@@ -1922,94 +2474,69 @@ static void ssh_sent(Plug plug, int bufsize)
  * Also places the canonical host name into `realhost'. It must be
  * freed by the caller.
  */
-static char *connect_to_host(char *host, int port, char **realhost, int nodelay)
+static const char *connect_to_host(Ssh ssh, char *host, int port,
+                                  char **realhost, int nodelay, int keepalive)
 {
-    static struct plug_function_table fn_table = {
+    static const struct plug_function_table fn_table = {
+       ssh_log,
        ssh_closing,
        ssh_receive,
        ssh_sent,
        NULL
-    }, *fn_table_ptr = &fn_table;
+    };
 
     SockAddr addr;
-    char *err;
-#ifdef FWHACK
-    char *FWhost;
-    int FWport;
-#endif
+    const char *err;
 
-    savedhost = smalloc(1 + strlen(host));
-    if (!savedhost)
+    ssh->savedhost = snewn(1 + strlen(host), char);
+    if (!ssh->savedhost)
        fatalbox("Out of memory");
-    strcpy(savedhost, host);
+    strcpy(ssh->savedhost, host);
 
     if (port < 0)
        port = 22;                     /* default ssh port */
-    savedport = port;
-
-#ifdef FWHACK
-    FWhost = host;
-    FWport = port;
-    host = FWSTR;
-    port = 23;
-#endif
+    ssh->savedport = port;
 
     /*
      * Try to find host.
      */
-    {
-       char buf[200];
-       sprintf(buf, "Looking up host \"%.170s\"", host);
-       logevent(buf);
-    }
-    addr = sk_namelookup(host, realhost);
-    if ((err = sk_addr_error(addr)))
+    logeventf(ssh, "Looking up host \"%s\"%s", host,
+             (ssh->cfg.addressfamily == ADDRTYPE_IPV4 ? " (IPv4)" :
+              (ssh->cfg.addressfamily == ADDRTYPE_IPV6 ? " (IPv6)" : "")));
+    addr = name_lookup(host, port, realhost, &ssh->cfg,
+                      ssh->cfg.addressfamily);
+    if ((err = sk_addr_error(addr)) != NULL) {
+       sk_addr_free(addr);
        return err;
-
-#ifdef FWHACK
-    *realhost = strdup(FWhost);
-#endif
+    }
 
     /*
      * Open socket.
      */
-    {
-       char buf[200], addrbuf[100];
-       sk_getaddr(addr, addrbuf, 100);
-       sprintf(buf, "Connecting to %.100s port %d", addrbuf, port);
-       logevent(buf);
-    }
-    s = new_connection(addr, *realhost, port, 0, 1, nodelay, &fn_table_ptr);
-    if ((err = sk_socket_error(s))) {
-       s = NULL;
+    ssh->fn = &fn_table;
+    ssh->s = new_connection(addr, *realhost, port,
+                           0, 1, nodelay, keepalive, (Plug) ssh, &ssh->cfg);
+    if ((err = sk_socket_error(ssh->s)) != NULL) {
+       ssh->s = NULL;
+       notify_remote_exit(ssh->frontend);
        return err;
     }
 
-#ifdef FWHACK
-    sk_write(s, "connect ", 8);
-    sk_write(s, FWhost, strlen(FWhost));
-    {
-       char buf[20];
-       sprintf(buf, " %d\n", FWport);
-       sk_write(s, buf, strlen(buf));
-    }
-#endif
-
     return NULL;
 }
 
 /*
  * Throttle or unthrottle the SSH connection.
  */
-static void ssh1_throttle(int adjust)
+static void ssh1_throttle(Ssh ssh, int adjust)
 {
-    int old_count = ssh1_throttle_count;
-    ssh1_throttle_count += adjust;
-    assert(ssh1_throttle_count >= 0);
-    if (ssh1_throttle_count && !old_count) {
-       sk_set_frozen(s, 1);
-    } else if (!ssh1_throttle_count && old_count) {
-       sk_set_frozen(s, 0);
+    int old_count = ssh->v1_throttle_count;
+    ssh->v1_throttle_count += adjust;
+    assert(ssh->v1_throttle_count >= 0);
+    if (ssh->v1_throttle_count && !old_count) {
+       sk_set_frozen(ssh->s, 1);
+    } else if (!ssh->v1_throttle_count && old_count) {
+       sk_set_frozen(ssh->s, 0);
     }
 }
 
@@ -2017,18 +2544,18 @@ static void ssh1_throttle(int adjust)
  * Throttle or unthrottle _all_ local data streams (for when sends
  * on the SSH connection itself back up).
  */
-static void ssh_throttle_all(int enable, int bufsize)
+static void ssh_throttle_all(Ssh ssh, int enable, int bufsize)
 {
     int i;
     struct ssh_channel *c;
 
-    if (enable == ssh_throttled_all)
+    if (enable == ssh->throttled_all)
        return;
-    ssh_throttled_all = enable;
-    ssh_overall_bufsize = bufsize;
-    if (!ssh_channels)
+    ssh->throttled_all = enable;
+    ssh->overall_bufsize = bufsize;
+    if (!ssh->channels)
        return;
-    for (i = 0; NULL != (c = index234(ssh_channels, i)); i++) {
+    for (i = 0; NULL != (c = index234(ssh->channels, i)); i++) {
        switch (c->type) {
          case CHAN_MAINSESSION:
            /*
@@ -2042,28 +2569,24 @@ static void ssh_throttle_all(int enable, int bufsize)
            /* Agent channels require no buffer management. */
            break;
          case CHAN_SOCKDATA:
-           pfd_override_throttle(c->u.x11.s, enable);
+           pfd_override_throttle(c->u.pfd.s, enable);
            break;
        }
     }
 }
 
 /*
- * Username and password input, abstracted off into reusable
- * routines (hopefully even reusable between SSH1 and SSH2!).
+ * Username and password input, abstracted off into routines
+ * reusable in several places - even between SSH1 and SSH2.
  */
-static char *ssh_userpass_input_buffer;
-static int ssh_userpass_input_buflen;
-static int ssh_userpass_input_bufpos;
-static int ssh_userpass_input_echo;
 
 /* Set up a username or password input loop on a given buffer. */
-void setup_userpass_input(char *buffer, int buflen, int echo)
+static void setup_userpass_input(Ssh ssh, char *buffer, int buflen, int echo)
 {
-    ssh_userpass_input_buffer = buffer;
-    ssh_userpass_input_buflen = buflen;
-    ssh_userpass_input_bufpos = 0;
-    ssh_userpass_input_echo = echo;
+    ssh->userpass_input_buffer = buffer;
+    ssh->userpass_input_buflen = buflen;
+    ssh->userpass_input_bufpos = 0;
+    ssh->userpass_input_echo = echo;
 }
 
 /*
@@ -2072,7 +2595,7 @@ void setup_userpass_input(char *buffer, int buflen, int echo)
  * buffer), <0 for failure (user hit ^C/^D, bomb out and exit), 0
  * for inconclusive (keep waiting for more input please).
  */
-int process_userpass_input(unsigned char *in, int inlen)
+static int process_userpass_input(Ssh ssh, unsigned char *in, int inlen)
 {
     char c;
 
@@ -2080,24 +2603,24 @@ int process_userpass_input(unsigned char *in, int inlen)
        switch (c = *in++) {
          case 10:
          case 13:
-           ssh_userpass_input_buffer[ssh_userpass_input_bufpos] = 0;
-           ssh_userpass_input_buffer[ssh_userpass_input_buflen-1] = 0;
+           ssh->userpass_input_buffer[ssh->userpass_input_bufpos] = 0;
+           ssh->userpass_input_buffer[ssh->userpass_input_buflen-1] = 0;
            return +1;
            break;
          case 8:
          case 127:
-           if (ssh_userpass_input_bufpos > 0) {
-               if (ssh_userpass_input_echo)
-                   c_write_str("\b \b");
-               ssh_userpass_input_bufpos--;
+           if (ssh->userpass_input_bufpos > 0) {
+               if (ssh->userpass_input_echo)
+                   c_write_str(ssh, "\b \b");
+               ssh->userpass_input_bufpos--;
            }
            break;
          case 21:
          case 27:
-           while (ssh_userpass_input_bufpos > 0) {
-               if (ssh_userpass_input_echo)
-                   c_write_str("\b \b");
-               ssh_userpass_input_bufpos--;
+           while (ssh->userpass_input_bufpos > 0) {
+               if (ssh->userpass_input_echo)
+                   c_write_str(ssh, "\b \b");
+               ssh->userpass_input_bufpos--;
            }
            break;
          case 3:
@@ -2105,12 +2628,18 @@ int process_userpass_input(unsigned char *in, int inlen)
            return -1;
            break;
          default:
-           if (((c >= ' ' && c <= '~') ||
+           /*
+            * This simplistic check for printability is disabled
+            * when we're doing password input, because some people
+            * have control characters in their passwords.o
+            */
+           if ((!ssh->userpass_input_echo ||
+                (c >= ' ' && c <= '~') ||
                 ((unsigned char) c >= 160))
-               && ssh_userpass_input_bufpos < ssh_userpass_input_buflen-1) {
-               ssh_userpass_input_buffer[ssh_userpass_input_bufpos++] = c;
-               if (ssh_userpass_input_echo)
-                   c_write(&c, 1);
+               && ssh->userpass_input_bufpos < ssh->userpass_input_buflen-1) {
+               ssh->userpass_input_buffer[ssh->userpass_input_bufpos++] = c;
+               if (ssh->userpass_input_echo)
+                   c_write(ssh, &c, 1);
            }
            break;
        }
@@ -2118,42 +2647,107 @@ int process_userpass_input(unsigned char *in, int inlen)
     return 0;
 }
 
+static void ssh_agent_callback(void *sshv, void *reply, int replylen)
+{
+    Ssh ssh = (Ssh) sshv;
+
+    ssh->agent_response = reply;
+    ssh->agent_response_len = replylen;
+
+    if (ssh->version == 1)
+       do_ssh1_login(ssh, NULL, -1, NULL);
+    else
+       do_ssh2_authconn(ssh, NULL, -1, NULL);
+}
+
+static void ssh_agentf_callback(void *cv, void *reply, int replylen)
+{
+    struct ssh_channel *c = (struct ssh_channel *)cv;
+    Ssh ssh = c->ssh;
+    void *sentreply = reply;
+
+    if (!sentreply) {
+       /* Fake SSH_AGENT_FAILURE. */
+       sentreply = "\0\0\0\1\5";
+       replylen = 5;
+    }
+    if (ssh->version == 2) {
+       ssh2_add_channel_data(c, sentreply, replylen);
+       ssh2_try_send(c);
+    } else {
+       send_packet(ssh, SSH1_MSG_CHANNEL_DATA,
+                   PKT_INT, c->remoteid,
+                   PKTT_DATA,
+                   PKT_INT, replylen,
+                   PKT_DATA, sentreply, replylen,
+                   PKTT_OTHER,
+                   PKT_END);
+    }
+    if (reply)
+       sfree(reply);
+}
+
 /*
  * Handle the key exchange and user authentication phases.
  */
-static int do_ssh1_login(unsigned char *in, int inlen, int ispkt)
+static int do_ssh1_login(Ssh ssh, unsigned char *in, int inlen,
+                        struct Packet *pktin)
 {
-    int i, j;
-    static int len;
-    static unsigned char *rsabuf, *keystr1, *keystr2;
-    unsigned char cookie[8];
+    int i, j, ret;
+    unsigned char cookie[8], *ptr;
     struct RSAKey servkey, hostkey;
     struct MD5Context md5c;
-    static unsigned long supported_ciphers_mask, supported_auths_mask;
-    static int tried_publickey, tried_agent;
-    static int tis_auth_refused, ccard_auth_refused;
-    static unsigned char session_id[16];
-    static int cipher_type;
-    static char username[100];
-    static void *publickey_blob;
-    int publickey_bloblen;
-
-    crBegin;
-
-    if (!ispkt)
-       crWaitUntil(ispkt);
-
-    if (pktin.type != SSH1_SMSG_PUBLIC_KEY) {
+    struct do_ssh1_login_state {
+       int len;
+       unsigned char *rsabuf, *keystr1, *keystr2;
+       unsigned long supported_ciphers_mask, supported_auths_mask;
+       int tried_publickey, tried_agent;
+       int tis_auth_refused, ccard_auth_refused;
+       unsigned char session_id[16];
+       int cipher_type;
+       char username[100];
+       void *publickey_blob;
+       int publickey_bloblen;
+       char password[100];
+       char prompt[200];
+       int pos;
+       char c;
+       int pwpkt_type;
+       unsigned char request[5], *response, *p;
+       int responselen;
+       int keyi, nkeys;
+       int authed;
+       struct RSAKey key;
+       Bignum challenge;
+       char *commentp;
+       int commentlen;
+    };
+    crState(do_ssh1_login_state);
+
+    crBegin(ssh->do_ssh1_login_crstate);
+
+    if (!pktin)
+       crWaitUntil(pktin);
+
+    if (pktin->type != SSH1_SMSG_PUBLIC_KEY) {
        bombout(("Public key packet not received"));
-       crReturn(0);
+       crStop(0);
     }
 
     logevent("Received public keys");
 
-    memcpy(cookie, pktin.body, 8);
+    ptr = ssh_pkt_getdata(pktin, 8);
+    if (!ptr) {
+       bombout(("SSH1 public key packet stopped before random cookie"));
+       crStop(0);
+    }
+    memcpy(cookie, ptr, 8);
 
-    i = makekey(pktin.body + 8, &servkey, &keystr1, 0);
-    j = makekey(pktin.body + 8 + i, &hostkey, &keystr2, 0);
+    if (!ssh1_pkt_getrsakey(pktin, &servkey, &s->keystr1) ||
+       !ssh1_pkt_getrsakey(pktin, &hostkey, &s->keystr2)) {    
+       bombout(("Failed to read SSH1 public keys from public key packet"));
+       crStop(0);
+    }
 
     /*
      * Log the host key fingerprint.
@@ -2168,27 +2762,36 @@ static int do_ssh1_login(unsigned char *in, int inlen, int ispkt)
        logevent(logmsg);
     }
 
-    ssh1_remote_protoflags = GET_32BIT(pktin.body + 8 + i + j);
-    supported_ciphers_mask = GET_32BIT(pktin.body + 12 + i + j);
-    supported_auths_mask = GET_32BIT(pktin.body + 16 + i + j);
+    ssh->v1_remote_protoflags = ssh_pkt_getuint32(pktin);
+    s->supported_ciphers_mask = ssh_pkt_getuint32(pktin);
+    s->supported_auths_mask = ssh_pkt_getuint32(pktin);
 
-    ssh1_local_protoflags =
-       ssh1_remote_protoflags & SSH1_PROTOFLAGS_SUPPORTED;
-    ssh1_local_protoflags |= SSH1_PROTOFLAG_SCREEN_NUMBER;
+    ssh->v1_local_protoflags =
+       ssh->v1_remote_protoflags & SSH1_PROTOFLAGS_SUPPORTED;
+    ssh->v1_local_protoflags |= SSH1_PROTOFLAG_SCREEN_NUMBER;
 
     MD5Init(&md5c);
-    MD5Update(&md5c, keystr2, hostkey.bytes);
-    MD5Update(&md5c, keystr1, servkey.bytes);
-    MD5Update(&md5c, pktin.body, 8);
-    MD5Final(session_id, &md5c);
+    MD5Update(&md5c, s->keystr2, hostkey.bytes);
+    MD5Update(&md5c, s->keystr1, servkey.bytes);
+    MD5Update(&md5c, cookie, 8);
+    MD5Final(s->session_id, &md5c);
 
     for (i = 0; i < 32; i++)
-       session_key[i] = random_byte();
+       ssh->session_key[i] = random_byte();
 
-    len = (hostkey.bytes > servkey.bytes ? hostkey.bytes : servkey.bytes);
+    /*
+     * Verify that the `bits' and `bytes' parameters match.
+     */
+    if (hostkey.bits > hostkey.bytes * 8 ||
+       servkey.bits > servkey.bytes * 8) {
+       bombout(("SSH1 public keys were badly formatted"));
+       crStop(0);
+    }
+
+    s->len = (hostkey.bytes > servkey.bytes ? hostkey.bytes : servkey.bytes);
 
-    rsabuf = smalloc(len);
-    if (!rsabuf)
+    s->rsabuf = snewn(s->len, unsigned char);
+    if (!s->rsabuf)
        fatalbox("Out of memory");
 
     /*
@@ -2200,28 +2803,35 @@ static int do_ssh1_login(unsigned char *in, int inlen, int ispkt)
         */
        int len = rsastr_len(&hostkey);
        char fingerprint[100];
-       char *keystr = smalloc(len);
+       char *keystr = snewn(len, char);
        if (!keystr)
            fatalbox("Out of memory");
        rsastr_fmt(keystr, &hostkey);
        rsa_fingerprint(fingerprint, sizeof(fingerprint), &hostkey);
-       verify_ssh_host_key(savedhost, savedport, "rsa", keystr,
+       verify_ssh_host_key(ssh->frontend,
+                           ssh->savedhost, ssh->savedport, "rsa", keystr,
                            fingerprint);
        sfree(keystr);
     }
 
     for (i = 0; i < 32; i++) {
-       rsabuf[i] = session_key[i];
+       s->rsabuf[i] = ssh->session_key[i];
        if (i < 16)
-           rsabuf[i] ^= session_id[i];
+           s->rsabuf[i] ^= s->session_id[i];
     }
 
     if (hostkey.bytes > servkey.bytes) {
-       rsaencrypt(rsabuf, 32, &servkey);
-       rsaencrypt(rsabuf, servkey.bytes, &hostkey);
+       ret = rsaencrypt(s->rsabuf, 32, &servkey);
+       if (ret)
+           ret = rsaencrypt(s->rsabuf, servkey.bytes, &hostkey);
     } else {
-       rsaencrypt(rsabuf, 32, &hostkey);
-       rsaencrypt(rsabuf, hostkey.bytes, &servkey);
+       ret = rsaencrypt(s->rsabuf, 32, &hostkey);
+       if (ret)
+           ret = rsaencrypt(s->rsabuf, hostkey.bytes, &servkey);
+    }
+    if (!ret) {
+       bombout(("SSH1 public key encryptions failed due to bad formatting"));
+       crStop(0);      
     }
 
     logevent("Encrypted session key");
@@ -2229,8 +2839,9 @@ static int do_ssh1_login(unsigned char *in, int inlen, int ispkt)
     {
        int cipher_chosen = 0, warn = 0;
        char *cipher_string = NULL;
+       int i;
        for (i = 0; !cipher_chosen && i < CIPHER_MAX; i++) {
-           int next_cipher = cfg.ssh_cipherlist[i];
+           int next_cipher = ssh->cfg.ssh_cipherlist[i];
            if (next_cipher == CIPHER_WARN) {
                /* If/when we choose a cipher, warn about it */
                warn = 1;
@@ -2239,33 +2850,36 @@ static int do_ssh1_login(unsigned char *in, int inlen, int ispkt)
                logevent("AES not supported in SSH1, skipping");
            } else {
                switch (next_cipher) {
-                 case CIPHER_3DES:     cipher_type = SSH_CIPHER_3DES;
+                 case CIPHER_3DES:     s->cipher_type = SSH_CIPHER_3DES;
                                        cipher_string = "3DES"; break;
-                 case CIPHER_BLOWFISH: cipher_type = SSH_CIPHER_BLOWFISH;
+                 case CIPHER_BLOWFISH: s->cipher_type = SSH_CIPHER_BLOWFISH;
                                        cipher_string = "Blowfish"; break;
-                 case CIPHER_DES:      cipher_type = SSH_CIPHER_DES;
+                 case CIPHER_DES:      s->cipher_type = SSH_CIPHER_DES;
                                        cipher_string = "single-DES"; break;
                }
-               if (supported_ciphers_mask & (1 << cipher_type))
+               if (s->supported_ciphers_mask & (1 << s->cipher_type))
                    cipher_chosen = 1;
            }
        }
        if (!cipher_chosen) {
-           if ((supported_ciphers_mask & (1 << SSH_CIPHER_3DES)) == 0)
+           if ((s->supported_ciphers_mask & (1 << SSH_CIPHER_3DES)) == 0)
                bombout(("Server violates SSH 1 protocol by not "
                         "supporting 3DES encryption"));
            else
                /* shouldn't happen */
                bombout(("No supported ciphers found"));
-           crReturn(0);
+           crStop(0);
        }
 
        /* Warn about chosen cipher if necessary. */
-       if (warn)
-           askcipher(cipher_string, 0);
+       if (warn) {
+            sk_set_frozen(ssh->s, 1);
+           askalg(ssh->frontend, "cipher", cipher_string);
+            sk_set_frozen(ssh->s, 0);
+        }
     }
 
-    switch (cipher_type) {
+    switch (s->cipher_type) {
       case SSH_CIPHER_3DES:
        logevent("Using 3DES encryption");
        break;
@@ -2277,203 +2891,271 @@ static int do_ssh1_login(unsigned char *in, int inlen, int ispkt)
        break;
     }
 
-    send_packet(SSH1_CMSG_SESSION_KEY,
-               PKT_CHAR, cipher_type,
+    send_packet(ssh, SSH1_CMSG_SESSION_KEY,
+               PKT_CHAR, s->cipher_type,
                PKT_DATA, cookie, 8,
-               PKT_CHAR, (len * 8) >> 8, PKT_CHAR, (len * 8) & 0xFF,
-               PKT_DATA, rsabuf, len,
-               PKT_INT, ssh1_local_protoflags, PKT_END);
+               PKT_CHAR, (s->len * 8) >> 8, PKT_CHAR, (s->len * 8) & 0xFF,
+               PKT_DATA, s->rsabuf, s->len,
+               PKT_INT, ssh->v1_local_protoflags, PKT_END);
 
     logevent("Trying to enable encryption...");
 
-    sfree(rsabuf);
+    sfree(s->rsabuf);
+
+    ssh->cipher = (s->cipher_type == SSH_CIPHER_BLOWFISH ? &ssh_blowfish_ssh1 :
+                  s->cipher_type == SSH_CIPHER_DES ? &ssh_des :
+                  &ssh_3des);
+    ssh->v1_cipher_ctx = ssh->cipher->make_context();
+    ssh->cipher->sesskey(ssh->v1_cipher_ctx, ssh->session_key);
+    logeventf(ssh, "Initialised %s encryption", ssh->cipher->text_name);
 
-    cipher = cipher_type == SSH_CIPHER_BLOWFISH ? &ssh_blowfish_ssh1 :
-       cipher_type == SSH_CIPHER_DES ? &ssh_des : &ssh_3des;
-    cipher->sesskey(session_key);
+    ssh->crcda_ctx = crcda_make_context();
+    logevent("Installing CRC compensation attack detector");
 
-    crWaitUntil(ispkt);
+    if (servkey.modulus) {
+       sfree(servkey.modulus);
+       servkey.modulus = NULL;
+    }
+    if (servkey.exponent) {
+       sfree(servkey.exponent);
+       servkey.exponent = NULL;
+    }
+    if (hostkey.modulus) {
+       sfree(hostkey.modulus);
+       hostkey.modulus = NULL;
+    }
+    if (hostkey.exponent) {
+       sfree(hostkey.exponent);
+       hostkey.exponent = NULL;
+    }
+    crWaitUntil(pktin);
 
-    if (pktin.type != SSH1_SMSG_SUCCESS) {
+    if (pktin->type != SSH1_SMSG_SUCCESS) {
        bombout(("Encryption not successfully enabled"));
-       crReturn(0);
+       crStop(0);
     }
 
     logevent("Successfully started encryption");
 
     fflush(stdout);
     {
-       if ((flags & FLAG_INTERACTIVE) && !*cfg.username) {
+       if (!*ssh->cfg.username) {
            if (ssh_get_line && !ssh_getline_pw_only) {
                if (!ssh_get_line("login as: ",
-                                 username, sizeof(username), FALSE)) {
+                                 s->username, sizeof(s->username), FALSE)) {
                    /*
                     * get_line failed to get a username.
                     * Terminate.
                     */
                    logevent("No username provided. Abandoning session.");
-                   ssh_state = SSH_STATE_CLOSED;
-                   crReturn(1);
+                   ssh->close_expected = TRUE;
+                    ssh_closing((Plug)ssh, NULL, 0, 0);
+                   crStop(1);
                }
            } else {
-               static int ret;
-               c_write_str("login as: ");
-               ssh_send_ok = 1;
+               int ret;               /* need not be kept over crReturn */
+               c_write_str(ssh, "login as: ");
+               ssh->send_ok = 1;
 
-               setup_userpass_input(username, sizeof(username), 1);
+               setup_userpass_input(ssh, s->username, sizeof(s->username), 1);
                do {
-                   crWaitUntil(!ispkt);
-                   ret = process_userpass_input(in, inlen);
+                   crWaitUntil(!pktin);
+                   ret = process_userpass_input(ssh, in, inlen);
                } while (ret == 0);
                if (ret < 0)
                    cleanup_exit(0);
-               c_write_str("\r\n");
+               c_write_str(ssh, "\r\n");
            }
        } else {
-           strncpy(username, cfg.username, 99);
-           username[99] = '\0';
+           strncpy(s->username, ssh->cfg.username, sizeof(s->username));
+           s->username[sizeof(s->username)-1] = '\0';
        }
 
-       send_packet(SSH1_CMSG_USER, PKT_STR, username, PKT_END);
+       send_packet(ssh, SSH1_CMSG_USER, PKT_STR, s->username, PKT_END);
        {
-           char userlog[22 + sizeof(username)];
-           sprintf(userlog, "Sent username \"%s\"", username);
+           char userlog[22 + sizeof(s->username)];
+           sprintf(userlog, "Sent username \"%s\"", s->username);
            logevent(userlog);
            if (flags & FLAG_INTERACTIVE &&
                (!((flags & FLAG_STDERR) && (flags & FLAG_VERBOSE)))) {
                strcat(userlog, "\r\n");
-               c_write_str(userlog);
+               c_write_str(ssh, userlog);
            }
        }
     }
 
-    crWaitUntil(ispkt);
+    crWaitUntil(pktin);
 
-    if ((ssh_remote_bugs & BUG_CHOKES_ON_RSA)) {
+    if ((ssh->remote_bugs & BUG_CHOKES_ON_RSA)) {
        /* We must not attempt PK auth. Pretend we've already tried it. */
-       tried_publickey = tried_agent = 1;
+       s->tried_publickey = s->tried_agent = 1;
     } else {
-       tried_publickey = tried_agent = 0;
+       s->tried_publickey = s->tried_agent = 0;
     }
-    tis_auth_refused = ccard_auth_refused = 0;
-    /* Load the public half of cfg.keyfile so we notice if it's in Pageant */
-    if (*cfg.keyfile) {
-       if (!rsakey_pubblob(cfg.keyfile, &publickey_blob, &publickey_bloblen))
-           publickey_blob = NULL;
+    s->tis_auth_refused = s->ccard_auth_refused = 0;
+    /* Load the public half of ssh->cfg.keyfile so we notice if it's in Pageant */
+    if (!filename_is_null(ssh->cfg.keyfile)) {
+       if (!rsakey_pubblob(&ssh->cfg.keyfile,
+                           &s->publickey_blob, &s->publickey_bloblen, NULL))
+           s->publickey_blob = NULL;
     } else
-       publickey_blob = NULL;
+       s->publickey_blob = NULL;
 
-    while (pktin.type == SSH1_SMSG_FAILURE) {
-       static char password[100];
-       static char prompt[200];
-       static int pos;
-       static char c;
-       static int pwpkt_type;
-       pwpkt_type = SSH1_CMSG_AUTH_PASSWORD;
+    while (pktin->type == SSH1_SMSG_FAILURE) {
+       s->pwpkt_type = SSH1_CMSG_AUTH_PASSWORD;
 
-       if (agent_exists() && !tried_agent) {
+       if (agent_exists() && !s->tried_agent) {
            /*
             * Attempt RSA authentication using Pageant.
             */
-           static unsigned char request[5], *response, *p;
-           static int responselen;
-           static int i, nkeys;
-           static int authed = FALSE;
            void *r;
 
-           tried_agent = 1;
+           s->authed = FALSE;
+           s->tried_agent = 1;
            logevent("Pageant is running. Requesting keys.");
 
            /* Request the keys held by the agent. */
-           PUT_32BIT(request, 1);
-           request[4] = SSH1_AGENTC_REQUEST_RSA_IDENTITIES;
-           agent_query(request, 5, &r, &responselen);
-           response = (unsigned char *) r;
-           if (response && responselen >= 5 &&
-               response[4] == SSH1_AGENT_RSA_IDENTITIES_ANSWER) {
-               p = response + 5;
-               nkeys = GET_32BIT(p);
-               p += 4;
+           PUT_32BIT(s->request, 1);
+           s->request[4] = SSH1_AGENTC_REQUEST_RSA_IDENTITIES;
+           if (!agent_query(s->request, 5, &r, &s->responselen,
+                            ssh_agent_callback, ssh)) {
+               do {
+                   crReturn(0);
+                   if (pktin) {
+                       bombout(("Unexpected data from server while waiting"
+                                " for agent response"));
+                       crStop(0);
+                   }
+               } while (pktin || inlen > 0);
+               r = ssh->agent_response;
+               s->responselen = ssh->agent_response_len;
+           }
+           s->response = (unsigned char *) r;
+           if (s->response && s->responselen >= 5 &&
+               s->response[4] == SSH1_AGENT_RSA_IDENTITIES_ANSWER) {
+               s->p = s->response + 5;
+               s->nkeys = GET_32BIT(s->p);
+               s->p += 4;
                {
                    char buf[64];
-                   sprintf(buf, "Pageant has %d SSH1 keys", nkeys);
+                   sprintf(buf, "Pageant has %d SSH1 keys", s->nkeys);
                    logevent(buf);
                }
-               for (i = 0; i < nkeys; i++) {
-                   static struct RSAKey key;
-                   static Bignum challenge;
-                   static char *commentp;
-                   static int commentlen;
-
+               for (s->keyi = 0; s->keyi < s->nkeys; s->keyi++) {
                    {
                        char buf[64];
-                       sprintf(buf, "Trying Pageant key #%d", i);
+                       sprintf(buf, "Trying Pageant key #%d", s->keyi);
                        logevent(buf);
                    }
-                   if (publickey_blob &&
-                       !memcmp(p, publickey_blob, publickey_bloblen)) {
+                   if (s->publickey_blob &&
+                       !memcmp(s->p, s->publickey_blob,
+                               s->publickey_bloblen)) {
                        logevent("This key matches configured key file");
-                       tried_publickey = 1;
+                       s->tried_publickey = 1;
+                   }
+                   s->p += 4;
+                   {
+                       int n, ok = FALSE;
+                       do {           /* do while (0) to make breaking easy */
+                           n = ssh1_read_bignum
+                               (s->p, s->responselen-(s->p-s->response),
+                                &s->key.exponent);
+                           if (n < 0)
+                               break;
+                           s->p += n;
+                           n = ssh1_read_bignum
+                               (s->p, s->responselen-(s->p-s->response),
+                                &s->key.modulus);
+                           if (n < 0)
+                           break;
+                           s->p += n;
+                           if (s->responselen - (s->p-s->response) < 4)
+                               break;
+                           s->commentlen = GET_32BIT(s->p);
+                           s->p += 4;
+                           if (s->responselen - (s->p-s->response) <
+                               s->commentlen)
+                               break;
+                           s->commentp = (char *)s->p;
+                           s->p += s->commentlen;
+                           ok = TRUE;
+                       } while (0);
+                       if (!ok) {
+                           logevent("Pageant key list packet was truncated");
+                           break;
+                       }
                    }
-                   p += 4;
-                   p += ssh1_read_bignum(p, &key.exponent);
-                   p += ssh1_read_bignum(p, &key.modulus);
-                   commentlen = GET_32BIT(p);
-                   p += 4;
-                   commentp = p;
-                   p += commentlen;
-                   send_packet(SSH1_CMSG_AUTH_RSA,
-                               PKT_BIGNUM, key.modulus, PKT_END);
-                   crWaitUntil(ispkt);
-                   if (pktin.type != SSH1_SMSG_AUTH_RSA_CHALLENGE) {
+                   send_packet(ssh, SSH1_CMSG_AUTH_RSA,
+                               PKT_BIGNUM, s->key.modulus, PKT_END);
+                   crWaitUntil(pktin);
+                   if (pktin->type != SSH1_SMSG_AUTH_RSA_CHALLENGE) {
                        logevent("Key refused");
                        continue;
                    }
                    logevent("Received RSA challenge");
-                   ssh1_read_bignum(pktin.body, &challenge);
+                   if ((s->challenge = ssh1_pkt_getmp(pktin)) == NULL) {
+                       bombout(("Server's RSA challenge was badly formatted"));
+                       crStop(0);
+                   }
+
                    {
                        char *agentreq, *q, *ret;
                        void *vret;
                        int len, retlen;
                        len = 1 + 4;   /* message type, bit count */
-                       len += ssh1_bignum_length(key.exponent);
-                       len += ssh1_bignum_length(key.modulus);
-                       len += ssh1_bignum_length(challenge);
+                       len += ssh1_bignum_length(s->key.exponent);
+                       len += ssh1_bignum_length(s->key.modulus);
+                       len += ssh1_bignum_length(s->challenge);
                        len += 16;     /* session id */
                        len += 4;      /* response format */
-                       agentreq = smalloc(4 + len);
+                       agentreq = snewn(4 + len, char);
                        PUT_32BIT(agentreq, len);
                        q = agentreq + 4;
                        *q++ = SSH1_AGENTC_RSA_CHALLENGE;
-                       PUT_32BIT(q, bignum_bitcount(key.modulus));
+                       PUT_32BIT(q, bignum_bitcount(s->key.modulus));
                        q += 4;
-                       q += ssh1_write_bignum(q, key.exponent);
-                       q += ssh1_write_bignum(q, key.modulus);
-                       q += ssh1_write_bignum(q, challenge);
-                       memcpy(q, session_id, 16);
+                       q += ssh1_write_bignum(q, s->key.exponent);
+                       q += ssh1_write_bignum(q, s->key.modulus);
+                       q += ssh1_write_bignum(q, s->challenge);
+                       memcpy(q, s->session_id, 16);
                        q += 16;
                        PUT_32BIT(q, 1);        /* response format */
-                       agent_query(agentreq, len + 4, &vret, &retlen);
+                       if (!agent_query(agentreq, len + 4, &vret, &retlen,
+                                        ssh_agent_callback, ssh)) {
+                           sfree(agentreq);
+                           do {
+                               crReturn(0);
+                               if (pktin) {
+                                   bombout(("Unexpected data from server"
+                                            " while waiting for agent"
+                                            " response"));
+                                   crStop(0);
+                               }
+                           } while (pktin || inlen > 0);
+                           vret = ssh->agent_response;
+                           retlen = ssh->agent_response_len;
+                       } else
+                           sfree(agentreq);
                        ret = vret;
-                       sfree(agentreq);
                        if (ret) {
                            if (ret[4] == SSH1_AGENT_RSA_RESPONSE) {
                                logevent("Sending Pageant's response");
-                               send_packet(SSH1_CMSG_AUTH_RSA_RESPONSE,
+                               send_packet(ssh, SSH1_CMSG_AUTH_RSA_RESPONSE,
                                            PKT_DATA, ret + 5, 16,
                                            PKT_END);
                                sfree(ret);
-                               crWaitUntil(ispkt);
-                               if (pktin.type == SSH1_SMSG_SUCCESS) {
+                               crWaitUntil(pktin);
+                               if (pktin->type == SSH1_SMSG_SUCCESS) {
                                    logevent
                                        ("Pageant's response accepted");
                                    if (flags & FLAG_VERBOSE) {
-                                       c_write_str
-                                           ("Authenticated using RSA key \"");
-                                       c_write(commentp, commentlen);
-                                       c_write_str("\" from agent\r\n");
+                                       c_write_str(ssh, "Authenticated using"
+                                                   " RSA key \"");
+                                       c_write(ssh, s->commentp,
+                                               s->commentlen);
+                                       c_write_str(ssh, "\" from agent\r\n");
                                    }
-                                   authed = TRUE;
+                                   s->authed = TRUE;
                                } else
                                    logevent
                                        ("Pageant's response not accepted");
@@ -2486,105 +3168,114 @@ static int do_ssh1_login(unsigned char *in, int inlen, int ispkt)
                            logevent("No reply received from Pageant");
                        }
                    }
-                   freebn(key.exponent);
-                   freebn(key.modulus);
-                   freebn(challenge);
-                   if (authed)
+                   freebn(s->key.exponent);
+                   freebn(s->key.modulus);
+                   freebn(s->challenge);
+                   if (s->authed)
                        break;
                }
+               sfree(s->response);
            }
-           if (authed)
+           if (s->authed)
                break;
        }
-       if (*cfg.keyfile && !tried_publickey)
-           pwpkt_type = SSH1_CMSG_AUTH_RSA;
+       if (!filename_is_null(ssh->cfg.keyfile) && !s->tried_publickey)
+           s->pwpkt_type = SSH1_CMSG_AUTH_RSA;
 
-       if (cfg.try_tis_auth &&
-           (supported_auths_mask & (1 << SSH1_AUTH_TIS)) &&
-           !tis_auth_refused) {
-           pwpkt_type = SSH1_CMSG_AUTH_TIS_RESPONSE;
+       if (ssh->cfg.try_tis_auth &&
+           (s->supported_auths_mask & (1 << SSH1_AUTH_TIS)) &&
+           !s->tis_auth_refused) {
+           s->pwpkt_type = SSH1_CMSG_AUTH_TIS_RESPONSE;
            logevent("Requested TIS authentication");
-           send_packet(SSH1_CMSG_AUTH_TIS, PKT_END);
-           crWaitUntil(ispkt);
-           if (pktin.type != SSH1_SMSG_AUTH_TIS_CHALLENGE) {
+           send_packet(ssh, SSH1_CMSG_AUTH_TIS, PKT_END);
+           crWaitUntil(pktin);
+           if (pktin->type != SSH1_SMSG_AUTH_TIS_CHALLENGE) {
                logevent("TIS authentication declined");
                if (flags & FLAG_INTERACTIVE)
-                   c_write_str("TIS authentication refused.\r\n");
-               tis_auth_refused = 1;
+                   c_write_str(ssh, "TIS authentication refused.\r\n");
+               s->tis_auth_refused = 1;
                continue;
            } else {
-               int challengelen = ((pktin.body[0] << 24) |
-                                   (pktin.body[1] << 16) |
-                                   (pktin.body[2] << 8) |
-                                   (pktin.body[3]));
+               char *challenge;
+               int challengelen;
+
+               ssh_pkt_getstring(pktin, &challenge, &challengelen);
+               if (!challenge) {
+                   bombout(("TIS challenge packet was badly formed"));
+                   crStop(0);
+               }
                logevent("Received TIS challenge");
-               if (challengelen > sizeof(prompt) - 1)
-                   challengelen = sizeof(prompt) - 1;  /* prevent overrun */
-               memcpy(prompt, pktin.body + 4, challengelen);
+               if (challengelen > sizeof(s->prompt) - 1)
+                   challengelen = sizeof(s->prompt) - 1;/* prevent overrun */
+               memcpy(s->prompt, challenge, challengelen);
                /* Prompt heuristic comes from OpenSSH */
-               strncpy(prompt + challengelen,
-                       memchr(prompt, '\n', challengelen) ?
+               strncpy(s->prompt + challengelen,
+                       memchr(s->prompt, '\n', challengelen) ?
                        "": "\r\nResponse: ",
-                       (sizeof prompt) - challengelen);
-               prompt[(sizeof prompt) - 1] = '\0';
+                       (sizeof s->prompt) - challengelen);
+               s->prompt[(sizeof s->prompt) - 1] = '\0';
            }
        }
-       if (cfg.try_tis_auth &&
-           (supported_auths_mask & (1 << SSH1_AUTH_CCARD)) &&
-           !ccard_auth_refused) {
-           pwpkt_type = SSH1_CMSG_AUTH_CCARD_RESPONSE;
+       if (ssh->cfg.try_tis_auth &&
+           (s->supported_auths_mask & (1 << SSH1_AUTH_CCARD)) &&
+           !s->ccard_auth_refused) {
+           s->pwpkt_type = SSH1_CMSG_AUTH_CCARD_RESPONSE;
            logevent("Requested CryptoCard authentication");
-           send_packet(SSH1_CMSG_AUTH_CCARD, PKT_END);
-           crWaitUntil(ispkt);
-           if (pktin.type != SSH1_SMSG_AUTH_CCARD_CHALLENGE) {
+           send_packet(ssh, SSH1_CMSG_AUTH_CCARD, PKT_END);
+           crWaitUntil(pktin);
+           if (pktin->type != SSH1_SMSG_AUTH_CCARD_CHALLENGE) {
                logevent("CryptoCard authentication declined");
-               c_write_str("CryptoCard authentication refused.\r\n");
-               ccard_auth_refused = 1;
+               c_write_str(ssh, "CryptoCard authentication refused.\r\n");
+               s->ccard_auth_refused = 1;
                continue;
            } else {
-               int challengelen = ((pktin.body[0] << 24) |
-                                   (pktin.body[1] << 16) |
-                                   (pktin.body[2] << 8) |
-                                   (pktin.body[3]));
+               char *challenge;
+               int challengelen;
+
+               ssh_pkt_getstring(pktin, &challenge, &challengelen);
+               if (!challenge) {
+                   bombout(("CryptoCard challenge packet was badly formed"));
+                   crStop(0);
+               }
                logevent("Received CryptoCard challenge");
-               if (challengelen > sizeof(prompt) - 1)
-                   challengelen = sizeof(prompt) - 1;  /* prevent overrun */
-               memcpy(prompt, pktin.body + 4, challengelen);
-               strncpy(prompt + challengelen,
-                       memchr(prompt, '\n', challengelen) ?
+               if (challengelen > sizeof(s->prompt) - 1)
+                   challengelen = sizeof(s->prompt) - 1;/* prevent overrun */
+               memcpy(s->prompt, challenge, challengelen);
+               strncpy(s->prompt + challengelen,
+                       memchr(s->prompt, '\n', challengelen) ?
                        "" : "\r\nResponse: ",
-                       sizeof(prompt) - challengelen);
-               prompt[sizeof(prompt) - 1] = '\0';
+                       sizeof(s->prompt) - challengelen);
+               s->prompt[sizeof(s->prompt) - 1] = '\0';
            }
        }
-       if (pwpkt_type == SSH1_CMSG_AUTH_PASSWORD) {
-           sprintf(prompt, "%.90s@%.90s's password: ",
-                   username, savedhost);
+       if (s->pwpkt_type == SSH1_CMSG_AUTH_PASSWORD) {
+           sprintf(s->prompt, "%.90s@%.90s's password: ",
+                   s->username, ssh->savedhost);
        }
-       if (pwpkt_type == SSH1_CMSG_AUTH_RSA) {
+       if (s->pwpkt_type == SSH1_CMSG_AUTH_RSA) {
            char *comment = NULL;
            int type;
            char msgbuf[256];
            if (flags & FLAG_VERBOSE)
-               c_write_str("Trying public key authentication.\r\n");
-           sprintf(msgbuf, "Trying public key \"%.200s\"", cfg.keyfile);
-           logevent(msgbuf);
-           type = key_type(cfg.keyfile);
+               c_write_str(ssh, "Trying public key authentication.\r\n");
+           logeventf(ssh, "Trying public key \"%s\"",
+                     filename_to_str(&ssh->cfg.keyfile));
+           type = key_type(&ssh->cfg.keyfile);
            if (type != SSH_KEYTYPE_SSH1) {
                sprintf(msgbuf, "Key is of wrong type (%s)",
                        key_type_to_str(type));
                logevent(msgbuf);
-               c_write_str(msgbuf);
-               c_write_str("\r\n");
-               tried_publickey = 1;
+               c_write_str(ssh, msgbuf);
+               c_write_str(ssh, "\r\n");
+               s->tried_publickey = 1;
                continue;
            }
-           if (!rsakey_encrypted(cfg.keyfile, &comment)) {
+           if (!rsakey_encrypted(&ssh->cfg.keyfile, &comment)) {
                if (flags & FLAG_VERBOSE)
-                   c_write_str("No passphrase required.\r\n");
+                   c_write_str(ssh, "No passphrase required.\r\n");
                goto tryauth;
            }
-           sprintf(prompt, "Passphrase for key \"%.100s\": ", comment);
+           sprintf(s->prompt, "Passphrase for key \"%.100s\": ", comment);
            sfree(comment);
        }
 
@@ -2594,108 +3285,124 @@ static int do_ssh1_login(unsigned char *in, int inlen, int ispkt)
         * authentication.
         */
        if (ssh_get_line) {
-           if (!ssh_get_line(prompt, password, sizeof(password), TRUE)) {
+           if (!ssh_get_line(s->prompt, s->password,
+                             sizeof(s->password), TRUE)) {
                /*
                 * get_line failed to get a password (for example
                 * because one was supplied on the command line
                 * which has already failed to work). Terminate.
                 */
-               send_packet(SSH1_MSG_DISCONNECT,
+               send_packet(ssh, SSH1_MSG_DISCONNECT,
                            PKT_STR, "No more passwords available to try",
                            PKT_END);
                logevent("Unable to authenticate");
-               connection_fatal("Unable to authenticate");
-               ssh_state = SSH_STATE_CLOSED;
-               crReturn(1);
+               connection_fatal(ssh->frontend, "Unable to authenticate");
+               ssh->close_expected = TRUE;
+                ssh_closing((Plug)ssh, NULL, 0, 0);
+               crStop(1);
            }
        } else {
            /* Prompt may have come from server. We've munged it a bit, so
             * we know it to be zero-terminated at least once. */
-           static int ret;
-           c_write_untrusted(prompt, strlen(prompt));
-           pos = 0;
+           int ret;                   /* need not be saved over crReturn */
+           c_write_untrusted(ssh, s->prompt, strlen(s->prompt));
+           s->pos = 0;
 
-           setup_userpass_input(password, sizeof(password), 0);
+           setup_userpass_input(ssh, s->password, sizeof(s->password), 0);
            do {
-               crWaitUntil(!ispkt);
-               ret = process_userpass_input(in, inlen);
+               crWaitUntil(!pktin);
+               ret = process_userpass_input(ssh, in, inlen);
            } while (ret == 0);
            if (ret < 0)
                cleanup_exit(0);
-           c_write_str("\r\n");
+           c_write_str(ssh, "\r\n");
        }
 
       tryauth:
-       if (pwpkt_type == SSH1_CMSG_AUTH_RSA) {
+       if (s->pwpkt_type == SSH1_CMSG_AUTH_RSA) {
            /*
             * Try public key authentication with the specified
             * key file.
             */
-           static struct RSAKey pubkey;
-           static Bignum challenge, response;
-           static int i;
-           static unsigned char buffer[32];
-
-           tried_publickey = 1;
-           i = loadrsakey(cfg.keyfile, &pubkey, password);
-           if (i == 0) {
-               c_write_str("Couldn't load private key from ");
-               c_write_str(cfg.keyfile);
-               c_write_str(".\r\n");
-               continue;              /* go and try password */
-           }
-           if (i == -1) {
-               c_write_str("Wrong passphrase.\r\n");
-               tried_publickey = 0;
-               continue;              /* try again */
+           s->tried_publickey = 1;
+           
+           {
+               const char *error = NULL;
+               int ret = loadrsakey(&ssh->cfg.keyfile, &s->key, s->password,
+                                    &error);
+               if (ret == 0) {
+                   c_write_str(ssh, "Couldn't load private key from ");
+                   c_write_str(ssh, filename_to_str(&ssh->cfg.keyfile));
+                   c_write_str(ssh, " (");
+                   c_write_str(ssh, error);
+                   c_write_str(ssh, ").\r\n");
+                   continue;          /* go and try password */
+               }
+               if (ret == -1) {
+                   c_write_str(ssh, "Wrong passphrase.\r\n");
+                   s->tried_publickey = 0;
+                   continue;          /* try again */
+               }
            }
 
            /*
             * Send a public key attempt.
             */
-           send_packet(SSH1_CMSG_AUTH_RSA,
-                       PKT_BIGNUM, pubkey.modulus, PKT_END);
+           send_packet(ssh, SSH1_CMSG_AUTH_RSA,
+                       PKT_BIGNUM, s->key.modulus, PKT_END);
 
-           crWaitUntil(ispkt);
-           if (pktin.type == SSH1_SMSG_FAILURE) {
-               c_write_str("Server refused our public key.\r\n");
+           crWaitUntil(pktin);
+           if (pktin->type == SSH1_SMSG_FAILURE) {
+               c_write_str(ssh, "Server refused our public key.\r\n");
                continue;              /* go and try password */
            }
-           if (pktin.type != SSH1_SMSG_AUTH_RSA_CHALLENGE) {
+           if (pktin->type != SSH1_SMSG_AUTH_RSA_CHALLENGE) {
                bombout(("Bizarre response to offer of public key"));
-               crReturn(0);
+               crStop(0);
            }
-           ssh1_read_bignum(pktin.body, &challenge);
-           response = rsadecrypt(challenge, &pubkey);
-           freebn(pubkey.private_exponent);    /* burn the evidence */
 
-           for (i = 0; i < 32; i++) {
-               buffer[i] = bignum_byte(response, 31 - i);
-           }
+           {
+               int i;
+               unsigned char buffer[32];
+               Bignum challenge, response;
+
+               if ((challenge = ssh1_pkt_getmp(pktin)) == NULL) {
+                   bombout(("Server's RSA challenge was badly formatted"));
+                   crStop(0);
+               }
+               response = rsadecrypt(challenge, &s->key);
+               freebn(s->key.private_exponent);/* burn the evidence */
+
+               for (i = 0; i < 32; i++) {
+                   buffer[i] = bignum_byte(response, 31 - i);
+               }
 
-           MD5Init(&md5c);
-           MD5Update(&md5c, buffer, 32);
-           MD5Update(&md5c, session_id, 16);
-           MD5Final(buffer, &md5c);
+               MD5Init(&md5c);
+               MD5Update(&md5c, buffer, 32);
+               MD5Update(&md5c, s->session_id, 16);
+               MD5Final(buffer, &md5c);
 
-           send_packet(SSH1_CMSG_AUTH_RSA_RESPONSE,
-                       PKT_DATA, buffer, 16, PKT_END);
+               send_packet(ssh, SSH1_CMSG_AUTH_RSA_RESPONSE,
+                           PKT_DATA, buffer, 16, PKT_END);
 
-           crWaitUntil(ispkt);
-           if (pktin.type == SSH1_SMSG_FAILURE) {
+               freebn(challenge);
+               freebn(response);
+           }
+
+           crWaitUntil(pktin);
+           if (pktin->type == SSH1_SMSG_FAILURE) {
                if (flags & FLAG_VERBOSE)
-                   c_write_str
-                       ("Failed to authenticate with our public key.\r\n");
+                   c_write_str(ssh, "Failed to authenticate with"
+                               " our public key.\r\n");
                continue;              /* go and try password */
-           } else if (pktin.type != SSH1_SMSG_SUCCESS) {
-               bombout(
-                       ("Bizarre response to RSA authentication response"));
-               crReturn(0);
+           } else if (pktin->type != SSH1_SMSG_SUCCESS) {
+               bombout(("Bizarre response to RSA authentication response"));
+               crStop(0);
            }
 
            break;                     /* we're through! */
        } else {
-           if (pwpkt_type == SSH1_CMSG_AUTH_PASSWORD) {
+           if (s->pwpkt_type == SSH1_CMSG_AUTH_PASSWORD) {
                /*
                 * Defence against traffic analysis: we send a
                 * whole bunch of packets containing strings of
@@ -2734,7 +3441,7 @@ static int do_ssh1_login(unsigned char *in, int inlen, int ispkt)
                 * For this server we are left with no defences
                 * against password length sniffing.
                 */
-               if (!(ssh_remote_bugs & BUG_CHOKES_ON_SSH1_IGNORE)) {
+               if (!(ssh->remote_bugs & BUG_CHOKES_ON_SSH1_IGNORE)) {
                    /*
                     * The server can deal with SSH1_MSG_IGNORE, so
                     * we can use the primary defence.
@@ -2742,7 +3449,7 @@ static int do_ssh1_login(unsigned char *in, int inlen, int ispkt)
                    int bottom, top, pwlen, i;
                    char *randomstr;
 
-                   pwlen = strlen(password);
+                   pwlen = strlen(s->password);
                    if (pwlen < 16) {
                        bottom = 0;    /* zero length passwords are OK! :-) */
                        top = 15;
@@ -2753,50 +3460,53 @@ static int do_ssh1_login(unsigned char *in, int inlen, int ispkt)
 
                    assert(pwlen >= bottom && pwlen <= top);
 
-                   randomstr = smalloc(top + 1);
+                   randomstr = snewn(top + 1, char);
 
                    for (i = bottom; i <= top; i++) {
-                       if (i == pwlen)
-                           defer_packet(pwpkt_type, PKT_STR, password,
-                                        PKT_END);
-                       else {
+                       if (i == pwlen) {
+                           defer_packet(ssh, s->pwpkt_type,
+                                        PKTT_PASSWORD, PKT_STR, s->password,
+                                        PKTT_OTHER, PKT_END);
+                       } else {
                            for (j = 0; j < i; j++) {
                                do {
                                    randomstr[j] = random_byte();
                                } while (randomstr[j] == '\0');
                            }
                            randomstr[i] = '\0';
-                           defer_packet(SSH1_MSG_IGNORE,
+                           defer_packet(ssh, SSH1_MSG_IGNORE,
                                         PKT_STR, randomstr, PKT_END);
                        }
                    }
                    logevent("Sending password with camouflage packets");
-                   ssh_pkt_defersend();
+                   ssh_pkt_defersend(ssh);
+                   sfree(randomstr);
                } 
-               else if (!(ssh_remote_bugs & BUG_NEEDS_SSH1_PLAIN_PASSWORD)) {
+               else if (!(ssh->remote_bugs & BUG_NEEDS_SSH1_PLAIN_PASSWORD)) {
                    /*
                     * The server can't deal with SSH1_MSG_IGNORE
                     * but can deal with padded passwords, so we
                     * can use the secondary defence.
                     */
                    char string[64];
-                   char *s;
+                   char *ss;
                    int len;
 
-                   len = strlen(password);
+                   len = strlen(s->password);
                    if (len < sizeof(string)) {
-                       s = string;
-                       strcpy(string, password);
+                       ss = string;
+                       strcpy(string, s->password);
                        len++;         /* cover the zero byte */
                        while (len < sizeof(string)) {
                            string[len++] = (char) random_byte();
                        }
                    } else {
-                       s = password;
+                       ss = s->password;
                    }
                    logevent("Sending length-padded password");
-                   send_packet(pwpkt_type, PKT_INT, len,
-                               PKT_DATA, s, len, PKT_END);
+                   send_packet(ssh, s->pwpkt_type, PKTT_PASSWORD,
+                               PKT_INT, len, PKT_DATA, ss, len,
+                               PKTT_OTHER, PKT_END);
                } else {
                    /*
                     * The server has _both_
@@ -2805,29 +3515,28 @@ static int do_ssh1_login(unsigned char *in, int inlen, int ispkt)
                     * therefore nothing we can do.
                     */
                    int len;
-                   len = strlen(password);
+                   len = strlen(s->password);
                    logevent("Sending unpadded password");
-                   send_packet(pwpkt_type, PKT_INT, len,
-                               PKT_DATA, password, len, PKT_END);
+                   send_packet(ssh, s->pwpkt_type,
+                               PKTT_PASSWORD, PKT_INT, len,
+                               PKT_DATA, s->password, len,
+                               PKTT_OTHER, PKT_END);
                }
            } else {
-               send_packet(pwpkt_type, PKT_STR, password, PKT_END);
+               send_packet(ssh, s->pwpkt_type, PKTT_PASSWORD,
+                           PKT_STR, s->password, PKTT_OTHER, PKT_END);
            }
        }
        logevent("Sent password");
-       memset(password, 0, strlen(password));
-       crWaitUntil(ispkt);
-       if (pktin.type == SSH1_SMSG_FAILURE) {
+       memset(s->password, 0, strlen(s->password));
+       crWaitUntil(pktin);
+       if (pktin->type == SSH1_SMSG_FAILURE) {
            if (flags & FLAG_VERBOSE)
-               c_write_str("Access denied\r\n");
+               c_write_str(ssh, "Access denied\r\n");
            logevent("Authentication refused");
-       } else if (pktin.type == SSH1_MSG_DISCONNECT) {
-           logevent("Received disconnect request");
-           ssh_state = SSH_STATE_CLOSED;
-           crReturn(1);
-       } else if (pktin.type != SSH1_SMSG_SUCCESS) {
-           bombout(("Strange packet received, type %d", pktin.type));
-           crReturn(0);
+       } else if (pktin->type != SSH1_SMSG_SUCCESS) {
+           bombout(("Strange packet received, type %d", pktin->type));
+           crStop(0);
        }
     }
 
@@ -2838,6 +3547,13 @@ static int do_ssh1_login(unsigned char *in, int inlen, int ispkt)
 
 void sshfwd_close(struct ssh_channel *c)
 {
+    Ssh ssh = c->ssh;
+
+    if (ssh->state != SSH_STATE_SESSION) {
+       assert(ssh->state == SSH_STATE_CLOSED);
+       return;
+    }
+
     if (c && !c->closes) {
        /*
         * If the channel's remoteid is -1, we have sent
@@ -2847,16 +3563,17 @@ void sshfwd_close(struct ssh_channel *c)
         * open, we can close it then.
         */
        if (((int)c->remoteid) != -1) {
-           if (ssh_version == 1) {
-               send_packet(SSH1_MSG_CHANNEL_CLOSE, PKT_INT, c->remoteid,
+           if (ssh->version == 1) {
+               send_packet(ssh, SSH1_MSG_CHANNEL_CLOSE, PKT_INT, c->remoteid,
                            PKT_END);
            } else {
-               ssh2_pkt_init(SSH2_MSG_CHANNEL_CLOSE);
-               ssh2_pkt_adduint32(c->remoteid);
-               ssh2_pkt_send();
+               struct Packet *pktout;
+               pktout = ssh2_pkt_init(SSH2_MSG_CHANNEL_CLOSE);
+               ssh2_pkt_adduint32(pktout, c->remoteid);
+               ssh2_pkt_send(ssh, pktout);
            }
        }
-       c->closes = 1;
+       c->closes = 1;                 /* sent MSG_CLOSE */
        if (c->type == CHAN_X11) {
            c->u.x11.s = NULL;
            logevent("Forwarded X11 connection terminated");
@@ -2870,10 +3587,19 @@ void sshfwd_close(struct ssh_channel *c)
 
 int sshfwd_write(struct ssh_channel *c, char *buf, int len)
 {
-    if (ssh_version == 1) {
-       send_packet(SSH1_MSG_CHANNEL_DATA,
+    Ssh ssh = c->ssh;
+
+    if (ssh->state != SSH_STATE_SESSION) {
+       assert(ssh->state == SSH_STATE_CLOSED);
+       return 0;
+    }
+
+    if (ssh->version == 1) {
+       send_packet(ssh, SSH1_MSG_CHANNEL_DATA,
                    PKT_INT, c->remoteid,
-                   PKT_INT, len, PKT_DATA, buf, len, PKT_END);
+                   PKTT_DATA,
+                   PKT_INT, len, PKT_DATA, buf, len,
+                   PKTT_OTHER, PKT_END);
        /*
         * In SSH1 we can return 0 here - implying that forwarded
         * connections are never individually throttled - because
@@ -2890,224 +3616,866 @@ int sshfwd_write(struct ssh_channel *c, char *buf, int len)
 
 void sshfwd_unthrottle(struct ssh_channel *c, int bufsize)
 {
-    if (ssh_version == 1) {
+    Ssh ssh = c->ssh;
+
+    if (ssh->state != SSH_STATE_SESSION) {
+       assert(ssh->state == SSH_STATE_CLOSED);
+       return;
+    }
+
+    if (ssh->version == 1) {
        if (c->v.v1.throttling && bufsize < SSH1_BUFFER_LIMIT) {
            c->v.v1.throttling = 0;
-           ssh1_throttle(-1);
+           ssh1_throttle(ssh, -1);
        }
     } else {
        ssh2_set_window(c, OUR_V2_WINSIZE - bufsize);
     }
 }
 
-static void ssh1_protocol(unsigned char *in, int inlen, int ispkt)
+static void ssh_queueing_handler(Ssh ssh, struct Packet *pktin)
 {
-    crBegin;
+    struct queued_handler *qh = ssh->qhead;
 
-    random_init();
+    assert(qh != NULL);
 
-    while (!do_ssh1_login(in, inlen, ispkt)) {
-       crReturnV;
+    assert(pktin->type == qh->msg1 || pktin->type == qh->msg2);
+
+    if (qh->msg1 > 0) {
+       assert(ssh->packet_dispatch[qh->msg1] == ssh_queueing_handler);
+       ssh->packet_dispatch[qh->msg1] = NULL;
+    }
+    if (qh->msg2 > 0) {
+       assert(ssh->packet_dispatch[qh->msg2] == ssh_queueing_handler);
+       ssh->packet_dispatch[qh->msg2] = NULL;
     }
-    if (ssh_state == SSH_STATE_CLOSED)
-       crReturnV;
 
-    if (cfg.agentfwd && agent_exists()) {
-       logevent("Requesting agent forwarding");
-       send_packet(SSH1_CMSG_AGENT_REQUEST_FORWARDING, PKT_END);
-       do {
-           crReturnV;
-       } while (!ispkt);
-       if (pktin.type != SSH1_SMSG_SUCCESS
-           && pktin.type != SSH1_SMSG_FAILURE) {
-           bombout(("Protocol confusion"));
-           crReturnV;
-       } else if (pktin.type == SSH1_SMSG_FAILURE) {
-           logevent("Agent forwarding refused");
-       } else {
-           logevent("Agent forwarding enabled");
-           ssh_agentfwd_enabled = TRUE;
+    if (qh->next) {
+       ssh->qhead = qh->next;
+
+       if (ssh->qhead->msg1 > 0) {
+           assert(ssh->packet_dispatch[ssh->qhead->msg1] == NULL);
+           ssh->packet_dispatch[ssh->qhead->msg1] = ssh_queueing_handler;
        }
+       if (ssh->qhead->msg2 > 0) {
+           assert(ssh->packet_dispatch[ssh->qhead->msg2] == NULL);
+           ssh->packet_dispatch[ssh->qhead->msg2] = ssh_queueing_handler;
+       }
+    } else {
+       ssh->qhead = ssh->qtail = NULL;
+       ssh->packet_dispatch[pktin->type] = NULL;
     }
 
-    if (cfg.x11_forward) {
-       char proto[20], data[64];
-       logevent("Requesting X11 forwarding");
-       x11_invent_auth(proto, sizeof(proto), data, sizeof(data));
-       if (ssh1_local_protoflags & SSH1_PROTOFLAG_SCREEN_NUMBER) {
-           send_packet(SSH1_CMSG_X11_REQUEST_FORWARDING,
-                       PKT_STR, proto, PKT_STR, data,
-                       PKT_INT, 0, PKT_END);
-       } else {
-           send_packet(SSH1_CMSG_X11_REQUEST_FORWARDING,
-                       PKT_STR, proto, PKT_STR, data, PKT_END);
+    qh->handler(ssh, pktin, qh->ctx);
+
+    sfree(qh);
+}
+
+static void ssh_queue_handler(Ssh ssh, int msg1, int msg2,
+                             chandler_fn_t handler, void *ctx)
+{
+    struct queued_handler *qh;
+
+    qh = snew(struct queued_handler);
+    qh->msg1 = msg1;
+    qh->msg2 = msg2;
+    qh->handler = handler;
+    qh->ctx = ctx;
+    qh->next = NULL;
+
+    if (ssh->qtail == NULL) {
+       ssh->qhead = qh;
+
+       if (qh->msg1 > 0) {
+           assert(ssh->packet_dispatch[qh->msg1] == NULL);
+           ssh->packet_dispatch[qh->msg1] = ssh_queueing_handler;
        }
-       do {
-           crReturnV;
-       } while (!ispkt);
-       if (pktin.type != SSH1_SMSG_SUCCESS
-           && pktin.type != SSH1_SMSG_FAILURE) {
-           bombout(("Protocol confusion"));
-           crReturnV;
-       } else if (pktin.type == SSH1_SMSG_FAILURE) {
-           logevent("X11 forwarding refused");
-       } else {
-           logevent("X11 forwarding enabled");
-           ssh_X11_fwd_enabled = TRUE;
+       if (qh->msg2 > 0) {
+           assert(ssh->packet_dispatch[qh->msg2] == NULL);
+           ssh->packet_dispatch[qh->msg2] = ssh_queueing_handler;
        }
+    } else {
+       ssh->qtail->next = qh;
     }
+    ssh->qtail = qh;
+}
 
-    {
-       char type;
-       static char *e;
-       int n;
+static void ssh_rportfwd_succfail(Ssh ssh, struct Packet *pktin, void *ctx)
+{
+    struct ssh_rportfwd *rpf, *pf = (struct ssh_rportfwd *)ctx;
+
+    if (pktin->type == (ssh->version == 1 ? SSH1_SMSG_SUCCESS :
+                       SSH2_MSG_REQUEST_SUCCESS)) {
+       logeventf(ssh, "Remote port forwarding from %s enabled",
+                 pf->sportdesc);
+    } else {
+       logeventf(ssh, "Remote port forwarding from %s refused",
+                 pf->sportdesc);
+
+       rpf = del234(ssh->rportfwds, pf);
+       assert(rpf == pf);
+       free_rportfwd(pf);
+    }
+}
+
+static void ssh_setup_portfwd(Ssh ssh, const Config *cfg)
+{
+    const char *portfwd_strptr = cfg->portfwd;
+    struct ssh_portfwd *epf;
+    int i;
+
+    if (!ssh->portfwds) {
+       ssh->portfwds = newtree234(ssh_portcmp);
+    } else {
+       /*
+        * Go through the existing port forwardings and tag them
+        * with status==DESTROY. Any that we want to keep will be
+        * re-enabled (status==KEEP) as we go through the
+        * configuration and find out which bits are the same as
+        * they were before.
+        */
+       struct ssh_portfwd *epf;
+       int i;
+       for (i = 0; (epf = index234(ssh->portfwds, i)) != NULL; i++)
+           epf->status = DESTROY;
+    }
+
+    while (*portfwd_strptr) {
+       char address_family, type;
        int sport,dport,sserv,dserv;
-       char sports[256], dports[256], host[256];
-       char buf[1024];
-       struct servent *se;
+       char sports[256], dports[256], saddr[256], host[256];
+       int n;
 
-       ssh_rportfwds = newtree234(ssh_rportcmp_ssh1);
-        /* Add port forwardings. */
-       e = cfg.portfwd;
-       while (*e) {
-           type = *e++;
-           n = 0;
-           while (*e && *e != '\t')
-               sports[n++] = *e++;
-           sports[n] = 0;
-           if (*e == '\t')
-               e++;
+       address_family = 'A';
+       type = 'L';
+       if (*portfwd_strptr == 'A' ||
+           *portfwd_strptr == '4' ||
+           *portfwd_strptr == '6')
+           address_family = *portfwd_strptr++;
+       if (*portfwd_strptr == 'L' ||
+           *portfwd_strptr == 'R' ||
+           *portfwd_strptr == 'D')
+           type = *portfwd_strptr++;
+
+       saddr[0] = '\0';
+
+       n = 0;
+       while (*portfwd_strptr && *portfwd_strptr != '\t') {
+           if (*portfwd_strptr == ':') {
+               /*
+                * We've seen a colon in the middle of the
+                * source port number. This means that
+                * everything we've seen until now is the
+                * source _address_, so we'll move it into
+                * saddr and start sports from the beginning
+                * again.
+                */
+               portfwd_strptr++;
+               sports[n] = '\0';
+               if (ssh->version == 1 && type == 'R') {
+                   logeventf(ssh, "SSH1 cannot handle remote source address "
+                             "spec \"%s\"; ignoring", sports);
+               } else
+                   strcpy(saddr, sports);
+               n = 0;
+           }
+           if (n < 255) sports[n++] = *portfwd_strptr++;
+       }
+       sports[n] = 0;
+       if (type != 'D') {
+           if (*portfwd_strptr == '\t')
+               portfwd_strptr++;
            n = 0;
-           while (*e && *e != ':')
-               host[n++] = *e++;
+           while (*portfwd_strptr && *portfwd_strptr != ':') {
+               if (n < 255) host[n++] = *portfwd_strptr++;
+           }
            host[n] = 0;
-           if (*e == ':')
-               e++;
+           if (*portfwd_strptr == ':')
+               portfwd_strptr++;
            n = 0;
-           while (*e)
-               dports[n++] = *e++;
+           while (*portfwd_strptr) {
+               if (n < 255) dports[n++] = *portfwd_strptr++;
+           }
            dports[n] = 0;
-           e++;
+           portfwd_strptr++;
            dport = atoi(dports);
            dserv = 0;
            if (dport == 0) {
                dserv = 1;
-               se = getservbyname(dports, NULL);
-               if (se != NULL) {
-                   dport = ntohs(se->s_port);
-               } else {
-                   sprintf(buf,
-                           "Service lookup failed for destination port \"%s\"",
-                           dports);
-                   logevent(buf);
+               dport = net_service_lookup(dports);
+               if (!dport) {
+                   logeventf(ssh, "Service lookup failed for destination"
+                             " port \"%s\"", dports);
                }
            }
-           sport = atoi(sports);
-           sserv = 0;
-           if (sport == 0) {
-               sserv = 1;
-               se = getservbyname(sports, NULL);
-               if (se != NULL) {
-                   sport = ntohs(se->s_port);
-               } else {
-                   sprintf(buf,
-                           "Service lookup failed for source port \"%s\"",
-                           sports);
-                   logevent(buf);
-               }
+       } else {
+           while (*portfwd_strptr) portfwd_strptr++;
+           dport = dserv = -1;
+           portfwd_strptr++;          /* eat the NUL and move to next one */
+       }
+       sport = atoi(sports);
+       sserv = 0;
+       if (sport == 0) {
+           sserv = 1;
+           sport = net_service_lookup(sports);
+           if (!sport) {
+               logeventf(ssh, "Service lookup failed for source"
+                         " port \"%s\"", sports);
            }
-           if (sport && dport) {
-               if (type == 'L') {
-                   pfd_addforward(host, dport, sport);
-                   sprintf(buf, "Local port %.*s%.*s%d%.*s forwarding to"
-                           " %s:%.*s%.*s%d%.*s",
-                           sserv ? strlen(sports) : 0, sports,
-                           sserv, "(", sport, sserv, ")",
-                           host,
-                           dserv ? strlen(dports) : 0, dports,
-                           dserv, "(", dport, dserv, ")");
-                   logevent(buf);
+       }
+       if (sport && dport) {
+           /* Set up a description of the source port. */
+           struct ssh_portfwd *pfrec, *epfrec;
+
+           pfrec = snew(struct ssh_portfwd);
+           pfrec->type = type;
+           pfrec->saddr = *saddr ? dupstr(saddr) : NULL;
+           pfrec->sserv = sserv ? dupstr(sports) : NULL;
+           pfrec->sport = sport;
+           pfrec->daddr = *host ? dupstr(host) : NULL;
+           pfrec->dserv = dserv ? dupstr(dports) : NULL;
+           pfrec->dport = dport;
+           pfrec->local = NULL;
+           pfrec->remote = NULL;
+           pfrec->addressfamily = (address_family == '4' ? ADDRTYPE_IPV4 :
+                                   address_family == '6' ? ADDRTYPE_IPV6 :
+                                   ADDRTYPE_UNSPEC);
+
+           epfrec = add234(ssh->portfwds, pfrec);
+           if (epfrec != pfrec) {
+               /*
+                * We already have a port forwarding with precisely
+                * these parameters. Hence, no need to do anything;
+                * simply tag the existing one as KEEP.
+                */
+               epfrec->status = KEEP;
+               free_portfwd(pfrec);
+           } else {
+               pfrec->status = CREATE;
+           }
+       }
+    }
+
+    /*
+     * Now go through and destroy any port forwardings which were
+     * not re-enabled.
+     */
+    for (i = 0; (epf = index234(ssh->portfwds, i)) != NULL; i++)
+       if (epf->status == DESTROY) {
+           char *message;
+
+           message = dupprintf("%s port forwarding from %s%s%d",
+                               epf->type == 'L' ? "local" :
+                               epf->type == 'R' ? "remote" : "dynamic",
+                               epf->saddr ? epf->saddr : "",
+                               epf->saddr ? ":" : "",
+                               epf->sport);
+
+           if (epf->type != 'D') {
+               char *msg2 = dupprintf("%s to %s:%d", message,
+                                      epf->daddr, epf->dport);
+               sfree(message);
+               message = msg2;
+           }
+
+           logeventf(ssh, "Cancelling %s", message);
+           sfree(message);
+
+           if (epf->remote) {
+               struct ssh_rportfwd *rpf = epf->remote;
+               struct Packet *pktout;
+
+               /*
+                * Cancel the port forwarding at the server
+                * end.
+                */
+               if (ssh->version == 1) {
+                   /*
+                    * We cannot cancel listening ports on the
+                    * server side in SSH1! There's no message
+                    * to support it. Instead, we simply remove
+                    * the rportfwd record from the local end
+                    * so that any connections the server tries
+                    * to make on it are rejected.
+                    */
                } else {
-                   struct ssh_rportfwd *pf;
-                   pf = smalloc(sizeof(*pf));
-                   strcpy(pf->dhost, host);
-                   pf->dport = dport;
-                   if (add234(ssh_rportfwds, pf) != pf) {
-                       sprintf(buf, 
-                               "Duplicate remote port forwarding to %s:%d",
-                               host, dport);
-                       logevent(buf);
-                       sfree(pf);
+                   pktout = ssh2_pkt_init(SSH2_MSG_GLOBAL_REQUEST);
+                   ssh2_pkt_addstring(pktout, "cancel-tcpip-forward");
+                   ssh2_pkt_addbool(pktout, 0);/* _don't_ want reply */
+                   if (epf->saddr) {
+                       ssh2_pkt_addstring(pktout, epf->saddr);
+                   } else if (ssh->cfg.rport_acceptall) {
+                       ssh2_pkt_addstring(pktout, "0.0.0.0");
                    } else {
-                       sprintf(buf, "Requesting remote port %.*s%.*s%d%.*s"
-                               " forward to %s:%.*s%.*s%d%.*s",
-                           sserv ? strlen(sports) : 0, sports,
-                           sserv, "(", sport, sserv, ")",
-                           host,
-                           dserv ? strlen(dports) : 0, dports,
-                           dserv, "(", dport, dserv, ")");
-                       logevent(buf);
-                       send_packet(SSH1_CMSG_PORT_FORWARD_REQUEST,
-                                   PKT_INT, sport,
-                                   PKT_STR, host,
-                                   PKT_INT, dport,
-                                   PKT_END);
-                       do {
-                           crReturnV;
-                       } while (!ispkt);
-                       if (pktin.type != SSH1_SMSG_SUCCESS
-                           && pktin.type != SSH1_SMSG_FAILURE) {
-                           bombout(("Protocol confusion"));
-                           crReturnV;
-                       } else if (pktin.type == SSH1_SMSG_FAILURE) {
-                           c_write_str("Server refused port forwarding\r\n");
-                           ssh_editing = ssh_echoing = 1;
-                       }
-                       logevent("Remote port forwarding enabled");
+                       ssh2_pkt_addstring(pktout, "127.0.0.1");
                    }
+                   ssh2_pkt_adduint32(pktout, epf->sport);
+                   ssh2_pkt_send(ssh, pktout);
                }
+
+               del234(ssh->rportfwds, rpf);
+               free_rportfwd(rpf);
+           } else if (epf->local) {
+               pfd_terminate(epf->local);
            }
+
+           delpos234(ssh->portfwds, i);
+           free_portfwd(epf);
+           i--;                       /* so we don't skip one in the list */
        }
+
+    /*
+     * And finally, set up any new port forwardings (status==CREATE).
+     */
+    for (i = 0; (epf = index234(ssh->portfwds, i)) != NULL; i++)
+       if (epf->status == CREATE) {
+           char *sportdesc, *dportdesc;
+           sportdesc = dupprintf("%s%s%s%s%d%s",
+                                 epf->saddr ? epf->saddr : "",
+                                 epf->saddr ? ":" : "",
+                                 epf->sserv ? epf->sserv : "",
+                                 epf->sserv ? "(" : "",
+                                 epf->sport,
+                                 epf->sserv ? ")" : "");
+           if (epf->type == 'D') {
+               dportdesc = NULL;
+           } else {
+               dportdesc = dupprintf("%s:%s%s%d%s",
+                                     epf->daddr,
+                                     epf->dserv ? epf->dserv : "",
+                                     epf->dserv ? "(" : "",
+                                     epf->dport,
+                                     epf->dserv ? ")" : "");
+           }
+
+           if (epf->type == 'L') {
+               const char *err = pfd_addforward(epf->daddr, epf->dport,
+                                                epf->saddr, epf->sport,
+                                                ssh, &ssh->cfg,
+                                                &epf->local,
+                                                epf->addressfamily);
+
+               logeventf(ssh, "Local %sport %s forwarding to %s%s%s",
+                         epf->addressfamily == ADDRTYPE_IPV4 ? "IPv4 " :
+                         epf->addressfamily == ADDRTYPE_IPV6 ? "IPv6 " : "",
+                         sportdesc, dportdesc,
+                         err ? " failed: " : "", err ? err : "");
+           } else if (epf->type == 'D') {
+               const char *err = pfd_addforward(NULL, -1,
+                                                epf->saddr, epf->sport,
+                                                ssh, &ssh->cfg,
+                                                &epf->local,
+                                                epf->addressfamily);
+
+               logeventf(ssh, "Local %sport %s SOCKS dynamic forwarding%s%s",
+                         epf->addressfamily == ADDRTYPE_IPV4 ? "IPv4 " :
+                         epf->addressfamily == ADDRTYPE_IPV6 ? "IPv6 " : "",
+                         sportdesc,
+                         err ? " failed: " : "", err ? err : "");
+           } else {
+               struct ssh_rportfwd *pf;
+
+               /*
+                * Ensure the remote port forwardings tree exists.
+                */
+               if (!ssh->rportfwds) {
+                   if (ssh->version == 1)
+                       ssh->rportfwds = newtree234(ssh_rportcmp_ssh1);
+                   else
+                       ssh->rportfwds = newtree234(ssh_rportcmp_ssh2);
+               }
+
+               pf = snew(struct ssh_rportfwd);
+               strncpy(pf->dhost, epf->daddr, lenof(pf->dhost)-1);
+               pf->dhost[lenof(pf->dhost)-1] = '\0';
+               pf->dport = epf->dport;
+               pf->sport = epf->sport;
+               if (add234(ssh->rportfwds, pf) != pf) {
+                   logeventf(ssh, "Duplicate remote port forwarding to %s:%d",
+                             epf->daddr, epf->dport);
+                   sfree(pf);
+               } else {
+                   logeventf(ssh, "Requesting remote port %s"
+                             " forward to %s", sportdesc, dportdesc);
+
+                   pf->sportdesc = sportdesc;
+                   sportdesc = NULL;
+                   epf->remote = pf;
+                   pf->pfrec = epf;
+
+                   if (ssh->version == 1) {
+                       send_packet(ssh, SSH1_CMSG_PORT_FORWARD_REQUEST,
+                                   PKT_INT, epf->sport,
+                                   PKT_STR, epf->daddr,
+                                   PKT_INT, epf->dport,
+                                   PKT_END);
+                       ssh_queue_handler(ssh, SSH1_SMSG_SUCCESS,
+                                         SSH1_SMSG_FAILURE,
+                                         ssh_rportfwd_succfail, pf);
+                   } else {
+                       struct Packet *pktout;
+                       pktout = ssh2_pkt_init(SSH2_MSG_GLOBAL_REQUEST);
+                       ssh2_pkt_addstring(pktout, "tcpip-forward");
+                       ssh2_pkt_addbool(pktout, 1);/* want reply */
+                       if (epf->saddr) {
+                           ssh2_pkt_addstring(pktout, epf->saddr);
+                       } else if (ssh->cfg.rport_acceptall) {
+                           ssh2_pkt_addstring(pktout, "0.0.0.0");
+                       } else {
+                           ssh2_pkt_addstring(pktout, "127.0.0.1");
+                       }
+                       ssh2_pkt_adduint32(pktout, epf->sport);
+                       ssh2_pkt_send(ssh, pktout);
+
+                       ssh_queue_handler(ssh, SSH2_MSG_REQUEST_SUCCESS,
+                                         SSH2_MSG_REQUEST_FAILURE,
+                                         ssh_rportfwd_succfail, pf);
+                   }
+               }
+           }
+           sfree(sportdesc);
+           sfree(dportdesc);
+       }
+}
+
+static void ssh1_smsg_stdout_stderr_data(Ssh ssh, struct Packet *pktin)
+{
+    char *string;
+    int stringlen, bufsize;
+
+    ssh_pkt_getstring(pktin, &string, &stringlen);
+    if (string == NULL) {
+       bombout(("Incoming terminal data packet was badly formed"));
+       return;
+    }
+
+    bufsize = from_backend(ssh->frontend, pktin->type == SSH1_SMSG_STDERR_DATA,
+                          string, stringlen);
+    if (!ssh->v1_stdout_throttling && bufsize > SSH1_BUFFER_LIMIT) {
+       ssh->v1_stdout_throttling = 1;
+       ssh1_throttle(ssh, +1);
+    }
+}
+
+static void ssh1_smsg_x11_open(Ssh ssh, struct Packet *pktin)
+{
+    /* Remote side is trying to open a channel to talk to our
+     * X-Server. Give them back a local channel number. */
+    struct ssh_channel *c;
+    int remoteid = ssh_pkt_getuint32(pktin);
+
+    logevent("Received X11 connect request");
+    /* Refuse if X11 forwarding is disabled. */
+    if (!ssh->X11_fwd_enabled) {
+       send_packet(ssh, SSH1_MSG_CHANNEL_OPEN_FAILURE,
+                   PKT_INT, remoteid, PKT_END);
+       logevent("Rejected X11 connect request");
+    } else {
+       c = snew(struct ssh_channel);
+       c->ssh = ssh;
+
+       if (x11_init(&c->u.x11.s, ssh->cfg.x11_display, c,
+                    ssh->x11auth, NULL, -1, &ssh->cfg) != NULL) {
+           logevent("Opening X11 forward connection failed");
+           sfree(c);
+           send_packet(ssh, SSH1_MSG_CHANNEL_OPEN_FAILURE,
+                       PKT_INT, remoteid, PKT_END);
+       } else {
+           logevent
+               ("Opening X11 forward connection succeeded");
+           c->remoteid = remoteid;
+           c->localid = alloc_channel_id(ssh);
+           c->closes = 0;
+           c->v.v1.throttling = 0;
+           c->type = CHAN_X11; /* identify channel type */
+           add234(ssh->channels, c);
+           send_packet(ssh, SSH1_MSG_CHANNEL_OPEN_CONFIRMATION,
+                       PKT_INT, c->remoteid, PKT_INT,
+                       c->localid, PKT_END);
+           logevent("Opened X11 forward channel");
+       }
+    }
+}
+
+static void ssh1_smsg_agent_open(Ssh ssh, struct Packet *pktin)
+{
+    /* Remote side is trying to open a channel to talk to our
+     * agent. Give them back a local channel number. */
+    struct ssh_channel *c;
+    int remoteid = ssh_pkt_getuint32(pktin);
+
+    /* Refuse if agent forwarding is disabled. */
+    if (!ssh->agentfwd_enabled) {
+       send_packet(ssh, SSH1_MSG_CHANNEL_OPEN_FAILURE,
+                   PKT_INT, remoteid, PKT_END);
+    } else {
+       c = snew(struct ssh_channel);
+       c->ssh = ssh;
+       c->remoteid = remoteid;
+       c->localid = alloc_channel_id(ssh);
+       c->closes = 0;
+       c->v.v1.throttling = 0;
+       c->type = CHAN_AGENT;   /* identify channel type */
+       c->u.a.lensofar = 0;
+       add234(ssh->channels, c);
+       send_packet(ssh, SSH1_MSG_CHANNEL_OPEN_CONFIRMATION,
+                   PKT_INT, c->remoteid, PKT_INT, c->localid,
+                   PKT_END);
+    }
+}
+
+static void ssh1_msg_port_open(Ssh ssh, struct Packet *pktin)
+{
+    /* Remote side is trying to open a channel to talk to a
+     * forwarded port. Give them back a local channel number. */
+    struct ssh_channel *c;
+    struct ssh_rportfwd pf, *pfp;
+    int remoteid;
+    int hostsize, port;
+    char *host, buf[1024];
+    const char *e;
+    c = snew(struct ssh_channel);
+    c->ssh = ssh;
+
+    remoteid = ssh_pkt_getuint32(pktin);
+    ssh_pkt_getstring(pktin, &host, &hostsize);
+    port = ssh_pkt_getuint32(pktin);
+
+    if (hostsize >= lenof(pf.dhost))
+       hostsize = lenof(pf.dhost)-1;
+    memcpy(pf.dhost, host, hostsize);
+    pf.dhost[hostsize] = '\0';
+    pf.dport = port;
+    pfp = find234(ssh->rportfwds, &pf, NULL);
+
+    if (pfp == NULL) {
+       sprintf(buf, "Rejected remote port open request for %s:%d",
+               pf.dhost, port);
+       logevent(buf);
+       send_packet(ssh, SSH1_MSG_CHANNEL_OPEN_FAILURE,
+                   PKT_INT, remoteid, PKT_END);
+    } else {
+       sprintf(buf, "Received remote port open request for %s:%d",
+               pf.dhost, port);
+       logevent(buf);
+       e = pfd_newconnect(&c->u.pfd.s, pf.dhost, port,
+                          c, &ssh->cfg, pfp->pfrec->addressfamily);
+       if (e != NULL) {
+           char buf[256];
+           sprintf(buf, "Port open failed: %s", e);
+           logevent(buf);
+           sfree(c);
+           send_packet(ssh, SSH1_MSG_CHANNEL_OPEN_FAILURE,
+                       PKT_INT, remoteid, PKT_END);
+       } else {
+           c->remoteid = remoteid;
+           c->localid = alloc_channel_id(ssh);
+           c->closes = 0;
+           c->v.v1.throttling = 0;
+           c->type = CHAN_SOCKDATA;    /* identify channel type */
+           add234(ssh->channels, c);
+           send_packet(ssh, SSH1_MSG_CHANNEL_OPEN_CONFIRMATION,
+                       PKT_INT, c->remoteid, PKT_INT,
+                       c->localid, PKT_END);
+           logevent("Forwarded port opened successfully");
+       }
+    }
+}
+
+static void ssh1_msg_channel_open_confirmation(Ssh ssh, struct Packet *pktin)
+{
+    unsigned int remoteid = ssh_pkt_getuint32(pktin);
+    unsigned int localid = ssh_pkt_getuint32(pktin);
+    struct ssh_channel *c;
+
+    c = find234(ssh->channels, &remoteid, ssh_channelfind);
+    if (c && c->type == CHAN_SOCKDATA_DORMANT) {
+       c->remoteid = localid;
+       c->type = CHAN_SOCKDATA;
+       c->v.v1.throttling = 0;
+       pfd_confirm(c->u.pfd.s);
+    }
+
+    if (c && c->closes) {
+       /*
+        * We have a pending close on this channel,
+        * which we decided on before the server acked
+        * the channel open. So now we know the
+        * remoteid, we can close it again.
+        */
+       send_packet(ssh, SSH1_MSG_CHANNEL_CLOSE,
+                   PKT_INT, c->remoteid, PKT_END);
+    }
+}
+
+static void ssh1_msg_channel_open_failure(Ssh ssh, struct Packet *pktin)
+{
+    unsigned int remoteid = ssh_pkt_getuint32(pktin);
+    struct ssh_channel *c;
+
+    c = find234(ssh->channels, &remoteid, ssh_channelfind);
+    if (c && c->type == CHAN_SOCKDATA_DORMANT) {
+       logevent("Forwarded connection refused by server");
+       pfd_close(c->u.pfd.s);
+       del234(ssh->channels, c);
+       sfree(c);
+    }
+}
+
+static void ssh1_msg_channel_close(Ssh ssh, struct Packet *pktin)
+{
+    /* Remote side closes a channel. */
+    unsigned i = ssh_pkt_getuint32(pktin);
+    struct ssh_channel *c;
+    c = find234(ssh->channels, &i, ssh_channelfind);
+    if (c && ((int)c->remoteid) != -1) {
+       int closetype;
+       closetype =
+           (pktin->type == SSH1_MSG_CHANNEL_CLOSE ? 1 : 2);
+
+       if ((c->closes == 0) && (c->type == CHAN_X11)) {
+           logevent("Forwarded X11 connection terminated");
+           assert(c->u.x11.s != NULL);
+           x11_close(c->u.x11.s);
+           c->u.x11.s = NULL;
+       }
+       if ((c->closes == 0) && (c->type == CHAN_SOCKDATA)) {
+           logevent("Forwarded port closed");
+           assert(c->u.pfd.s != NULL);
+           pfd_close(c->u.pfd.s);
+           c->u.pfd.s = NULL;
+       }
+
+       c->closes |= (closetype << 2);   /* seen this message */
+       if (!(c->closes & closetype)) {
+           send_packet(ssh, pktin->type, PKT_INT, c->remoteid,
+                       PKT_END);
+           c->closes |= closetype;      /* sent it too */
+       }
+
+       if (c->closes == 15) {
+           del234(ssh->channels, c);
+           sfree(c);
+       }
+    } else {
+       bombout(("Received CHANNEL_CLOSE%s for %s channel %d\n",
+                pktin->type == SSH1_MSG_CHANNEL_CLOSE ? "" :
+                "_CONFIRMATION", c ? "half-open" : "nonexistent",
+                i));
     }
+}
+
+static void ssh1_msg_channel_data(Ssh ssh, struct Packet *pktin)
+{
+    /* Data sent down one of our channels. */
+    int i = ssh_pkt_getuint32(pktin);
+    char *p;
+    unsigned int len;
+    struct ssh_channel *c;
+
+    ssh_pkt_getstring(pktin, &p, &len);
 
-    if (!cfg.nopty) {
-       send_packet(SSH1_CMSG_REQUEST_PTY,
-                   PKT_STR, cfg.termtype,
-                   PKT_INT, rows, PKT_INT, cols,
-                   PKT_INT, 0, PKT_INT, 0, PKT_CHAR, 0, PKT_END);
-       ssh_state = SSH_STATE_INTERMED;
+    c = find234(ssh->channels, &i, ssh_channelfind);
+    if (c) {
+       int bufsize = 0;
+       switch (c->type) {
+         case CHAN_X11:
+           bufsize = x11_send(c->u.x11.s, p, len);
+           break;
+         case CHAN_SOCKDATA:
+           bufsize = pfd_send(c->u.pfd.s, p, len);
+           break;
+         case CHAN_AGENT:
+           /* Data for an agent message. Buffer it. */
+           while (len > 0) {
+               if (c->u.a.lensofar < 4) {
+                   unsigned int l = min(4 - c->u.a.lensofar, len);
+                   memcpy(c->u.a.msglen + c->u.a.lensofar, p,
+                          l);
+                   p += l;
+                   len -= l;
+                   c->u.a.lensofar += l;
+               }
+               if (c->u.a.lensofar == 4) {
+                   c->u.a.totallen =
+                       4 + GET_32BIT(c->u.a.msglen);
+                   c->u.a.message = snewn(c->u.a.totallen,
+                                          unsigned char);
+                   memcpy(c->u.a.message, c->u.a.msglen, 4);
+               }
+               if (c->u.a.lensofar >= 4 && len > 0) {
+                   unsigned int l =
+                       min(c->u.a.totallen - c->u.a.lensofar,
+                           len);
+                   memcpy(c->u.a.message + c->u.a.lensofar, p,
+                          l);
+                   p += l;
+                   len -= l;
+                   c->u.a.lensofar += l;
+               }
+               if (c->u.a.lensofar == c->u.a.totallen) {
+                   void *reply;
+                   int replylen;
+                   if (agent_query(c->u.a.message,
+                                   c->u.a.totallen,
+                                   &reply, &replylen,
+                                   ssh_agentf_callback, c))
+                       ssh_agentf_callback(c, reply, replylen);
+                   sfree(c->u.a.message);
+                   c->u.a.lensofar = 0;
+               }
+           }
+           bufsize = 0;   /* agent channels never back up */
+           break;
+       }
+       if (!c->v.v1.throttling && bufsize > SSH1_BUFFER_LIMIT) {
+           c->v.v1.throttling = 1;
+           ssh1_throttle(ssh, +1);
+       }
+    }
+}
+
+static void ssh1_smsg_exit_status(Ssh ssh, struct Packet *pktin)
+{
+    char buf[100];
+    ssh->exitcode = ssh_pkt_getuint32(pktin);
+    sprintf(buf, "Server sent command exit status %d",
+           ssh->exitcode);
+    logevent(buf);
+    send_packet(ssh, SSH1_CMSG_EXIT_CONFIRMATION, PKT_END);
+    /*
+     * In case `helpful' firewalls or proxies tack
+     * extra human-readable text on the end of the
+     * session which we might mistake for another
+     * encrypted packet, we close the session once
+     * we've sent EXIT_CONFIRMATION.
+     */
+    ssh->close_expected = TRUE;
+    ssh_closing((Plug)ssh, NULL, 0, 0);
+}
+
+static void do_ssh1_connection(Ssh ssh, unsigned char *in, int inlen,
+                              struct Packet *pktin)
+{
+    crBegin(ssh->do_ssh1_connection_crstate);
+
+    ssh->packet_dispatch[SSH1_SMSG_STDOUT_DATA] = 
+       ssh->packet_dispatch[SSH1_SMSG_STDERR_DATA] =
+       ssh1_smsg_stdout_stderr_data;
+
+    ssh->packet_dispatch[SSH1_MSG_CHANNEL_OPEN_CONFIRMATION] =
+       ssh1_msg_channel_open_confirmation;
+    ssh->packet_dispatch[SSH1_MSG_CHANNEL_OPEN_FAILURE] =
+       ssh1_msg_channel_open_failure;
+    ssh->packet_dispatch[SSH1_MSG_CHANNEL_CLOSE] =
+       ssh->packet_dispatch[SSH1_MSG_CHANNEL_CLOSE_CONFIRMATION] =
+       ssh1_msg_channel_close;
+    ssh->packet_dispatch[SSH1_MSG_CHANNEL_DATA] = ssh1_msg_channel_data;
+    ssh->packet_dispatch[SSH1_SMSG_EXIT_STATUS] = ssh1_smsg_exit_status;
+
+    if (ssh->cfg.agentfwd && agent_exists()) {
+       logevent("Requesting agent forwarding");
+       send_packet(ssh, SSH1_CMSG_AGENT_REQUEST_FORWARDING, PKT_END);
+       do {
+           crReturnV;
+       } while (!pktin);
+       if (pktin->type != SSH1_SMSG_SUCCESS
+           && pktin->type != SSH1_SMSG_FAILURE) {
+           bombout(("Protocol confusion"));
+           crStopV;
+       } else if (pktin->type == SSH1_SMSG_FAILURE) {
+           logevent("Agent forwarding refused");
+       } else {
+           logevent("Agent forwarding enabled");
+           ssh->agentfwd_enabled = TRUE;
+           ssh->packet_dispatch[SSH1_SMSG_AGENT_OPEN] = ssh1_smsg_agent_open;
+       }
+    }
+
+    if (ssh->cfg.x11_forward) {
+       char proto[20], data[64];
+       logevent("Requesting X11 forwarding");
+       ssh->x11auth = x11_invent_auth(proto, sizeof(proto),
+                                      data, sizeof(data), ssh->cfg.x11_auth);
+        x11_get_real_auth(ssh->x11auth, ssh->cfg.x11_display);
+       if (ssh->v1_local_protoflags & SSH1_PROTOFLAG_SCREEN_NUMBER) {
+           send_packet(ssh, SSH1_CMSG_X11_REQUEST_FORWARDING,
+                       PKT_STR, proto, PKT_STR, data,
+                       PKT_INT, x11_get_screen_number(ssh->cfg.x11_display),
+                       PKT_END);
+       } else {
+           send_packet(ssh, SSH1_CMSG_X11_REQUEST_FORWARDING,
+                       PKT_STR, proto, PKT_STR, data, PKT_END);
+       }
        do {
            crReturnV;
-       } while (!ispkt);
-       if (pktin.type != SSH1_SMSG_SUCCESS
-           && pktin.type != SSH1_SMSG_FAILURE) {
+       } while (!pktin);
+       if (pktin->type != SSH1_SMSG_SUCCESS
+           && pktin->type != SSH1_SMSG_FAILURE) {
            bombout(("Protocol confusion"));
+           crStopV;
+       } else if (pktin->type == SSH1_SMSG_FAILURE) {
+           logevent("X11 forwarding refused");
+       } else {
+           logevent("X11 forwarding enabled");
+           ssh->X11_fwd_enabled = TRUE;
+           ssh->packet_dispatch[SSH1_SMSG_X11_OPEN] = ssh1_smsg_x11_open;
+       }
+    }
+
+    ssh_setup_portfwd(ssh, &ssh->cfg);
+    ssh->packet_dispatch[SSH1_MSG_PORT_OPEN] = ssh1_msg_port_open;
+
+    if (!ssh->cfg.nopty) {
+       /* Unpick the terminal-speed string. */
+       /* XXX perhaps we should allow no speeds to be sent. */
+       ssh->ospeed = 38400; ssh->ispeed = 38400; /* last-resort defaults */
+       sscanf(ssh->cfg.termspeed, "%d,%d", &ssh->ospeed, &ssh->ispeed);
+       /* Send the pty request. */
+       send_packet(ssh, SSH1_CMSG_REQUEST_PTY,
+                   PKT_STR, ssh->cfg.termtype,
+                   PKT_INT, ssh->term_height,
+                   PKT_INT, ssh->term_width,
+                   PKT_INT, 0, PKT_INT, 0, /* width,height in pixels */
+                   PKT_CHAR, 192, PKT_INT, ssh->ispeed, /* TTY_OP_ISPEED */
+                   PKT_CHAR, 193, PKT_INT, ssh->ospeed, /* TTY_OP_OSPEED */
+                   PKT_CHAR, 0, PKT_END);
+       ssh->state = SSH_STATE_INTERMED;
+       do {
            crReturnV;
-       } else if (pktin.type == SSH1_SMSG_FAILURE) {
-           c_write_str("Server refused to allocate pty\r\n");
-           ssh_editing = ssh_echoing = 1;
+       } while (!pktin);
+       if (pktin->type != SSH1_SMSG_SUCCESS
+           && pktin->type != SSH1_SMSG_FAILURE) {
+           bombout(("Protocol confusion"));
+           crStopV;
+       } else if (pktin->type == SSH1_SMSG_FAILURE) {
+           c_write_str(ssh, "Server refused to allocate pty\r\n");
+           ssh->editing = ssh->echoing = 1;
        }
-       logevent("Allocated pty");
+       logeventf(ssh, "Allocated pty (ospeed %dbps, ispeed %dbps)",
+                 ssh->ospeed, ssh->ispeed);
     } else {
-       ssh_editing = ssh_echoing = 1;
+       ssh->editing = ssh->echoing = 1;
     }
 
-    if (cfg.compression) {
-       send_packet(SSH1_CMSG_REQUEST_COMPRESSION, PKT_INT, 6, PKT_END);
+    if (ssh->cfg.compression) {
+       send_packet(ssh, SSH1_CMSG_REQUEST_COMPRESSION, PKT_INT, 6, PKT_END);
        do {
            crReturnV;
-       } while (!ispkt);
-       if (pktin.type != SSH1_SMSG_SUCCESS
-           && pktin.type != SSH1_SMSG_FAILURE) {
+       } while (!pktin);
+       if (pktin->type != SSH1_SMSG_SUCCESS
+           && pktin->type != SSH1_SMSG_FAILURE) {
            bombout(("Protocol confusion"));
-           crReturnV;
-       } else if (pktin.type == SSH1_SMSG_FAILURE) {
-           c_write_str("Server refused to compress\r\n");
+           crStopV;
+       } else if (pktin->type == SSH1_SMSG_FAILURE) {
+           c_write_str(ssh, "Server refused to compress\r\n");
        }
        logevent("Started compression");
-       ssh1_compressing = TRUE;
-       zlib_compress_init();
-       zlib_decompress_init();
+       ssh->v1_compressing = TRUE;
+       ssh->cs_comp_ctx = zlib_compress_init();
+       logevent("Initialised zlib (RFC1950) compression");
+       ssh->sc_comp_ctx = zlib_decompress_init();
+       logevent("Initialised zlib (RFC1950) decompression");
     }
 
     /*
@@ -3118,330 +4486,54 @@ static void ssh1_protocol(unsigned char *in, int inlen, int ispkt)
      * exists, we fall straight back to that.
      */
     {
-       char *cmd = cfg.remote_cmd_ptr;
+       char *cmd = ssh->cfg.remote_cmd_ptr;
        
-       if (cfg.ssh_subsys && cfg.remote_cmd_ptr2) {
-           cmd = cfg.remote_cmd_ptr2;
-           ssh_fallback_cmd = TRUE;
+       if (ssh->cfg.ssh_subsys && ssh->cfg.remote_cmd_ptr2) {
+           cmd = ssh->cfg.remote_cmd_ptr2;
+           ssh->fallback_cmd = TRUE;
        }
        if (*cmd)
-           send_packet(SSH1_CMSG_EXEC_CMD, PKT_STR, cmd, PKT_END);
+           send_packet(ssh, SSH1_CMSG_EXEC_CMD, PKT_STR, cmd, PKT_END);
        else
-           send_packet(SSH1_CMSG_EXEC_SHELL, PKT_END);
+           send_packet(ssh, SSH1_CMSG_EXEC_SHELL, PKT_END);
        logevent("Started session");
     }
 
-    ssh_state = SSH_STATE_SESSION;
-    if (size_needed)
-       ssh_size();
-    if (eof_needed)
-       ssh_special(TS_EOF);
+    ssh->state = SSH_STATE_SESSION;
+    if (ssh->size_needed)
+       ssh_size(ssh, ssh->term_width, ssh->term_height);
+    if (ssh->eof_needed)
+       ssh_special(ssh, TS_EOF);
 
-    ldisc_send(NULL, 0, 0);           /* cause ldisc to notice changes */
-    ssh_send_ok = 1;
-    ssh_channels = newtree234(ssh_channelcmp);
+    if (ssh->ldisc)
+       ldisc_send(ssh->ldisc, NULL, 0, 0);/* cause ldisc to notice changes */
+    ssh->send_ok = 1;
+    ssh->channels = newtree234(ssh_channelcmp);
     while (1) {
-       crReturnV;
-       if (ispkt) {
-           if (pktin.type == SSH1_SMSG_STDOUT_DATA ||
-               pktin.type == SSH1_SMSG_STDERR_DATA) {
-               long len = GET_32BIT(pktin.body);
-               int bufsize =
-                   from_backend(pktin.type == SSH1_SMSG_STDERR_DATA,
-                                pktin.body + 4, len);
-               if (!ssh1_stdout_throttling && bufsize > SSH1_BUFFER_LIMIT) {
-                   ssh1_stdout_throttling = 1;
-                   ssh1_throttle(+1);
-               }
-           } else if (pktin.type == SSH1_MSG_DISCONNECT) {
-               ssh_state = SSH_STATE_CLOSED;
-               logevent("Received disconnect request");
-               crReturnV;
-           } else if (pktin.type == SSH1_SMSG_X11_OPEN) {
-               /* Remote side is trying to open a channel to talk to our
-                * X-Server. Give them back a local channel number. */
-               struct ssh_channel *c;
-
-               logevent("Received X11 connect request");
-               /* Refuse if X11 forwarding is disabled. */
-               if (!ssh_X11_fwd_enabled) {
-                   send_packet(SSH1_MSG_CHANNEL_OPEN_FAILURE,
-                               PKT_INT, GET_32BIT(pktin.body), PKT_END);
-                   logevent("Rejected X11 connect request");
-               } else {
-                   c = smalloc(sizeof(struct ssh_channel));
 
-                   if (x11_init(&c->u.x11.s, cfg.x11_display, c) != NULL) {
-                       logevent("opening X11 forward connection failed");
-                       sfree(c);
-                       send_packet(SSH1_MSG_CHANNEL_OPEN_FAILURE,
-                                   PKT_INT, GET_32BIT(pktin.body),
-                                   PKT_END);
-                   } else {
-                       logevent
-                           ("opening X11 forward connection succeeded");
-                       c->remoteid = GET_32BIT(pktin.body);
-                       c->localid = alloc_channel_id();
-                       c->closes = 0;
-                       c->v.v1.throttling = 0;
-                       c->type = CHAN_X11;     /* identify channel type */
-                       add234(ssh_channels, c);
-                       send_packet(SSH1_MSG_CHANNEL_OPEN_CONFIRMATION,
-                                   PKT_INT, c->remoteid, PKT_INT,
-                                   c->localid, PKT_END);
-                       logevent("Opened X11 forward channel");
-                   }
-               }
-           } else if (pktin.type == SSH1_SMSG_AGENT_OPEN) {
-               /* Remote side is trying to open a channel to talk to our
-                * agent. Give them back a local channel number. */
-               struct ssh_channel *c;
-
-               /* Refuse if agent forwarding is disabled. */
-               if (!ssh_agentfwd_enabled) {
-                   send_packet(SSH1_MSG_CHANNEL_OPEN_FAILURE,
-                               PKT_INT, GET_32BIT(pktin.body), PKT_END);
-               } else {
-                   c = smalloc(sizeof(struct ssh_channel));
-                   c->remoteid = GET_32BIT(pktin.body);
-                   c->localid = alloc_channel_id();
-                   c->closes = 0;
-                   c->v.v1.throttling = 0;
-                   c->type = CHAN_AGENT;       /* identify channel type */
-                   c->u.a.lensofar = 0;
-                   add234(ssh_channels, c);
-                   send_packet(SSH1_MSG_CHANNEL_OPEN_CONFIRMATION,
-                               PKT_INT, c->remoteid, PKT_INT, c->localid,
-                               PKT_END);
-               }
-           } else if (pktin.type == SSH1_MSG_PORT_OPEN) {
-               /* Remote side is trying to open a channel to talk to a
-                * forwarded port. Give them back a local channel number. */
-               struct ssh_channel *c;
-               struct ssh_rportfwd pf;
-               int hostsize, port;
-               char host[256], buf[1024];
-               char *p, *h, *e;
-               c = smalloc(sizeof(struct ssh_channel));
-
-               hostsize = GET_32BIT(pktin.body+4);
-               for(h = host, p = pktin.body+8; hostsize != 0; hostsize--) {
-                   if (h+1 < host+sizeof(host))
-                       *h++ = *p;
-                   p++;
-               }
-               *h = 0;
-               port = GET_32BIT(p);
-
-               strcpy(pf.dhost, host);
-               pf.dport = port;
-
-               if (find234(ssh_rportfwds, &pf, NULL) == NULL) {
-                   sprintf(buf, "Rejected remote port open request for %s:%d",
-                           host, port);
-                   logevent(buf);
-                    send_packet(SSH1_MSG_CHANNEL_OPEN_FAILURE,
-                                PKT_INT, GET_32BIT(pktin.body), PKT_END);
-               } else {
-                   sprintf(buf, "Received remote port open request for %s:%d",
-                           host, port);
-                   logevent(buf);
-                   e = pfd_newconnect(&c->u.pfd.s, host, port, c);
-                   if (e != NULL) {
-                       char buf[256];
-                       sprintf(buf, "Port open failed: %s", e);
-                       logevent(buf);
-                       sfree(c);
-                       send_packet(SSH1_MSG_CHANNEL_OPEN_FAILURE,
-                                   PKT_INT, GET_32BIT(pktin.body),
-                                   PKT_END);
-                   } else {
-                       c->remoteid = GET_32BIT(pktin.body);
-                       c->localid = alloc_channel_id();
-                       c->closes = 0;
-                       c->v.v1.throttling = 0;
-                       c->type = CHAN_SOCKDATA;        /* identify channel type */
-                       add234(ssh_channels, c);
-                       send_packet(SSH1_MSG_CHANNEL_OPEN_CONFIRMATION,
-                                   PKT_INT, c->remoteid, PKT_INT,
-                                   c->localid, PKT_END);
-                       logevent("Forwarded port opened successfully");
-                   }
-               }
-
-           } else if (pktin.type == SSH1_MSG_CHANNEL_OPEN_CONFIRMATION) {
-               unsigned int remoteid = GET_32BIT(pktin.body);
-               unsigned int localid = GET_32BIT(pktin.body+4);
-               struct ssh_channel *c;
-
-               c = find234(ssh_channels, &remoteid, ssh_channelfind);
-               if (c && c->type == CHAN_SOCKDATA_DORMANT) {
-                   c->remoteid = localid;
-                   c->type = CHAN_SOCKDATA;
-                   c->v.v1.throttling = 0;
-                   pfd_confirm(c->u.pfd.s);
-               }
-
-               if (c && c->closes) {
-                   /*
-                    * We have a pending close on this channel,
-                    * which we decided on before the server acked
-                    * the channel open. So now we know the
-                    * remoteid, we can close it again.
-                    */
-                   send_packet(SSH1_MSG_CHANNEL_CLOSE, PKT_INT, c->remoteid,
-                               PKT_END);
-               }
-
-           } else if (pktin.type == SSH1_MSG_CHANNEL_OPEN_FAILURE) {
-               unsigned int remoteid = GET_32BIT(pktin.body);
-               unsigned int localid = GET_32BIT(pktin.body+4);
-               struct ssh_channel *c;
-
-               c = find234(ssh_channels, &remoteid, ssh_channelfind);
-               if (c && c->type == CHAN_SOCKDATA_DORMANT) {
-                   logevent("Forwarded connection refused by server");
-                   pfd_close(c->u.pfd.s);
-                   del234(ssh_channels, c);
-                   sfree(c);
-               }
+       /*
+        * By this point, most incoming packets are already being
+        * handled by the dispatch table, and we need only pay
+        * attention to the unusual ones.
+        */
 
-           } else if (pktin.type == SSH1_MSG_CHANNEL_CLOSE ||
-                      pktin.type == SSH1_MSG_CHANNEL_CLOSE_CONFIRMATION) {
-               /* Remote side closes a channel. */
-               unsigned i = GET_32BIT(pktin.body);
-               struct ssh_channel *c;
-               c = find234(ssh_channels, &i, ssh_channelfind);
-               if (c) {
-                   int closetype;
-                   closetype =
-                       (pktin.type == SSH1_MSG_CHANNEL_CLOSE ? 1 : 2);
-                   if (!(c->closes & closetype))
-                       send_packet(pktin.type, PKT_INT, c->remoteid,
-                                   PKT_END);
-                   if ((c->closes == 0) && (c->type == CHAN_X11)) {
-                       logevent("Forwarded X11 connection terminated");
-                       assert(c->u.x11.s != NULL);
-                       x11_close(c->u.x11.s);
-                       c->u.x11.s = NULL;
-                   }
-                   if ((c->closes == 0) && (c->type == CHAN_SOCKDATA)) {
-                       logevent("Forwarded port closed");
-                       assert(c->u.pfd.s != NULL);
-                       pfd_close(c->u.pfd.s);
-                       c->u.pfd.s = NULL;
-                   }
-                   c->closes |= closetype;
-                   if (c->closes == 3) {
-                       del234(ssh_channels, c);
-                       sfree(c);
-                   }
-               }
-           } else if (pktin.type == SSH1_MSG_CHANNEL_DATA) {
-               /* Data sent down one of our channels. */
-               int i = GET_32BIT(pktin.body);
-               int len = GET_32BIT(pktin.body + 4);
-               unsigned char *p = pktin.body + 8;
-               struct ssh_channel *c;
-               c = find234(ssh_channels, &i, ssh_channelfind);
-               if (c) {
-                   int bufsize;
-                   switch (c->type) {
-                     case CHAN_X11:
-                       bufsize = x11_send(c->u.x11.s, p, len);
-                       break;
-                     case CHAN_SOCKDATA:
-                       bufsize = pfd_send(c->u.pfd.s, p, len);
-                       break;
-                     case CHAN_AGENT:
-                       /* Data for an agent message. Buffer it. */
-                       while (len > 0) {
-                           if (c->u.a.lensofar < 4) {
-                               int l = min(4 - c->u.a.lensofar, len);
-                               memcpy(c->u.a.msglen + c->u.a.lensofar, p,
-                                      l);
-                               p += l;
-                               len -= l;
-                               c->u.a.lensofar += l;
-                           }
-                           if (c->u.a.lensofar == 4) {
-                               c->u.a.totallen =
-                                   4 + GET_32BIT(c->u.a.msglen);
-                               c->u.a.message = smalloc(c->u.a.totallen);
-                               memcpy(c->u.a.message, c->u.a.msglen, 4);
-                           }
-                           if (c->u.a.lensofar >= 4 && len > 0) {
-                               int l =
-                                   min(c->u.a.totallen - c->u.a.lensofar,
-                                       len);
-                               memcpy(c->u.a.message + c->u.a.lensofar, p,
-                                      l);
-                               p += l;
-                               len -= l;
-                               c->u.a.lensofar += l;
-                           }
-                           if (c->u.a.lensofar == c->u.a.totallen) {
-                               void *reply, *sentreply;
-                               int replylen;
-                               agent_query(c->u.a.message,
-                                           c->u.a.totallen, &reply,
-                                           &replylen);
-                               if (reply)
-                                   sentreply = reply;
-                               else {
-                                   /* Fake SSH_AGENT_FAILURE. */
-                                   sentreply = "\0\0\0\1\5";
-                                   replylen = 5;
-                               }
-                               send_packet(SSH1_MSG_CHANNEL_DATA,
-                                           PKT_INT, c->remoteid,
-                                           PKT_INT, replylen,
-                                           PKT_DATA, sentreply, replylen,
-                                           PKT_END);
-                               if (reply)
-                                   sfree(reply);
-                               sfree(c->u.a.message);
-                               c->u.a.lensofar = 0;
-                           }
-                       }
-                       bufsize = 0;   /* agent channels never back up */
-                       break;
-                   }
-                   if (!c->v.v1.throttling && bufsize > SSH1_BUFFER_LIMIT) {
-                       c->v.v1.throttling = 1;
-                       ssh1_throttle(+1);
-                   }
-               }
-           } else if (pktin.type == SSH1_SMSG_SUCCESS) {
+       crReturnV;
+       if (pktin) {
+           if (pktin->type == SSH1_SMSG_SUCCESS) {
                /* may be from EXEC_SHELL on some servers */
-           } else if (pktin.type == SSH1_SMSG_FAILURE) {
+           } else if (pktin->type == SSH1_SMSG_FAILURE) {
                /* may be from EXEC_SHELL on some servers
                 * if no pty is available or in other odd cases. Ignore */
-           } else if (pktin.type == SSH1_SMSG_EXIT_STATUS) {
-               char buf[100];
-               ssh_exitcode = GET_32BIT(pktin.body);
-               sprintf(buf, "Server sent command exit status %d",
-                       ssh_exitcode);
-               logevent(buf);
-               send_packet(SSH1_CMSG_EXIT_CONFIRMATION, PKT_END);
-                /*
-                 * In case `helpful' firewalls or proxies tack
-                 * extra human-readable text on the end of the
-                 * session which we might mistake for another
-                 * encrypted packet, we close the session once
-                 * we've sent EXIT_CONFIRMATION.
-                 */
-                ssh_state = SSH_STATE_CLOSED;
-                crReturnV;
            } else {
-               bombout(("Strange packet received: type %d", pktin.type));
-               crReturnV;
+               bombout(("Strange packet received: type %d", pktin->type));
+               crStopV;
            }
        } else {
            while (inlen > 0) {
                int len = min(inlen, 512);
-               send_packet(SSH1_CMSG_STDIN_DATA,
-                           PKT_INT, len, PKT_DATA, in, len, PKT_END);
+               send_packet(ssh, SSH1_CMSG_STDIN_DATA, PKTT_DATA,
+                           PKT_INT, len, PKT_DATA, in, len,
+                           PKTT_OTHER, PKT_END);
                in += len;
                inlen -= len;
            }
@@ -3452,11 +4544,82 @@ static void ssh1_protocol(unsigned char *in, int inlen, int ispkt)
 }
 
 /*
+ * Handle the top-level SSH2 protocol.
+ */
+static void ssh1_msg_debug(Ssh ssh, struct Packet *pktin)
+{
+    char *buf, *msg;
+    int msglen;
+
+    ssh_pkt_getstring(pktin, &msg, &msglen);
+    buf = dupprintf("Remote debug message: %.*s", msglen, msg);
+    logevent(buf);
+    sfree(buf);
+}
+
+static void ssh1_msg_disconnect(Ssh ssh, struct Packet *pktin)
+{
+    /* log reason code in disconnect message */
+    char *msg;
+    int msglen;
+
+    ssh_pkt_getstring(pktin, &msg, &msglen);
+    bombout(("Server sent disconnect message:\n\"%.*s\"", msglen, msg));
+}
+
+void ssh_msg_ignore(Ssh ssh, struct Packet *pktin)
+{
+    /* Do nothing, because we're ignoring it! Duhh. */
+}
+
+static void ssh1_protocol_setup(Ssh ssh)
+{
+    int i;
+
+    /*
+     * Most messages are handled by the coroutines.
+     */
+    for (i = 0; i < 256; i++)
+       ssh->packet_dispatch[i] = NULL;
+
+    /*
+     * These special message types we install handlers for.
+     */
+    ssh->packet_dispatch[SSH1_MSG_DISCONNECT] = ssh1_msg_disconnect;
+    ssh->packet_dispatch[SSH1_MSG_IGNORE] = ssh_msg_ignore;
+    ssh->packet_dispatch[SSH1_MSG_DEBUG] = ssh1_msg_debug;
+}
+
+static void ssh1_protocol(Ssh ssh, unsigned char *in, int inlen,
+                         struct Packet *pktin)
+{
+    if (ssh->state == SSH_STATE_CLOSED)
+       return;
+
+    if (pktin && ssh->packet_dispatch[pktin->type]) {
+       ssh->packet_dispatch[pktin->type](ssh, pktin);
+       return;
+    }
+
+    if (!ssh->protocol_initial_phase_done) {
+       if (do_ssh1_login(ssh, in, inlen, pktin))
+           ssh->protocol_initial_phase_done = TRUE;
+       else
+           return;
+    }
+
+    do_ssh1_connection(ssh, in, inlen, pktin);
+}
+
+/*
  * Utility routine for decoding comma-separated strings in KEXINIT.
  */
 static int in_commasep_string(char *needle, char *haystack, int haylen)
 {
-    int needlen = strlen(needle);
+    int needlen;
+    if (!needle || !haystack)         /* protect against null pointers */
+       return 0;
+    needlen = strlen(needle);
     while (1) {
        /*
         * Is it at the start of the string?
@@ -3482,20 +4645,23 @@ static int in_commasep_string(char *needle, char *haystack, int haylen)
 /*
  * SSH2 key creation method.
  */
-static void ssh2_mkkey(Bignum K, char *H, char *sessid, char chr,
-                      char *keyspace)
+static void ssh2_mkkey(Ssh ssh, Bignum K, unsigned char *H,
+                      unsigned char *sessid, char chr,
+                      unsigned char *keyspace)
 {
     SHA_State s;
     /* First 20 bytes. */
     SHA_Init(&s);
-    sha_mpint(&s, K);
+    if (!(ssh->remote_bugs & BUG_SSH2_DERIVEKEY))
+       sha_mpint(&s, K);
     SHA_Bytes(&s, H, 20);
     SHA_Bytes(&s, &chr, 1);
     SHA_Bytes(&s, sessid, 20);
     SHA_Final(&s, keyspace);
     /* Next 20 bytes. */
     SHA_Init(&s);
-    sha_mpint(&s, K);
+    if (!(ssh->remote_bugs & BUG_SSH2_DERIVEKEY))
+       sha_mpint(&s, K);
     SHA_Bytes(&s, H, 20);
     SHA_Bytes(&s, keyspace, 20);
     SHA_Final(&s, keyspace + 20);
@@ -3504,294 +4670,382 @@ static void ssh2_mkkey(Bignum K, char *H, char *sessid, char chr,
 /*
  * Handle the SSH2 transport layer.
  */
-static int do_ssh2_transport(unsigned char *in, int inlen, int ispkt)
-{
-    static int i, j, len, nbits, pbits, warn;
-    static char *str;
-    static Bignum p, g, e, f, K;
-    static int kex_init_value, kex_reply_value;
-    static const struct ssh_mac **maclist;
-    static int nmacs;
-    static const struct ssh2_cipher *cscipher_tobe = NULL;
-    static const struct ssh2_cipher *sccipher_tobe = NULL;
-    static const struct ssh_mac *csmac_tobe = NULL;
-    static const struct ssh_mac *scmac_tobe = NULL;
-    static const struct ssh_compress *cscomp_tobe = NULL;
-    static const struct ssh_compress *sccomp_tobe = NULL;
-    static char *hostkeydata, *sigdata, *keystr, *fingerprint;
-    static int hostkeylen, siglen;
-    static void *hkey;                /* actual host key */
-    static unsigned char exchange_hash[20];
-    static unsigned char keyspace[40];
-    static int n_preferred_ciphers;
-    static const struct ssh2_ciphers *preferred_ciphers[CIPHER_MAX];
-    static const struct ssh_compress *preferred_comp;
-    static int cipherstr_started;
-    static int first_kex;
-
-    crBegin;
-    random_init();
-    first_kex = 1;
+static int do_ssh2_transport(Ssh ssh, unsigned char *in, int inlen,
+                            struct Packet *pktin)
+{
+    struct do_ssh2_transport_state {
+       int nbits, pbits, warn;
+       Bignum p, g, e, f, K;
+       int kex_init_value, kex_reply_value;
+       const struct ssh_mac **maclist;
+       int nmacs;
+       const struct ssh2_cipher *cscipher_tobe;
+       const struct ssh2_cipher *sccipher_tobe;
+       const struct ssh_mac *csmac_tobe;
+       const struct ssh_mac *scmac_tobe;
+       const struct ssh_compress *cscomp_tobe;
+       const struct ssh_compress *sccomp_tobe;
+       char *hostkeydata, *sigdata, *keystr, *fingerprint;
+       int hostkeylen, siglen;
+       void *hkey;                    /* actual host key */
+       unsigned char exchange_hash[20];
+       int n_preferred_kex;
+       const struct ssh_kex *preferred_kex[KEX_MAX];
+       int n_preferred_ciphers;
+       const struct ssh2_ciphers *preferred_ciphers[CIPHER_MAX];
+       const struct ssh_compress *preferred_comp;
+       int got_session_id, activated_authconn;
+       struct Packet *pktout;
+    };
+    crState(do_ssh2_transport_state);
+
+    crBegin(ssh->do_ssh2_transport_crstate);
+
+    s->cscipher_tobe = s->sccipher_tobe = NULL;
+    s->csmac_tobe = s->scmac_tobe = NULL;
+    s->cscomp_tobe = s->sccomp_tobe = NULL;
+
+    s->got_session_id = s->activated_authconn = FALSE;
 
     /*
-     * Set up the preferred ciphers. (NULL => warn below here)
+     * Be prepared to work around the buggy MAC problem.
      */
-    n_preferred_ciphers = 0;
-    for (i = 0; i < CIPHER_MAX; i++) {
-       switch (cfg.ssh_cipherlist[i]) {
-         case CIPHER_BLOWFISH:
-           preferred_ciphers[n_preferred_ciphers] = &ssh2_blowfish;
-           n_preferred_ciphers++;
-           break;
-         case CIPHER_DES:
-           if (cfg.ssh2_des_cbc) {
-               preferred_ciphers[n_preferred_ciphers] = &ssh2_des;
-               n_preferred_ciphers++;
+    if (ssh->remote_bugs & BUG_SSH2_HMAC)
+       s->maclist = buggymacs, s->nmacs = lenof(buggymacs);
+    else
+       s->maclist = macs, s->nmacs = lenof(macs);
+
+  begin_key_exchange:
+    ssh->pkt_ctx &= ~SSH2_PKTCTX_KEX_MASK;
+    {
+       int i, j, commalist_started;
+
+       /*
+        * Set up the preferred key exchange. (NULL => warn below here)
+        */
+       s->n_preferred_kex = 0;
+       for (i = 0; i < KEX_MAX; i++) {
+           switch (ssh->cfg.ssh_kexlist[i]) {
+             case KEX_DHGEX:
+               s->preferred_kex[s->n_preferred_kex++] =
+                   &ssh_diffiehellman_gex;
+               break;
+             case KEX_DHGROUP14:
+               s->preferred_kex[s->n_preferred_kex++] =
+                   &ssh_diffiehellman_group14;
+               break;
+             case KEX_DHGROUP1:
+               s->preferred_kex[s->n_preferred_kex++] =
+                   &ssh_diffiehellman_group1;
+               break;
+             case CIPHER_WARN:
+               /* Flag for later. Don't bother if it's the last in
+                * the list. */
+               if (i < KEX_MAX - 1) {
+                   s->preferred_kex[s->n_preferred_kex++] = NULL;
+               }
+               break;
            }
-           break;
-         case CIPHER_3DES:
-           preferred_ciphers[n_preferred_ciphers] = &ssh2_3des;
-           n_preferred_ciphers++;
-           break;
-         case CIPHER_AES:
-           preferred_ciphers[n_preferred_ciphers] = &ssh2_aes;
-           n_preferred_ciphers++;
-           break;
-         case CIPHER_WARN:
-           /* Flag for later. Don't bother if it's the last in
-            * the list. */
-           if (i < CIPHER_MAX - 1) {
-               preferred_ciphers[n_preferred_ciphers] = NULL;
-               n_preferred_ciphers++;
+       }
+
+       /*
+        * Set up the preferred ciphers. (NULL => warn below here)
+        */
+       s->n_preferred_ciphers = 0;
+       for (i = 0; i < CIPHER_MAX; i++) {
+           switch (ssh->cfg.ssh_cipherlist[i]) {
+             case CIPHER_BLOWFISH:
+               s->preferred_ciphers[s->n_preferred_ciphers++] = &ssh2_blowfish;
+               break;
+             case CIPHER_DES:
+               if (ssh->cfg.ssh2_des_cbc) {
+                   s->preferred_ciphers[s->n_preferred_ciphers++] = &ssh2_des;
+               }
+               break;
+             case CIPHER_3DES:
+               s->preferred_ciphers[s->n_preferred_ciphers++] = &ssh2_3des;
+               break;
+             case CIPHER_AES:
+               s->preferred_ciphers[s->n_preferred_ciphers++] = &ssh2_aes;
+               break;
+             case CIPHER_WARN:
+               /* Flag for later. Don't bother if it's the last in
+                * the list. */
+               if (i < CIPHER_MAX - 1) {
+                   s->preferred_ciphers[s->n_preferred_ciphers++] = NULL;
+               }
+               break;
            }
-           break;
        }
-    }
 
-    /*
-     * Set up preferred compression.
-     */
-    if (cfg.compression)
-       preferred_comp = &ssh_zlib;
-    else
-       preferred_comp = &ssh_comp_none;
+       /*
+        * Set up preferred compression.
+        */
+       if (ssh->cfg.compression)
+           s->preferred_comp = &ssh_zlib;
+       else
+           s->preferred_comp = &ssh_comp_none;
 
-    /*
-     * Be prepared to work around the buggy MAC problem.
-     */
-    if (cfg.buggymac || (ssh_remote_bugs & BUG_SSH2_HMAC))
-       maclist = buggymacs, nmacs = lenof(buggymacs);
-    else
-       maclist = macs, nmacs = lenof(macs);
+       /*
+        * Enable queueing of outgoing auth- or connection-layer
+        * packets while we are in the middle of a key exchange.
+        */
+       ssh->queueing = TRUE;
 
-  begin_key_exchange:
-    /*
-     * Construct and send our key exchange packet.
-     */
-    ssh2_pkt_init(SSH2_MSG_KEXINIT);
-    for (i = 0; i < 16; i++)
-       ssh2_pkt_addbyte((unsigned char) random_byte());
-    /* List key exchange algorithms. */
-    ssh2_pkt_addstring_start();
-    for (i = 0; i < lenof(kex_algs); i++) {
-       ssh2_pkt_addstring_str(kex_algs[i]->name);
-       if (i < lenof(kex_algs) - 1)
-           ssh2_pkt_addstring_str(",");
-    }
-    /* List server host key algorithms. */
-    ssh2_pkt_addstring_start();
-    for (i = 0; i < lenof(hostkey_algs); i++) {
-       ssh2_pkt_addstring_str(hostkey_algs[i]->name);
-       if (i < lenof(hostkey_algs) - 1)
-           ssh2_pkt_addstring_str(",");
-    }
-    /* List client->server encryption algorithms. */
-    ssh2_pkt_addstring_start();
-    cipherstr_started = 0;
-    for (i = 0; i < n_preferred_ciphers; i++) {
-       const struct ssh2_ciphers *c = preferred_ciphers[i];
-       if (!c) continue;              /* warning flag */
-       for (j = 0; j < c->nciphers; j++) {
-           if (cipherstr_started)
-               ssh2_pkt_addstring_str(",");
-           ssh2_pkt_addstring_str(c->list[j]->name);
-           cipherstr_started = 1;
+       /*
+        * Flag that KEX is in progress.
+        */
+       ssh->kex_in_progress = TRUE;
+
+       /*
+        * Construct and send our key exchange packet.
+        */
+       s->pktout = ssh2_pkt_init(SSH2_MSG_KEXINIT);
+       for (i = 0; i < 16; i++)
+           ssh2_pkt_addbyte(s->pktout, (unsigned char) random_byte());
+       /* List key exchange algorithms. */
+       ssh2_pkt_addstring_start(s->pktout);
+       commalist_started = 0;
+       for (i = 0; i < s->n_preferred_kex; i++) {
+           const struct ssh_kex *k = s->preferred_kex[i];
+           if (!k) continue;          /* warning flag */
+           if (commalist_started)
+               ssh2_pkt_addstring_str(s->pktout, ",");
+           ssh2_pkt_addstring_str(s->pktout, s->preferred_kex[i]->name);
+           commalist_started = 1;
        }
-    }
-    /* List server->client encryption algorithms. */
-    ssh2_pkt_addstring_start();
-    cipherstr_started = 0;
-    for (i = 0; i < n_preferred_ciphers; i++) {
-       const struct ssh2_ciphers *c = preferred_ciphers[i];
-       if (!c) continue; /* warning flag */
-       for (j = 0; j < c->nciphers; j++) {
-           if (cipherstr_started)
-               ssh2_pkt_addstring_str(",");
-           ssh2_pkt_addstring_str(c->list[j]->name);
-           cipherstr_started = 1;
+       /* List server host key algorithms. */
+       ssh2_pkt_addstring_start(s->pktout);
+       for (i = 0; i < lenof(hostkey_algs); i++) {
+           ssh2_pkt_addstring_str(s->pktout, hostkey_algs[i]->name);
+           if (i < lenof(hostkey_algs) - 1)
+               ssh2_pkt_addstring_str(s->pktout, ",");
+       }
+       /* List client->server encryption algorithms. */
+       ssh2_pkt_addstring_start(s->pktout);
+       commalist_started = 0;
+       for (i = 0; i < s->n_preferred_ciphers; i++) {
+           const struct ssh2_ciphers *c = s->preferred_ciphers[i];
+           if (!c) continue;          /* warning flag */
+           for (j = 0; j < c->nciphers; j++) {
+               if (commalist_started)
+                   ssh2_pkt_addstring_str(s->pktout, ",");
+               ssh2_pkt_addstring_str(s->pktout, c->list[j]->name);
+               commalist_started = 1;
+           }
+       }
+       /* List server->client encryption algorithms. */
+       ssh2_pkt_addstring_start(s->pktout);
+       commalist_started = 0;
+       for (i = 0; i < s->n_preferred_ciphers; i++) {
+           const struct ssh2_ciphers *c = s->preferred_ciphers[i];
+           if (!c) continue; /* warning flag */
+           for (j = 0; j < c->nciphers; j++) {
+               if (commalist_started)
+                   ssh2_pkt_addstring_str(s->pktout, ",");
+               ssh2_pkt_addstring_str(s->pktout, c->list[j]->name);
+               commalist_started = 1;
+           }
+       }
+       /* List client->server MAC algorithms. */
+       ssh2_pkt_addstring_start(s->pktout);
+       for (i = 0; i < s->nmacs; i++) {
+           ssh2_pkt_addstring_str(s->pktout, s->maclist[i]->name);
+           if (i < s->nmacs - 1)
+               ssh2_pkt_addstring_str(s->pktout, ",");
+       }
+       /* List server->client MAC algorithms. */
+       ssh2_pkt_addstring_start(s->pktout);
+       for (i = 0; i < s->nmacs; i++) {
+           ssh2_pkt_addstring_str(s->pktout, s->maclist[i]->name);
+           if (i < s->nmacs - 1)
+               ssh2_pkt_addstring_str(s->pktout, ",");
+       }
+       /* List client->server compression algorithms. */
+       ssh2_pkt_addstring_start(s->pktout);
+       assert(lenof(compressions) > 1);
+       ssh2_pkt_addstring_str(s->pktout, s->preferred_comp->name);
+       for (i = 0; i < lenof(compressions); i++) {
+           const struct ssh_compress *c = compressions[i];
+           if (c != s->preferred_comp) {
+               ssh2_pkt_addstring_str(s->pktout, ",");
+               ssh2_pkt_addstring_str(s->pktout, c->name);
+           }
+       }
+       /* List server->client compression algorithms. */
+       ssh2_pkt_addstring_start(s->pktout);
+       assert(lenof(compressions) > 1);
+       ssh2_pkt_addstring_str(s->pktout, s->preferred_comp->name);
+       for (i = 0; i < lenof(compressions); i++) {
+           const struct ssh_compress *c = compressions[i];
+           if (c != s->preferred_comp) {
+               ssh2_pkt_addstring_str(s->pktout, ",");
+               ssh2_pkt_addstring_str(s->pktout, c->name);
+           }
        }
+       /* List client->server languages. Empty list. */
+       ssh2_pkt_addstring_start(s->pktout);
+       /* List server->client languages. Empty list. */
+       ssh2_pkt_addstring_start(s->pktout);
+       /* First KEX packet does _not_ follow, because we're not that brave. */
+       ssh2_pkt_addbool(s->pktout, FALSE);
+       /* Reserved. */
+       ssh2_pkt_adduint32(s->pktout, 0);
     }
-    /* List client->server MAC algorithms. */
-    ssh2_pkt_addstring_start();
-    for (i = 0; i < nmacs; i++) {
-       ssh2_pkt_addstring_str(maclist[i]->name);
-       if (i < nmacs - 1)
-           ssh2_pkt_addstring_str(",");
-    }
-    /* List server->client MAC algorithms. */
-    ssh2_pkt_addstring_start();
-    for (i = 0; i < nmacs; i++) {
-       ssh2_pkt_addstring_str(maclist[i]->name);
-       if (i < nmacs - 1)
-           ssh2_pkt_addstring_str(",");
-    }
-    /* List client->server compression algorithms. */
-    ssh2_pkt_addstring_start();
-    for (i = 0; i < lenof(compressions) + 1; i++) {
-       const struct ssh_compress *c =
-           i == 0 ? preferred_comp : compressions[i - 1];
-       ssh2_pkt_addstring_str(c->name);
-       if (i < lenof(compressions))
-           ssh2_pkt_addstring_str(",");
-    }
-    /* List server->client compression algorithms. */
-    ssh2_pkt_addstring_start();
-    for (i = 0; i < lenof(compressions) + 1; i++) {
-       const struct ssh_compress *c =
-           i == 0 ? preferred_comp : compressions[i - 1];
-       ssh2_pkt_addstring_str(c->name);
-       if (i < lenof(compressions))
-           ssh2_pkt_addstring_str(",");
-    }
-    /* List client->server languages. Empty list. */
-    ssh2_pkt_addstring_start();
-    /* List server->client languages. Empty list. */
-    ssh2_pkt_addstring_start();
-    /* First KEX packet does _not_ follow, because we're not that brave. */
-    ssh2_pkt_addbool(FALSE);
-    /* Reserved. */
-    ssh2_pkt_adduint32(0);
-
-    exhash = exhashbase;
-    sha_string(&exhash, pktout.data + 5, pktout.length - 5);
-
-    ssh2_pkt_send();
-
-    if (!ispkt)
-       crWaitUntil(ispkt);
-    sha_string(&exhash, pktin.data + 5, pktin.length - 5);
+
+    ssh->exhash = ssh->exhashbase;
+    sha_string(&ssh->exhash, s->pktout->data + 5, s->pktout->length - 5);
+
+    ssh2_pkt_send_noqueue(ssh, s->pktout);
+
+    if (!pktin)
+       crWaitUntil(pktin);
+    if (pktin->length > 5)
+       sha_string(&ssh->exhash, pktin->data + 5, pktin->length - 5);
 
     /*
      * Now examine the other side's KEXINIT to see what we're up
      * to.
      */
-    if (pktin.type != SSH2_MSG_KEXINIT) {
-       bombout(("expected key exchange packet from server"));
-       crReturn(0);
-    }
-    kex = NULL;
-    hostkey = NULL;
-    cscipher_tobe = NULL;
-    sccipher_tobe = NULL;
-    csmac_tobe = NULL;
-    scmac_tobe = NULL;
-    cscomp_tobe = NULL;
-    sccomp_tobe = NULL;
-    pktin.savedpos += 16;             /* skip garbage cookie */
-    ssh2_pkt_getstring(&str, &len);    /* key exchange algorithms */
-    for (i = 0; i < lenof(kex_algs); i++) {
-       if (in_commasep_string(kex_algs[i]->name, str, len)) {
-           kex = kex_algs[i];
-           break;
+    {
+       char *str;
+       int i, j, len;
+
+       if (pktin->type != SSH2_MSG_KEXINIT) {
+           bombout(("expected key exchange packet from server"));
+           crStop(0);
        }
-    }
-    ssh2_pkt_getstring(&str, &len);    /* host key algorithms */
-    for (i = 0; i < lenof(hostkey_algs); i++) {
-       if (in_commasep_string(hostkey_algs[i]->name, str, len)) {
-           hostkey = hostkey_algs[i];
-           break;
+       ssh->kex = NULL;
+       ssh->hostkey = NULL;
+       s->cscipher_tobe = NULL;
+       s->sccipher_tobe = NULL;
+       s->csmac_tobe = NULL;
+       s->scmac_tobe = NULL;
+       s->cscomp_tobe = NULL;
+       s->sccomp_tobe = NULL;
+       pktin->savedpos += 16;          /* skip garbage cookie */
+       ssh_pkt_getstring(pktin, &str, &len);    /* key exchange algorithms */
+       s->warn = 0;
+       for (i = 0; i < s->n_preferred_kex; i++) {
+           const struct ssh_kex *k = s->preferred_kex[i];
+           if (!k) {
+               s->warn = 1;
+           } else if (in_commasep_string(k->name, str, len)) {
+               ssh->kex = k;
+           }
+           if (ssh->kex) {
+               if (s->warn) {
+                    sk_set_frozen(ssh->s, 1);
+                   askalg(ssh->frontend, "key-exchange algorithm",
+                          ssh->kex->name);
+                    sk_set_frozen(ssh->s, 0);
+                }
+               break;
+           }
        }
-    }
-    ssh2_pkt_getstring(&str, &len);    /* client->server cipher */
-    warn = 0;
-    for (i = 0; i < n_preferred_ciphers; i++) {
-       const struct ssh2_ciphers *c = preferred_ciphers[i];
-       if (!c) {
-           warn = 1;
-       } else {
-           for (j = 0; j < c->nciphers; j++) {
-               if (in_commasep_string(c->list[j]->name, str, len)) {
-                   cscipher_tobe = c->list[j];
-                   break;
+       if (!ssh->kex) {
+           bombout(("Couldn't agree a key exchange algorithm (available: %s)",
+                    str ? str : "(null)"));
+           crStop(0);
+       }
+       ssh_pkt_getstring(pktin, &str, &len);    /* host key algorithms */
+       for (i = 0; i < lenof(hostkey_algs); i++) {
+           if (in_commasep_string(hostkey_algs[i]->name, str, len)) {
+               ssh->hostkey = hostkey_algs[i];
+               break;
+           }
+       }
+       ssh_pkt_getstring(pktin, &str, &len);    /* client->server cipher */
+       s->warn = 0;
+       for (i = 0; i < s->n_preferred_ciphers; i++) {
+           const struct ssh2_ciphers *c = s->preferred_ciphers[i];
+           if (!c) {
+               s->warn = 1;
+           } else {
+               for (j = 0; j < c->nciphers; j++) {
+                   if (in_commasep_string(c->list[j]->name, str, len)) {
+                       s->cscipher_tobe = c->list[j];
+                       break;
+                   }
                }
            }
+           if (s->cscipher_tobe) {
+               if (s->warn) {
+                    sk_set_frozen(ssh->s, 1);
+                   askalg(ssh->frontend, "client-to-server cipher",
+                          s->cscipher_tobe->name);
+                    sk_set_frozen(ssh->s, 0);
+                }
+               break;
+           }
        }
-       if (cscipher_tobe) {
-           if (warn)
-               askcipher(cscipher_tobe->name, 1);
-           break;
+       if (!s->cscipher_tobe) {
+           bombout(("Couldn't agree a client-to-server cipher (available: %s)",
+                    str ? str : "(null)"));
+           crStop(0);
        }
-    }
-    if (!cscipher_tobe) {
-       bombout(("Couldn't agree a client-to-server cipher (available: %s)", str));
-       crReturn(0);
-    }
 
-    ssh2_pkt_getstring(&str, &len);    /* server->client cipher */
-    warn = 0;
-    for (i = 0; i < n_preferred_ciphers; i++) {
-       const struct ssh2_ciphers *c = preferred_ciphers[i];
-       if (!c) {
-           warn = 1;
-       } else {
-           for (j = 0; j < c->nciphers; j++) {
-               if (in_commasep_string(c->list[j]->name, str, len)) {
-                   sccipher_tobe = c->list[j];
-                   break;
+       ssh_pkt_getstring(pktin, &str, &len);    /* server->client cipher */
+       s->warn = 0;
+       for (i = 0; i < s->n_preferred_ciphers; i++) {
+           const struct ssh2_ciphers *c = s->preferred_ciphers[i];
+           if (!c) {
+               s->warn = 1;
+           } else {
+               for (j = 0; j < c->nciphers; j++) {
+                   if (in_commasep_string(c->list[j]->name, str, len)) {
+                       s->sccipher_tobe = c->list[j];
+                       break;
+                   }
                }
            }
+           if (s->sccipher_tobe) {
+               if (s->warn) {
+                    sk_set_frozen(ssh->s, 1);
+                   askalg(ssh->frontend, "server-to-client cipher",
+                          s->sccipher_tobe->name);
+                    sk_set_frozen(ssh->s, 0);
+                }
+               break;
+           }
        }
-       if (sccipher_tobe) {
-           if (warn)
-               askcipher(sccipher_tobe->name, 2);
-           break;
+       if (!s->sccipher_tobe) {
+           bombout(("Couldn't agree a server-to-client cipher (available: %s)",
+                    str ? str : "(null)"));
+           crStop(0);
        }
-    }
-    if (!sccipher_tobe) {
-       bombout(("Couldn't agree a server-to-client cipher (available: %s)", str));
-       crReturn(0);
-    }
 
-    ssh2_pkt_getstring(&str, &len);    /* client->server mac */
-    for (i = 0; i < nmacs; i++) {
-       if (in_commasep_string(maclist[i]->name, str, len)) {
-           csmac_tobe = maclist[i];
-           break;
+       ssh_pkt_getstring(pktin, &str, &len);    /* client->server mac */
+       for (i = 0; i < s->nmacs; i++) {
+           if (in_commasep_string(s->maclist[i]->name, str, len)) {
+               s->csmac_tobe = s->maclist[i];
+               break;
+           }
        }
-    }
-    ssh2_pkt_getstring(&str, &len);    /* server->client mac */
-    for (i = 0; i < nmacs; i++) {
-       if (in_commasep_string(maclist[i]->name, str, len)) {
-           scmac_tobe = maclist[i];
-           break;
+       ssh_pkt_getstring(pktin, &str, &len);    /* server->client mac */
+       for (i = 0; i < s->nmacs; i++) {
+           if (in_commasep_string(s->maclist[i]->name, str, len)) {
+               s->scmac_tobe = s->maclist[i];
+               break;
+           }
        }
-    }
-    ssh2_pkt_getstring(&str, &len);    /* client->server compression */
-    for (i = 0; i < lenof(compressions) + 1; i++) {
-       const struct ssh_compress *c =
-           i == 0 ? preferred_comp : compressions[i - 1];
-       if (in_commasep_string(c->name, str, len)) {
-           cscomp_tobe = c;
-           break;
+       ssh_pkt_getstring(pktin, &str, &len);  /* client->server compression */
+       for (i = 0; i < lenof(compressions) + 1; i++) {
+           const struct ssh_compress *c =
+               i == 0 ? s->preferred_comp : compressions[i - 1];
+           if (in_commasep_string(c->name, str, len)) {
+               s->cscomp_tobe = c;
+               break;
+           }
        }
-    }
-    ssh2_pkt_getstring(&str, &len);    /* server->client compression */
-    for (i = 0; i < lenof(compressions) + 1; i++) {
-       const struct ssh_compress *c =
-           i == 0 ? preferred_comp : compressions[i - 1];
-       if (in_commasep_string(c->name, str, len)) {
-           sccomp_tobe = c;
-           break;
+       ssh_pkt_getstring(pktin, &str, &len);  /* server->client compression */
+       for (i = 0; i < lenof(compressions) + 1; i++) {
+           const struct ssh_compress *c =
+               i == 0 ? s->preferred_comp : compressions[i - 1];
+           if (in_commasep_string(c->name, str, len)) {
+               s->sccomp_tobe = c;
+               break;
+           }
        }
     }
 
@@ -3803,153 +5057,269 @@ static int do_ssh2_transport(unsigned char *in, int inlen, int ispkt)
     {
        int csbits, scbits;
 
-       csbits = cscipher_tobe->keylen;
-       scbits = sccipher_tobe->keylen;
-       nbits = (csbits > scbits ? csbits : scbits);
+       csbits = s->cscipher_tobe->keylen;
+       scbits = s->sccipher_tobe->keylen;
+       s->nbits = (csbits > scbits ? csbits : scbits);
     }
     /* The keys only have 160-bit entropy, since they're based on
      * a SHA-1 hash. So cap the key size at 160 bits. */
-    if (nbits > 160)
-       nbits = 160;
+    if (s->nbits > 160)
+       s->nbits = 160;
 
     /*
      * If we're doing Diffie-Hellman group exchange, start by
      * requesting a group.
      */
-    if (kex == &ssh_diffiehellman_gex) {
+    if (!ssh->kex->pdata) {
        logevent("Doing Diffie-Hellman group exchange");
-       ssh_pkt_ctx |= SSH2_PKTCTX_DHGEX;
+       ssh->pkt_ctx |= SSH2_PKTCTX_DHGEX;
        /*
         * Work out how big a DH group we will need to allow that
         * much data.
         */
-       pbits = 512 << ((nbits - 1) / 64);
-       ssh2_pkt_init(SSH2_MSG_KEX_DH_GEX_REQUEST);
-       ssh2_pkt_adduint32(pbits);
-       ssh2_pkt_send();
+       s->pbits = 512 << ((s->nbits - 1) / 64);
+       s->pktout = ssh2_pkt_init(SSH2_MSG_KEX_DH_GEX_REQUEST);
+       ssh2_pkt_adduint32(s->pktout, s->pbits);
+       ssh2_pkt_send_noqueue(ssh, s->pktout);
 
-       crWaitUntil(ispkt);
-       if (pktin.type != SSH2_MSG_KEX_DH_GEX_GROUP) {
+       crWaitUntil(pktin);
+       if (pktin->type != SSH2_MSG_KEX_DH_GEX_GROUP) {
            bombout(("expected key exchange group packet from server"));
-           crReturn(0);
+           crStop(0);
        }
-       p = ssh2_pkt_getmp();
-       g = ssh2_pkt_getmp();
-       dh_setup_group(p, g);
-       kex_init_value = SSH2_MSG_KEX_DH_GEX_INIT;
-       kex_reply_value = SSH2_MSG_KEX_DH_GEX_REPLY;
+       s->p = ssh2_pkt_getmp(pktin);
+       s->g = ssh2_pkt_getmp(pktin);
+       if (!s->p || !s->g) {
+           bombout(("unable to read mp-ints from incoming group packet"));
+           crStop(0);
+       }
+       ssh->kex_ctx = dh_setup_gex(s->p, s->g);
+       s->kex_init_value = SSH2_MSG_KEX_DH_GEX_INIT;
+       s->kex_reply_value = SSH2_MSG_KEX_DH_GEX_REPLY;
     } else {
-       ssh_pkt_ctx |= SSH2_PKTCTX_DHGROUP1;
-       dh_setup_group1();
-       kex_init_value = SSH2_MSG_KEXDH_INIT;
-       kex_reply_value = SSH2_MSG_KEXDH_REPLY;
+       ssh->pkt_ctx |= SSH2_PKTCTX_DHGROUP;
+       ssh->kex_ctx = dh_setup_group(ssh->kex);
+       s->kex_init_value = SSH2_MSG_KEXDH_INIT;
+       s->kex_reply_value = SSH2_MSG_KEXDH_REPLY;
+       logeventf(ssh, "Using Diffie-Hellman with standard group \"%s\"",
+                 ssh->kex->groupname);
     }
 
     logevent("Doing Diffie-Hellman key exchange");
     /*
      * Now generate and send e for Diffie-Hellman.
      */
-    e = dh_create_e(nbits * 2);
-    ssh2_pkt_init(kex_init_value);
-    ssh2_pkt_addmp(e);
-    ssh2_pkt_send();
+    s->e = dh_create_e(ssh->kex_ctx, s->nbits * 2);
+    s->pktout = ssh2_pkt_init(s->kex_init_value);
+    ssh2_pkt_addmp(s->pktout, s->e);
+    ssh2_pkt_send_noqueue(ssh, s->pktout);
 
-    crWaitUntil(ispkt);
-    if (pktin.type != kex_reply_value) {
+    crWaitUntil(pktin);
+    if (pktin->type != s->kex_reply_value) {
        bombout(("expected key exchange reply packet from server"));
-       crReturn(0);
+       crStop(0);
+    }
+    ssh_pkt_getstring(pktin, &s->hostkeydata, &s->hostkeylen);
+    s->f = ssh2_pkt_getmp(pktin);
+    if (!s->f) {
+       bombout(("unable to parse key exchange reply packet"));
+       crStop(0);
     }
-    ssh2_pkt_getstring(&hostkeydata, &hostkeylen);
-    f = ssh2_pkt_getmp();
-    ssh2_pkt_getstring(&sigdata, &siglen);
+    ssh_pkt_getstring(pktin, &s->sigdata, &s->siglen);
 
-    K = dh_find_K(f);
+    s->K = dh_find_K(ssh->kex_ctx, s->f);
 
-    sha_string(&exhash, hostkeydata, hostkeylen);
-    if (kex == &ssh_diffiehellman_gex) {
-       sha_uint32(&exhash, pbits);
-       sha_mpint(&exhash, p);
-       sha_mpint(&exhash, g);
+    sha_string(&ssh->exhash, s->hostkeydata, s->hostkeylen);
+    if (ssh->kex == &ssh_diffiehellman_gex) {
+       sha_uint32(&ssh->exhash, s->pbits);
+       sha_mpint(&ssh->exhash, s->p);
+       sha_mpint(&ssh->exhash, s->g);
     }
-    sha_mpint(&exhash, e);
-    sha_mpint(&exhash, f);
-    sha_mpint(&exhash, K);
-    SHA_Final(&exhash, exchange_hash);
+    sha_mpint(&ssh->exhash, s->e);
+    sha_mpint(&ssh->exhash, s->f);
+    sha_mpint(&ssh->exhash, s->K);
+    SHA_Final(&ssh->exhash, s->exchange_hash);
 
-    dh_cleanup();
+    dh_cleanup(ssh->kex_ctx);
+    ssh->kex_ctx = NULL;
 
 #if 0
     debug(("Exchange hash is:\n"));
-    dmemdump(exchange_hash, 20);
+    dmemdump(s->exchange_hash, 20);
 #endif
 
-    hkey = hostkey->newkey(hostkeydata, hostkeylen);
-    if (!hkey ||
-       !hostkey->verifysig(hkey, sigdata, siglen, exchange_hash, 20)) {
+    s->hkey = ssh->hostkey->newkey(s->hostkeydata, s->hostkeylen);
+    if (!s->hkey ||
+       !ssh->hostkey->verifysig(s->hkey, s->sigdata, s->siglen,
+                                (char *)s->exchange_hash, 20)) {
        bombout(("Server's host key did not match the signature supplied"));
-       crReturn(0);
+       crStop(0);
     }
 
     /*
      * Authenticate remote host: verify host key. (We've already
      * checked the signature of the exchange hash.)
      */
-    keystr = hostkey->fmtkey(hkey);
-    fingerprint = hostkey->fingerprint(hkey);
-    verify_ssh_host_key(savedhost, savedport, hostkey->keytype,
-                       keystr, fingerprint);
-    if (first_kex) {                  /* don't bother logging this in rekeys */
+    s->keystr = ssh->hostkey->fmtkey(s->hkey);
+    s->fingerprint = ssh->hostkey->fingerprint(s->hkey);
+    sk_set_frozen(ssh->s, 1);
+    verify_ssh_host_key(ssh->frontend,
+                       ssh->savedhost, ssh->savedport, ssh->hostkey->keytype,
+                       s->keystr, s->fingerprint);
+    sk_set_frozen(ssh->s, 0);
+    if (!s->got_session_id) {     /* don't bother logging this in rekeys */
        logevent("Host key fingerprint is:");
-       logevent(fingerprint);
+       logevent(s->fingerprint);
+    }
+    sfree(s->fingerprint);
+    sfree(s->keystr);
+    ssh->hostkey->freekey(s->hkey);
+
+    /*
+     * The exchange hash from the very first key exchange is also
+     * the session id, used in session key construction and
+     * authentication.
+     */
+    if (!s->got_session_id) {
+       memcpy(ssh->v2_session_id, s->exchange_hash,
+              sizeof(s->exchange_hash));
+       s->got_session_id = TRUE;
     }
-    sfree(fingerprint);
-    sfree(keystr);
-    hostkey->freekey(hkey);
 
     /*
      * Send SSH2_MSG_NEWKEYS.
      */
-    ssh2_pkt_init(SSH2_MSG_NEWKEYS);
-    ssh2_pkt_send();
+    s->pktout = ssh2_pkt_init(SSH2_MSG_NEWKEYS);
+    ssh2_pkt_send_noqueue(ssh, s->pktout);
+    ssh->outgoing_data_size = 0;       /* start counting from here */
+
+    /*
+     * We've sent client NEWKEYS, so create and initialise
+     * client-to-server session keys.
+     */
+    if (ssh->cs_cipher_ctx)
+       ssh->cscipher->free_context(ssh->cs_cipher_ctx);
+    ssh->cscipher = s->cscipher_tobe;
+    ssh->cs_cipher_ctx = ssh->cscipher->make_context();
+
+    if (ssh->cs_mac_ctx)
+       ssh->csmac->free_context(ssh->cs_mac_ctx);
+    ssh->csmac = s->csmac_tobe;
+    ssh->cs_mac_ctx = ssh->csmac->make_context();
+
+    if (ssh->cs_comp_ctx)
+       ssh->cscomp->compress_cleanup(ssh->cs_comp_ctx);
+    ssh->cscomp = s->cscomp_tobe;
+    ssh->cs_comp_ctx = ssh->cscomp->compress_init();
+
+    /*
+     * Set IVs on client-to-server keys. Here we use the exchange
+     * hash from the _first_ key exchange.
+     */
+    {
+       unsigned char keyspace[40];
+       ssh2_mkkey(ssh,s->K,s->exchange_hash,ssh->v2_session_id,'C',keyspace);
+       ssh->cscipher->setkey(ssh->cs_cipher_ctx, keyspace);
+       ssh2_mkkey(ssh,s->K,s->exchange_hash,ssh->v2_session_id,'A',keyspace);
+       ssh->cscipher->setiv(ssh->cs_cipher_ctx, keyspace);
+       ssh2_mkkey(ssh,s->K,s->exchange_hash,ssh->v2_session_id,'E',keyspace);
+       ssh->csmac->setkey(ssh->cs_mac_ctx, keyspace);
+    }
+
+    logeventf(ssh, "Initialised %.200s client->server encryption",
+             ssh->cscipher->text_name);
+    logeventf(ssh, "Initialised %.200s client->server MAC algorithm",
+             ssh->csmac->text_name);
+    if (ssh->cscomp->text_name)
+       logeventf(ssh, "Initialised %s compression",
+                 ssh->cscomp->text_name);
+
+    /*
+     * Now our end of the key exchange is complete, we can send all
+     * our queued higher-layer packets.
+     */
+    ssh->queueing = FALSE;
+    ssh2_pkt_queuesend(ssh);
 
     /*
      * Expect SSH2_MSG_NEWKEYS from server.
      */
-    crWaitUntil(ispkt);
-    if (pktin.type != SSH2_MSG_NEWKEYS) {
+    crWaitUntil(pktin);
+    if (pktin->type != SSH2_MSG_NEWKEYS) {
        bombout(("expected new-keys packet from server"));
-       crReturn(0);
+       crStop(0);
+    }
+    ssh->incoming_data_size = 0;       /* start counting from here */
+
+    /*
+     * We've seen server NEWKEYS, so create and initialise
+     * server-to-client session keys.
+     */
+    if (ssh->sc_cipher_ctx)
+       ssh->sccipher->free_context(ssh->sc_cipher_ctx);
+    ssh->sccipher = s->sccipher_tobe;
+    ssh->sc_cipher_ctx = ssh->sccipher->make_context();
+
+    if (ssh->sc_mac_ctx)
+       ssh->scmac->free_context(ssh->sc_mac_ctx);
+    ssh->scmac = s->scmac_tobe;
+    ssh->sc_mac_ctx = ssh->scmac->make_context();
+
+    if (ssh->sc_comp_ctx)
+       ssh->sccomp->decompress_cleanup(ssh->sc_comp_ctx);
+    ssh->sccomp = s->sccomp_tobe;
+    ssh->sc_comp_ctx = ssh->sccomp->decompress_init();
+
+    /*
+     * Set IVs on server-to-client keys. Here we use the exchange
+     * hash from the _first_ key exchange.
+     */
+    {
+       unsigned char keyspace[40];
+       ssh2_mkkey(ssh,s->K,s->exchange_hash,ssh->v2_session_id,'D',keyspace);
+       ssh->sccipher->setkey(ssh->sc_cipher_ctx, keyspace);
+       ssh2_mkkey(ssh,s->K,s->exchange_hash,ssh->v2_session_id,'B',keyspace);
+       ssh->sccipher->setiv(ssh->sc_cipher_ctx, keyspace);
+       ssh2_mkkey(ssh,s->K,s->exchange_hash,ssh->v2_session_id,'F',keyspace);
+       ssh->scmac->setkey(ssh->sc_mac_ctx, keyspace);
+    }
+    logeventf(ssh, "Initialised %.200s server->client encryption",
+             ssh->sccipher->text_name);
+    logeventf(ssh, "Initialised %.200s server->client MAC algorithm",
+             ssh->scmac->text_name);
+    if (ssh->sccomp->text_name)
+       logeventf(ssh, "Initialised %s decompression",
+                 ssh->sccomp->text_name);
+
+    /*
+     * Free key exchange data.
+     */
+    freebn(s->f);
+    freebn(s->K);
+    if (ssh->kex == &ssh_diffiehellman_gex) {
+       freebn(s->g);
+       freebn(s->p);
     }
 
     /*
-     * Create and initialise session keys.
+     * Key exchange is over. Loop straight back round if we have a
+     * deferred rekey reason.
      */
-    cscipher = cscipher_tobe;
-    sccipher = sccipher_tobe;
-    csmac = csmac_tobe;
-    scmac = scmac_tobe;
-    cscomp = cscomp_tobe;
-    sccomp = sccomp_tobe;
-    cscomp->compress_init();
-    sccomp->decompress_init();
+    if (ssh->deferred_rekey_reason) {
+       logevent(ssh->deferred_rekey_reason);
+       pktin = NULL;
+       ssh->deferred_rekey_reason = NULL;
+       goto begin_key_exchange;
+    }
+
     /*
-     * Set IVs after keys. Here we use the exchange hash from the
-     * _first_ key exchange.
+     * Otherwise, schedule a timer for our next rekey.
      */
-    if (first_kex)
-       memcpy(ssh2_session_id, exchange_hash, sizeof(exchange_hash));
-    ssh2_mkkey(K, exchange_hash, ssh2_session_id, 'C', keyspace);
-    cscipher->setcskey(keyspace);
-    ssh2_mkkey(K, exchange_hash, ssh2_session_id, 'D', keyspace);
-    sccipher->setsckey(keyspace);
-    ssh2_mkkey(K, exchange_hash, ssh2_session_id, 'A', keyspace);
-    cscipher->setcsiv(keyspace);
-    ssh2_mkkey(K, exchange_hash, ssh2_session_id, 'B', keyspace);
-    sccipher->setsciv(keyspace);
-    ssh2_mkkey(K, exchange_hash, ssh2_session_id, 'E', keyspace);
-    csmac->setcskey(keyspace);
-    ssh2_mkkey(K, exchange_hash, ssh2_session_id, 'F', keyspace);
-    scmac->setsckey(keyspace);
+    ssh->kex_in_progress = FALSE;
+    ssh->last_rekey = GETTICKCOUNT();
+    if (ssh->cfg.ssh_rekey_time != 0)
+       ssh->next_rekey = schedule_timer(ssh->cfg.ssh_rekey_time*60*TICKSPERSEC,
+                                        ssh2_timer, ssh);
 
     /*
      * If this is the first key exchange phase, we must pass the
@@ -3959,21 +5329,53 @@ static int do_ssh2_transport(unsigned char *in, int inlen, int ispkt)
      * exchange phases, we don't pass SSH2_MSG_NEWKEYS on, because
      * it would only confuse the layer above.
      */
-    if (!first_kex) {
-       crReturn(0);
+    if (s->activated_authconn) {
+       crReturn(1);
     }
-    first_kex = 0;
+    s->activated_authconn = TRUE;
 
     /*
      * Now we're encrypting. Begin returning 1 to the protocol main
      * function so that other things can run on top of the
      * transport. If we ever see a KEXINIT, we must go back to the
      * start.
+     * 
+     * We _also_ go back to the start if we see pktin==NULL and
+     * inlen==-1, because this is a special signal meaning
+     * `initiate client-driven rekey', and `in' contains a message
+     * giving the reason for the rekey.
      */
-    while (!(ispkt && pktin.type == SSH2_MSG_KEXINIT)) {
+    while (!((pktin && pktin->type == SSH2_MSG_KEXINIT) ||
+            (!pktin && inlen == -1))) {
+        wait_for_rekey:
        crReturn(1);
     }
-    logevent("Server initiated key re-exchange");
+    if (pktin) {
+       logevent("Server initiated key re-exchange");
+    } else {
+        /*
+         * Special case: if the server bug is set that doesn't
+         * allow rekeying, we give a different log message and
+         * continue waiting. (If such a server _initiates_ a rekey,
+         * we process it anyway!)
+         */
+        if ((ssh->remote_bugs & BUG_SSH2_REKEY)) {
+            logeventf(ssh, "Server bug prevents key re-exchange (%s)",
+                      (char *)in);
+            /* Reset the counters, so that at least this message doesn't
+             * hit the event log _too_ often. */
+            ssh->outgoing_data_size = 0;
+            ssh->incoming_data_size = 0;
+            if (ssh->cfg.ssh_rekey_time != 0) {
+                ssh->next_rekey =
+                    schedule_timer(ssh->cfg.ssh_rekey_time*60*TICKSPERSEC,
+                                   ssh2_timer, ssh);
+            }
+            goto wait_for_rekey;       /* this is utterly horrid */
+        } else {
+            logeventf(ssh, "Initiating key re-exchange (%s)", (char *)in);
+        }
+    }
     goto begin_key_exchange;
 
     crFinish(1);
@@ -3993,6 +5395,9 @@ static void ssh2_add_channel_data(struct ssh_channel *c, char *buf,
  */
 static int ssh2_try_send(struct ssh_channel *c)
 {
+    Ssh ssh = c->ssh;
+    struct Packet *pktout;
+
     while (c->v.v2.remwindow > 0 && bufchain_size(&c->v.v2.outbuffer) > 0) {
        int len;
        void *data;
@@ -4001,11 +5406,13 @@ static int ssh2_try_send(struct ssh_channel *c)
            len = c->v.v2.remwindow;
        if ((unsigned)len > c->v.v2.remmaxpkt)
            len = c->v.v2.remmaxpkt;
-       ssh2_pkt_init(SSH2_MSG_CHANNEL_DATA);
-       ssh2_pkt_adduint32(c->remoteid);
-       ssh2_pkt_addstring_start();
-       ssh2_pkt_addstring_data(data, len);
-       ssh2_pkt_send();
+       pktout = ssh2_pkt_init(SSH2_MSG_CHANNEL_DATA);
+       ssh2_pkt_adduint32(pktout, c->remoteid);
+       dont_log_data(ssh, pktout, PKTLOG_OMIT);
+       ssh2_pkt_addstring_start(pktout);
+       ssh2_pkt_addstring_data(pktout, data, len);
+       end_log_omission(ssh, pktout);
+       ssh2_pkt_send(ssh, pktout);
        bufchain_consume(&c->v.v2.outbuffer, len);
        c->v.v2.remwindow -= len;
     }
@@ -4022,6 +5429,8 @@ static int ssh2_try_send(struct ssh_channel *c)
  */
 static void ssh2_set_window(struct ssh_channel *c, unsigned newwin)
 {
+    Ssh ssh = c->ssh;
+
     /*
      * Never send WINDOW_ADJUST for a channel that the remote side
      * already thinks it's closed; there's no point, since it won't
@@ -4031,66 +5440,612 @@ static void ssh2_set_window(struct ssh_channel *c, unsigned newwin)
        return;
 
     if (newwin > c->v.v2.locwindow) {
-       ssh2_pkt_init(SSH2_MSG_CHANNEL_WINDOW_ADJUST);
-       ssh2_pkt_adduint32(c->remoteid);
-       ssh2_pkt_adduint32(newwin - c->v.v2.locwindow);
-       ssh2_pkt_send();
+       struct Packet *pktout;
+
+       pktout = ssh2_pkt_init(SSH2_MSG_CHANNEL_WINDOW_ADJUST);
+       ssh2_pkt_adduint32(pktout, c->remoteid);
+       ssh2_pkt_adduint32(pktout, newwin - c->v.v2.locwindow);
+       ssh2_pkt_send(ssh, pktout);
        c->v.v2.locwindow = newwin;
     }
 }
 
+static void ssh2_msg_channel_window_adjust(Ssh ssh, struct Packet *pktin)
+{
+    unsigned i = ssh_pkt_getuint32(pktin);
+    struct ssh_channel *c;
+    c = find234(ssh->channels, &i, ssh_channelfind);
+    if (c && !c->closes)
+       c->v.v2.remwindow += ssh_pkt_getuint32(pktin);
+}
+
+static void ssh2_msg_channel_data(Ssh ssh, struct Packet *pktin)
+{
+    char *data;
+    unsigned int length;
+    unsigned i = ssh_pkt_getuint32(pktin);
+    struct ssh_channel *c;
+    c = find234(ssh->channels, &i, ssh_channelfind);
+    if (!c)
+       return;                        /* nonexistent channel */
+    if (pktin->type == SSH2_MSG_CHANNEL_EXTENDED_DATA &&
+       ssh_pkt_getuint32(pktin) != SSH2_EXTENDED_DATA_STDERR)
+       return;                        /* extended but not stderr */
+    ssh_pkt_getstring(pktin, &data, &length);
+    if (data) {
+       int bufsize = 0;
+       c->v.v2.locwindow -= length;
+       switch (c->type) {
+         case CHAN_MAINSESSION:
+           bufsize =
+               from_backend(ssh->frontend, pktin->type ==
+                            SSH2_MSG_CHANNEL_EXTENDED_DATA,
+                            data, length);
+           break;
+         case CHAN_X11:
+           bufsize = x11_send(c->u.x11.s, data, length);
+           break;
+         case CHAN_SOCKDATA:
+           bufsize = pfd_send(c->u.pfd.s, data, length);
+           break;
+         case CHAN_AGENT:
+           while (length > 0) {
+               if (c->u.a.lensofar < 4) {
+                   unsigned int l = min(4 - c->u.a.lensofar, length);
+                   memcpy(c->u.a.msglen + c->u.a.lensofar,
+                          data, l);
+                   data += l;
+                   length -= l;
+                   c->u.a.lensofar += l;
+               }
+               if (c->u.a.lensofar == 4) {
+                   c->u.a.totallen =
+                       4 + GET_32BIT(c->u.a.msglen);
+                   c->u.a.message = snewn(c->u.a.totallen,
+                                          unsigned char);
+                   memcpy(c->u.a.message, c->u.a.msglen, 4);
+               }
+               if (c->u.a.lensofar >= 4 && length > 0) {
+                   unsigned int l =
+                       min(c->u.a.totallen - c->u.a.lensofar,
+                           length);
+                   memcpy(c->u.a.message + c->u.a.lensofar,
+                          data, l);
+                   data += l;
+                   length -= l;
+                   c->u.a.lensofar += l;
+               }
+               if (c->u.a.lensofar == c->u.a.totallen) {
+                   void *reply;
+                   int replylen;
+                   if (agent_query(c->u.a.message,
+                                   c->u.a.totallen,
+                                   &reply, &replylen,
+                                   ssh_agentf_callback, c))
+                       ssh_agentf_callback(c, reply, replylen);
+                   sfree(c->u.a.message);
+                   c->u.a.lensofar = 0;
+               }
+           }
+           bufsize = 0;
+           break;
+       }
+       /*
+        * If we are not buffering too much data,
+        * enlarge the window again at the remote side.
+        */
+       if (bufsize < OUR_V2_WINSIZE)
+           ssh2_set_window(c, OUR_V2_WINSIZE - bufsize);
+    }
+}
+
+static void ssh2_msg_channel_eof(Ssh ssh, struct Packet *pktin)
+{
+    unsigned i = ssh_pkt_getuint32(pktin);
+    struct ssh_channel *c;
+
+    c = find234(ssh->channels, &i, ssh_channelfind);
+    if (!c)
+       return;                        /* nonexistent channel */
+
+    if (c->type == CHAN_X11) {
+       /*
+        * Remote EOF on an X11 channel means we should
+        * wrap up and close the channel ourselves.
+        */
+       x11_close(c->u.x11.s);
+       sshfwd_close(c);
+    } else if (c->type == CHAN_AGENT) {
+       sshfwd_close(c);
+    } else if (c->type == CHAN_SOCKDATA) {
+       pfd_close(c->u.pfd.s);
+       sshfwd_close(c);
+    }
+}
+
+static void ssh2_msg_channel_close(Ssh ssh, struct Packet *pktin)
+{
+    unsigned i = ssh_pkt_getuint32(pktin);
+    struct ssh_channel *c;
+    struct Packet *pktout;
+
+    c = find234(ssh->channels, &i, ssh_channelfind);
+    if (!c || ((int)c->remoteid) == -1) {
+       bombout(("Received CHANNEL_CLOSE for %s channel %d\n",
+                c ? "half-open" : "nonexistent", i));
+       return;
+    }
+    /* Do pre-close processing on the channel. */
+    switch (c->type) {
+      case CHAN_MAINSESSION:
+       ssh->mainchan = NULL;
+       update_specials_menu(ssh->frontend);
+       break;
+      case CHAN_X11:
+       if (c->u.x11.s != NULL)
+           x11_close(c->u.x11.s);
+       sshfwd_close(c);
+       break;
+      case CHAN_AGENT:
+       sshfwd_close(c);
+       break;
+      case CHAN_SOCKDATA:
+       if (c->u.pfd.s != NULL)
+           pfd_close(c->u.pfd.s);
+       sshfwd_close(c);
+       break;
+    }
+    if (c->closes == 0) {
+       pktout = ssh2_pkt_init(SSH2_MSG_CHANNEL_CLOSE);
+       ssh2_pkt_adduint32(pktout, c->remoteid);
+       ssh2_pkt_send(ssh, pktout);
+    }
+    del234(ssh->channels, c);
+    bufchain_clear(&c->v.v2.outbuffer);
+    sfree(c);
+
+    /*
+     * See if that was the last channel left open.
+     * (This is only our termination condition if we're
+     * not running in -N mode.)
+     */
+    if (!ssh->cfg.ssh_no_shell && count234(ssh->channels) == 0) {
+       logevent("All channels closed. Disconnecting");
+#if 0
+       /*
+        * We used to send SSH_MSG_DISCONNECT here,
+        * because I'd believed that _every_ conforming
+        * SSH2 connection had to end with a disconnect
+        * being sent by at least one side; apparently
+        * I was wrong and it's perfectly OK to
+        * unceremoniously slam the connection shut
+        * when you're done, and indeed OpenSSH feels
+        * this is more polite than sending a
+        * DISCONNECT. So now we don't.
+        */
+       s->pktout = ssh2_pkt_init(SSH2_MSG_DISCONNECT);
+       ssh2_pkt_adduint32(s->pktout, SSH2_DISCONNECT_BY_APPLICATION);
+       ssh2_pkt_addstring(s->pktout, "All open channels closed");
+       ssh2_pkt_addstring(s->pktout, "en");    /* language tag */
+       ssh2_pkt_send_noqueue(ssh, s->pktout);
+#endif
+       ssh->close_expected = TRUE;
+       ssh_closing((Plug)ssh, NULL, 0, 0);
+    }
+}
+
+static void ssh2_msg_channel_open_confirmation(Ssh ssh, struct Packet *pktin)
+{
+    unsigned i = ssh_pkt_getuint32(pktin);
+    struct ssh_channel *c;
+    struct Packet *pktout;
+
+    c = find234(ssh->channels, &i, ssh_channelfind);
+    if (!c)
+       return;                        /* nonexistent channel */
+    if (c->type != CHAN_SOCKDATA_DORMANT)
+       return;                        /* dunno why they're confirming this */
+    c->remoteid = ssh_pkt_getuint32(pktin);
+    c->type = CHAN_SOCKDATA;
+    c->v.v2.remwindow = ssh_pkt_getuint32(pktin);
+    c->v.v2.remmaxpkt = ssh_pkt_getuint32(pktin);
+    if (c->u.pfd.s)
+       pfd_confirm(c->u.pfd.s);
+    if (c->closes) {
+       /*
+        * We have a pending close on this channel,
+        * which we decided on before the server acked
+        * the channel open. So now we know the
+        * remoteid, we can close it again.
+        */
+       pktout = ssh2_pkt_init(SSH2_MSG_CHANNEL_CLOSE);
+       ssh2_pkt_adduint32(pktout, c->remoteid);
+       ssh2_pkt_send(ssh, pktout);
+    }
+}
+
+static void ssh2_msg_channel_open_failure(Ssh ssh, struct Packet *pktin)
+{
+    static const char *const reasons[] = {
+       "<unknown reason code>",
+           "Administratively prohibited",
+           "Connect failed",
+           "Unknown channel type",
+           "Resource shortage",
+    };
+    unsigned i = ssh_pkt_getuint32(pktin);
+    unsigned reason_code;
+    char *reason_string;
+    int reason_length;
+    char *message;
+    struct ssh_channel *c;
+    c = find234(ssh->channels, &i, ssh_channelfind);
+    if (!c)
+       return;                        /* nonexistent channel */
+    if (c->type != CHAN_SOCKDATA_DORMANT)
+       return;                        /* dunno why they're failing this */
+
+    reason_code = ssh_pkt_getuint32(pktin);
+    if (reason_code >= lenof(reasons))
+       reason_code = 0; /* ensure reasons[reason_code] in range */
+    ssh_pkt_getstring(pktin, &reason_string, &reason_length);
+    message = dupprintf("Forwarded connection refused by"
+                       " server: %s [%.*s]", reasons[reason_code],
+                       reason_length, reason_string);
+    logevent(message);
+    sfree(message);
+
+    pfd_close(c->u.pfd.s);
+
+    del234(ssh->channels, c);
+    sfree(c);
+}
+
+static void ssh2_msg_channel_request(Ssh ssh, struct Packet *pktin)
+{
+    unsigned localid;
+    char *type;
+    int typelen, want_reply;
+    int reply = SSH2_MSG_CHANNEL_FAILURE; /* default */
+    struct ssh_channel *c;
+    struct Packet *pktout;
+
+    localid = ssh_pkt_getuint32(pktin);
+    ssh_pkt_getstring(pktin, &type, &typelen);
+    want_reply = ssh2_pkt_getbool(pktin);
+
+    /*
+     * First, check that the channel exists. Otherwise,
+     * we can instantly disconnect with a rude message.
+     */
+    c = find234(ssh->channels, &localid, ssh_channelfind);
+    if (!c) {
+       char buf[80];
+       sprintf(buf, "Received channel request for nonexistent"
+               " channel %d", localid);
+       logevent(buf);
+       pktout = ssh2_pkt_init(SSH2_MSG_DISCONNECT);
+       ssh2_pkt_adduint32(pktout, SSH2_DISCONNECT_BY_APPLICATION);
+       ssh2_pkt_addstring(pktout, buf);
+       ssh2_pkt_addstring(pktout, "en");       /* language tag */
+       ssh2_pkt_send_noqueue(ssh, pktout);
+       connection_fatal(ssh->frontend, "%s", buf);
+       ssh->close_expected = TRUE;
+       ssh_closing((Plug)ssh, NULL, 0, 0);
+       return;
+    }
+
+    /*
+     * Having got the channel number, we now look at
+     * the request type string to see if it's something
+     * we recognise.
+     */
+    if (c == ssh->mainchan) {
+       /*
+        * We recognise "exit-status" and "exit-signal" on
+        * the primary channel.
+        */
+       if (typelen == 11 &&
+           !memcmp(type, "exit-status", 11)) {
+
+           ssh->exitcode = ssh_pkt_getuint32(pktin);
+           logeventf(ssh, "Server sent command exit status %d",
+                     ssh->exitcode);
+           reply = SSH2_MSG_CHANNEL_SUCCESS;
+
+       } else if (typelen == 11 &&
+                  !memcmp(type, "exit-signal", 11)) {
+
+           int is_plausible = TRUE, is_int = FALSE;
+           char *fmt_sig = "", *fmt_msg = "";
+           char *msg;
+           int msglen = 0, core = FALSE;
+           /* ICK: older versions of OpenSSH (e.g. 3.4p1)
+            * provide an `int' for the signal, despite its
+            * having been a `string' in the drafts since at
+            * least 2001. (Fixed in session.c 1.147.) Try to
+            * infer which we can safely parse it as. */
+           {
+               unsigned char *p = pktin->body +
+                   pktin->savedpos;
+               long len = pktin->length - pktin->savedpos;
+               unsigned long num = GET_32BIT(p); /* what is it? */
+               /* If it's 0, it hardly matters; assume string */
+               if (num == 0) {
+                   is_int = FALSE;
+               } else {
+                   int maybe_int = FALSE, maybe_str = FALSE;
+#define CHECK_HYPOTHESIS(offset, result) \
+    do { \
+       long q = offset; \
+       if (q >= 0 && q+4 <= len) { \
+           q = q + 4 + GET_32BIT(p+q); \
+           if (q >= 0 && q+4 <= len && \
+                   (q = q + 4 + GET_32BIT(p+q)) && q == len) \
+               result = TRUE; \
+       } \
+    } while(0)
+                   CHECK_HYPOTHESIS(4+1, maybe_int);
+                   CHECK_HYPOTHESIS(4+num+1, maybe_str);
+#undef CHECK_HYPOTHESIS
+                   if (maybe_int && !maybe_str)
+                       is_int = TRUE;
+                   else if (!maybe_int && maybe_str)
+                       is_int = FALSE;
+                   else
+                       /* Crikey. Either or neither. Panic. */
+                       is_plausible = FALSE;
+               }
+           }
+           if (is_plausible) {
+               if (is_int) {
+                   /* Old non-standard OpenSSH. */
+                   int signum = ssh_pkt_getuint32(pktin);
+                   fmt_sig = dupprintf(" %d", signum);
+               } else {
+                   /* As per the drafts. */
+                   char *sig;
+                   int siglen;
+                   ssh_pkt_getstring(pktin, &sig, &siglen);
+                   /* Signal name isn't supposed to be blank, but
+                    * let's cope gracefully if it is. */
+                   if (siglen) {
+                       fmt_sig = dupprintf(" \"%.*s\"",
+                                           siglen, sig);
+                   }
+               }
+               core = ssh2_pkt_getbool(pktin);
+               ssh_pkt_getstring(pktin, &msg, &msglen);
+               if (msglen) {
+                   fmt_msg = dupprintf(" (\"%.*s\")", msglen, msg);
+               }
+               /* ignore lang tag */
+           } /* else don't attempt to parse */
+           logeventf(ssh, "Server exited on signal%s%s%s",
+                     fmt_sig, core ? " (core dumped)" : "",
+                     fmt_msg);
+           if (*fmt_sig) sfree(fmt_sig);
+           if (*fmt_msg) sfree(fmt_msg);
+           reply = SSH2_MSG_CHANNEL_SUCCESS;
+
+       }
+    } else {
+       /*
+        * This is a channel request we don't know
+        * about, so we now either ignore the request
+        * or respond with CHANNEL_FAILURE, depending
+        * on want_reply.
+        */
+       reply = SSH2_MSG_CHANNEL_FAILURE;
+    }
+    if (want_reply) {
+       pktout = ssh2_pkt_init(reply);
+       ssh2_pkt_adduint32(pktout, c->remoteid);
+       ssh2_pkt_send(ssh, pktout);
+    }
+}
+
+static void ssh2_msg_global_request(Ssh ssh, struct Packet *pktin)
+{
+    char *type;
+    int typelen, want_reply;
+    struct Packet *pktout;
+
+    ssh_pkt_getstring(pktin, &type, &typelen);
+    want_reply = ssh2_pkt_getbool(pktin);
+
+    /*
+     * We currently don't support any global requests
+     * at all, so we either ignore the request or
+     * respond with REQUEST_FAILURE, depending on
+     * want_reply.
+     */
+    if (want_reply) {
+       pktout = ssh2_pkt_init(SSH2_MSG_REQUEST_FAILURE);
+       ssh2_pkt_send(ssh, pktout);
+    }
+}
+
+static void ssh2_msg_channel_open(Ssh ssh, struct Packet *pktin)
+{
+    char *type;
+    int typelen;
+    char *peeraddr;
+    int peeraddrlen;
+    int peerport;
+    char *error = NULL;
+    struct ssh_channel *c;
+    unsigned remid, winsize, pktsize;
+    struct Packet *pktout;
+
+    ssh_pkt_getstring(pktin, &type, &typelen);
+    c = snew(struct ssh_channel);
+    c->ssh = ssh;
+
+    remid = ssh_pkt_getuint32(pktin);
+    winsize = ssh_pkt_getuint32(pktin);
+    pktsize = ssh_pkt_getuint32(pktin);
+
+    if (typelen == 3 && !memcmp(type, "x11", 3)) {
+       char *addrstr;
+
+       ssh_pkt_getstring(pktin, &peeraddr, &peeraddrlen);
+       addrstr = snewn(peeraddrlen+1, char);
+       memcpy(addrstr, peeraddr, peeraddrlen);
+       addrstr[peeraddrlen] = '\0';
+       peerport = ssh_pkt_getuint32(pktin);
+
+       logeventf(ssh, "Received X11 connect request from %s:%d",
+                 addrstr, peerport);
+
+       if (!ssh->X11_fwd_enabled)
+           error = "X11 forwarding is not enabled";
+       else if (x11_init(&c->u.x11.s, ssh->cfg.x11_display, c,
+                         ssh->x11auth, addrstr, peerport,
+                         &ssh->cfg) != NULL) {
+           error = "Unable to open an X11 connection";
+       } else {
+           logevent("Opening X11 forward connection succeeded");
+           c->type = CHAN_X11;
+       }
+
+       sfree(addrstr);
+    } else if (typelen == 15 &&
+              !memcmp(type, "forwarded-tcpip", 15)) {
+       struct ssh_rportfwd pf, *realpf;
+       char *dummy;
+       int dummylen;
+       ssh_pkt_getstring(pktin, &dummy, &dummylen);/* skip address */
+       pf.sport = ssh_pkt_getuint32(pktin);
+       ssh_pkt_getstring(pktin, &peeraddr, &peeraddrlen);
+       peerport = ssh_pkt_getuint32(pktin);
+       realpf = find234(ssh->rportfwds, &pf, NULL);
+       logeventf(ssh, "Received remote port %d open request "
+                 "from %s:%d", pf.sport, peeraddr, peerport);
+       if (realpf == NULL) {
+           error = "Remote port is not recognised";
+       } else {
+           const char *e = pfd_newconnect(&c->u.pfd.s,
+                                          realpf->dhost,
+                                          realpf->dport, c,
+                                          &ssh->cfg,
+                                          realpf->pfrec->addressfamily);
+           logeventf(ssh, "Attempting to forward remote port to "
+                     "%s:%d", realpf->dhost, realpf->dport);
+           if (e != NULL) {
+               logeventf(ssh, "Port open failed: %s", e);
+               error = "Port open failed";
+           } else {
+               logevent("Forwarded port opened successfully");
+               c->type = CHAN_SOCKDATA;
+           }
+       }
+    } else if (typelen == 22 &&
+              !memcmp(type, "auth-agent@openssh.com", 3)) {
+       if (!ssh->agentfwd_enabled)
+           error = "Agent forwarding is not enabled";
+       else {
+           c->type = CHAN_AGENT;       /* identify channel type */
+           c->u.a.lensofar = 0;
+       }
+    } else {
+       error = "Unsupported channel type requested";
+    }
+
+    c->remoteid = remid;
+    if (error) {
+       pktout = ssh2_pkt_init(SSH2_MSG_CHANNEL_OPEN_FAILURE);
+       ssh2_pkt_adduint32(pktout, c->remoteid);
+       ssh2_pkt_adduint32(pktout, SSH2_OPEN_CONNECT_FAILED);
+       ssh2_pkt_addstring(pktout, error);
+       ssh2_pkt_addstring(pktout, "en");       /* language tag */
+       ssh2_pkt_send(ssh, pktout);
+       logeventf(ssh, "Rejected channel open: %s", error);
+       sfree(c);
+    } else {
+       c->localid = alloc_channel_id(ssh);
+       c->closes = 0;
+       c->v.v2.locwindow = OUR_V2_WINSIZE;
+       c->v.v2.remwindow = winsize;
+       c->v.v2.remmaxpkt = pktsize;
+       bufchain_init(&c->v.v2.outbuffer);
+       add234(ssh->channels, c);
+       pktout = ssh2_pkt_init(SSH2_MSG_CHANNEL_OPEN_CONFIRMATION);
+       ssh2_pkt_adduint32(pktout, c->remoteid);
+       ssh2_pkt_adduint32(pktout, c->localid);
+       ssh2_pkt_adduint32(pktout, c->v.v2.locwindow);
+       ssh2_pkt_adduint32(pktout, OUR_V2_MAXPKT);      /* our max pkt size */
+       ssh2_pkt_send(ssh, pktout);
+    }
+}
+
 /*
  * Handle the SSH2 userauth and connection layers.
  */
-static void do_ssh2_authconn(unsigned char *in, int inlen, int ispkt)
-{
-    static enum {
-       AUTH_INVALID, AUTH_PUBLICKEY_AGENT, AUTH_PUBLICKEY_FILE,
-       AUTH_PASSWORD,
-        AUTH_KEYBOARD_INTERACTIVE
-    } method;
-    static enum {
-       AUTH_TYPE_NONE,
-       AUTH_TYPE_PUBLICKEY,
-       AUTH_TYPE_PUBLICKEY_OFFER_LOUD,
-       AUTH_TYPE_PUBLICKEY_OFFER_QUIET,
-       AUTH_TYPE_PASSWORD,
-       AUTH_TYPE_KEYBOARD_INTERACTIVE,
-       AUTH_TYPE_KEYBOARD_INTERACTIVE_QUIET
-    } type;
-    static int gotit, need_pw, can_pubkey, can_passwd, can_keyb_inter;
-    static int tried_pubkey_config, tried_agent, tried_keyb_inter;
-    static int kbd_inter_running;
-    static int we_are_in;
-    static int num_prompts, curr_prompt, echo;
-    static char username[100];
-    static int got_username;
-    static char pwprompt[200];
-    static char password[100];
-    static void *publickey_blob;
-    static int publickey_bloblen;
-
-    crBegin;
+static void do_ssh2_authconn(Ssh ssh, unsigned char *in, int inlen,
+                            struct Packet *pktin)
+{
+    struct do_ssh2_authconn_state {
+       enum {
+           AUTH_INVALID, AUTH_PUBLICKEY_AGENT, AUTH_PUBLICKEY_FILE,
+               AUTH_PASSWORD,
+               AUTH_KEYBOARD_INTERACTIVE
+       } method;
+       enum {
+           AUTH_TYPE_NONE,
+               AUTH_TYPE_PUBLICKEY,
+               AUTH_TYPE_PUBLICKEY_OFFER_LOUD,
+               AUTH_TYPE_PUBLICKEY_OFFER_QUIET,
+               AUTH_TYPE_PASSWORD,
+               AUTH_TYPE_KEYBOARD_INTERACTIVE,
+               AUTH_TYPE_KEYBOARD_INTERACTIVE_QUIET
+       } type;
+       int gotit, need_pw, can_pubkey, can_passwd, can_keyb_inter;
+       int tried_pubkey_config, tried_agent;
+       int kbd_inter_running, kbd_inter_refused;
+       int we_are_in;
+       int num_prompts, curr_prompt, echo;
+       char username[100];
+       int got_username;
+       char pwprompt[512];
+       char password[100];
+       void *publickey_blob;
+       int publickey_bloblen;
+       unsigned char request[5], *response, *p;
+       int responselen;
+       int keyi, nkeys;
+       int authed;
+       char *pkblob, *alg, *commentp;
+       int pklen, alglen, commentlen;
+       int siglen, retlen, len;
+       char *q, *agentreq, *ret;
+       int try_send;
+       int num_env, env_left, env_ok;
+       struct Packet *pktout;
+    };
+    crState(do_ssh2_authconn_state);
+
+    crBegin(ssh->do_ssh2_authconn_crstate);
 
     /*
      * Request userauth protocol, and await a response to it.
      */
-    ssh2_pkt_init(SSH2_MSG_SERVICE_REQUEST);
-    ssh2_pkt_addstring("ssh-userauth");
-    ssh2_pkt_send();
-    crWaitUntilV(ispkt);
-    if (pktin.type != SSH2_MSG_SERVICE_ACCEPT) {
+    s->pktout = ssh2_pkt_init(SSH2_MSG_SERVICE_REQUEST);
+    ssh2_pkt_addstring(s->pktout, "ssh-userauth");
+    ssh2_pkt_send(ssh, s->pktout);
+    crWaitUntilV(pktin);
+    if (pktin->type != SSH2_MSG_SERVICE_ACCEPT) {
        bombout(("Server refused user authentication protocol"));
-       crReturnV;
+       crStopV;
     }
 
     /*
      * We repeat this whole loop, including the username prompt,
      * until we manage a successful authentication. If the user
-     * types the wrong _password_, they are sent back to the
-     * beginning to try another username. (If they specify a
-     * username in the config, they are never asked, even if they
-     * do give a wrong password.)
+     * types the wrong _password_, they can be sent back to the
+     * beginning to try another username, if this is configured on.
+     * (If they specify a username in the config, they are never
+     * asked, even if they do give a wrong password.)
      * 
      * I think this best serves the needs of
      * 
@@ -4108,102 +6063,109 @@ static void do_ssh2_authconn(unsigned char *in, int inlen, int ispkt)
      *    the username they will want to be able to get back and
      *    retype it!
      */
-    username[0] = '\0';
-    got_username = FALSE;
+    s->username[0] = '\0';
+    s->got_username = FALSE;
     do {
        /*
         * Get a username.
         */
-       if (got_username && !cfg.change_username) {
+       if (s->got_username && !ssh->cfg.change_username) {
            /*
             * We got a username last time round this loop, and
             * with change_username turned off we don't try to get
             * it again.
             */
-       } else if ((flags & FLAG_INTERACTIVE) && !*cfg.username) {
+       } else if (!*ssh->cfg.username) {
            if (ssh_get_line && !ssh_getline_pw_only) {
                if (!ssh_get_line("login as: ",
-                                 username, sizeof(username), FALSE)) {
+                                 s->username, sizeof(s->username), FALSE)) {
                    /*
                     * get_line failed to get a username.
                     * Terminate.
                     */
                    logevent("No username provided. Abandoning session.");
-                   ssh_state = SSH_STATE_CLOSED;
-                   crReturnV;
+                   ssh->close_expected = TRUE;
+                    ssh_closing((Plug)ssh, NULL, 0, 0);
+                   crStopV;
                }
            } else {
-               static int ret;
-               c_write_str("login as: ");
-               ssh_send_ok = 1;
-               setup_userpass_input(username, sizeof(username), 1);
+               int ret;               /* need not be saved across crReturn */
+               c_write_str(ssh, "login as: ");
+               ssh->send_ok = 1;
+               setup_userpass_input(ssh, s->username, sizeof(s->username), 1);
                do {
-                   crWaitUntilV(!ispkt);
-                   ret = process_userpass_input(in, inlen);
+                   crWaitUntilV(!pktin);
+                   ret = process_userpass_input(ssh, in, inlen);
                } while (ret == 0);
                if (ret < 0)
                    cleanup_exit(0);
+               c_write_str(ssh, "\r\n");
            }
-           c_write_str("\r\n");
-           username[strcspn(username, "\n\r")] = '\0';
+           s->username[strcspn(s->username, "\n\r")] = '\0';
        } else {
-           char stuff[200];
-           strncpy(username, cfg.username, 99);
-           username[99] = '\0';
+           char *stuff;
+           strncpy(s->username, ssh->cfg.username, sizeof(s->username));
+           s->username[sizeof(s->username)-1] = '\0';
            if ((flags & FLAG_VERBOSE) || (flags & FLAG_INTERACTIVE)) {
-               sprintf(stuff, "Using username \"%s\".\r\n", username);
-               c_write_str(stuff);
+               stuff = dupprintf("Using username \"%s\".\r\n", s->username);
+               c_write_str(ssh, stuff);
+               sfree(stuff);
            }
        }
-       got_username = TRUE;
+       s->got_username = TRUE;
 
        /*
         * Send an authentication request using method "none": (a)
         * just in case it succeeds, and (b) so that we know what
         * authentication methods we can usefully try next.
         */
-       ssh_pkt_ctx &= ~SSH2_PKTCTX_AUTH_MASK;
-
-       ssh2_pkt_init(SSH2_MSG_USERAUTH_REQUEST);
-       ssh2_pkt_addstring(username);
-       ssh2_pkt_addstring("ssh-connection");   /* service requested */
-       ssh2_pkt_addstring("none");    /* method */
-       ssh2_pkt_send();
-       type = AUTH_TYPE_NONE;
-       gotit = FALSE;
-       we_are_in = FALSE;
-
-       tried_pubkey_config = FALSE;
-       tried_agent = FALSE;
-       tried_keyb_inter = FALSE;
-       kbd_inter_running = FALSE;
-       /* Load the pub half of cfg.keyfile so we notice if it's in Pageant */
-       if (*cfg.keyfile) {
+       ssh->pkt_ctx &= ~SSH2_PKTCTX_AUTH_MASK;
+
+       s->pktout = ssh2_pkt_init(SSH2_MSG_USERAUTH_REQUEST);
+       ssh2_pkt_addstring(s->pktout, s->username);
+       ssh2_pkt_addstring(s->pktout, "ssh-connection");/* service requested */
+       ssh2_pkt_addstring(s->pktout, "none");    /* method */
+       ssh2_pkt_send(ssh, s->pktout);
+       s->type = AUTH_TYPE_NONE;
+       s->gotit = FALSE;
+       s->we_are_in = FALSE;
+
+       s->tried_pubkey_config = FALSE;
+       s->tried_agent = FALSE;
+       s->kbd_inter_running = FALSE;
+       s->kbd_inter_refused = FALSE;
+       /* Load the pub half of ssh->cfg.keyfile so we notice if it's in Pageant */
+       if (!filename_is_null(ssh->cfg.keyfile)) {
            int keytype;
-           logeventf("Reading private key file \"%.150s\"", cfg.keyfile);
-           keytype = key_type(cfg.keyfile);
-           if (keytype == SSH_KEYTYPE_SSH2)
-               publickey_blob = ssh2_userkey_loadpub(cfg.keyfile, NULL,
-                                                     &publickey_bloblen);
-           else {
-               char msgbuf[256];
-               logeventf("Unable to use this key file (%s)",
-                       key_type_to_str(keytype));
-               sprintf(msgbuf, "Unable to use key file \"%.150s\" (%s)\r\n",
-                       cfg.keyfile, key_type_to_str(keytype));
-               c_write_str(msgbuf);
-               publickey_blob = NULL;
+           logeventf(ssh, "Reading private key file \"%.150s\"",
+                     filename_to_str(&ssh->cfg.keyfile));
+           keytype = key_type(&ssh->cfg.keyfile);
+           if (keytype == SSH_KEYTYPE_SSH2) {
+               s->publickey_blob =
+                   ssh2_userkey_loadpub(&ssh->cfg.keyfile, NULL,
+                                        &s->publickey_bloblen, NULL);
+           } else {
+               char *msgbuf;
+               logeventf(ssh, "Unable to use this key file (%s)",
+                         key_type_to_str(keytype));
+               msgbuf = dupprintf("Unable to use key file \"%.150s\""
+                                  " (%s)\r\n",
+                                  filename_to_str(&ssh->cfg.keyfile),
+                                  key_type_to_str(keytype));
+               c_write_str(ssh, msgbuf);
+               sfree(msgbuf);
+               s->publickey_blob = NULL;
            }
        } else
-           publickey_blob = NULL;
+           s->publickey_blob = NULL;
 
        while (1) {
            /*
             * Wait for the result of the last authentication request.
             */
-           if (!gotit)
-               crWaitUntilV(ispkt);
-           while (pktin.type == SSH2_MSG_USERAUTH_BANNER) {
+           if (!s->gotit)
+               crWaitUntilV(pktin);
+           while (pktin->type == SSH2_MSG_USERAUTH_BANNER) {
                char *banner;
                int size;
                /*
@@ -4215,20 +6177,20 @@ static void do_ssh2_authconn(unsigned char *in, int inlen, int ispkt)
                 * output of (say) plink.)
                 */
                if (flags & (FLAG_VERBOSE | FLAG_INTERACTIVE)) {
-                   ssh2_pkt_getstring(&banner, &size);
+                   ssh_pkt_getstring(pktin, &banner, &size);
                    if (banner)
-                       c_write_untrusted(banner, size);
+                       c_write_untrusted(ssh, banner, size);
                }
-               crWaitUntilV(ispkt);
+               crWaitUntilV(pktin);
            }
-           if (pktin.type == SSH2_MSG_USERAUTH_SUCCESS) {
+           if (pktin->type == SSH2_MSG_USERAUTH_SUCCESS) {
                logevent("Access granted");
-               we_are_in = TRUE;
+               s->we_are_in = TRUE;
                break;
            }
 
-           if (kbd_inter_running &&
-               pktin.type == SSH2_MSG_USERAUTH_INFO_REQUEST) {
+           if (s->kbd_inter_running &&
+               pktin->type == SSH2_MSG_USERAUTH_INFO_REQUEST) {
                /*
                 * This is either a further set-of-prompts packet
                 * in keyboard-interactive authentication, or it's
@@ -4236,27 +6198,31 @@ static void do_ssh2_authconn(unsigned char *in, int inlen, int ispkt)
                 * set. In the former case, we must reset the
                 * curr_prompt variable.
                 */
-               if (!gotit)
-                   curr_prompt = 0;
-           } else if (pktin.type != SSH2_MSG_USERAUTH_FAILURE) {
+               if (!s->gotit)
+                   s->curr_prompt = 0;
+           } else if (pktin->type == SSH2_MSG_USERAUTH_PASSWD_CHANGEREQ) {
+               /* FIXME: perhaps we should support this? */
+               bombout(("PASSWD_CHANGEREQ not yet supported"));
+               crStopV;
+           } else if (pktin->type != SSH2_MSG_USERAUTH_FAILURE) {
                bombout(("Strange packet received during authentication: type %d",
-                        pktin.type));
-               crReturnV;
+                        pktin->type));
+               crStopV;
            }
 
-           gotit = FALSE;
+           s->gotit = FALSE;
 
            /*
             * OK, we're now sitting on a USERAUTH_FAILURE message, so
             * we can look at the string in it and know what we can
             * helpfully try next.
             */
-           if (pktin.type == SSH2_MSG_USERAUTH_FAILURE) {
+           if (pktin->type == SSH2_MSG_USERAUTH_FAILURE) {
                char *methods;
                int methlen;
-               ssh2_pkt_getstring(&methods, &methlen);
-               kbd_inter_running = FALSE;
-               if (!ssh2_pkt_getbool()) {
+               ssh_pkt_getstring(pktin, &methods, &methlen);
+               s->kbd_inter_running = FALSE;
+               if (!ssh2_pkt_getbool(pktin)) {
                    /*
                     * We have received an unequivocal Access
                     * Denied. This can translate to a variety of
@@ -4276,40 +6242,45 @@ static void do_ssh2_authconn(unsigned char *in, int inlen, int ispkt)
                     * Additionally, if we'd just tried password
                     * authentication, we should break out of this
                     * whole loop so as to go back to the username
-                    * prompt.
+                    * prompt (iff we're configured to allow
+                    * username change attempts).
                     */
-                   if (type == AUTH_TYPE_NONE) {
+                   if (s->type == AUTH_TYPE_NONE) {
                        /* do nothing */
-                   } else if (type == AUTH_TYPE_PUBLICKEY_OFFER_LOUD ||
-                              type == AUTH_TYPE_PUBLICKEY_OFFER_QUIET) {
-                       if (type == AUTH_TYPE_PUBLICKEY_OFFER_LOUD)
-                           c_write_str("Server refused our key\r\n");
+                   } else if (s->type == AUTH_TYPE_PUBLICKEY_OFFER_LOUD ||
+                              s->type == AUTH_TYPE_PUBLICKEY_OFFER_QUIET) {
+                       if (s->type == AUTH_TYPE_PUBLICKEY_OFFER_LOUD)
+                           c_write_str(ssh, "Server refused our key\r\n");
                        logevent("Server refused public key");
-                   } else if (type == AUTH_TYPE_KEYBOARD_INTERACTIVE_QUIET) {
+                   } else if (s->type==AUTH_TYPE_KEYBOARD_INTERACTIVE_QUIET) {
                        /* server declined keyboard-interactive; ignore */
                    } else {
-                       c_write_str("Access denied\r\n");
+                       c_write_str(ssh, "Access denied\r\n");
                        logevent("Access denied");
-                       if (type == AUTH_TYPE_PASSWORD) {
-                           we_are_in = FALSE;
+                       if (s->type == AUTH_TYPE_PASSWORD &&
+                           ssh->cfg.change_username) {
+                           /* XXX perhaps we should allow
+                            * keyboard-interactive to do this too? */
+                           s->we_are_in = FALSE;
                            break;
                        }
                    }
                } else {
-                   c_write_str("Further authentication required\r\n");
+                   c_write_str(ssh, "Further authentication required\r\n");
                    logevent("Further authentication required");
                }
 
-               can_pubkey =
+               s->can_pubkey =
                    in_commasep_string("publickey", methods, methlen);
-               can_passwd =
+               s->can_passwd =
                    in_commasep_string("password", methods, methlen);
-               can_keyb_inter = cfg.try_ki_auth &&
+               s->can_keyb_inter = ssh->cfg.try_ki_auth &&
                    in_commasep_string("keyboard-interactive", methods, methlen);
            }
 
-           method = 0;
-           ssh_pkt_ctx &= ~SSH2_PKTCTX_AUTH_MASK;
+           s->method = 0;
+           ssh->pkt_ctx &= ~SSH2_PKTCTX_AUTH_MASK;
+           s->need_pw = FALSE;
 
            /*
             * Most password/passphrase prompts will be
@@ -4317,163 +6288,192 @@ static void do_ssh2_authconn(unsigned char *in, int inlen, int ispkt)
             * Exception is that some keyboard-interactive prompts
             * can be echoing, in which case we'll set this to 1.
             */
-           echo = 0;
+           s->echo = 0;
 
-           if (!method && can_pubkey && agent_exists() && !tried_agent) {
+           if (!s->method && s->can_pubkey &&
+               agent_exists() && !s->tried_agent) {
                /*
                 * Attempt public-key authentication using Pageant.
                 */
-               static unsigned char request[5], *response, *p;
-               static int responselen;
-               static int i, nkeys;
-               static int authed = FALSE;
                void *r;
+               s->authed = FALSE;
 
-               ssh_pkt_ctx &= ~SSH2_PKTCTX_AUTH_MASK;
-               ssh_pkt_ctx |= SSH2_PKTCTX_PUBLICKEY;
+               ssh->pkt_ctx &= ~SSH2_PKTCTX_AUTH_MASK;
+               ssh->pkt_ctx |= SSH2_PKTCTX_PUBLICKEY;
 
-               tried_agent = TRUE;
+               s->tried_agent = TRUE;
 
                logevent("Pageant is running. Requesting keys.");
 
                /* Request the keys held by the agent. */
-               PUT_32BIT(request, 1);
-               request[4] = SSH2_AGENTC_REQUEST_IDENTITIES;
-               agent_query(request, 5, &r, &responselen);
-               response = (unsigned char *) r;
-               if (response && responselen >= 5 &&
-                   response[4] == SSH2_AGENT_IDENTITIES_ANSWER) {
-                   p = response + 5;
-                   nkeys = GET_32BIT(p);
-                   p += 4;
+               PUT_32BIT(s->request, 1);
+               s->request[4] = SSH2_AGENTC_REQUEST_IDENTITIES;
+               if (!agent_query(s->request, 5, &r, &s->responselen,
+                                ssh_agent_callback, ssh)) {
+                   do {
+                       crReturnV;
+                       if (pktin) {
+                           bombout(("Unexpected data from server while"
+                                    " waiting for agent response"));
+                           crStopV;
+                       }
+                   } while (pktin || inlen > 0);
+                   r = ssh->agent_response;
+                   s->responselen = ssh->agent_response_len;
+               }
+               s->response = (unsigned char *) r;
+               if (s->response && s->responselen >= 5 &&
+                   s->response[4] == SSH2_AGENT_IDENTITIES_ANSWER) {
+                   s->p = s->response + 5;
+                   s->nkeys = GET_32BIT(s->p);
+                   s->p += 4;
                    {
                        char buf[64];
-                       sprintf(buf, "Pageant has %d SSH2 keys", nkeys);
+                       sprintf(buf, "Pageant has %d SSH2 keys", s->nkeys);
                        logevent(buf);
                    }
-                   for (i = 0; i < nkeys; i++) {
-                       static char *pkblob, *alg, *commentp;
-                       static int pklen, alglen, commentlen;
-                       static int siglen, retlen, len;
-                       static char *q, *agentreq, *ret;
+                   for (s->keyi = 0; s->keyi < s->nkeys; s->keyi++) {
                        void *vret;
 
                        {
                            char buf[64];
-                           sprintf(buf, "Trying Pageant key #%d", i);
+                           sprintf(buf, "Trying Pageant key #%d", s->keyi);
                            logevent(buf);
                        }
-                       pklen = GET_32BIT(p);
-                       p += 4;
-                       if (publickey_blob &&
-                           pklen == publickey_bloblen &&
-                           !memcmp(p, publickey_blob, publickey_bloblen)) {
+                       s->pklen = GET_32BIT(s->p);
+                       s->p += 4;
+                       if (s->publickey_blob &&
+                           s->pklen == s->publickey_bloblen &&
+                           !memcmp(s->p, s->publickey_blob,
+                                   s->publickey_bloblen)) {
                            logevent("This key matches configured key file");
-                           tried_pubkey_config = 1;
+                           s->tried_pubkey_config = 1;
                        }
-                       pkblob = p;
-                       p += pklen;
-                       alglen = GET_32BIT(pkblob);
-                       alg = pkblob + 4;
-                       commentlen = GET_32BIT(p);
-                       p += 4;
-                       commentp = p;
-                       p += commentlen;
-                       ssh2_pkt_init(SSH2_MSG_USERAUTH_REQUEST);
-                       ssh2_pkt_addstring(username);
-                       ssh2_pkt_addstring("ssh-connection");   /* service requested */
-                       ssh2_pkt_addstring("publickey");        /* method */
-                       ssh2_pkt_addbool(FALSE);        /* no signature included */
-                       ssh2_pkt_addstring_start();
-                       ssh2_pkt_addstring_data(alg, alglen);
-                       ssh2_pkt_addstring_start();
-                       ssh2_pkt_addstring_data(pkblob, pklen);
-                       ssh2_pkt_send();
-
-                       crWaitUntilV(ispkt);
-                       if (pktin.type != SSH2_MSG_USERAUTH_PK_OK) {
+                       s->pkblob = (char *)s->p;
+                       s->p += s->pklen;
+                       s->alglen = GET_32BIT(s->pkblob);
+                       s->alg = s->pkblob + 4;
+                       s->commentlen = GET_32BIT(s->p);
+                       s->p += 4;
+                       s->commentp = (char *)s->p;
+                       s->p += s->commentlen;
+                       s->pktout = ssh2_pkt_init(SSH2_MSG_USERAUTH_REQUEST);
+                       ssh2_pkt_addstring(s->pktout, s->username);
+                       ssh2_pkt_addstring(s->pktout, "ssh-connection");        /* service requested */
+                       ssh2_pkt_addstring(s->pktout, "publickey");     /* method */
+                       ssh2_pkt_addbool(s->pktout, FALSE);     /* no signature included */
+                       ssh2_pkt_addstring_start(s->pktout);
+                       ssh2_pkt_addstring_data(s->pktout, s->alg, s->alglen);
+                       ssh2_pkt_addstring_start(s->pktout);
+                       ssh2_pkt_addstring_data(s->pktout, s->pkblob, s->pklen);
+                       ssh2_pkt_send(ssh, s->pktout);
+
+                       crWaitUntilV(pktin);
+                       if (pktin->type != SSH2_MSG_USERAUTH_PK_OK) {
                            logevent("Key refused");
                            continue;
                        }
 
                        if (flags & FLAG_VERBOSE) {
-                           c_write_str
-                               ("Authenticating with public key \"");
-                           c_write(commentp, commentlen);
-                           c_write_str("\" from agent\r\n");
+                           c_write_str(ssh, "Authenticating with "
+                                       "public key \"");
+                           c_write(ssh, s->commentp, s->commentlen);
+                           c_write_str(ssh, "\" from agent\r\n");
                        }
 
                        /*
                         * Server is willing to accept the key.
                         * Construct a SIGN_REQUEST.
                         */
-                       ssh2_pkt_init(SSH2_MSG_USERAUTH_REQUEST);
-                       ssh2_pkt_addstring(username);
-                       ssh2_pkt_addstring("ssh-connection");   /* service requested */
-                       ssh2_pkt_addstring("publickey");        /* method */
-                       ssh2_pkt_addbool(TRUE);
-                       ssh2_pkt_addstring_start();
-                       ssh2_pkt_addstring_data(alg, alglen);
-                       ssh2_pkt_addstring_start();
-                       ssh2_pkt_addstring_data(pkblob, pklen);
-
-                       siglen = pktout.length - 5 + 4 + 20;
-                       len = 1;       /* message type */
-                       len += 4 + pklen;       /* key blob */
-                       len += 4 + siglen;      /* data to sign */
-                       len += 4;      /* flags */
-                       agentreq = smalloc(4 + len);
-                       PUT_32BIT(agentreq, len);
-                       q = agentreq + 4;
-                       *q++ = SSH2_AGENTC_SIGN_REQUEST;
-                       PUT_32BIT(q, pklen);
-                       q += 4;
-                       memcpy(q, pkblob, pklen);
-                       q += pklen;
-                       PUT_32BIT(q, siglen);
-                       q += 4;
+                       s->pktout = ssh2_pkt_init(SSH2_MSG_USERAUTH_REQUEST);
+                       ssh2_pkt_addstring(s->pktout, s->username);
+                       ssh2_pkt_addstring(s->pktout, "ssh-connection");        /* service requested */
+                       ssh2_pkt_addstring(s->pktout, "publickey");     /* method */
+                       ssh2_pkt_addbool(s->pktout, TRUE);
+                       ssh2_pkt_addstring_start(s->pktout);
+                       ssh2_pkt_addstring_data(s->pktout, s->alg, s->alglen);
+                       ssh2_pkt_addstring_start(s->pktout);
+                       ssh2_pkt_addstring_data(s->pktout, s->pkblob, s->pklen);
+
+                       s->siglen = s->pktout->length - 5 + 4 + 20;
+                        if (ssh->remote_bugs & BUG_SSH2_PK_SESSIONID)
+                            s->siglen -= 4;
+                       s->len = 1;       /* message type */
+                       s->len += 4 + s->pklen; /* key blob */
+                       s->len += 4 + s->siglen;        /* data to sign */
+                       s->len += 4;      /* flags */
+                       s->agentreq = snewn(4 + s->len, char);
+                       PUT_32BIT(s->agentreq, s->len);
+                       s->q = s->agentreq + 4;
+                       *s->q++ = SSH2_AGENTC_SIGN_REQUEST;
+                       PUT_32BIT(s->q, s->pklen);
+                       s->q += 4;
+                       memcpy(s->q, s->pkblob, s->pklen);
+                       s->q += s->pklen;
+                       PUT_32BIT(s->q, s->siglen);
+                       s->q += 4;
                        /* Now the data to be signed... */
-                       PUT_32BIT(q, 20);
-                       q += 4;
-                       memcpy(q, ssh2_session_id, 20);
-                       q += 20;
-                       memcpy(q, pktout.data + 5, pktout.length - 5);
-                       q += pktout.length - 5;
+                        if (!(ssh->remote_bugs & BUG_SSH2_PK_SESSIONID)) {
+                            PUT_32BIT(s->q, 20);
+                            s->q += 4;
+                        }
+                       memcpy(s->q, ssh->v2_session_id, 20);
+                       s->q += 20;
+                       memcpy(s->q, s->pktout->data + 5,
+                              s->pktout->length - 5);
+                       s->q += s->pktout->length - 5;
                        /* And finally the (zero) flags word. */
-                       PUT_32BIT(q, 0);
-                       agent_query(agentreq, len + 4, &vret, &retlen);
-                       ret = vret;
-                       sfree(agentreq);
-                       if (ret) {
-                           if (ret[4] == SSH2_AGENT_SIGN_RESPONSE) {
+                       PUT_32BIT(s->q, 0);
+                       if (!agent_query(s->agentreq, s->len + 4,
+                                        &vret, &s->retlen,
+                                        ssh_agent_callback, ssh)) {
+                           do {
+                               crReturnV;
+                               if (pktin) {
+                                   bombout(("Unexpected data from server"
+                                            " while waiting for agent"
+                                            " response"));
+                                   crStopV;
+                               }
+                           } while (pktin || inlen > 0);
+                           vret = ssh->agent_response;
+                           s->retlen = ssh->agent_response_len;
+                       }
+                       s->ret = vret;
+                       sfree(s->agentreq);
+                       if (s->ret) {
+                           if (s->ret[4] == SSH2_AGENT_SIGN_RESPONSE) {
                                logevent("Sending Pageant's response");
-                               ssh2_add_sigblob(pkblob, pklen,
-                                                ret + 9, GET_32BIT(ret + 5));
-                               ssh2_pkt_send();
-                               authed = TRUE;
+                               ssh2_add_sigblob(ssh, s->pktout,
+                                                s->pkblob, s->pklen,
+                                                s->ret + 9,
+                                                GET_32BIT(s->ret + 5));
+                               ssh2_pkt_send(ssh, s->pktout);
+                               s->authed = TRUE;
                                break;
                            } else {
                                logevent
                                    ("Pageant failed to answer challenge");
-                               sfree(ret);
+                               sfree(s->ret);
                            }
                        }
                    }
-                   if (authed)
+                   if (s->authed)
                        continue;
                }
+               sfree(s->response);
            }
 
-           if (!method && can_pubkey && publickey_blob
-               && !tried_pubkey_config) {
+           if (!s->method && s->can_pubkey && s->publickey_blob
+               && !s->tried_pubkey_config) {
                unsigned char *pub_blob;
                char *algorithm, *comment;
                int pub_blob_len;
 
-               tried_pubkey_config = TRUE;
+               s->tried_pubkey_config = TRUE;
 
-               ssh_pkt_ctx &= ~SSH2_PKTCTX_AUTH_MASK;
-               ssh_pkt_ctx |= SSH2_PKTCTX_PUBLICKEY;
+               ssh->pkt_ctx &= ~SSH2_PKTCTX_AUTH_MASK;
+               ssh->pkt_ctx |= SSH2_PKTCTX_PUBLICKEY;
 
                /*
                 * Try the public key supplied in the configuration.
@@ -4481,24 +6481,28 @@ static void do_ssh2_authconn(unsigned char *in, int inlen, int ispkt)
                 * First, offer the public blob to see if the server is
                 * willing to accept it.
                 */
-               pub_blob = ssh2_userkey_loadpub(cfg.keyfile, &algorithm,
-                                               &pub_blob_len);
+               pub_blob =
+                   (unsigned char *)ssh2_userkey_loadpub(&ssh->cfg.keyfile,
+                                                         &algorithm,
+                                                         &pub_blob_len,
+                                                         NULL);
                if (pub_blob) {
-                   ssh2_pkt_init(SSH2_MSG_USERAUTH_REQUEST);
-                   ssh2_pkt_addstring(username);
-                   ssh2_pkt_addstring("ssh-connection");       /* service requested */
-                   ssh2_pkt_addstring("publickey");    /* method */
-                   ssh2_pkt_addbool(FALSE);    /* no signature included */
-                   ssh2_pkt_addstring(algorithm);
-                   ssh2_pkt_addstring_start();
-                   ssh2_pkt_addstring_data(pub_blob, pub_blob_len);
-                   ssh2_pkt_send();
-                   logevent("Offered public key");     /* FIXME */
-
-                   crWaitUntilV(ispkt);
-                   if (pktin.type != SSH2_MSG_USERAUTH_PK_OK) {
-                       gotit = TRUE;
-                       type = AUTH_TYPE_PUBLICKEY_OFFER_LOUD;
+                   s->pktout = ssh2_pkt_init(SSH2_MSG_USERAUTH_REQUEST);
+                   ssh2_pkt_addstring(s->pktout, s->username);
+                   ssh2_pkt_addstring(s->pktout, "ssh-connection");    /* service requested */
+                   ssh2_pkt_addstring(s->pktout, "publickey"); /* method */
+                   ssh2_pkt_addbool(s->pktout, FALSE); /* no signature included */
+                   ssh2_pkt_addstring(s->pktout, algorithm);
+                   ssh2_pkt_addstring_start(s->pktout);
+                   ssh2_pkt_addstring_data(s->pktout, (char *)pub_blob,
+                                           pub_blob_len);
+                   ssh2_pkt_send(ssh, s->pktout);
+                   logevent("Offered public key");
+
+                   crWaitUntilV(pktin);
+                   if (pktin->type != SSH2_MSG_USERAUTH_PK_OK) {
+                       s->gotit = TRUE;
+                       s->type = AUTH_TYPE_PUBLICKEY_OFFER_LOUD;
                        continue;      /* key refused; give up on it */
                    }
 
@@ -4507,59 +6511,61 @@ static void do_ssh2_authconn(unsigned char *in, int inlen, int ispkt)
                     * Actually attempt a serious authentication using
                     * the key.
                     */
-                   if (ssh2_userkey_encrypted(cfg.keyfile, &comment)) {
-                       sprintf(pwprompt,
+                   if (ssh2_userkey_encrypted(&ssh->cfg.keyfile, &comment)) {
+                       sprintf(s->pwprompt,
                                "Passphrase for key \"%.100s\": ",
                                comment);
-                       need_pw = TRUE;
+                       s->need_pw = TRUE;
                    } else {
-                       need_pw = FALSE;
+                       s->need_pw = FALSE;
+                   }
+                   if (flags & FLAG_VERBOSE) {
+                       c_write_str(ssh, "Authenticating with public key \"");
+                       c_write_str(ssh, comment);
+                       c_write_str(ssh, "\"\r\n");
                    }
-                   c_write_str("Authenticating with public key \"");
-                   c_write_str(comment);
-                   c_write_str("\"\r\n");
-                   method = AUTH_PUBLICKEY_FILE;
+                   s->method = AUTH_PUBLICKEY_FILE;
                }
            }
 
-           if (!method && can_keyb_inter && !tried_keyb_inter) {
-               method = AUTH_KEYBOARD_INTERACTIVE;
-               type = AUTH_TYPE_KEYBOARD_INTERACTIVE;
-               tried_keyb_inter = TRUE;
-
-               ssh_pkt_ctx &= ~SSH2_PKTCTX_AUTH_MASK;
-               ssh_pkt_ctx |= SSH2_PKTCTX_KBDINTER;
-
-               ssh2_pkt_init(SSH2_MSG_USERAUTH_REQUEST);
-               ssh2_pkt_addstring(username);
-               ssh2_pkt_addstring("ssh-connection");   /* service requested */
-               ssh2_pkt_addstring("keyboard-interactive");     /* method */
-               ssh2_pkt_addstring(""); /* lang */
-               ssh2_pkt_addstring("");
-               ssh2_pkt_send();
-
-               crWaitUntilV(ispkt);
-               if (pktin.type != SSH2_MSG_USERAUTH_INFO_REQUEST) {
-                   if (pktin.type == SSH2_MSG_USERAUTH_FAILURE)
-                       gotit = TRUE;
+           if (!s->method && s->can_keyb_inter && !s->kbd_inter_refused &&
+               !s->kbd_inter_running) {
+               s->method = AUTH_KEYBOARD_INTERACTIVE;
+               s->type = AUTH_TYPE_KEYBOARD_INTERACTIVE;
+
+               ssh->pkt_ctx &= ~SSH2_PKTCTX_AUTH_MASK;
+               ssh->pkt_ctx |= SSH2_PKTCTX_KBDINTER;
+
+               s->pktout = ssh2_pkt_init(SSH2_MSG_USERAUTH_REQUEST);
+               ssh2_pkt_addstring(s->pktout, s->username);
+               ssh2_pkt_addstring(s->pktout, "ssh-connection");        /* service requested */
+               ssh2_pkt_addstring(s->pktout, "keyboard-interactive");  /* method */
+               ssh2_pkt_addstring(s->pktout, ""); /* lang */
+               ssh2_pkt_addstring(s->pktout, "");
+               ssh2_pkt_send(ssh, s->pktout);
+
+               crWaitUntilV(pktin);
+               if (pktin->type != SSH2_MSG_USERAUTH_INFO_REQUEST) {
+                   if (pktin->type == SSH2_MSG_USERAUTH_FAILURE)
+                       s->gotit = TRUE;
                    logevent("Keyboard-interactive authentication refused");
-                   type = AUTH_TYPE_KEYBOARD_INTERACTIVE_QUIET;
+                   s->type = AUTH_TYPE_KEYBOARD_INTERACTIVE_QUIET;
+                   s->kbd_inter_refused = TRUE; /* don't try it again */
                    continue;
                }
 
-               kbd_inter_running = TRUE;
-               curr_prompt = 0;
+               s->kbd_inter_running = TRUE;
+               s->curr_prompt = 0;
            }
 
-           if (kbd_inter_running) {
-               method = AUTH_KEYBOARD_INTERACTIVE;
-               type = AUTH_TYPE_KEYBOARD_INTERACTIVE;
-               tried_keyb_inter = TRUE;
+           if (s->kbd_inter_running) {
+               s->method = AUTH_KEYBOARD_INTERACTIVE;
+               s->type = AUTH_TYPE_KEYBOARD_INTERACTIVE;
 
-               ssh_pkt_ctx &= ~SSH2_PKTCTX_AUTH_MASK;
-               ssh_pkt_ctx |= SSH2_PKTCTX_KBDINTER;
+               ssh->pkt_ctx &= ~SSH2_PKTCTX_AUTH_MASK;
+               ssh->pkt_ctx |= SSH2_PKTCTX_KBDINTER;
 
-               if (curr_prompt == 0) {
+               if (s->curr_prompt == 0) {
                    /*
                     * We've got a fresh USERAUTH_INFO_REQUEST.
                     * Display header data, and start going through
@@ -4568,129 +6574,144 @@ static void do_ssh2_authconn(unsigned char *in, int inlen, int ispkt)
                    char *name, *inst, *lang;
                    int name_len, inst_len, lang_len;
 
-                   ssh2_pkt_getstring(&name, &name_len);
-                   ssh2_pkt_getstring(&inst, &inst_len);
-                   ssh2_pkt_getstring(&lang, &lang_len);
+                   ssh_pkt_getstring(pktin, &name, &name_len);
+                   ssh_pkt_getstring(pktin, &inst, &inst_len);
+                   ssh_pkt_getstring(pktin, &lang, &lang_len);
                    if (name_len > 0) {
-                       c_write_untrusted(name, name_len);
-                       c_write_str("\r\n");
+                       c_write_untrusted(ssh, name, name_len);
+                       c_write_str(ssh, "\r\n");
                    }
                    if (inst_len > 0) {
-                       c_write_untrusted(inst, inst_len);
-                       c_write_str("\r\n");
+                       c_write_untrusted(ssh, inst, inst_len);
+                       c_write_str(ssh, "\r\n");
                    }
-                   num_prompts = ssh2_pkt_getuint32();
+                   s->num_prompts = ssh_pkt_getuint32(pktin);
                }
 
                /*
                 * If there are prompts remaining in the packet,
                 * display one and get a response.
                 */
-               if (curr_prompt < num_prompts) {
+               if (s->curr_prompt < s->num_prompts) {
                    char *prompt;
                    int prompt_len;
 
-                   ssh2_pkt_getstring(&prompt, &prompt_len);
+                   ssh_pkt_getstring(pktin, &prompt, &prompt_len);
                    if (prompt_len > 0) {
-                       strncpy(pwprompt, prompt, sizeof(pwprompt));
-                       pwprompt[prompt_len < sizeof(pwprompt) ?
-                                prompt_len : sizeof(pwprompt)-1] = '\0';
+                       static const char trunc[] = "<prompt truncated>: ";
+                       static const int prlen = sizeof(s->pwprompt) -
+                                                lenof(trunc);
+                       if (prompt_len > prlen) {
+                           memcpy(s->pwprompt, prompt, prlen);
+                           strcpy(s->pwprompt + prlen, trunc);
+                       } else {
+                           memcpy(s->pwprompt, prompt, prompt_len);
+                           s->pwprompt[prompt_len] = '\0';
+                       }
                    } else {
-                       strcpy(pwprompt,
+                       strcpy(s->pwprompt,
                               "<server failed to send prompt>: ");
                    }
-                   echo = ssh2_pkt_getbool();
-                   need_pw = TRUE;
+                   s->echo = ssh2_pkt_getbool(pktin);
+                   s->need_pw = TRUE;
                } else
-                   need_pw = FALSE;
+                   s->need_pw = FALSE;
            }
 
-           if (!method && can_passwd) {
-               method = AUTH_PASSWORD;
-               ssh_pkt_ctx &= ~SSH2_PKTCTX_AUTH_MASK;
-               ssh_pkt_ctx |= SSH2_PKTCTX_PASSWORD;
-               sprintf(pwprompt, "%.90s@%.90s's password: ", username,
-                       savedhost);
-               need_pw = TRUE;
+           if (!s->method && s->can_passwd) {
+               s->method = AUTH_PASSWORD;
+               ssh->pkt_ctx &= ~SSH2_PKTCTX_AUTH_MASK;
+               ssh->pkt_ctx |= SSH2_PKTCTX_PASSWORD;
+               sprintf(s->pwprompt, "%.90s@%.90s's password: ", s->username,
+                       ssh->savedhost);
+               s->need_pw = TRUE;
            }
 
-           if (need_pw) {
+           if (s->need_pw) {
                if (ssh_get_line) {
-                   if (!ssh_get_line(pwprompt, password,
-                                     sizeof(password), TRUE)) {
+                   if (!ssh_get_line(s->pwprompt, s->password,
+                                     sizeof(s->password), TRUE)) {
                        /*
                         * get_line failed to get a password (for
                         * example because one was supplied on the
                         * command line which has already failed to
                         * work). Terminate.
                         */
-                       ssh2_pkt_init(SSH2_MSG_DISCONNECT);
-                       ssh2_pkt_adduint32(SSH2_DISCONNECT_BY_APPLICATION);
-                       ssh2_pkt_addstring
-                           ("No more passwords available to try");
-                       ssh2_pkt_addstring("en");       /* language tag */
-                       ssh2_pkt_send();
+                       s->pktout = ssh2_pkt_init(SSH2_MSG_DISCONNECT);
+                       ssh2_pkt_adduint32(s->pktout,SSH2_DISCONNECT_BY_APPLICATION);
+                       ssh2_pkt_addstring(s->pktout, "No more passwords available"
+                                          " to try");
+                       ssh2_pkt_addstring(s->pktout, "en");    /* language tag */
+                       ssh2_pkt_send_noqueue(ssh, s->pktout);
                        logevent("Unable to authenticate");
-                       connection_fatal("Unable to authenticate");
-                       ssh_state = SSH_STATE_CLOSED;
-                       crReturnV;
+                       connection_fatal(ssh->frontend,
+                                        "Unable to authenticate");
+                       ssh->close_expected = TRUE;
+                        ssh_closing((Plug)ssh, NULL, 0, 0);
+                       crStopV;
                    }
                } else {
-                   static int ret;
-                   c_write_untrusted(pwprompt, strlen(pwprompt));
-                   ssh_send_ok = 1;
+                   int ret;           /* need not be saved across crReturn */
+                   c_write_untrusted(ssh, s->pwprompt, strlen(s->pwprompt));
+                   ssh->send_ok = 1;
 
-                   setup_userpass_input(password, sizeof(password), echo);
+                   setup_userpass_input(ssh, s->password,
+                                        sizeof(s->password), s->echo);
                    do {
-                       crWaitUntilV(!ispkt);
-                       ret = process_userpass_input(in, inlen);
+                       crWaitUntilV(!pktin);
+                       ret = process_userpass_input(ssh, in, inlen);
                    } while (ret == 0);
                    if (ret < 0)
                        cleanup_exit(0);
-                   c_write_str("\r\n");
+                   c_write_str(ssh, "\r\n");
                }
            }
 
-           if (method == AUTH_PUBLICKEY_FILE) {
+           if (s->method == AUTH_PUBLICKEY_FILE) {
                /*
                 * We have our passphrase. Now try the actual authentication.
                 */
                struct ssh2_userkey *key;
+               const char *error = NULL;
 
-               key = ssh2_load_userkey(cfg.keyfile, password);
+               key = ssh2_load_userkey(&ssh->cfg.keyfile, s->password,
+                                       &error);
                if (key == SSH2_WRONG_PASSPHRASE || key == NULL) {
                    if (key == SSH2_WRONG_PASSPHRASE) {
-                       c_write_str("Wrong passphrase\r\n");
-                       tried_pubkey_config = FALSE;
+                       c_write_str(ssh, "Wrong passphrase\r\n");
+                       s->tried_pubkey_config = FALSE;
                    } else {
-                       c_write_str("Unable to load private key\r\n");
-                       tried_pubkey_config = TRUE;
+                       c_write_str(ssh, "Unable to load private key (");
+                       c_write_str(ssh, error);
+                       c_write_str(ssh, ")\r\n");
+                       s->tried_pubkey_config = TRUE;
                    }
                    /* Send a spurious AUTH_NONE to return to the top. */
-                   ssh2_pkt_init(SSH2_MSG_USERAUTH_REQUEST);
-                   ssh2_pkt_addstring(username);
-                   ssh2_pkt_addstring("ssh-connection");       /* service requested */
-                   ssh2_pkt_addstring("none"); /* method */
-                   ssh2_pkt_send();
-                   type = AUTH_TYPE_NONE;
+                   s->pktout = ssh2_pkt_init(SSH2_MSG_USERAUTH_REQUEST);
+                   ssh2_pkt_addstring(s->pktout, s->username);
+                   ssh2_pkt_addstring(s->pktout, "ssh-connection");    /* service requested */
+                   ssh2_pkt_addstring(s->pktout, "none");      /* method */
+                   ssh2_pkt_send(ssh, s->pktout);
+                   s->type = AUTH_TYPE_NONE;
                } else {
                    unsigned char *pkblob, *sigblob, *sigdata;
                    int pkblob_len, sigblob_len, sigdata_len;
+                    int p;
 
                    /*
                     * We have loaded the private key and the server
                     * has announced that it's willing to accept it.
                     * Hallelujah. Generate a signature and send it.
                     */
-                   ssh2_pkt_init(SSH2_MSG_USERAUTH_REQUEST);
-                   ssh2_pkt_addstring(username);
-                   ssh2_pkt_addstring("ssh-connection");       /* service requested */
-                   ssh2_pkt_addstring("publickey");    /* method */
-                   ssh2_pkt_addbool(TRUE);
-                   ssh2_pkt_addstring(key->alg->name);
+                   s->pktout = ssh2_pkt_init(SSH2_MSG_USERAUTH_REQUEST);
+                   ssh2_pkt_addstring(s->pktout, s->username);
+                   ssh2_pkt_addstring(s->pktout, "ssh-connection");    /* service requested */
+                   ssh2_pkt_addstring(s->pktout, "publickey"); /* method */
+                   ssh2_pkt_addbool(s->pktout, TRUE);
+                   ssh2_pkt_addstring(s->pktout, key->alg->name);
                    pkblob = key->alg->public_blob(key->data, &pkblob_len);
-                   ssh2_pkt_addstring_start();
-                   ssh2_pkt_addstring_data(pkblob, pkblob_len);
+                   ssh2_pkt_addstring_start(s->pktout);
+                   ssh2_pkt_addstring_data(s->pktout, (char *)pkblob, pkblob_len);
 
                    /*
                     * The data to be signed is:
@@ -4700,24 +6721,33 @@ static void do_ssh2_authconn(unsigned char *in, int inlen, int ispkt)
                     * followed by everything so far placed in the
                     * outgoing packet.
                     */
-                   sigdata_len = pktout.length - 5 + 4 + 20;
-                   sigdata = smalloc(sigdata_len);
-                   PUT_32BIT(sigdata, 20);
-                   memcpy(sigdata + 4, ssh2_session_id, 20);
-                   memcpy(sigdata + 24, pktout.data + 5,
-                          pktout.length - 5);
-                   sigblob = key->alg->sign(key->data, sigdata,
+                   sigdata_len = s->pktout->length - 5 + 4 + 20;
+                    if (ssh->remote_bugs & BUG_SSH2_PK_SESSIONID)
+                        sigdata_len -= 4;
+                   sigdata = snewn(sigdata_len, unsigned char);
+                    p = 0;
+                    if (!(ssh->remote_bugs & BUG_SSH2_PK_SESSIONID)) {
+                        PUT_32BIT(sigdata+p, 20);
+                        p += 4;
+                    }
+                   memcpy(sigdata+p, ssh->v2_session_id, 20); p += 20;
+                   memcpy(sigdata+p, s->pktout->data + 5,
+                          s->pktout->length - 5);
+                    p += s->pktout->length - 5;
+                    assert(p == sigdata_len);
+                   sigblob = key->alg->sign(key->data, (char *)sigdata,
                                             sigdata_len, &sigblob_len);
-                   ssh2_add_sigblob(pkblob, pkblob_len,
+                   ssh2_add_sigblob(ssh, s->pktout, pkblob, pkblob_len,
                                     sigblob, sigblob_len);
                    sfree(pkblob);
                    sfree(sigblob);
                    sfree(sigdata);
 
-                   ssh2_pkt_send();
-                   type = AUTH_TYPE_PUBLICKEY;
+                   ssh2_pkt_send(ssh, s->pktout);
+                   s->type = AUTH_TYPE_PUBLICKEY;
+                   key->alg->freekey(key->data);
                }
-           } else if (method == AUTH_PASSWORD) {
+           } else if (s->method == AUTH_PASSWORD) {
                /*
                 * We send the password packet lumped tightly together with
                 * an SSH_MSG_IGNORE packet. The IGNORE packet contains a
@@ -4732,26 +6762,29 @@ static void do_ssh2_authconn(unsigned char *in, int inlen, int ispkt)
                 * that probably doesn't have much to worry about from
                 * people who find out how long their password is!
                 */
-               ssh2_pkt_init(SSH2_MSG_USERAUTH_REQUEST);
-               ssh2_pkt_addstring(username);
-               ssh2_pkt_addstring("ssh-connection");   /* service requested */
-               ssh2_pkt_addstring("password");
-               ssh2_pkt_addbool(FALSE);
-               ssh2_pkt_addstring(password);
-               ssh2_pkt_defer();
+               s->pktout = ssh2_pkt_init(SSH2_MSG_USERAUTH_REQUEST);
+               ssh2_pkt_addstring(s->pktout, s->username);
+               ssh2_pkt_addstring(s->pktout, "ssh-connection");        /* service requested */
+               ssh2_pkt_addstring(s->pktout, "password");
+               ssh2_pkt_addbool(s->pktout, FALSE);
+               dont_log_password(ssh, s->pktout, PKTLOG_BLANK);
+               ssh2_pkt_addstring(s->pktout, s->password);
+               memset(s->password, 0, sizeof(s->password));
+               end_log_omission(ssh, s->pktout);
+               ssh2_pkt_defer(ssh, s->pktout);
                /*
                 * We'll include a string that's an exact multiple of the
                 * cipher block size. If the cipher is NULL for some
                 * reason, we don't do this trick at all because we gain
                 * nothing by it.
                 */
-               if (cscipher) {
+               if (ssh->cscipher) {
                    int stringlen, i;
 
-                   stringlen = (256 - deferred_len);
-                   stringlen += cscipher->blksize - 1;
-                   stringlen -= (stringlen % cscipher->blksize);
-                   if (cscomp) {
+                   stringlen = (256 - ssh->deferred_len);
+                   stringlen += ssh->cscipher->blksize - 1;
+                   stringlen -= (stringlen % ssh->cscipher->blksize);
+                   if (ssh->cscomp) {
                        /*
                         * Temporarily disable actual compression,
                         * so we can guarantee to get this string
@@ -4761,31 +6794,34 @@ static void do_ssh2_authconn(unsigned char *in, int inlen, int ispkt)
                         * bytes we should adjust our string length
                         * by.
                         */
-                       stringlen -= cscomp->disable_compression();
+                       stringlen -= 
+                           ssh->cscomp->disable_compression(ssh->cs_comp_ctx);
                    }
-                   ssh2_pkt_init(SSH2_MSG_IGNORE);
-                   ssh2_pkt_addstring_start();
+                   s->pktout = ssh2_pkt_init(SSH2_MSG_IGNORE);
+                   ssh2_pkt_addstring_start(s->pktout);
                    for (i = 0; i < stringlen; i++) {
                        char c = (char) random_byte();
-                       ssh2_pkt_addstring_data(&c, 1);
+                       ssh2_pkt_addstring_data(s->pktout, &c, 1);
                    }
-                   ssh2_pkt_defer();
+                   ssh2_pkt_defer(ssh, s->pktout);
                }
-               ssh_pkt_defersend();
+               ssh_pkt_defersend(ssh);
                logevent("Sent password");
-               type = AUTH_TYPE_PASSWORD;
-           } else if (method == AUTH_KEYBOARD_INTERACTIVE) {
-               if (curr_prompt == 0) {
-                   ssh2_pkt_init(SSH2_MSG_USERAUTH_INFO_RESPONSE);
-                   ssh2_pkt_adduint32(num_prompts);
+               s->type = AUTH_TYPE_PASSWORD;
+           } else if (s->method == AUTH_KEYBOARD_INTERACTIVE) {
+               if (s->curr_prompt == 0) {
+                   s->pktout = ssh2_pkt_init(SSH2_MSG_USERAUTH_INFO_RESPONSE);
+                   ssh2_pkt_adduint32(s->pktout, s->num_prompts);
                }
-               if (need_pw) {         /* only add pw if we just got one! */
-                   ssh2_pkt_addstring(password);
-                   memset(password, 0, sizeof(password));
-                   curr_prompt++;
+               if (s->need_pw) {      /* only add pw if we just got one! */
+                   dont_log_password(ssh, s->pktout, PKTLOG_BLANK);
+                   ssh2_pkt_addstring(s->pktout, s->password);
+                   memset(s->password, 0, sizeof(s->password));
+                   end_log_omission(ssh, s->pktout);
+                   s->curr_prompt++;
                }
-               if (curr_prompt >= num_prompts) {
-                   ssh2_pkt_send();
+               if (s->curr_prompt >= s->num_prompts) {
+                   ssh2_pkt_send(ssh, s->pktout);
                } else {
                    /*
                     * If there are prompts remaining, we set
@@ -4795,25 +6831,26 @@ static void do_ssh2_authconn(unsigned char *in, int inlen, int ispkt)
                     * prompt out of the existing packet. Funky or
                     * what?
                     */
-                   gotit = TRUE;
+                   s->gotit = TRUE;
                }
-               type = AUTH_TYPE_KEYBOARD_INTERACTIVE;
+               s->type = AUTH_TYPE_KEYBOARD_INTERACTIVE;
            } else {
-               c_write_str
-                   ("No supported authentication methods left to try!\r\n");
-               logevent
-                   ("No supported authentications offered. Disconnecting");
-               ssh2_pkt_init(SSH2_MSG_DISCONNECT);
-               ssh2_pkt_adduint32(SSH2_DISCONNECT_BY_APPLICATION);
-               ssh2_pkt_addstring
-                   ("No supported authentication methods available");
-               ssh2_pkt_addstring("en");       /* language tag */
-               ssh2_pkt_send();
-               ssh_state = SSH_STATE_CLOSED;
-               crReturnV;
+               c_write_str(ssh, "No supported authentication methods"
+                           " left to try!\r\n");
+               logevent("No supported authentications offered."
+                        " Disconnecting");
+               s->pktout = ssh2_pkt_init(SSH2_MSG_DISCONNECT);
+               ssh2_pkt_adduint32(s->pktout, SSH2_DISCONNECT_BY_APPLICATION);
+               ssh2_pkt_addstring(s->pktout, "No supported authentication"
+                                  " methods available");
+               ssh2_pkt_addstring(s->pktout, "en");    /* language tag */
+               ssh2_pkt_send_noqueue(ssh, s->pktout);
+               ssh->close_expected = TRUE;
+                ssh_closing((Plug)ssh, NULL, 0, 0);
+               crStopV;
            }
        }
-    } while (!we_are_in);
+    } while (!s->we_are_in);
 
     /*
      * Now we're authenticated for the connection protocol. The
@@ -4821,292 +6858,245 @@ static void do_ssh2_authconn(unsigned char *in, int inlen, int ispkt)
      * point; there's no need to send SERVICE_REQUEST.
      */
 
+    ssh->channels = newtree234(ssh_channelcmp);
+
     /*
-     * So now create a channel with a session in it.
+     * Set up handlers for some connection protocol messages, so we
+     * don't have to handle them repeatedly in this coroutine.
      */
-    ssh_channels = newtree234(ssh_channelcmp);
-    mainchan = smalloc(sizeof(struct ssh_channel));
-    mainchan->localid = alloc_channel_id();
-    ssh2_pkt_init(SSH2_MSG_CHANNEL_OPEN);
-    ssh2_pkt_addstring("session");
-    ssh2_pkt_adduint32(mainchan->localid);
-    mainchan->v.v2.locwindow = OUR_V2_WINSIZE;
-    ssh2_pkt_adduint32(mainchan->v.v2.locwindow);      /* our window size */
-    ssh2_pkt_adduint32(0x4000UL);      /* our max pkt size */
-    ssh2_pkt_send();
-    crWaitUntilV(ispkt);
-    if (pktin.type != SSH2_MSG_CHANNEL_OPEN_CONFIRMATION) {
-       bombout(("Server refused to open a session"));
-       crReturnV;
-       /* FIXME: error data comes back in FAILURE packet */
-    }
-    if (ssh2_pkt_getuint32() != mainchan->localid) {
-       bombout(("Server's channel confirmation cited wrong channel"));
-       crReturnV;
-    }
-    mainchan->remoteid = ssh2_pkt_getuint32();
-    mainchan->type = CHAN_MAINSESSION;
-    mainchan->closes = 0;
-    mainchan->v.v2.remwindow = ssh2_pkt_getuint32();
-    mainchan->v.v2.remmaxpkt = ssh2_pkt_getuint32();
-    bufchain_init(&mainchan->v.v2.outbuffer);
-    add234(ssh_channels, mainchan);
-    logevent("Opened channel for session");
+    ssh->packet_dispatch[SSH2_MSG_CHANNEL_WINDOW_ADJUST] =
+       ssh2_msg_channel_window_adjust;
+    ssh->packet_dispatch[SSH2_MSG_GLOBAL_REQUEST] =
+       ssh2_msg_global_request;
+
+    /*
+     * Create the main session channel.
+     */
+    if (!ssh->cfg.ssh_no_shell) {
+       ssh->mainchan = snew(struct ssh_channel);
+       ssh->mainchan->ssh = ssh;
+       ssh->mainchan->localid = alloc_channel_id(ssh);
+       s->pktout = ssh2_pkt_init(SSH2_MSG_CHANNEL_OPEN);
+       ssh2_pkt_addstring(s->pktout, "session");
+       ssh2_pkt_adduint32(s->pktout, ssh->mainchan->localid);
+       ssh->mainchan->v.v2.locwindow = OUR_V2_WINSIZE;
+       ssh2_pkt_adduint32(s->pktout, ssh->mainchan->v.v2.locwindow);/* our window size */
+       ssh2_pkt_adduint32(s->pktout, OUR_V2_MAXPKT);    /* our max pkt size */
+       ssh2_pkt_send(ssh, s->pktout);
+       crWaitUntilV(pktin);
+       if (pktin->type != SSH2_MSG_CHANNEL_OPEN_CONFIRMATION) {
+           bombout(("Server refused to open a session"));
+           crStopV;
+           /* FIXME: error data comes back in FAILURE packet */
+       }
+       if (ssh_pkt_getuint32(pktin) != ssh->mainchan->localid) {
+           bombout(("Server's channel confirmation cited wrong channel"));
+           crStopV;
+       }
+       ssh->mainchan->remoteid = ssh_pkt_getuint32(pktin);
+       ssh->mainchan->type = CHAN_MAINSESSION;
+       ssh->mainchan->closes = 0;
+       ssh->mainchan->v.v2.remwindow = ssh_pkt_getuint32(pktin);
+       ssh->mainchan->v.v2.remmaxpkt = ssh_pkt_getuint32(pktin);
+       bufchain_init(&ssh->mainchan->v.v2.outbuffer);
+       add234(ssh->channels, ssh->mainchan);
+       update_specials_menu(ssh->frontend);
+       logevent("Opened channel for session");
+    } else
+       ssh->mainchan = NULL;
+
+    /*
+     * Now we have a channel, make dispatch table entries for
+     * general channel-based messages.
+     */
+    ssh->packet_dispatch[SSH2_MSG_CHANNEL_DATA] =
+    ssh->packet_dispatch[SSH2_MSG_CHANNEL_EXTENDED_DATA] =
+       ssh2_msg_channel_data;
+    ssh->packet_dispatch[SSH2_MSG_CHANNEL_EOF] = ssh2_msg_channel_eof;
+    ssh->packet_dispatch[SSH2_MSG_CHANNEL_CLOSE] = ssh2_msg_channel_close;
+    ssh->packet_dispatch[SSH2_MSG_CHANNEL_OPEN_CONFIRMATION] =
+       ssh2_msg_channel_open_confirmation;
+    ssh->packet_dispatch[SSH2_MSG_CHANNEL_OPEN_FAILURE] =
+       ssh2_msg_channel_open_failure;
+    ssh->packet_dispatch[SSH2_MSG_CHANNEL_REQUEST] =
+       ssh2_msg_channel_request;
+    ssh->packet_dispatch[SSH2_MSG_CHANNEL_OPEN] =
+       ssh2_msg_channel_open;
 
     /*
      * Potentially enable X11 forwarding.
      */
-    if (cfg.x11_forward) {
+    if (ssh->mainchan && ssh->cfg.x11_forward) {
        char proto[20], data[64];
        logevent("Requesting X11 forwarding");
-       x11_invent_auth(proto, sizeof(proto), data, sizeof(data));
-       ssh2_pkt_init(SSH2_MSG_CHANNEL_REQUEST);
-       ssh2_pkt_adduint32(mainchan->remoteid);
-       ssh2_pkt_addstring("x11-req");
-       ssh2_pkt_addbool(1);           /* want reply */
-       ssh2_pkt_addbool(0);           /* many connections */
-       ssh2_pkt_addstring(proto);
-       ssh2_pkt_addstring(data);
-       ssh2_pkt_adduint32(0);         /* screen number */
-       ssh2_pkt_send();
-
-       do {
-           crWaitUntilV(ispkt);
-           if (pktin.type == SSH2_MSG_CHANNEL_WINDOW_ADJUST) {
-               unsigned i = ssh2_pkt_getuint32();
-               struct ssh_channel *c;
-               c = find234(ssh_channels, &i, ssh_channelfind);
-               if (!c)
-                   continue;          /* nonexistent channel */
-               c->v.v2.remwindow += ssh2_pkt_getuint32();
-           }
-       } while (pktin.type == SSH2_MSG_CHANNEL_WINDOW_ADJUST);
-
-       if (pktin.type != SSH2_MSG_CHANNEL_SUCCESS) {
-           if (pktin.type != SSH2_MSG_CHANNEL_FAILURE) {
+       ssh->x11auth = x11_invent_auth(proto, sizeof(proto),
+                                      data, sizeof(data), ssh->cfg.x11_auth);
+        x11_get_real_auth(ssh->x11auth, ssh->cfg.x11_display);
+       s->pktout = ssh2_pkt_init(SSH2_MSG_CHANNEL_REQUEST);
+       ssh2_pkt_adduint32(s->pktout, ssh->mainchan->remoteid);
+       ssh2_pkt_addstring(s->pktout, "x11-req");
+       ssh2_pkt_addbool(s->pktout, 1);        /* want reply */
+       ssh2_pkt_addbool(s->pktout, 0);        /* many connections */
+       ssh2_pkt_addstring(s->pktout, proto);
+       ssh2_pkt_addstring(s->pktout, data);
+       ssh2_pkt_adduint32(s->pktout, x11_get_screen_number(ssh->cfg.x11_display));
+       ssh2_pkt_send(ssh, s->pktout);
+
+       crWaitUntilV(pktin);
+
+       if (pktin->type != SSH2_MSG_CHANNEL_SUCCESS) {
+           if (pktin->type != SSH2_MSG_CHANNEL_FAILURE) {
                bombout(("Unexpected response to X11 forwarding request:"
-                        " packet type %d", pktin.type));
-               crReturnV;
+                        " packet type %d", pktin->type));
+               crStopV;
            }
            logevent("X11 forwarding refused");
        } else {
            logevent("X11 forwarding enabled");
-           ssh_X11_fwd_enabled = TRUE;
-       }
-    }
-
-    /*
-     * Enable port forwardings.
-     */
-    {
-       static char *e;                /* preserve across crReturn */
-       char type;
-       int n;
-       int sport,dport,sserv,dserv;
-       char sports[256], dports[256], host[256];
-       char buf[1024];
-       struct servent *se;
-
-       ssh_rportfwds = newtree234(ssh_rportcmp_ssh2);
-        /* Add port forwardings. */
-       e = cfg.portfwd;
-       while (*e) {
-           type = *e++;
-           n = 0;
-           while (*e && *e != '\t')
-               sports[n++] = *e++;
-           sports[n] = 0;
-           if (*e == '\t')
-               e++;
-           n = 0;
-           while (*e && *e != ':')
-               host[n++] = *e++;
-           host[n] = 0;
-           if (*e == ':')
-               e++;
-           n = 0;
-           while (*e)
-               dports[n++] = *e++;
-           dports[n] = 0;
-           e++;
-           dport = atoi(dports);
-           dserv = 0;
-           if (dport == 0) {
-               dserv = 1;
-               se = getservbyname(dports, NULL);
-               if (se != NULL) {
-                   dport = ntohs(se->s_port);
-               } else {
-                   sprintf(buf,
-                           "Service lookup failed for destination port \"%s\"",
-                           dports);
-                   logevent(buf);
-               }
-           }
-           sport = atoi(sports);
-           sserv = 0;
-           if (sport == 0) {
-               sserv = 1;
-               se = getservbyname(sports, NULL);
-               if (se != NULL) {
-                   sport = ntohs(se->s_port);
-               } else {
-                   sprintf(buf,
-                           "Service lookup failed for source port \"%s\"",
-                           sports);
-                   logevent(buf);
-               }
-           }
-           if (sport && dport) {
-               if (type == 'L') {
-                   pfd_addforward(host, dport, sport);
-                   sprintf(buf, "Local port %.*s%.*s%d%.*s forwarding to"
-                           " %s:%.*s%.*s%d%.*s",
-                           sserv ? strlen(sports) : 0, sports,
-                           sserv, "(", sport, sserv, ")",
-                           host,
-                           dserv ? strlen(dports) : 0, dports,
-                           dserv, "(", dport, dserv, ")");
-                   logevent(buf);
-               } else {
-                   struct ssh_rportfwd *pf;
-                   pf = smalloc(sizeof(*pf));
-                   strcpy(pf->dhost, host);
-                   pf->dport = dport;
-                   pf->sport = sport;
-                   if (add234(ssh_rportfwds, pf) != pf) {
-                       sprintf(buf, 
-                               "Duplicate remote port forwarding to %s:%d",
-                               host, dport);
-                       logevent(buf);
-                       sfree(pf);
-                   } else {
-                       sprintf(buf, "Requesting remote port %.*s%.*s%d%.*s"
-                               " forward to %s:%.*s%.*s%d%.*s",
-                           sserv ? strlen(sports) : 0, sports,
-                           sserv, "(", sport, sserv, ")",
-                           host,
-                           dserv ? strlen(dports) : 0, dports,
-                           dserv, "(", dport, dserv, ")");
-                       logevent(buf);
-                       ssh2_pkt_init(SSH2_MSG_GLOBAL_REQUEST);
-                       ssh2_pkt_addstring("tcpip-forward");
-                       ssh2_pkt_addbool(1);/* want reply */
-                       if (cfg.rport_acceptall)
-                           ssh2_pkt_addstring("0.0.0.0");
-                       else
-                           ssh2_pkt_addstring("127.0.0.1");
-                       ssh2_pkt_adduint32(sport);
-                       ssh2_pkt_send();
-
-                       do {
-                           crWaitUntilV(ispkt);
-                           if (pktin.type == SSH2_MSG_CHANNEL_WINDOW_ADJUST) {
-                               unsigned i = ssh2_pkt_getuint32();
-                               struct ssh_channel *c;
-                               c = find234(ssh_channels, &i, ssh_channelfind);
-                               if (!c)
-                                   continue;/* nonexistent channel */
-                               c->v.v2.remwindow += ssh2_pkt_getuint32();
-                           }
-                       } while (pktin.type == SSH2_MSG_CHANNEL_WINDOW_ADJUST);
-
-                       if (pktin.type != SSH2_MSG_REQUEST_SUCCESS) {
-                           if (pktin.type != SSH2_MSG_REQUEST_FAILURE) {
-                               bombout(("Unexpected response to port "
-                                        "forwarding request: packet type %d",
-                                        pktin.type));
-                               crReturnV;
-                           }
-                           logevent("Server refused this port forwarding");
-                       } else {
-                           logevent("Remote port forwarding enabled");
-                       }
-                   }
-               }
-           }
+           ssh->X11_fwd_enabled = TRUE;
        }
     }
 
     /*
+     * Enable port forwardings.
+     */
+    ssh_setup_portfwd(ssh, &ssh->cfg);
+
+    /*
      * Potentially enable agent forwarding.
      */
-    if (cfg.agentfwd && agent_exists()) {
+    if (ssh->mainchan && ssh->cfg.agentfwd && agent_exists()) {
        logevent("Requesting OpenSSH-style agent forwarding");
-       ssh2_pkt_init(SSH2_MSG_CHANNEL_REQUEST);
-       ssh2_pkt_adduint32(mainchan->remoteid);
-       ssh2_pkt_addstring("auth-agent-req@openssh.com");
-       ssh2_pkt_addbool(1);           /* want reply */
-       ssh2_pkt_send();
+       s->pktout = ssh2_pkt_init(SSH2_MSG_CHANNEL_REQUEST);
+       ssh2_pkt_adduint32(s->pktout, ssh->mainchan->remoteid);
+       ssh2_pkt_addstring(s->pktout, "auth-agent-req@openssh.com");
+       ssh2_pkt_addbool(s->pktout, 1);        /* want reply */
+       ssh2_pkt_send(ssh, s->pktout);
 
-       do {
-           crWaitUntilV(ispkt);
-           if (pktin.type == SSH2_MSG_CHANNEL_WINDOW_ADJUST) {
-               unsigned i = ssh2_pkt_getuint32();
-               struct ssh_channel *c;
-               c = find234(ssh_channels, &i, ssh_channelfind);
-               if (!c)
-                   continue;          /* nonexistent channel */
-               c->v.v2.remwindow += ssh2_pkt_getuint32();
-           }
-       } while (pktin.type == SSH2_MSG_CHANNEL_WINDOW_ADJUST);
+       crWaitUntilV(pktin);
 
-       if (pktin.type != SSH2_MSG_CHANNEL_SUCCESS) {
-           if (pktin.type != SSH2_MSG_CHANNEL_FAILURE) {
+       if (pktin->type != SSH2_MSG_CHANNEL_SUCCESS) {
+           if (pktin->type != SSH2_MSG_CHANNEL_FAILURE) {
                bombout(("Unexpected response to agent forwarding request:"
-                        " packet type %d", pktin.type));
-               crReturnV;
+                        " packet type %d", pktin->type));
+               crStopV;
            }
            logevent("Agent forwarding refused");
        } else {
            logevent("Agent forwarding enabled");
-           ssh_agentfwd_enabled = TRUE;
+           ssh->agentfwd_enabled = TRUE;
        }
     }
 
     /*
      * Now allocate a pty for the session.
      */
-    if (!cfg.nopty) {
-       ssh2_pkt_init(SSH2_MSG_CHANNEL_REQUEST);
-       ssh2_pkt_adduint32(mainchan->remoteid); /* recipient channel */
-       ssh2_pkt_addstring("pty-req");
-       ssh2_pkt_addbool(1);           /* want reply */
-       ssh2_pkt_addstring(cfg.termtype);
-       ssh2_pkt_adduint32(cols);
-       ssh2_pkt_adduint32(rows);
-       ssh2_pkt_adduint32(0);         /* pixel width */
-       ssh2_pkt_adduint32(0);         /* pixel height */
-       ssh2_pkt_addstring_start();
-       ssh2_pkt_addstring_data("\0", 1);       /* TTY_OP_END, no special options */
-       ssh2_pkt_send();
-       ssh_state = SSH_STATE_INTERMED;
-
-       do {
-           crWaitUntilV(ispkt);
-           if (pktin.type == SSH2_MSG_CHANNEL_WINDOW_ADJUST) {
-               unsigned i = ssh2_pkt_getuint32();
-               struct ssh_channel *c;
-               c = find234(ssh_channels, &i, ssh_channelfind);
-               if (!c)
-                   continue;          /* nonexistent channel */
-               c->v.v2.remwindow += ssh2_pkt_getuint32();
-           }
-       } while (pktin.type == SSH2_MSG_CHANNEL_WINDOW_ADJUST);
-
-       if (pktin.type != SSH2_MSG_CHANNEL_SUCCESS) {
-           if (pktin.type != SSH2_MSG_CHANNEL_FAILURE) {
+    if (ssh->mainchan && !ssh->cfg.nopty) {
+       /* Unpick the terminal-speed string. */
+       /* XXX perhaps we should allow no speeds to be sent. */
+        ssh->ospeed = 38400; ssh->ispeed = 38400; /* last-resort defaults */
+       sscanf(ssh->cfg.termspeed, "%d,%d", &ssh->ospeed, &ssh->ispeed);
+       /* Build the pty request. */
+       s->pktout = ssh2_pkt_init(SSH2_MSG_CHANNEL_REQUEST);
+       ssh2_pkt_adduint32(s->pktout, ssh->mainchan->remoteid); /* recipient channel */
+       ssh2_pkt_addstring(s->pktout, "pty-req");
+       ssh2_pkt_addbool(s->pktout, 1);        /* want reply */
+       ssh2_pkt_addstring(s->pktout, ssh->cfg.termtype);
+       ssh2_pkt_adduint32(s->pktout, ssh->term_width);
+       ssh2_pkt_adduint32(s->pktout, ssh->term_height);
+       ssh2_pkt_adduint32(s->pktout, 0);              /* pixel width */
+       ssh2_pkt_adduint32(s->pktout, 0);              /* pixel height */
+       ssh2_pkt_addstring_start(s->pktout);
+       ssh2_pkt_addbyte(s->pktout, 128);              /* TTY_OP_ISPEED */
+       ssh2_pkt_adduint32(s->pktout, ssh->ispeed);
+       ssh2_pkt_addbyte(s->pktout, 129);              /* TTY_OP_OSPEED */
+       ssh2_pkt_adduint32(s->pktout, ssh->ospeed);
+       ssh2_pkt_addstring_data(s->pktout, "\0", 1); /* TTY_OP_END */
+       ssh2_pkt_send(ssh, s->pktout);
+       ssh->state = SSH_STATE_INTERMED;
+
+       crWaitUntilV(pktin);
+
+       if (pktin->type != SSH2_MSG_CHANNEL_SUCCESS) {
+           if (pktin->type != SSH2_MSG_CHANNEL_FAILURE) {
                bombout(("Unexpected response to pty request:"
-                        " packet type %d", pktin.type));
-               crReturnV;
+                        " packet type %d", pktin->type));
+               crStopV;
            }
-           c_write_str("Server refused to allocate pty\r\n");
-           ssh_editing = ssh_echoing = 1;
+           c_write_str(ssh, "Server refused to allocate pty\r\n");
+           ssh->editing = ssh->echoing = 1;
        } else {
-           logevent("Allocated pty");
+           logeventf(ssh, "Allocated pty (ospeed %dbps, ispeed %dbps)",
+                     ssh->ospeed, ssh->ispeed);
        }
     } else {
-       ssh_editing = ssh_echoing = 1;
+       ssh->editing = ssh->echoing = 1;
+    }
+
+    /*
+     * Send environment variables.
+     * 
+     * Simplest thing here is to send all the requests at once, and
+     * then wait for a whole bunch of successes or failures.
+     */
+    if (ssh->mainchan && *ssh->cfg.environmt) {
+       char *e = ssh->cfg.environmt;
+       char *var, *varend, *val;
+
+       s->num_env = 0;
+
+       while (*e) {
+           var = e;
+           while (*e && *e != '\t') e++;
+           varend = e;
+           if (*e == '\t') e++;
+           val = e;
+           while (*e) e++;
+           e++;
+
+           s->pktout = ssh2_pkt_init(SSH2_MSG_CHANNEL_REQUEST);
+           ssh2_pkt_adduint32(s->pktout, ssh->mainchan->remoteid);
+           ssh2_pkt_addstring(s->pktout, "env");
+           ssh2_pkt_addbool(s->pktout, 1);            /* want reply */
+           ssh2_pkt_addstring_start(s->pktout);
+           ssh2_pkt_addstring_data(s->pktout, var, varend-var);
+           ssh2_pkt_addstring(s->pktout, val);
+           ssh2_pkt_send(ssh, s->pktout);
+
+           s->num_env++;
+       }
+
+       logeventf(ssh, "Sent %d environment variables", s->num_env);
+
+       s->env_ok = 0;
+       s->env_left = s->num_env;
+
+       while (s->env_left > 0) {
+           crWaitUntilV(pktin);
+
+           if (pktin->type != SSH2_MSG_CHANNEL_SUCCESS) {
+               if (pktin->type != SSH2_MSG_CHANNEL_FAILURE) {
+                   bombout(("Unexpected response to environment request:"
+                            " packet type %d", pktin->type));
+                   crStopV;
+               }
+           } else {
+               s->env_ok++;
+           }
+
+           s->env_left--;
+       }
+
+       if (s->env_ok == s->num_env) {
+           logevent("All environment variables successfully set");
+       } else if (s->env_ok == 0) {
+           logevent("All environment variables refused");
+           c_write_str(ssh, "Server refused to set environment variables\r\n");
+       } else {
+           logeventf(ssh, "%d environment variables refused",
+                     s->num_env - s->env_ok);
+           c_write_str(ssh, "Server refused to set all environment variables\r\n");
+       }
     }
 
     /*
@@ -5114,49 +7104,41 @@ static void do_ssh2_authconn(unsigned char *in, int inlen, int ispkt)
      * this twice if the config data has provided a second choice
      * of command.
      */
-    while (1) {
+    if (ssh->mainchan) while (1) {
        int subsys;
        char *cmd;
 
-       if (ssh_fallback_cmd) {
-           subsys = cfg.ssh_subsys2;
-           cmd = cfg.remote_cmd_ptr2;
+       if (ssh->fallback_cmd) {
+           subsys = ssh->cfg.ssh_subsys2;
+           cmd = ssh->cfg.remote_cmd_ptr2;
        } else {
-           subsys = cfg.ssh_subsys;
-           cmd = cfg.remote_cmd_ptr;
+           subsys = ssh->cfg.ssh_subsys;
+           cmd = ssh->cfg.remote_cmd_ptr;
        }
 
-       ssh2_pkt_init(SSH2_MSG_CHANNEL_REQUEST);
-       ssh2_pkt_adduint32(mainchan->remoteid); /* recipient channel */
+       s->pktout = ssh2_pkt_init(SSH2_MSG_CHANNEL_REQUEST);
+       ssh2_pkt_adduint32(s->pktout, ssh->mainchan->remoteid); /* recipient channel */
        if (subsys) {
-           ssh2_pkt_addstring("subsystem");
-           ssh2_pkt_addbool(1);               /* want reply */
-           ssh2_pkt_addstring(cmd);
+           ssh2_pkt_addstring(s->pktout, "subsystem");
+           ssh2_pkt_addbool(s->pktout, 1);            /* want reply */
+           ssh2_pkt_addstring(s->pktout, cmd);
        } else if (*cmd) {
-           ssh2_pkt_addstring("exec");
-           ssh2_pkt_addbool(1);               /* want reply */
-           ssh2_pkt_addstring(cmd);
+           ssh2_pkt_addstring(s->pktout, "exec");
+           ssh2_pkt_addbool(s->pktout, 1);            /* want reply */
+           ssh2_pkt_addstring(s->pktout, cmd);
        } else {
-           ssh2_pkt_addstring("shell");
-           ssh2_pkt_addbool(1);               /* want reply */
+           ssh2_pkt_addstring(s->pktout, "shell");
+           ssh2_pkt_addbool(s->pktout, 1);            /* want reply */
        }
-       ssh2_pkt_send();
-       do {
-           crWaitUntilV(ispkt);
-           if (pktin.type == SSH2_MSG_CHANNEL_WINDOW_ADJUST) {
-               unsigned i = ssh2_pkt_getuint32();
-               struct ssh_channel *c;
-               c = find234(ssh_channels, &i, ssh_channelfind);
-               if (!c)
-                   continue;          /* nonexistent channel */
-               c->v.v2.remwindow += ssh2_pkt_getuint32();
-           }
-       } while (pktin.type == SSH2_MSG_CHANNEL_WINDOW_ADJUST);
-       if (pktin.type != SSH2_MSG_CHANNEL_SUCCESS) {
-           if (pktin.type != SSH2_MSG_CHANNEL_FAILURE) {
+       ssh2_pkt_send(ssh, s->pktout);
+
+       crWaitUntilV(pktin);
+
+       if (pktin->type != SSH2_MSG_CHANNEL_SUCCESS) {
+           if (pktin->type != SSH2_MSG_CHANNEL_FAILURE) {
                bombout(("Unexpected response to shell/command request:"
-                        " packet type %d", pktin.type));
-               crReturnV;
+                        " packet type %d", pktin->type));
+               crStopV;
            }
            /*
             * We failed to start the command. If this is the
@@ -5164,437 +7146,63 @@ static void do_ssh2_authconn(unsigned char *in, int inlen, int ispkt)
             * not, and if the fallback command exists, try falling
             * back to it before complaining.
             */
-           if (!ssh_fallback_cmd && cfg.remote_cmd_ptr2 != NULL) {
+           if (!ssh->fallback_cmd && ssh->cfg.remote_cmd_ptr2 != NULL) {
                logevent("Primary command failed; attempting fallback");
-               ssh_fallback_cmd = TRUE;
+               ssh->fallback_cmd = TRUE;
                continue;
            }
            bombout(("Server refused to start a shell/command"));
-           crReturnV;
+           crStopV;
        } else {
            logevent("Started a shell/command");
        }
        break;
     }
 
-    ssh_state = SSH_STATE_SESSION;
-    if (size_needed)
-       ssh_size();
-    if (eof_needed)
-       ssh_special(TS_EOF);
+    ssh->state = SSH_STATE_SESSION;
+    if (ssh->size_needed)
+       ssh_size(ssh, ssh->term_width, ssh->term_height);
+    if (ssh->eof_needed)
+       ssh_special(ssh, TS_EOF);
 
     /*
      * Transfer data!
      */
-    ldisc_send(NULL, 0, 0);           /* cause ldisc to notice changes */
-    ssh_send_ok = 1;
+    if (ssh->ldisc)
+       ldisc_send(ssh->ldisc, NULL, 0, 0);/* cause ldisc to notice changes */
+    if (ssh->mainchan)
+       ssh->send_ok = 1;
     while (1) {
-       static int try_send;
        crReturnV;
-       try_send = FALSE;
-       if (ispkt) {
-           if (pktin.type == SSH2_MSG_CHANNEL_DATA ||
-               pktin.type == SSH2_MSG_CHANNEL_EXTENDED_DATA) {
-               char *data;
-               int length;
-               unsigned i = ssh2_pkt_getuint32();
-               struct ssh_channel *c;
-               c = find234(ssh_channels, &i, ssh_channelfind);
-               if (!c)
-                   continue;          /* nonexistent channel */
-               if (pktin.type == SSH2_MSG_CHANNEL_EXTENDED_DATA &&
-                   ssh2_pkt_getuint32() != SSH2_EXTENDED_DATA_STDERR)
-                   continue;          /* extended but not stderr */
-               ssh2_pkt_getstring(&data, &length);
-               if (data) {
-                   int bufsize;
-                   c->v.v2.locwindow -= length;
-                   switch (c->type) {
-                     case CHAN_MAINSESSION:
-                       bufsize =
-                           from_backend(pktin.type ==
-                                        SSH2_MSG_CHANNEL_EXTENDED_DATA,
-                                        data, length);
-                       break;
-                     case CHAN_X11:
-                       bufsize = x11_send(c->u.x11.s, data, length);
-                       break;
-                     case CHAN_SOCKDATA:
-                       bufsize = pfd_send(c->u.pfd.s, data, length);
-                       break;
-                     case CHAN_AGENT:
-                       while (length > 0) {
-                           if (c->u.a.lensofar < 4) {
-                               int l = min(4 - c->u.a.lensofar, length);
-                               memcpy(c->u.a.msglen + c->u.a.lensofar,
-                                      data, l);
-                               data += l;
-                               length -= l;
-                               c->u.a.lensofar += l;
-                           }
-                           if (c->u.a.lensofar == 4) {
-                               c->u.a.totallen =
-                                   4 + GET_32BIT(c->u.a.msglen);
-                               c->u.a.message = smalloc(c->u.a.totallen);
-                               memcpy(c->u.a.message, c->u.a.msglen, 4);
-                           }
-                           if (c->u.a.lensofar >= 4 && length > 0) {
-                               int l =
-                                   min(c->u.a.totallen - c->u.a.lensofar,
-                                       length);
-                               memcpy(c->u.a.message + c->u.a.lensofar,
-                                      data, l);
-                               data += l;
-                               length -= l;
-                               c->u.a.lensofar += l;
-                           }
-                           if (c->u.a.lensofar == c->u.a.totallen) {
-                               void *reply, *sentreply;
-                               int replylen;
-                               agent_query(c->u.a.message,
-                                           c->u.a.totallen, &reply,
-                                           &replylen);
-                               if (reply)
-                                   sentreply = reply;
-                               else {
-                                   /* Fake SSH_AGENT_FAILURE. */
-                                   sentreply = "\0\0\0\1\5";
-                                   replylen = 5;
-                               }
-                               ssh2_add_channel_data(c, sentreply,
-                                                     replylen);
-                               try_send = TRUE;
-                               if (reply)
-                                   sfree(reply);
-                               sfree(c->u.a.message);
-                               c->u.a.lensofar = 0;
-                           }
-                       }
-                       bufsize = 0;
-                       break;
-                   }
-                   /*
-                    * If we are not buffering too much data,
-                    * enlarge the window again at the remote side.
-                    */
-                   if (bufsize < OUR_V2_WINSIZE)
-                       ssh2_set_window(c, OUR_V2_WINSIZE - bufsize);
-               }
-           } else if (pktin.type == SSH2_MSG_DISCONNECT) {
-               ssh_state = SSH_STATE_CLOSED;
-               logevent("Received disconnect message");
-               crReturnV;
-           } else if (pktin.type == SSH2_MSG_CHANNEL_EOF) {
-               unsigned i = ssh2_pkt_getuint32();
-               struct ssh_channel *c;
-
-               c = find234(ssh_channels, &i, ssh_channelfind);
-               if (!c)
-                   continue;          /* nonexistent channel */
-
-               if (c->type == CHAN_X11) {
-                   /*
-                    * Remote EOF on an X11 channel means we should
-                    * wrap up and close the channel ourselves.
-                    */
-                   x11_close(c->u.x11.s);
-                   sshfwd_close(c);
-               } else if (c->type == CHAN_AGENT) {
-                   sshfwd_close(c);
-               } else if (c->type == CHAN_SOCKDATA) {
-                   pfd_close(c->u.pfd.s);
-                   sshfwd_close(c);
-               }
-           } else if (pktin.type == SSH2_MSG_CHANNEL_CLOSE) {
-               unsigned i = ssh2_pkt_getuint32();
-               struct ssh_channel *c;
-
-               c = find234(ssh_channels, &i, ssh_channelfind);
-               if (!c)
-                   continue;          /* nonexistent channel */
-               /* Do pre-close processing on the channel. */
-               switch (c->type) {
-                 case CHAN_MAINSESSION:
-                   break;             /* nothing to see here, move along */
-                 case CHAN_X11:
-                   if (c->u.x11.s != NULL)
-                       x11_close(c->u.x11.s);
-                   sshfwd_close(c);
-                   break;
-                 case CHAN_AGENT:
-                   sshfwd_close(c);
-                   break;
-                 case CHAN_SOCKDATA:
-                   if (c->u.pfd.s != NULL)
-                       pfd_close(c->u.pfd.s);
-                   sshfwd_close(c);
-                   break;
-               }
-               if (c->closes == 0) {
-                   ssh2_pkt_init(SSH2_MSG_CHANNEL_CLOSE);
-                   ssh2_pkt_adduint32(c->remoteid);
-                   ssh2_pkt_send();
-               }
-               del234(ssh_channels, c);
-               bufchain_clear(&c->v.v2.outbuffer);
-               sfree(c);
-
-               /*
-                * See if that was the last channel left open.
-                */
-               if (count234(ssh_channels) == 0) {
-#if 0
-                    /*
-                     * We used to send SSH_MSG_DISCONNECT here,
-                     * because I'd believed that _every_ conforming
-                     * SSH2 connection had to end with a disconnect
-                     * being sent by at least one side; apparently
-                     * I was wrong and it's perfectly OK to
-                     * unceremoniously slam the connection shut
-                     * when you're done, and indeed OpenSSH feels
-                     * this is more polite than sending a
-                     * DISCONNECT. So now we don't.
-                     */
-                   logevent("All channels closed. Disconnecting");
-                   ssh2_pkt_init(SSH2_MSG_DISCONNECT);
-                   ssh2_pkt_adduint32(SSH2_DISCONNECT_BY_APPLICATION);
-                   ssh2_pkt_addstring("All open channels closed");
-                   ssh2_pkt_addstring("en");   /* language tag */
-                   ssh2_pkt_send();
-#endif
-                   ssh_state = SSH_STATE_CLOSED;
-                   crReturnV;
-               }
-               continue;              /* remote sends close; ignore (FIXME) */
-           } else if (pktin.type == SSH2_MSG_CHANNEL_WINDOW_ADJUST) {
-               unsigned i = ssh2_pkt_getuint32();
-               struct ssh_channel *c;
-               c = find234(ssh_channels, &i, ssh_channelfind);
-               if (!c)
-                   continue;          /* nonexistent channel */
-               c->v.v2.remwindow += ssh2_pkt_getuint32();
-               try_send = TRUE;
-           } else if (pktin.type == SSH2_MSG_CHANNEL_OPEN_CONFIRMATION) {
-               unsigned i = ssh2_pkt_getuint32();
-               struct ssh_channel *c;
-               c = find234(ssh_channels, &i, ssh_channelfind);
-               if (!c)
-                   continue;          /* nonexistent channel */
-               if (c->type != CHAN_SOCKDATA_DORMANT)
-                   continue;          /* dunno why they're confirming this */
-               c->remoteid = ssh2_pkt_getuint32();
-               c->type = CHAN_SOCKDATA;
-               c->v.v2.remwindow = ssh2_pkt_getuint32();
-               c->v.v2.remmaxpkt = ssh2_pkt_getuint32();
-               if (c->u.pfd.s)
-                   pfd_confirm(c->u.pfd.s);
-               if (c->closes) {
-                   /*
-                    * We have a pending close on this channel,
-                    * which we decided on before the server acked
-                    * the channel open. So now we know the
-                    * remoteid, we can close it again.
-                    */
-                   ssh2_pkt_init(SSH2_MSG_CHANNEL_CLOSE);
-                   ssh2_pkt_adduint32(c->remoteid);
-                   ssh2_pkt_send();
-               }
-           } else if (pktin.type == SSH2_MSG_CHANNEL_OPEN_FAILURE) {
-               unsigned i = ssh2_pkt_getuint32();
-               struct ssh_channel *c;
-               c = find234(ssh_channels, &i, ssh_channelfind);
-               if (!c)
-                   continue;          /* nonexistent channel */
-               if (c->type != CHAN_SOCKDATA_DORMANT)
-                   continue;          /* dunno why they're failing this */
-
-               logevent("Forwarded connection refused by server");
-
-               pfd_close(c->u.pfd.s);
+       s->try_send = FALSE;
+       if (pktin) {
 
-               del234(ssh_channels, c);
-               sfree(c);
-           } else if (pktin.type == SSH2_MSG_CHANNEL_REQUEST) {
-               unsigned localid;
-               char *type;
-               int typelen, want_reply;
-               struct ssh_channel *c;
-
-               localid = ssh2_pkt_getuint32();
-               ssh2_pkt_getstring(&type, &typelen);
-               want_reply = ssh2_pkt_getbool();
-
-               /*
-                * First, check that the channel exists. Otherwise,
-                * we can instantly disconnect with a rude message.
-                */
-               c = find234(ssh_channels, &localid, ssh_channelfind);
-               if (!c) {
-                   char buf[80];
-                   sprintf(buf, "Received channel request for nonexistent"
-                           " channel %d", localid);
-                   logevent(buf);
-                   ssh2_pkt_init(SSH2_MSG_DISCONNECT);
-                   ssh2_pkt_adduint32(SSH2_DISCONNECT_BY_APPLICATION);
-                   ssh2_pkt_addstring(buf);
-                   ssh2_pkt_addstring("en");   /* language tag */
-                   ssh2_pkt_send();
-                   connection_fatal("%s", buf);
-                   ssh_state = SSH_STATE_CLOSED;
-                   crReturnV;
-               }
-
-               /*
-                * Having got the channel number, we now look at
-                * the request type string to see if it's something
-                * we recognise.
-                */
-               if (typelen == 11 && !memcmp(type, "exit-status", 11) &&
-                   c == mainchan) {
-                   /* We recognise "exit-status" on the primary channel. */
-                   char buf[100];
-                   ssh_exitcode = ssh2_pkt_getuint32();
-                   sprintf(buf, "Server sent command exit status %d",
-                           ssh_exitcode);
-                   logevent(buf);
-                   if (want_reply) {
-                       ssh2_pkt_init(SSH2_MSG_CHANNEL_SUCCESS);
-                       ssh2_pkt_adduint32(c->remoteid);
-                       ssh2_pkt_send();
-                   }
-               } else {
-                   /*
-                    * This is a channel request we don't know
-                    * about, so we now either ignore the request
-                    * or respond with CHANNEL_FAILURE, depending
-                    * on want_reply.
-                    */
-                   if (want_reply) {
-                       ssh2_pkt_init(SSH2_MSG_CHANNEL_FAILURE);
-                       ssh2_pkt_adduint32(c->remoteid);
-                       ssh2_pkt_send();
-                   }
-               }
-           } else if (pktin.type == SSH2_MSG_GLOBAL_REQUEST) {
-               char *type;
-               int typelen, want_reply;
-
-               ssh2_pkt_getstring(&type, &typelen);
-               want_reply = ssh2_pkt_getbool();
-
-                /*
-                 * We currently don't support any global requests
-                 * at all, so we either ignore the request or
-                 * respond with REQUEST_FAILURE, depending on
-                 * want_reply.
-                 */
-                if (want_reply) {
-                    ssh2_pkt_init(SSH2_MSG_REQUEST_FAILURE);
-                    ssh2_pkt_send();
-               }
-           } else if (pktin.type == SSH2_MSG_CHANNEL_OPEN) {
-               char *type;
-               int typelen;
-               char *error = NULL;
-               struct ssh_channel *c;
-               unsigned remid, winsize, pktsize;
-               ssh2_pkt_getstring(&type, &typelen);
-               c = smalloc(sizeof(struct ssh_channel));
-
-               remid = ssh2_pkt_getuint32();
-               winsize = ssh2_pkt_getuint32();
-               pktsize = ssh2_pkt_getuint32();
-
-               if (typelen == 3 && !memcmp(type, "x11", 3)) {
-                   if (!ssh_X11_fwd_enabled)
-                       error = "X11 forwarding is not enabled";
-                   else if (x11_init(&c->u.x11.s, cfg.x11_display, c) !=
-                            NULL) {
-                       error = "Unable to open an X11 connection";
-                   } else {
-                       c->type = CHAN_X11;
-                   }
-               } else if (typelen == 15 &&
-                          !memcmp(type, "forwarded-tcpip", 15)) {
-                   struct ssh_rportfwd pf, *realpf;
-                   char *dummy;
-                   int dummylen;
-                   ssh2_pkt_getstring(&dummy, &dummylen);/* skip address */
-                   pf.sport = ssh2_pkt_getuint32();
-                   realpf = find234(ssh_rportfwds, &pf, NULL);
-                   if (realpf == NULL) {
-                       error = "Remote port is not recognised";
-                   } else {
-                       char *e = pfd_newconnect(&c->u.pfd.s, realpf->dhost,
-                                                realpf->dport, c);
-                       char buf[1024];
-                       sprintf(buf, "Received remote port open request for %s:%d",
-                               realpf->dhost, realpf->dport);
-                       logevent(buf);
-                       if (e != NULL) {
-                           sprintf(buf, "Port open failed: %s", e);
-                           logevent(buf);
-                           error = "Port open failed";
-                       } else {
-                           logevent("Forwarded port opened successfully");
-                           c->type = CHAN_SOCKDATA;
-                       }
-                   }
-               } else if (typelen == 22 &&
-                          !memcmp(type, "auth-agent@openssh.com", 3)) {
-                   if (!ssh_agentfwd_enabled)
-                       error = "Agent forwarding is not enabled";
-                   else {
-                       c->type = CHAN_AGENT;   /* identify channel type */
-                       c->u.a.lensofar = 0;
-                   }
-               } else {
-                   error = "Unsupported channel type requested";
-               }
+           /*
+            * _All_ the connection-layer packets we expect to
+            * receive are now handled by the dispatch table.
+            * Anything that reaches here must be bogus.
+            */
 
-               c->remoteid = remid;
-               if (error) {
-                   ssh2_pkt_init(SSH2_MSG_CHANNEL_OPEN_FAILURE);
-                   ssh2_pkt_adduint32(c->remoteid);
-                   ssh2_pkt_adduint32(SSH2_OPEN_CONNECT_FAILED);
-                   ssh2_pkt_addstring(error);
-                   ssh2_pkt_addstring("en");   /* language tag */
-                   ssh2_pkt_send();
-                   sfree(c);
-               } else {
-                   c->localid = alloc_channel_id();
-                   c->closes = 0;
-                   c->v.v2.locwindow = OUR_V2_WINSIZE;
-                   c->v.v2.remwindow = winsize;
-                   c->v.v2.remmaxpkt = pktsize;
-                   bufchain_init(&c->v.v2.outbuffer);
-                   add234(ssh_channels, c);
-                   ssh2_pkt_init(SSH2_MSG_CHANNEL_OPEN_CONFIRMATION);
-                   ssh2_pkt_adduint32(c->remoteid);
-                   ssh2_pkt_adduint32(c->localid);
-                   ssh2_pkt_adduint32(c->v.v2.locwindow);
-                   ssh2_pkt_adduint32(0x4000UL);       /* our max pkt size */
-                   ssh2_pkt_send();
-               }
-           } else {
-               bombout(("Strange packet received: type %d", pktin.type));
-               crReturnV;
-           }
-       } else {
+           bombout(("Strange packet received: type %d", pktin->type));
+           crStopV;
+       } else if (ssh->mainchan) {
            /*
             * We have spare data. Add it to the channel buffer.
             */
-           ssh2_add_channel_data(mainchan, in, inlen);
-           try_send = TRUE;
+           ssh2_add_channel_data(ssh->mainchan, (char *)in, inlen);
+           s->try_send = TRUE;
        }
-       if (try_send) {
+       if (s->try_send) {
            int i;
            struct ssh_channel *c;
            /*
             * Try to send data on all channels if we can.
             */
-           for (i = 0; NULL != (c = index234(ssh_channels, i)); i++) {
-               int bufsize = ssh2_try_send(c);
+           for (i = 0; NULL != (c = index234(ssh->channels, i)); i++) {
+               int bufsize;
+               if (c->closes)
+                   continue;          /* don't send on closing channels */
+               bufsize = ssh2_try_send(c);
                if (bufsize == 0) {
                    switch (c->type) {
                      case CHAN_MAINSESSION:
@@ -5621,13 +7229,166 @@ static void do_ssh2_authconn(unsigned char *in, int inlen, int ispkt)
 }
 
 /*
+ * Handlers for SSH2 messages that might arrive at any moment.
+ */
+void ssh2_msg_disconnect(Ssh ssh, struct Packet *pktin)
+{
+    /* log reason code in disconnect message */
+    char *buf, *msg;
+    int nowlen, reason, msglen;
+
+    reason = ssh_pkt_getuint32(pktin);
+    ssh_pkt_getstring(pktin, &msg, &msglen);
+
+    if (reason > 0 && reason < lenof(ssh2_disconnect_reasons)) {
+       buf = dupprintf("Received disconnect message (%s)",
+                       ssh2_disconnect_reasons[reason]);
+    } else {
+       buf = dupprintf("Received disconnect message (unknown"
+                       " type %d)", reason);
+    }
+    logevent(buf);
+    sfree(buf);
+    buf = dupprintf("Disconnection message text: %n%.*s",
+                   &nowlen, msglen, msg);
+    logevent(buf);
+    bombout(("Server sent disconnect message\ntype %d (%s):\n\"%s\"",
+            reason,
+            (reason > 0 && reason < lenof(ssh2_disconnect_reasons)) ?
+            ssh2_disconnect_reasons[reason] : "unknown",
+            buf+nowlen));
+    sfree(buf);
+}
+
+void ssh2_msg_debug(Ssh ssh, struct Packet *pktin)
+{
+    /* log the debug message */
+    char *buf, *msg;
+    int msglen;
+    int always_display;
+
+    /* XXX maybe we should actually take notice of this */
+    always_display = ssh2_pkt_getbool(pktin);
+    ssh_pkt_getstring(pktin, &msg, &msglen);
+
+    buf = dupprintf("Remote debug message: %.*s", msglen, msg);
+    logevent(buf);
+    sfree(buf);
+}
+
+void ssh2_msg_something_unimplemented(Ssh ssh, struct Packet *pktin)
+{
+    struct Packet *pktout;
+    pktout = ssh2_pkt_init(SSH2_MSG_UNIMPLEMENTED);
+    ssh2_pkt_adduint32(pktout, pktin->sequence);
+    /*
+     * UNIMPLEMENTED messages MUST appear in the same order as the
+     * messages they respond to. Hence, never queue them.
+     */
+    ssh2_pkt_send_noqueue(ssh, pktout);
+}
+
+/*
  * Handle the top-level SSH2 protocol.
  */
-static void ssh2_protocol(unsigned char *in, int inlen, int ispkt)
+static void ssh2_protocol_setup(Ssh ssh)
+{
+    int i;
+
+    /*
+     * Most messages cause SSH2_MSG_UNIMPLEMENTED.
+     */
+    for (i = 0; i < 256; i++)
+       ssh->packet_dispatch[i] = ssh2_msg_something_unimplemented;
+
+    /*
+     * Any message we actually understand, we set to NULL so that
+     * the coroutines will get it.
+     */
+    ssh->packet_dispatch[SSH2_MSG_UNIMPLEMENTED] = NULL;
+    ssh->packet_dispatch[SSH2_MSG_SERVICE_REQUEST] = NULL;
+    ssh->packet_dispatch[SSH2_MSG_SERVICE_ACCEPT] = NULL;
+    ssh->packet_dispatch[SSH2_MSG_KEXINIT] = NULL;
+    ssh->packet_dispatch[SSH2_MSG_NEWKEYS] = NULL;
+    ssh->packet_dispatch[SSH2_MSG_KEXDH_INIT] = NULL;
+    ssh->packet_dispatch[SSH2_MSG_KEXDH_REPLY] = NULL;
+    /* ssh->packet_dispatch[SSH2_MSG_KEX_DH_GEX_REQUEST] = NULL; duplicate case value */
+    /* ssh->packet_dispatch[SSH2_MSG_KEX_DH_GEX_GROUP] = NULL; duplicate case value */
+    ssh->packet_dispatch[SSH2_MSG_KEX_DH_GEX_INIT] = NULL;
+    ssh->packet_dispatch[SSH2_MSG_KEX_DH_GEX_REPLY] = NULL;
+    ssh->packet_dispatch[SSH2_MSG_USERAUTH_REQUEST] = NULL;
+    ssh->packet_dispatch[SSH2_MSG_USERAUTH_FAILURE] = NULL;
+    ssh->packet_dispatch[SSH2_MSG_USERAUTH_SUCCESS] = NULL;
+    ssh->packet_dispatch[SSH2_MSG_USERAUTH_BANNER] = NULL;
+    ssh->packet_dispatch[SSH2_MSG_USERAUTH_PK_OK] = NULL;
+    /* ssh->packet_dispatch[SSH2_MSG_USERAUTH_PASSWD_CHANGEREQ] = NULL; duplicate case value */
+    /* ssh->packet_dispatch[SSH2_MSG_USERAUTH_INFO_REQUEST] = NULL; duplicate case value */
+    ssh->packet_dispatch[SSH2_MSG_USERAUTH_INFO_RESPONSE] = NULL;
+    ssh->packet_dispatch[SSH2_MSG_GLOBAL_REQUEST] = NULL;
+    ssh->packet_dispatch[SSH2_MSG_REQUEST_SUCCESS] = NULL;
+    ssh->packet_dispatch[SSH2_MSG_REQUEST_FAILURE] = NULL;
+    ssh->packet_dispatch[SSH2_MSG_CHANNEL_OPEN] = NULL;
+    ssh->packet_dispatch[SSH2_MSG_CHANNEL_OPEN_CONFIRMATION] = NULL;
+    ssh->packet_dispatch[SSH2_MSG_CHANNEL_OPEN_FAILURE] = NULL;
+    ssh->packet_dispatch[SSH2_MSG_CHANNEL_WINDOW_ADJUST] = NULL;
+    ssh->packet_dispatch[SSH2_MSG_CHANNEL_DATA] = NULL;
+    ssh->packet_dispatch[SSH2_MSG_CHANNEL_EXTENDED_DATA] = NULL;
+    ssh->packet_dispatch[SSH2_MSG_CHANNEL_EOF] = NULL;
+    ssh->packet_dispatch[SSH2_MSG_CHANNEL_CLOSE] = NULL;
+    ssh->packet_dispatch[SSH2_MSG_CHANNEL_REQUEST] = NULL;
+    ssh->packet_dispatch[SSH2_MSG_CHANNEL_SUCCESS] = NULL;
+    ssh->packet_dispatch[SSH2_MSG_CHANNEL_FAILURE] = NULL;
+
+    /*
+     * These special message types we install handlers for.
+     */
+    ssh->packet_dispatch[SSH2_MSG_DISCONNECT] = ssh2_msg_disconnect;
+    ssh->packet_dispatch[SSH2_MSG_IGNORE] = ssh_msg_ignore; /* shared with ssh1 */
+    ssh->packet_dispatch[SSH2_MSG_DEBUG] = ssh2_msg_debug;
+}
+
+static void ssh2_timer(void *ctx, long now)
+{
+    Ssh ssh = (Ssh)ctx;
+
+    if (!ssh->kex_in_progress && ssh->cfg.ssh_rekey_time != 0 &&
+       now - ssh->next_rekey >= 0) {
+       do_ssh2_transport(ssh, "timeout", -1, NULL);
+    }
+}
+
+static void ssh2_protocol(Ssh ssh, unsigned char *in, int inlen,
+                         struct Packet *pktin)
 {
-    if (do_ssh2_transport(in, inlen, ispkt) == 0)
+    if (ssh->state == SSH_STATE_CLOSED)
+       return;
+
+    if (pktin) {
+       ssh->incoming_data_size += pktin->encrypted_len;
+       if (!ssh->kex_in_progress &&
+           ssh->max_data_size != 0 &&
+           ssh->incoming_data_size > ssh->max_data_size)
+           do_ssh2_transport(ssh, "too much data received", -1, NULL);
+    }
+
+    if (pktin && ssh->packet_dispatch[pktin->type]) {
+       ssh->packet_dispatch[pktin->type](ssh, pktin);
        return;
-    do_ssh2_authconn(in, inlen, ispkt);
+    }
+
+    if (!ssh->protocol_initial_phase_done ||
+       (pktin && pktin->type >= 20 && pktin->type < 50)) {
+       if (do_ssh2_transport(ssh, in, inlen, pktin) &&
+           !ssh->protocol_initial_phase_done) {
+           ssh->protocol_initial_phase_done = TRUE;
+           /*
+            * Allow authconn to initialise itself.
+            */
+           do_ssh2_authconn(ssh, NULL, 0, NULL);
+       }
+    } else {
+       do_ssh2_authconn(ssh, in, inlen, pktin);
+    }
 }
 
 /*
@@ -5635,50 +7396,282 @@ static void ssh2_protocol(unsigned char *in, int inlen, int ispkt)
  *
  * Returns an error message, or NULL on success.
  */
-static char *ssh_init(char *host, int port, char **realhost, int nodelay)
+static const char *ssh_init(void *frontend_handle, void **backend_handle,
+                           Config *cfg,
+                           char *host, int port, char **realhost, int nodelay,
+                           int keepalive)
 {
-    char *p;
+    const char *p;
+    Ssh ssh;
+
+    ssh = snew(struct ssh_tag);
+    ssh->cfg = *cfg;                  /* STRUCTURE COPY */
+    ssh->version = 0;                 /* when not ready yet */
+    ssh->s = NULL;
+    ssh->cipher = NULL;
+    ssh->v1_cipher_ctx = NULL;
+    ssh->crcda_ctx = NULL;
+    ssh->cscipher = NULL;
+    ssh->cs_cipher_ctx = NULL;
+    ssh->sccipher = NULL;
+    ssh->sc_cipher_ctx = NULL;
+    ssh->csmac = NULL;
+    ssh->cs_mac_ctx = NULL;
+    ssh->scmac = NULL;
+    ssh->sc_mac_ctx = NULL;
+    ssh->cscomp = NULL;
+    ssh->cs_comp_ctx = NULL;
+    ssh->sccomp = NULL;
+    ssh->sc_comp_ctx = NULL;
+    ssh->kex = NULL;
+    ssh->kex_ctx = NULL;
+    ssh->hostkey = NULL;
+    ssh->exitcode = -1;
+    ssh->close_expected = FALSE;
+    ssh->state = SSH_STATE_PREPACKET;
+    ssh->size_needed = FALSE;
+    ssh->eof_needed = FALSE;
+    ssh->ldisc = NULL;
+    ssh->logctx = NULL;
+    ssh->deferred_send_data = NULL;
+    ssh->deferred_len = 0;
+    ssh->deferred_size = 0;
+    ssh->fallback_cmd = 0;
+    ssh->pkt_ctx = 0;
+    ssh->x11auth = NULL;
+    ssh->v1_compressing = FALSE;
+    ssh->v2_outgoing_sequence = 0;
+    ssh->ssh1_rdpkt_crstate = 0;
+    ssh->ssh2_rdpkt_crstate = 0;
+    ssh->do_ssh_init_crstate = 0;
+    ssh->ssh_gotdata_crstate = 0;
+    ssh->do_ssh1_connection_crstate = 0;
+    ssh->do_ssh1_login_crstate = 0;
+    ssh->do_ssh2_transport_crstate = 0;
+    ssh->do_ssh2_authconn_crstate = 0;
+    ssh->do_ssh_init_state = NULL;
+    ssh->do_ssh1_login_state = NULL;
+    ssh->do_ssh2_transport_state = NULL;
+    ssh->do_ssh2_authconn_state = NULL;
+    ssh->mainchan = NULL;
+    ssh->throttled_all = 0;
+    ssh->v1_stdout_throttling = 0;
+    ssh->queue = NULL;
+    ssh->queuelen = ssh->queuesize = 0;
+    ssh->queueing = FALSE;
+    ssh->qhead = ssh->qtail = NULL;
+    ssh->deferred_rekey_reason = NULL;
+
+    *backend_handle = ssh;
 
 #ifdef MSCRYPTOAPI
     if (crypto_startup() == 0)
        return "Microsoft high encryption pack not installed!";
 #endif
 
-    ssh_send_ok = 0;
-    ssh_editing = 0;
-    ssh_echoing = 0;
-    ssh1_throttle_count = 0;
-    ssh_overall_bufsize = 0;
-    ssh_fallback_cmd = 0;
+    ssh->frontend = frontend_handle;
+    ssh->term_width = ssh->cfg.width;
+    ssh->term_height = ssh->cfg.height;
+
+    ssh->channels = NULL;
+    ssh->rportfwds = NULL;
+    ssh->portfwds = NULL;
 
-    p = connect_to_host(host, port, realhost, nodelay);
+    ssh->send_ok = 0;
+    ssh->editing = 0;
+    ssh->echoing = 0;
+    ssh->v1_throttle_count = 0;
+    ssh->overall_bufsize = 0;
+    ssh->fallback_cmd = 0;
+
+    ssh->protocol = NULL;
+
+    ssh->protocol_initial_phase_done = FALSE;
+
+    ssh->pinger = NULL;
+
+    ssh->incoming_data_size = ssh->outgoing_data_size =
+       ssh->deferred_data_size = 0L;
+    ssh->max_data_size = parse_blocksize(ssh->cfg.ssh_rekey_data);
+    ssh->kex_in_progress = FALSE;
+
+    p = connect_to_host(ssh, host, port, realhost, nodelay, keepalive);
     if (p != NULL)
        return p;
 
+    random_ref();
+
     return NULL;
 }
 
+static void ssh_free(void *handle)
+{
+    Ssh ssh = (Ssh) handle;
+    struct ssh_channel *c;
+    struct ssh_rportfwd *pf;
+
+    if (ssh->v1_cipher_ctx)
+       ssh->cipher->free_context(ssh->v1_cipher_ctx);
+    if (ssh->cs_cipher_ctx)
+       ssh->cscipher->free_context(ssh->cs_cipher_ctx);
+    if (ssh->sc_cipher_ctx)
+       ssh->sccipher->free_context(ssh->sc_cipher_ctx);
+    if (ssh->cs_mac_ctx)
+       ssh->csmac->free_context(ssh->cs_mac_ctx);
+    if (ssh->sc_mac_ctx)
+       ssh->scmac->free_context(ssh->sc_mac_ctx);
+    if (ssh->cs_comp_ctx) {
+       if (ssh->cscomp)
+           ssh->cscomp->compress_cleanup(ssh->cs_comp_ctx);
+       else
+           zlib_compress_cleanup(ssh->cs_comp_ctx);
+    }
+    if (ssh->sc_comp_ctx) {
+       if (ssh->sccomp)
+           ssh->sccomp->decompress_cleanup(ssh->sc_comp_ctx);
+       else
+           zlib_decompress_cleanup(ssh->sc_comp_ctx);
+    }
+    if (ssh->kex_ctx)
+       dh_cleanup(ssh->kex_ctx);
+    sfree(ssh->savedhost);
+
+    while (ssh->queuelen-- > 0)
+       ssh_free_packet(ssh->queue[ssh->queuelen]);
+    sfree(ssh->queue);
+
+    while (ssh->qhead) {
+       struct queued_handler *qh = ssh->qhead;
+       ssh->qhead = qh->next;
+       sfree(ssh->qhead);
+    }
+    ssh->qhead = ssh->qtail = NULL;
+
+    if (ssh->channels) {
+       while ((c = delpos234(ssh->channels, 0)) != NULL) {
+           switch (c->type) {
+             case CHAN_X11:
+               if (c->u.x11.s != NULL)
+                   x11_close(c->u.x11.s);
+               break;
+             case CHAN_SOCKDATA:
+               if (c->u.pfd.s != NULL)
+                   pfd_close(c->u.pfd.s);
+               break;
+           }
+           sfree(c);
+       }
+       freetree234(ssh->channels);
+       ssh->channels = NULL;
+    }
+
+    if (ssh->rportfwds) {
+       while ((pf = delpos234(ssh->rportfwds, 0)) != NULL)
+           sfree(pf);
+       freetree234(ssh->rportfwds);
+       ssh->rportfwds = NULL;
+    }
+    sfree(ssh->deferred_send_data);
+    if (ssh->x11auth)
+       x11_free_auth(ssh->x11auth);
+    sfree(ssh->do_ssh_init_state);
+    sfree(ssh->do_ssh1_login_state);
+    sfree(ssh->do_ssh2_transport_state);
+    sfree(ssh->do_ssh2_authconn_state);
+    if (ssh->crcda_ctx) {
+       crcda_free_context(ssh->crcda_ctx);
+       ssh->crcda_ctx = NULL;
+    }
+    if (ssh->s)
+       ssh_do_close(ssh, TRUE);
+    expire_timer_context(ssh);
+    if (ssh->pinger)
+       pinger_free(ssh->pinger);
+    sfree(ssh);
+
+    random_unref();
+}
+
+/*
+ * Reconfigure the SSH backend.
+ */
+static void ssh_reconfig(void *handle, Config *cfg)
+{
+    Ssh ssh = (Ssh) handle;
+    char *rekeying = NULL, rekey_mandatory = FALSE;
+    unsigned long old_max_data_size;
+
+    pinger_reconfig(ssh->pinger, &ssh->cfg, cfg);
+    ssh_setup_portfwd(ssh, cfg);
+
+    if (ssh->cfg.ssh_rekey_time != cfg->ssh_rekey_time &&
+       cfg->ssh_rekey_time != 0) {
+       long new_next = ssh->last_rekey + cfg->ssh_rekey_time*60*TICKSPERSEC;
+       long now = GETTICKCOUNT();
+
+       if (new_next - now < 0) {
+           rekeying = "timeout shortened";
+       } else {
+           ssh->next_rekey = schedule_timer(new_next - now, ssh2_timer, ssh);
+       }
+    }
+
+    old_max_data_size = ssh->max_data_size;
+    ssh->max_data_size = parse_blocksize(cfg->ssh_rekey_data);
+    if (old_max_data_size != ssh->max_data_size &&
+       ssh->max_data_size != 0) {
+       if (ssh->outgoing_data_size > ssh->max_data_size ||
+           ssh->incoming_data_size > ssh->max_data_size)
+           rekeying = "data limit lowered";
+    }
+
+    if (ssh->cfg.compression != cfg->compression) {
+       rekeying = "compression setting changed";
+       rekey_mandatory = TRUE;
+    }
+
+    if (ssh->cfg.ssh2_des_cbc != cfg->ssh2_des_cbc ||
+       memcmp(ssh->cfg.ssh_cipherlist, cfg->ssh_cipherlist,
+              sizeof(ssh->cfg.ssh_cipherlist))) {
+       rekeying = "cipher settings changed";
+       rekey_mandatory = TRUE;
+    }
+
+    ssh->cfg = *cfg;                  /* STRUCTURE COPY */
+
+    if (rekeying) {
+       if (!ssh->kex_in_progress) {
+           do_ssh2_transport(ssh, rekeying, -1, NULL);
+       } else if (rekey_mandatory) {
+           ssh->deferred_rekey_reason = rekeying;
+       }
+    }
+}
+
 /*
  * Called to send data down the Telnet connection.
  */
-static int ssh_send(char *buf, int len)
+static int ssh_send(void *handle, char *buf, int len)
 {
-    if (s == NULL || ssh_protocol == NULL)
+    Ssh ssh = (Ssh) handle;
+
+    if (ssh == NULL || ssh->s == NULL || ssh->protocol == NULL)
        return 0;
 
-    ssh_protocol(buf, len, 0);
+    ssh->protocol(ssh, (unsigned char *)buf, len, 0);
 
-    return ssh_sendbuffer();
+    return ssh_sendbuffer(ssh);
 }
 
 /*
  * Called to query the current amount of buffered stdin data.
  */
-static int ssh_sendbuffer(void)
+static int ssh_sendbuffer(void *handle)
 {
+    Ssh ssh = (Ssh) handle;
     int override_value;
 
-    if (s == NULL || ssh_protocol == NULL)
+    if (ssh == NULL || ssh->s == NULL || ssh->protocol == NULL)
        return 0;
 
     /*
@@ -5686,16 +7679,17 @@ static int ssh_sendbuffer(void)
      * size on that to any individual buffer on the stdin channel.
      */
     override_value = 0;
-    if (ssh_throttled_all)
-       override_value = ssh_overall_bufsize;
+    if (ssh->throttled_all)
+       override_value = ssh->overall_bufsize;
 
-    if (ssh_version == 1) {
+    if (ssh->version == 1) {
        return override_value;
-    } else if (ssh_version == 2) {
-       if (!mainchan || mainchan->closes > 0)
+    } else if (ssh->version == 2) {
+       if (!ssh->mainchan || ssh->mainchan->closes > 0)
            return override_value;
        else
-           return override_value + bufchain_size(&mainchan->v.v2.outbuffer);
+           return (override_value +
+                   bufchain_size(&ssh->mainchan->v.v2.outbuffer));
     }
 
     return 0;
@@ -5704,32 +7698,39 @@ static int ssh_sendbuffer(void)
 /*
  * Called to set the size of the window from SSH's POV.
  */
-static void ssh_size(void)
+static void ssh_size(void *handle, int width, int height)
 {
-    switch (ssh_state) {
+    Ssh ssh = (Ssh) handle;
+    struct Packet *pktout;
+
+    ssh->term_width = width;
+    ssh->term_height = height;
+
+    switch (ssh->state) {
       case SSH_STATE_BEFORE_SIZE:
       case SSH_STATE_PREPACKET:
       case SSH_STATE_CLOSED:
        break;                         /* do nothing */
       case SSH_STATE_INTERMED:
-       size_needed = TRUE;            /* buffer for later */
+       ssh->size_needed = TRUE;       /* buffer for later */
        break;
       case SSH_STATE_SESSION:
-       if (!cfg.nopty) {
-           if (ssh_version == 1) {
-               send_packet(SSH1_CMSG_WINDOW_SIZE,
-                           PKT_INT, rows, PKT_INT, cols,
+       if (!ssh->cfg.nopty) {
+           if (ssh->version == 1) {
+               send_packet(ssh, SSH1_CMSG_WINDOW_SIZE,
+                           PKT_INT, ssh->term_height,
+                           PKT_INT, ssh->term_width,
                            PKT_INT, 0, PKT_INT, 0, PKT_END);
-           } else {
-               ssh2_pkt_init(SSH2_MSG_CHANNEL_REQUEST);
-               ssh2_pkt_adduint32(mainchan->remoteid);
-               ssh2_pkt_addstring("window-change");
-               ssh2_pkt_addbool(0);
-               ssh2_pkt_adduint32(cols);
-               ssh2_pkt_adduint32(rows);
-               ssh2_pkt_adduint32(0);
-               ssh2_pkt_adduint32(0);
-               ssh2_pkt_send();
+           } else if (ssh->mainchan) {
+               pktout = ssh2_pkt_init(SSH2_MSG_CHANNEL_REQUEST);
+               ssh2_pkt_adduint32(pktout, ssh->mainchan->remoteid);
+               ssh2_pkt_addstring(pktout, "window-change");
+               ssh2_pkt_addbool(pktout, 0);
+               ssh2_pkt_adduint32(pktout, ssh->term_width);
+               ssh2_pkt_adduint32(pktout, ssh->term_height);
+               ssh2_pkt_adduint32(pktout, 0);
+               ssh2_pkt_adduint32(pktout, 0);
+               ssh2_pkt_send(ssh, pktout);
            }
        }
        break;
@@ -5737,58 +7738,179 @@ static void ssh_size(void)
 }
 
 /*
+ * Return a list of the special codes that make sense in this
+ * protocol.
+ */
+static const struct telnet_special *ssh_get_specials(void *handle)
+{
+    static const struct telnet_special ssh1_ignore_special[] = {
+       {"IGNORE message", TS_NOP}
+    };
+    static const struct telnet_special ssh2_transport_specials[] = {
+       {"IGNORE message", TS_NOP},
+       {"Repeat key exchange", TS_REKEY},
+    };
+    static const struct telnet_special ssh2_session_specials[] = {
+       {NULL, TS_SEP},
+       {"Break", TS_BRK},
+       /* These are the signal names defined by draft-ietf-secsh-connect-23.
+        * They include all the ISO C signals, but are a subset of the POSIX
+        * required signals. */
+       {"SIGINT (Interrupt)", TS_SIGINT},
+       {"SIGTERM (Terminate)", TS_SIGTERM},
+       {"SIGKILL (Kill)", TS_SIGKILL},
+       {"SIGQUIT (Quit)", TS_SIGQUIT},
+       {"SIGHUP (Hangup)", TS_SIGHUP},
+       {"More signals", TS_SUBMENU},
+         {"SIGABRT", TS_SIGABRT}, {"SIGALRM", TS_SIGALRM},
+         {"SIGFPE",  TS_SIGFPE},  {"SIGILL",  TS_SIGILL},
+         {"SIGPIPE", TS_SIGPIPE}, {"SIGSEGV", TS_SIGSEGV},
+         {"SIGUSR1", TS_SIGUSR1}, {"SIGUSR2", TS_SIGUSR2},
+       {NULL, TS_EXITMENU}
+    };
+    static const struct telnet_special specials_end[] = {
+       {NULL, TS_EXITMENU}
+    };
+    /* XXX review this length for any changes: */
+    static struct telnet_special ssh_specials[lenof(ssh2_transport_specials) +
+                                             lenof(ssh2_session_specials) +
+                                             lenof(specials_end)];
+    Ssh ssh = (Ssh) handle;
+    int i = 0;
+#define ADD_SPECIALS(name) \
+    do { \
+       assert((i + lenof(name)) <= lenof(ssh_specials)); \
+       memcpy(&ssh_specials[i], name, sizeof name); \
+       i += lenof(name); \
+    } while(0)
+
+    if (ssh->version == 1) {
+       /* Don't bother offering IGNORE if we've decided the remote
+        * won't cope with it, since we wouldn't bother sending it if
+        * asked anyway. */
+       if (!(ssh->remote_bugs & BUG_CHOKES_ON_SSH1_IGNORE))
+           ADD_SPECIALS(ssh1_ignore_special);
+    } else if (ssh->version == 2) {
+       ADD_SPECIALS(ssh2_transport_specials);
+       if (ssh->mainchan)
+           ADD_SPECIALS(ssh2_session_specials);
+    } /* else we're not ready yet */
+
+    if (i) {
+       ADD_SPECIALS(specials_end);
+       return ssh_specials;
+    } else {
+       return NULL;
+    }
+#undef ADD_SPECIALS
+}
+
+/*
  * Send Telnet special codes. TS_EOF is useful for `plink', so you
  * can send an EOF and collect resulting output (e.g. `plink
  * hostname sort').
  */
-static void ssh_special(Telnet_Special code)
+static void ssh_special(void *handle, Telnet_Special code)
 {
+    Ssh ssh = (Ssh) handle;
+    struct Packet *pktout;
+
     if (code == TS_EOF) {
-       if (ssh_state != SSH_STATE_SESSION) {
+       if (ssh->state != SSH_STATE_SESSION) {
            /*
             * Buffer the EOF in case we are pre-SESSION, so we can
             * send it as soon as we reach SESSION.
             */
            if (code == TS_EOF)
-               eof_needed = TRUE;
+               ssh->eof_needed = TRUE;
            return;
        }
-       if (ssh_version == 1) {
-           send_packet(SSH1_CMSG_EOF, PKT_END);
-       } else {
-           ssh2_pkt_init(SSH2_MSG_CHANNEL_EOF);
-           ssh2_pkt_adduint32(mainchan->remoteid);
-           ssh2_pkt_send();
+       if (ssh->version == 1) {
+           send_packet(ssh, SSH1_CMSG_EOF, PKT_END);
+       } else if (ssh->mainchan) {
+           struct Packet *pktout = ssh2_pkt_init(SSH2_MSG_CHANNEL_EOF);
+           ssh2_pkt_adduint32(pktout, ssh->mainchan->remoteid);
+           ssh2_pkt_send(ssh, pktout);
        }
        logevent("Sent EOF message");
-    } else if (code == TS_PING) {
-       if (ssh_state == SSH_STATE_CLOSED
-           || ssh_state == SSH_STATE_PREPACKET) return;
-       if (ssh_version == 1) {
-           send_packet(SSH1_MSG_IGNORE, PKT_STR, "", PKT_END);
+    } else if (code == TS_PING || code == TS_NOP) {
+       if (ssh->state == SSH_STATE_CLOSED
+           || ssh->state == SSH_STATE_PREPACKET) return;
+       if (ssh->version == 1) {
+           if (!(ssh->remote_bugs & BUG_CHOKES_ON_SSH1_IGNORE))
+               send_packet(ssh, SSH1_MSG_IGNORE, PKT_STR, "", PKT_END);
        } else {
-           ssh2_pkt_init(SSH2_MSG_IGNORE);
-           ssh2_pkt_addstring_start();
-           ssh2_pkt_send();
+           pktout = ssh2_pkt_init(SSH2_MSG_IGNORE);
+           ssh2_pkt_addstring_start(pktout);
+           ssh2_pkt_send_noqueue(ssh, pktout);
+       }
+    } else if (code == TS_REKEY) {
+       if (!ssh->kex_in_progress && ssh->version == 2) {
+           do_ssh2_transport(ssh, "at user request", -1, NULL);
+       }
+    } else if (code == TS_BRK) {
+       if (ssh->state == SSH_STATE_CLOSED
+           || ssh->state == SSH_STATE_PREPACKET) return;
+       if (ssh->version == 1) {
+           logevent("Unable to send BREAK signal in SSH1");
+       } else if (ssh->mainchan) {
+           pktout = ssh2_pkt_init(SSH2_MSG_CHANNEL_REQUEST);
+           ssh2_pkt_adduint32(pktout, ssh->mainchan->remoteid);
+           ssh2_pkt_addstring(pktout, "break");
+           ssh2_pkt_addbool(pktout, 0);
+           ssh2_pkt_adduint32(pktout, 0);   /* default break length */
+           ssh2_pkt_send(ssh, pktout);
        }
     } else {
-       /* do nothing */
+       /* Is is a POSIX signal? */
+       char *signame = NULL;
+       if (code == TS_SIGABRT) signame = "ABRT";
+       if (code == TS_SIGALRM) signame = "ALRM";
+       if (code == TS_SIGFPE)  signame = "FPE";
+       if (code == TS_SIGHUP)  signame = "HUP";
+       if (code == TS_SIGILL)  signame = "ILL";
+       if (code == TS_SIGINT)  signame = "INT";
+       if (code == TS_SIGKILL) signame = "KILL";
+       if (code == TS_SIGPIPE) signame = "PIPE";
+       if (code == TS_SIGQUIT) signame = "QUIT";
+       if (code == TS_SIGSEGV) signame = "SEGV";
+       if (code == TS_SIGTERM) signame = "TERM";
+       if (code == TS_SIGUSR1) signame = "USR1";
+       if (code == TS_SIGUSR2) signame = "USR2";
+       /* The SSH-2 protocol does in principle support arbitrary named
+        * signals, including signame@domain, but we don't support those. */
+       if (signame) {
+           /* It's a signal. */
+           if (ssh->version == 2 && ssh->mainchan) {
+               pktout = ssh2_pkt_init(SSH2_MSG_CHANNEL_REQUEST);
+               ssh2_pkt_adduint32(pktout, ssh->mainchan->remoteid);
+               ssh2_pkt_addstring(pktout, "signal");
+               ssh2_pkt_addbool(pktout, 0);
+               ssh2_pkt_addstring(pktout, signame);
+               ssh2_pkt_send(ssh, pktout);
+               logeventf(ssh, "Sent signal SIG%s", signame);
+           }
+       } else {
+           /* Never heard of it. Do nothing */
+       }
     }
 }
 
-void *new_sock_channel(Socket s)
+void *new_sock_channel(void *handle, Socket s)
 {
+    Ssh ssh = (Ssh) handle;
     struct ssh_channel *c;
-    c = smalloc(sizeof(struct ssh_channel));
+    c = snew(struct ssh_channel);
+    c->ssh = ssh;
 
     if (c) {
        c->remoteid = -1;              /* to be set when open confirmed */
-       c->localid = alloc_channel_id();
+       c->localid = alloc_channel_id(ssh);
        c->closes = 0;
        c->type = CHAN_SOCKDATA_DORMANT;/* identify channel type */
        c->u.pfd.s = s;
        bufchain_init(&c->v.v2.outbuffer);
-       add234(ssh_channels, c);
+       add234(ssh->channels, c);
     }
     return c;
 }
@@ -5797,90 +7919,136 @@ void *new_sock_channel(Socket s)
  * This is called when stdout/stderr (the entity to which
  * from_backend sends data) manages to clear some backlog.
  */
-void ssh_unthrottle(int bufsize)
+static void ssh_unthrottle(void *handle, int bufsize)
 {
-    if (ssh_version == 1) {
-       if (ssh1_stdout_throttling && bufsize < SSH1_BUFFER_LIMIT) {
-           ssh1_stdout_throttling = 0;
-           ssh1_throttle(-1);
+    Ssh ssh = (Ssh) handle;
+    if (ssh->version == 1) {
+       if (ssh->v1_stdout_throttling && bufsize < SSH1_BUFFER_LIMIT) {
+           ssh->v1_stdout_throttling = 0;
+           ssh1_throttle(ssh, -1);
        }
     } else {
-       if (mainchan && mainchan->closes == 0)
-           ssh2_set_window(mainchan, OUR_V2_WINSIZE - bufsize);
+       if (ssh->mainchan && ssh->mainchan->closes == 0)
+           ssh2_set_window(ssh->mainchan, OUR_V2_WINSIZE - bufsize);
     }
 }
 
 void ssh_send_port_open(void *channel, char *hostname, int port, char *org)
 {
     struct ssh_channel *c = (struct ssh_channel *)channel;
-    char buf[1024];
+    Ssh ssh = c->ssh;
+    struct Packet *pktout;
 
-    sprintf(buf, "Opening forwarded connection to %.512s:%d", hostname, port);
-    logevent(buf);
+    logeventf(ssh, "Opening forwarded connection to %s:%d", hostname, port);
 
-    if (ssh_version == 1) {
-       send_packet(SSH1_MSG_PORT_OPEN,
+    if (ssh->version == 1) {
+       send_packet(ssh, SSH1_MSG_PORT_OPEN,
                    PKT_INT, c->localid,
                    PKT_STR, hostname,
                    PKT_INT, port,
-                   //PKT_STR, <org:orgport>,
+                   /* PKT_STR, <org:orgport>, */
                    PKT_END);
     } else {
-       ssh2_pkt_init(SSH2_MSG_CHANNEL_OPEN);
-       ssh2_pkt_addstring("direct-tcpip");
-       ssh2_pkt_adduint32(c->localid);
+       pktout = ssh2_pkt_init(SSH2_MSG_CHANNEL_OPEN);
+       ssh2_pkt_addstring(pktout, "direct-tcpip");
+       ssh2_pkt_adduint32(pktout, c->localid);
        c->v.v2.locwindow = OUR_V2_WINSIZE;
-       ssh2_pkt_adduint32(c->v.v2.locwindow);/* our window size */
-       ssh2_pkt_adduint32(0x4000UL);      /* our max pkt size */
-       ssh2_pkt_addstring(hostname);
-       ssh2_pkt_adduint32(port);
+       ssh2_pkt_adduint32(pktout, c->v.v2.locwindow);/* our window size */
+       ssh2_pkt_adduint32(pktout, OUR_V2_MAXPKT);      /* our max pkt size */
+       ssh2_pkt_addstring(pktout, hostname);
+       ssh2_pkt_adduint32(pktout, port);
        /*
         * We make up values for the originator data; partly it's
         * too much hassle to keep track, and partly I'm not
         * convinced the server should be told details like that
         * about my local network configuration.
         */
-       ssh2_pkt_addstring("client-side-connection");
-       ssh2_pkt_adduint32(0);
-       ssh2_pkt_send();
+       ssh2_pkt_addstring(pktout, "client-side-connection");
+       ssh2_pkt_adduint32(pktout, 0);
+       ssh2_pkt_send(ssh, pktout);
     }
 }
 
-
-static Socket ssh_socket(void)
+static Socket ssh_socket(void *handle)
 {
-    return s;
+    Ssh ssh = (Ssh) handle;
+    return ssh->s;
 }
 
-static int ssh_sendok(void)
+static int ssh_sendok(void *handle)
 {
-    return ssh_send_ok;
+    Ssh ssh = (Ssh) handle;
+    return ssh->send_ok;
 }
 
-static int ssh_ldisc(int option)
+static int ssh_ldisc(void *handle, int option)
 {
+    Ssh ssh = (Ssh) handle;
     if (option == LD_ECHO)
-       return ssh_echoing;
+       return ssh->echoing;
     if (option == LD_EDIT)
-       return ssh_editing;
+       return ssh->editing;
     return FALSE;
 }
 
-static int ssh_return_exitcode(void)
+static void ssh_provide_ldisc(void *handle, void *ldisc)
+{
+    Ssh ssh = (Ssh) handle;
+    ssh->ldisc = ldisc;
+}
+
+static void ssh_provide_logctx(void *handle, void *logctx)
+{
+    Ssh ssh = (Ssh) handle;
+    ssh->logctx = logctx;
+}
+
+static int ssh_return_exitcode(void *handle)
+{
+    Ssh ssh = (Ssh) handle;
+    if (ssh->s != NULL)
+        return -1;
+    else
+        return (ssh->exitcode >= 0 ? ssh->exitcode : 0);
+}
+
+/*
+ * cfg_info for SSH is the currently running version of the
+ * protocol. (1 for 1; 2 for 2; 0 for not-decided-yet.)
+ */
+static int ssh_cfg_info(void *handle)
+{
+    Ssh ssh = (Ssh) handle;
+    return ssh->version;
+}
+
+/*
+ * Gross hack: pscp will try to start SFTP but fall back to scp1 if
+ * that fails. This variable is the means by which scp.c can reach
+ * into the SSH code and find out which one it got.
+ */
+extern int ssh_fallback_cmd(void *handle)
 {
-    return ssh_exitcode;
+    Ssh ssh = (Ssh) handle;
+    return ssh->fallback_cmd;
 }
 
 Backend ssh_backend = {
     ssh_init,
+    ssh_free,
+    ssh_reconfig,
     ssh_send,
     ssh_sendbuffer,
     ssh_size,
     ssh_special,
+    ssh_get_specials,
     ssh_socket,
     ssh_return_exitcode,
     ssh_sendok,
     ssh_ldisc,
+    ssh_provide_ldisc,
+    ssh_provide_logctx,
     ssh_unthrottle,
+    ssh_cfg_info,
     22
 };