Robustness fixes for KEXINIT handling and others. In particular, I've
[u/mdw/putty] / ssh.c
diff --git a/ssh.c b/ssh.c
index f8ba521..2df7110 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
 
-/* uncomment this for packet level debugging */
-/* #define DUMP_PACKETS */
-
-#define logevent(s) { logevent(s); \
-                      if ((flags & FLAG_STDERR) && (flags & FLAG_VERBOSE)) \
-                      { fprintf(stderr, "%s\n", s); fflush(stderr); } }
-
-#define bombout(msg) ( ssh_state = SSH_STATE_CLOSED, \
-                          (s ? sk_close(s), s = NULL : 0), \
-                          connection_fatal msg )
-
 #define SSH1_MSG_DISCONNECT                       1    /* 0x1 */
 #define SSH1_SMSG_PUBLIC_KEY                      2    /* 0x2 */
 #define SSH1_CMSG_SESSION_KEY                     3    /* 0x3 */
 #define SSH2_MSG_CHANNEL_SUCCESS                  99   /* 0x63 */
 #define SSH2_MSG_CHANNEL_FAILURE                  100  /* 0x64 */
 
+/*
+ * 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_DHGEX            0x0002
+#define SSH2_PKTCTX_PUBLICKEY        0x0010
+#define SSH2_PKTCTX_PASSWORD         0x0020
+#define SSH2_PKTCTX_KBDINTER         0x0040
+#define SSH2_PKTCTX_AUTH_MASK        0x00F0
+
 #define SSH2_DISCONNECT_HOST_NOT_ALLOWED_TO_CONNECT 1  /* 0x1 */
 #define SSH2_DISCONNECT_PROTOCOL_ERROR            2    /* 0x2 */
 #define SSH2_DISCONNECT_KEY_EXCHANGE_FAILED       3    /* 0x3 */
@@ -159,6 +158,101 @@ static const char *const ssh2_disconnect_reasons[] = {
  */
 #define BUG_CHOKES_ON_SSH1_IGNORE                 1
 #define BUG_SSH2_HMAC                             2
+#define BUG_NEEDS_SSH1_PLAIN_PASSWORD            4
+#define BUG_CHOKES_ON_RSA                        8
+#define BUG_SSH2_RSA_PADDING                    16
+#define BUG_SSH2_DERIVEKEY                       32
+#define BUG_SSH2_DH_GEX                          64
+
+#define translate(x) if (type == x) return #x
+#define translatec(x,ctx) if (type == x && (pkt_ctx & ctx)) return #x
+char *ssh1_pkt_type(int type)
+{
+    translate(SSH1_MSG_DISCONNECT);
+    translate(SSH1_SMSG_PUBLIC_KEY);
+    translate(SSH1_CMSG_SESSION_KEY);
+    translate(SSH1_CMSG_USER);
+    translate(SSH1_CMSG_AUTH_RSA);
+    translate(SSH1_SMSG_AUTH_RSA_CHALLENGE);
+    translate(SSH1_CMSG_AUTH_RSA_RESPONSE);
+    translate(SSH1_CMSG_AUTH_PASSWORD);
+    translate(SSH1_CMSG_REQUEST_PTY);
+    translate(SSH1_CMSG_WINDOW_SIZE);
+    translate(SSH1_CMSG_EXEC_SHELL);
+    translate(SSH1_CMSG_EXEC_CMD);
+    translate(SSH1_SMSG_SUCCESS);
+    translate(SSH1_SMSG_FAILURE);
+    translate(SSH1_CMSG_STDIN_DATA);
+    translate(SSH1_SMSG_STDOUT_DATA);
+    translate(SSH1_SMSG_STDERR_DATA);
+    translate(SSH1_CMSG_EOF);
+    translate(SSH1_SMSG_EXIT_STATUS);
+    translate(SSH1_MSG_CHANNEL_OPEN_CONFIRMATION);
+    translate(SSH1_MSG_CHANNEL_OPEN_FAILURE);
+    translate(SSH1_MSG_CHANNEL_DATA);
+    translate(SSH1_MSG_CHANNEL_CLOSE);
+    translate(SSH1_MSG_CHANNEL_CLOSE_CONFIRMATION);
+    translate(SSH1_SMSG_X11_OPEN);
+    translate(SSH1_CMSG_PORT_FORWARD_REQUEST);
+    translate(SSH1_MSG_PORT_OPEN);
+    translate(SSH1_CMSG_AGENT_REQUEST_FORWARDING);
+    translate(SSH1_SMSG_AGENT_OPEN);
+    translate(SSH1_MSG_IGNORE);
+    translate(SSH1_CMSG_EXIT_CONFIRMATION);
+    translate(SSH1_CMSG_X11_REQUEST_FORWARDING);
+    translate(SSH1_CMSG_AUTH_RHOSTS_RSA);
+    translate(SSH1_MSG_DEBUG);
+    translate(SSH1_CMSG_REQUEST_COMPRESSION);
+    translate(SSH1_CMSG_AUTH_TIS);
+    translate(SSH1_SMSG_AUTH_TIS_CHALLENGE);
+    translate(SSH1_CMSG_AUTH_TIS_RESPONSE);
+    translate(SSH1_CMSG_AUTH_CCARD);
+    translate(SSH1_SMSG_AUTH_CCARD_CHALLENGE);
+    translate(SSH1_CMSG_AUTH_CCARD_RESPONSE);
+    return "unknown";
+}
+char *ssh2_pkt_type(int pkt_ctx, int type)
+{
+    translate(SSH2_MSG_DISCONNECT);
+    translate(SSH2_MSG_IGNORE);
+    translate(SSH2_MSG_UNIMPLEMENTED);
+    translate(SSH2_MSG_DEBUG);
+    translate(SSH2_MSG_SERVICE_REQUEST);
+    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_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);
+    translatec(SSH2_MSG_KEX_DH_GEX_REPLY, SSH2_PKTCTX_DHGEX);
+    translate(SSH2_MSG_USERAUTH_REQUEST);
+    translate(SSH2_MSG_USERAUTH_FAILURE);
+    translate(SSH2_MSG_USERAUTH_SUCCESS);
+    translate(SSH2_MSG_USERAUTH_BANNER);
+    translatec(SSH2_MSG_USERAUTH_PK_OK, SSH2_PKTCTX_PUBLICKEY);
+    translatec(SSH2_MSG_USERAUTH_PASSWD_CHANGEREQ, SSH2_PKTCTX_PASSWORD);
+    translatec(SSH2_MSG_USERAUTH_INFO_REQUEST, SSH2_PKTCTX_KBDINTER);
+    translatec(SSH2_MSG_USERAUTH_INFO_RESPONSE, SSH2_PKTCTX_KBDINTER);
+    translate(SSH2_MSG_GLOBAL_REQUEST);
+    translate(SSH2_MSG_REQUEST_SUCCESS);
+    translate(SSH2_MSG_REQUEST_FAILURE);
+    translate(SSH2_MSG_CHANNEL_OPEN);
+    translate(SSH2_MSG_CHANNEL_OPEN_CONFIRMATION);
+    translate(SSH2_MSG_CHANNEL_OPEN_FAILURE);
+    translate(SSH2_MSG_CHANNEL_WINDOW_ADJUST);
+    translate(SSH2_MSG_CHANNEL_DATA);
+    translate(SSH2_MSG_CHANNEL_EXTENDED_DATA);
+    translate(SSH2_MSG_CHANNEL_EOF);
+    translate(SSH2_MSG_CHANNEL_CLOSE);
+    translate(SSH2_MSG_CHANNEL_REQUEST);
+    translate(SSH2_MSG_CHANNEL_SUCCESS);
+    translate(SSH2_MSG_CHANNEL_FAILURE);
+    return "unknown";
+}
+#undef translate
+#undef translatec
 
 #define GET_32BIT(cp) \
     (((unsigned long)(unsigned char)(cp)[0] << 24) | \
@@ -175,39 +269,56 @@ static const char *const ssh2_disconnect_reasons[] = {
 enum { PKT_END, PKT_INT, PKT_CHAR, PKT_DATA, PKT_STR, PKT_BIGNUM };
 
 /* 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
+#define crBegin(v)     { int *crLine = &v; switch(v) { case 0:;
+#define crState(t) \
+    struct t *s; \
+    if (!ssh->t) ssh->t = smalloc(sizeof(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 *);
+typedef struct ssh_tag *Ssh;
+
+extern char *x11_init(Socket *, char *, void *, 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_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 char *pfd_addforward(char *desthost, int destport, int port,
+                           void *backhandle);
 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(Ssh, int pkt_type);
+static void ssh2_pkt_addbool(Ssh, unsigned char value);
+static void ssh2_pkt_adduint32(Ssh, unsigned long value);
+static void ssh2_pkt_addstring_start(Ssh);
+static void ssh2_pkt_addstring_str(Ssh, char *data);
+static void ssh2_pkt_addstring_data(Ssh, char *data, int len);
+static void ssh2_pkt_addstring(Ssh, char *data);
+static char *ssh2_mpint_fmt(Bignum b, int *len);
+static void ssh2_pkt_addmp(Ssh, Bignum b);
+static int ssh2_pkt_construct(Ssh);
+static void ssh2_pkt_send(Ssh);
+
 /*
  * Buffer management constants. There are several of these for
  * various different purposes:
@@ -233,18 +344,6 @@ extern void pfd_override_throttle(Socket s, int enable);
 #define SSH_MAX_BACKLOG 32768
 #define OUR_V2_WINSIZE 16384
 
-/*
- * Ciphers for SSH2. We miss out single-DES because it isn't
- * supported; also 3DES and Blowfish are both done differently from
- * SSH1. (3DES uses outer chaining; Blowfish has the opposite
- * endianness and different-sized keys.)
- */
-const static struct ssh2_ciphers *ciphers[] = {
-    &ssh2_aes,
-    &ssh2_blowfish,
-    &ssh2_3des,
-};
-
 const static struct ssh_kex *kex_algs[] = {
     &ssh_diffiehellman_gex,
     &ssh_diffiehellman
@@ -252,19 +351,28 @@ const static struct ssh_kex *kex_algs[] = {
 
 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
@@ -273,23 +381,27 @@ 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[] = {
@@ -308,8 +420,19 @@ 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 {
@@ -379,87 +502,170 @@ struct Packet {
     long maxlen;
 };
 
-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];
-int (*ssh_get_line) (const char *prompt, char *str, int maxlen,
-                    int is_pw) = NULL;
-
-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 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;
-
-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, int ispkt);
+static void ssh2_protocol(Ssh ssh, unsigned char *in, int inlen, int ispkt);
+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 int ssh_sendbuffer(void *handle);
 
-static struct rdpkt1_state_tag {
+struct rdpkt1_state_tag {
     long len, pad, biglen, to_read;
     unsigned long realcrc, gotcrc;
     unsigned char *p;
     int i;
     int chunk;
-} rdpkt1_state;
+};
 
-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 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 term_width, term_height;
+
+    tree234 *channels;                /* indexed by local id */
+    struct ssh_channel *mainchan;      /* primary session channel */
+    int exitcode;
+
+    tree234 *rportfwds;
+
+    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 pktin;
+    struct Packet pktout;
+    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;
+
+    char *portfwd_strptr;
+    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 ssh1_protocol_crstate;
+    int do_ssh1_login_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;
+
+    void (*protocol) (Ssh ssh, unsigned char *in, int inlen, int ispkt);
+    int (*s_rdpkt) (Ssh ssh, unsigned char **data, int *datalen);
+};
+
+#define logevent(s) do { \
+    logevent(ssh->frontend, s); \
+    if ((flags & FLAG_STDERR) && (flags & FLAG_VERBOSE)) { \
+       fprintf(stderr, "%s\n", s); \
+       fflush(stderr); \
+    } \
+} while (0)
+
+/* logevent, only printf-formatted. */
+void logeventf(Ssh ssh, char *fmt, ...)
+{
+    va_list ap;
+    char *buf;
+
+    va_start(ap, fmt);
+    buf = dupvprintf(fmt, ap);
+    va_end(ap);
+    logevent(buf);
+    if ((flags & FLAG_STDERR) && (flags & FLAG_VERBOSE)) {
+       fprintf(stderr, "%s\n", buf);
+       fflush(stderr);
+    }
+    sfree(buf);
+}
+
+#define bombout(msg) ( ssh->state = SSH_STATE_CLOSED, \
+                          (ssh->s ? sk_close(ssh->s), ssh->s = NULL : 0), \
+                          logeventf msg, connection_fatal msg )
 
 static int ssh_channelcmp(void *av, void *bv)
 {
@@ -500,7 +706,7 @@ static int ssh_rportcmp_ssh2(void *av, void *bv)
 {
     struct ssh_rportfwd *a = (struct ssh_rportfwd *) av;
     struct ssh_rportfwd *b = (struct ssh_rportfwd *) bv;
-    int i;
+
     if (a->sport > b->sport)
        return +1;
     if (a->sport < b->sport)
@@ -508,7 +714,7 @@ static int ssh_rportcmp_ssh2(void *av, void *bv)
     return 0;
 }
 
-static int alloc_channel_id(void)
+static int alloc_channel_id(Ssh ssh)
 {
     const unsigned CHANNEL_NUMBER_OFFSET = 256;
     unsigned low, high, mid;
@@ -523,13 +729,13 @@ 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
@@ -541,12 +747,12 @@ 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, char *buf, int len)
 {
     if ((flags & FLAG_STDERR)) {
        int i;
@@ -555,23 +761,23 @@ 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, 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, char *buf)
 {
-    c_write(buf, strlen(buf));
+    c_write(ssh, buf, strlen(buf));
 }
 
 /*
@@ -582,16 +788,16 @@ static void c_write_str(char *buf)
  * Return the additional nr of bytes needed, or 0 when
  * a complete packet is available.
  */
-static int ssh1_rdpkt(unsigned char **data, int *datalen)
+static int 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:
 
-    pktin.type = 0;
-    pktin.length = 0;
+    ssh->pktin.type = 0;
+    ssh->pktin.length = 0;
 
     for (st->i = st->len = 0; st->i < 4; st->i++) {
        while ((*datalen) == 0)
@@ -600,26 +806,17 @@ static int ssh1_rdpkt(unsigned char **data, int *datalen)
        (*data)++, (*datalen)--;
     }
 
-#ifdef FWHACK
-    if (st->len == 0x52656d6f) {       /* "Remo"te server has closed ... */
-       st->len = 0x300;               /* big enough to carry to end */
-    }
-#endif
-
     st->pad = 8 - (st->len % 8);
     st->biglen = st->len + st->pad;
-    pktin.length = st->len - 5;
+    ssh->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 (ssh->pktin.maxlen < st->biglen) {
+       ssh->pktin.maxlen = st->biglen;
+       ssh->pktin.data = srealloc(ssh->pktin.data, st->biglen + APIEXTRA);
     }
 
     st->to_read = st->biglen;
-    st->p = pktin.data;
+    st->p = ssh->pktin.data;
     while (st->to_read > 0) {
        st->chunk = st->to_read;
        while ((*datalen) == 0)
@@ -633,122 +830,117 @@ static int ssh1_rdpkt(unsigned char **data, int *datalen)
        st->to_read -= st->chunk;
     }
 
-    if (cipher)
-       cipher->decrypt(pktin.data, st->biglen);
-#ifdef DUMP_PACKETS
-    debug(("Got packet len=%d pad=%d\n", st->len, st->pad));
-    dmemdump(pktin.data, st->biglen);
-#endif
+    if (ssh->cipher && detect_attack(ssh->crcda_ctx, ssh->pktin.data,
+                                    st->biglen, NULL)) {
+        bombout((ssh,"Network attack (CRC compensation) detected!"));
+        crReturn(0);
+    }
+
+    if (ssh->cipher)
+       ssh->cipher->decrypt(ssh->v1_cipher_ctx, ssh->pktin.data, st->biglen);
 
-    st->realcrc = crc32(pktin.data, st->biglen - 4);
-    st->gotcrc = GET_32BIT(pktin.data + st->biglen - 4);
+    st->realcrc = crc32(ssh->pktin.data, st->biglen - 4);
+    st->gotcrc = GET_32BIT(ssh->pktin.data + st->biglen - 4);
     if (st->gotcrc != st->realcrc) {
-       bombout(("Incorrect CRC received on packet"));
+       bombout((ssh,"Incorrect CRC received on packet"));
        crReturn(0);
     }
 
-    pktin.body = pktin.data + st->pad + 1;
+    ssh->pktin.body = ssh->pktin.data + st->pad + 1;
 
-    if (ssh1_compressing) {
+    if (ssh->v1_compressing) {
        unsigned char *decompblk;
        int decomplen;
-#ifdef DUMP_PACKETS
-       debug(("Packet payload pre-decompression:\n"));
-       dmemdump(pktin.body - 1, pktin.length + 1);
-#endif
-       zlib_decompress_block(pktin.body - 1, pktin.length + 1,
+       zlib_decompress_block(ssh->sc_comp_ctx,
+                             ssh->pktin.body - 1, ssh->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 (ssh->pktin.maxlen < st->pad + decomplen) {
+           ssh->pktin.maxlen = st->pad + decomplen;
+           ssh->pktin.data = srealloc(ssh->pktin.data,
+                                      ssh->pktin.maxlen + APIEXTRA);
+           ssh->pktin.body = ssh->pktin.data + st->pad + 1;
        }
 
-       memcpy(pktin.body - 1, decompblk, decomplen);
+       memcpy(ssh->pktin.body - 1, decompblk, decomplen);
        sfree(decompblk);
-       pktin.length = decomplen - 1;
-#ifdef DUMP_PACKETS
-       debug(("Packet payload post-decompression:\n"));
-       dmemdump(pktin.body - 1, pktin.length + 1);
-#endif
+       ssh->pktin.length = decomplen - 1;
     }
 
-    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 strlen = GET_32BIT(pktin.body);
-       if (strlen + 4 != pktin.length) {
-           bombout(("Received data packet with bogus string length"));
+    ssh->pktin.type = ssh->pktin.body[-1];
+
+    if (ssh->logctx)
+       log_packet(ssh->logctx,
+                  PKT_INCOMING, ssh->pktin.type,
+                  ssh1_pkt_type(ssh->pktin.type),
+                  ssh->pktin.body, ssh->pktin.length);
+
+    if (ssh->pktin.type == SSH1_SMSG_STDOUT_DATA ||
+       ssh->pktin.type == SSH1_SMSG_STDERR_DATA ||
+       ssh->pktin.type == SSH1_MSG_DEBUG ||
+       ssh->pktin.type == SSH1_SMSG_AUTH_TIS_CHALLENGE ||
+       ssh->pktin.type == SSH1_SMSG_AUTH_CCARD_CHALLENGE) {
+       long stringlen = GET_32BIT(ssh->pktin.body);
+       if (stringlen + 4 != ssh->pktin.length) {
+           bombout((ssh,"Received data packet with bogus string length"));
            crReturn(0);
        }
     }
 
-    pktin.type = pktin.body[-1];
-
-    if (pktin.type == SSH1_MSG_DEBUG) {
+    if (ssh->pktin.type == SSH1_MSG_DEBUG) {
        /* log debug message */
-       char buf[80];
-       int strlen = GET_32BIT(pktin.body);
-       strcpy(buf, "Remote: ");
-       if (strlen > 70)
-           strlen = 70;
-       memcpy(buf + 8, pktin.body + 4, strlen);
-       buf[8 + strlen] = '\0';
+       char buf[512];
+       int stringlen = GET_32BIT(ssh->pktin.body);
+       strcpy(buf, "Remote debug message: ");
+       if (stringlen > 480)
+           stringlen = 480;
+       memcpy(buf + 8, ssh->pktin.body + 4, stringlen);
+       buf[8 + stringlen] = '\0';
        logevent(buf);
        goto next_packet;
-    } else if (pktin.type == SSH1_MSG_IGNORE) {
+    } else if (ssh->pktin.type == SSH1_MSG_IGNORE) {
        /* do nothing */
        goto next_packet;
     }
 
-    if (pktin.type == SSH1_MSG_DISCONNECT) {
+    if (ssh->pktin.type == SSH1_MSG_DISCONNECT) {
        /* log reason code in disconnect message */
        char buf[256];
-       unsigned msglen = GET_32BIT(pktin.body);
+       unsigned msglen = GET_32BIT(ssh->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);
+       memcpy(buf + nowlen, ssh->pktin.body + 4, msglen);
        buf[nowlen + msglen] = '\0';
-       logevent(buf);
+       /* logevent(buf); (this is now done within the bombout macro) */
+       bombout((ssh,"Server sent disconnect message:\n\"%s\"", buf+nowlen));
+       crReturn(0);
     }
 
     crFinish(0);
 }
 
-static int ssh2_rdpkt(unsigned char **data, int *datalen)
+static int 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;
+    ssh->pktin.type = 0;
+    ssh->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");
+    if (ssh->pktin.maxlen < st->cipherblk) {
+       ssh->pktin.maxlen = st->cipherblk;
+       ssh->pktin.data = srealloc(ssh->pktin.data, st->cipherblk + APIEXTRA);
     }
 
     /*
@@ -758,49 +950,49 @@ 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)++;
+       ssh->pktin.data[st->i] = *(*data)++;
        (*datalen)--;
     }
-#ifdef FWHACK
-    if (!memcmp(pktin.data, "Remo", 4)) {      /* "Remo"te server has closed ... */
-       /* FIXME */
-    }
-#endif
-    if (sccipher)
-       sccipher->decrypt(pktin.data, st->cipherblk);
+
+    if (ssh->sccipher)
+       ssh->sccipher->decrypt(ssh->sc_cipher_ctx,
+                              ssh->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(ssh->pktin.data);
+    st->pad = ssh->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((ssh,"Incoming packet was garbled on decryption"));
+       crReturn(0);
+    }
 
     /*
      * This enables us to deduce the payload length.
      */
     st->payload = st->len - st->pad - 1;
 
-    pktin.length = st->payload + 5;
+    ssh->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.
      */
-    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");
+    if (ssh->pktin.maxlen < st->packetlen + st->maclen) {
+       ssh->pktin.maxlen = st->packetlen + st->maclen;
+       ssh->pktin.data = srealloc(ssh->pktin.data,
+                                  ssh->pktin.maxlen + APIEXTRA);
     }
 
     /*
@@ -810,26 +1002,22 @@ static int ssh2_rdpkt(unsigned char **data, int *datalen)
         st->i++) {
        while ((*datalen) == 0)
            crReturn(st->packetlen + st->maclen - st->i);
-       pktin.data[st->i] = *(*data)++;
+       ssh->pktin.data[st->i] = *(*data)++;
        (*datalen)--;
     }
     /* Decrypt everything _except_ the MAC. */
-    if (sccipher)
-       sccipher->decrypt(pktin.data + st->cipherblk,
-                         st->packetlen - st->cipherblk);
-
-#ifdef DUMP_PACKETS
-    debug(("Got packet len=%d pad=%d\n", st->len, st->pad));
-    dmemdump(pktin.data, st->packetlen);
-#endif
+    if (ssh->sccipher)
+       ssh->sccipher->decrypt(ssh->sc_cipher_ctx,
+                              ssh->pktin.data + st->cipherblk,
+                              st->packetlen - st->cipherblk);
 
     /*
      * Check the MAC.
      */
-    if (scmac
-       && !scmac->verify(pktin.data, st->len + 4,
-                         st->incoming_sequence)) {
-       bombout(("Incorrect MAC received on packet"));
+    if (ssh->scmac
+       && !ssh->scmac->verify(ssh->sc_mac_ctx, ssh->pktin.data, st->len + 4,
+                              st->incoming_sequence)) {
+       bombout((ssh,"Incorrect MAC received on packet"));
        crReturn(0);
     }
     st->incoming_sequence++;          /* whether or not we MACed */
@@ -840,63 +1028,133 @@ 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,
+                                   ssh->pktin.data + 5, ssh->pktin.length - 5,
+                                   &newpayload, &newlen)) {
+           if (ssh->pktin.maxlen < newlen + 5) {
+               ssh->pktin.maxlen = newlen + 5;
+               ssh->pktin.data = srealloc(ssh->pktin.data,
+                                          ssh->pktin.maxlen + APIEXTRA);
            }
-           pktin.length = 5 + newlen;
-           memcpy(pktin.data + 5, newpayload, newlen);
-#ifdef DUMP_PACKETS
-           debug(("Post-decompression payload:\n"));
-           dmemdump(pktin.data + 5, newlen);
-#endif
-
+           ssh->pktin.length = 5 + newlen;
+           memcpy(ssh->pktin.data + 5, newpayload, newlen);
            sfree(newpayload);
        }
     }
 
-    pktin.savedpos = 6;
-    pktin.type = pktin.data[5];
-
-    if (pktin.type == SSH2_MSG_IGNORE || pktin.type == SSH2_MSG_DEBUG)
-       goto next_packet;              /* FIXME: print DEBUG message */
-
-    if (pktin.type == 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);
+    ssh->pktin.savedpos = 6;
+    ssh->pktin.type = ssh->pktin.data[5];
+
+    if (ssh->logctx)
+       log_packet(ssh->logctx, PKT_INCOMING, ssh->pktin.type,
+                  ssh2_pkt_type(ssh->pkt_ctx, ssh->pktin.type),
+                  ssh->pktin.data+6, ssh->pktin.length-6);
+
+    switch (ssh->pktin.type) {
+        /*
+         * These packets we must handle instantly.
+         */
+      case SSH2_MSG_DISCONNECT:
+        {
+            /* log reason code in disconnect message */
+            char *buf;
+           int nowlen;
+            int reason = GET_32BIT(ssh->pktin.data + 6);
+            unsigned msglen = GET_32BIT(ssh->pktin.data + 10);
+
+            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",
+                           msglen, &nowlen, ssh->pktin.data + 14);
+            logevent(buf);
+            bombout((ssh,"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);
+            crReturn(0);
+        }
+        break;
+      case SSH2_MSG_IGNORE:
+       goto next_packet;
+      case SSH2_MSG_DEBUG:
+       {
+           /* log the debug message */
+           char buf[512];
+           /* int display = ssh->pktin.body[6]; */
+           int stringlen = GET_32BIT(ssh->pktin.data+7);
+           int prefix;
+           strcpy(buf, "Remote debug message: ");
+           prefix = strlen(buf);
+           if (stringlen > (int)(sizeof(buf)-prefix-1))
+               stringlen = sizeof(buf)-prefix-1;
+           memcpy(buf + prefix, ssh->pktin.data + 11, stringlen);
+           buf[prefix + stringlen] = '\0';
+           logevent(buf);
        }
-       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);
+        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(ssh, SSH2_MSG_UNIMPLEMENTED);
+       ssh2_pkt_adduint32(ssh, st->incoming_sequence - 1);
+       ssh2_pkt_send(ssh);
+        break;
     }
 
     crFinish(0);
 }
 
-static void ssh1_pktout_size(int len)
+static void ssh1_pktout_size(Ssh ssh, int len)
 {
     int pad, biglen;
 
@@ -904,101 +1162,91 @@ 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;
+    ssh->pktout.length = len - 5;
+    if (ssh->pktout.maxlen < biglen) {
+       ssh->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));
+       ssh->pktout.data = srealloc(ssh->pktout.data, biglen + 12);
 #else
-       pktout.data = (pktout.data == NULL ? smalloc(biglen + 4) :
-                      srealloc(pktout.data, biglen + 4));
+       ssh->pktout.data = srealloc(ssh->pktout.data, biglen + 4);
 #endif
-       if (!pktout.data)
-           fatalbox("Out of memory");
     }
-    pktout.body = pktout.data + 4 + pad + 1;
+    ssh->pktout.body = ssh->pktout.data + 4 + pad + 1;
 }
 
-static void s_wrpkt_start(int type, int len)
+static void s_wrpkt_start(Ssh ssh, int type, int len)
 {
-    ssh1_pktout_size(len);
-    pktout.type = type;
+    ssh1_pktout_size(ssh, len);
+    ssh->pktout.type = type;
 }
 
-static int s_wrpkt_prepare(void)
+static int s_wrpkt_prepare(Ssh ssh)
 {
     int pad, len, biglen, i;
     unsigned long crc;
 
-    pktout.body[-1] = pktout.type;
+    ssh->pktout.body[-1] = ssh->pktout.type;
 
-#ifdef DUMP_PACKETS
-    debug(("Packet payload pre-compression:\n"));
-    dmemdump(pktout.body - 1, pktout.length + 1);
-#endif
+    if (ssh->logctx)
+       log_packet(ssh->logctx, PKT_OUTGOING, ssh->pktout.type,
+                  ssh1_pkt_type(ssh->pktout.type),
+                  ssh->pktout.body, ssh->pktout.length);
 
-    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,
+                           ssh->pktout.body - 1, ssh->pktout.length + 1,
                            &compblk, &complen);
-       ssh1_pktout_size(complen - 1);
-       memcpy(pktout.body - 1, compblk, complen);
+       ssh1_pktout_size(ssh, complen - 1);
+       memcpy(ssh->pktout.body - 1, compblk, complen);
        sfree(compblk);
-#ifdef DUMP_PACKETS
-       debug(("Packet payload post-compression:\n"));
-       dmemdump(pktout.body - 1, pktout.length + 1);
-#endif
     }
 
-    len = pktout.length + 5;          /* type and CRC */
+    len = ssh->pktout.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);
-
-#ifdef DUMP_PACKETS
-    debug(("Sending packet len=%d\n", biglen + 4));
-    dmemdump(pktout.data, biglen + 4);
-#endif
-    if (cipher)
-       cipher->encrypt(pktout.data + 4, biglen);
+       ssh->pktout.data[i + 4] = random_byte();
+    crc = crc32(ssh->pktout.data + 4, biglen - 4);
+    PUT_32BIT(ssh->pktout.data + biglen, crc);
+    PUT_32BIT(ssh->pktout.data, len);
+
+    if (ssh->cipher)
+       ssh->cipher->encrypt(ssh->v1_cipher_ctx, ssh->pktout.data + 4, biglen);
 
     return biglen + 4;
 }
 
-static void s_wrpkt(void)
+static void s_wrpkt(Ssh ssh)
 {
     int len, backlog;
-    len = s_wrpkt_prepare();
-    backlog = sk_write(spktout.data, len);
+    len = s_wrpkt_prepare(ssh);
+    backlog = sk_write(ssh->s, ssh->pktout.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)
 {
     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);
+    if (ssh->deferred_len + len > ssh->deferred_size) {
+       ssh->deferred_size = ssh->deferred_len + len + 128;
+       ssh->deferred_send_data = srealloc(ssh->deferred_send_data,
+                                          ssh->deferred_size);
     }
-    memcpy(deferred_send_data + deferred_len, pktout.data, len);
-    deferred_len += len;
+    memcpy(ssh->deferred_send_data + ssh->deferred_len, ssh->pktout.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 void construct_packet(Ssh ssh, int pkttype, va_list ap1, va_list ap2)
 {
     unsigned char *p, *argp, argchar;
     unsigned long argint;
@@ -1013,7 +1261,7 @@ 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:
@@ -1035,8 +1283,8 @@ static void construct_packet(int pkttype, va_list ap1, va_list ap2)
        }
     }
 
-    s_wrpkt_start(pkttype, pktlen);
-    p = pktout.body;
+    s_wrpkt_start(ssh, pkttype, pktlen);
+    p = ssh->pktout.body;
 
     while ((argtype = va_arg(ap2, int)) != PKT_END) {
        switch (argtype) {
@@ -1046,7 +1294,7 @@ static void construct_packet(int pkttype, va_list ap1, va_list ap2)
            p += 4;
            break;
          case PKT_CHAR:
-           argchar = va_arg(ap2, unsigned char);
+           argchar = (unsigned char) va_arg(ap2, int);
            *p = argchar;
            p++;
            break;
@@ -1071,22 +1319,22 @@ static void construct_packet(int pkttype, va_list ap1, va_list ap2)
     }
 }
 
-static void send_packet(int pkttype, ...)
+static void send_packet(Ssh ssh, int pkttype, ...)
 {
     va_list ap1, ap2;
     va_start(ap1, pkttype);
     va_start(ap2, pkttype);
-    construct_packet(pkttype, ap1, ap2);
-    s_wrpkt();
+    construct_packet(ssh, pkttype, ap1, ap2);
+    s_wrpkt(ssh);
 }
 
-static void defer_packet(int pkttype, ...)
+static void defer_packet(Ssh ssh, int pkttype, ...)
 {
     va_list ap1, ap2;
     va_start(ap1, pkttype);
     va_start(ap2, pkttype);
-    construct_packet(pkttype, ap1, ap2);
-    s_wrpkt_defer();
+    construct_packet(ssh, pkttype, ap1, ap2);
+    s_wrpkt_defer(ssh);
 }
 
 static int ssh_versioncmp(char *a, char *b)
@@ -1109,7 +1357,6 @@ static int ssh_versioncmp(char *a, char *b)
     return 0;
 }
 
-
 /*
  * Utility routines for putting an SSH-protocol `string' and
  * `uint32' into a SHA state.
@@ -1133,66 +1380,62 @@ static void sha_uint32(SHA_State * s, unsigned i)
 /*
  * SSH2 packet construction functions.
  */
-static void ssh2_pkt_ensure(int length)
+static void ssh2_pkt_ensure(Ssh ssh, 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)
+    if (ssh->pktout.maxlen < length) {
+       ssh->pktout.maxlen = length + 256;
+       ssh->pktout.data = srealloc(ssh->pktout.data,
+                                   ssh->pktout.maxlen + APIEXTRA);
+       if (!ssh->pktout.data)
            fatalbox("Out of memory");
     }
 }
-static void ssh2_pkt_adddata(void *data, int len)
+static void ssh2_pkt_adddata(Ssh ssh, void *data, int len)
 {
-    pktout.length += len;
-    ssh2_pkt_ensure(pktout.length);
-    memcpy(pktout.data + pktout.length - len, data, len);
+    ssh->pktout.length += len;
+    ssh2_pkt_ensure(ssh, ssh->pktout.length);
+    memcpy(ssh->pktout.data + ssh->pktout.length - len, data, len);
 }
-static void ssh2_pkt_addbyte(unsigned char byte)
+static void ssh2_pkt_addbyte(Ssh ssh, unsigned char byte)
 {
-    ssh2_pkt_adddata(&byte, 1);
+    ssh2_pkt_adddata(ssh, &byte, 1);
 }
-static void ssh2_pkt_init(int pkt_type)
+static void ssh2_pkt_init(Ssh ssh, int pkt_type)
 {
-    pktout.length = 5;
-    ssh2_pkt_addbyte((unsigned char) pkt_type);
+    ssh->pktout.length = 5;
+    ssh2_pkt_addbyte(ssh, (unsigned char) pkt_type);
 }
-static void ssh2_pkt_addbool(unsigned char value)
+static void ssh2_pkt_addbool(Ssh ssh, unsigned char value)
 {
-    ssh2_pkt_adddata(&value, 1);
+    ssh2_pkt_adddata(ssh, &value, 1);
 }
-static void ssh2_pkt_adduint32(unsigned long value)
+static void ssh2_pkt_adduint32(Ssh ssh, unsigned long value)
 {
     unsigned char x[4];
     PUT_32BIT(x, value);
-    ssh2_pkt_adddata(x, 4);
+    ssh2_pkt_adddata(ssh, x, 4);
 }
-static void ssh2_pkt_addstring_start(void)
+static void ssh2_pkt_addstring_start(Ssh ssh)
 {
-    ssh2_pkt_adduint32(0);
-    pktout.savedpos = pktout.length;
+    ssh2_pkt_adduint32(ssh, 0);
+    ssh->pktout.savedpos = ssh->pktout.length;
 }
-static void ssh2_pkt_addstring_str(char *data)
+static void ssh2_pkt_addstring_str(Ssh ssh, char *data)
 {
-    ssh2_pkt_adddata(data, strlen(data));
-    PUT_32BIT(pktout.data + pktout.savedpos - 4,
-             pktout.length - pktout.savedpos);
+    ssh2_pkt_adddata(ssh, data, strlen(data));
+    PUT_32BIT(ssh->pktout.data + ssh->pktout.savedpos - 4,
+             ssh->pktout.length - ssh->pktout.savedpos);
 }
-static void ssh2_pkt_addstring_data(char *data, int len)
+static void ssh2_pkt_addstring_data(Ssh ssh, char *data, int len)
 {
-    ssh2_pkt_adddata(data, len);
-    PUT_32BIT(pktout.data + pktout.savedpos - 4,
-             pktout.length - pktout.savedpos);
+    ssh2_pkt_adddata(ssh, data, len);
+    PUT_32BIT(ssh->pktout.data + ssh->pktout.savedpos - 4,
+             ssh->pktout.length - ssh->pktout.savedpos);
 }
-static void ssh2_pkt_addstring(char *data)
+static void ssh2_pkt_addstring(Ssh ssh, char *data)
 {
-    ssh2_pkt_addstring_start();
-    ssh2_pkt_addstring_str(data);
+    ssh2_pkt_addstring_start(ssh);
+    ssh2_pkt_addstring_str(ssh, data);
 }
 static char *ssh2_mpint_fmt(Bignum b, int *len)
 {
@@ -1211,40 +1454,42 @@ 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(Ssh ssh, 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(ssh);
+    ssh2_pkt_addstring_data(ssh, 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.
+ * ssh->pktout.data. Total length is returned.
  */
-static int ssh2_pkt_construct(void)
+static int ssh2_pkt_construct(Ssh ssh)
 {
     int cipherblk, maclen, padding, i;
-    static unsigned long outgoing_sequence = 0;
+
+    if (ssh->logctx)
+       log_packet(ssh->logctx, PKT_OUTGOING, ssh->pktout.data[5],
+                  ssh2_pkt_type(ssh->pkt_ctx, ssh->pktout.data[5]),
+                  ssh->pktout.data + 6, ssh->pktout.length - 6);
 
     /*
      * Compress packet payload.
      */
-#ifdef DUMP_PACKETS
-    debug(("Pre-compression payload:\n"));
-    dmemdump(pktout.data + 5, pktout.length - 5);
-#endif
     {
        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, ssh->pktout.data + 5,
+                                 ssh->pktout.length - 5,
+                                 &newpayload, &newlen)) {
+           ssh->pktout.length = 5;
+           ssh2_pkt_adddata(ssh, newpayload, newlen);
            sfree(newpayload);
        }
     }
@@ -1253,45 +1498,42 @@ 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 - (ssh->pktout.length + padding) % cipherblk) % cipherblk;
+    maclen = ssh->csmac ? ssh->csmac->len : 0;
+    ssh2_pkt_ensure(ssh, ssh->pktout.length + padding + maclen);
+    ssh->pktout.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 */
-
-#ifdef DUMP_PACKETS
-    debug(("Sending packet len=%d\n", pktout.length + padding));
-    dmemdump(pktout.data, pktout.length + padding);
-#endif
-
-    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;
+       ssh->pktout.data[ssh->pktout.length + i] = random_byte();
+    PUT_32BIT(ssh->pktout.data, ssh->pktout.length + padding - 4);
+    if (ssh->csmac)
+       ssh->csmac->generate(ssh->cs_mac_ctx, ssh->pktout.data,
+                            ssh->pktout.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,
+                              ssh->pktout.data, ssh->pktout.length + padding);
+
+    /* Ready-to-send packet starts at ssh->pktout.data. We return length. */
+    return ssh->pktout.length + padding + maclen;
 }
 
 /*
  * Construct and send an SSH2 packet immediately.
  */
-static void ssh2_pkt_send(void)
+static void ssh2_pkt_send(Ssh ssh)
 {
     int len;
     int backlog;
-    len = ssh2_pkt_construct();
-    backlog = sk_write(spktout.data, len);
+    len = ssh2_pkt_construct(ssh);
+    backlog = sk_write(ssh->s, ssh->pktout.data, len);
     if (backlog > SSH_MAX_BACKLOG)
-       ssh_throttle_all(1, backlog);
+       ssh_throttle_all(ssh, 1, backlog);
 }
 
 /*
@@ -1305,30 +1547,31 @@ static void ssh2_pkt_send(void)
  * NOT be used as an m4-style `defer' allowing packets to be
  * constructed in one order and sent in another.
  */
-static void ssh2_pkt_defer(void)
+static void ssh2_pkt_defer(Ssh ssh)
 {
-    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);
+    int len = ssh2_pkt_construct(ssh);
+    if (ssh->deferred_len + len > ssh->deferred_size) {
+       ssh->deferred_size = ssh->deferred_len + len + 128;
+       ssh->deferred_send_data = srealloc(ssh->deferred_send_data,
+                                          ssh->deferred_size);
     }
-    memcpy(deferred_send_data + deferred_len, pktout.data, len);
-    deferred_len += len;
+    memcpy(ssh->deferred_send_data + ssh->deferred_len, ssh->pktout.data, len);
+    ssh->deferred_len += len;
 }
 
 /*
  * Send the whole deferred data block constructed by
  * ssh2_pkt_defer() or SSH1's defer_packet().
  */
-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, 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);
 }
 
 #if 0
@@ -1357,47 +1600,52 @@ static void sha_mpint(SHA_State * s, Bignum b)
 /*
  * SSH2 packet decode functions.
  */
-static unsigned long ssh2_pkt_getuint32(void)
+static unsigned long ssh2_pkt_getuint32(Ssh ssh)
 {
     unsigned long value;
-    if (pktin.length - pktin.savedpos < 4)
+    if (ssh->pktin.length - ssh->pktin.savedpos < 4)
        return 0;                      /* arrgh, no way to decline (FIXME?) */
-    value = GET_32BIT(pktin.data + pktin.savedpos);
-    pktin.savedpos += 4;
+    value = GET_32BIT(ssh->pktin.data + ssh->pktin.savedpos);
+    ssh->pktin.savedpos += 4;
     return value;
 }
-static int ssh2_pkt_getbool(void)
+static int ssh2_pkt_getbool(Ssh ssh)
 {
     unsigned long value;
-    if (pktin.length - pktin.savedpos < 1)
+    if (ssh->pktin.length - ssh->pktin.savedpos < 1)
        return 0;                      /* arrgh, no way to decline (FIXME?) */
-    value = pktin.data[pktin.savedpos] != 0;
-    pktin.savedpos++;
+    value = ssh->pktin.data[ssh->pktin.savedpos] != 0;
+    ssh->pktin.savedpos++;
     return value;
 }
-static void ssh2_pkt_getstring(char **p, int *length)
+static void ssh2_pkt_getstring(Ssh ssh, char **p, int *length)
 {
+    int len;
     *p = NULL;
-    if (pktin.length - pktin.savedpos < 4)
+    *length = 0;
+    if (ssh->pktin.length - ssh->pktin.savedpos < 4)
        return;
-    *length = GET_32BIT(pktin.data + pktin.savedpos);
-    pktin.savedpos += 4;
-    if (pktin.length - pktin.savedpos < *length)
+    len = GET_32BIT(ssh->pktin.data + ssh->pktin.savedpos);
+    if (len < 0)
        return;
-    *p = pktin.data + pktin.savedpos;
-    pktin.savedpos += *length;
+    *length = len;
+    ssh->pktin.savedpos += 4;
+    if (ssh->pktin.length - ssh->pktin.savedpos < *length)
+       return;
+    *p = ssh->pktin.data + ssh->pktin.savedpos;
+    ssh->pktin.savedpos += *length;
 }
-static Bignum ssh2_pkt_getmp(void)
+static Bignum ssh2_pkt_getmp(Ssh ssh)
 {
     char *p;
     int length;
     Bignum b;
 
-    ssh2_pkt_getstring(&p, &length);
+    ssh2_pkt_getstring(ssh, &p, &length);
     if (!p)
        return NULL;
     if (p[0] & 0x80) {
-       bombout(("internal error: Can't handle negative mpints"));
+       bombout((ssh,"internal error: Can't handle negative mpints"));
        return NULL;
     }
     b = bignum_from_bytes(p, length);
@@ -1405,159 +1653,306 @@ static Bignum ssh2_pkt_getmp(void)
 }
 
 /*
+ * Helper function to add an SSH2 signature blob to a packet.
+ * Expects to be shown the public key blob as well as the signature
+ * blob. Normally works just like ssh2_pkt_addstring, but will
+ * fiddle with the signature packet if necessary for
+ * BUG_SSH2_RSA_PADDING.
+ */
+static void ssh2_add_sigblob(Ssh ssh, void *pkblob_v, int pkblob_len,
+                            void *sigblob_v, int sigblob_len)
+{
+    unsigned char *pkblob = (unsigned char *)pkblob_v;
+    unsigned char *sigblob = (unsigned char *)sigblob_v;
+
+    /* dmemdump(pkblob, pkblob_len); */
+    /* dmemdump(sigblob, sigblob_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) &&
+       (GET_32BIT(pkblob) == 7 && !memcmp(pkblob+4, "ssh-rsa", 7))) {
+       int pos, len, siglen;
+
+       /*
+        * Find the byte length of the modulus.
+        */
+
+       pos = 4+7;                     /* skip over "ssh-rsa" */
+       pos += 4 + GET_32BIT(pkblob+pos);   /* skip over exponent */
+       len = GET_32BIT(pkblob+pos);   /* find length of modulus */
+       pos += 4;                      /* find modulus itself */
+       while (len > 0 && pkblob[pos] == 0)
+           len--, pos++;
+       /* debug(("modulus length is %d\n", len)); */
+
+       /*
+        * Now find the signature integer.
+        */
+       pos = 4+7;                     /* skip over "ssh-rsa" */
+       siglen = GET_32BIT(sigblob+pos);
+       /* debug(("signature length is %d\n", siglen)); */
+
+       if (len != siglen) {
+           unsigned char newlen[4];
+           ssh2_pkt_addstring_start(ssh);
+           ssh2_pkt_addstring_data(ssh, sigblob, pos);
+           /* dmemdump(sigblob, pos); */
+           pos += 4;                  /* point to start of actual sig */
+           PUT_32BIT(newlen, len);
+           ssh2_pkt_addstring_data(ssh, newlen, 4);
+           /* dmemdump(newlen, 4); */
+           newlen[0] = 0;
+           while (len-- > siglen) {
+               ssh2_pkt_addstring_data(ssh, newlen, 1);
+               /* dmemdump(newlen, 1); */
+           }
+           ssh2_pkt_addstring_data(ssh, sigblob+pos, siglen);
+           /* dmemdump(sigblob+pos, siglen); */
+           return;
+       }
+
+       /* Otherwise fall through and do it the easy way. */
+    }
+
+    ssh2_pkt_addstring_start(ssh);
+    ssh2_pkt_addstring_data(ssh, 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;
     imp += strcspn(imp, "-");
-    if (*imp)
-       imp++;
+    if (*imp) imp++;
     imp += strcspn(imp, "-");
-    if (*imp)
-       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")) {
+    if (cfg.sshbug_ignore1 == BUG_ON ||
+       (cfg.sshbug_ignore1 == BUG_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")))) {
        /*
         * 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 (!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 (cfg.sshbug_plainpw1 == BUG_ON ||
+       (cfg.sshbug_plainpw1 == BUG_AUTO &&
+        (!strcmp(imp, "Cisco-1.25")))) {
+       /*
+        * 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;
+       logevent("We believe remote version needs a plain SSH1 password");
+    }
+
+    if (cfg.sshbug_rsa1 == BUG_ON ||
+       (cfg.sshbug_rsa1 == BUG_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;
+       logevent("We believe remote version can't handle RSA authentication");
+    }
+
+    if (cfg.sshbug_hmac2 == BUG_ON ||
+       (cfg.sshbug_hmac2 == BUG_AUTO &&
+        (!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)))) {
        /*
         * 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 (cfg.sshbug_derivekey2 == BUG_ON ||
+       (cfg.sshbug_derivekey2 == BUG_AUTO &&
+        (!strncmp(imp, "2.0.", 4)))) {
+       /*
+        * 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 (cfg.sshbug_rsapad2 == BUG_ON ||
+       (cfg.sshbug_rsapad2 == BUG_AUTO &&
+        ((!strncmp(imp, "OpenSSH_2.", 10) && imp[10]>='5' && imp[10]<='9') ||
+         (!strncmp(imp, "OpenSSH_3.", 10) && imp[10]>='0' && imp[10]<='2')))){
+       /*
+        * These versions have the SSH2 RSA padding bug.
+        */
+       ssh->remote_bugs |= BUG_SSH2_RSA_PADDING;
+       logevent("We believe remote version has SSH2 RSA padding bug");
+    }
+
+    if (cfg.sshbug_dhgex2 == BUG_ON) {
+       /*
+        * These versions have the SSH2 DH GEX bug.
+        */
+       ssh->remote_bugs |= BUG_SSH2_DH_GEX;
+       logevent("We believe remote version has SSH2 DH group exchange bug");
+    }
 }
 
-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;
+    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 */
     }
 
-    vstring = smalloc(16);
-    vstrsize = 16;
-    strcpy(vstring, "SSH-");
-    vslen = 4;
-    i = 0;
+    s->vstrsize = 16;
+    s->vstring = smalloc(s->vstrsize);
+    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 = srealloc(s->vstring, s->vstrsize);
        }
-       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;
+               s->version[s->i] = '\0';
+               s->i = -1;
+           } else if (s->i < sizeof(s->version) - 1)
+               s->version[s->i++] = c;
        } else if (c == '\n')
            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);
-    sprintf(vlog, "Server version: %s", vstring);
-    ssh_detect_bugs(vstring);
-    vlog[strcspn(vlog, "\r\n")] = '\0';
-    logevent(vlog);
-    sfree(vlog);
+    s->vstring[s->vslen] = 0;
+    s->vstring[strcspn(s->vstring, "\r\n")] = '\0';/* remove EOL chars */
+    {
+       char *vlog;
+       vlog = smalloc(20 + s->vslen);
+       sprintf(vlog, "Server version: %s", s->vstring);
+       logevent(vlog);
+       sfree(vlog);
+    }
+    ssh_detect_bugs(ssh, s->vstring);
 
     /*
-     * Server version "1.99" means we can choose whether we use v1
-     * or v2 protocol. Choice is based on cfg.sshprot.
+     * Decide which SSH protocol version to support.
      */
-    if (ssh_versioncmp(version, cfg.sshprot == 1 ? "2.0" : "1.99") >= 0) {
+
+    /* Anything strictly below "2.0" means protocol 1 is supported. */
+    s->proto1 = ssh_versioncmp(s->version, "2.0") < 0;
+    /* Anything greater or equal to "1.99" means protocol 2 is supported. */
+    s->proto2 = ssh_versioncmp(s->version, "1.99") >= 0;
+
+    if (cfg.sshprot == 0 && !s->proto1) {
+       bombout((ssh,"SSH protocol version 1 required by user but not provided by server"));
+       crReturn(0);
+    }
+    if (cfg.sshprot == 3 && !s->proto2) {
+       bombout((ssh,"SSH protocol version 2 required by user but not provided by server"));
+       crReturn(0);
+    }
+
+    if (s->proto2 && (cfg.sshprot >= 2 || !s->proto1)) {
        /*
-        * This is a v2 server. Begin v2 protocol.
+        * Use v2 protocol.
         */
        char verstring[80], vlog[100];
        sprintf(verstring, "SSH-2.0-%s", sshver);
-       SHA_Init(&exhashbase);
+       SHA_Init(&ssh->exhashbase);
        /*
         * Hash our version string and their version string.
         */
-       sha_string(&exhashbase, verstring, strlen(verstring));
-       sha_string(&exhashbase, vstring, strcspn(vstring, "\r\n"));
+       sha_string(&ssh->exhashbase, verstring, strlen(verstring));
+       sha_string(&ssh->exhashbase, s->vstring, strcspn(s->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;
+       sk_write(ssh->s, verstring, strlen(verstring));
+       ssh->protocol = ssh2_protocol;
+       ssh->version = 2;
+       ssh->s_rdpkt = ssh2_rdpkt;
     } else {
        /*
-        * This is a v1 server. Begin v1 protocol.
+        * Use v1 protocol.
         */
        char verstring[80], vlog[100];
        sprintf(verstring, "SSH-%s-%s",
-               (ssh_versioncmp(version, "1.5") <= 0 ? version : "1.5"),
+               (ssh_versioncmp(s->version, "1.5") <= 0 ? s->version : "1.5"),
                sshver);
        sprintf(vlog, "We claim version: %s", verstring);
        logevent(vlog);
        strcat(verstring, "\n");
+
        logevent("Using SSH protocol version 1");
-       sk_write(s, verstring, strlen(verstring));
-       ssh_protocol = ssh1_protocol;
-       ssh_version = 1;
-       s_rdpkt = ssh1_rdpkt;
+       sk_write(ssh->s, verstring, strlen(verstring));
+       ssh->protocol = ssh1_protocol;
+       ssh->version = 1;
+       ssh->s_rdpkt = ssh1_rdpkt;
     }
-    ssh_state = SSH_STATE_BEFORE_SIZE;
+    ssh->state = SSH_STATE_BEFORE_SIZE;
 
-    sfree(vstring);
+    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
@@ -1566,10 +1961,10 @@ 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)
@@ -1586,9 +1981,12 @@ static void ssh_gotdata(unsigned char *data, int datalen)
        crReturnV;
     while (1) {
        while (datalen > 0) {
-           if (s_rdpkt(&data, &datalen) == 0) {
-               ssh_protocol(NULL, 0, 1);
-               if (ssh_state == SSH_STATE_CLOSED) {
+           if (ssh->s_rdpkt(ssh, &data, &datalen) == 0) {
+               if (ssh->state == SSH_STATE_CLOSED) {
+                   return;
+               }
+               ssh->protocol(ssh, NULL, 0, 1);
+               if (ssh->state == SSH_STATE_CLOSED) {
                    return;
                }
            }
@@ -1601,14 +1999,16 @@ static void ssh_gotdata(unsigned char *data, int datalen)
 static int ssh_closing(Plug plug, 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;
+    ssh->state = SSH_STATE_CLOSED;
+    if (ssh->s) {
+        sk_close(ssh->s);
+        ssh->s = NULL;
     }
     if (error_msg) {
        /* A socket error has occurred. */
-       connection_fatal(error_msg);
+       logevent(error_msg);
+       connection_fatal(ssh->frontend, error_msg);
     } else {
        /* Otherwise, the remote side closed the connection normally. */
     }
@@ -1617,11 +2017,12 @@ static int ssh_closing(Plug plug, char *error_msg, int error_code,
 
 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, data, len);
+    if (ssh->state == SSH_STATE_CLOSED) {
+       if (ssh->s) {
+           sk_close(ssh->s);
+           ssh->s = NULL;
        }
        return 0;
     }
@@ -1630,12 +2031,13 @@ 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);
 }
 
 /*
@@ -1644,65 +2046,50 @@ 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)
+static char *connect_to_host(Ssh ssh, char *host, int port,
+                            char **realhost, int nodelay)
 {
-    static struct plug_function_table fn_table = {
+    static const struct plug_function_table fn_table = {
        ssh_closing,
        ssh_receive,
        ssh_sent,
        NULL
-    }, *fn_table_ptr = &fn_table;
+    };
 
     SockAddr addr;
     char *err;
-#ifdef FWHACK
-    char *FWhost;
-    int FWport;
-#endif
 
-    savedhost = smalloc(1 + strlen(host));
-    if (!savedhost)
+    ssh->savedhost = smalloc(1 + strlen(host));
+    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.
      */
+    logeventf(ssh, "Looking up host \"%s\"", host);
     addr = sk_namelookup(host, realhost);
     if ((err = sk_addr_error(addr)))
        return err;
 
-#ifdef FWHACK
-    *realhost = strdup(FWhost);
-#endif
-
     /*
      * Open socket.
      */
-    s = sk_new(addr, port, 0, 1, &fn_table_ptr);
-    if ((err = sk_socket_error(s)))
-       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));
+       char addrbuf[100];
+       sk_getaddr(addr, addrbuf, 100);
+       logeventf(ssh, "Connecting to %s port %d", addrbuf, port);
+    }
+    ssh->fn = &fn_table;
+    ssh->s = new_connection(addr, *realhost, port, 0, 1, nodelay, (Plug) ssh);
+    if ((err = sk_socket_error(ssh->s))) {
+       ssh->s = NULL;
+       return err;
     }
-#endif
 
     return NULL;
 }
@@ -1710,15 +2097,15 @@ static char *connect_to_host(char *host, int port, char **realhost)
 /*
  * 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);
     }
 }
 
@@ -1726,18 +2113,18 @@ 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:
            /*
@@ -1758,38 +2145,123 @@ static void ssh_throttle_all(int enable, int bufsize)
 }
 
 /*
+ * Username and password input, abstracted off into routines
+ * reusable in several places - even between SSH1 and SSH2.
+ */
+
+/* Set up a username or password input loop on a given buffer. */
+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;
+}
+
+/*
+ * Process some terminal data in the course of username/password
+ * input. Returns >0 for success (line of input returned in
+ * 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(Ssh ssh, unsigned char *in, int inlen)
+{
+    char c;
+
+    while (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;
+           return +1;
+           break;
+         case 8:
+         case 127:
+           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(ssh, "\b \b");
+               ssh->userpass_input_bufpos--;
+           }
+           break;
+         case 3:
+         case 4:
+           return -1;
+           break;
+         default:
+           if (((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(ssh, &c, 1);
+           }
+           break;
+       }
+    }
+    return 0;
+}
+
+/*
  * 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, int ispkt)
 {
     int i, j;
-    static int len;
-    static unsigned char *rsabuf, *keystr1, *keystr2;
     unsigned char cookie[8];
     struct RSAKey servkey, hostkey;
     struct MD5Context md5c;
-    static unsigned long supported_ciphers_mask, supported_auths_mask;
-    static int tried_publickey;
-    static unsigned char session_id[16];
-    static int cipher_type;
-    static char username[100];
-
-    crBegin;
+    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 (!ispkt)
        crWaitUntil(ispkt);
 
-    if (pktin.type != SSH1_SMSG_PUBLIC_KEY) {
-       bombout(("Public key packet not received"));
+    if (ssh->pktin.type != SSH1_SMSG_PUBLIC_KEY) {
+       bombout((ssh,"Public key packet not received"));
        crReturn(0);
     }
 
     logevent("Received public keys");
 
-    memcpy(cookie, pktin.body, 8);
+    memcpy(cookie, ssh->pktin.body, 8);
 
-    i = makekey(pktin.body + 8, &servkey, &keystr1, 0);
-    j = makekey(pktin.body + 8 + i, &hostkey, &keystr2, 0);
+    i = makekey(ssh->pktin.body + 8, &servkey, &s->keystr1, 0);
+    j = makekey(ssh->pktin.body + 8 + i, &hostkey, &s->keystr2, 0);
 
     /*
      * Log the host key fingerprint.
@@ -1804,27 +2276,27 @@ 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 = GET_32BIT(ssh->pktin.body + 8 + i + j);
+    s->supported_ciphers_mask = GET_32BIT(ssh->pktin.body + 12 + i + j);
+    s->supported_auths_mask = GET_32BIT(ssh->pktin.body + 16 + i + j);
 
-    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, ssh->pktin.body, 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);
+    s->len = (hostkey.bytes > servkey.bytes ? hostkey.bytes : servkey.bytes);
 
-    rsabuf = smalloc(len);
-    if (!rsabuf)
+    s->rsabuf = smalloc(s->len);
+    if (!s->rsabuf)
        fatalbox("Out of memory");
 
     /*
@@ -1841,23 +2313,24 @@ static int do_ssh1_login(unsigned char *in, int inlen, int ispkt)
            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);
+       rsaencrypt(s->rsabuf, 32, &servkey);
+       rsaencrypt(s->rsabuf, servkey.bytes, &hostkey);
     } else {
-       rsaencrypt(rsabuf, 32, &hostkey);
-       rsaencrypt(rsabuf, hostkey.bytes, &servkey);
+       rsaencrypt(s->rsabuf, 32, &hostkey);
+       rsaencrypt(s->rsabuf, hostkey.bytes, &servkey);
     }
 
     logevent("Encrypted session key");
@@ -1865,6 +2338,7 @@ 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];
            if (next_cipher == CIPHER_WARN) {
@@ -1875,33 +2349,33 @@ 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)
-               bombout(("Server violates SSH 1 protocol by not "
+           if ((s->supported_ciphers_mask & (1 << SSH_CIPHER_3DES)) == 0)
+               bombout((ssh,"Server violates SSH 1 protocol by not "
                         "supporting 3DES encryption"));
            else
                /* shouldn't happen */
-               bombout(("No supported ciphers found"));
+               bombout((ssh,"No supported ciphers found"));
            crReturn(0);
        }
 
        /* Warn about chosen cipher if necessary. */
        if (warn)
-           askcipher(cipher_string, 0);
+           askcipher(ssh->frontend, cipher_string, 0);
     }
 
-    switch (cipher_type) {
+    switch (s->cipher_type) {
       case SSH_CIPHER_3DES:
        logevent("Using 3DES encryption");
        break;
@@ -1913,25 +2387,31 @@ 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 (pktin.type != SSH1_SMSG_SUCCESS) {
-       bombout(("Encryption not successfully enabled"));
+    if (ssh->pktin.type != SSH1_SMSG_SUCCESS) {
+       bombout((ssh,"Encryption not successfully enabled"));
        crReturn(0);
     }
 
@@ -1939,172 +2419,143 @@ static int do_ssh1_login(unsigned char *in, int inlen, int ispkt)
 
     fflush(stdout);
     {
-       static int pos = 0;
-       static char c;
        if ((flags & FLAG_INTERACTIVE) && !*cfg.username) {
-           if (ssh_get_line) {
+           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;
+                   ssh->state = SSH_STATE_CLOSED;
                    crReturn(1);
                }
            } else {
-               c_write_str("login as: ");
-               ssh_send_ok = 1;
-               while (pos >= 0) {
+               int ret;               /* need not be kept over crReturn */
+               c_write_str(ssh, "login as: ");
+               ssh->send_ok = 1;
+
+               setup_userpass_input(ssh, s->username, sizeof(s->username), 1);
+               do {
                    crWaitUntil(!ispkt);
-                   while (inlen--)
-                       switch (c = *in++) {
-                         case 10:
-                         case 13:
-                           username[pos] = 0;
-                           pos = -1;
-                           break;
-                         case 8:
-                         case 127:
-                           if (pos > 0) {
-                               c_write_str("\b \b");
-                               pos--;
-                           }
-                           break;
-                         case 21:
-                         case 27:
-                           while (pos > 0) {
-                               c_write_str("\b \b");
-                               pos--;
-                           }
-                           break;
-                         case 3:
-                         case 4:
-                           random_save_seed();
-                           exit(0);
-                           break;
-                         default:
-                           if (((c >= ' ' && c <= '~') ||
-                                ((unsigned char) c >= 160))
-                               && pos < sizeof(username)-1) {
-                               username[pos++] = c;
-                               c_write(&c, 1);
-                           }
-                           break;
-                       }
-               }
-               c_write_str("\r\n");
-               username[strcspn(username, "\n\r")] = '\0';
+                   ret = process_userpass_input(ssh, in, inlen);
+               } while (ret == 0);
+               if (ret < 0)
+                   cleanup_exit(0);
+               c_write_str(ssh, "\r\n");
            }
        } else {
-           strncpy(username, cfg.username, 99);
-           username[99] = '\0';
+           strncpy(s->username, 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);
 
-    tried_publickey = 0;
-
-    while (pktin.type == SSH1_SMSG_FAILURE) {
-       static char password[100];
-       static char prompt[200];
-       static int pos;
-       static char c;
-       static int pwpkt_type;
-       /*
-        * Show password prompt, having first obtained it via a TIS
-        * or CryptoCard exchange if we're doing TIS or CryptoCard
-        * authentication.
-        */
-       pwpkt_type = SSH1_CMSG_AUTH_PASSWORD;
-       if (agent_exists()) {
+    if ((ssh->remote_bugs & BUG_CHOKES_ON_RSA)) {
+       /* We must not attempt PK auth. Pretend we've already tried it. */
+       s->tried_publickey = s->tried_agent = 1;
+    } else {
+       s->tried_publickey = s->tried_agent = 0;
+    }
+    s->tis_auth_refused = s->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,
+                           &s->publickey_blob, &s->publickey_bloblen))
+           s->publickey_blob = NULL;
+    } else
+       s->publickey_blob = NULL;
+
+    while (ssh->pktin.type == SSH1_SMSG_FAILURE) {
+       s->pwpkt_type = SSH1_CMSG_AUTH_PASSWORD;
+
+       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;
 
+           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;
+           agent_query(s->request, 5, &r, &s->responselen);
+           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);
                    }
-                   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);
+                   if (s->publickey_blob &&
+                       !memcmp(s->p, s->publickey_blob,
+                               s->publickey_bloblen)) {
+                       logevent("This key matches configured key file");
+                       s->tried_publickey = 1;
+                   }
+                   s->p += 4;
+                   s->p += ssh1_read_bignum(s->p, &s->key.exponent);
+                   s->p += ssh1_read_bignum(s->p, &s->key.modulus);
+                   s->commentlen = GET_32BIT(s->p);
+                   s->p += 4;
+                   s->commentp = s->p;
+                   s->p += s->commentlen;
+                   send_packet(ssh, SSH1_CMSG_AUTH_RSA,
+                               PKT_BIGNUM, s->key.modulus, PKT_END);
                    crWaitUntil(ispkt);
-                   if (pktin.type != SSH1_SMSG_AUTH_RSA_CHALLENGE) {
+                   if (ssh->pktin.type != SSH1_SMSG_AUTH_RSA_CHALLENGE) {
                        logevent("Key refused");
                        continue;
                    }
                    logevent("Received RSA challenge");
-                   ssh1_read_bignum(pktin.body, &challenge);
+                   ssh1_read_bignum(ssh->pktin.body, &s->challenge);
                    {
                        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);
                        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);
@@ -2113,21 +2564,22 @@ static int do_ssh1_login(unsigned char *in, int inlen, int ispkt)
                        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) {
+                               if (ssh->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");
@@ -2140,204 +2592,217 @@ 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;
                }
            }
-           if (authed)
+           if (s->authed)
                break;
        }
-       if (*cfg.keyfile && !tried_publickey)
-           pwpkt_type = SSH1_CMSG_AUTH_RSA;
+       if (*cfg.keyfile && !s->tried_publickey)
+           s->pwpkt_type = SSH1_CMSG_AUTH_RSA;
 
-       if (pktin.type == SSH1_SMSG_FAILURE &&
-           cfg.try_tis_auth &&
-           (supported_auths_mask & (1 << SSH1_AUTH_TIS))) {
-           pwpkt_type = SSH1_CMSG_AUTH_TIS_RESPONSE;
+       if (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);
+           send_packet(ssh, SSH1_CMSG_AUTH_TIS, PKT_END);
            crWaitUntil(ispkt);
-           if (pktin.type != SSH1_SMSG_AUTH_TIS_CHALLENGE) {
+           if (ssh->pktin.type != SSH1_SMSG_AUTH_TIS_CHALLENGE) {
                logevent("TIS authentication declined");
                if (flags & FLAG_INTERACTIVE)
-                   c_write_str("TIS authentication refused.\r\n");
+                   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]));
+               int challengelen = GET_32BIT(ssh->pktin.body);
                logevent("Received TIS challenge");
-               if (challengelen > sizeof(prompt) - 1)
-                   challengelen = sizeof(prompt) - 1;  /* prevent overrun */
-               memcpy(prompt, pktin.body + 4, challengelen);
-               prompt[challengelen] = '\0';
+               if (challengelen > sizeof(s->prompt) - 1)
+                   challengelen = sizeof(s->prompt) - 1;/* prevent overrun */
+               memcpy(s->prompt, ssh->pktin.body + 4, challengelen);
+               /* Prompt heuristic comes from OpenSSH */
+               strncpy(s->prompt + challengelen,
+                       memchr(s->prompt, '\n', challengelen) ?
+                       "": "\r\nResponse: ",
+                       (sizeof s->prompt) - challengelen);
+               s->prompt[(sizeof s->prompt) - 1] = '\0';
            }
        }
-       if (pktin.type == SSH1_SMSG_FAILURE &&
-           cfg.try_tis_auth &&
-           (supported_auths_mask & (1 << SSH1_AUTH_CCARD))) {
-           pwpkt_type = SSH1_CMSG_AUTH_CCARD_RESPONSE;
+       if (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);
+           send_packet(ssh, SSH1_CMSG_AUTH_CCARD, PKT_END);
            crWaitUntil(ispkt);
-           if (pktin.type != SSH1_SMSG_AUTH_CCARD_CHALLENGE) {
+           if (ssh->pktin.type != SSH1_SMSG_AUTH_CCARD_CHALLENGE) {
                logevent("CryptoCard authentication declined");
-               c_write_str("CryptoCard authentication refused.\r\n");
+               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]));
+               int challengelen = GET_32BIT(ssh->pktin.body);
                logevent("Received CryptoCard challenge");
-               if (challengelen > sizeof(prompt) - 1)
-                   challengelen = sizeof(prompt) - 1;  /* prevent overrun */
-               memcpy(prompt, pktin.body + 4, challengelen);
-               strncpy(prompt + challengelen, "\r\nResponse : ",
-                       sizeof(prompt) - challengelen);
-               prompt[sizeof(prompt) - 1] = '\0';
+               if (challengelen > sizeof(s->prompt) - 1)
+                   challengelen = sizeof(s->prompt) - 1;/* prevent overrun */
+               memcpy(s->prompt, ssh->pktin.body + 4, challengelen);
+               strncpy(s->prompt + challengelen,
+                       memchr(s->prompt, '\n', challengelen) ?
+                       "" : "\r\nResponse: ",
+                       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");
+               c_write_str(ssh, "Trying public key authentication.\r\n");
+           logeventf(ssh, "Trying public key \"%s\"", cfg.keyfile);
+           type = key_type(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(ssh, msgbuf);
+               c_write_str(ssh, "\r\n");
+               s->tried_publickey = 1;
+               continue;
+           }
            if (!rsakey_encrypted(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);
        }
 
+       /*
+        * Show password prompt, having first obtained it via a TIS
+        * or CryptoCard exchange if we're doing TIS or CryptoCard
+        * 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);
-               connection_fatal("Unable to authenticate");
-               ssh_state = SSH_STATE_CLOSED;
+               logevent("Unable to authenticate");
+               connection_fatal(ssh->frontend, "Unable to authenticate");
+               ssh->state = SSH_STATE_CLOSED;
                crReturn(1);
            }
        } else {
-           c_write_str(prompt);
-           pos = 0;
-           ssh_send_ok = 1;
-           while (pos >= 0) {
+           /* Prompt may have come from server. We've munged it a bit, so
+            * we know it to be zero-terminated at least once. */
+           int ret;                   /* need not be saved over crReturn */
+           c_write_untrusted(ssh, s->prompt, strlen(s->prompt));
+           s->pos = 0;
+
+           setup_userpass_input(ssh, s->password, sizeof(s->password), 0);
+           do {
                crWaitUntil(!ispkt);
-               while (inlen--)
-                   switch (c = *in++) {
-                     case 10:
-                     case 13:
-                       password[pos] = 0;
-                       pos = -1;
-                       break;
-                     case 8:
-                     case 127:
-                       if (pos > 0)
-                           pos--;
-                       break;
-                     case 21:
-                     case 27:
-                       pos = 0;
-                       break;
-                     case 3:
-                     case 4:
-                       random_save_seed();
-                       exit(0);
-                       break;
-                     default:
-                       if (pos < sizeof(password)-1)
-                           password[pos++] = c;
-                       break;
-                   }
-           }
-           c_write_str("\r\n");
+               ret = process_userpass_input(ssh, in, inlen);
+           } while (ret == 0);
+           if (ret < 0)
+               cleanup_exit(0);
+           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 public 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;
+           
+           {
+               int ret = loadrsakey(cfg.keyfile, &s->key, s->password);
+               if (ret == 0) {
+                   c_write_str(ssh, "Couldn't load private key from ");
+                   c_write_str(ssh, cfg.keyfile);
+                   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");
+           if (ssh->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) {
-               bombout(("Bizarre response to offer of public key"));
+           if (ssh->pktin.type != SSH1_SMSG_AUTH_RSA_CHALLENGE) {
+               bombout((ssh,"Bizarre response to offer of public key"));
                crReturn(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;
+
+               ssh1_read_bignum(ssh->pktin.body, &challenge);
+               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);
+
+               freebn(challenge);
+               freebn(response);
+           }
 
            crWaitUntil(ispkt);
-           if (pktin.type == SSH1_SMSG_FAILURE) {
+           if (ssh->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"));
+           } else if (ssh->pktin.type != SSH1_SMSG_SUCCESS) {
+               bombout((ssh,"Bizarre response to RSA authentication response"));
                crReturn(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
@@ -2370,30 +2835,21 @@ static int do_ssh1_login(unsigned char *in, int inlen, int ispkt)
                 * use of the fact that the password is interpreted
                 * as a C string: so we can append a NUL, then some
                 * random data.
+                * 
+                * One server (a Cisco one) can deal with neither
+                * SSH1_MSG_IGNORE _nor_ a padded password string.
+                * For this server we are left with no defences
+                * against password length sniffing.
                 */
-               if (ssh_remote_bugs & BUG_CHOKES_ON_SSH1_IGNORE) {
-                   char string[64];
-                   char *s;
-                   int len;
-
-                   len = strlen(password);
-                   if (len < sizeof(string)) {
-                       s = string;
-                       strcpy(string, password);
-                       len++;         /* cover the zero byte */
-                       while (len < sizeof(string)) {
-                           string[len++] = (char) random_byte();
-                       }
-                   } else {
-                       s = password;
-                   }
-                   send_packet(pwpkt_type, PKT_INT, len,
-                               PKT_DATA, s, len, PKT_END);
-               } else {
+               if (!(ssh->remote_bugs & BUG_CHOKES_ON_SSH1_IGNORE)) {
+                   /*
+                    * The server can deal with SSH1_MSG_IGNORE, so
+                    * we can use the primary defence.
+                    */
                    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;
@@ -2408,8 +2864,8 @@ static int do_ssh1_login(unsigned char *in, int inlen, int ispkt)
 
                    for (i = bottom; i <= top; i++) {
                        if (i == pwlen)
-                           defer_packet(pwpkt_type, PKT_STR, password,
-                                        PKT_END);
+                           defer_packet(ssh, s->pwpkt_type,
+                                        PKT_STR, s->password, PKT_END);
                        else {
                            for (j = 0; j < i; j++) {
                                do {
@@ -2417,29 +2873,63 @@ static int do_ssh1_login(unsigned char *in, int inlen, int ispkt)
                                } while (randomstr[j] == '\0');
                            }
                            randomstr[i] = '\0';
-                           defer_packet(SSH1_MSG_IGNORE,
+                           defer_packet(ssh, SSH1_MSG_IGNORE,
                                         PKT_STR, randomstr, PKT_END);
                        }
                    }
-                   ssh_pkt_defersend();
+                   logevent("Sending password with camouflage packets");
+                   ssh_pkt_defersend(ssh);
+               } 
+               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 *ss;
+                   int len;
+
+                   len = strlen(s->password);
+                   if (len < sizeof(string)) {
+                       ss = string;
+                       strcpy(string, s->password);
+                       len++;         /* cover the zero byte */
+                       while (len < sizeof(string)) {
+                           string[len++] = (char) random_byte();
+                       }
+                   } else {
+                       ss = s->password;
+                   }
+                   logevent("Sending length-padded password");
+                   send_packet(ssh, s->pwpkt_type, PKT_INT, len,
+                               PKT_DATA, ss, len, PKT_END);
+               } else {
+                   /*
+                    * The server has _both_
+                    * BUG_CHOKES_ON_SSH1_IGNORE and
+                    * BUG_NEEDS_SSH1_PLAIN_PASSWORD. There is
+                    * therefore nothing we can do.
+                    */
+                   int len;
+                   len = strlen(s->password);
+                   logevent("Sending unpadded password");
+                   send_packet(ssh, s->pwpkt_type, PKT_INT, len,
+                               PKT_DATA, s->password, len, PKT_END);
                }
            } else {
-               send_packet(pwpkt_type, PKT_STR, password, PKT_END);
+               send_packet(ssh, s->pwpkt_type, PKT_STR, s->password, PKT_END);
            }
        }
        logevent("Sent password");
-       memset(password, 0, strlen(password));
+       memset(s->password, 0, strlen(s->password));
        crWaitUntil(ispkt);
-       if (pktin.type == SSH1_SMSG_FAILURE) {
+       if (ssh->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));
+       } else if (ssh->pktin.type != SSH1_SMSG_SUCCESS) {
+           bombout((ssh,"Strange packet received, type %d", ssh->pktin.type));
            crReturn(0);
        }
     }
@@ -2451,20 +2941,32 @@ static int do_ssh1_login(unsigned char *in, int inlen, int ispkt)
 
 void sshfwd_close(struct ssh_channel *c)
 {
+    Ssh ssh = c->ssh;
+
     if (c && !c->closes) {
-       if (ssh_version == 1) {
-           send_packet(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();
+       /*
+        * If the channel's remoteid is -1, we have sent
+        * CHANNEL_OPEN for this channel, but it hasn't even been
+        * acknowledged by the server. So we must set a close flag
+        * on it now, and then when the server acks the channel
+        * open, we can close it then.
+        */
+       if (((int)c->remoteid) != -1) {
+           if (ssh->version == 1) {
+               send_packet(ssh, SSH1_MSG_CHANNEL_CLOSE, PKT_INT, c->remoteid,
+                           PKT_END);
+           } else {
+               ssh2_pkt_init(ssh, SSH2_MSG_CHANNEL_CLOSE);
+               ssh2_pkt_adduint32(ssh, c->remoteid);
+               ssh2_pkt_send(ssh);
+           }
        }
-       c->closes = 1;
+       c->closes = 1;                 /* sent MSG_CLOSE */
        if (c->type == CHAN_X11) {
            c->u.x11.s = NULL;
            logevent("Forwarded X11 connection terminated");
-       } else if (c->type == CHAN_SOCKDATA) {
+       } else if (c->type == CHAN_SOCKDATA ||
+                  c->type == CHAN_SOCKDATA_DORMANT) {
            c->u.pfd.s = NULL;
            logevent("Forwarded port closed");
        }
@@ -2473,8 +2975,10 @@ 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->version == 1) {
+       send_packet(ssh, SSH1_MSG_CHANNEL_DATA,
                    PKT_INT, c->remoteid,
                    PKT_INT, len, PKT_DATA, buf, len, PKT_END);
        /*
@@ -2493,130 +2997,169 @@ 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->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 ssh1_protocol(Ssh ssh, unsigned char *in, int inlen, int ispkt)
 {
-    crBegin;
+    crBegin(ssh->ssh1_protocol_crstate);
 
     random_init();
 
-    while (!do_ssh1_login(in, inlen, ispkt)) {
+    while (!do_ssh1_login(ssh, in, inlen, ispkt)) {
        crReturnV;
     }
-    if (ssh_state == SSH_STATE_CLOSED)
+    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);
+       send_packet(ssh, 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"));
+       if (ssh->pktin.type != SSH1_SMSG_SUCCESS
+           && ssh->pktin.type != SSH1_SMSG_FAILURE) {
+           bombout((ssh,"Protocol confusion"));
            crReturnV;
-       } else if (pktin.type == SSH1_SMSG_FAILURE) {
+       } else if (ssh->pktin.type == SSH1_SMSG_FAILURE) {
            logevent("Agent forwarding refused");
        } else {
            logevent("Agent forwarding enabled");
-           ssh_agentfwd_enabled = TRUE;
+           ssh->agentfwd_enabled = TRUE;
        }
     }
 
     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,
+       ssh->x11auth = x11_invent_auth(proto, sizeof(proto),
+                                      data, sizeof(data));
+       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, 0, PKT_END);
        } else {
-           send_packet(SSH1_CMSG_X11_REQUEST_FORWARDING,
+           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) {
-           bombout(("Protocol confusion"));
+       if (ssh->pktin.type != SSH1_SMSG_SUCCESS
+           && ssh->pktin.type != SSH1_SMSG_FAILURE) {
+           bombout((ssh,"Protocol confusion"));
            crReturnV;
-       } else if (pktin.type == SSH1_SMSG_FAILURE) {
+       } else if (ssh->pktin.type == SSH1_SMSG_FAILURE) {
            logevent("X11 forwarding refused");
        } else {
            logevent("X11 forwarding enabled");
-           ssh_X11_fwd_enabled = TRUE;
+           ssh->X11_fwd_enabled = TRUE;
        }
     }
 
     {
-       char type, *e;
+       char type;
        int n;
-       int sport,dport;
+       int sport,dport,sserv,dserv;
        char sports[256], dports[256], host[256];
-       char buf[1024];
 
-       ssh_rportfwds = newtree234(ssh_rportcmp_ssh1);
+       ssh->rportfwds = newtree234(ssh_rportcmp_ssh1);
         /* Add port forwardings. */
-       e = cfg.portfwd;
-       while (*e) {
-           type = *e++;
+       ssh->portfwd_strptr = cfg.portfwd;
+       while (*ssh->portfwd_strptr) {
+           type = *ssh->portfwd_strptr++;
            n = 0;
-           while (*e && *e != '\t')
-               sports[n++] = *e++;
+           while (*ssh->portfwd_strptr && *ssh->portfwd_strptr != '\t')
+               sports[n++] = *ssh->portfwd_strptr++;
            sports[n] = 0;
-           if (*e == '\t')
-               e++;
+           if (*ssh->portfwd_strptr == '\t')
+               ssh->portfwd_strptr++;
            n = 0;
-           while (*e && *e != ':')
-               host[n++] = *e++;
+           while (*ssh->portfwd_strptr && *ssh->portfwd_strptr != ':')
+               host[n++] = *ssh->portfwd_strptr++;
            host[n] = 0;
-           if (*e == ':')
-               e++;
+           if (*ssh->portfwd_strptr == ':')
+               ssh->portfwd_strptr++;
            n = 0;
-           while (*e)
-               dports[n++] = *e++;
+           while (*ssh->portfwd_strptr)
+               dports[n++] = *ssh->portfwd_strptr++;
            dports[n] = 0;
-           e++;
+           ssh->portfwd_strptr++;
            dport = atoi(dports);
+           dserv = 0;
+           if (dport == 0) {
+               dserv = 1;
+               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;
+               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 %d forwarding to %s:%d",
-                           sport, host, dport);
-                   logevent(buf);
+                   pfd_addforward(host, dport, sport, ssh);
+                   logeventf(ssh, "Local port %.*s%.*s%d%.*s forwarding to"
+                             " %s:%.*s%.*s%d%.*s",
+                             (int)(sserv ? strlen(sports) : 0), sports,
+                             sserv, "(", sport, sserv, ")",
+                             host,
+                             (int)(dserv ? strlen(dports) : 0), dports,
+                             dserv, "(", dport, dserv, ")");
                } 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);
+                   if (add234(ssh->rportfwds, pf) != pf) {
+                       logeventf(ssh, 
+                                 "Duplicate remote port forwarding to %s:%d",
+                                 host, dport);
                        sfree(pf);
                    } else {
-                       sprintf(buf, "Requesting remote port %d forward to %s:%d",
-                               sport, host, dport);
-                       logevent(buf);
-                       send_packet(SSH1_CMSG_PORT_FORWARD_REQUEST,
+                       logeventf(ssh, "Requesting remote port %.*s%.*s%d%.*s"
+                                 " forward to %s:%.*s%.*s%d%.*s",
+                                 (int)(sserv ? strlen(sports) : 0), sports,
+                                 sserv, "(", sport, sserv, ")",
+                                 host,
+                                 (int)(dserv ? strlen(dports) : 0), dports,
+                                 dserv, "(", dport, dserv, ")");
+                       send_packet(ssh, SSH1_CMSG_PORT_FORWARD_REQUEST,
                                    PKT_INT, sport,
                                    PKT_STR, host,
                                    PKT_INT, dport,
                                    PKT_END);
+                       do {
+                           crReturnV;
+                       } while (!ispkt);
+                       if (ssh->pktin.type != SSH1_SMSG_SUCCESS
+                           && ssh->pktin.type != SSH1_SMSG_FAILURE) {
+                           bombout((ssh,"Protocol confusion"));
+                           crReturnV;
+                       } else if (ssh->pktin.type == SSH1_SMSG_FAILURE) {
+                           c_write_str(ssh, "Server refused port"
+                                       " forwarding\r\n");
+                       }
+                       logevent("Remote port forwarding enabled");
                    }
                }
            }
@@ -2624,136 +3167,158 @@ static void ssh1_protocol(unsigned char *in, int inlen, int ispkt)
     }
 
     if (!cfg.nopty) {
-       send_packet(SSH1_CMSG_REQUEST_PTY,
+       send_packet(ssh, SSH1_CMSG_REQUEST_PTY,
                    PKT_STR, cfg.termtype,
-                   PKT_INT, rows, PKT_INT, cols,
+                   PKT_INT, ssh->term_height,
+                   PKT_INT, ssh->term_width,
                    PKT_INT, 0, PKT_INT, 0, PKT_CHAR, 0, PKT_END);
-       ssh_state = SSH_STATE_INTERMED;
+       ssh->state = SSH_STATE_INTERMED;
        do {
            crReturnV;
        } while (!ispkt);
-       if (pktin.type != SSH1_SMSG_SUCCESS
-           && pktin.type != SSH1_SMSG_FAILURE) {
-           bombout(("Protocol confusion"));
+       if (ssh->pktin.type != SSH1_SMSG_SUCCESS
+           && ssh->pktin.type != SSH1_SMSG_FAILURE) {
+           bombout((ssh,"Protocol confusion"));
            crReturnV;
-       } else if (pktin.type == SSH1_SMSG_FAILURE) {
-           c_write_str("Server refused to allocate pty\r\n");
-           ssh_editing = ssh_echoing = 1;
+       } else if (ssh->pktin.type == SSH1_SMSG_FAILURE) {
+           c_write_str(ssh, "Server refused to allocate pty\r\n");
+           ssh->editing = ssh->echoing = 1;
        }
        logevent("Allocated pty");
     } 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);
+       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) {
-           bombout(("Protocol confusion"));
+       if (ssh->pktin.type != SSH1_SMSG_SUCCESS
+           && ssh->pktin.type != SSH1_SMSG_FAILURE) {
+           bombout((ssh,"Protocol confusion"));
            crReturnV;
-       } else if (pktin.type == SSH1_SMSG_FAILURE) {
-           c_write_str("Server refused to compress\r\n");
+       } else if (ssh->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");
     }
 
-    if (*cfg.remote_cmd_ptr)
-       send_packet(SSH1_CMSG_EXEC_CMD, PKT_STR, cfg.remote_cmd_ptr,
-                   PKT_END);
-    else
-       send_packet(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);
-
-    ldisc_send(NULL, 0);              /* cause ldisc to notice changes */
-    ssh_send_ok = 1;
-    ssh_channels = newtree234(ssh_channelcmp);
+    /*
+     * Start the shell or command.
+     * 
+     * Special case: if the first-choice command is an SSH2
+     * subsystem (hence not usable here) and the second choice
+     * exists, we fall straight back to that.
+     */
+    {
+       char *cmd = cfg.remote_cmd_ptr;
+       
+       if (cfg.ssh_subsys && cfg.remote_cmd_ptr2) {
+           cmd = cfg.remote_cmd_ptr2;
+           ssh->fallback_cmd = TRUE;
+       }
+       if (*cmd)
+           send_packet(ssh, SSH1_CMSG_EXEC_CMD, PKT_STR, cmd, PKT_END);
+       else
+           send_packet(ssh, SSH1_CMSG_EXEC_SHELL, PKT_END);
+       logevent("Started session");
+    }
+
+    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);
+
+    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);
+           if (ssh->pktin.type == SSH1_SMSG_STDOUT_DATA ||
+               ssh->pktin.type == SSH1_SMSG_STDERR_DATA) {
+               long len = GET_32BIT(ssh->pktin.body);
                int bufsize =
-                   from_backend(pktin.type == SSH1_SMSG_STDERR_DATA,
-                                pktin.body + 4, len);
-               if (bufsize > SSH1_BUFFER_LIMIT) {
-                   ssh1_stdout_throttling = 1;
-                   ssh1_throttle(+1);
+                   from_backend(ssh->frontend,
+                                ssh->pktin.type == SSH1_SMSG_STDERR_DATA,
+                                ssh->pktin.body + 4, len);
+               if (!ssh->v1_stdout_throttling && bufsize > SSH1_BUFFER_LIMIT) {
+                   ssh->v1_stdout_throttling = 1;
+                   ssh1_throttle(ssh, +1);
                }
-           } else if (pktin.type == SSH1_MSG_DISCONNECT) {
-               ssh_state = SSH_STATE_CLOSED;
+           } else if (ssh->pktin.type == SSH1_MSG_DISCONNECT) {
+               ssh->state = SSH_STATE_CLOSED;
                logevent("Received disconnect request");
                crReturnV;
-           } else if (pktin.type == SSH1_SMSG_X11_OPEN) {
+           } else if (ssh->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);
+               if (!ssh->X11_fwd_enabled) {
+                   send_packet(ssh, SSH1_MSG_CHANNEL_OPEN_FAILURE,
+                               PKT_INT, GET_32BIT(ssh->pktin.body), PKT_END);
                    logevent("Rejected X11 connect request");
                } else {
                    c = smalloc(sizeof(struct ssh_channel));
+                   c->ssh = ssh;
 
-                   if (x11_init(&c->u.x11.s, cfg.x11_display, c) != NULL) {
+                   if (x11_init(&c->u.x11.s, cfg.x11_display, c,
+                                ssh->x11auth) != NULL) {
                        logevent("opening X11 forward connection failed");
                        sfree(c);
-                       send_packet(SSH1_MSG_CHANNEL_OPEN_FAILURE,
-                                   PKT_INT, GET_32BIT(pktin.body),
+                       send_packet(ssh, SSH1_MSG_CHANNEL_OPEN_FAILURE,
+                                   PKT_INT, GET_32BIT(ssh->pktin.body),
                                    PKT_END);
                    } else {
                        logevent
                            ("opening X11 forward connection succeeded");
-                       c->remoteid = GET_32BIT(pktin.body);
-                       c->localid = alloc_channel_id();
+                       c->remoteid = GET_32BIT(ssh->pktin.body);
+                       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(SSH1_MSG_CHANNEL_OPEN_CONFIRMATION,
+                       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");
                    }
                }
-           } else if (pktin.type == SSH1_SMSG_AGENT_OPEN) {
+           } else if (ssh->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);
+               if (!ssh->agentfwd_enabled) {
+                   send_packet(ssh, SSH1_MSG_CHANNEL_OPEN_FAILURE,
+                               PKT_INT, GET_32BIT(ssh->pktin.body), PKT_END);
                } else {
                    c = smalloc(sizeof(struct ssh_channel));
-                   c->remoteid = GET_32BIT(pktin.body);
-                   c->localid = alloc_channel_id();
+                   c->ssh = ssh;
+                   c->remoteid = GET_32BIT(ssh->pktin.body);
+                   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(SSH1_MSG_CHANNEL_OPEN_CONFIRMATION,
+                   add234(ssh->channels, c);
+                   send_packet(ssh, SSH1_MSG_CHANNEL_OPEN_CONFIRMATION,
                                PKT_INT, c->remoteid, PKT_INT, c->localid,
                                PKT_END);
                }
-           } else if (pktin.type == SSH1_MSG_PORT_OPEN) {
+           } else if (ssh->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;
@@ -2762,9 +3327,10 @@ static void ssh1_protocol(unsigned char *in, int inlen, int ispkt)
                char host[256], buf[1024];
                char *p, *h, *e;
                c = smalloc(sizeof(struct ssh_channel));
+               c->ssh = ssh;
 
-               hostsize = GET_32BIT(pktin.body+4);
-               for(h = host, p = pktin.body+8; hostsize != 0; hostsize--) {
+               hostsize = GET_32BIT(ssh->pktin.body+4);
+               for(h = host, p = ssh->pktin.body+8; hostsize != 0; hostsize--) {
                    if (h+1 < host+sizeof(host))
                        *h++ = *p;
                    p++;
@@ -2775,12 +3341,12 @@ static void ssh1_protocol(unsigned char *in, int inlen, int ispkt)
                strcpy(pf.dhost, host);
                pf.dport = port;
 
-               if (find234(ssh_rportfwds, &pf, NULL) == NULL) {
+               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);
+                    send_packet(ssh, SSH1_MSG_CHANNEL_OPEN_FAILURE,
+                                PKT_INT, GET_32BIT(ssh->pktin.body), PKT_END);
                } else {
                    sprintf(buf, "Received remote port open request for %s:%d",
                            host, port);
@@ -2791,48 +3357,70 @@ static void ssh1_protocol(unsigned char *in, int inlen, int ispkt)
                        sprintf(buf, "Port open failed: %s", e);
                        logevent(buf);
                        sfree(c);
-                       send_packet(SSH1_MSG_CHANNEL_OPEN_FAILURE,
-                                   PKT_INT, GET_32BIT(pktin.body),
+                       send_packet(ssh, SSH1_MSG_CHANNEL_OPEN_FAILURE,
+                                   PKT_INT, GET_32BIT(ssh->pktin.body),
                                    PKT_END);
                    } else {
-                       c->remoteid = GET_32BIT(pktin.body);
-                       c->localid = alloc_channel_id();
+                       c->remoteid = GET_32BIT(ssh->pktin.body);
+                       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(SSH1_MSG_CHANNEL_OPEN_CONFIRMATION,
+                       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");
                    }
                }
 
-           } else if (pktin.type == SSH1_MSG_CHANNEL_OPEN_CONFIRMATION) {
-               unsigned int remoteid = GET_32BIT(pktin.body);
-               unsigned int localid = GET_32BIT(pktin.body+4);
+           } else if (ssh->pktin.type == SSH1_MSG_CHANNEL_OPEN_CONFIRMATION) {
+               unsigned int remoteid = GET_32BIT(ssh->pktin.body);
+               unsigned int localid = GET_32BIT(ssh->pktin.body+4);
                struct ssh_channel *c;
 
-               c = find234(ssh_channels, &remoteid, ssh_channelfind);
+               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);
                }
 
-           } else if (pktin.type == SSH1_MSG_CHANNEL_CLOSE ||
-                      pktin.type == SSH1_MSG_CHANNEL_CLOSE_CONFIRMATION) {
+               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);
+               }
+
+           } else if (ssh->pktin.type == SSH1_MSG_CHANNEL_OPEN_FAILURE) {
+               unsigned int remoteid = GET_32BIT(ssh->pktin.body);
+               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);
+               }
+
+           } else if (ssh->pktin.type == SSH1_MSG_CHANNEL_CLOSE ||
+                      ssh->pktin.type == SSH1_MSG_CHANNEL_CLOSE_CONFIRMATION) {
                /* Remote side closes a channel. */
-               unsigned i = GET_32BIT(pktin.body);
+               unsigned i = GET_32BIT(ssh->pktin.body);
                struct ssh_channel *c;
-               c = find234(ssh_channels, &i, ssh_channelfind);
-               if (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 & closetype))
-                       send_packet(pktin.type, PKT_INT, c->remoteid,
-                                   PKT_END);
+                       (ssh->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);
@@ -2845,19 +3433,31 @@ static void ssh1_protocol(unsigned char *in, int inlen, int ispkt)
                        pfd_close(c->u.pfd.s);
                        c->u.pfd.s = NULL;
                    }
-                   c->closes |= closetype;
-                   if (c->closes == 3) {
-                       del234(ssh_channels, c);
+
+                   c->closes |= (closetype << 2);   /* seen this message */
+                   if (!(c->closes & closetype)) {
+                       send_packet(ssh, 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((ssh,"Received CHANNEL_CLOSE%s for %s channel %d\n",
+                            ssh->pktin.type == SSH1_MSG_CHANNEL_CLOSE ? "" :
+                            "_CONFIRMATION", c ? "half-open" : "nonexistent",
+                            i));
                }
-           } else if (pktin.type == SSH1_MSG_CHANNEL_DATA) {
+           } else if (ssh->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;
+               int i = GET_32BIT(ssh->pktin.body);
+               int len = GET_32BIT(ssh->pktin.body + 4);
+               unsigned char *p = ssh->pktin.body + 8;
                struct ssh_channel *c;
-               c = find234(ssh_channels, &i, ssh_channelfind);
+               c = find234(ssh->channels, &i, ssh_channelfind);
                if (c) {
                    int bufsize;
                    switch (c->type) {
@@ -2907,7 +3507,7 @@ static void ssh1_protocol(unsigned char *in, int inlen, int ispkt)
                                    sentreply = "\0\0\0\1\5";
                                    replylen = 5;
                                }
-                               send_packet(SSH1_MSG_CHANNEL_DATA,
+                               send_packet(ssh, SSH1_MSG_CHANNEL_DATA,
                                            PKT_INT, c->remoteid,
                                            PKT_INT, replylen,
                                            PKT_DATA, sentreply, replylen,
@@ -2921,26 +3521,40 @@ static void ssh1_protocol(unsigned char *in, int inlen, int ispkt)
                        bufsize = 0;   /* agent channels never back up */
                        break;
                    }
-                   if (bufsize > SSH1_BUFFER_LIMIT) {
+                   if (!c->v.v1.throttling && bufsize > SSH1_BUFFER_LIMIT) {
                        c->v.v1.throttling = 1;
-                       ssh1_throttle(+1);
+                       ssh1_throttle(ssh, +1);
                    }
                }
-           } else if (pktin.type == SSH1_SMSG_SUCCESS) {
+           } else if (ssh->pktin.type == SSH1_SMSG_SUCCESS) {
                /* may be from EXEC_SHELL on some servers */
-           } else if (pktin.type == SSH1_SMSG_FAILURE) {
+           } else if (ssh->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) {
-               send_packet(SSH1_CMSG_EXIT_CONFIRMATION, PKT_END);
+           } else if (ssh->pktin.type == SSH1_SMSG_EXIT_STATUS) {
+               char buf[100];
+               ssh->exitcode = GET_32BIT(ssh->pktin.body);
+               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->state = SSH_STATE_CLOSED;
+                crReturnV;
            } else {
-               bombout(("Strange packet received: type %d", pktin.type));
+               bombout((ssh,"Strange packet received: type %d", ssh->pktin.type));
                crReturnV;
            }
        } else {
            while (inlen > 0) {
                int len = min(inlen, 512);
-               send_packet(SSH1_CMSG_STDIN_DATA,
+               send_packet(ssh, SSH1_CMSG_STDIN_DATA,
                            PKT_INT, len, PKT_DATA, in, len, PKT_END);
                in += len;
                inlen -= len;
@@ -2956,7 +3570,10 @@ static void ssh1_protocol(unsigned char *in, int inlen, int ispkt)
  */
 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?
@@ -2982,20 +3599,22 @@ 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,
+static void ssh2_mkkey(Ssh ssh, Bignum K, char *H, char *sessid, char chr,
                       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);
@@ -3004,63 +3623,70 @@ 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 do_ssh2_transport(Ssh ssh, 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 first_kex;
-
-    crBegin;
+    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_ciphers;
+       const struct ssh2_ciphers *preferred_ciphers[CIPHER_MAX];
+       const struct ssh_compress *preferred_comp;
+       int first_kex;
+    };
+    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;
+
     random_init();
-    first_kex = 1;
+    s->first_kex = 1;
 
-    /*
-     * Set up the preferred ciphers. (NULL => warn below here)
-     */
-    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:
-           /* Not supported in SSH2; silently drop */
-           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++;
+    {
+       int i;
+       /*
+        * Set up the preferred ciphers. (NULL => warn below here)
+        */
+       s->n_preferred_ciphers = 0;
+       for (i = 0; i < CIPHER_MAX; i++) {
+           switch (cfg.ssh_cipherlist[i]) {
+             case CIPHER_BLOWFISH:
+               s->preferred_ciphers[s->n_preferred_ciphers++] = &ssh2_blowfish;
+               break;
+             case CIPHER_DES:
+               if (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;
        }
     }
 
@@ -3068,212 +3694,244 @@ static int do_ssh2_transport(unsigned char *in, int inlen, int ispkt)
      * Set up preferred compression.
      */
     if (cfg.compression)
-       preferred_comp = &ssh_zlib;
+       s->preferred_comp = &ssh_zlib;
     else
-       preferred_comp = &ssh_comp_none;
+       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);
+    if (ssh->remote_bugs & BUG_SSH2_HMAC)
+       s->maclist = buggymacs, s->nmacs = lenof(buggymacs);
     else
-       maclist = macs, nmacs = lenof(macs);
+       s->maclist = macs, s->nmacs = lenof(macs);
 
   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();
-    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++) {
-           ssh2_pkt_addstring_str(c->list[j]->name);
-           if (i < n_preferred_ciphers || j < c->nciphers - 1)
-               ssh2_pkt_addstring_str(",");
+    {
+       int i, j, cipherstr_started;
+
+       /*
+        * Construct and send our key exchange packet.
+        */
+       ssh2_pkt_init(ssh, SSH2_MSG_KEXINIT);
+       for (i = 0; i < 16; i++)
+           ssh2_pkt_addbyte(ssh, (unsigned char) random_byte());
+       /* List key exchange algorithms. */
+       ssh2_pkt_addstring_start(ssh);
+       for (i = 0; i < lenof(kex_algs); i++) {
+           if (kex_algs[i] == &ssh_diffiehellman_gex &&
+               (ssh->remote_bugs & BUG_SSH2_DH_GEX))
+               continue;
+           ssh2_pkt_addstring_str(ssh, kex_algs[i]->name);
+           if (i < lenof(kex_algs) - 1)
+               ssh2_pkt_addstring_str(ssh, ",");
        }
-    }
-    /* List server->client encryption algorithms. */
-    ssh2_pkt_addstring_start();
-    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++) {
-           ssh2_pkt_addstring_str(c->list[j]->name);
-           if (i < n_preferred_ciphers || j < c->nciphers - 1)
-               ssh2_pkt_addstring_str(",");
+       /* List server host key algorithms. */
+       ssh2_pkt_addstring_start(ssh);
+       for (i = 0; i < lenof(hostkey_algs); i++) {
+           ssh2_pkt_addstring_str(ssh, hostkey_algs[i]->name);
+           if (i < lenof(hostkey_algs) - 1)
+               ssh2_pkt_addstring_str(ssh, ",");
        }
+       /* List client->server encryption algorithms. */
+       ssh2_pkt_addstring_start(ssh);
+       cipherstr_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 (cipherstr_started)
+                   ssh2_pkt_addstring_str(ssh, ",");
+               ssh2_pkt_addstring_str(ssh, c->list[j]->name);
+               cipherstr_started = 1;
+           }
+       }
+       /* List server->client encryption algorithms. */
+       ssh2_pkt_addstring_start(ssh);
+       cipherstr_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 (cipherstr_started)
+                   ssh2_pkt_addstring_str(ssh, ",");
+               ssh2_pkt_addstring_str(ssh, c->list[j]->name);
+               cipherstr_started = 1;
+           }
+       }
+       /* List client->server MAC algorithms. */
+       ssh2_pkt_addstring_start(ssh);
+       for (i = 0; i < s->nmacs; i++) {
+           ssh2_pkt_addstring_str(ssh, s->maclist[i]->name);
+           if (i < s->nmacs - 1)
+               ssh2_pkt_addstring_str(ssh, ",");
+       }
+       /* List server->client MAC algorithms. */
+       ssh2_pkt_addstring_start(ssh);
+       for (i = 0; i < s->nmacs; i++) {
+           ssh2_pkt_addstring_str(ssh, s->maclist[i]->name);
+           if (i < s->nmacs - 1)
+               ssh2_pkt_addstring_str(ssh, ",");
+       }
+       /* List client->server compression algorithms. */
+       ssh2_pkt_addstring_start(ssh);
+       for (i = 0; i < lenof(compressions) + 1; i++) {
+           const struct ssh_compress *c =
+               i == 0 ? s->preferred_comp : compressions[i - 1];
+           ssh2_pkt_addstring_str(ssh, c->name);
+           if (i < lenof(compressions))
+               ssh2_pkt_addstring_str(ssh, ",");
+       }
+       /* List server->client compression algorithms. */
+       ssh2_pkt_addstring_start(ssh);
+       for (i = 0; i < lenof(compressions) + 1; i++) {
+           const struct ssh_compress *c =
+               i == 0 ? s->preferred_comp : compressions[i - 1];
+           ssh2_pkt_addstring_str(ssh, c->name);
+           if (i < lenof(compressions))
+               ssh2_pkt_addstring_str(ssh, ",");
+       }
+       /* List client->server languages. Empty list. */
+       ssh2_pkt_addstring_start(ssh);
+       /* List server->client languages. Empty list. */
+       ssh2_pkt_addstring_start(ssh);
+       /* First KEX packet does _not_ follow, because we're not that brave. */
+       ssh2_pkt_addbool(ssh, FALSE);
+       /* Reserved. */
+       ssh2_pkt_adduint32(ssh, 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);
+    ssh->exhash = ssh->exhashbase;
+    sha_string(&ssh->exhash, ssh->pktout.data + 5, ssh->pktout.length - 5);
 
-    ssh2_pkt_send();
+    ssh2_pkt_send(ssh);
 
     if (!ispkt)
        crWaitUntil(ispkt);
-    sha_string(&exhash, pktin.data + 5, pktin.length - 5);
+    if (ssh->pktin.length > 5)
+       sha_string(&ssh->exhash, ssh->pktin.data + 5, ssh->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 (ssh->pktin.type != SSH2_MSG_KEXINIT) {
+           bombout((ssh,"expected key exchange packet from server"));
+           crReturn(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;
+       ssh->pktin.savedpos += 16;              /* skip garbage cookie */
+       ssh2_pkt_getstring(ssh, &str, &len);    /* key exchange algorithms */
+       for (i = 0; i < lenof(kex_algs); i++) {
+           if (kex_algs[i] == &ssh_diffiehellman_gex &&
+               (ssh->remote_bugs & BUG_SSH2_DH_GEX))
+               continue;
+           if (in_commasep_string(kex_algs[i]->name, str, len)) {
+               ssh->kex = kex_algs[i];
+               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;
+       ssh2_pkt_getstring(ssh, &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;
+           }
+       }
+       ssh2_pkt_getstring(ssh, &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)
+                   askcipher(ssh->frontend, s->cscipher_tobe->name, 1);
+               break;
+           }
        }
-       if (cscipher_tobe) {
-           if (warn)
-               askcipher(cscipher_tobe->name, 1);
-           break;
+       if (!s->cscipher_tobe) {
+           bombout((ssh,"Couldn't agree a client-to-server cipher (available: %s)",
+                    str ? str : "(null)"));
+           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;
+
+       ssh2_pkt_getstring(ssh, &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)
+                   askcipher(ssh->frontend, s->sccipher_tobe->name, 2);
+               break;
+           }
        }
-       if (sccipher_tobe) {
-           if (warn)
-               askcipher(sccipher_tobe->name, 2);
-           break;
+       if (!s->sccipher_tobe) {
+           bombout((ssh,"Couldn't agree a server-to-client cipher (available: %s)",
+                    str ? str : "(null)"));
+           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;
+
+       ssh2_pkt_getstring(ssh, &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;
+       ssh2_pkt_getstring(ssh, &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;
+       ssh2_pkt_getstring(ssh, &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;
+       ssh2_pkt_getstring(ssh, &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;
+           }
        }
     }
 
@@ -3285,97 +3943,91 @@ 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 == &ssh_diffiehellman_gex) {
        logevent("Doing Diffie-Hellman group exchange");
+       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);
+       ssh2_pkt_init(ssh, SSH2_MSG_KEX_DH_GEX_REQUEST);
+       ssh2_pkt_adduint32(ssh, s->pbits);
+       ssh2_pkt_send(ssh);
 
        crWaitUntil(ispkt);
-       if (pktin.type != SSH2_MSG_KEX_DH_GEX_GROUP) {
-           bombout(("expected key exchange group packet from server"));
+       if (ssh->pktin.type != SSH2_MSG_KEX_DH_GEX_GROUP) {
+           bombout((ssh,"expected key exchange group packet from server"));
            crReturn(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(ssh);
+       s->g = ssh2_pkt_getmp(ssh);
+       ssh->kex_ctx = dh_setup_group(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 {
-       dh_setup_group1();
-       kex_init_value = SSH2_MSG_KEXDH_INIT;
-       kex_reply_value = SSH2_MSG_KEXDH_REPLY;
+       ssh->pkt_ctx |= SSH2_PKTCTX_DHGROUP1;
+       ssh->kex_ctx = dh_setup_group1();
+       s->kex_init_value = SSH2_MSG_KEXDH_INIT;
+       s->kex_reply_value = SSH2_MSG_KEXDH_REPLY;
     }
 
     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);
+    ssh2_pkt_init(ssh, s->kex_init_value);
+    ssh2_pkt_addmp(ssh, s->e);
+    ssh2_pkt_send(ssh);
 
     crWaitUntil(ispkt);
-    if (pktin.type != kex_reply_value) {
-       bombout(("expected key exchange reply packet from server"));
+    if (ssh->pktin.type != s->kex_reply_value) {
+       bombout((ssh,"expected key exchange reply packet from server"));
        crReturn(0);
     }
-    ssh2_pkt_getstring(&hostkeydata, &hostkeylen);
-    f = ssh2_pkt_getmp();
-    ssh2_pkt_getstring(&sigdata, &siglen);
+    ssh2_pkt_getstring(ssh, &s->hostkeydata, &s->hostkeylen);
+    s->f = ssh2_pkt_getmp(ssh);
+    ssh2_pkt_getstring(ssh, &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);
 
 #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)) {
-       bombout(("Server's host key did not match the signature supplied"));
-       crReturn(0);
-    }
-
-    /*
-     * Expect SSH2_MSG_NEWKEYS from server.
-     */
-    crWaitUntil(ispkt);
-    if (pktin.type != SSH2_MSG_NEWKEYS) {
-       bombout(("expected new-keys packet from server"));
+    s->hkey = ssh->hostkey->newkey(s->hostkeydata, s->hostkeylen);
+    if (!s->hkey ||
+       !ssh->hostkey->verifysig(s->hkey, s->sigdata, s->siglen,
+                                s->exchange_hash, 20)) {
+       bombout((ssh,"Server's host key did not match the signature supplied"));
        crReturn(0);
     }
 
@@ -3383,53 +4035,99 @@ static int do_ssh2_transport(unsigned char *in, int inlen, int ispkt)
      * 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);
+    verify_ssh_host_key(ssh->frontend,
+                       ssh->savedhost, ssh->savedport, ssh->hostkey->keytype,
+                       s->keystr, s->fingerprint);
+    if (s->first_kex) {                       /* don't bother logging this in rekeys */
        logevent("Host key fingerprint is:");
-       logevent(fingerprint);
+       logevent(s->fingerprint);
     }
-    sfree(fingerprint);
-    sfree(keystr);
-    hostkey->freekey(hkey);
+    sfree(s->fingerprint);
+    sfree(s->keystr);
+    ssh->hostkey->freekey(s->hkey);
 
     /*
      * Send SSH2_MSG_NEWKEYS.
      */
-    ssh2_pkt_init(SSH2_MSG_NEWKEYS);
-    ssh2_pkt_send();
+    ssh2_pkt_init(ssh, SSH2_MSG_NEWKEYS);
+    ssh2_pkt_send(ssh);
+
+    /*
+     * Expect SSH2_MSG_NEWKEYS from server.
+     */
+    crWaitUntil(ispkt);
+    if (ssh->pktin.type != SSH2_MSG_NEWKEYS) {
+       bombout((ssh,"expected new-keys packet from server"));
+       crReturn(0);
+    }
 
     /*
      * Create and initialise session keys.
      */
-    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->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->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->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->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->cs_comp_ctx)
+       ssh->cscomp->compress_cleanup(ssh->cs_comp_ctx);
+    ssh->cscomp = s->cscomp_tobe;
+    ssh->cs_comp_ctx = ssh->cscomp->compress_init();
+
+    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 after keys. Here we use the exchange hash from the
      * _first_ key exchange.
      */
-    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);
+    {
+       unsigned char keyspace[40];
+       if (s->first_kex)
+           memcpy(ssh->v2_session_id, s->exchange_hash,
+                  sizeof(s->exchange_hash));
+       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,'D',keyspace);
+       ssh->sccipher->setkey(ssh->sc_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,'B',keyspace);
+       ssh->sccipher->setiv(ssh->sc_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);
+       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 client->server encryption",
+             ssh->cscipher->text_name);
+    logeventf(ssh, "Initialised %.200s server->client encryption",
+             ssh->sccipher->text_name);
+    if (ssh->cscomp->text_name)
+       logeventf(ssh, "Initialised %s compression",
+                 ssh->cscomp->text_name);
+    if (ssh->sccomp->text_name)
+       logeventf(ssh, "Initialised %s decompression",
+                 ssh->sccomp->text_name);
 
     /*
      * If this is the first key exchange phase, we must pass the
@@ -3439,10 +4137,10 @@ 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) {
+    if (!s->first_kex) {
        crReturn(0);
     }
-    first_kex = 0;
+    s->first_kex = 0;
 
     /*
      * Now we're encrypting. Begin returning 1 to the protocol main
@@ -3450,7 +4148,7 @@ static int do_ssh2_transport(unsigned char *in, int inlen, int ispkt)
      * transport. If we ever see a KEXINIT, we must go back to the
      * start.
      */
-    while (!(ispkt && pktin.type == SSH2_MSG_KEXINIT)) {
+    while (!(ispkt && ssh->pktin.type == SSH2_MSG_KEXINIT)) {
        crReturn(1);
     }
     logevent("Server initiated key re-exchange");
@@ -3473,6 +4171,8 @@ 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;
+
     while (c->v.v2.remwindow > 0 && bufchain_size(&c->v.v2.outbuffer) > 0) {
        int len;
        void *data;
@@ -3481,11 +4181,11 @@ 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();
+       ssh2_pkt_init(ssh, SSH2_MSG_CHANNEL_DATA);
+       ssh2_pkt_adduint32(ssh, c->remoteid);
+       ssh2_pkt_addstring_start(ssh);
+       ssh2_pkt_addstring_data(ssh, data, len);
+       ssh2_pkt_send(ssh);
        bufchain_consume(&c->v.v2.outbuffer, len);
        c->v.v2.remwindow -= len;
     }
@@ -3502,11 +4202,21 @@ 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
+     * be sending any more data anyway.
+     */
+    if (c->closes != 0)
+       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();
+       ssh2_pkt_init(ssh, SSH2_MSG_CHANNEL_WINDOW_ADJUST);
+       ssh2_pkt_adduint32(ssh, c->remoteid);
+       ssh2_pkt_adduint32(ssh, newwin - c->v.v2.locwindow);
+       ssh2_pkt_send(ssh);
        c->v.v2.locwindow = newwin;
     }
 }
@@ -3514,52 +4224,67 @@ static void ssh2_set_window(struct ssh_channel *c, unsigned newwin)
 /*
  * Handle the SSH2 userauth and connection layers.
  */
-static void do_ssh2_authconn(unsigned char *in, int inlen, int ispkt)
+static void do_ssh2_authconn(Ssh ssh, 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, echo;
-    static char username[100];
-    static char pwprompt[200];
-    static char password[100];
-
-    crBegin;
+    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, tried_keyb_inter;
+       int kbd_inter_running;
+       int we_are_in;
+       int num_prompts, curr_prompt, echo;
+       char username[100];
+       int got_username;
+       char pwprompt[200];
+       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;
+    };
+    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();
+    ssh2_pkt_init(ssh, SSH2_MSG_SERVICE_REQUEST);
+    ssh2_pkt_addstring(ssh, "ssh-userauth");
+    ssh2_pkt_send(ssh);
     crWaitUntilV(ispkt);
-    if (pktin.type != SSH2_MSG_SERVICE_ACCEPT) {
-       bombout(("Server refused user authentication protocol"));
+    if (ssh->pktin.type != SSH2_MSG_SERVICE_ACCEPT) {
+       bombout((ssh,"Server refused user authentication protocol"));
        crReturnV;
     }
 
     /*
      * 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
      * 
@@ -3577,106 +4302,108 @@ 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!
      */
+    s->username[0] = '\0';
+    s->got_username = FALSE;
     do {
-       static int pos;
-       static char c;
-
        /*
         * Get a username.
         */
-       pos = 0;
-       if ((flags & FLAG_INTERACTIVE) && !*cfg.username) {
-           if (ssh_get_line) {
+       if (s->got_username && !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) {
+           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;
+                   ssh->state = SSH_STATE_CLOSED;
                    crReturnV;
                }
            } else {
-               c_write_str("login as: ");
-               ssh_send_ok = 1;
-               while (pos >= 0) {
+               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);
-                   while (inlen--)
-                       switch (c = *in++) {
-                         case 10:
-                         case 13:
-                           username[pos] = 0;
-                           pos = -1;
-                           break;
-                         case 8:
-                         case 127:
-                           if (pos > 0) {
-                               c_write_str("\b \b");
-                               pos--;
-                           }
-                           break;
-                         case 21:
-                         case 27:
-                           while (pos > 0) {
-                               c_write_str("\b \b");
-                               pos--;
-                           }
-                           break;
-                         case 3:
-                         case 4:
-                           random_save_seed();
-                           exit(0);
-                           break;
-                         default:
-                           if (((c >= ' ' && c <= '~') ||
-                                ((unsigned char) c >= 160))
-                               && pos < sizeof(username)-1) {
-                               username[pos++] = c;
-                               c_write(&c, 1);
-                           }
-                           break;
-                       }
-               }
+                   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, 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);
            }
        }
+       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.
         */
-       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;
+       ssh->pkt_ctx &= ~SSH2_PKTCTX_AUTH_MASK;
+
+       ssh2_pkt_init(ssh, SSH2_MSG_USERAUTH_REQUEST);
+       ssh2_pkt_addstring(ssh, s->username);
+       ssh2_pkt_addstring(ssh, "ssh-connection");/* service requested */
+       ssh2_pkt_addstring(ssh, "none");    /* method */
+       ssh2_pkt_send(ssh);
+       s->type = AUTH_TYPE_NONE;
+       s->gotit = FALSE;
+       s->we_are_in = FALSE;
+
+       s->tried_pubkey_config = FALSE;
+       s->tried_agent = FALSE;
+       s->tried_keyb_inter = FALSE;
+       s->kbd_inter_running = FALSE;
+       /* Load the pub half of cfg.keyfile so we notice if it's in Pageant */
+       if (*cfg.keyfile) {
+           int keytype;
+           logeventf(ssh->frontend,
+                     "Reading private key file \"%.150s\"", cfg.keyfile);
+           keytype = key_type(cfg.keyfile);
+           if (keytype == SSH_KEYTYPE_SSH2) {
+               s->publickey_blob =
+                   ssh2_userkey_loadpub(cfg.keyfile, NULL,
+                                        &s->publickey_bloblen);
+           } else {
+               char *msgbuf;
+               logeventf(ssh->frontend,
+                         "Unable to use this key file (%s)",
+                         key_type_to_str(keytype));
+               msgbuf = dupprintf("Unable to use key file \"%.150s\""
+                                  " (%s)\r\n", cfg.keyfile,
+                                  key_type_to_str(keytype));
+               c_write_str(ssh, msgbuf);
+               sfree(msgbuf);
+               s->publickey_blob = NULL;
+           }
+       } else
+           s->publickey_blob = NULL;
 
        while (1) {
            /*
             * Wait for the result of the last authentication request.
             */
-           if (!gotit)
+           if (!s->gotit)
                crWaitUntilV(ispkt);
-           while (pktin.type == SSH2_MSG_USERAUTH_BANNER) {
+           while (ssh->pktin.type == SSH2_MSG_USERAUTH_BANNER) {
                char *banner;
                int size;
                /*
@@ -3688,43 +4415,48 @@ 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);
+                   ssh2_pkt_getstring(ssh, &banner, &size);
                    if (banner)
-                       c_write_untrusted(banner, size);
+                       c_write_untrusted(ssh, banner, size);
                }
                crWaitUntilV(ispkt);
            }
-           if (pktin.type == SSH2_MSG_USERAUTH_SUCCESS) {
+           if (ssh->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 &&
+               ssh->pktin.type == SSH2_MSG_USERAUTH_INFO_REQUEST) {
                /*
-                * This is a further prompt in keyboard-interactive
-                * authentication. Do nothing.
+                * This is either a further set-of-prompts packet
+                * in keyboard-interactive authentication, or it's
+                * the same one and we came back here with `gotit'
+                * set. In the former case, we must reset the
+                * curr_prompt variable.
                 */
-           } else if (pktin.type != SSH2_MSG_USERAUTH_FAILURE) {
-               bombout(("Strange packet received during authentication: type %d",
-                        pktin.type));
+               if (!s->gotit)
+                   s->curr_prompt = 0;
+           } else if (ssh->pktin.type != SSH2_MSG_USERAUTH_FAILURE) {
+               bombout((ssh,"Strange packet received during authentication: type %d",
+                        ssh->pktin.type));
                crReturnV;
            }
 
-           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 (ssh->pktin.type == SSH2_MSG_USERAUTH_FAILURE) {
                char *methods;
                int methlen;
-               ssh2_pkt_getstring(&methods, &methlen);
-               kbd_inter_running = FALSE;
-               if (!ssh2_pkt_getbool()) {
+               ssh2_pkt_getstring(ssh, &methods, &methlen);
+               s->kbd_inter_running = FALSE;
+               if (!ssh2_pkt_getbool(ssh)) {
                    /*
                     * We have received an unequivocal Access
                     * Denied. This can translate to a variety of
@@ -3746,237 +4478,199 @@ static void do_ssh2_authconn(unsigned char *in, int inlen, int ispkt)
                     * whole loop so as to go back to the username
                     * prompt.
                     */
-                   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) {
+                           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_passwd =
-                   in_commasep_string("password", methods, methlen);
-               can_keyb_inter = 
+               s->can_keyb_inter = cfg.try_ki_auth &&
                    in_commasep_string("keyboard-interactive", methods, methlen);
            }
 
-           method = 0;
-
-           if (!method && can_keyb_inter && !tried_keyb_inter) {
-               method = AUTH_KEYBOARD_INTERACTIVE;
-               type = AUTH_TYPE_KEYBOARD_INTERACTIVE;
-               tried_keyb_inter = TRUE;
-
-               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();
+           s->method = 0;
+           ssh->pkt_ctx &= ~SSH2_PKTCTX_AUTH_MASK;
 
-               crWaitUntilV(ispkt);
-               if (pktin.type != SSH2_MSG_USERAUTH_INFO_REQUEST) {
-                   if (pktin.type == SSH2_MSG_USERAUTH_FAILURE)
-                       gotit = TRUE;
-                   logevent("Keyboard-interactive authentication refused");
-                   type = AUTH_TYPE_KEYBOARD_INTERACTIVE_QUIET;
-                   continue;
-               }
-
-               kbd_inter_running = TRUE;
-           }
-
-           if (kbd_inter_running) {
-               method = AUTH_KEYBOARD_INTERACTIVE;
-               type = AUTH_TYPE_KEYBOARD_INTERACTIVE;
-               tried_keyb_inter = TRUE;
-
-               /* We've got packet with that "interactive" info
-                  dump banners, and set its prompt as ours */
-               {
-                   char *name, *inst, *lang, *prompt;
-                   int name_len, inst_len, lang_len, prompt_len;
-                   ssh2_pkt_getstring(&name, &name_len);
-                   ssh2_pkt_getstring(&inst, &inst_len);
-                   ssh2_pkt_getstring(&lang, &lang_len);
-                   if (name_len > 0)
-                       c_write_untrusted(name, name_len);
-                   if (inst_len > 0)
-                       c_write_untrusted(inst, inst_len);
-                   num_prompts = ssh2_pkt_getuint32();
-
-                   ssh2_pkt_getstring(&prompt, &prompt_len);
-                   strncpy(pwprompt, prompt, sizeof(pwprompt));
-                   need_pw = TRUE;
-
-                   echo = ssh2_pkt_getbool();
-               }
-           }
+           /*
+            * Most password/passphrase prompts will be
+            * non-echoing, so we set this to 0 by default.
+            * Exception is that some keyboard-interactive prompts
+            * can be echoing, in which case we'll set this to 1.
+            */
+           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;
 
-               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;
+               agent_query(s->request, 5, &r, &s->responselen);
+               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;
-                       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();
+                       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");
+                           s->tried_pubkey_config = 1;
+                       }
+                       s->pkblob = 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 = s->p;
+                       s->p += s->commentlen;
+                       ssh2_pkt_init(ssh, SSH2_MSG_USERAUTH_REQUEST);
+                       ssh2_pkt_addstring(ssh, s->username);
+                       ssh2_pkt_addstring(ssh, "ssh-connection");      /* service requested */
+                       ssh2_pkt_addstring(ssh, "publickey");   /* method */
+                       ssh2_pkt_addbool(ssh, FALSE);   /* no signature included */
+                       ssh2_pkt_addstring_start(ssh);
+                       ssh2_pkt_addstring_data(ssh, s->alg, s->alglen);
+                       ssh2_pkt_addstring_start(ssh);
+                       ssh2_pkt_addstring_data(ssh, s->pkblob, s->pklen);
+                       ssh2_pkt_send(ssh);
 
                        crWaitUntilV(ispkt);
-                       if (pktin.type != SSH2_MSG_USERAUTH_PK_OK) {
+                       if (ssh->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;
+                       ssh2_pkt_init(ssh, SSH2_MSG_USERAUTH_REQUEST);
+                       ssh2_pkt_addstring(ssh, s->username);
+                       ssh2_pkt_addstring(ssh, "ssh-connection");      /* service requested */
+                       ssh2_pkt_addstring(ssh, "publickey");   /* method */
+                       ssh2_pkt_addbool(ssh, TRUE);
+                       ssh2_pkt_addstring_start(ssh);
+                       ssh2_pkt_addstring_data(ssh, s->alg, s->alglen);
+                       ssh2_pkt_addstring_start(ssh);
+                       ssh2_pkt_addstring_data(ssh, s->pkblob, s->pklen);
+
+                       s->siglen = ssh->pktout.length - 5 + 4 + 20;
+                       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 = smalloc(4 + s->len);
+                       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;
+                       PUT_32BIT(s->q, 20);
+                       s->q += 4;
+                       memcpy(s->q, ssh->v2_session_id, 20);
+                       s->q += 20;
+                       memcpy(s->q, ssh->pktout.data + 5,
+                              ssh->pktout.length - 5);
+                       s->q += ssh->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);
+                       agent_query(s->agentreq, s->len + 4, &vret, &s->retlen);
+                       s->ret = vret;
+                       sfree(s->agentreq);
+                       if (s->ret) {
+                           if (s->ret[4] == SSH2_AGENT_SIGN_RESPONSE) {
                                logevent("Sending Pageant's response");
-                               ssh2_pkt_addstring_start();
-                               ssh2_pkt_addstring_data(ret + 9,
-                                                       GET_32BIT(ret +
-                                                                 5));
-                               ssh2_pkt_send();
-                               authed = TRUE;
+                               ssh2_add_sigblob(ssh, s->pkblob, s->pklen,
+                                                s->ret + 9,
+                                                GET_32BIT(s->ret + 5));
+                               ssh2_pkt_send(ssh);
+                               s->authed = TRUE;
                                break;
                            } else {
                                logevent
                                    ("Pageant failed to answer challenge");
-                               sfree(ret);
+                               sfree(s->ret);
                            }
                        }
                    }
-                   if (authed)
+                   if (s->authed)
                        continue;
                }
            }
 
-           if (!method && can_pubkey && *cfg.keyfile
-               && !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;
 
                /*
                 * Try the public key supplied in the configuration.
@@ -3987,21 +4681,21 @@ static void do_ssh2_authconn(unsigned char *in, int inlen, int ispkt)
                pub_blob = ssh2_userkey_loadpub(cfg.keyfile, &algorithm,
                                                &pub_blob_len);
                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();
+                   ssh2_pkt_init(ssh, SSH2_MSG_USERAUTH_REQUEST);
+                   ssh2_pkt_addstring(ssh, s->username);
+                   ssh2_pkt_addstring(ssh, "ssh-connection");  /* service requested */
+                   ssh2_pkt_addstring(ssh, "publickey");       /* method */
+                   ssh2_pkt_addbool(ssh, FALSE);       /* no signature included */
+                   ssh2_pkt_addstring(ssh, algorithm);
+                   ssh2_pkt_addstring_start(ssh);
+                   ssh2_pkt_addstring_data(ssh, pub_blob, pub_blob_len);
+                   ssh2_pkt_send(ssh);
                    logevent("Offered public key");     /* FIXME */
 
                    crWaitUntilV(ispkt);
-                   if (pktin.type != SSH2_MSG_USERAUTH_PK_OK) {
-                       gotit = TRUE;
-                       type = AUTH_TYPE_PUBLICKEY_OFFER_LOUD;
+                   if (ssh->pktin.type != SSH2_MSG_USERAUTH_PK_OK) {
+                       s->gotit = TRUE;
+                       s->type = AUTH_TYPE_PUBLICKEY_OFFER_LOUD;
                        continue;      /* key refused; give up on it */
                    }
 
@@ -4011,129 +4705,191 @@ static void do_ssh2_authconn(unsigned char *in, int inlen, int ispkt)
                     * the key.
                     */
                    if (ssh2_userkey_encrypted(cfg.keyfile, &comment)) {
-                       sprintf(pwprompt,
+                       sprintf(s->pwprompt,
                                "Passphrase for key \"%.100s\": ",
                                comment);
-                       need_pw = TRUE;
+                       s->need_pw = TRUE;
                    } else {
-                       need_pw = FALSE;
+                       s->need_pw = FALSE;
                    }
-                   c_write_str("Authenticating with public key \"");
-                   c_write_str(comment);
-                   c_write_str("\"\r\n");
-                   method = AUTH_PUBLICKEY_FILE;
+                   c_write_str(ssh, "Authenticating with public key \"");
+                   c_write_str(ssh, comment);
+                   c_write_str(ssh, "\"\r\n");
+                   s->method = AUTH_PUBLICKEY_FILE;
                }
            }
 
-           if (!method && can_passwd) {
-               method = AUTH_PASSWORD;
-               sprintf(pwprompt, "%.90s@%.90s's password: ", username,
-                       savedhost);
-               need_pw = TRUE;
+           if (!s->method && s->can_keyb_inter && !s->tried_keyb_inter) {
+               s->method = AUTH_KEYBOARD_INTERACTIVE;
+               s->type = AUTH_TYPE_KEYBOARD_INTERACTIVE;
+               s->tried_keyb_inter = TRUE;
+
+               ssh->pkt_ctx &= ~SSH2_PKTCTX_AUTH_MASK;
+               ssh->pkt_ctx |= SSH2_PKTCTX_KBDINTER;
+
+               ssh2_pkt_init(ssh, SSH2_MSG_USERAUTH_REQUEST);
+               ssh2_pkt_addstring(ssh, s->username);
+               ssh2_pkt_addstring(ssh, "ssh-connection");      /* service requested */
+               ssh2_pkt_addstring(ssh, "keyboard-interactive");        /* method */
+               ssh2_pkt_addstring(ssh, ""); /* lang */
+               ssh2_pkt_addstring(ssh, "");
+               ssh2_pkt_send(ssh);
+
+               crWaitUntilV(ispkt);
+               if (ssh->pktin.type != SSH2_MSG_USERAUTH_INFO_REQUEST) {
+                   if (ssh->pktin.type == SSH2_MSG_USERAUTH_FAILURE)
+                       s->gotit = TRUE;
+                   logevent("Keyboard-interactive authentication refused");
+                   s->type = AUTH_TYPE_KEYBOARD_INTERACTIVE_QUIET;
+                   continue;
+               }
+
+               s->kbd_inter_running = TRUE;
+               s->curr_prompt = 0;
            }
 
-           if (need_pw) {
+           if (s->kbd_inter_running) {
+               s->method = AUTH_KEYBOARD_INTERACTIVE;
+               s->type = AUTH_TYPE_KEYBOARD_INTERACTIVE;
+               s->tried_keyb_inter = TRUE;
+
+               ssh->pkt_ctx &= ~SSH2_PKTCTX_AUTH_MASK;
+               ssh->pkt_ctx |= SSH2_PKTCTX_KBDINTER;
+
+               if (s->curr_prompt == 0) {
+                   /*
+                    * We've got a fresh USERAUTH_INFO_REQUEST.
+                    * Display header data, and start going through
+                    * the prompts.
+                    */
+                   char *name, *inst, *lang;
+                   int name_len, inst_len, lang_len;
+
+                   ssh2_pkt_getstring(ssh, &name, &name_len);
+                   ssh2_pkt_getstring(ssh, &inst, &inst_len);
+                   ssh2_pkt_getstring(ssh, &lang, &lang_len);
+                   if (name_len > 0) {
+                       c_write_untrusted(ssh, name, name_len);
+                       c_write_str(ssh, "\r\n");
+                   }
+                   if (inst_len > 0) {
+                       c_write_untrusted(ssh, inst, inst_len);
+                       c_write_str(ssh, "\r\n");
+                   }
+                   s->num_prompts = ssh2_pkt_getuint32(ssh);
+               }
+
+               /*
+                * If there are prompts remaining in the packet,
+                * display one and get a response.
+                */
+               if (s->curr_prompt < s->num_prompts) {
+                   char *prompt;
+                   int prompt_len;
+
+                   ssh2_pkt_getstring(ssh, &prompt, &prompt_len);
+                   if (prompt_len > 0) {
+                       strncpy(s->pwprompt, prompt, sizeof(s->pwprompt));
+                       s->pwprompt[prompt_len < sizeof(s->pwprompt) ?
+                                   prompt_len : sizeof(s->pwprompt)-1] = '\0';
+                   } else {
+                       strcpy(s->pwprompt,
+                              "<server failed to send prompt>: ");
+                   }
+                   s->echo = ssh2_pkt_getbool(ssh);
+                   s->need_pw = TRUE;
+               } else
+                   s->need_pw = FALSE;
+           }
+
+           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 (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();
-                       connection_fatal("Unable to authenticate");
-                       ssh_state = SSH_STATE_CLOSED;
+                       ssh2_pkt_init(ssh, SSH2_MSG_DISCONNECT);
+                       ssh2_pkt_adduint32(ssh,SSH2_DISCONNECT_BY_APPLICATION);
+                       ssh2_pkt_addstring(ssh, "No more passwords available"
+                                          " to try");
+                       ssh2_pkt_addstring(ssh, "en");  /* language tag */
+                       ssh2_pkt_send(ssh);
+                       logevent("Unable to authenticate");
+                       connection_fatal(ssh->frontend,
+                                        "Unable to authenticate");
+                       ssh->state = SSH_STATE_CLOSED;
                        crReturnV;
                    }
                } else {
-                   static int pos = 0;
-                   static char c;
-
-                   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;
 
-                   pos = 0;
-                   while (pos >= 0) {
+                   setup_userpass_input(ssh, s->password,
+                                        sizeof(s->password), s->echo);
+                   do {
                        crWaitUntilV(!ispkt);
-                       while (inlen--)
-                           switch (c = *in++) {
-                             case 10:
-                             case 13:
-                               password[pos] = 0;
-                               pos = -1;
-                               break;
-                             case 8:
-                             case 127:
-                               if (pos > 0)
-                                   pos--;
-                               break;
-                             case 21:
-                             case 27:
-                               pos = 0;
-                               break;
-                             case 3:
-                             case 4:
-                               random_save_seed();
-                               exit(0);
-                               break;
-                             default:
-                               if (pos < sizeof(password)-1)
-                                   password[pos++] = c;
-                               break;
-                           }
-                   }
-                   c_write_str("\r\n");
+                       ret = process_userpass_input(ssh, in, inlen);
+                   } while (ret == 0);
+                   if (ret < 0)
+                       cleanup_exit(0);
+                   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;
 
-               key = ssh2_load_userkey(cfg.keyfile, password);
+               key = ssh2_load_userkey(cfg.keyfile, s->password);
                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\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;
+                   ssh2_pkt_init(ssh, SSH2_MSG_USERAUTH_REQUEST);
+                   ssh2_pkt_addstring(ssh, s->username);
+                   ssh2_pkt_addstring(ssh, "ssh-connection");  /* service requested */
+                   ssh2_pkt_addstring(ssh, "none");    /* method */
+                   ssh2_pkt_send(ssh);
+                   s->type = AUTH_TYPE_NONE;
                } else {
-                   unsigned char *blob, *sigdata;
-                   int blob_len, sigdata_len;
+                   unsigned char *pkblob, *sigblob, *sigdata;
+                   int pkblob_len, sigblob_len, sigdata_len;
 
                    /*
                     * 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);
-                   blob = key->alg->public_blob(key->data, &blob_len);
-                   ssh2_pkt_addstring_start();
-                   ssh2_pkt_addstring_data(blob, blob_len);
-                   sfree(blob);
+                   ssh2_pkt_init(ssh, SSH2_MSG_USERAUTH_REQUEST);
+                   ssh2_pkt_addstring(ssh, s->username);
+                   ssh2_pkt_addstring(ssh, "ssh-connection");  /* service requested */
+                   ssh2_pkt_addstring(ssh, "publickey");       /* method */
+                   ssh2_pkt_addbool(ssh, TRUE);
+                   ssh2_pkt_addstring(ssh, key->alg->name);
+                   pkblob = key->alg->public_blob(key->data, &pkblob_len);
+                   ssh2_pkt_addstring_start(ssh);
+                   ssh2_pkt_addstring_data(ssh, pkblob, pkblob_len);
 
                    /*
                     * The data to be signed is:
@@ -4143,24 +4899,24 @@ 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_len = ssh->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);
-                   blob =
-                       key->alg->sign(key->data, sigdata, sigdata_len,
-                                      &blob_len);
-                   ssh2_pkt_addstring_start();
-                   ssh2_pkt_addstring_data(blob, blob_len);
-                   sfree(blob);
+                   memcpy(sigdata + 4, ssh->v2_session_id, 20);
+                   memcpy(sigdata + 24, ssh->pktout.data + 5,
+                          ssh->pktout.length - 5);
+                   sigblob = key->alg->sign(key->data, sigdata,
+                                            sigdata_len, &sigblob_len);
+                   ssh2_add_sigblob(ssh, pkblob, pkblob_len,
+                                    sigblob, sigblob_len);
+                   sfree(pkblob);
+                   sfree(sigblob);
                    sfree(sigdata);
 
-                   ssh2_pkt_send();
-                   type = AUTH_TYPE_PUBLICKEY;
+                   ssh2_pkt_send(ssh);
+                   s->type = AUTH_TYPE_PUBLICKEY;
                }
-           } 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
@@ -4175,26 +4931,26 @@ 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();
+               ssh2_pkt_init(ssh, SSH2_MSG_USERAUTH_REQUEST);
+               ssh2_pkt_addstring(ssh, s->username);
+               ssh2_pkt_addstring(ssh, "ssh-connection");      /* service requested */
+               ssh2_pkt_addstring(ssh, "password");
+               ssh2_pkt_addbool(ssh, FALSE);
+               ssh2_pkt_addstring(ssh, s->password);
+               ssh2_pkt_defer(ssh);
                /*
                 * 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
@@ -4204,42 +4960,60 @@ 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();
+                   ssh2_pkt_init(ssh, SSH2_MSG_IGNORE);
+                   ssh2_pkt_addstring_start(ssh);
                    for (i = 0; i < stringlen; i++) {
                        char c = (char) random_byte();
-                       ssh2_pkt_addstring_data(&c, 1);
+                       ssh2_pkt_addstring_data(ssh, &c, 1);
                    }
-                   ssh2_pkt_defer();
+                   ssh2_pkt_defer(ssh);
                }
-               ssh_pkt_defersend();
+               ssh_pkt_defersend(ssh);
                logevent("Sent password");
-               type = AUTH_TYPE_PASSWORD;
-           } else if (method == AUTH_KEYBOARD_INTERACTIVE) {
-                ssh2_pkt_init(SSH2_MSG_USERAUTH_INFO_RESPONSE);
-                ssh2_pkt_adduint32(num_prompts);
-                ssh2_pkt_addstring(password);
-                memset(password, 0, sizeof(password));
-                ssh2_pkt_send();
-               type = AUTH_TYPE_KEYBOARD_INTERACTIVE;
+               s->type = AUTH_TYPE_PASSWORD;
+           } else if (s->method == AUTH_KEYBOARD_INTERACTIVE) {
+               if (s->curr_prompt == 0) {
+                   ssh2_pkt_init(ssh, SSH2_MSG_USERAUTH_INFO_RESPONSE);
+                   ssh2_pkt_adduint32(ssh, s->num_prompts);
+               }
+               if (s->need_pw) {      /* only add pw if we just got one! */
+                   ssh2_pkt_addstring(ssh, s->password);
+                   memset(s->password, 0, sizeof(s->password));
+                   s->curr_prompt++;
+               }
+               if (s->curr_prompt >= s->num_prompts) {
+                   ssh2_pkt_send(ssh);
+               } else {
+                   /*
+                    * If there are prompts remaining, we set
+                    * `gotit' so that we won't attempt to get
+                    * another packet. Then we go back round the
+                    * loop and will end up retrieving another
+                    * prompt out of the existing packet. Funky or
+                    * what?
+                    */
+                   s->gotit = TRUE;
+               }
+               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;
+               c_write_str(ssh, "No supported authentication methods"
+                           " left to try!\r\n");
+               logevent("No supported authentications offered."
+                        " Disconnecting");
+               ssh2_pkt_init(ssh, SSH2_MSG_DISCONNECT);
+               ssh2_pkt_adduint32(ssh, SSH2_DISCONNECT_BY_APPLICATION);
+               ssh2_pkt_addstring(ssh, "No supported authentication"
+                                  " methods available");
+               ssh2_pkt_addstring(ssh, "en");  /* language tag */
+               ssh2_pkt_send(ssh);
+               ssh->state = SSH_STATE_CLOSED;
                crReturnV;
            }
        }
-    } while (!we_are_in);
+    } while (!s->we_are_in);
 
     /*
      * Now we're authenticated for the connection protocol. The
@@ -4250,33 +5024,34 @@ static void do_ssh2_authconn(unsigned char *in, int inlen, int ispkt)
     /*
      * So now create a channel with a session in it.
      */
-    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();
+    ssh->channels = newtree234(ssh_channelcmp);
+    ssh->mainchan = smalloc(sizeof(struct ssh_channel));
+    ssh->mainchan->ssh = ssh;
+    ssh->mainchan->localid = alloc_channel_id(ssh);
+    ssh2_pkt_init(ssh, SSH2_MSG_CHANNEL_OPEN);
+    ssh2_pkt_addstring(ssh, "session");
+    ssh2_pkt_adduint32(ssh, ssh->mainchan->localid);
+    ssh->mainchan->v.v2.locwindow = OUR_V2_WINSIZE;
+    ssh2_pkt_adduint32(ssh, ssh->mainchan->v.v2.locwindow);/* our window size */
+    ssh2_pkt_adduint32(ssh, 0x4000UL);      /* our max pkt size */
+    ssh2_pkt_send(ssh);
     crWaitUntilV(ispkt);
-    if (pktin.type != SSH2_MSG_CHANNEL_OPEN_CONFIRMATION) {
-       bombout(("Server refused to open a session"));
+    if (ssh->pktin.type != SSH2_MSG_CHANNEL_OPEN_CONFIRMATION) {
+       bombout((ssh,"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"));
+    if (ssh2_pkt_getuint32(ssh) != ssh->mainchan->localid) {
+       bombout((ssh,"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);
+    ssh->mainchan->remoteid = ssh2_pkt_getuint32(ssh);
+    ssh->mainchan->type = CHAN_MAINSESSION;
+    ssh->mainchan->closes = 0;
+    ssh->mainchan->v.v2.remwindow = ssh2_pkt_getuint32(ssh);
+    ssh->mainchan->v.v2.remmaxpkt = ssh2_pkt_getuint32(ssh);
+    bufchain_init(&ssh->mainchan->v.v2.outbuffer);
+    add234(ssh->channels, ssh->mainchan);
     logevent("Opened channel for session");
 
     /*
@@ -4285,38 +5060,40 @@ static void do_ssh2_authconn(unsigned char *in, int inlen, int ispkt)
     if (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();
+       ssh->x11auth = x11_invent_auth(proto, sizeof(proto),
+                                      data, sizeof(data));
+       ssh2_pkt_init(ssh, SSH2_MSG_CHANNEL_REQUEST);
+       ssh2_pkt_adduint32(ssh, ssh->mainchan->remoteid);
+       ssh2_pkt_addstring(ssh, "x11-req");
+       ssh2_pkt_addbool(ssh, 1);              /* want reply */
+       ssh2_pkt_addbool(ssh, 0);              /* many connections */
+       ssh2_pkt_addstring(ssh, proto);
+       ssh2_pkt_addstring(ssh, data);
+       ssh2_pkt_adduint32(ssh, 0);            /* screen number */
+       ssh2_pkt_send(ssh);
 
        do {
            crWaitUntilV(ispkt);
-           if (pktin.type == SSH2_MSG_CHANNEL_WINDOW_ADJUST) {
-               unsigned i = ssh2_pkt_getuint32();
+           if (ssh->pktin.type == SSH2_MSG_CHANNEL_WINDOW_ADJUST) {
+               unsigned i = ssh2_pkt_getuint32(ssh);
                struct ssh_channel *c;
-               c = find234(ssh_channels, &i, ssh_channelfind);
+               c = find234(ssh->channels, &i, ssh_channelfind);
                if (!c)
                    continue;          /* nonexistent channel */
-               c->v.v2.remwindow += ssh2_pkt_getuint32();
+               c->v.v2.remwindow += ssh2_pkt_getuint32(ssh);
            }
-       } while (pktin.type == SSH2_MSG_CHANNEL_WINDOW_ADJUST);
+       } while (ssh->pktin.type == SSH2_MSG_CHANNEL_WINDOW_ADJUST);
 
-       if (pktin.type != SSH2_MSG_CHANNEL_SUCCESS) {
-           if (pktin.type != SSH2_MSG_CHANNEL_FAILURE) {
-               bombout(("Server got confused by X11 forwarding request"));
+       if (ssh->pktin.type != SSH2_MSG_CHANNEL_SUCCESS) {
+           if (ssh->pktin.type != SSH2_MSG_CHANNEL_FAILURE) {
+               bombout((ssh,"Unexpected response to X11 forwarding request:"
+                        " packet type %d", ssh->pktin.type));
                crReturnV;
            }
            logevent("X11 forwarding refused");
        } else {
            logevent("X11 forwarding enabled");
-           ssh_X11_fwd_enabled = TRUE;
+           ssh->X11_fwd_enabled = TRUE;
        }
     }
 
@@ -4324,81 +5101,108 @@ static void do_ssh2_authconn(unsigned char *in, int inlen, int ispkt)
      * Enable port forwardings.
      */
     {
-       static char *e;                /* preserve across crReturn */
        char type;
        int n;
-       int sport,dport;
+       int sport,dport,sserv,dserv;
        char sports[256], dports[256], host[256];
-       char buf[1024];
 
-       ssh_rportfwds = newtree234(ssh_rportcmp_ssh2);
+       ssh->rportfwds = newtree234(ssh_rportcmp_ssh2);
         /* Add port forwardings. */
-       e = cfg.portfwd;
-       while (*e) {
-           type = *e++;
+       ssh->portfwd_strptr = cfg.portfwd;
+       while (*ssh->portfwd_strptr) {
+           type = *ssh->portfwd_strptr++;
            n = 0;
-           while (*e && *e != '\t')
-               sports[n++] = *e++;
+           while (*ssh->portfwd_strptr && *ssh->portfwd_strptr != '\t')
+               sports[n++] = *ssh->portfwd_strptr++;
            sports[n] = 0;
-           if (*e == '\t')
-               e++;
+           if (*ssh->portfwd_strptr == '\t')
+               ssh->portfwd_strptr++;
            n = 0;
-           while (*e && *e != ':')
-               host[n++] = *e++;
+           while (*ssh->portfwd_strptr && *ssh->portfwd_strptr != ':')
+               host[n++] = *ssh->portfwd_strptr++;
            host[n] = 0;
-           if (*e == ':')
-               e++;
+           if (*ssh->portfwd_strptr == ':')
+               ssh->portfwd_strptr++;
            n = 0;
-           while (*e)
-               dports[n++] = *e++;
+           while (*ssh->portfwd_strptr)
+               dports[n++] = *ssh->portfwd_strptr++;
            dports[n] = 0;
-           e++;
+           ssh->portfwd_strptr++;
            dport = atoi(dports);
+           dserv = 0;
+           if (dport == 0) {
+               dserv = 1;
+               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;
+               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 %d forwarding to %s:%d",
-                           sport, host, dport);
-                   logevent(buf);
+                   pfd_addforward(host, dport, sport, ssh);
+                   logeventf(ssh, "Local port %.*s%.*s%d%.*s forwarding to"
+                             " %s:%.*s%.*s%d%.*s",
+                             (int)(sserv ? strlen(sports) : 0), sports,
+                             sserv, "(", sport, sserv, ")",
+                             host,
+                             (int)(dserv ? strlen(dports) : 0), dports,
+                             dserv, "(", dport, dserv, ")");
                } 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);
+                   if (add234(ssh->rportfwds, pf) != pf) {
+                       logeventf(ssh, "Duplicate remote port forwarding"
+                                 " to %s:%d", host, dport);
                        sfree(pf);
                    } else {
-                       sprintf(buf, "Requesting remote port %d (forwarded to %s:%d)",
-                               sport, host, dport);
-                       logevent(buf);
-                       ssh2_pkt_init(SSH2_MSG_GLOBAL_REQUEST);
-                       ssh2_pkt_addstring("tcpip-forward");
-                       ssh2_pkt_addbool(1);/* want reply */
-                       ssh2_pkt_addstring("127.0.0.1");
-                       ssh2_pkt_adduint32(sport);
-                       ssh2_pkt_send();
+                       logeventf(ssh, "Requesting remote port %.*s%.*s%d%.*s"
+                                 " forward to %s:%.*s%.*s%d%.*s",
+                                 (int)(sserv ? strlen(sports) : 0), sports,
+                                 sserv, "(", sport, sserv, ")",
+                                 host,
+                                 (int)(dserv ? strlen(dports) : 0), dports,
+                                 dserv, "(", dport, dserv, ")");
+                       ssh2_pkt_init(ssh, SSH2_MSG_GLOBAL_REQUEST);
+                       ssh2_pkt_addstring(ssh, "tcpip-forward");
+                       ssh2_pkt_addbool(ssh, 1);/* want reply */
+                       if (cfg.rport_acceptall)
+                           ssh2_pkt_addstring(ssh, "0.0.0.0");
+                       else
+                           ssh2_pkt_addstring(ssh, "127.0.0.1");
+                       ssh2_pkt_adduint32(ssh, sport);
+                       ssh2_pkt_send(ssh);
 
                        do {
                            crWaitUntilV(ispkt);
-                           if (pktin.type == SSH2_MSG_CHANNEL_WINDOW_ADJUST) {
-                               unsigned i = ssh2_pkt_getuint32();
+                           if (ssh->pktin.type == SSH2_MSG_CHANNEL_WINDOW_ADJUST) {
+                               unsigned i = ssh2_pkt_getuint32(ssh);
                                struct ssh_channel *c;
-                               c = find234(ssh_channels, &i, ssh_channelfind);
+                               c = find234(ssh->channels, &i, ssh_channelfind);
                                if (!c)
                                    continue;/* nonexistent channel */
-                               c->v.v2.remwindow += ssh2_pkt_getuint32();
+                               c->v.v2.remwindow += ssh2_pkt_getuint32(ssh);
                            }
-                       } while (pktin.type == SSH2_MSG_CHANNEL_WINDOW_ADJUST);
+                       } while (ssh->pktin.type == SSH2_MSG_CHANNEL_WINDOW_ADJUST);
 
-                       if (pktin.type != SSH2_MSG_REQUEST_SUCCESS) {
-                           if (pktin.type != SSH2_MSG_REQUEST_FAILURE) {
-                               bombout(("Server got confused by port forwarding request"));
+                       if (ssh->pktin.type != SSH2_MSG_REQUEST_SUCCESS) {
+                           if (ssh->pktin.type != SSH2_MSG_REQUEST_FAILURE) {
+                               bombout((ssh,"Unexpected response to port "
+                                        "forwarding request: packet type %d",
+                                        ssh->pktin.type));
                                crReturnV;
                            }
                            logevent("Server refused this port forwarding");
@@ -4416,34 +5220,34 @@ static void do_ssh2_authconn(unsigned char *in, int inlen, int ispkt)
      */
     if (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();
+       ssh2_pkt_init(ssh, SSH2_MSG_CHANNEL_REQUEST);
+       ssh2_pkt_adduint32(ssh, ssh->mainchan->remoteid);
+       ssh2_pkt_addstring(ssh, "auth-agent-req@openssh.com");
+       ssh2_pkt_addbool(ssh, 1);              /* want reply */
+       ssh2_pkt_send(ssh);
 
        do {
            crWaitUntilV(ispkt);
-           if (pktin.type == SSH2_MSG_CHANNEL_WINDOW_ADJUST) {
-               unsigned i = ssh2_pkt_getuint32();
+           if (ssh->pktin.type == SSH2_MSG_CHANNEL_WINDOW_ADJUST) {
+               unsigned i = ssh2_pkt_getuint32(ssh);
                struct ssh_channel *c;
-               c = find234(ssh_channels, &i, ssh_channelfind);
+               c = find234(ssh->channels, &i, ssh_channelfind);
                if (!c)
                    continue;          /* nonexistent channel */
-               c->v.v2.remwindow += ssh2_pkt_getuint32();
+               c->v.v2.remwindow += ssh2_pkt_getuint32(ssh);
            }
-       } while (pktin.type == SSH2_MSG_CHANNEL_WINDOW_ADJUST);
+       } while (ssh->pktin.type == SSH2_MSG_CHANNEL_WINDOW_ADJUST);
 
-       if (pktin.type != SSH2_MSG_CHANNEL_SUCCESS) {
-           if (pktin.type != SSH2_MSG_CHANNEL_FAILURE) {
-               bombout(
-                       ("Server got confused by agent forwarding request"));
+       if (ssh->pktin.type != SSH2_MSG_CHANNEL_SUCCESS) {
+           if (ssh->pktin.type != SSH2_MSG_CHANNEL_FAILURE) {
+               bombout((ssh,"Unexpected response to agent forwarding request:"
+                        " packet type %d", ssh->pktin.type));
                crReturnV;
            }
            logevent("Agent forwarding refused");
        } else {
            logevent("Agent forwarding enabled");
-           ssh_agentfwd_enabled = TRUE;
+           ssh->agentfwd_enabled = TRUE;
        }
     }
 
@@ -4451,122 +5255,151 @@ static void do_ssh2_authconn(unsigned char *in, int inlen, int ispkt)
      * 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;
+       ssh2_pkt_init(ssh, SSH2_MSG_CHANNEL_REQUEST);
+       ssh2_pkt_adduint32(ssh, ssh->mainchan->remoteid);       /* recipient channel */
+       ssh2_pkt_addstring(ssh, "pty-req");
+       ssh2_pkt_addbool(ssh, 1);              /* want reply */
+       ssh2_pkt_addstring(ssh, cfg.termtype);
+       ssh2_pkt_adduint32(ssh, ssh->term_width);
+       ssh2_pkt_adduint32(ssh, ssh->term_height);
+       ssh2_pkt_adduint32(ssh, 0);            /* pixel width */
+       ssh2_pkt_adduint32(ssh, 0);            /* pixel height */
+       ssh2_pkt_addstring_start(ssh);
+       ssh2_pkt_addstring_data(ssh, "\0", 1);  /* TTY_OP_END, no special options */
+       ssh2_pkt_send(ssh);
+       ssh->state = SSH_STATE_INTERMED;
 
        do {
            crWaitUntilV(ispkt);
-           if (pktin.type == SSH2_MSG_CHANNEL_WINDOW_ADJUST) {
-               unsigned i = ssh2_pkt_getuint32();
+           if (ssh->pktin.type == SSH2_MSG_CHANNEL_WINDOW_ADJUST) {
+               unsigned i = ssh2_pkt_getuint32(ssh);
                struct ssh_channel *c;
-               c = find234(ssh_channels, &i, ssh_channelfind);
+               c = find234(ssh->channels, &i, ssh_channelfind);
                if (!c)
                    continue;          /* nonexistent channel */
-               c->v.v2.remwindow += ssh2_pkt_getuint32();
+               c->v.v2.remwindow += ssh2_pkt_getuint32(ssh);
            }
-       } while (pktin.type == SSH2_MSG_CHANNEL_WINDOW_ADJUST);
+       } while (ssh->pktin.type == SSH2_MSG_CHANNEL_WINDOW_ADJUST);
 
-       if (pktin.type != SSH2_MSG_CHANNEL_SUCCESS) {
-           if (pktin.type != SSH2_MSG_CHANNEL_FAILURE) {
-               bombout(("Server got confused by pty request"));
+       if (ssh->pktin.type != SSH2_MSG_CHANNEL_SUCCESS) {
+           if (ssh->pktin.type != SSH2_MSG_CHANNEL_FAILURE) {
+               bombout((ssh,"Unexpected response to pty request:"
+                        " packet type %d", ssh->pktin.type));
                crReturnV;
            }
-           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");
        }
     } else {
-       ssh_editing = ssh_echoing = 1;
+       ssh->editing = ssh->echoing = 1;
     }
 
     /*
-     * Start a shell or a remote command.
+     * Start a shell or a remote command. We may have to attempt
+     * this twice if the config data has provided a second choice
+     * of command.
      */
-    ssh2_pkt_init(SSH2_MSG_CHANNEL_REQUEST);
-    ssh2_pkt_adduint32(mainchan->remoteid);    /* recipient channel */
-    if (cfg.ssh_subsys) {
-       ssh2_pkt_addstring("subsystem");
-       ssh2_pkt_addbool(1);           /* want reply */
-       ssh2_pkt_addstring(cfg.remote_cmd_ptr);
-    } else if (*cfg.remote_cmd_ptr) {
-       ssh2_pkt_addstring("exec");
-       ssh2_pkt_addbool(1);           /* want reply */
-       ssh2_pkt_addstring(cfg.remote_cmd_ptr);
-    } else {
-       ssh2_pkt_addstring("shell");
-       ssh2_pkt_addbool(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 (1) {
+       int subsys;
+       char *cmd;
+
+       if (ssh->fallback_cmd) {
+           subsys = cfg.ssh_subsys2;
+           cmd = cfg.remote_cmd_ptr2;
+       } else {
+           subsys = cfg.ssh_subsys;
+           cmd = cfg.remote_cmd_ptr;
+       }
+
+       ssh2_pkt_init(ssh, SSH2_MSG_CHANNEL_REQUEST);
+       ssh2_pkt_adduint32(ssh, ssh->mainchan->remoteid);       /* recipient channel */
+       if (subsys) {
+           ssh2_pkt_addstring(ssh, "subsystem");
+           ssh2_pkt_addbool(ssh, 1);          /* want reply */
+           ssh2_pkt_addstring(ssh, cmd);
+       } else if (*cmd) {
+           ssh2_pkt_addstring(ssh, "exec");
+           ssh2_pkt_addbool(ssh, 1);          /* want reply */
+           ssh2_pkt_addstring(ssh, cmd);
+       } else {
+           ssh2_pkt_addstring(ssh, "shell");
+           ssh2_pkt_addbool(ssh, 1);          /* want reply */
        }
-    } while (pktin.type == SSH2_MSG_CHANNEL_WINDOW_ADJUST);
-    if (pktin.type != SSH2_MSG_CHANNEL_SUCCESS) {
-       if (pktin.type != SSH2_MSG_CHANNEL_FAILURE) {
-           bombout(("Server got confused by shell/command request"));
+       ssh2_pkt_send(ssh);
+       do {
+           crWaitUntilV(ispkt);
+           if (ssh->pktin.type == SSH2_MSG_CHANNEL_WINDOW_ADJUST) {
+               unsigned i = ssh2_pkt_getuint32(ssh);
+               struct ssh_channel *c;
+               c = find234(ssh->channels, &i, ssh_channelfind);
+               if (!c)
+                   continue;          /* nonexistent channel */
+               c->v.v2.remwindow += ssh2_pkt_getuint32(ssh);
+           }
+       } while (ssh->pktin.type == SSH2_MSG_CHANNEL_WINDOW_ADJUST);
+       if (ssh->pktin.type != SSH2_MSG_CHANNEL_SUCCESS) {
+           if (ssh->pktin.type != SSH2_MSG_CHANNEL_FAILURE) {
+               bombout((ssh,"Unexpected response to shell/command request:"
+                        " packet type %d", ssh->pktin.type));
+               crReturnV;
+           }
+           /*
+            * We failed to start the command. If this is the
+            * fallback command, we really are finished; if it's
+            * not, and if the fallback command exists, try falling
+            * back to it before complaining.
+            */
+           if (!ssh->fallback_cmd && cfg.remote_cmd_ptr2 != NULL) {
+               logevent("Primary command failed; attempting fallback");
+               ssh->fallback_cmd = TRUE;
+               continue;
+           }
+           bombout((ssh,"Server refused to start a shell/command"));
            crReturnV;
+       } else {
+           logevent("Started a shell/command");
        }
-       bombout(("Server refused to start a shell/command"));
-       crReturnV;
-    } 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);              /* cause ldisc to notice changes */
-    ssh_send_ok = 1;
+    if (ssh->ldisc)
+       ldisc_send(ssh->ldisc, NULL, 0, 0);/* cause ldisc to notice changes */
+    ssh->send_ok = 1;
     while (1) {
-       static int try_send;
        crReturnV;
-       try_send = FALSE;
+       s->try_send = FALSE;
        if (ispkt) {
-           if (pktin.type == SSH2_MSG_CHANNEL_DATA ||
-               pktin.type == SSH2_MSG_CHANNEL_EXTENDED_DATA) {
+           if (ssh->pktin.type == SSH2_MSG_CHANNEL_DATA ||
+               ssh->pktin.type == SSH2_MSG_CHANNEL_EXTENDED_DATA) {
                char *data;
                int length;
-               unsigned i = ssh2_pkt_getuint32();
+               unsigned i = ssh2_pkt_getuint32(ssh);
                struct ssh_channel *c;
-               c = find234(ssh_channels, &i, ssh_channelfind);
+               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)
+               if (ssh->pktin.type == SSH2_MSG_CHANNEL_EXTENDED_DATA &&
+                   ssh2_pkt_getuint32(ssh) != SSH2_EXTENDED_DATA_STDERR)
                    continue;          /* extended but not stderr */
-               ssh2_pkt_getstring(&data, &length);
+               ssh2_pkt_getstring(ssh, &data, &length);
                if (data) {
                    int bufsize;
                    c->v.v2.locwindow -= length;
                    switch (c->type) {
                      case CHAN_MAINSESSION:
                        bufsize =
-                           from_backend(pktin.type ==
+                           from_backend(ssh->frontend, ssh->pktin.type ==
                                         SSH2_MSG_CHANNEL_EXTENDED_DATA,
                                         data, length);
                        break;
@@ -4615,9 +5448,8 @@ static void do_ssh2_authconn(unsigned char *in, int inlen, int ispkt)
                                    sentreply = "\0\0\0\1\5";
                                    replylen = 5;
                                }
-                               ssh2_add_channel_data(c, sentreply,
-                                                     replylen);
-                               try_send = TRUE;
+                               ssh2_add_channel_data(c, sentreply, replylen);
+                               s->try_send = TRUE;
                                if (reply)
                                    sfree(reply);
                                sfree(c->u.a.message);
@@ -4634,17 +5466,11 @@ static void do_ssh2_authconn(unsigned char *in, int inlen, int ispkt)
                    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_REQUEST) {
-               continue;              /* exit status et al; ignore (FIXME?) */
-           } else if (pktin.type == SSH2_MSG_CHANNEL_EOF) {
-               unsigned i = ssh2_pkt_getuint32();
+           } else if (ssh->pktin.type == SSH2_MSG_CHANNEL_EOF) {
+               unsigned i = ssh2_pkt_getuint32(ssh);
                struct ssh_channel *c;
 
-               c = find234(ssh_channels, &i, ssh_channelfind);
+               c = find234(ssh->channels, &i, ssh_channelfind);
                if (!c)
                    continue;          /* nonexistent channel */
 
@@ -4661,88 +5487,214 @@ static void do_ssh2_authconn(unsigned char *in, int inlen, int ispkt)
                    pfd_close(c->u.pfd.s);
                    sshfwd_close(c);
                }
-           } else if (pktin.type == SSH2_MSG_CHANNEL_CLOSE) {
-               unsigned i = ssh2_pkt_getuint32();
+           } else if (ssh->pktin.type == SSH2_MSG_CHANNEL_CLOSE) {
+               unsigned i = ssh2_pkt_getuint32(ssh);
                struct ssh_channel *c;
 
-               c = find234(ssh_channels, &i, ssh_channelfind);
-               if (!c)
-                   continue;          /* nonexistent channel */
-               if (c->closes == 0) {
-                   ssh2_pkt_init(SSH2_MSG_CHANNEL_CLOSE);
-                   ssh2_pkt_adduint32(c->remoteid);
-                   ssh2_pkt_send();
+               c = find234(ssh->channels, &i, ssh_channelfind);
+               if (!c || ((int)c->remoteid) == -1) {
+                   bombout((ssh,"Received CHANNEL_CLOSE for %s channel %d\n",
+                            c ? "half-open" : "nonexistent", i));
                }
                /* 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;
                }
-               del234(ssh_channels, c);
+               if (c->closes == 0) {
+                   ssh2_pkt_init(ssh, SSH2_MSG_CHANNEL_CLOSE);
+                   ssh2_pkt_adduint32(ssh, c->remoteid);
+                   ssh2_pkt_send(ssh);
+               }
+               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 (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();
-                   ssh_state = SSH_STATE_CLOSED;
+                   ssh2_pkt_init(ssh, SSH2_MSG_DISCONNECT);
+                   ssh2_pkt_adduint32(ssh, SSH2_DISCONNECT_BY_APPLICATION);
+                   ssh2_pkt_addstring(ssh, "All open channels closed");
+                   ssh2_pkt_addstring(ssh, "en");      /* language tag */
+                   ssh2_pkt_send(ssh);
+#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();
+           } else if (ssh->pktin.type == SSH2_MSG_CHANNEL_WINDOW_ADJUST) {
+               unsigned i = ssh2_pkt_getuint32(ssh);
                struct ssh_channel *c;
-               c = find234(ssh_channels, &i, ssh_channelfind);
+               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();
+               c->v.v2.remwindow += ssh2_pkt_getuint32(ssh);
+               s->try_send = TRUE;
+           } else if (ssh->pktin.type == SSH2_MSG_CHANNEL_OPEN_CONFIRMATION) {
+               unsigned i = ssh2_pkt_getuint32(ssh);
                struct ssh_channel *c;
-               c = find234(ssh_channels, &i, ssh_channelfind);
+               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->remoteid = ssh2_pkt_getuint32(ssh);
                c->type = CHAN_SOCKDATA;
-               c->closes = 0;
-               c->v.v2.remwindow = ssh2_pkt_getuint32();
-               c->v.v2.remmaxpkt = ssh2_pkt_getuint32();
-               bufchain_init(&c->v.v2.outbuffer);
-               pfd_confirm(c->u.pfd.s);
-           } else if (pktin.type == SSH2_MSG_CHANNEL_OPEN) {
+               c->v.v2.remwindow = ssh2_pkt_getuint32(ssh);
+               c->v.v2.remmaxpkt = ssh2_pkt_getuint32(ssh);
+               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(ssh, SSH2_MSG_CHANNEL_CLOSE);
+                   ssh2_pkt_adduint32(ssh, c->remoteid);
+                   ssh2_pkt_send(ssh);
+               }
+           } else if (ssh->pktin.type == SSH2_MSG_CHANNEL_OPEN_FAILURE) {
+               unsigned i = ssh2_pkt_getuint32(ssh);
+               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);
+
+               del234(ssh->channels, c);
+               sfree(c);
+           } else if (ssh->pktin.type == SSH2_MSG_CHANNEL_REQUEST) {
+               unsigned localid;
+               char *type;
+               int typelen, want_reply;
+               struct ssh_channel *c;
+
+               localid = ssh2_pkt_getuint32(ssh);
+               ssh2_pkt_getstring(ssh, &type, &typelen);
+               want_reply = ssh2_pkt_getbool(ssh);
+
+               /*
+                * 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(ssh, SSH2_MSG_DISCONNECT);
+                   ssh2_pkt_adduint32(ssh, SSH2_DISCONNECT_BY_APPLICATION);
+                   ssh2_pkt_addstring(ssh, buf);
+                   ssh2_pkt_addstring(ssh, "en");      /* language tag */
+                   ssh2_pkt_send(ssh);
+                   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 == ssh->mainchan) {
+                   /* We recognise "exit-status" on the primary channel. */
+                   char buf[100];
+                   ssh->exitcode = ssh2_pkt_getuint32(ssh);
+                   sprintf(buf, "Server sent command exit status %d",
+                           ssh->exitcode);
+                   logevent(buf);
+                   if (want_reply) {
+                       ssh2_pkt_init(ssh, SSH2_MSG_CHANNEL_SUCCESS);
+                       ssh2_pkt_adduint32(ssh, c->remoteid);
+                       ssh2_pkt_send(ssh);
+                   }
+               } 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(ssh, SSH2_MSG_CHANNEL_FAILURE);
+                       ssh2_pkt_adduint32(ssh, c->remoteid);
+                       ssh2_pkt_send(ssh);
+                   }
+               }
+           } else if (ssh->pktin.type == SSH2_MSG_GLOBAL_REQUEST) {
+               char *type;
+               int typelen, want_reply;
+
+               ssh2_pkt_getstring(ssh, &type, &typelen);
+               want_reply = ssh2_pkt_getbool(ssh);
+
+                /*
+                 * 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(ssh, SSH2_MSG_REQUEST_FAILURE);
+                    ssh2_pkt_send(ssh);
+               }
+           } else if (ssh->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);
+               ssh2_pkt_getstring(ssh, &type, &typelen);
                c = smalloc(sizeof(struct ssh_channel));
+               c->ssh = ssh;
 
-               remid = ssh2_pkt_getuint32();
-               winsize = ssh2_pkt_getuint32();
-               pktsize = ssh2_pkt_getuint32();
+               remid = ssh2_pkt_getuint32(ssh);
+               winsize = ssh2_pkt_getuint32(ssh);
+               pktsize = ssh2_pkt_getuint32(ssh);
 
                if (typelen == 3 && !memcmp(type, "x11", 3)) {
-                   if (!ssh_X11_fwd_enabled)
+                   if (!ssh->X11_fwd_enabled)
                        error = "X11 forwarding is not enabled";
-                   else if (x11_init(&c->u.x11.s, cfg.x11_display, c) !=
-                            NULL) {
+                   else if (x11_init(&c->u.x11.s, cfg.x11_display, c,
+                                     ssh->x11auth) != NULL) {
                        error = "Unable to open an X11 connection";
                    } else {
                        c->type = CHAN_X11;
@@ -4752,21 +5704,18 @@ static void do_ssh2_authconn(unsigned char *in, int inlen, int ispkt)
                    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);
+                   ssh2_pkt_getstring(ssh, &dummy, &dummylen);/* skip address */
+                   pf.sport = ssh2_pkt_getuint32(ssh);
+                   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);
+                       logeventf(ssh, "Received remote port open request"
+                                 " for %s:%d", realpf->dhost, realpf->dport);
                        if (e != NULL) {
-                           sprintf(buf, "Port open failed: %s", e);
-                           logevent(buf);
+                           logeventf(ssh, "Port open failed: %s", e);
                            error = "Port open failed";
                        } else {
                            logevent("Forwarded port opened successfully");
@@ -4775,7 +5724,7 @@ static void do_ssh2_authconn(unsigned char *in, int inlen, int ispkt)
                    }
                } else if (typelen == 22 &&
                           !memcmp(type, "auth-agent@openssh.com", 3)) {
-                   if (!ssh_agentfwd_enabled)
+                   if (!ssh->agentfwd_enabled)
                        error = "Agent forwarding is not enabled";
                    else {
                        c->type = CHAN_AGENT;   /* identify channel type */
@@ -4787,46 +5736,46 @@ static void do_ssh2_authconn(unsigned char *in, int inlen, int ispkt)
 
                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();
+                   ssh2_pkt_init(ssh, SSH2_MSG_CHANNEL_OPEN_FAILURE);
+                   ssh2_pkt_adduint32(ssh, c->remoteid);
+                   ssh2_pkt_adduint32(ssh, SSH2_OPEN_CONNECT_FAILED);
+                   ssh2_pkt_addstring(ssh, error);
+                   ssh2_pkt_addstring(ssh, "en");      /* language tag */
+                   ssh2_pkt_send(ssh);
                    sfree(c);
                } else {
-                   c->localid = alloc_channel_id();
+                   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);
-                   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();
+                   add234(ssh->channels, c);
+                   ssh2_pkt_init(ssh, SSH2_MSG_CHANNEL_OPEN_CONFIRMATION);
+                   ssh2_pkt_adduint32(ssh, c->remoteid);
+                   ssh2_pkt_adduint32(ssh, c->localid);
+                   ssh2_pkt_adduint32(ssh, c->v.v2.locwindow);
+                   ssh2_pkt_adduint32(ssh, 0x4000UL);  /* our max pkt size */
+                   ssh2_pkt_send(ssh);
                }
            } else {
-               bombout(("Strange packet received: type %d", pktin.type));
+               bombout((ssh,"Strange packet received: type %d", ssh->pktin.type));
                crReturnV;
            }
        } else {
            /*
             * 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, 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++) {
+           for (i = 0; NULL != (c = index234(ssh->channels, i)); i++) {
                int bufsize = ssh2_try_send(c);
                if (bufsize == 0) {
                    switch (c->type) {
@@ -4856,11 +5805,11 @@ static void do_ssh2_authconn(unsigned char *in, int inlen, int ispkt)
 /*
  * Handle the top-level SSH2 protocol.
  */
-static void ssh2_protocol(unsigned char *in, int inlen, int ispkt)
+static void ssh2_protocol(Ssh ssh, unsigned char *in, int inlen, int ispkt)
 {
-    if (do_ssh2_transport(in, inlen, ispkt) == 0)
+    if (do_ssh2_transport(ssh, in, inlen, ispkt) == 0)
        return;
-    do_ssh2_authconn(in, inlen, ispkt);
+    do_ssh2_authconn(ssh, in, inlen, ispkt);
 }
 
 /*
@@ -4868,22 +5817,84 @@ 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)
+static char *ssh_init(void *frontend_handle, void **backend_handle,
+                     char *host, int port, char **realhost, int nodelay)
 {
     char *p;
+    Ssh ssh;
+
+    ssh = smalloc(sizeof(*ssh));
+    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->hostkey = NULL;
+    ssh->exitcode = -1;
+    ssh->state = SSH_STATE_PREPACKET;
+    ssh->size_needed = FALSE;
+    ssh->eof_needed = FALSE;
+    ssh->ldisc = NULL;
+    ssh->logctx = NULL;
+    {
+       static const struct Packet empty = { 0, 0, NULL, NULL, 0 };
+       ssh->pktin = ssh->pktout = empty;
+    }
+    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->ssh1_protocol_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;
+
+    *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->frontend = frontend_handle;
+    ssh->term_width = cfg.width;
+    ssh->term_height = cfg.height;
 
-    p = connect_to_host(host, port, realhost);
+    ssh->send_ok = 0;
+    ssh->editing = 0;
+    ssh->echoing = 0;
+    ssh->v1_throttle_count = 0;
+    ssh->overall_bufsize = 0;
+    ssh->fallback_cmd = 0;
+
+    p = connect_to_host(ssh, host, port, realhost, nodelay);
     if (p != NULL)
        return p;
 
@@ -4893,24 +5904,27 @@ static char *ssh_init(char *host, int port, char **realhost)
 /*
  * 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, 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;
 
     /*
@@ -4918,16 +5932,17 @@ 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;
@@ -4936,32 +5951,38 @@ 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;
+
+    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->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();
+               ssh2_pkt_init(ssh, SSH2_MSG_CHANNEL_REQUEST);
+               ssh2_pkt_adduint32(ssh, ssh->mainchan->remoteid);
+               ssh2_pkt_addstring(ssh, "window-change");
+               ssh2_pkt_addbool(ssh, 0);
+               ssh2_pkt_adduint32(ssh, ssh->term_width);
+               ssh2_pkt_adduint32(ssh, ssh->term_height);
+               ssh2_pkt_adduint32(ssh, 0);
+               ssh2_pkt_adduint32(ssh, 0);
+               ssh2_pkt_send(ssh);
            }
        }
        break;
@@ -4973,53 +5994,59 @@ static void ssh_size(void)
  * 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;
+
     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);
+       if (ssh->version == 1) {
+           send_packet(ssh, SSH1_CMSG_EOF, PKT_END);
        } else {
-           ssh2_pkt_init(SSH2_MSG_CHANNEL_EOF);
-           ssh2_pkt_adduint32(mainchan->remoteid);
-           ssh2_pkt_send();
+           ssh2_pkt_init(ssh, SSH2_MSG_CHANNEL_EOF);
+           ssh2_pkt_adduint32(ssh, ssh->mainchan->remoteid);
+           ssh2_pkt_send(ssh);
        }
        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);
+       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();
+           ssh2_pkt_init(ssh, SSH2_MSG_IGNORE);
+           ssh2_pkt_addstring_start(ssh);
+           ssh2_pkt_send(ssh);
        }
     } else {
        /* 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->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;
-       add234(ssh_channels, c);
+       bufchain_init(&c->v.v2.outbuffer);
+       add234(ssh->channels, c);
     }
     return c;
 }
@@ -5028,75 +6055,107 @@ 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)
+void ssh_unthrottle(void *handle, int bufsize)
 {
-    if (ssh_version == 1) {
-       if (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;
 
-    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_END);
     } else {
-       ssh2_pkt_init(SSH2_MSG_CHANNEL_OPEN);
-       ssh2_pkt_addstring("direct-tcpip");
-       ssh2_pkt_adduint32(c->localid);
+       ssh2_pkt_init(ssh, SSH2_MSG_CHANNEL_OPEN);
+       ssh2_pkt_addstring(ssh, "direct-tcpip");
+       ssh2_pkt_adduint32(ssh, 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(ssh, c->v.v2.locwindow);/* our window size */
+       ssh2_pkt_adduint32(ssh, 0x4000UL);      /* our max pkt size */
+       ssh2_pkt_addstring(ssh, hostname);
+       ssh2_pkt_adduint32(ssh, 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(ssh, "client-side-connection");
+       ssh2_pkt_adduint32(ssh, 0);
+       ssh2_pkt_send(ssh);
     }
 }
 
 
-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 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;
+    return ssh->exitcode;
+}
+
+/*
+ * 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)
+{
+    Ssh ssh = (Ssh) handle;
+    return ssh->fallback_cmd;
+}
+
 Backend ssh_backend = {
     ssh_init,
     ssh_send,
@@ -5104,8 +6163,11 @@ Backend ssh_backend = {
     ssh_size,
     ssh_special,
     ssh_socket,
+    ssh_return_exitcode,
     ssh_sendok,
     ssh_ldisc,
+    ssh_provide_ldisc,
+    ssh_provide_logctx,
     ssh_unthrottle,
     22
 };