X-Git-Url: https://git.distorted.org.uk/u/mdw/putty/blobdiff_plain/43b5682aa6140913dfd750fe64cc15edb499d2d4..2ccb2fc83a62d8ded4b0287b72384ce22a83000c:/ssh.c

diff --git a/ssh.c b/ssh.c
index 9517e95f..75610c67 100644
--- a/ssh.c
+++ b/ssh.c
@@ -166,6 +166,110 @@ static const char *const ssh2_disconnect_reasons[] = {
 #define BUG_SSH2_REKEY                           64
 #define BUG_SSH2_PK_SESSIONID                   128
 
+/*
+ * Codes for terminal modes.
+ * Most of these are the same in SSH-1 and SSH-2.
+ * This list is derived from draft-ietf-secsh-connect-25 and
+ * SSH-1 RFC-1.2.31.
+ */
+static const struct {
+    const char* const mode;
+    int opcode;
+    enum { TTY_OP_CHAR, TTY_OP_BOOL } type;
+} ssh_ttymodes[] = {
+    /* "V" prefix discarded for special characters relative to SSH specs */
+    { "INTR",	      1, TTY_OP_CHAR },
+    { "QUIT",	      2, TTY_OP_CHAR },
+    { "ERASE",	      3, TTY_OP_CHAR },
+    { "KILL",	      4, TTY_OP_CHAR },
+    { "EOF",	      5, TTY_OP_CHAR },
+    { "EOL",	      6, TTY_OP_CHAR },
+    { "EOL2",	      7, TTY_OP_CHAR },
+    { "START",	      8, TTY_OP_CHAR },
+    { "STOP",	      9, TTY_OP_CHAR },
+    { "SUSP",	     10, TTY_OP_CHAR },
+    { "DSUSP",	     11, TTY_OP_CHAR },
+    { "REPRINT",     12, TTY_OP_CHAR },
+    { "WERASE",	     13, TTY_OP_CHAR },
+    { "LNEXT",	     14, TTY_OP_CHAR },
+    { "FLUSH",	     15, TTY_OP_CHAR },
+    { "SWTCH",	     16, TTY_OP_CHAR },
+    { "STATUS",	     17, TTY_OP_CHAR },
+    { "DISCARD",     18, TTY_OP_CHAR },
+    { "IGNPAR",	     30, TTY_OP_BOOL },
+    { "PARMRK",	     31, TTY_OP_BOOL },
+    { "INPCK",	     32, TTY_OP_BOOL },
+    { "ISTRIP",	     33, TTY_OP_BOOL },
+    { "INLCR",	     34, TTY_OP_BOOL },
+    { "IGNCR",	     35, TTY_OP_BOOL },
+    { "ICRNL",	     36, TTY_OP_BOOL },
+    { "IUCLC",	     37, TTY_OP_BOOL },
+    { "IXON",	     38, TTY_OP_BOOL },
+    { "IXANY",	     39, TTY_OP_BOOL },
+    { "IXOFF",	     40, TTY_OP_BOOL },
+    { "IMAXBEL",     41, TTY_OP_BOOL },
+    { "ISIG",	     50, TTY_OP_BOOL },
+    { "ICANON",	     51, TTY_OP_BOOL },
+    { "XCASE",	     52, TTY_OP_BOOL },
+    { "ECHO",	     53, TTY_OP_BOOL },
+    { "ECHOE",	     54, TTY_OP_BOOL },
+    { "ECHOK",	     55, TTY_OP_BOOL },
+    { "ECHONL",	     56, TTY_OP_BOOL },
+    { "NOFLSH",	     57, TTY_OP_BOOL },
+    { "TOSTOP",	     58, TTY_OP_BOOL },
+    { "IEXTEN",	     59, TTY_OP_BOOL },
+    { "ECHOCTL",     60, TTY_OP_BOOL },
+    { "ECHOKE",	     61, TTY_OP_BOOL },
+    { "PENDIN",	     62, TTY_OP_BOOL }, /* XXX is this a real mode? */
+    { "OPOST",	     70, TTY_OP_BOOL },
+    { "OLCUC",	     71, TTY_OP_BOOL },
+    { "ONLCR",	     72, TTY_OP_BOOL },
+    { "OCRNL",	     73, TTY_OP_BOOL },
+    { "ONOCR",	     74, TTY_OP_BOOL },
+    { "ONLRET",	     75, TTY_OP_BOOL },
+    { "CS7",	     90, TTY_OP_BOOL },
+    { "CS8",	     91, TTY_OP_BOOL },
+    { "PARENB",	     92, TTY_OP_BOOL },
+    { "PARODD",	     93, TTY_OP_BOOL }
+};
+
+/* Miscellaneous other tty-related constants. */
+#define SSH_TTY_OP_END		  0
+/* The opcodes for ISPEED/OSPEED differ between SSH-1 and SSH-2. */
+#define SSH1_TTY_OP_ISPEED	192
+#define SSH1_TTY_OP_OSPEED	193
+#define SSH2_TTY_OP_ISPEED	128
+#define SSH2_TTY_OP_OSPEED	129
+
+/* Helper functions for parsing tty-related config. */
+static unsigned int ssh_tty_parse_specchar(char *s)
+{
+    unsigned int ret;
+    if (*s) {
+	char *next = NULL;
+	ret = ctrlparse(s, &next);
+	if (!next) ret = s[0];
+    } else {
+	ret = 255; /* special value meaning "don't set" */
+    }
+    return ret;
+}
+static unsigned int ssh_tty_parse_boolean(char *s)
+{
+    if (stricmp(s, "yes") == 0 ||
+	stricmp(s, "on") == 0 ||
+	stricmp(s, "true") == 0 ||
+	stricmp(s, "+") == 0)
+	return 1; /* true */
+    else if (stricmp(s, "no") == 0 ||
+	     stricmp(s, "off") == 0 ||
+	     stricmp(s, "false") == 0 ||
+	     stricmp(s, "-") == 0)
+	return 0; /* false */
+    else
+	return (atoi(s) != 0);
+}
+
 #define translate(x) if (type == x) return #x
 #define translatec(x,ctx) if (type == x && (pkt_ctx & ctx)) return #x
 static char *ssh1_pkt_type(int type)
@@ -256,18 +360,6 @@ static char *ssh2_pkt_type(int pkt_ctx, int type)
 #undef translate
 #undef translatec
 
-#define GET_32BIT(cp) \
-    (((unsigned long)(unsigned char)(cp)[0] << 24) | \
-    ((unsigned long)(unsigned char)(cp)[1] << 16) | \
-    ((unsigned long)(unsigned char)(cp)[2] << 8) | \
-    ((unsigned long)(unsigned char)(cp)[3]))
-
-#define PUT_32BIT(cp, value) { \
-    (cp)[0] = (unsigned char)((value) >> 24); \
-    (cp)[1] = (unsigned char)((value) >> 16); \
-    (cp)[2] = (unsigned char)((value) >> 8); \
-    (cp)[3] = (unsigned char)(value); }
-
 /* Enumeration values for fields in SSH-1 packets */
 enum {
     PKT_END, PKT_INT, PKT_CHAR, PKT_DATA, PKT_STR, PKT_BIGNUM,
@@ -319,14 +411,19 @@ enum {
 typedef struct ssh_tag *Ssh;
 struct Packet;
 
+static struct Packet *ssh1_pkt_init(int pkt_type);
 static struct Packet *ssh2_pkt_init(int pkt_type);
+static void ssh_pkt_ensure(struct Packet *, int length);
+static void ssh_pkt_adddata(struct Packet *, void *data, int len);
+static void ssh_pkt_addbyte(struct Packet *, unsigned char value);
 static void ssh2_pkt_addbool(struct Packet *, unsigned char value);
-static void ssh2_pkt_adduint32(struct Packet *, unsigned long value);
-static void ssh2_pkt_addstring_start(struct Packet *);
-static void ssh2_pkt_addstring_str(struct Packet *, char *data);
-static void ssh2_pkt_addstring_data(struct Packet *, char *data, int len);
-static void ssh2_pkt_addstring(struct Packet *, char *data);
+static void ssh_pkt_adduint32(struct Packet *, unsigned long value);
+static void ssh_pkt_addstring_start(struct Packet *);
+static void ssh_pkt_addstring_str(struct Packet *, char *data);
+static void ssh_pkt_addstring_data(struct Packet *, char *data, int len);
+static void ssh_pkt_addstring(struct Packet *, char *data);
 static unsigned char *ssh2_mpint_fmt(Bignum b, int *len);
+static void ssh1_pkt_addmp(struct Packet *, Bignum b);
 static void ssh2_pkt_addmp(struct Packet *, Bignum b);
 static int ssh2_pkt_construct(Ssh, struct Packet *);
 static void ssh2_pkt_send(Ssh, struct Packet *);
@@ -342,55 +439,33 @@ static void do_ssh2_authconn(Ssh ssh, unsigned char *in, int inlen,
  * 
  *  - SSH1_BUFFER_LIMIT is the amount of backlog that must build up
  *    on a local data stream before we throttle the whole SSH
- *    connection (in SSH1 only). Throttling the whole connection is
+ *    connection (in SSH-1 only). Throttling the whole connection is
  *    pretty drastic so we set this high in the hope it won't
  *    happen very often.
  * 
  *  - SSH_MAX_BACKLOG is the amount of backlog that must build up
  *    on the SSH connection itself before we defensively throttle
  *    _all_ local data streams. This is pretty drastic too (though
- *    thankfully unlikely in SSH2 since the window mechanism should
+ *    thankfully unlikely in SSH-2 since the window mechanism should
  *    ensure that the server never has any need to throttle its end
  *    of the connection), so we set this high as well.
  * 
- *  - OUR_V2_WINSIZE is the maximum window size we present on SSH2
+ *  - OUR_V2_WINSIZE is the maximum window size we present on SSH-2
  *    channels.
  */
 
 #define SSH1_BUFFER_LIMIT 32768
 #define SSH_MAX_BACKLOG 32768
 #define OUR_V2_WINSIZE 16384
+#define OUR_V2_MAXPKT 0x4000UL
 
 const static struct ssh_signkey *hostkey_algs[] = { &ssh_rsa, &ssh_dss };
 
-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(void *handle, 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_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
+    &ssh_hmac_sha1, &ssh_hmac_md5
 };
 const static struct ssh_mac *buggymacs[] = {
-    &ssh_sha1_buggy, &ssh_md5, &ssh_mac_none
+    &ssh_hmac_sha1_buggy, &ssh_hmac_md5
 };
 
 static void *ssh_comp_none_init(void)
@@ -435,8 +510,10 @@ struct ssh_channel {
     Ssh ssh;			       /* pointer back to main context */
     unsigned remoteid, localid;
     int type;
+    /* True if we opened this channel but server hasn't confirmed. */
+    int halfopen;
     /*
-     * In SSH1, this value contains four bits:
+     * In SSH-1, this value contains four bits:
      * 
      *   1   We have sent SSH1_MSG_CHANNEL_CLOSE.
      *   2   We have sent SSH1_MSG_CHANNEL_CLOSE_CONFIRMATION.
@@ -472,11 +549,11 @@ struct ssh_channel {
 };
 
 /*
- * 2-3-4 tree storing remote->local port forwardings. SSH 1 and SSH
- * 2 use this structure in different ways, reflecting SSH 2's
+ * 2-3-4 tree storing remote->local port forwardings. SSH-1 and SSH-2
+ * use this structure in different ways, reflecting SSH-2's
  * altogether saner approach to port forwarding.
  * 
- * In SSH 1, you arrange a remote forwarding by sending the server
+ * In SSH-1, you arrange a remote forwarding by sending the server
  * the remote port number, and the local destination host:port.
  * When a connection comes in, the server sends you back that
  * host:port pair, and you connect to it. This is a ready-made
@@ -488,15 +565,15 @@ struct ssh_channel {
  * host:port pairs we _are_ trying to forward to, and reject a
  * connection request from the server if it's not in the list.
  * 
- * In SSH 2, each side of the connection minds its own business and
+ * In SSH-2, each side of the connection minds its own business and
  * doesn't send unnecessary information to the other. You arrange a
  * remote forwarding by sending the server just the remote port
  * number. When a connection comes in, the server tells you which
  * of its ports was connected to; and _you_ have to remember what
  * local host:port pair went with that port number.
  * 
- * Hence, in SSH 1 this structure is indexed by destination
- * host:port pair, whereas in SSH 2 it is indexed by source port.
+ * Hence, in SSH-1 this structure is indexed by destination
+ * host:port pair, whereas in SSH-2 it is indexed by source port.
  */
 struct ssh_portfwd; /* forward declaration */
 
@@ -531,14 +608,15 @@ struct ssh_portfwd {
 	     sfree((pf)->sserv), sfree((pf)->dserv)) : (void)0 ), sfree(pf) )
 
 struct Packet {
-    long length;
-    int type;
-    unsigned long sequence;
-    unsigned char *data;
-    unsigned char *body;
-    long savedpos;
-    long maxlen;
-    long encrypted_len;		       /* for SSH2 total-size counting */
+    long length;	    /* length of `data' actually used */
+    long forcepad;	    /* SSH-2: force padding to at least this length */
+    int type;		    /* only used for incoming packets */
+    unsigned long sequence; /* SSH-2 incoming sequence number */
+    unsigned char *data;    /* allocated storage */
+    unsigned char *body;    /* offset of payload within `data' */
+    long savedpos;	    /* temporary index into `data' (for strings) */
+    long maxlen;	    /* amount of storage allocated for `data' */
+    long encrypted_len;	    /* for SSH-2 total-size counting */
 
     /*
      * State associated with packet logging
@@ -548,9 +626,9 @@ struct Packet {
     struct logblank_t *blanks;
 };
 
-static void ssh1_protocol(Ssh ssh, unsigned char *in, int inlen,
+static void ssh1_protocol(Ssh ssh, void *vin, int inlen,
 			  struct Packet *pktin);
-static void ssh2_protocol(Ssh ssh, unsigned char *in, int inlen,
+static void ssh2_protocol(Ssh ssh, void *vin, int inlen,
 			  struct Packet *pktin);
 static void ssh1_protocol_setup(Ssh ssh);
 static void ssh2_protocol_setup(Ssh ssh);
@@ -561,12 +639,12 @@ 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 ssh_sendbuffer(void *handle);
-static void ssh_do_close(Ssh ssh);
+static int ssh_do_close(Ssh ssh, int notify_exit);
 static unsigned long ssh_pkt_getuint32(struct Packet *pkt);
 static int ssh2_pkt_getbool(struct Packet *pkt);
 static void ssh_pkt_getstring(struct Packet *pkt, char **p, int *length);
 static void ssh2_timer(void *ctx, long now);
-static int do_ssh2_transport(Ssh ssh, unsigned char *in, int inlen,
+static int do_ssh2_transport(Ssh ssh, void *vin, int inlen,
 			     struct Packet *pktin);
 
 struct rdpkt1_state_tag {
@@ -601,7 +679,8 @@ struct ssh_tag {
     const struct plug_function_table *fn;
     /* the above field _must_ be first in the structure */
 
-    SHA_State exhash, exhashbase;
+    char *v_c, *v_s;
+    void *exhash;
 
     Socket s;
 
@@ -626,7 +705,8 @@ struct ssh_tag {
     void *cs_comp_ctx, *sc_comp_ctx;
     const struct ssh_kex *kex;
     const struct ssh_signkey *hostkey;
-    unsigned char v2_session_id[20];
+    unsigned char v2_session_id[32];
+    int v2_session_id_len;
     void *kex_ctx;
 
     char *savedhost;
@@ -642,6 +722,8 @@ struct ssh_tag {
     tree234 *channels;		       /* indexed by local id */
     struct ssh_channel *mainchan;      /* primary session channel */
     int exitcode;
+    int close_expected;
+    int clean_exit;
 
     tree234 *rportfwds, *portfwds;
 
@@ -669,6 +751,7 @@ struct ssh_tag {
      */
     int fallback_cmd;
 
+    bufchain banner;	/* accumulates banners during do_ssh2_authconn */
     /*
      * Used for username and password input.
      */
@@ -686,7 +769,7 @@ struct ssh_tag {
     int overall_bufsize;
     int throttled_all;
     int v1_stdout_throttling;
-    int v2_outgoing_sequence;
+    unsigned long v2_outgoing_sequence;
 
     int ssh1_rdpkt_crstate;
     int ssh2_rdpkt_crstate;
@@ -705,10 +788,10 @@ struct ssh_tag {
     struct rdpkt1_state_tag rdpkt1_state;
     struct rdpkt2_state_tag rdpkt2_state;
 
-    /* ssh1 and ssh2 use this for different things, but both use it */
+    /* SSH-1 and SSH-2 use this for different things, but both use it */
     int protocol_initial_phase_done;
 
-    void (*protocol) (Ssh ssh, unsigned char *in, int inlen,
+    void (*protocol) (Ssh ssh, void *vin, int inlen,
 		      struct Packet *pkt);
     struct Packet *(*s_rdpkt) (Ssh ssh, unsigned char **data, int *datalen);
 
@@ -721,10 +804,23 @@ struct ssh_tag {
     Config cfg;
 
     /*
-     * Used to transfer data back from async agent callbacks.
+     * Used to transfer data back from async callbacks.
      */
     void *agent_response;
     int agent_response_len;
+    int user_response;
+
+    /*
+     * The SSH connection can be set as `frozen', meaning we are
+     * not currently accepting incoming data from the network. This
+     * is slightly more serious than setting the _socket_ as
+     * frozen, because we may already have had data passed to us
+     * from the network which we need to delay processing until
+     * after the freeze is lifted, so we also need a bufchain to
+     * store that data.
+     */
+    int frozen;
+    bufchain queued_incoming_data;
 
     /*
      * Dispatch table for packet types that we may have to deal
@@ -772,7 +868,7 @@ static void logeventf(Ssh ssh, const char *fmt, ...)
 #define bombout(msg) \
     do { \
         char *text = dupprintf msg; \
-	ssh_do_close(ssh); \
+	ssh_do_close(ssh, FALSE); \
         logevent(text); \
         connection_fatal(ssh->frontend, "%s", text); \
         sfree(text); \
@@ -797,6 +893,29 @@ static void end_log_omission(Ssh ssh, struct Packet *pkt)
     pkt->logmode = PKTLOG_EMIT;
 }
 
+/* Helper function for common bits of parsing cfg.ttymodes. */
+static void parse_ttymodes(Ssh ssh, char *modes,
+			   void (*do_mode)(void *data, char *mode, char *val),
+			   void *data)
+{
+    while (*modes) {
+	char *t = strchr(modes, '\t');
+	char *m = snewn(t-modes+1, char);
+	char *val;
+	strncpy(m, modes, t-modes);
+	m[t-modes] = '\0';
+	if (*(t+1) == 'A')
+	    val = get_ttymode(ssh->frontend, m);
+	else
+	    val = dupstr(t+2);
+	if (val)
+	    do_mode(data, m, val);
+	sfree(m);
+	sfree(val);
+	modes += strlen(modes) + 1;
+    }
+}
+
 static int ssh_channelcmp(void *av, void *bv)
 {
     struct ssh_channel *a = (struct ssh_channel *) av;
@@ -964,7 +1083,7 @@ static struct Packet *ssh_new_packet(void)
 {
     struct Packet *pkt = snew(struct Packet);
 
-    pkt->data = NULL;
+    pkt->body = pkt->data = NULL;
     pkt->maxlen = 0;
     pkt->logmode = PKTLOG_EMIT;
     pkt->nblanks = 0;
@@ -1150,7 +1269,8 @@ static struct Packet *ssh2_rdpkt(Ssh ssh, unsigned char **data, int *datalen)
      * _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) {
+    if (st->len < 0 || st->len > 35000 || st->pad < 4 ||
+	st->len - st->pad < 1 || (st->len + 4) % st->cipherblk != 0) {
 	bombout(("Incoming packet was garbled on decryption"));
 	ssh_free_packet(st->pktin);
 	crStop(NULL);
@@ -1264,36 +1384,9 @@ static struct Packet *ssh2_rdpkt(Ssh ssh, unsigned char **data, int *datalen)
     crFinish(st->pktin);
 }
 
-static void ssh1_pktout_size(struct Packet *pkt, int len)
+static int s_wrpkt_prepare(Ssh ssh, struct Packet *pkt, int *offset_p)
 {
-    int pad, biglen;
-
-    len += 5;			       /* type and CRC */
-    pad = 8 - (len % 8);
-    biglen = len + pad;
-
-    pkt->length = len - 5;
-    if (pkt->maxlen < biglen) {
-	pkt->maxlen = biglen;
-	pkt->data = sresize(pkt->data, biglen + 4 + APIEXTRA, unsigned char);
-    }
-    pkt->body = pkt->data + 4 + pad + 1;
-}
-
-static struct Packet *s_wrpkt_start(int type, int len)
-{
-    struct Packet *pkt = ssh_new_packet();
-    ssh1_pktout_size(pkt, len);
-    pkt->type = type;
-    /* Initialise log omission state */
-    pkt->nblanks = 0;
-    pkt->blanks = NULL;
-    return pkt;
-}
-
-static int s_wrpkt_prepare(Ssh ssh, struct Packet *pkt)
-{
-    int pad, biglen, i;
+    int pad, biglen, i, pktoffs;
     unsigned long crc;
 #ifdef __SC__
     /*
@@ -1306,12 +1399,10 @@ static int s_wrpkt_prepare(Ssh ssh, struct Packet *pkt)
 #endif
     int len;
 
-    pkt->body[-1] = pkt->type;
-
     if (ssh->logctx)
-	log_packet(ssh->logctx, PKT_OUTGOING, pkt->type,
-		   ssh1_pkt_type(pkt->type),
-		   pkt->body, pkt->length,
+	log_packet(ssh->logctx, PKT_OUTGOING, pkt->data[12],
+		   ssh1_pkt_type(pkt->data[12]),
+		   pkt->body, pkt->length - (pkt->body - pkt->data),
 		   pkt->nblanks, pkt->blanks);
     sfree(pkt->blanks); pkt->blanks = NULL;
     pkt->nblanks = 0;
@@ -1320,132 +1411,99 @@ static int s_wrpkt_prepare(Ssh ssh, struct Packet *pkt)
 	unsigned char *compblk;
 	int complen;
 	zlib_compress_block(ssh->cs_comp_ctx,
-			    pkt->body - 1, pkt->length + 1,
+			    pkt->data + 12, pkt->length - 12,
 			    &compblk, &complen);
-	ssh1_pktout_size(pkt, complen - 1);
-	memcpy(pkt->body - 1, compblk, complen);
+	memcpy(pkt->data + 12, compblk, complen);
 	sfree(compblk);
+	pkt->length = complen + 12;
     }
 
-    len = pkt->length + 5;	       /* type and CRC */
+    ssh_pkt_ensure(pkt, pkt->length + 4); /* space for CRC */
+    pkt->length += 4;
+    len = pkt->length - 4 - 8;	/* len(type+data+CRC) */
     pad = 8 - (len % 8);
-    biglen = len + pad;
+    pktoffs = 8 - pad;
+    biglen = len + pad;		/* len(padding+type+data+CRC) */
 
-    for (i = 0; i < pad; i++)
-	pkt->data[i + 4] = random_byte();
-    crc = crc32_compute(pkt->data + 4, biglen - 4);
-    PUT_32BIT(pkt->data + biglen, crc);
-    PUT_32BIT(pkt->data, len);
+    for (i = pktoffs; i < 4+8; i++)
+	pkt->data[i] = random_byte();
+    crc = crc32_compute(pkt->data + pktoffs + 4, biglen - 4); /* all ex len */
+    PUT_32BIT(pkt->data + pktoffs + 4 + biglen - 4, crc);
+    PUT_32BIT(pkt->data + pktoffs, len);
 
     if (ssh->cipher)
-	ssh->cipher->encrypt(ssh->v1_cipher_ctx, pkt->data + 4, biglen);
+	ssh->cipher->encrypt(ssh->v1_cipher_ctx,
+			     pkt->data + pktoffs + 4, biglen);
 
-    return biglen + 4;
+    if (offset_p) *offset_p = pktoffs;
+    return biglen + 4;		/* len(length+padding+type+data+CRC) */
 }
 
 static void s_wrpkt(Ssh ssh, struct Packet *pkt)
 {
-    int len, backlog;
-    len = s_wrpkt_prepare(ssh, pkt);
-    backlog = sk_write(ssh->s, (char *)pkt->data, len);
+    int len, backlog, offset;
+    len = s_wrpkt_prepare(ssh, pkt, &offset);
+    backlog = sk_write(ssh->s, (char *)pkt->data + offset, len);
     if (backlog > SSH_MAX_BACKLOG)
 	ssh_throttle_all(ssh, 1, backlog);
+    ssh_free_packet(pkt);
 }
 
 static void s_wrpkt_defer(Ssh ssh, struct Packet *pkt)
 {
-    int len;
-    len = s_wrpkt_prepare(ssh, pkt);
+    int len, offset;
+    len = s_wrpkt_prepare(ssh, pkt, &offset);
     if (ssh->deferred_len + len > ssh->deferred_size) {
 	ssh->deferred_size = ssh->deferred_len + len + 128;
 	ssh->deferred_send_data = sresize(ssh->deferred_send_data,
 					  ssh->deferred_size,
 					  unsigned char);
     }
-    memcpy(ssh->deferred_send_data + ssh->deferred_len, pkt->data, len);
+    memcpy(ssh->deferred_send_data + ssh->deferred_len,
+	   pkt->data + offset, len);
     ssh->deferred_len += len;
+    ssh_free_packet(pkt);
 }
 
 /*
- * Construct a packet with the specified contents.
+ * Construct a SSH-1 packet with the specified contents.
+ * (This all-at-once interface used to be the only one, but now SSH-1
+ * packets can also be constructed incrementally.)
  */
-static struct Packet *construct_packet(Ssh ssh, int pkttype,
-				       va_list ap1, va_list ap2)
+static struct Packet *construct_packet(Ssh ssh, int pkttype, va_list ap)
 {
-    unsigned char *p, *argp, argchar;
-    unsigned long argint;
-    int pktlen, argtype, arglen;
+    int argtype;
     Bignum bn;
     struct Packet *pkt;
 
-    pktlen = 0;
-    while ((argtype = va_arg(ap1, int)) != PKT_END) {
-	switch (argtype) {
-	  case PKT_INT:
-	    (void) va_arg(ap1, int);
-	    pktlen += 4;
-	    break;
-	  case PKT_CHAR:
-	    (void) va_arg(ap1, int);
-	    pktlen++;
-	    break;
-	  case PKT_DATA:
-	    (void) va_arg(ap1, unsigned char *);
-	    arglen = va_arg(ap1, int);
-	    pktlen += arglen;
-	    break;
-	  case PKT_STR:
-	    argp = va_arg(ap1, unsigned char *);
-	    arglen = strlen((char *)argp);
-	    pktlen += 4 + arglen;
-	    break;
-	  case PKT_BIGNUM:
-	    bn = va_arg(ap1, Bignum);
-	    pktlen += ssh1_bignum_length(bn);
-	    break;
-	  case PKTT_PASSWORD:
-	  case PKTT_DATA:
-	  case PKTT_OTHER:
-	    /* ignore this pass */
-	    break;
-	  default:
-	    assert(0);
-	}
-    }
-
-    pkt = s_wrpkt_start(pkttype, pktlen);
-    p = pkt->body;
+    pkt = ssh1_pkt_init(pkttype);
 
-    while ((argtype = va_arg(ap2, int)) != PKT_END) {
-	int offset = p - pkt->body, len = 0;
+    while ((argtype = va_arg(ap, int)) != PKT_END) {
+	unsigned char *argp, argchar;
+	unsigned long argint;
+	int arglen;
 	switch (argtype) {
 	  /* Actual fields in the packet */
 	  case PKT_INT:
-	    argint = va_arg(ap2, int);
-	    PUT_32BIT(p, argint);
-	    len = 4;
+	    argint = va_arg(ap, int);
+	    ssh_pkt_adduint32(pkt, argint);
 	    break;
 	  case PKT_CHAR:
-	    argchar = (unsigned char) va_arg(ap2, int);
-	    *p = argchar;
-	    len = 1;
+	    argchar = (unsigned char) va_arg(ap, int);
+	    ssh_pkt_addbyte(pkt, argchar);
 	    break;
 	  case PKT_DATA:
-	    argp = va_arg(ap2, unsigned char *);
-	    arglen = va_arg(ap2, int);
-	    memcpy(p, argp, arglen);
-	    len = arglen;
+	    argp = va_arg(ap, unsigned char *);
+	    arglen = va_arg(ap, int);
+	    ssh_pkt_adddata(pkt, argp, arglen);
 	    break;
 	  case PKT_STR:
-	    argp = va_arg(ap2, unsigned char *);
-	    arglen = strlen((char *)argp);
-	    PUT_32BIT(p, arglen);
-	    memcpy(p + 4, argp, arglen);
-	    len = arglen + 4;
+	    argp = va_arg(ap, unsigned char *);
+	    ssh_pkt_addstring(pkt, argp);
 	    break;
 	  case PKT_BIGNUM:
-	    bn = va_arg(ap2, Bignum);
-	    len = ssh1_write_bignum(p, bn);
+	    bn = va_arg(ap, Bignum);
+	    ssh1_pkt_addmp(pkt, bn);
 	    break;
 	  /* Tokens for modifications to packet logging */
 	  case PKTT_PASSWORD:
@@ -1458,16 +1516,6 @@ static struct Packet *construct_packet(Ssh ssh, int pkttype,
 	    end_log_omission(ssh, pkt);
 	    break;
 	}
-	p += len;
-	/* Deal with logfile omission, if required. */
-	if (len && (pkt->logmode != PKTLOG_EMIT)) {
-	    pkt->nblanks++;
-	    pkt->blanks = sresize(pkt->blanks, pkt->nblanks,
-				  struct logblank_t);
-	    pkt->blanks[pkt->nblanks-1].offset = offset;
-	    pkt->blanks[pkt->nblanks-1].len    = len;
-	    pkt->blanks[pkt->nblanks-1].type   = pkt->logmode;
-	}
     }
 
     return pkt;
@@ -1476,27 +1524,21 @@ static struct Packet *construct_packet(Ssh ssh, int pkttype,
 static void send_packet(Ssh ssh, int pkttype, ...)
 {
     struct Packet *pkt;
-    va_list ap1, ap2;
-    va_start(ap1, pkttype);
-    va_start(ap2, pkttype);
-    pkt = construct_packet(ssh, pkttype, ap1, ap2);
-    va_end(ap2);
-    va_end(ap1);
+    va_list ap;
+    va_start(ap, pkttype);
+    pkt = construct_packet(ssh, pkttype, ap);
+    va_end(ap);
     s_wrpkt(ssh, pkt);
-    ssh_free_packet(pkt);
 }
 
 static void defer_packet(Ssh ssh, int pkttype, ...)
 {
     struct Packet *pkt;
-    va_list ap1, ap2;
-    va_start(ap1, pkttype);
-    va_start(ap2, pkttype);
-    pkt = construct_packet(ssh, pkttype, ap1, ap2);
-    va_end(ap2);
-    va_end(ap1);
+    va_list ap;
+    va_start(ap, pkttype);
+    pkt = construct_packet(ssh, pkttype, ap);
+    va_end(ap);
     s_wrpkt_defer(ssh, pkt);
-    ssh_free_packet(pkt);
 }
 
 static int ssh_versioncmp(char *a, char *b)
@@ -1521,95 +1563,98 @@ static int ssh_versioncmp(char *a, char *b)
 
 /*
  * Utility routines for putting an SSH-protocol `string' and
- * `uint32' into a SHA state.
+ * `uint32' into a hash state.
  */
-#include <stdio.h>
-static void sha_string(SHA_State * s, void *str, int len)
+static void hash_string(const struct ssh_hash *h, void *s, void *str, int len)
 {
     unsigned char lenblk[4];
     PUT_32BIT(lenblk, len);
-    SHA_Bytes(s, lenblk, 4);
-    SHA_Bytes(s, str, len);
+    h->bytes(s, lenblk, 4);
+    h->bytes(s, str, len);
 }
 
-static void sha_uint32(SHA_State * s, unsigned i)
+static void hash_uint32(const struct ssh_hash *h, void *s, unsigned i)
 {
     unsigned char intblk[4];
     PUT_32BIT(intblk, i);
-    SHA_Bytes(s, intblk, 4);
+    h->bytes(s, intblk, 4);
 }
 
 /*
- * SSH2 packet construction functions.
+ * Packet construction functions. Mostly shared between SSH-1 and SSH-2.
  */
-static void ssh2_pkt_ensure(struct Packet *pkt, int length)
+static void ssh_pkt_ensure(struct Packet *pkt, int length)
 {
     if (pkt->maxlen < length) {
+	unsigned char *body = pkt->body;
+	int offset = body ? pkt->data - body : 0;
 	pkt->maxlen = length + 256;
 	pkt->data = sresize(pkt->data, pkt->maxlen + APIEXTRA, unsigned char);
+	if (body) pkt->body = pkt->data + offset;
     }
 }
-static void ssh2_pkt_adddata(struct Packet *pkt, void *data, int len)
+static void ssh_pkt_adddata(struct Packet *pkt, void *data, int len)
 {
     if (pkt->logmode != PKTLOG_EMIT) {
 	pkt->nblanks++;
 	pkt->blanks = sresize(pkt->blanks, pkt->nblanks, struct logblank_t);
-	pkt->blanks[pkt->nblanks-1].offset = pkt->length - 6;
+	assert(pkt->body);
+	pkt->blanks[pkt->nblanks-1].offset = pkt->length -
+					     (pkt->body - pkt->data);
 	pkt->blanks[pkt->nblanks-1].len = len;
 	pkt->blanks[pkt->nblanks-1].type = pkt->logmode;
     }
     pkt->length += len;
-    ssh2_pkt_ensure(pkt, pkt->length);
+    ssh_pkt_ensure(pkt, pkt->length);
     memcpy(pkt->data + pkt->length - len, data, len);
 }
-static void ssh2_pkt_addbyte(struct Packet *pkt, unsigned char byte)
+static void ssh_pkt_addbyte(struct Packet *pkt, unsigned char byte)
 {
-    ssh2_pkt_adddata(pkt, &byte, 1);
-}
-static struct Packet *ssh2_pkt_init(int pkt_type)
-{
-    struct Packet *pkt = ssh_new_packet();
-    pkt->length = 5;
-    ssh2_pkt_addbyte(pkt, (unsigned char) pkt_type);
-    return pkt;
+    ssh_pkt_adddata(pkt, &byte, 1);
 }
 static void ssh2_pkt_addbool(struct Packet *pkt, unsigned char value)
 {
-    ssh2_pkt_adddata(pkt, &value, 1);
+    ssh_pkt_adddata(pkt, &value, 1);
 }
-static void ssh2_pkt_adduint32(struct Packet *pkt, unsigned long value)
+static void ssh_pkt_adduint32(struct Packet *pkt, unsigned long value)
 {
     unsigned char x[4];
     PUT_32BIT(x, value);
-    ssh2_pkt_adddata(pkt, x, 4);
+    ssh_pkt_adddata(pkt, x, 4);
 }
-static void ssh2_pkt_addstring_start(struct Packet *pkt)
+static void ssh_pkt_addstring_start(struct Packet *pkt)
 {
-    ssh2_pkt_adduint32(pkt, 0);
+    ssh_pkt_adduint32(pkt, 0);
     pkt->savedpos = pkt->length;
 }
-static void ssh2_pkt_addstring_str(struct Packet *pkt, char *data)
+static void ssh_pkt_addstring_str(struct Packet *pkt, char *data)
 {
-    ssh2_pkt_adddata(pkt, data, strlen(data));
+    ssh_pkt_adddata(pkt, data, strlen(data));
     PUT_32BIT(pkt->data + pkt->savedpos - 4, pkt->length - pkt->savedpos);
 }
-static void ssh2_pkt_addstring_data(struct Packet *pkt, char *data, int len)
+static void ssh_pkt_addstring_data(struct Packet *pkt, char *data, int len)
 {
-    ssh2_pkt_adddata(pkt, data, len);
+    ssh_pkt_adddata(pkt, data, len);
     PUT_32BIT(pkt->data + pkt->savedpos - 4, pkt->length - pkt->savedpos);
 }
-static void ssh2_pkt_addstring(struct Packet *pkt, char *data)
+static void ssh_pkt_addstring(struct Packet *pkt, char *data)
 {
-    ssh2_pkt_addstring_start(pkt);
-    ssh2_pkt_addstring_str(pkt, data);
+    ssh_pkt_addstring_start(pkt);
+    ssh_pkt_addstring_str(pkt, data);
+}
+static void ssh1_pkt_addmp(struct Packet *pkt, Bignum b)
+{
+    int len = ssh1_bignum_length(b);
+    unsigned char *data = snewn(len, char);
+    (void) ssh1_write_bignum(data, b);
+    ssh_pkt_adddata(pkt, data, len);
+    sfree(data);
 }
 static unsigned char *ssh2_mpint_fmt(Bignum b, int *len)
 {
     unsigned char *p;
     int i, n = (bignum_bitcount(b) + 7) / 8;
     p = snewn(n + 1, unsigned char);
-    if (!p)
-	fatalbox("out of memory");
     p[0] = 0;
     for (i = 1; i <= n; i++)
 	p[i] = bignum_byte(b, n - i);
@@ -1625,13 +1670,42 @@ static void ssh2_pkt_addmp(struct Packet *pkt, Bignum b)
     unsigned char *p;
     int len;
     p = ssh2_mpint_fmt(b, &len);
-    ssh2_pkt_addstring_start(pkt);
-    ssh2_pkt_addstring_data(pkt, (char *)p, len);
+    ssh_pkt_addstring_start(pkt);
+    ssh_pkt_addstring_data(pkt, (char *)p, len);
     sfree(p);
 }
 
+static struct Packet *ssh1_pkt_init(int pkt_type)
+{
+    struct Packet *pkt = ssh_new_packet();
+    pkt->length = 4 + 8;	    /* space for length + max padding */
+    ssh_pkt_addbyte(pkt, pkt_type);
+    pkt->body = pkt->data + pkt->length;
+    return pkt;
+}
+
+/* For legacy code (SSH-1 and -2 packet construction used to be separate) */
+#define ssh2_pkt_ensure(pkt, length) ssh_pkt_ensure(pkt, length)
+#define ssh2_pkt_adddata(pkt, data, len) ssh_pkt_adddata(pkt, data, len)
+#define ssh2_pkt_addbyte(pkt, byte) ssh_pkt_addbyte(pkt, byte)
+#define ssh2_pkt_adduint32(pkt, value) ssh_pkt_adduint32(pkt, value)
+#define ssh2_pkt_addstring_start(pkt) ssh_pkt_addstring_start(pkt)
+#define ssh2_pkt_addstring_str(pkt, data) ssh_pkt_addstring_str(pkt, data)
+#define ssh2_pkt_addstring_data(pkt, data, len) ssh_pkt_addstring_data(pkt, data, len)
+#define ssh2_pkt_addstring(pkt, data) ssh_pkt_addstring(pkt, data)
+
+static struct Packet *ssh2_pkt_init(int pkt_type)
+{
+    struct Packet *pkt = ssh_new_packet();
+    pkt->length = 5;
+    pkt->forcepad = 0;
+    ssh_pkt_addbyte(pkt, (unsigned char) pkt_type);
+    pkt->body = pkt->data + pkt->length;
+    return pkt;
+}
+
 /*
- * Construct an SSH2 final-form packet: compress it, encrypt it,
+ * Construct an SSH-2 final-form packet: compress it, encrypt it,
  * put the MAC on it. Final packet, ready to be sent, is stored in
  * pkt->data. Total length is returned.
  */
@@ -1642,7 +1716,7 @@ static int ssh2_pkt_construct(Ssh ssh, struct Packet *pkt)
     if (ssh->logctx)
 	log_packet(ssh->logctx, PKT_OUTGOING, pkt->data[5],
 		   ssh2_pkt_type(ssh->pkt_ctx, pkt->data[5]),
-		   pkt->data + 6, pkt->length - 6,
+		   pkt->body, pkt->length - (pkt->body - pkt->data),
 		   pkt->nblanks, pkt->blanks);
     sfree(pkt->blanks); pkt->blanks = NULL;
     pkt->nblanks = 0;
@@ -1666,12 +1740,17 @@ static int ssh2_pkt_construct(Ssh ssh, struct Packet *pkt)
     /*
      * Add padding. At least four bytes, and must also bring total
      * length (minus MAC) up to a multiple of the block size.
+     * If pkt->forcepad is set, make sure the packet is at least that size
+     * after padding.
      */
     cipherblk = ssh->cscipher ? ssh->cscipher->blksize : 8;  /* block size */
     cipherblk = cipherblk < 8 ? 8 : cipherblk;	/* or 8 if blksize < 8 */
     padding = 4;
+    if (pkt->length + padding < pkt->forcepad)
+	padding = pkt->forcepad - pkt->length;
     padding +=
 	(cipherblk - (pkt->length + padding) % cipherblk) % cipherblk;
+    assert(padding <= 255);
     maclen = ssh->csmac ? ssh->csmac->len : 0;
     ssh2_pkt_ensure(pkt, pkt->length + padding + maclen);
     pkt->data[4] = padding;
@@ -1721,15 +1800,32 @@ static int ssh2_pkt_construct(Ssh ssh, struct Packet *pkt)
  * ssh2_pkt_send() or ssh2_pkt_defer() either go straight to one of
  * these or get queued, and then when the queue is later emptied
  * the packets are all passed to defer_noqueue().
+ *
+ * When using a CBC-mode cipher, it's necessary to ensure that an
+ * attacker can't provide data to be encrypted using an IV that they
+ * know.  We ensure this by prefixing each packet that might contain
+ * user data with an SSH_MSG_IGNORE.  This is done using the deferral
+ * mechanism, so in this case send_noqueue() ends up redirecting to
+ * defer_noqueue().  If you don't like this inefficiency, don't use
+ * CBC.
  */
 
+static void ssh2_pkt_defer_noqueue(Ssh, struct Packet *, int);
+static void ssh_pkt_defersend(Ssh);
+
 /*
- * Send an SSH2 packet immediately, without queuing or deferring.
+ * Send an SSH-2 packet immediately, without queuing or deferring.
  */
 static void ssh2_pkt_send_noqueue(Ssh ssh, struct Packet *pkt)
 {
     int len;
     int backlog;
+    if (ssh->cscipher != NULL && (ssh->cscipher->flags & SSH_CIPHER_IS_CBC)) {
+	/* We need to send two packets, so use the deferral mechanism. */
+	ssh2_pkt_defer_noqueue(ssh, pkt, FALSE);
+	ssh_pkt_defersend(ssh);
+	return;
+    }
     len = ssh2_pkt_construct(ssh, pkt);
     backlog = sk_write(ssh->s, (char *)pkt->data, len);
     if (backlog > SSH_MAX_BACKLOG)
@@ -1745,11 +1841,21 @@ static void ssh2_pkt_send_noqueue(Ssh ssh, struct Packet *pkt)
 }
 
 /*
- * Defer an SSH2 packet.
+ * Defer an SSH-2 packet.
  */
-static void ssh2_pkt_defer_noqueue(Ssh ssh, struct Packet *pkt)
+static void ssh2_pkt_defer_noqueue(Ssh ssh, struct Packet *pkt, int noignore)
 {
-    int len = ssh2_pkt_construct(ssh, pkt);
+    int len;
+    if (ssh->cscipher != NULL && (ssh->cscipher->flags & SSH_CIPHER_IS_CBC) &&
+	ssh->deferred_len == 0 && !noignore) {
+	/*
+	 * Interpose an SSH_MSG_IGNORE to ensure that user data don't
+	 * get encrypted with a known IV.
+	 */
+	struct Packet *ipkt = ssh2_pkt_init(SSH2_MSG_IGNORE);
+	ssh2_pkt_defer_noqueue(ssh, ipkt, TRUE);
+    }
+    len = ssh2_pkt_construct(ssh, pkt);
     if (ssh->deferred_len + len > ssh->deferred_size) {
 	ssh->deferred_size = ssh->deferred_len + len + 128;
 	ssh->deferred_send_data = sresize(ssh->deferred_send_data,
@@ -1763,7 +1869,7 @@ static void ssh2_pkt_defer_noqueue(Ssh ssh, struct Packet *pkt)
 }
 
 /*
- * Queue an SSH2 packet.
+ * Queue an SSH-2 packet.
  */
 static void ssh2_pkt_queue(Ssh ssh, struct Packet *pkt)
 {
@@ -1789,6 +1895,7 @@ static void ssh2_pkt_send(Ssh ssh, struct Packet *pkt)
 	ssh2_pkt_send_noqueue(ssh, pkt);
 }
 
+#if 0 /* disused */
 /*
  * Either queue or defer a packet, depending on whether queueing is
  * set.
@@ -1798,12 +1905,13 @@ static void ssh2_pkt_defer(Ssh ssh, struct Packet *pkt)
     if (ssh->queueing)
 	ssh2_pkt_queue(ssh, pkt);
     else
-	ssh2_pkt_defer_noqueue(ssh, pkt);
+	ssh2_pkt_defer_noqueue(ssh, pkt, FALSE);
 }
+#endif
 
 /*
  * Send the whole deferred data block constructed by
- * ssh2_pkt_defer() or SSH1's defer_packet().
+ * ssh2_pkt_defer() or SSH-1's defer_packet().
  * 
  * The expected use of the defer mechanism is that you call
  * ssh2_pkt_defer() a few times, then call ssh_pkt_defersend(). If
@@ -1834,7 +1942,7 @@ static void ssh_pkt_defersend(Ssh ssh)
 }
 
 /*
- * Send all queued SSH2 packets. We send them by means of
+ * Send all queued SSH-2 packets. We send them by means of
  * ssh2_pkt_defer_noqueue(), in case they included a pair of
  * packets that needed to be lumped together.
  */
@@ -1845,7 +1953,7 @@ static void ssh2_pkt_queuesend(Ssh ssh)
     assert(!ssh->queueing);
 
     for (i = 0; i < ssh->queuelen; i++)
-	ssh2_pkt_defer_noqueue(ssh, ssh->queue[i]);
+	ssh2_pkt_defer_noqueue(ssh, ssh->queue[i], FALSE);
     ssh->queuelen = 0;
 
     ssh_pkt_defersend(ssh);
@@ -1865,17 +1973,17 @@ void bndebug(char *string, Bignum b)
 }
 #endif
 
-static void sha_mpint(SHA_State * s, Bignum b)
+static void hash_mpint(const struct ssh_hash *h, void *s, Bignum b)
 {
     unsigned char *p;
     int len;
     p = ssh2_mpint_fmt(b, &len);
-    sha_string(s, p, len);
+    hash_string(h, s, p, len);
     sfree(p);
 }
 
 /*
- * Packet decode functions for both SSH1 and SSH2.
+ * Packet decode functions for both SSH-1 and SSH-2.
  */
 static unsigned long ssh_pkt_getuint32(struct Packet *pkt)
 {
@@ -1966,7 +2074,7 @@ static Bignum ssh2_pkt_getmp(struct Packet *pkt)
 }
 
 /*
- * Helper function to add an SSH2 signature blob to a packet.
+ * Helper function to add an SSH-2 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
@@ -2062,7 +2170,7 @@ static void ssh_detect_bugs(Ssh ssh, char *vstring)
 	 * sniffing.
 	 */
 	ssh->remote_bugs |= BUG_CHOKES_ON_SSH1_IGNORE;
-	logevent("We believe remote version has SSH1 ignore bug");
+	logevent("We believe remote version has SSH-1 ignore bug");
     }
 
     if (ssh->cfg.sshbug_plainpw1 == FORCE_ON ||
@@ -2074,7 +2182,7 @@ static void ssh_detect_bugs(Ssh ssh, char *vstring)
 	 * the password.
 	 */
 	ssh->remote_bugs |= BUG_NEEDS_SSH1_PLAIN_PASSWORD;
-	logevent("We believe remote version needs a plain SSH1 password");
+	logevent("We believe remote version needs a plain SSH-1 password");
     }
 
     if (ssh->cfg.sshbug_rsa1 == FORCE_ON ||
@@ -2086,7 +2194,7 @@ static void ssh_detect_bugs(Ssh ssh, char *vstring)
 	 * an AUTH_RSA message.
 	 */
 	ssh->remote_bugs |= BUG_CHOKES_ON_RSA;
-	logevent("We believe remote version can't handle RSA authentication");
+	logevent("We believe remote version can't handle SSH-1 RSA authentication");
     }
 
     if (ssh->cfg.sshbug_hmac2 == FORCE_ON ||
@@ -2099,7 +2207,7 @@ static void ssh_detect_bugs(Ssh ssh, char *vstring)
 	 * These versions have the HMAC bug.
 	 */
 	ssh->remote_bugs |= BUG_SSH2_HMAC;
-	logevent("We believe remote version has SSH2 HMAC bug");
+	logevent("We believe remote version has SSH-2 HMAC bug");
     }
 
     if (ssh->cfg.sshbug_derivekey2 == FORCE_ON ||
@@ -2112,7 +2220,7 @@ static void ssh_detect_bugs(Ssh ssh, char *vstring)
 	 * generate the keys).
 	 */
 	ssh->remote_bugs |= BUG_SSH2_DERIVEKEY;
-	logevent("We believe remote version has SSH2 key-derivation bug");
+	logevent("We believe remote version has SSH-2 key-derivation bug");
     }
 
     if (ssh->cfg.sshbug_rsapad2 == FORCE_ON ||
@@ -2120,32 +2228,37 @@ static void ssh_detect_bugs(Ssh ssh, char *vstring)
 	 (wc_match("OpenSSH_2.[5-9]*", imp) ||
 	  wc_match("OpenSSH_3.[0-2]*", imp)))) {
 	/*
-	 * These versions have the SSH2 RSA padding bug.
+	 * These versions have the SSH-2 RSA padding bug.
 	 */
 	ssh->remote_bugs |= BUG_SSH2_RSA_PADDING;
-	logevent("We believe remote version has SSH2 RSA padding bug");
+	logevent("We believe remote version has SSH-2 RSA padding bug");
     }
 
     if (ssh->cfg.sshbug_pksessid2 == FORCE_ON ||
 	(ssh->cfg.sshbug_pksessid2 == AUTO &&
 	 wc_match("OpenSSH_2.[0-2]*", imp))) {
 	/*
-	 * These versions have the SSH2 session-ID bug in
+	 * These versions have the SSH-2 session-ID bug in
 	 * public-key authentication.
 	 */
 	ssh->remote_bugs |= BUG_SSH2_PK_SESSIONID;
-	logevent("We believe remote version has SSH2 public-key-session-ID bug");
+	logevent("We believe remote version has SSH-2 public-key-session-ID bug");
     }
 
     if (ssh->cfg.sshbug_rekey2 == FORCE_ON ||
 	(ssh->cfg.sshbug_rekey2 == AUTO &&
-	 (wc_match("Sun_SSH_1.0", imp) ||
-	  wc_match("Sun_SSH_1.0.1", imp)))) {
+	 (wc_match("DigiSSH_2.0", imp) ||
+	  wc_match("OpenSSH_2.[0-4]*", imp) ||
+	  wc_match("OpenSSH_2.5.[0-3]*", imp) ||
+	  wc_match("Sun_SSH_1.0", imp) ||
+	  wc_match("Sun_SSH_1.0.1", imp) ||
+	  /* All versions <= 1.2.6 (they changed their format in 1.2.7) */
+	  wc_match("WeOnlyDo-*", imp)))) {
 	/*
-	 * These versions have the SSH2 ignore-rekey bug.
+	 * These versions have the SSH-2 rekey bug.
 	 */
 	ssh->remote_bugs |= BUG_SSH2_REKEY;
-	logevent("We believe remote version has SSH2 ignore-rekey bug");
+	logevent("We believe remote version has SSH-2 rekey bug");
     }
 }
 
@@ -2186,23 +2299,20 @@ static int do_ssh_init(Ssh ssh, unsigned char c)
 
     crBegin(ssh->do_ssh_init_crstate);
 
-    /* Search for the string "SSH-" in the input. */
-    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')
-	    s->i = transS[s->i];
-	else if (c == 'H')
-	    s->i = transH[s->i];
-	else if (c == '-')
-	    s->i = transminus[s->i];
-	else
-	    s->i = 0;
-	if (s->i < 0)
-	    break;
-	crReturn(1);		       /* get another character */
+    /* Search for a line beginning with the string "SSH-" in the input. */
+    for (;;) {
+	if (c != 'S') goto no;
+	crReturn(1);
+	if (c != 'S') goto no;
+	crReturn(1);
+	if (c != 'H') goto no;
+	crReturn(1);
+	if (c != '-') goto no;
+	break;
+      no:
+	while (c != '\012')
+	    crReturn(1);
+	crReturn(1);
     }
 
     s->vstrsize = 16;
@@ -2232,13 +2342,7 @@ static int do_ssh_init(Ssh ssh, unsigned char c)
 
     s->vstring[s->vslen] = 0;
     s->vstring[strcspn(s->vstring, "\015\012")] = '\0';/* remove EOL chars */
-    {
-	char *vlog;
-	vlog = snewn(20 + s->vslen, char);
-	sprintf(vlog, "Server version: %s", s->vstring);
-	logevent(vlog);
-	sfree(vlog);
-    }
+    logeventf(ssh, "Server version: %s", s->vstring);
     ssh_detect_bugs(ssh, s->vstring);
 
     /*
@@ -2282,24 +2386,28 @@ static int do_ssh_init(Ssh ssh, unsigned char c)
         ssh_fix_verstring(verstring);
 
         if (ssh->version == 2) {
+	    size_t len;
             /*
              * Hash our version string and their version string.
              */
-            SHA_Init(&ssh->exhashbase);
-            sha_string(&ssh->exhashbase, verstring,
-                       strcspn(verstring, "\015\012"));
-            sha_string(&ssh->exhashbase, s->vstring,
-                       strcspn(s->vstring, "\015\012"));
-
+	    len = strcspn(verstring, "\015\012");
+	    ssh->v_c = snewn(len + 1, char);
+	    memcpy(ssh->v_c, verstring, len);
+	    ssh->v_c[len] = 0;
+	    len = strcspn(s->vstring, "\015\012");
+	    ssh->v_s = snewn(len + 1, char);
+	    memcpy(ssh->v_s, s->vstring, len);
+	    ssh->v_s[len] = 0;
+	    
             /*
-             * Initialise SSHv2 protocol.
+             * Initialise SSH-2 protocol.
              */
             ssh->protocol = ssh2_protocol;
             ssh2_protocol_setup(ssh);
             ssh->s_rdpkt = ssh2_rdpkt;
         } else {
             /*
-             * Initialise SSHv1 protocol.
+             * Initialise SSH-1 protocol.
              */
             ssh->protocol = ssh1_protocol;
             ssh1_protocol_setup(ssh);
@@ -2309,6 +2417,8 @@ static int do_ssh_init(Ssh ssh, unsigned char c)
                   strcspn(verstring, "\015\012"), verstring);
 	sk_write(ssh->s, verstring, strlen(verstring));
         sfree(verstring);
+	if (ssh->version == 2)
+	    do_ssh2_transport(ssh, NULL, -1, NULL);
     }
 
     logeventf(ssh, "Using SSH protocol version %d", ssh->version);
@@ -2322,6 +2432,50 @@ static int do_ssh_init(Ssh ssh, unsigned char c)
     crFinish(0);
 }
 
+static void ssh_process_incoming_data(Ssh ssh,
+				      unsigned char **data, int *datalen)
+{
+    struct Packet *pktin = ssh->s_rdpkt(ssh, data, datalen);
+    if (pktin) {
+	ssh->protocol(ssh, NULL, 0, pktin);
+	ssh_free_packet(pktin);
+    }
+}
+
+static void ssh_queue_incoming_data(Ssh ssh,
+				    unsigned char **data, int *datalen)
+{
+    bufchain_add(&ssh->queued_incoming_data, *data, *datalen);
+    *data += *datalen;
+    *datalen = 0;
+}
+
+static void ssh_process_queued_incoming_data(Ssh ssh)
+{
+    void *vdata;
+    unsigned char *data;
+    int len, origlen;
+
+    while (!ssh->frozen && bufchain_size(&ssh->queued_incoming_data)) {
+	bufchain_prefix(&ssh->queued_incoming_data, &vdata, &len);
+	data = vdata;
+	origlen = len;
+
+	while (!ssh->frozen && len > 0)
+	    ssh_process_incoming_data(ssh, &data, &len);
+
+	if (origlen > len)
+	    bufchain_consume(&ssh->queued_incoming_data, origlen - len);
+    }
+}
+
+static void ssh_set_frozen(Ssh ssh, int frozen)
+{
+    if (ssh->s)
+	sk_set_frozen(ssh->s, frozen);
+    ssh->frozen = frozen;
+}
+
 static void ssh_gotdata(Ssh ssh, unsigned char *data, int datalen)
 {
     crBegin(ssh->ssh_gotdata_crstate);
@@ -2349,40 +2503,55 @@ static void ssh_gotdata(Ssh ssh, unsigned char *data, int datalen)
      * everything to s_rdpkt, and then pass the resulting packets
      * to the proper protocol handler.
      */
-    if (datalen == 0)
-	crReturnV;
+
     while (1) {
-	while (datalen > 0) {
-	    struct Packet *pktin = ssh->s_rdpkt(ssh, &data, &datalen);
-	    if (pktin) {
-		ssh->protocol(ssh, NULL, 0, pktin);
-		ssh_free_packet(pktin);
+	while (bufchain_size(&ssh->queued_incoming_data) > 0 || datalen > 0) {
+	    if (ssh->frozen) {
+		ssh_queue_incoming_data(ssh, &data, &datalen);
+		/* This uses up all data and cannot cause anything interesting
+		 * to happen; indeed, for anything to happen at all, we must
+		 * return, so break out. */
+		break;
+	    } else if (bufchain_size(&ssh->queued_incoming_data) > 0) {
+		/* This uses up some or all data, and may freeze the
+		 * session. */
+		ssh_process_queued_incoming_data(ssh);
+	    } else {
+		/* This uses up some or all data, and may freeze the
+		 * session. */
+		ssh_process_incoming_data(ssh, &data, &datalen);
 	    }
+	    /* FIXME this is probably EBW. */
 	    if (ssh->state == SSH_STATE_CLOSED)
 		return;
 	}
+	/* We're out of data. Go and get some more. */
 	crReturnV;
     }
     crFinishV;
 }
 
-static void ssh_do_close(Ssh ssh)
+static int ssh_do_close(Ssh ssh, int notify_exit)
 {
-    int i;
+    int ret = 0;
     struct ssh_channel *c;
 
     ssh->state = SSH_STATE_CLOSED;
+    expire_timer_context(ssh);
     if (ssh->s) {
         sk_close(ssh->s);
         ssh->s = NULL;
-	notify_remote_exit(ssh->frontend);
+        if (notify_exit)
+            notify_remote_exit(ssh->frontend);
+        else
+            ret = 1;
     }
     /*
-     * Now we must shut down any port and X forwardings going
+     * Now we must shut down any port- and X-forwarded channels going
      * through this connection.
      */
     if (ssh->channels) {
-	for (i = 0; NULL != (c = index234(ssh->channels, i)); i++) {
+	while (NULL != (c = index234(ssh->channels, 0))) {
 	    switch (c->type) {
 	      case CHAN_X11:
 		x11_close(c->u.x11.s);
@@ -2391,26 +2560,67 @@ static void ssh_do_close(Ssh ssh)
 		pfd_close(c->u.pfd.s);
 		break;
 	    }
-	    del234(ssh->channels, c);
+	    del234(ssh->channels, c); /* moving next one to index 0 */
 	    if (ssh->version == 2)
 		bufchain_clear(&c->v.v2.outbuffer);
 	    sfree(c);
 	}
     }
+    /*
+     * Go through port-forwardings, and close any associated
+     * listening sockets.
+     */
+    if (ssh->portfwds) {
+	struct ssh_portfwd *pf;
+	while (NULL != (pf = index234(ssh->portfwds, 0))) {
+	    /* Dispose of any listening socket. */
+	    if (pf->local)
+		pfd_terminate(pf->local);
+	    del234(ssh->portfwds, pf); /* moving next one to index 0 */
+	    free_portfwd(pf);
+	}
+    }
+
+    return ret;
+}
+
+static void ssh_log(Plug plug, int type, SockAddr addr, int port,
+		    const char *error_msg, int error_code)
+{
+    Ssh ssh = (Ssh) plug;
+    char addrbuf[256], *msg;
+
+    sk_getaddr(addr, addrbuf, lenof(addrbuf));
+
+    if (type == 0)
+	msg = dupprintf("Connecting to %s port %d", addrbuf, port);
+    else
+	msg = dupprintf("Failed to connect to %s: %s", addrbuf, error_msg);
+
+    logevent(msg);
+    sfree(msg);
 }
 
 static int ssh_closing(Plug plug, const char *error_msg, int error_code,
 		       int calling_back)
 {
     Ssh ssh = (Ssh) plug;
-    ssh_do_close(ssh);
-    if (error_msg) {
-	/* A socket error has occurred. */
+    int need_notify = ssh_do_close(ssh, FALSE);
+
+    if (!error_msg) {
+	if (!ssh->close_expected)
+	    error_msg = "Server unexpectedly closed network connection";
+	else
+	    error_msg = "Server closed network connection";
+    }
+
+    if (need_notify)
+        notify_remote_exit(ssh->frontend);
+
+    if (error_msg)
 	logevent(error_msg);
+    if (!ssh->close_expected || !ssh->clean_exit)
 	connection_fatal(ssh->frontend, "%s", error_msg);
-    } else {
-	/* Otherwise, the remote side closed the connection normally. */
-    }
     return 0;
 }
 
@@ -2419,7 +2629,7 @@ static int ssh_receive(Plug plug, int urgent, char *data, int len)
     Ssh ssh = (Ssh) plug;
     ssh_gotdata(ssh, (unsigned char *)data, len);
     if (ssh->state == SSH_STATE_CLOSED) {
-	ssh_do_close(ssh);
+	ssh_do_close(ssh, TRUE);
 	return 0;
     }
     return 1;
@@ -2446,6 +2656,7 @@ static const char *connect_to_host(Ssh ssh, char *host, int port,
 				   char **realhost, int nodelay, int keepalive)
 {
     static const struct plug_function_table fn_table = {
+	ssh_log,
 	ssh_closing,
 	ssh_receive,
 	ssh_sent,
@@ -2456,8 +2667,6 @@ static const char *connect_to_host(Ssh ssh, char *host, int port,
     const char *err;
 
     ssh->savedhost = snewn(1 + strlen(host), char);
-    if (!ssh->savedhost)
-	fatalbox("Out of memory");
     strcpy(ssh->savedhost, host);
 
     if (port < 0)
@@ -2480,11 +2689,6 @@ static const char *connect_to_host(Ssh ssh, char *host, int port,
     /*
      * Open socket.
      */
-    {
-	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, keepalive, (Plug) ssh, &ssh->cfg);
@@ -2506,9 +2710,9 @@ static void ssh1_throttle(Ssh ssh, int adjust)
     ssh->v1_throttle_count += adjust;
     assert(ssh->v1_throttle_count >= 0);
     if (ssh->v1_throttle_count && !old_count) {
-	sk_set_frozen(ssh->s, 1);
+	ssh_set_frozen(ssh, 1);
     } else if (!ssh->v1_throttle_count && old_count) {
-	sk_set_frozen(ssh->s, 0);
+	ssh_set_frozen(ssh, 0);
     }
 }
 
@@ -2549,7 +2753,7 @@ static void ssh_throttle_all(Ssh ssh, int enable, int bufsize)
 
 /*
  * Username and password input, abstracted off into routines
- * reusable in several places - even between SSH1 and SSH2.
+ * reusable in several places - even between SSH-1 and SSH-2.
  */
 
 /* Set up a username or password input loop on a given buffer. */
@@ -2632,6 +2836,24 @@ static void ssh_agent_callback(void *sshv, void *reply, int replylen)
 	do_ssh2_authconn(ssh, NULL, -1, NULL);
 }
 
+static void ssh_dialog_callback(void *sshv, int ret)
+{
+    Ssh ssh = (Ssh) sshv;
+
+    ssh->user_response = ret;
+
+    if (ssh->version == 1)
+	do_ssh1_login(ssh, NULL, -1, NULL);
+    else
+	do_ssh2_transport(ssh, NULL, -1, NULL);
+
+    /*
+     * This may have unfrozen the SSH connection, so do a
+     * queued-data run.
+     */
+    ssh_process_queued_incoming_data(ssh);
+}
+
 static void ssh_agentf_callback(void *cv, void *reply, int replylen)
 {
     struct ssh_channel *c = (struct ssh_channel *)cv;
@@ -2660,6 +2882,39 @@ static void ssh_agentf_callback(void *cv, void *reply, int replylen)
 }
 
 /*
+ * Client-initiated disconnection. Send a DISCONNECT if `wire_reason'
+ * non-NULL, otherwise just close the connection. `client_reason' == NULL
+ * => log `wire_reason'.
+ */
+static void ssh_disconnect(Ssh ssh, char *client_reason, char *wire_reason,
+			   int code, int clean_exit)
+{
+    char *error;
+    if (!client_reason)
+	client_reason = wire_reason;
+    if (client_reason)
+	error = dupprintf("Disconnected: %s", client_reason);
+    else
+	error = dupstr("Disconnected");
+    if (wire_reason) {
+	if (ssh->version == 1) {
+	    send_packet(ssh, SSH1_MSG_DISCONNECT, PKT_STR, wire_reason,
+			PKT_END);
+	} else if (ssh->version == 2) {
+	    struct Packet *pktout = ssh2_pkt_init(SSH2_MSG_DISCONNECT);
+	    ssh2_pkt_adduint32(pktout, code);
+	    ssh2_pkt_addstring(pktout, wire_reason);
+	    ssh2_pkt_addstring(pktout, "en");	/* language tag */
+	    ssh2_pkt_send_noqueue(ssh, pktout);
+	}
+    }
+    ssh->close_expected = TRUE;
+    ssh->clean_exit = clean_exit;
+    ssh_closing((Plug)ssh, error, 0, 0);
+    sfree(error);
+}
+
+/*
  * Handle the key exchange and user authentication phases.
  */
 static int do_ssh1_login(Ssh ssh, unsigned char *in, int inlen,
@@ -2693,6 +2948,7 @@ static int do_ssh1_login(Ssh ssh, unsigned char *in, int inlen,
 	Bignum challenge;
 	char *commentp;
 	int commentlen;
+        int dlgret;
     };
     crState(do_ssh1_login_state);
 
@@ -2710,14 +2966,14 @@ static int do_ssh1_login(Ssh ssh, unsigned char *in, int inlen,
 
     ptr = ssh_pkt_getdata(pktin, 8);
     if (!ptr) {
-	bombout(("SSH1 public key packet stopped before random cookie"));
+	bombout(("SSH-1 public key packet stopped before random cookie"));
 	crStop(0);
     }
     memcpy(cookie, ptr, 8);
 
     if (!ssh1_pkt_getrsakey(pktin, &servkey, &s->keystr1) ||
 	!ssh1_pkt_getrsakey(pktin, &hostkey, &s->keystr2)) {	
-	bombout(("Failed to read SSH1 public keys from public key packet"));
+	bombout(("Failed to read SSH-1 public keys from public key packet"));
 	crStop(0);
     }
 
@@ -2756,15 +3012,13 @@ static int do_ssh1_login(Ssh ssh, unsigned char *in, int inlen,
      */
     if (hostkey.bits > hostkey.bytes * 8 ||
 	servkey.bits > servkey.bytes * 8) {
-	bombout(("SSH1 public keys were badly formatted"));
+	bombout(("SSH-1 public keys were badly formatted"));
 	crStop(0);
     }
 
     s->len = (hostkey.bytes > servkey.bytes ? hostkey.bytes : servkey.bytes);
 
     s->rsabuf = snewn(s->len, unsigned char);
-    if (!s->rsabuf)
-	fatalbox("Out of memory");
 
     /*
      * Verify the host key.
@@ -2776,14 +3030,33 @@ static int do_ssh1_login(Ssh ssh, unsigned char *in, int inlen,
 	int len = rsastr_len(&hostkey);
 	char fingerprint[100];
 	char *keystr = snewn(len, char);
-	if (!keystr)
-	    fatalbox("Out of memory");
 	rsastr_fmt(keystr, &hostkey);
 	rsa_fingerprint(fingerprint, sizeof(fingerprint), &hostkey);
-	verify_ssh_host_key(ssh->frontend,
-			    ssh->savedhost, ssh->savedport, "rsa", keystr,
-			    fingerprint);
+
+        ssh_set_frozen(ssh, 1);
+	s->dlgret = verify_ssh_host_key(ssh->frontend,
+                                        ssh->savedhost, ssh->savedport,
+                                        "rsa", keystr, fingerprint,
+                                        ssh_dialog_callback, ssh);
 	sfree(keystr);
+        if (s->dlgret < 0) {
+            do {
+                crReturn(0);
+                if (pktin) {
+                    bombout(("Unexpected data from server while waiting"
+                             " for user host key response"));
+                    crStop(0);
+                }
+            } while (pktin || inlen > 0);
+            s->dlgret = ssh->user_response;
+        }
+        ssh_set_frozen(ssh, 0);
+
+        if (s->dlgret == 0) {
+	    ssh_disconnect(ssh, "User aborted at host key verification",
+			   NULL, 0, TRUE);
+	    crStop(0);
+        }
     }
 
     for (i = 0; i < 32; i++) {
@@ -2802,7 +3075,7 @@ static int do_ssh1_login(Ssh ssh, unsigned char *in, int inlen,
 	    ret = rsaencrypt(s->rsabuf, hostkey.bytes, &servkey);
     }
     if (!ret) {
-	bombout(("SSH1 public key encryptions failed due to bad formatting"));
+	bombout(("SSH-1 public key encryptions failed due to bad formatting"));
 	crStop(0);	
     }
 
@@ -2819,7 +3092,7 @@ static int do_ssh1_login(Ssh ssh, unsigned char *in, int inlen,
 		warn = 1;
 	    } else if (next_cipher == CIPHER_AES) {
 		/* XXX Probably don't need to mention this. */
-		logevent("AES not supported in SSH1, skipping");
+		logevent("AES not supported in SSH-1, skipping");
 	    } else {
 		switch (next_cipher) {
 		  case CIPHER_3DES:     s->cipher_type = SSH_CIPHER_3DES;
@@ -2835,7 +3108,7 @@ static int do_ssh1_login(Ssh ssh, unsigned char *in, int inlen,
 	}
 	if (!cipher_chosen) {
 	    if ((s->supported_ciphers_mask & (1 << SSH_CIPHER_3DES)) == 0)
-		bombout(("Server violates SSH 1 protocol by not "
+		bombout(("Server violates SSH-1 protocol by not "
 			 "supporting 3DES encryption"));
 	    else
 		/* shouldn't happen */
@@ -2845,9 +3118,26 @@ static int do_ssh1_login(Ssh ssh, unsigned char *in, int inlen,
 
 	/* Warn about chosen cipher if necessary. */
 	if (warn) {
-            sk_set_frozen(ssh->s, 1);
-	    askalg(ssh->frontend, "cipher", cipher_string);
-            sk_set_frozen(ssh->s, 0);
+            ssh_set_frozen(ssh, 1);
+	    s->dlgret = askalg(ssh->frontend, "cipher", cipher_string,
+			       ssh_dialog_callback, ssh);
+	    if (s->dlgret < 0) {
+		do {
+		    crReturn(0);
+		    if (pktin) {
+			bombout(("Unexpected data from server while waiting"
+				 " for user response"));
+			crStop(0);
+		    }
+		} while (pktin || inlen > 0);
+		s->dlgret = ssh->user_response;
+	    }
+            ssh_set_frozen(ssh, 0);
+	    if (s->dlgret == 0) {
+		ssh_disconnect(ssh, "User aborted at cipher warning", NULL,
+			       0, TRUE);
+		crStop(0);
+	    }
         }
     }
 
@@ -2919,8 +3209,7 @@ static int do_ssh1_login(Ssh ssh, unsigned char *in, int inlen,
 		     * get_line failed to get a username.
 		     * Terminate.
 		     */
-		    logevent("No username provided. Abandoning session.");
-                    ssh_closing((Plug)ssh, NULL, 0, 0);
+		    ssh_disconnect(ssh, "No username provided", NULL, 0, TRUE);
 		    crStop(1);
 		}
 	    } else {
@@ -3007,17 +3296,9 @@ static int do_ssh1_login(Ssh ssh, unsigned char *in, int inlen,
 		s->p = s->response + 5;
 		s->nkeys = GET_32BIT(s->p);
 		s->p += 4;
-		{
-		    char buf[64];
-		    sprintf(buf, "Pageant has %d SSH1 keys", s->nkeys);
-		    logevent(buf);
-		}
+		logeventf(ssh, "Pageant has %d SSH-1 keys", s->nkeys);
 		for (s->keyi = 0; s->keyi < s->nkeys; s->keyi++) {
-		    {
-			char buf[64];
-			sprintf(buf, "Trying Pageant key #%d", s->keyi);
-			logevent(buf);
-		    }
+		    logeventf(ssh, "Trying Pageant key #%d", s->keyi);
 		    if (s->publickey_blob &&
 			!memcmp(s->p, s->publickey_blob,
 				s->publickey_bloblen)) {
@@ -3175,6 +3456,7 @@ static int do_ssh1_login(Ssh ssh, unsigned char *in, int inlen,
 		    bombout(("TIS challenge packet was badly formed"));
 		    crStop(0);
 		}
+		c_write_str(ssh, "Using TIS authentication.\r\n");
 		logevent("Received TIS challenge");
 		if (challengelen > sizeof(s->prompt) - 1)
 		    challengelen = sizeof(s->prompt) - 1;/* prevent overrun */
@@ -3208,6 +3490,7 @@ static int do_ssh1_login(Ssh ssh, unsigned char *in, int inlen,
 		    bombout(("CryptoCard challenge packet was badly formed"));
 		    crStop(0);
 		}
+		c_write_str(ssh, "Using CryptoCard authentication.\r\n");
 		logevent("Received CryptoCard challenge");
 		if (challengelen > sizeof(s->prompt) - 1)
 		    challengelen = sizeof(s->prompt) - 1;/* prevent overrun */
@@ -3226,18 +3509,18 @@ static int do_ssh1_login(Ssh ssh, unsigned char *in, int inlen,
 	if (s->pwpkt_type == SSH1_CMSG_AUTH_RSA) {
 	    char *comment = NULL;
 	    int type;
-	    char msgbuf[256];
 	    if (flags & FLAG_VERBOSE)
 		c_write_str(ssh, "Trying public key authentication.\r\n");
 	    logeventf(ssh, "Trying public key \"%s\"",
 		      filename_to_str(&ssh->cfg.keyfile));
 	    type = key_type(&ssh->cfg.keyfile);
 	    if (type != SSH_KEYTYPE_SSH1) {
-		sprintf(msgbuf, "Key is of wrong type (%s)",
-			key_type_to_str(type));
-		logevent(msgbuf);
-		c_write_str(ssh, msgbuf);
+		char *msg = dupprintf("Key is of wrong type (%s)",
+				      key_type_to_str(type));
+		logevent(msg);
+		c_write_str(ssh, msg);
 		c_write_str(ssh, "\r\n");
+		sfree(msg);
 		s->tried_publickey = 1;
 		continue;
 	    }
@@ -3263,12 +3546,7 @@ static int do_ssh1_login(Ssh ssh, unsigned char *in, int inlen,
 		 * because one was supplied on the command line
 		 * which has already failed to work). Terminate.
 		 */
-		send_packet(ssh, SSH1_MSG_DISCONNECT,
-			    PKT_STR, "No more passwords available to try",
-			    PKT_END);
-		logevent("Unable to authenticate");
-		connection_fatal(ssh->frontend, "Unable to authenticate");
-                ssh_closing((Plug)ssh, NULL, 0, 0);
+		ssh_disconnect(ssh, NULL, "Unable to authenticate", 0, FALSE);
 		crStop(1);
 	    }
 	} else {
@@ -3519,20 +3797,18 @@ void sshfwd_close(struct ssh_channel *c)
 {
     Ssh ssh = c->ssh;
 
-    if (ssh->state != SSH_STATE_SESSION) {
-	assert(ssh->state == SSH_STATE_CLOSED);
+    if (ssh->state == SSH_STATE_CLOSED)
 	return;
-    }
 
     if (c && !c->closes) {
 	/*
-	 * If the channel's remoteid is -1, we have sent
+	 * If halfopen is true, 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 (!c->halfopen) {
 	    if (ssh->version == 1) {
 		send_packet(ssh, SSH1_MSG_CHANNEL_CLOSE, PKT_INT, c->remoteid,
 			    PKT_END);
@@ -3559,10 +3835,8 @@ int sshfwd_write(struct ssh_channel *c, char *buf, int len)
 {
     Ssh ssh = c->ssh;
 
-    if (ssh->state != SSH_STATE_SESSION) {
-	assert(ssh->state == SSH_STATE_CLOSED);
+    if (ssh->state == SSH_STATE_CLOSED)
 	return 0;
-    }
 
     if (ssh->version == 1) {
 	send_packet(ssh, SSH1_MSG_CHANNEL_DATA,
@@ -3571,7 +3845,7 @@ int sshfwd_write(struct ssh_channel *c, char *buf, int len)
 		    PKT_INT, len, PKT_DATA, buf, len,
 		    PKTT_OTHER, PKT_END);
 	/*
-	 * In SSH1 we can return 0 here - implying that forwarded
+	 * In SSH-1 we can return 0 here - implying that forwarded
 	 * connections are never individually throttled - because
 	 * the only circumstance that can cause throttling will be
 	 * the whole SSH connection backing up, in which case
@@ -3588,10 +3862,8 @@ void sshfwd_unthrottle(struct ssh_channel *c, int bufsize)
 {
     Ssh ssh = c->ssh;
 
-    if (ssh->state != SSH_STATE_SESSION) {
-	assert(ssh->state == SSH_STATE_CLOSED);
+    if (ssh->state == SSH_STATE_CLOSED)
 	return;
-    }
 
     if (ssh->version == 1) {
 	if (c->v.v1.throttling && bufsize < SSH1_BUFFER_LIMIT) {
@@ -3743,13 +4015,13 @@ static void ssh_setup_portfwd(Ssh ssh, const Config *cfg)
 		portfwd_strptr++;
 		sports[n] = '\0';
 		if (ssh->version == 1 && type == 'R') {
-		    logeventf(ssh, "SSH1 cannot handle remote source address "
+		    logeventf(ssh, "SSH-1 cannot handle remote source address "
 			      "spec \"%s\"; ignoring", sports);
 		} else
 		    strcpy(saddr, sports);
 		n = 0;
 	    }
-	    if (n < 255) sports[n++] = *portfwd_strptr++;
+	    if (n < lenof(sports)-1) sports[n++] = *portfwd_strptr++;
 	}
 	sports[n] = 0;
 	if (type != 'D') {
@@ -3757,14 +4029,14 @@ static void ssh_setup_portfwd(Ssh ssh, const Config *cfg)
 		portfwd_strptr++;
 	    n = 0;
 	    while (*portfwd_strptr && *portfwd_strptr != ':') {
-		if (n < 255) host[n++] = *portfwd_strptr++;
+		if (n < lenof(host)-1) host[n++] = *portfwd_strptr++;
 	    }
 	    host[n] = 0;
 	    if (*portfwd_strptr == ':')
 		portfwd_strptr++;
 	    n = 0;
 	    while (*portfwd_strptr) {
-		if (n < 255) dports[n++] = *portfwd_strptr++;
+		if (n < lenof(dports)-1) dports[n++] = *portfwd_strptr++;
 	    }
 	    dports[n] = 0;
 	    portfwd_strptr++;
@@ -3780,6 +4052,8 @@ static void ssh_setup_portfwd(Ssh ssh, const Config *cfg)
 	    }
 	} else {
 	    while (*portfwd_strptr) portfwd_strptr++;
+	    host[0] = 0;
+	    dports[0] = 0;
 	    dport = dserv = -1;
 	    portfwd_strptr++;	       /* eat the NUL and move to next one */
 	}
@@ -3862,7 +4136,7 @@ static void ssh_setup_portfwd(Ssh ssh, const Config *cfg)
 		if (ssh->version == 1) {
 		    /*
 		     * We cannot cancel listening ports on the
-		     * server side in SSH1! There's no message
+		     * server side in SSH-1! There's no message
 		     * to support it. Instead, we simply remove
 		     * the rportfwd record from the local end
 		     * so that any connections the server tries
@@ -3875,6 +4149,9 @@ static void ssh_setup_portfwd(Ssh ssh, const Config *cfg)
 		    if (epf->saddr) {
 			ssh2_pkt_addstring(pktout, epf->saddr);
 		    } else if (ssh->cfg.rport_acceptall) {
+			/* XXX: ssh->cfg.rport_acceptall may not represent
+			 * what was used to open the original connection,
+			 * since it's reconfigurable. */
 			ssh2_pkt_addstring(pktout, "0.0.0.0");
 		    } else {
 			ssh2_pkt_addstring(pktout, "127.0.0.1");
@@ -3921,7 +4198,7 @@ static void ssh_setup_portfwd(Ssh ssh, const Config *cfg)
 	    if (epf->type == 'L') {
 		const char *err = pfd_addforward(epf->daddr, epf->dport,
 						 epf->saddr, epf->sport,
-						 ssh, &ssh->cfg,
+						 ssh, cfg,
 						 &epf->local,
 						 epf->addressfamily);
 
@@ -3933,7 +4210,7 @@ static void ssh_setup_portfwd(Ssh ssh, const Config *cfg)
 	    } else if (epf->type == 'D') {
 		const char *err = pfd_addforward(NULL, -1,
 						 epf->saddr, epf->sport,
-						 ssh, &ssh->cfg,
+						 ssh, cfg,
 						 &epf->local,
 						 epf->addressfamily);
 
@@ -3989,7 +4266,7 @@ static void ssh_setup_portfwd(Ssh ssh, const Config *cfg)
 			ssh2_pkt_addbool(pktout, 1);/* want reply */
 			if (epf->saddr) {
 			    ssh2_pkt_addstring(pktout, epf->saddr);
-			} else if (ssh->cfg.rport_acceptall) {
+			} else if (cfg->rport_acceptall) {
 			    ssh2_pkt_addstring(pktout, "0.0.0.0");
 			} else {
 			    ssh2_pkt_addstring(pktout, "127.0.0.1");
@@ -4054,6 +4331,7 @@ static void ssh1_smsg_x11_open(Ssh ssh, struct Packet *pktin)
 	    logevent
 		("Opening X11 forward connection succeeded");
 	    c->remoteid = remoteid;
+	    c->halfopen = FALSE;
 	    c->localid = alloc_channel_id(ssh);
 	    c->closes = 0;
 	    c->v.v1.throttling = 0;
@@ -4082,6 +4360,7 @@ static void ssh1_smsg_agent_open(Ssh ssh, struct Packet *pktin)
 	c = snew(struct ssh_channel);
 	c->ssh = ssh;
 	c->remoteid = remoteid;
+	c->halfopen = FALSE;
 	c->localid = alloc_channel_id(ssh);
 	c->closes = 0;
 	c->v.v1.throttling = 0;
@@ -4102,7 +4381,7 @@ static void ssh1_msg_port_open(Ssh ssh, struct Packet *pktin)
     struct ssh_rportfwd pf, *pfp;
     int remoteid;
     int hostsize, port;
-    char *host, buf[1024];
+    char *host;
     const char *e;
     c = snew(struct ssh_channel);
     c->ssh = ssh;
@@ -4119,26 +4398,23 @@ static void ssh1_msg_port_open(Ssh ssh, struct Packet *pktin)
     pfp = find234(ssh->rportfwds, &pf, NULL);
 
     if (pfp == NULL) {
-	sprintf(buf, "Rejected remote port open request for %s:%d",
-		pf.dhost, port);
-	logevent(buf);
+	logeventf(ssh, "Rejected remote port open request for %s:%d",
+		  pf.dhost, port);
 	send_packet(ssh, SSH1_MSG_CHANNEL_OPEN_FAILURE,
 		    PKT_INT, remoteid, PKT_END);
     } else {
-	sprintf(buf, "Received remote port open request for %s:%d",
-		pf.dhost, port);
-	logevent(buf);
+	logeventf(ssh, "Received remote port open request for %s:%d",
+		  pf.dhost, port);
 	e = pfd_newconnect(&c->u.pfd.s, pf.dhost, port,
 			   c, &ssh->cfg, pfp->pfrec->addressfamily);
 	if (e != NULL) {
-	    char buf[256];
-	    sprintf(buf, "Port open failed: %s", e);
-	    logevent(buf);
+	    logeventf(ssh, "Port open failed: %s", e);
 	    sfree(c);
 	    send_packet(ssh, SSH1_MSG_CHANNEL_OPEN_FAILURE,
 			PKT_INT, remoteid, PKT_END);
 	} else {
 	    c->remoteid = remoteid;
+	    c->halfopen = FALSE;
 	    c->localid = alloc_channel_id(ssh);
 	    c->closes = 0;
 	    c->v.v1.throttling = 0;
@@ -4161,6 +4437,7 @@ static void ssh1_msg_channel_open_confirmation(Ssh ssh, struct Packet *pktin)
     c = find234(ssh->channels, &remoteid, ssh_channelfind);
     if (c && c->type == CHAN_SOCKDATA_DORMANT) {
 	c->remoteid = localid;
+	c->halfopen = FALSE;
 	c->type = CHAN_SOCKDATA;
 	c->v.v1.throttling = 0;
 	pfd_confirm(c->u.pfd.s);
@@ -4198,7 +4475,7 @@ static void ssh1_msg_channel_close(Ssh ssh, struct Packet *pktin)
     unsigned i = ssh_pkt_getuint32(pktin);
     struct ssh_channel *c;
     c = find234(ssh->channels, &i, ssh_channelfind);
-    if (c && ((int)c->remoteid) != -1) {
+    if (c && !c->halfopen) {
 	int closetype;
 	closetype =
 	    (pktin->type == SSH1_MSG_CHANNEL_CLOSE ? 1 : 2);
@@ -4240,7 +4517,7 @@ static void ssh1_msg_channel_data(Ssh ssh, struct Packet *pktin)
     /* Data sent down one of our channels. */
     int i = ssh_pkt_getuint32(pktin);
     char *p;
-    unsigned int len;
+    int len;
     struct ssh_channel *c;
 
     ssh_pkt_getstring(pktin, &p, &len);
@@ -4307,11 +4584,8 @@ static void ssh1_msg_channel_data(Ssh ssh, struct Packet *pktin)
 
 static void ssh1_smsg_exit_status(Ssh ssh, struct Packet *pktin)
 {
-    char buf[100];
     ssh->exitcode = ssh_pkt_getuint32(pktin);
-    sprintf(buf, "Server sent command exit status %d",
-	    ssh->exitcode);
-    logevent(buf);
+    logeventf(ssh, "Server sent command exit status %d", ssh->exitcode);
     send_packet(ssh, SSH1_CMSG_EXIT_CONFIRMATION, PKT_END);
     /*
      * In case `helpful' firewalls or proxies tack
@@ -4320,9 +4594,30 @@ static void ssh1_smsg_exit_status(Ssh ssh, struct Packet *pktin)
      * encrypted packet, we close the session once
      * we've sent EXIT_CONFIRMATION.
      */
-    ssh_closing((Plug)ssh, NULL, 0, 0);
+    ssh_disconnect(ssh, NULL, NULL, 0, TRUE);
 }
 
+/* Helper function to deal with sending tty modes for REQUEST_PTY */
+static void ssh1_send_ttymode(void *data, char *mode, char *val)
+{
+    struct Packet *pktout = (struct Packet *)data;
+    int i = 0;
+    unsigned int arg = 0;
+    while (strcmp(mode, ssh_ttymodes[i].mode) != 0) i++;
+    if (i == lenof(ssh_ttymodes)) return;
+    switch (ssh_ttymodes[i].type) {
+      case TTY_OP_CHAR:
+	arg = ssh_tty_parse_specchar(val);
+	break;
+      case TTY_OP_BOOL:
+	arg = ssh_tty_parse_boolean(val);
+	break;
+    }
+    ssh2_pkt_addbyte(pktout, ssh_ttymodes[i].opcode);
+    ssh2_pkt_addbyte(pktout, arg);
+}
+
+
 static void do_ssh1_connection(Ssh ssh, unsigned char *in, int inlen,
 			       struct Packet *pktin)
 {
@@ -4367,14 +4662,23 @@ static void do_ssh1_connection(Ssh ssh, unsigned char *in, int inlen,
 	ssh->x11auth = x11_invent_auth(proto, sizeof(proto),
 				       data, sizeof(data), ssh->cfg.x11_auth);
         x11_get_real_auth(ssh->x11auth, ssh->cfg.x11_display);
+	/*
+	 * Note that while we blank the X authentication data here, we don't
+	 * take any special action to blank the start of an X11 channel,
+	 * so using MIT-MAGIC-COOKIE-1 and actually opening an X connection
+	 * without having session blanking enabled is likely to leak your
+	 * cookie into the log.
+	 */
 	if (ssh->v1_local_protoflags & SSH1_PROTOFLAG_SCREEN_NUMBER) {
 	    send_packet(ssh, SSH1_CMSG_X11_REQUEST_FORWARDING,
-			PKT_STR, proto, PKT_STR, data,
+			PKT_STR, proto,
+			PKTT_PASSWORD, PKT_STR, data, PKTT_OTHER,
 			PKT_INT, x11_get_screen_number(ssh->cfg.x11_display),
 			PKT_END);
 	} else {
 	    send_packet(ssh, SSH1_CMSG_X11_REQUEST_FORWARDING,
-			PKT_STR, proto, PKT_STR, data, PKT_END);
+			PKT_STR, proto,
+			PKTT_PASSWORD, PKT_STR, data, PKTT_OTHER, PKT_END);
 	}
 	do {
 	    crReturnV;
@@ -4396,19 +4700,26 @@ static void do_ssh1_connection(Ssh ssh, unsigned char *in, int inlen,
     ssh->packet_dispatch[SSH1_MSG_PORT_OPEN] = ssh1_msg_port_open;
 
     if (!ssh->cfg.nopty) {
+	struct Packet *pkt;
 	/* Unpick the terminal-speed string. */
 	/* XXX perhaps we should allow no speeds to be sent. */
 	ssh->ospeed = 38400; ssh->ispeed = 38400; /* last-resort defaults */
 	sscanf(ssh->cfg.termspeed, "%d,%d", &ssh->ospeed, &ssh->ispeed);
 	/* Send the pty request. */
-	send_packet(ssh, SSH1_CMSG_REQUEST_PTY,
-		    PKT_STR, ssh->cfg.termtype,
-		    PKT_INT, ssh->term_height,
-		    PKT_INT, ssh->term_width,
-		    PKT_INT, 0, PKT_INT, 0, /* width,height in pixels */
-		    PKT_CHAR, 192, PKT_INT, ssh->ispeed, /* TTY_OP_ISPEED */
-		    PKT_CHAR, 193, PKT_INT, ssh->ospeed, /* TTY_OP_OSPEED */
-		    PKT_CHAR, 0, PKT_END);
+	pkt = ssh1_pkt_init(SSH1_CMSG_REQUEST_PTY);
+	ssh_pkt_addstring(pkt, ssh->cfg.termtype);
+	ssh_pkt_adduint32(pkt, ssh->term_height);
+	ssh_pkt_adduint32(pkt, ssh->term_width);
+	ssh_pkt_adduint32(pkt, 0); /* width in pixels */
+	ssh_pkt_adduint32(pkt, 0); /* height in pixels */
+	parse_ttymodes(ssh, ssh->cfg.ttymodes,
+		       ssh1_send_ttymode, (void *)pkt);
+	ssh_pkt_addbyte(pkt, SSH1_TTY_OP_ISPEED);
+	ssh_pkt_adduint32(pkt, ssh->ispeed);
+	ssh_pkt_addbyte(pkt, SSH1_TTY_OP_OSPEED);
+	ssh_pkt_adduint32(pkt, ssh->ospeed);
+	ssh_pkt_addbyte(pkt, SSH_TTY_OP_END);
+	s_wrpkt(ssh, pkt);
 	ssh->state = SSH_STATE_INTERMED;
 	do {
 	    crReturnV;
@@ -4450,12 +4761,14 @@ static void do_ssh1_connection(Ssh ssh, unsigned char *in, int inlen,
     /*
      * Start the shell or command.
      * 
-     * Special case: if the first-choice command is an SSH2
+     * Special case: if the first-choice command is an SSH-2
      * subsystem (hence not usable here) and the second choice
      * exists, we fall straight back to that.
      */
     {
 	char *cmd = ssh->cfg.remote_cmd_ptr;
+
+	if (!cmd) cmd = ssh->cfg.remote_cmd;
 	
 	if (ssh->cfg.ssh_subsys && ssh->cfg.remote_cmd_ptr2) {
 	    cmd = ssh->cfg.remote_cmd_ptr2;
@@ -4513,17 +4826,15 @@ static void do_ssh1_connection(Ssh ssh, unsigned char *in, int inlen,
 }
 
 /*
- * Handle the top-level SSH2 protocol.
+ * Handle the top-level SSH-2 protocol.
  */
 static void ssh1_msg_debug(Ssh ssh, struct Packet *pktin)
 {
-    char *buf, *msg;
+    char *msg;
     int msglen;
 
     ssh_pkt_getstring(pktin, &msg, &msglen);
-    buf = dupprintf("Remote debug message: %.*s", msglen, msg);
-    logevent(buf);
-    sfree(buf);
+    logeventf(ssh, "Remote debug message: %.*s", msglen, msg);
 }
 
 static void ssh1_msg_disconnect(Ssh ssh, struct Packet *pktin)
@@ -4536,7 +4847,7 @@ static void ssh1_msg_disconnect(Ssh ssh, struct Packet *pktin)
     bombout(("Server sent disconnect message:\n\"%.*s\"", msglen, msg));
 }
 
-void ssh_msg_ignore(Ssh ssh, struct Packet *pktin)
+static void ssh_msg_ignore(Ssh ssh, struct Packet *pktin)
 {
     /* Do nothing, because we're ignoring it! Duhh. */
 }
@@ -4559,9 +4870,10 @@ static void ssh1_protocol_setup(Ssh ssh)
     ssh->packet_dispatch[SSH1_MSG_DEBUG] = ssh1_msg_debug;
 }
 
-static void ssh1_protocol(Ssh ssh, unsigned char *in, int inlen,
+static void ssh1_protocol(Ssh ssh, void *vin, int inlen,
 			  struct Packet *pktin)
 {
+    unsigned char *in=(unsigned char*)vin;
     if (ssh->state == SSH_STATE_CLOSED)
 	return;
 
@@ -4612,39 +4924,64 @@ static int in_commasep_string(char *needle, char *haystack, int haylen)
 }
 
 /*
- * SSH2 key creation method.
+ * Similar routine for checking whether we have the first string in a list.
  */
-static void ssh2_mkkey(Ssh ssh, Bignum K, unsigned char *H,
-		       unsigned char *sessid, char chr,
+static int first_in_commasep_string(char *needle, char *haystack, int haylen)
+{
+    int needlen;
+    if (!needle || !haystack)	       /* protect against null pointers */
+	return 0;
+    needlen = strlen(needle);
+    /*
+     * Is it at the start of the string?
+     */
+    if (haylen >= needlen &&       /* haystack is long enough */
+	!memcmp(needle, haystack, needlen) &&	/* initial match */
+	(haylen == needlen || haystack[needlen] == ',')
+	/* either , or EOS follows */
+	)
+	return 1;
+    return 0;
+}
+
+
+/*
+ * SSH-2 key creation method.
+ */
+static void ssh2_mkkey(Ssh ssh, Bignum K, unsigned char *H, char chr,
 		       unsigned char *keyspace)
 {
-    SHA_State s;
-    /* First 20 bytes. */
-    SHA_Init(&s);
+    const struct ssh_hash *h = ssh->kex->hash;
+    void *s;
+    /* First hlen bytes. */
+    s = h->init();
     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);
+	hash_mpint(h, s, K);
+    h->bytes(s, H, h->hlen);
+    h->bytes(s, &chr, 1);
+    h->bytes(s, ssh->v2_session_id, ssh->v2_session_id_len);
+    h->final(s, keyspace);
+    /* Next hlen bytes. */
+    s = h->init();
     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);
+	hash_mpint(h, s, K);
+    h->bytes(s, H, h->hlen);
+    h->bytes(s, keyspace, h->hlen);
+    h->final(s, keyspace + h->hlen);
 }
 
 /*
- * Handle the SSH2 transport layer.
+ * Handle the SSH-2 transport layer.
  */
-static int do_ssh2_transport(Ssh ssh, unsigned char *in, int inlen,
+static int do_ssh2_transport(Ssh ssh, void *vin, int inlen,
 			     struct Packet *pktin)
 {
+    unsigned char *in = (unsigned char *)vin;
     struct do_ssh2_transport_state {
-	int nbits, pbits, warn;
+	int nbits, pbits, warn_kex, warn_cscipher, warn_sccipher;
 	Bignum p, g, e, f, K;
+	void *our_kexinit;
+	int our_kexinitlen;
 	int kex_init_value, kex_reply_value;
 	const struct ssh_mac **maclist;
 	int nmacs;
@@ -4657,14 +4994,17 @@ static int do_ssh2_transport(Ssh ssh, unsigned char *in, int inlen,
 	char *hostkeydata, *sigdata, *keystr, *fingerprint;
 	int hostkeylen, siglen;
 	void *hkey;		       /* actual host key */
-	unsigned char exchange_hash[20];
+	unsigned char exchange_hash[32];
 	int n_preferred_kex;
-	const struct ssh_kex *preferred_kex[KEX_MAX];
+	const struct ssh_kexes *preferred_kex[KEX_MAX];
 	int n_preferred_ciphers;
 	const struct ssh2_ciphers *preferred_ciphers[CIPHER_MAX];
 	const struct ssh_compress *preferred_comp;
 	int got_session_id, activated_authconn;
 	struct Packet *pktout;
+        int dlgret;
+	int guessok;
+	int ignorepkt;
     };
     crState(do_ssh2_transport_state);
 
@@ -4737,6 +5077,9 @@ static int do_ssh2_transport(Ssh ssh, unsigned char *in, int inlen,
 	      case CIPHER_AES:
 		s->preferred_ciphers[s->n_preferred_ciphers++] = &ssh2_aes;
 		break;
+	      case CIPHER_ARCFOUR:
+		s->preferred_ciphers[s->n_preferred_ciphers++] = &ssh2_arcfour;
+		break;
 	      case CIPHER_WARN:
 		/* Flag for later. Don't bother if it's the last in
 		 * the list. */
@@ -4776,12 +5119,14 @@ static int do_ssh2_transport(Ssh ssh, unsigned char *in, int inlen,
 	ssh2_pkt_addstring_start(s->pktout);
 	commalist_started = 0;
 	for (i = 0; i < s->n_preferred_kex; i++) {
-	    const struct ssh_kex *k = s->preferred_kex[i];
+	    const struct ssh_kexes *k = s->preferred_kex[i];
 	    if (!k) continue;	       /* warning flag */
-	    if (commalist_started)
-		ssh2_pkt_addstring_str(s->pktout, ",");
-	    ssh2_pkt_addstring_str(s->pktout, s->preferred_kex[i]->name);
-	    commalist_started = 1;
+	    for (j = 0; j < k->nkexes; j++) {
+		if (commalist_started)
+		    ssh2_pkt_addstring_str(s->pktout, ",");
+		ssh2_pkt_addstring_str(s->pktout, k->list[j]->name);
+		commalist_started = 1;
+	    }
 	}
 	/* List server host key algorithms. */
 	ssh2_pkt_addstring_start(s->pktout);
@@ -4862,22 +5207,21 @@ static int do_ssh2_transport(Ssh ssh, unsigned char *in, int inlen,
 	ssh2_pkt_adduint32(s->pktout, 0);
     }
 
-    ssh->exhash = ssh->exhashbase;
-    sha_string(&ssh->exhash, s->pktout->data + 5, s->pktout->length - 5);
+    s->our_kexinitlen = s->pktout->length - 5;
+    s->our_kexinit = snewn(s->our_kexinitlen, unsigned char);
+    memcpy(s->our_kexinit, s->pktout->data + 5, s->our_kexinitlen); 
 
     ssh2_pkt_send_noqueue(ssh, s->pktout);
 
     if (!pktin)
 	crWaitUntil(pktin);
-    if (pktin->length > 5)
-	sha_string(&ssh->exhash, pktin->data + 5, pktin->length - 5);
 
     /*
      * Now examine the other side's KEXINIT to see what we're up
      * to.
      */
     {
-	char *str;
+	char *str, *preferred;
 	int i, j, len;
 
 	if (pktin->type != SSH2_MSG_KEXINIT) {
@@ -4892,31 +5236,39 @@ static int do_ssh2_transport(Ssh ssh, unsigned char *in, int inlen,
 	s->scmac_tobe = NULL;
 	s->cscomp_tobe = NULL;
 	s->sccomp_tobe = NULL;
+	s->warn_kex = s->warn_cscipher = s->warn_sccipher = FALSE;
+
 	pktin->savedpos += 16;	        /* skip garbage cookie */
 	ssh_pkt_getstring(pktin, &str, &len);    /* key exchange algorithms */
-	s->warn = 0;
+
+	preferred = NULL;
 	for (i = 0; i < s->n_preferred_kex; i++) {
-	    const struct ssh_kex *k = s->preferred_kex[i];
+	    const struct ssh_kexes *k = s->preferred_kex[i];
 	    if (!k) {
-		s->warn = 1;
-	    } else if (in_commasep_string(k->name, str, len)) {
-		ssh->kex = k;
+		s->warn_kex = TRUE;
+	    } else {
+		for (j = 0; j < k->nkexes; j++) {
+		    if (!preferred) preferred = k->list[j]->name;
+		    if (in_commasep_string(k->list[j]->name, str, len)) {
+			ssh->kex = k->list[j];
+			break;
+		    }
+		}
 	    }
-	    if (ssh->kex) {
-		if (s->warn) {
-                    sk_set_frozen(ssh->s, 1);
-		    askalg(ssh->frontend, "key-exchange algorithm",
-			   ssh->kex->name);
-                    sk_set_frozen(ssh->s, 0);
-                }
+	    if (ssh->kex)
 		break;
-	    }
 	}
 	if (!ssh->kex) {
 	    bombout(("Couldn't agree a key exchange algorithm (available: %s)",
 		     str ? str : "(null)"));
 	    crStop(0);
 	}
+	/*
+	 * Note that the server's guess is considered wrong if it doesn't match
+	 * the first algorithm in our list, even if it's still the algorithm
+	 * we end up using.
+	 */
+	s->guessok = first_in_commasep_string(preferred, str, len);
 	ssh_pkt_getstring(pktin, &str, &len);    /* host key algorithms */
 	for (i = 0; i < lenof(hostkey_algs); i++) {
 	    if (in_commasep_string(hostkey_algs[i]->name, str, len)) {
@@ -4924,12 +5276,13 @@ static int do_ssh2_transport(Ssh ssh, unsigned char *in, int inlen,
 		break;
 	    }
 	}
+	s->guessok = s->guessok &&
+	    first_in_commasep_string(hostkey_algs[0]->name, str, len);
 	ssh_pkt_getstring(pktin, &str, &len);    /* client->server cipher */
-	s->warn = 0;
 	for (i = 0; i < s->n_preferred_ciphers; i++) {
 	    const struct ssh2_ciphers *c = s->preferred_ciphers[i];
 	    if (!c) {
-		s->warn = 1;
+		s->warn_cscipher = TRUE;
 	    } else {
 		for (j = 0; j < c->nciphers; j++) {
 		    if (in_commasep_string(c->list[j]->name, str, len)) {
@@ -4938,15 +5291,8 @@ static int do_ssh2_transport(Ssh ssh, unsigned char *in, int inlen,
 		    }
 		}
 	    }
-	    if (s->cscipher_tobe) {
-		if (s->warn) {
-                    sk_set_frozen(ssh->s, 1);
-		    askalg(ssh->frontend, "client-to-server cipher",
-			   s->cscipher_tobe->name);
-                    sk_set_frozen(ssh->s, 0);
-                }
+	    if (s->cscipher_tobe)
 		break;
-	    }
 	}
 	if (!s->cscipher_tobe) {
 	    bombout(("Couldn't agree a client-to-server cipher (available: %s)",
@@ -4955,11 +5301,10 @@ static int do_ssh2_transport(Ssh ssh, unsigned char *in, int inlen,
 	}
 
 	ssh_pkt_getstring(pktin, &str, &len);    /* server->client cipher */
-	s->warn = 0;
 	for (i = 0; i < s->n_preferred_ciphers; i++) {
 	    const struct ssh2_ciphers *c = s->preferred_ciphers[i];
 	    if (!c) {
-		s->warn = 1;
+		s->warn_sccipher = TRUE;
 	    } else {
 		for (j = 0; j < c->nciphers; j++) {
 		    if (in_commasep_string(c->list[j]->name, str, len)) {
@@ -4968,15 +5313,8 @@ static int do_ssh2_transport(Ssh ssh, unsigned char *in, int inlen,
 		    }
 		}
 	    }
-	    if (s->sccipher_tobe) {
-		if (s->warn) {
-                    sk_set_frozen(ssh->s, 1);
-		    askalg(ssh->frontend, "server-to-client cipher",
-			   s->sccipher_tobe->name);
-                    sk_set_frozen(ssh->s, 0);
-                }
+	    if (s->sccipher_tobe)
 		break;
-	    }
 	}
 	if (!s->sccipher_tobe) {
 	    bombout(("Couldn't agree a server-to-client cipher (available: %s)",
@@ -5016,6 +5354,96 @@ static int do_ssh2_transport(Ssh ssh, unsigned char *in, int inlen,
 		break;
 	    }
 	}
+	ssh_pkt_getstring(pktin, &str, &len);  /* client->server language */
+	ssh_pkt_getstring(pktin, &str, &len);  /* server->client language */
+	s->ignorepkt = ssh2_pkt_getbool(pktin) && !s->guessok;
+
+	if (s->warn_kex) {
+	    ssh_set_frozen(ssh, 1);
+	    s->dlgret = askalg(ssh->frontend, "key-exchange algorithm",
+			       ssh->kex->name,
+			       ssh_dialog_callback, ssh);
+	    if (s->dlgret < 0) {
+		do {
+		    crReturn(0);
+		    if (pktin) {
+			bombout(("Unexpected data from server while"
+				 " waiting for user response"));
+			crStop(0);
+		    }
+		} while (pktin || inlen > 0);
+		s->dlgret = ssh->user_response;
+	    }
+	    ssh_set_frozen(ssh, 0);
+	    if (s->dlgret == 0) {
+		ssh_disconnect(ssh, "User aborted at kex warning", NULL,
+			       0, TRUE);
+		crStop(0);
+	    }
+	}
+
+	if (s->warn_cscipher) {
+	    ssh_set_frozen(ssh, 1);
+	    s->dlgret = askalg(ssh->frontend,
+			       "client-to-server cipher",
+			       s->cscipher_tobe->name,
+			       ssh_dialog_callback, ssh);
+	    if (s->dlgret < 0) {
+		do {
+		    crReturn(0);
+		    if (pktin) {
+			bombout(("Unexpected data from server while"
+				 " waiting for user response"));
+			crStop(0);
+		    }
+		} while (pktin || inlen > 0);
+		s->dlgret = ssh->user_response;
+	    }
+	    ssh_set_frozen(ssh, 0);
+	    if (s->dlgret == 0) {
+		ssh_disconnect(ssh, "User aborted at cipher warning", NULL,
+			       0, TRUE);
+		crStop(0);
+	    }
+	}
+
+	if (s->warn_sccipher) {
+	    ssh_set_frozen(ssh, 1);
+	    s->dlgret = askalg(ssh->frontend,
+			       "server-to-client cipher",
+			       s->sccipher_tobe->name,
+			       ssh_dialog_callback, ssh);
+	    if (s->dlgret < 0) {
+		do {
+		    crReturn(0);
+		    if (pktin) {
+			bombout(("Unexpected data from server while"
+				 " waiting for user response"));
+			crStop(0);
+		    }
+		} while (pktin || inlen > 0);
+		s->dlgret = ssh->user_response;
+	    }
+	    ssh_set_frozen(ssh, 0);
+	    if (s->dlgret == 0) {
+		ssh_disconnect(ssh, "User aborted at cipher warning", NULL,
+			       0, TRUE);
+		crStop(0);
+	    }
+	}
+
+	ssh->exhash = ssh->kex->hash->init();
+	hash_string(ssh->kex->hash, ssh->exhash, ssh->v_c, strlen(ssh->v_c));
+	hash_string(ssh->kex->hash, ssh->exhash, ssh->v_s, strlen(ssh->v_s));
+	hash_string(ssh->kex->hash, ssh->exhash,
+	    s->our_kexinit, s->our_kexinitlen);
+	sfree(s->our_kexinit);
+	if (pktin->length > 5)
+	    hash_string(ssh->kex->hash, ssh->exhash,
+		pktin->data + 5, pktin->length - 5);
+
+	if (s->ignorepkt) /* first_kex_packet_follows */
+	    crWaitUntil(pktin);                /* Ignore packet */
     }
 
     /*
@@ -5030,10 +5458,10 @@ static int do_ssh2_transport(Ssh ssh, unsigned char *in, int inlen,
 	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 (s->nbits > 160)
-	s->nbits = 160;
+    /* The keys only have hlen-bit entropy, since they're based on
+     * a hash. So cap the key size at hlen bits. */
+    if (s->nbits > ssh->kex->hash->hlen * 8)
+	s->nbits = ssh->kex->hash->hlen * 8;
 
     /*
      * If we're doing Diffie-Hellman group exchange, start by
@@ -5078,16 +5506,19 @@ static int do_ssh2_transport(Ssh ssh, unsigned char *in, int inlen,
     /*
      * Now generate and send e for Diffie-Hellman.
      */
+    set_busy_status(ssh->frontend, BUSY_CPU); /* this can take a while */
     s->e = dh_create_e(ssh->kex_ctx, s->nbits * 2);
     s->pktout = ssh2_pkt_init(s->kex_init_value);
     ssh2_pkt_addmp(s->pktout, s->e);
     ssh2_pkt_send_noqueue(ssh, s->pktout);
 
+    set_busy_status(ssh->frontend, BUSY_WAITING); /* wait for server */
     crWaitUntil(pktin);
     if (pktin->type != s->kex_reply_value) {
 	bombout(("expected key exchange reply packet from server"));
 	crStop(0);
     }
+    set_busy_status(ssh->frontend, BUSY_CPU); /* cogitate */
     ssh_pkt_getstring(pktin, &s->hostkeydata, &s->hostkeylen);
     s->f = ssh2_pkt_getmp(pktin);
     if (!s->f) {
@@ -5098,29 +5529,35 @@ static int do_ssh2_transport(Ssh ssh, unsigned char *in, int inlen,
 
     s->K = dh_find_K(ssh->kex_ctx, s->f);
 
-    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);
+    /* We assume everything from now on will be quick, and it might
+     * involve user interaction. */
+    set_busy_status(ssh->frontend, BUSY_NOT);
+
+    hash_string(ssh->kex->hash, ssh->exhash, s->hostkeydata, s->hostkeylen);
+    if (!ssh->kex->pdata) {
+	hash_uint32(ssh->kex->hash, ssh->exhash, s->pbits);
+	hash_mpint(ssh->kex->hash, ssh->exhash, s->p);
+	hash_mpint(ssh->kex->hash, ssh->exhash, s->g);
     }
-    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);
+    hash_mpint(ssh->kex->hash, ssh->exhash, s->e);
+    hash_mpint(ssh->kex->hash, ssh->exhash, s->f);
+    hash_mpint(ssh->kex->hash, ssh->exhash, s->K);
+    assert(ssh->kex->hash->hlen <= sizeof(s->exchange_hash));
+    ssh->kex->hash->final(ssh->exhash, s->exchange_hash);
 
     dh_cleanup(ssh->kex_ctx);
     ssh->kex_ctx = NULL;
 
 #if 0
     debug(("Exchange hash is:\n"));
-    dmemdump(s->exchange_hash, 20);
+    dmemdump(s->exchange_hash, ssh->kex->hash->hlen);
 #endif
 
     s->hkey = ssh->hostkey->newkey(s->hostkeydata, s->hostkeylen);
     if (!s->hkey ||
 	!ssh->hostkey->verifysig(s->hkey, s->sigdata, s->siglen,
-				 (char *)s->exchange_hash, 20)) {
+				 (char *)s->exchange_hash,
+				 ssh->kex->hash->hlen)) {
 	bombout(("Server's host key did not match the signature supplied"));
 	crStop(0);
     }
@@ -5131,11 +5568,29 @@ static int do_ssh2_transport(Ssh ssh, unsigned char *in, int inlen,
      */
     s->keystr = ssh->hostkey->fmtkey(s->hkey);
     s->fingerprint = ssh->hostkey->fingerprint(s->hkey);
-    sk_set_frozen(ssh->s, 1);
-    verify_ssh_host_key(ssh->frontend,
-			ssh->savedhost, ssh->savedport, ssh->hostkey->keytype,
-			s->keystr, s->fingerprint);
-    sk_set_frozen(ssh->s, 0);
+    ssh_set_frozen(ssh, 1);
+    s->dlgret = verify_ssh_host_key(ssh->frontend,
+                                    ssh->savedhost, ssh->savedport,
+                                    ssh->hostkey->keytype, s->keystr,
+				    s->fingerprint,
+                                    ssh_dialog_callback, ssh);
+    if (s->dlgret < 0) {
+        do {
+            crReturn(0);
+            if (pktin) {
+                bombout(("Unexpected data from server while waiting"
+                         " for user host key response"));
+                    crStop(0);
+            }
+        } while (pktin || inlen > 0);
+        s->dlgret = ssh->user_response;
+    }
+    ssh_set_frozen(ssh, 0);
+    if (s->dlgret == 0) {
+	ssh_disconnect(ssh, "User aborted at host key verification", NULL,
+		       0, TRUE);
+        crStop(0);
+    }
     if (!s->got_session_id) {     /* don't bother logging this in rekeys */
 	logevent("Host key fingerprint is:");
 	logevent(s->fingerprint);
@@ -5150,8 +5605,11 @@ static int do_ssh2_transport(Ssh ssh, unsigned char *in, int inlen,
      * authentication.
      */
     if (!s->got_session_id) {
+	assert(sizeof(s->exchange_hash) <= sizeof(ssh->v2_session_id));
 	memcpy(ssh->v2_session_id, s->exchange_hash,
 	       sizeof(s->exchange_hash));
+	ssh->v2_session_id_len = ssh->kex->hash->hlen;
+	assert(ssh->v2_session_id_len <= sizeof(ssh->v2_session_id));
 	s->got_session_id = TRUE;
     }
 
@@ -5187,11 +5645,11 @@ static int do_ssh2_transport(Ssh ssh, unsigned char *in, int inlen,
      */
     {
 	unsigned char keyspace[40];
-	ssh2_mkkey(ssh,s->K,s->exchange_hash,ssh->v2_session_id,'C',keyspace);
+	ssh2_mkkey(ssh,s->K,s->exchange_hash,'C',keyspace);
 	ssh->cscipher->setkey(ssh->cs_cipher_ctx, keyspace);
-	ssh2_mkkey(ssh,s->K,s->exchange_hash,ssh->v2_session_id,'A',keyspace);
+	ssh2_mkkey(ssh,s->K,s->exchange_hash,'A',keyspace);
 	ssh->cscipher->setiv(ssh->cs_cipher_ctx, keyspace);
-	ssh2_mkkey(ssh,s->K,s->exchange_hash,ssh->v2_session_id,'E',keyspace);
+	ssh2_mkkey(ssh,s->K,s->exchange_hash,'E',keyspace);
 	ssh->csmac->setkey(ssh->cs_mac_ctx, keyspace);
     }
 
@@ -5245,11 +5703,11 @@ static int do_ssh2_transport(Ssh ssh, unsigned char *in, int inlen,
      */
     {
 	unsigned char keyspace[40];
-	ssh2_mkkey(ssh,s->K,s->exchange_hash,ssh->v2_session_id,'D',keyspace);
+	ssh2_mkkey(ssh,s->K,s->exchange_hash,'D',keyspace);
 	ssh->sccipher->setkey(ssh->sc_cipher_ctx, keyspace);
-	ssh2_mkkey(ssh,s->K,s->exchange_hash,ssh->v2_session_id,'B',keyspace);
+	ssh2_mkkey(ssh,s->K,s->exchange_hash,'B',keyspace);
 	ssh->sccipher->setiv(ssh->sc_cipher_ctx, keyspace);
-	ssh2_mkkey(ssh,s->K,s->exchange_hash,ssh->v2_session_id,'F',keyspace);
+	ssh2_mkkey(ssh,s->K,s->exchange_hash,'F',keyspace);
 	ssh->scmac->setkey(ssh->sc_mac_ctx, keyspace);
     }
     logeventf(ssh, "Initialised %.200s server->client encryption",
@@ -5265,7 +5723,7 @@ static int do_ssh2_transport(Ssh ssh, unsigned char *in, int inlen,
      */
     freebn(s->f);
     freebn(s->K);
-    if (ssh->kex == &ssh_diffiehellman_gex) {
+    if (!ssh->kex->pdata) {
 	freebn(s->g);
 	freebn(s->p);
     }
@@ -5299,7 +5757,7 @@ static int do_ssh2_transport(Ssh ssh, unsigned char *in, int inlen,
      * it would only confuse the layer above.
      */
     if (s->activated_authconn) {
-	crReturn(1);
+	crReturn(0);
     }
     s->activated_authconn = TRUE;
 
@@ -5351,7 +5809,7 @@ static int do_ssh2_transport(Ssh ssh, unsigned char *in, int inlen,
 }
 
 /*
- * Add data to an SSH2 channel output buffer.
+ * Add data to an SSH-2 channel output buffer.
  */
 static void ssh2_add_channel_data(struct ssh_channel *c, char *buf,
 				  int len)
@@ -5360,7 +5818,7 @@ static void ssh2_add_channel_data(struct ssh_channel *c, char *buf,
 }
 
 /*
- * Attempt to send data on an SSH2 channel.
+ * Attempt to send data on an SSH-2 channel.
  */
 static int ssh2_try_send(struct ssh_channel *c)
 {
@@ -5393,8 +5851,34 @@ static int ssh2_try_send(struct ssh_channel *c)
     return bufchain_size(&c->v.v2.outbuffer);
 }
 
+static void ssh2_try_send_and_unthrottle(struct ssh_channel *c)
+{
+    int bufsize;
+    if (c->closes)
+	return;			       /* don't send on closing channels */
+    bufsize = ssh2_try_send(c);
+    if (bufsize == 0) {
+	switch (c->type) {
+	  case CHAN_MAINSESSION:
+	    /* stdin need not receive an unthrottle
+	     * notification since it will be polled */
+	    break;
+	  case CHAN_X11:
+	    x11_unthrottle(c->u.x11.s);
+	    break;
+	  case CHAN_AGENT:
+	    /* agent sockets are request/response and need no
+	     * buffer management */
+	    break;
+	  case CHAN_SOCKDATA:
+	    pfd_unthrottle(c->u.pfd.s);
+	    break;
+	}
+    }
+}
+
 /*
- * Potentially enlarge the window on an SSH2 channel.
+ * Potentially enlarge the window on an SSH-2 channel.
  */
 static void ssh2_set_window(struct ssh_channel *c, unsigned newwin)
 {
@@ -5408,7 +5892,14 @@ static void ssh2_set_window(struct ssh_channel *c, unsigned newwin)
     if (c->closes != 0)
 	return;
 
-    if (newwin > c->v.v2.locwindow) {
+    /*
+     * Only send a WINDOW_ADJUST if there's significantly more window
+     * available than the other end thinks there is.  This saves us
+     * sending a WINDOW_ADJUST for every character in a shell session.
+     *
+     * "Significant" is arbitrarily defined as half the window size.
+     */
+    if (newwin > c->v.v2.locwindow * 2) {
 	struct Packet *pktout;
 
 	pktout = ssh2_pkt_init(SSH2_MSG_CHANNEL_WINDOW_ADJUST);
@@ -5424,14 +5915,16 @@ static void ssh2_msg_channel_window_adjust(Ssh ssh, struct Packet *pktin)
     unsigned i = ssh_pkt_getuint32(pktin);
     struct ssh_channel *c;
     c = find234(ssh->channels, &i, ssh_channelfind);
-    if (c && !c->closes)
+    if (c && !c->closes) {
 	c->v.v2.remwindow += ssh_pkt_getuint32(pktin);
+	ssh2_try_send_and_unthrottle(c);
+    }
 }
 
 static void ssh2_msg_channel_data(Ssh ssh, struct Packet *pktin)
 {
     char *data;
-    unsigned int length;
+    int length;
     unsigned i = ssh_pkt_getuint32(pktin);
     struct ssh_channel *c;
     c = find234(ssh->channels, &i, ssh_channelfind);
@@ -5539,7 +6032,7 @@ static void ssh2_msg_channel_close(Ssh ssh, struct Packet *pktin)
     struct Packet *pktout;
 
     c = find234(ssh->channels, &i, ssh_channelfind);
-    if (!c || ((int)c->remoteid) == -1) {
+    if (!c || c->halfopen) {
 	bombout(("Received CHANNEL_CLOSE for %s channel %d\n",
 		 c ? "half-open" : "nonexistent", i));
 	return;
@@ -5579,12 +6072,10 @@ static void ssh2_msg_channel_close(Ssh ssh, struct Packet *pktin)
      * not running in -N mode.)
      */
     if (!ssh->cfg.ssh_no_shell && count234(ssh->channels) == 0) {
-	logevent("All channels closed. Disconnecting");
-#if 0
 	/*
 	 * We used to send SSH_MSG_DISCONNECT here,
 	 * because I'd believed that _every_ conforming
-	 * SSH2 connection had to end with a disconnect
+	 * SSH-2 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
@@ -5592,13 +6083,7 @@ static void ssh2_msg_channel_close(Ssh ssh, struct Packet *pktin)
 	 * this is more polite than sending a
 	 * DISCONNECT. So now we don't.
 	 */
-	s->pktout = ssh2_pkt_init(SSH2_MSG_DISCONNECT);
-	ssh2_pkt_adduint32(s->pktout, SSH2_DISCONNECT_BY_APPLICATION);
-	ssh2_pkt_addstring(s->pktout, "All open channels closed");
-	ssh2_pkt_addstring(s->pktout, "en");	/* language tag */
-	ssh2_pkt_send_noqueue(ssh, s->pktout);
-#endif
-	ssh_closing((Plug)ssh, NULL, 0, 0);
+	ssh_disconnect(ssh, "All channels closed", NULL, 0, TRUE);
     }
 }
 
@@ -5614,6 +6099,7 @@ static void ssh2_msg_channel_open_confirmation(Ssh ssh, struct Packet *pktin)
     if (c->type != CHAN_SOCKDATA_DORMANT)
 	return;			       /* dunno why they're confirming this */
     c->remoteid = ssh_pkt_getuint32(pktin);
+    c->halfopen = FALSE;
     c->type = CHAN_SOCKDATA;
     c->v.v2.remwindow = ssh_pkt_getuint32(pktin);
     c->v.v2.remmaxpkt = ssh_pkt_getuint32(pktin);
@@ -5645,7 +6131,6 @@ static void ssh2_msg_channel_open_failure(Ssh ssh, struct Packet *pktin)
     unsigned reason_code;
     char *reason_string;
     int reason_length;
-    char *message;
     struct ssh_channel *c;
     c = find234(ssh->channels, &i, ssh_channelfind);
     if (!c)
@@ -5657,11 +6142,8 @@ static void ssh2_msg_channel_open_failure(Ssh ssh, struct Packet *pktin)
     if (reason_code >= lenof(reasons))
 	reason_code = 0; /* ensure reasons[reason_code] in range */
     ssh_pkt_getstring(pktin, &reason_string, &reason_length);
-    message = dupprintf("Forwarded connection refused by"
-			" server: %s [%.*s]", reasons[reason_code],
-			reason_length, reason_string);
-    logevent(message);
-    sfree(message);
+    logeventf(ssh, "Forwarded connection refused by server: %s [%.*s]",
+	      reasons[reason_code], reason_length, reason_string);
 
     pfd_close(c->u.pfd.s);
 
@@ -5688,17 +6170,10 @@ static void ssh2_msg_channel_request(Ssh ssh, struct Packet *pktin)
      */
     c = find234(ssh->channels, &localid, ssh_channelfind);
     if (!c) {
-	char buf[80];
-	sprintf(buf, "Received channel request for nonexistent"
-		" channel %d", localid);
-	logevent(buf);
-	pktout = ssh2_pkt_init(SSH2_MSG_DISCONNECT);
-	ssh2_pkt_adduint32(pktout, SSH2_DISCONNECT_BY_APPLICATION);
-	ssh2_pkt_addstring(pktout, buf);
-	ssh2_pkt_addstring(pktout, "en");	/* language tag */
-	ssh2_pkt_send_noqueue(ssh, pktout);
-	connection_fatal(ssh->frontend, "%s", buf);
-	ssh_closing((Plug)ssh, NULL, 0, 0);
+	char *buf = dupprintf("Received channel request for nonexistent"
+			      " channel %d", localid);
+	ssh_disconnect(ssh, NULL, buf, SSH2_DISCONNECT_PROTOCOL_ERROR, FALSE);
+	sfree(buf);
 	return;
     }
 
@@ -5748,7 +6223,7 @@ static void ssh2_msg_channel_request(Ssh ssh, struct Packet *pktin)
 	if (q >= 0 && q+4 <= len) { \
 	    q = q + 4 + GET_32BIT(p+q); \
 	    if (q >= 0 && q+4 <= len && \
-		    (q = q + 4 + GET_32BIT(p+q)) && q == len) \
+		    ((q = q + 4 + GET_32BIT(p+q))!= 0) && q == len) \
 		result = TRUE; \
 	} \
     } while(0)
@@ -5908,7 +6383,7 @@ static void ssh2_msg_channel_open(Ssh ssh, struct Packet *pktin)
 	    }
 	}
     } else if (typelen == 22 &&
-	       !memcmp(type, "auth-agent@openssh.com", 3)) {
+	       !memcmp(type, "auth-agent@openssh.com", 22)) {
 	if (!ssh->agentfwd_enabled)
 	    error = "Agent forwarding is not enabled";
 	else {
@@ -5920,6 +6395,7 @@ static void ssh2_msg_channel_open(Ssh ssh, struct Packet *pktin)
     }
 
     c->remoteid = remid;
+    c->halfopen = FALSE;
     if (error) {
 	pktout = ssh2_pkt_init(SSH2_MSG_CHANNEL_OPEN_FAILURE);
 	ssh2_pkt_adduint32(pktout, c->remoteid);
@@ -5941,13 +6417,48 @@ static void ssh2_msg_channel_open(Ssh ssh, struct Packet *pktin)
 	ssh2_pkt_adduint32(pktout, c->remoteid);
 	ssh2_pkt_adduint32(pktout, c->localid);
 	ssh2_pkt_adduint32(pktout, c->v.v2.locwindow);
-	ssh2_pkt_adduint32(pktout, 0x4000UL);	/* our max pkt size */
+	ssh2_pkt_adduint32(pktout, OUR_V2_MAXPKT);	/* our max pkt size */
 	ssh2_pkt_send(ssh, pktout);
     }
 }
 
 /*
- * Handle the SSH2 userauth and connection layers.
+ * Buffer banner messages for later display at some convenient point.
+ */
+static void ssh2_msg_userauth_banner(Ssh ssh, struct Packet *pktin)
+{
+    /* Arbitrary limit to prevent unbounded inflation of buffer */
+    if (bufchain_size(&ssh->banner) <= 131072) {
+	char *banner = NULL;
+	int size = 0;
+	ssh_pkt_getstring(pktin, &banner, &size);
+	if (banner)
+	    bufchain_add(&ssh->banner, banner, size);
+    }
+}
+
+/* Helper function to deal with sending tty modes for "pty-req" */
+static void ssh2_send_ttymode(void *data, char *mode, char *val)
+{
+    struct Packet *pktout = (struct Packet *)data;
+    int i = 0;
+    unsigned int arg = 0;
+    while (strcmp(mode, ssh_ttymodes[i].mode) != 0) i++;
+    if (i == lenof(ssh_ttymodes)) return;
+    switch (ssh_ttymodes[i].type) {
+      case TTY_OP_CHAR:
+	arg = ssh_tty_parse_specchar(val);
+	break;
+      case TTY_OP_BOOL:
+	arg = ssh_tty_parse_boolean(val);
+	break;
+    }
+    ssh2_pkt_addbyte(pktout, ssh_ttymodes[i].opcode);
+    ssh2_pkt_adduint32(pktout, arg);
+}
+
+/*
+ * Handle the SSH-2 userauth and connection layers.
  */
 static void do_ssh2_authconn(Ssh ssh, unsigned char *in, int inlen,
 			     struct Packet *pktin)
@@ -5967,6 +6478,7 @@ static void do_ssh2_authconn(Ssh ssh, unsigned char *in, int inlen,
 		AUTH_TYPE_KEYBOARD_INTERACTIVE,
 		AUTH_TYPE_KEYBOARD_INTERACTIVE_QUIET
 	} type;
+	int done_service_req;
 	int gotit, need_pw, can_pubkey, can_passwd, can_keyb_inter;
 	int tried_pubkey_config, tried_agent;
 	int kbd_inter_running, kbd_inter_refused;
@@ -5994,16 +6506,33 @@ static void do_ssh2_authconn(Ssh ssh, unsigned char *in, int inlen,
 
     crBegin(ssh->do_ssh2_authconn_crstate);
 
-    /*
-     * Request userauth protocol, and await a response to it.
-     */
-    s->pktout = ssh2_pkt_init(SSH2_MSG_SERVICE_REQUEST);
-    ssh2_pkt_addstring(s->pktout, "ssh-userauth");
-    ssh2_pkt_send(ssh, s->pktout);
-    crWaitUntilV(pktin);
-    if (pktin->type != SSH2_MSG_SERVICE_ACCEPT) {
-	bombout(("Server refused user authentication protocol"));
-	crStopV;
+    s->done_service_req = FALSE;
+    s->we_are_in = FALSE;
+    if (!ssh->cfg.ssh_no_userauth) {
+	/*
+	 * Request userauth protocol, and await a response to it.
+	 */
+	s->pktout = ssh2_pkt_init(SSH2_MSG_SERVICE_REQUEST);
+	ssh2_pkt_addstring(s->pktout, "ssh-userauth");
+	ssh2_pkt_send(ssh, s->pktout);
+	crWaitUntilV(pktin);
+	if (pktin->type == SSH2_MSG_SERVICE_ACCEPT)
+	    s->done_service_req = TRUE;
+    }
+    if (!s->done_service_req) {
+	/*
+	 * Request connection protocol directly, without authentication.
+	 */
+	s->pktout = ssh2_pkt_init(SSH2_MSG_SERVICE_REQUEST);
+	ssh2_pkt_addstring(s->pktout, "ssh-connection");
+	ssh2_pkt_send(ssh, s->pktout);
+	crWaitUntilV(pktin);
+	if (pktin->type == SSH2_MSG_SERVICE_ACCEPT) {
+	    s->we_are_in = TRUE; /* no auth required */
+	} else {
+	    bombout(("Server refused service request"));
+	    crStopV;
+	}
     }
 
     /*
@@ -6032,7 +6561,10 @@ static void do_ssh2_authconn(Ssh ssh, unsigned char *in, int inlen,
      */
     s->username[0] = '\0';
     s->got_username = FALSE;
-    do {
+    bufchain_init(&ssh->banner);
+    ssh->packet_dispatch[SSH2_MSG_USERAUTH_BANNER] =
+	ssh2_msg_userauth_banner;
+    while (!s->we_are_in) {
 	/*
 	 * Get a username.
 	 */
@@ -6050,8 +6582,7 @@ static void do_ssh2_authconn(Ssh ssh, unsigned char *in, int inlen,
 		     * get_line failed to get a username.
 		     * Terminate.
 		     */
-		    logevent("No username provided. Abandoning session.");
-                    ssh_closing((Plug)ssh, NULL, 0, 0);
+		    ssh_disconnect(ssh, "No username provided", NULL, 0, TRUE);
 		    crStopV;
 		}
 	    } else {
@@ -6131,9 +6662,14 @@ static void do_ssh2_authconn(Ssh ssh, unsigned char *in, int inlen,
 	     */
 	    if (!s->gotit)
 		crWaitUntilV(pktin);
-	    while (pktin->type == SSH2_MSG_USERAUTH_BANNER) {
-		char *banner;
-		int size;
+	    /*
+	     * Now is a convenient point to spew any banner material
+	     * that we've accumulated. (This should ensure that when
+	     * we exit the auth loop, we haven't any left to deal
+	     * with.)
+	     */
+	    {
+		int size = bufchain_size(&ssh->banner);
 		/*
 		 * Don't show the banner if we're operating in
 		 * non-verbose non-interactive mode. (It's probably
@@ -6142,12 +6678,13 @@ static void do_ssh2_authconn(Ssh ssh, unsigned char *in, int inlen,
 		 * the banner will screw up processing on the
 		 * output of (say) plink.)
 		 */
-		if (flags & (FLAG_VERBOSE | FLAG_INTERACTIVE)) {
-		    ssh_pkt_getstring(pktin, &banner, &size);
-		    if (banner)
-			c_write_untrusted(ssh, banner, size);
+		if (size && (flags & (FLAG_VERBOSE | FLAG_INTERACTIVE))) {
+		    char *banner = snewn(size, char);
+		    bufchain_fetch(&ssh->banner, banner, size);
+		    c_write_untrusted(ssh, banner, size);
+		    sfree(banner);
 		}
-		crWaitUntilV(pktin);
+		bufchain_clear(&ssh->banner);
 	    }
 	    if (pktin->type == SSH2_MSG_USERAUTH_SUCCESS) {
 		logevent("Access granted");
@@ -6293,19 +6830,11 @@ static void do_ssh2_authconn(Ssh ssh, unsigned char *in, int inlen,
 		    s->p = s->response + 5;
 		    s->nkeys = GET_32BIT(s->p);
 		    s->p += 4;
-		    {
-			char buf[64];
-			sprintf(buf, "Pageant has %d SSH2 keys", s->nkeys);
-			logevent(buf);
-		    }
+		    logeventf(ssh, "Pageant has %d SSH-2 keys", s->nkeys);
 		    for (s->keyi = 0; s->keyi < s->nkeys; s->keyi++) {
 			void *vret;
 
-			{
-			    char buf[64];
-			    sprintf(buf, "Trying Pageant key #%d", s->keyi);
-			    logevent(buf);
-			}
+			logeventf(ssh, "Trying Pageant key #%d", s->keyi);
 			s->pklen = GET_32BIT(s->p);
 			s->p += 4;
 			if (s->publickey_blob &&
@@ -6361,7 +6890,8 @@ static void do_ssh2_authconn(Ssh ssh, unsigned char *in, int inlen,
 			ssh2_pkt_addstring_start(s->pktout);
 			ssh2_pkt_addstring_data(s->pktout, s->pkblob, s->pklen);
 
-			s->siglen = s->pktout->length - 5 + 4 + 20;
+			s->siglen = s->pktout->length - 5 + 4 +
+			    ssh->v2_session_id_len;
                         if (ssh->remote_bugs & BUG_SSH2_PK_SESSIONID)
                             s->siglen -= 4;
 			s->len = 1;       /* message type */
@@ -6380,11 +6910,12 @@ static void do_ssh2_authconn(Ssh ssh, unsigned char *in, int inlen,
 			s->q += 4;
 			/* Now the data to be signed... */
                         if (!(ssh->remote_bugs & BUG_SSH2_PK_SESSIONID)) {
-                            PUT_32BIT(s->q, 20);
+                            PUT_32BIT(s->q, ssh->v2_session_id_len);
                             s->q += 4;
                         }
-			memcpy(s->q, ssh->v2_session_id, 20);
-			s->q += 20;
+			memcpy(s->q, ssh->v2_session_id,
+			       ssh->v2_session_id_len);
+			s->q += ssh->v2_session_id_len;
 			memcpy(s->q, s->pktout->data + 5,
 			       s->pktout->length - 5);
 			s->q += s->pktout->length - 5;
@@ -6520,6 +7051,7 @@ static void do_ssh2_authconn(Ssh ssh, unsigned char *in, int inlen,
 		    continue;
 		}
 
+		c_write_str(ssh, "Using keyboard-interactive authentication.\r\n");
 		s->kbd_inter_running = TRUE;
 		s->curr_prompt = 0;
 	    }
@@ -6603,16 +7135,9 @@ static void do_ssh2_authconn(Ssh ssh, unsigned char *in, int inlen,
 			 * command line which has already failed to
 			 * work). Terminate.
 			 */
-			s->pktout = ssh2_pkt_init(SSH2_MSG_DISCONNECT);
-			ssh2_pkt_adduint32(s->pktout,SSH2_DISCONNECT_BY_APPLICATION);
-			ssh2_pkt_addstring(s->pktout, "No more passwords available"
-					   " to try");
-			ssh2_pkt_addstring(s->pktout, "en");	/* language tag */
-			ssh2_pkt_send_noqueue(ssh, s->pktout);
-			logevent("Unable to authenticate");
-			connection_fatal(ssh->frontend,
-					 "Unable to authenticate");
-                        ssh_closing((Plug)ssh, NULL, 0, 0);
+			ssh_disconnect(ssh, NULL, "Unable to authenticate",
+				       SSH2_DISCONNECT_AUTH_CANCELLED_BY_USER,
+				       FALSE);
 			crStopV;
 		    }
 		} else {
@@ -6686,16 +7211,19 @@ static void do_ssh2_authconn(Ssh ssh, unsigned char *in, int inlen,
 		     * followed by everything so far placed in the
 		     * outgoing packet.
 		     */
-		    sigdata_len = s->pktout->length - 5 + 4 + 20;
+		    sigdata_len = s->pktout->length - 5 + 4 +
+			ssh->v2_session_id_len;
                     if (ssh->remote_bugs & BUG_SSH2_PK_SESSIONID)
                         sigdata_len -= 4;
 		    sigdata = snewn(sigdata_len, unsigned char);
                     p = 0;
                     if (!(ssh->remote_bugs & BUG_SSH2_PK_SESSIONID)) {
-                        PUT_32BIT(sigdata+p, 20);
+                        PUT_32BIT(sigdata+p, ssh->v2_session_id_len);
                         p += 4;
                     }
-		    memcpy(sigdata+p, ssh->v2_session_id, 20); p += 20;
+		    memcpy(sigdata+p, ssh->v2_session_id,
+			   ssh->v2_session_id_len);
+		    p += ssh->v2_session_id_len;
 		    memcpy(sigdata+p, s->pktout->data + 5,
 			   s->pktout->length - 5);
                     p += s->pktout->length - 5;
@@ -6714,20 +7242,16 @@ static void do_ssh2_authconn(Ssh ssh, unsigned char *in, int inlen,
 		}
 	    } 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
-		 * string long enough to make the total length of the two
-		 * packets constant. This should ensure that a passive
-		 * listener doing traffic analyis can't work out the length
-		 * of the password.
+		 * We pad out the password packet to 256 bytes to make
+		 * it harder for an attacker to find the length of the
+		 * user's password.
 		 *
-		 * For this to work, we need an assumption about the
-		 * maximum length of the password packet. I think 256 is
-		 * pretty conservative. Anyone using a password longer than
-		 * that probably doesn't have much to worry about from
+		 * Anyone using a password longer than 256 bytes
+		 * probably doesn't have much to worry about from
 		 * people who find out how long their password is!
 		 */
 		s->pktout = ssh2_pkt_init(SSH2_MSG_USERAUTH_REQUEST);
+		s->pktout->forcepad = 256;
 		ssh2_pkt_addstring(s->pktout, s->username);
 		ssh2_pkt_addstring(s->pktout, "ssh-connection");	/* service requested */
 		ssh2_pkt_addstring(s->pktout, "password");
@@ -6736,46 +7260,13 @@ static void do_ssh2_authconn(Ssh ssh, unsigned char *in, int inlen,
 		ssh2_pkt_addstring(s->pktout, s->password);
 		memset(s->password, 0, sizeof(s->password));
 		end_log_omission(ssh, s->pktout);
-		ssh2_pkt_defer(ssh, s->pktout);
-		/*
-		 * We'll include a string that's an exact multiple of the
-		 * cipher block size. If the cipher is NULL for some
-		 * reason, we don't do this trick at all because we gain
-		 * nothing by it.
-		 */
-		if (ssh->cscipher) {
-		    int stringlen, i;
-
-		    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
-			 * exactly the length we want it. The
-			 * compression-disabling routine should
-			 * return an integer indicating how many
-			 * bytes we should adjust our string length
-			 * by.
-			 */
-			stringlen -= 
-			    ssh->cscomp->disable_compression(ssh->cs_comp_ctx);
-		    }
-		    s->pktout = ssh2_pkt_init(SSH2_MSG_IGNORE);
-		    ssh2_pkt_addstring_start(s->pktout);
-		    for (i = 0; i < stringlen; i++) {
-			char c = (char) random_byte();
-			ssh2_pkt_addstring_data(s->pktout, &c, 1);
-		    }
-		    ssh2_pkt_defer(ssh, s->pktout);
-		}
-		ssh_pkt_defersend(ssh);
+		ssh2_pkt_send(ssh, s->pktout);
 		logevent("Sent password");
 		s->type = AUTH_TYPE_PASSWORD;
 	    } else if (s->method == AUTH_KEYBOARD_INTERACTIVE) {
 		if (s->curr_prompt == 0) {
 		    s->pktout = ssh2_pkt_init(SSH2_MSG_USERAUTH_INFO_RESPONSE);
+		    s->pktout->forcepad = 256;
 		    ssh2_pkt_adduint32(s->pktout, s->num_prompts);
 		}
 		if (s->need_pw) {      /* only add pw if we just got one! */
@@ -6800,26 +7291,18 @@ static void do_ssh2_authconn(Ssh ssh, unsigned char *in, int inlen,
 		}
 		s->type = AUTH_TYPE_KEYBOARD_INTERACTIVE;
 	    } else {
-		c_write_str(ssh, "No supported authentication methods"
-			    " left to try!\r\n");
-		logevent("No supported authentications offered."
-			 " Disconnecting");
-		s->pktout = ssh2_pkt_init(SSH2_MSG_DISCONNECT);
-		ssh2_pkt_adduint32(s->pktout, SSH2_DISCONNECT_BY_APPLICATION);
-		ssh2_pkt_addstring(s->pktout, "No supported authentication"
-				   " methods available");
-		ssh2_pkt_addstring(s->pktout, "en");	/* language tag */
-		ssh2_pkt_send_noqueue(ssh, s->pktout);
-                ssh_closing((Plug)ssh, NULL, 0, 0);
+		ssh_disconnect(ssh, NULL,
+			       "No supported authentication methods available",
+			       SSH2_DISCONNECT_NO_MORE_AUTH_METHODS_AVAILABLE,
+			       FALSE);
 		crStopV;
 	    }
 	}
-    } while (!s->we_are_in);
+    }
+    ssh->packet_dispatch[SSH2_MSG_USERAUTH_BANNER] = NULL;
 
     /*
-     * Now we're authenticated for the connection protocol. The
-     * connection protocol will automatically have started at this
-     * point; there's no need to send SERVICE_REQUEST.
+     * Now the connection protocol has started, one way or another.
      */
 
     ssh->channels = newtree234(ssh_channelcmp);
@@ -6845,7 +7328,7 @@ static void do_ssh2_authconn(Ssh ssh, unsigned char *in, int inlen,
 	ssh2_pkt_adduint32(s->pktout, ssh->mainchan->localid);
 	ssh->mainchan->v.v2.locwindow = OUR_V2_WINSIZE;
 	ssh2_pkt_adduint32(s->pktout, ssh->mainchan->v.v2.locwindow);/* our window size */
-	ssh2_pkt_adduint32(s->pktout, 0x4000UL);      /* our max pkt size */
+	ssh2_pkt_adduint32(s->pktout, OUR_V2_MAXPKT);    /* our max pkt size */
 	ssh2_pkt_send(ssh, s->pktout);
 	crWaitUntilV(pktin);
 	if (pktin->type != SSH2_MSG_CHANNEL_OPEN_CONFIRMATION) {
@@ -6858,6 +7341,7 @@ static void do_ssh2_authconn(Ssh ssh, unsigned char *in, int inlen,
 	    crStopV;
 	}
 	ssh->mainchan->remoteid = ssh_pkt_getuint32(pktin);
+	ssh->mainchan->halfopen = FALSE;
 	ssh->mainchan->type = CHAN_MAINSESSION;
 	ssh->mainchan->closes = 0;
 	ssh->mainchan->v.v2.remwindow = ssh_pkt_getuint32(pktin);
@@ -6902,7 +7386,16 @@ static void do_ssh2_authconn(Ssh ssh, unsigned char *in, int inlen,
 	ssh2_pkt_addbool(s->pktout, 1);	       /* want reply */
 	ssh2_pkt_addbool(s->pktout, 0);	       /* many connections */
 	ssh2_pkt_addstring(s->pktout, proto);
+	/*
+	 * Note that while we blank the X authentication data here, we don't
+	 * take any special action to blank the start of an X11 channel,
+	 * so using MIT-MAGIC-COOKIE-1 and actually opening an X connection
+	 * without having session blanking enabled is likely to leak your
+	 * cookie into the log.
+	 */
+	dont_log_password(ssh, s->pktout, PKTLOG_BLANK);
 	ssh2_pkt_addstring(s->pktout, data);
+	end_log_omission(ssh, s->pktout);
 	ssh2_pkt_adduint32(s->pktout, x11_get_screen_number(ssh->cfg.x11_display));
 	ssh2_pkt_send(ssh, s->pktout);
 
@@ -6971,9 +7464,11 @@ static void do_ssh2_authconn(Ssh ssh, unsigned char *in, int inlen,
 	ssh2_pkt_adduint32(s->pktout, 0);	       /* pixel width */
 	ssh2_pkt_adduint32(s->pktout, 0);	       /* pixel height */
 	ssh2_pkt_addstring_start(s->pktout);
-	ssh2_pkt_addbyte(s->pktout, 128);	       /* TTY_OP_ISPEED */
+	parse_ttymodes(ssh, ssh->cfg.ttymodes,
+		       ssh2_send_ttymode, (void *)s->pktout);
+	ssh2_pkt_addbyte(s->pktout, SSH2_TTY_OP_ISPEED);
 	ssh2_pkt_adduint32(s->pktout, ssh->ispeed);
-	ssh2_pkt_addbyte(s->pktout, 129);	       /* TTY_OP_OSPEED */
+	ssh2_pkt_addbyte(s->pktout, SSH2_TTY_OP_OSPEED);
 	ssh2_pkt_adduint32(s->pktout, ssh->ospeed);
 	ssh2_pkt_addstring_data(s->pktout, "\0", 1); /* TTY_OP_END */
 	ssh2_pkt_send(ssh, s->pktout);
@@ -7078,6 +7573,7 @@ static void do_ssh2_authconn(Ssh ssh, unsigned char *in, int inlen,
 	} else {
 	    subsys = ssh->cfg.ssh_subsys;
 	    cmd = ssh->cfg.remote_cmd_ptr;
+	    if (!cmd) cmd = ssh->cfg.remote_cmd;
 	}
 
 	s->pktout = ssh2_pkt_init(SSH2_MSG_CHANNEL_REQUEST);
@@ -7162,30 +7658,8 @@ static void do_ssh2_authconn(Ssh ssh, unsigned char *in, int inlen,
 	    /*
 	     * Try to send data on all channels if we can.
 	     */
-	    for (i = 0; NULL != (c = index234(ssh->channels, i)); i++) {
-		int bufsize;
-		if (c->closes)
-		    continue;	       /* don't send on closing channels */
-		bufsize = ssh2_try_send(c);
-		if (bufsize == 0) {
-		    switch (c->type) {
-		      case CHAN_MAINSESSION:
-			/* stdin need not receive an unthrottle
-			 * notification since it will be polled */
-			break;
-		      case CHAN_X11:
-			x11_unthrottle(c->u.x11.s);
-			break;
-		      case CHAN_AGENT:
-			/* agent sockets are request/response and need no
-			 * buffer management */
-			break;
-		      case CHAN_SOCKDATA:
-			pfd_unthrottle(c->u.pfd.s);
-			break;
-		    }
-		}
-	    }
+	    for (i = 0; NULL != (c = index234(ssh->channels, i)); i++)
+		ssh2_try_send_and_unthrottle(c);
 	}
     }
 
@@ -7193,9 +7667,9 @@ static void do_ssh2_authconn(Ssh ssh, unsigned char *in, int inlen,
 }
 
 /*
- * Handlers for SSH2 messages that might arrive at any moment.
+ * Handlers for SSH-2 messages that might arrive at any moment.
  */
-void ssh2_msg_disconnect(Ssh ssh, struct Packet *pktin)
+static void ssh2_msg_disconnect(Ssh ssh, struct Packet *pktin)
 {
     /* log reason code in disconnect message */
     char *buf, *msg;
@@ -7224,10 +7698,10 @@ void ssh2_msg_disconnect(Ssh ssh, struct Packet *pktin)
     sfree(buf);
 }
 
-void ssh2_msg_debug(Ssh ssh, struct Packet *pktin)
+static void ssh2_msg_debug(Ssh ssh, struct Packet *pktin)
 {
     /* log the debug message */
-    char *buf, *msg;
+    char *msg;
     int msglen;
     int always_display;
 
@@ -7235,12 +7709,10 @@ void ssh2_msg_debug(Ssh ssh, struct Packet *pktin)
     always_display = ssh2_pkt_getbool(pktin);
     ssh_pkt_getstring(pktin, &msg, &msglen);
 
-    buf = dupprintf("Remote debug message: %.*s", msglen, msg);
-    logevent(buf);
-    sfree(buf);
+    logeventf(ssh, "Remote debug message: %.*s", msglen, msg);
 }
 
-void ssh2_msg_something_unimplemented(Ssh ssh, struct Packet *pktin)
+static void ssh2_msg_something_unimplemented(Ssh ssh, struct Packet *pktin)
 {
     struct Packet *pktout;
     pktout = ssh2_pkt_init(SSH2_MSG_UNIMPLEMENTED);
@@ -7253,7 +7725,7 @@ void ssh2_msg_something_unimplemented(Ssh ssh, struct Packet *pktin)
 }
 
 /*
- * Handle the top-level SSH2 protocol.
+ * Handle the top-level SSH-2 protocol.
  */
 static void ssh2_protocol_setup(Ssh ssh)
 {
@@ -7307,7 +7779,7 @@ static void ssh2_protocol_setup(Ssh ssh)
      * These special message types we install handlers for.
      */
     ssh->packet_dispatch[SSH2_MSG_DISCONNECT] = ssh2_msg_disconnect;
-    ssh->packet_dispatch[SSH2_MSG_IGNORE] = ssh_msg_ignore; /* shared with ssh1 */
+    ssh->packet_dispatch[SSH2_MSG_IGNORE] = ssh_msg_ignore; /* shared with SSH-1 */
     ssh->packet_dispatch[SSH2_MSG_DEBUG] = ssh2_msg_debug;
 }
 
@@ -7315,15 +7787,19 @@ static void ssh2_timer(void *ctx, long now)
 {
     Ssh ssh = (Ssh)ctx;
 
+    if (ssh->state == SSH_STATE_CLOSED)
+	return;
+
     if (!ssh->kex_in_progress && ssh->cfg.ssh_rekey_time != 0 &&
 	now - ssh->next_rekey >= 0) {
 	do_ssh2_transport(ssh, "timeout", -1, NULL);
     }
 }
 
-static void ssh2_protocol(Ssh ssh, unsigned char *in, int inlen,
+static void ssh2_protocol(Ssh ssh, void *vin, int inlen,
 			  struct Packet *pktin)
 {
+    unsigned char *in = (unsigned char *)vin;
     if (ssh->state == SSH_STATE_CLOSED)
 	return;
 
@@ -7391,6 +7867,8 @@ static const char *ssh_init(void *frontend_handle, void **backend_handle,
     ssh->kex_ctx = NULL;
     ssh->hostkey = NULL;
     ssh->exitcode = -1;
+    ssh->close_expected = FALSE;
+    ssh->clean_exit = FALSE;
     ssh->state = SSH_STATE_PREPACKET;
     ssh->size_needed = FALSE;
     ssh->eof_needed = FALSE;
@@ -7416,6 +7894,8 @@ static const char *ssh_init(void *frontend_handle, void **backend_handle,
     ssh->do_ssh1_login_state = NULL;
     ssh->do_ssh2_transport_state = NULL;
     ssh->do_ssh2_authconn_state = NULL;
+    ssh->v_c = NULL;
+    ssh->v_s = NULL;
     ssh->mainchan = NULL;
     ssh->throttled_all = 0;
     ssh->v1_stdout_throttling = 0;
@@ -7424,6 +7904,8 @@ static const char *ssh_init(void *frontend_handle, void **backend_handle,
     ssh->queueing = FALSE;
     ssh->qhead = ssh->qtail = NULL;
     ssh->deferred_rekey_reason = NULL;
+    bufchain_init(&ssh->queued_incoming_data);
+    ssh->frozen = FALSE;
 
     *backend_handle = ssh;
 
@@ -7541,15 +8023,18 @@ static void ssh_free(void *handle)
     sfree(ssh->do_ssh1_login_state);
     sfree(ssh->do_ssh2_transport_state);
     sfree(ssh->do_ssh2_authconn_state);
+    sfree(ssh->v_c);
+    sfree(ssh->v_s);
     if (ssh->crcda_ctx) {
 	crcda_free_context(ssh->crcda_ctx);
 	ssh->crcda_ctx = NULL;
     }
     if (ssh->s)
-	ssh_do_close(ssh);
+	ssh_do_close(ssh, TRUE);
     expire_timer_context(ssh);
     if (ssh->pinger)
 	pinger_free(ssh->pinger);
+    bufchain_clear(&ssh->queued_incoming_data);
     sfree(ssh);
 
     random_unref();
@@ -7565,7 +8050,8 @@ static void ssh_reconfig(void *handle, Config *cfg)
     unsigned long old_max_data_size;
 
     pinger_reconfig(ssh->pinger, &ssh->cfg, cfg);
-    ssh_setup_portfwd(ssh, cfg);
+    if (ssh->portfwds)
+	ssh_setup_portfwd(ssh, cfg);
 
     if (ssh->cfg.ssh_rekey_time != cfg->ssh_rekey_time &&
 	cfg->ssh_rekey_time != 0) {
@@ -7612,7 +8098,7 @@ static void ssh_reconfig(void *handle, Config *cfg)
 }
 
 /*
- * Called to send data down the Telnet connection.
+ * Called to send data down the SSH connection.
  */
 static int ssh_send(void *handle, char *buf, int len)
 {
@@ -7769,7 +8255,7 @@ static const struct telnet_special *ssh_get_specials(void *handle)
 }
 
 /*
- * Send Telnet special codes. TS_EOF is useful for `plink', so you
+ * Send special codes. TS_EOF is useful for `plink', so you
  * can send an EOF and collect resulting output (e.g. `plink
  * hostname sort').
  */
@@ -7794,6 +8280,7 @@ static void ssh_special(void *handle, Telnet_Special code)
 	    struct Packet *pktout = ssh2_pkt_init(SSH2_MSG_CHANNEL_EOF);
 	    ssh2_pkt_adduint32(pktout, ssh->mainchan->remoteid);
 	    ssh2_pkt_send(ssh, pktout);
+            ssh->send_ok = 0;          /* now stop trying to read from stdin */
 	}
 	logevent("Sent EOF message");
     } else if (code == TS_PING || code == TS_NOP) {
@@ -7815,7 +8302,7 @@ static void ssh_special(void *handle, Telnet_Special code)
 	if (ssh->state == SSH_STATE_CLOSED
 	    || ssh->state == SSH_STATE_PREPACKET) return;
 	if (ssh->version == 1) {
-	    logevent("Unable to send BREAK signal in SSH1");
+	    logevent("Unable to send BREAK signal in SSH-1");
 	} else if (ssh->mainchan) {
 	    pktout = ssh2_pkt_init(SSH2_MSG_CHANNEL_REQUEST);
 	    ssh2_pkt_adduint32(pktout, ssh->mainchan->remoteid);
@@ -7867,7 +8354,7 @@ void *new_sock_channel(void *handle, Socket s)
     c->ssh = ssh;
 
     if (c) {
-	c->remoteid = -1;	       /* to be set when open confirmed */
+	c->halfopen = TRUE;
 	c->localid = alloc_channel_id(ssh);
 	c->closes = 0;
 	c->type = CHAN_SOCKDATA_DORMANT;/* identify channel type */
@@ -7917,7 +8404,7 @@ void ssh_send_port_open(void *channel, char *hostname, int port, char *org)
 	ssh2_pkt_adduint32(pktout, c->localid);
 	c->v.v2.locwindow = OUR_V2_WINSIZE;
 	ssh2_pkt_adduint32(pktout, c->v.v2.locwindow);/* our window size */
-	ssh2_pkt_adduint32(pktout, 0x4000UL);      /* our max pkt size */
+	ssh2_pkt_adduint32(pktout, OUR_V2_MAXPKT);      /* our max pkt size */
 	ssh2_pkt_addstring(pktout, hostname);
 	ssh2_pkt_adduint32(pktout, port);
 	/*