Loose end from timing shakeup: sshrand.c is now a client of
[u/mdw/putty] / ssh.c
diff --git a/ssh.c b/ssh.c
index 3426098..07d06f1 100644 (file)
--- a/ssh.c
+++ b/ssh.c
@@ -517,6 +517,7 @@ struct Packet {
     unsigned char *body;
     long savedpos;
     long maxlen;
+    long encrypted_len;                       /* for SSH2 total-size counting */
 
     /*
      * State associated with packet logging
@@ -543,6 +544,9 @@ static void ssh_do_close(Ssh ssh);
 static unsigned long ssh_pkt_getuint32(struct Packet *pkt);
 static int ssh2_pkt_getbool(struct Packet *pkt);
 static void ssh_pkt_getstring(struct Packet *pkt, char **p, int *length);
+static void ssh2_timer(void *ctx, long now);
+static int do_ssh2_transport(Ssh ssh, unsigned char *in, int inlen,
+                            struct Packet *pktin);
 
 struct rdpkt1_state_tag {
     long len, pad, biglen, to_read;
@@ -698,8 +702,24 @@ struct ssh_tag {
      * with at any time.
      */
     handler_fn_t packet_dispatch[256];
+
+    /*
+     * This module deals with sending keepalives.
+     */
+    Pinger pinger;
+
+    /*
+     * Track incoming and outgoing data sizes and time, for
+     * size-based rekeys.
+     */
+    unsigned long incoming_data_size, outgoing_data_size, deferred_data_size;
+    int kex_in_progress;
+    long next_rekey;
 };
 
+#define MAX_DATA_BEFORE_REKEY (0x40000000UL)
+#define REKEY_TIMEOUT (3600 * TICKSPERSEC)
+
 #define logevent(s) logevent(ssh->frontend, s)
 
 /* logevent, only printf-formatted. */
@@ -1094,6 +1114,8 @@ static struct Packet *ssh2_rdpkt(Ssh ssh, unsigned char **data, int *datalen)
                               st->pktin->data + st->cipherblk,
                               st->packetlen - st->cipherblk);
 
+    st->pktin->encrypted_len = st->packetlen;
+
     /*
      * Check the MAC.
      */
@@ -1587,6 +1609,8 @@ static int ssh2_pkt_construct(Ssh ssh, struct Packet *pkt)
        ssh->cscipher->encrypt(ssh->cs_cipher_ctx,
                               pkt->data, pkt->length + padding);
 
+    pkt->encrypted_len = pkt->length + padding;
+
     /* Ready-to-send packet starts at pkt->data. We return length. */
     return pkt->length + padding + maclen;
 }
@@ -1631,6 +1655,13 @@ static void ssh2_pkt_send_noqueue(Ssh ssh, struct Packet *pkt)
     backlog = sk_write(ssh->s, (char *)pkt->data, len);
     if (backlog > SSH_MAX_BACKLOG)
        ssh_throttle_all(ssh, 1, backlog);
+
+    ssh->outgoing_data_size += pkt->encrypted_len;
+    if (!ssh->kex_in_progress &&
+       ssh->outgoing_data_size > MAX_DATA_BEFORE_REKEY)
+       do_ssh2_transport(ssh, "Initiating key re-exchange "
+                         "(too much data sent)", -1, NULL);
+
     ssh_free_packet(pkt);
 }
 
@@ -1648,6 +1679,7 @@ static void ssh2_pkt_defer_noqueue(Ssh ssh, struct Packet *pkt)
     }
     memcpy(ssh->deferred_send_data + ssh->deferred_len, pkt->data, len);
     ssh->deferred_len += len;
+    ssh->deferred_data_size += pkt->encrypted_len;
     ssh_free_packet(pkt);
 }
 
@@ -1713,6 +1745,13 @@ static void ssh_pkt_defersend(Ssh ssh)
     ssh->deferred_send_data = NULL;
     if (backlog > SSH_MAX_BACKLOG)
        ssh_throttle_all(ssh, 1, backlog);
+
+    ssh->outgoing_data_size += ssh->deferred_data_size;
+    if (!ssh->kex_in_progress &&
+       ssh->outgoing_data_size > MAX_DATA_BEFORE_REKEY)
+       do_ssh2_transport(ssh, "Initiating key re-exchange "
+                         "(too much data sent)", -1, NULL);
+    ssh->deferred_data_size = 0;
 }
 
 /*
@@ -2157,6 +2196,7 @@ static int do_ssh_init(Ssh ssh, unsigned char c)
     }
     update_specials_menu(ssh->frontend);
     ssh->state = SSH_STATE_BEFORE_SIZE;
+    ssh->pinger = pinger_new(&ssh->cfg, &ssh_backend, ssh);
 
     sfree(s->vstring);
 
@@ -2216,6 +2256,7 @@ static void ssh_do_close(Ssh ssh)
     if (ssh->s) {
         sk_close(ssh->s);
         ssh->s = NULL;
+       notify_remote_exit(ssh->frontend);
     }
     /*
      * Now we must shut down any port and X forwardings going
@@ -2327,6 +2368,7 @@ static const char *connect_to_host(Ssh ssh, char *host, int port,
                            0, 1, nodelay, keepalive, (Plug) ssh, &ssh->cfg);
     if ((err = sk_socket_error(ssh->s)) != NULL) {
        ssh->s = NULL;
+       notify_remote_exit(ssh->frontend);
        return err;
     }
 
@@ -2534,8 +2576,6 @@ static int do_ssh1_login(Ssh ssh, unsigned char *in, int inlen,
 
     crBegin(ssh->do_ssh1_login_crstate);
 
-    random_init();
-
     if (!pktin)
        crWaitUntil(pktin);
 
@@ -3438,11 +3478,339 @@ void sshfwd_unthrottle(struct ssh_channel *c, int bufsize)
     }
 }
 
+static void ssh1_smsg_stdout_stderr_data(Ssh ssh, struct Packet *pktin)
+{
+    char *string;
+    int stringlen, bufsize;
+
+    ssh_pkt_getstring(pktin, &string, &stringlen);
+    if (string == NULL) {
+       bombout(("Incoming terminal data packet was badly formed"));
+       return;
+    }
+
+    bufsize = from_backend(ssh->frontend, pktin->type == SSH1_SMSG_STDERR_DATA,
+                          string, stringlen);
+    if (!ssh->v1_stdout_throttling && bufsize > SSH1_BUFFER_LIMIT) {
+       ssh->v1_stdout_throttling = 1;
+       ssh1_throttle(ssh, +1);
+    }
+}
+
+static void ssh1_smsg_x11_open(Ssh ssh, struct Packet *pktin)
+{
+    /* Remote side is trying to open a channel to talk to our
+     * X-Server. Give them back a local channel number. */
+    struct ssh_channel *c;
+    int remoteid = ssh_pkt_getuint32(pktin);
+
+    logevent("Received X11 connect request");
+    /* Refuse if X11 forwarding is disabled. */
+    if (!ssh->X11_fwd_enabled) {
+       send_packet(ssh, SSH1_MSG_CHANNEL_OPEN_FAILURE,
+                   PKT_INT, remoteid, PKT_END);
+       logevent("Rejected X11 connect request");
+    } else {
+       c = snew(struct ssh_channel);
+       c->ssh = ssh;
+
+       if (x11_init(&c->u.x11.s, ssh->cfg.x11_display, c,
+                    ssh->x11auth, NULL, -1, &ssh->cfg) != NULL) {
+           logevent("Opening X11 forward connection failed");
+           sfree(c);
+           send_packet(ssh, SSH1_MSG_CHANNEL_OPEN_FAILURE,
+                       PKT_INT, remoteid, PKT_END);
+       } else {
+           logevent
+               ("Opening X11 forward connection succeeded");
+           c->remoteid = remoteid;
+           c->localid = alloc_channel_id(ssh);
+           c->closes = 0;
+           c->v.v1.throttling = 0;
+           c->type = CHAN_X11; /* identify channel type */
+           add234(ssh->channels, c);
+           send_packet(ssh, SSH1_MSG_CHANNEL_OPEN_CONFIRMATION,
+                       PKT_INT, c->remoteid, PKT_INT,
+                       c->localid, PKT_END);
+           logevent("Opened X11 forward channel");
+       }
+    }
+}
+
+static void ssh1_smsg_agent_open(Ssh ssh, struct Packet *pktin)
+{
+    /* Remote side is trying to open a channel to talk to our
+     * agent. Give them back a local channel number. */
+    struct ssh_channel *c;
+    int remoteid = ssh_pkt_getuint32(pktin);
+
+    /* Refuse if agent forwarding is disabled. */
+    if (!ssh->agentfwd_enabled) {
+       send_packet(ssh, SSH1_MSG_CHANNEL_OPEN_FAILURE,
+                   PKT_INT, remoteid, PKT_END);
+    } else {
+       c = snew(struct ssh_channel);
+       c->ssh = ssh;
+       c->remoteid = remoteid;
+       c->localid = alloc_channel_id(ssh);
+       c->closes = 0;
+       c->v.v1.throttling = 0;
+       c->type = CHAN_AGENT;   /* identify channel type */
+       c->u.a.lensofar = 0;
+       add234(ssh->channels, c);
+       send_packet(ssh, SSH1_MSG_CHANNEL_OPEN_CONFIRMATION,
+                   PKT_INT, c->remoteid, PKT_INT, c->localid,
+                   PKT_END);
+    }
+}
+
+static void ssh1_msg_port_open(Ssh ssh, struct Packet *pktin)
+{
+    /* Remote side is trying to open a channel to talk to a
+     * forwarded port. Give them back a local channel number. */
+    struct ssh_channel *c;
+    struct ssh_rportfwd pf;
+    int remoteid;
+    int hostsize, port;
+    char *host, buf[1024];
+    const char *e;
+    c = snew(struct ssh_channel);
+    c->ssh = ssh;
+
+    remoteid = ssh_pkt_getuint32(pktin);
+    ssh_pkt_getstring(pktin, &host, &hostsize);
+    port = ssh_pkt_getuint32(pktin);
+
+    if (hostsize >= lenof(pf.dhost))
+       hostsize = lenof(pf.dhost)-1;
+    memcpy(pf.dhost, host, hostsize);
+    pf.dhost[hostsize] = '\0';
+    pf.dport = port;
+
+    if (find234(ssh->rportfwds, &pf, NULL) == NULL) {
+       sprintf(buf, "Rejected remote port open request for %s:%d",
+               pf.dhost, port);
+       logevent(buf);
+       send_packet(ssh, SSH1_MSG_CHANNEL_OPEN_FAILURE,
+                   PKT_INT, remoteid, PKT_END);
+    } else {
+       sprintf(buf, "Received remote port open request for %s:%d",
+               pf.dhost, port);
+       logevent(buf);
+       e = pfd_newconnect(&c->u.pfd.s, pf.dhost, port,
+                          c, &ssh->cfg);
+       if (e != NULL) {
+           char buf[256];
+           sprintf(buf, "Port open failed: %s", e);
+           logevent(buf);
+           sfree(c);
+           send_packet(ssh, SSH1_MSG_CHANNEL_OPEN_FAILURE,
+                       PKT_INT, remoteid, PKT_END);
+       } else {
+           c->remoteid = remoteid;
+           c->localid = alloc_channel_id(ssh);
+           c->closes = 0;
+           c->v.v1.throttling = 0;
+           c->type = CHAN_SOCKDATA;    /* identify channel type */
+           add234(ssh->channels, c);
+           send_packet(ssh, SSH1_MSG_CHANNEL_OPEN_CONFIRMATION,
+                       PKT_INT, c->remoteid, PKT_INT,
+                       c->localid, PKT_END);
+           logevent("Forwarded port opened successfully");
+       }
+    }
+}
+
+static void ssh1_msg_channel_open_confirmation(Ssh ssh, struct Packet *pktin)
+{
+    unsigned int remoteid = ssh_pkt_getuint32(pktin);
+    unsigned int localid = ssh_pkt_getuint32(pktin);
+    struct ssh_channel *c;
+
+    c = find234(ssh->channels, &remoteid, ssh_channelfind);
+    if (c && c->type == CHAN_SOCKDATA_DORMANT) {
+       c->remoteid = localid;
+       c->type = CHAN_SOCKDATA;
+       c->v.v1.throttling = 0;
+       pfd_confirm(c->u.pfd.s);
+    }
+
+    if (c && c->closes) {
+       /*
+        * We have a pending close on this channel,
+        * which we decided on before the server acked
+        * the channel open. So now we know the
+        * remoteid, we can close it again.
+        */
+       send_packet(ssh, SSH1_MSG_CHANNEL_CLOSE,
+                   PKT_INT, c->remoteid, PKT_END);
+    }
+}
+
+static void ssh1_msg_channel_open_failure(Ssh ssh, struct Packet *pktin)
+{
+    unsigned int remoteid = ssh_pkt_getuint32(pktin);
+    struct ssh_channel *c;
+
+    c = find234(ssh->channels, &remoteid, ssh_channelfind);
+    if (c && c->type == CHAN_SOCKDATA_DORMANT) {
+       logevent("Forwarded connection refused by server");
+       pfd_close(c->u.pfd.s);
+       del234(ssh->channels, c);
+       sfree(c);
+    }
+}
+
+static void ssh1_msg_channel_close(Ssh ssh, struct Packet *pktin)
+{
+    /* Remote side closes a channel. */
+    unsigned i = ssh_pkt_getuint32(pktin);
+    struct ssh_channel *c;
+    c = find234(ssh->channels, &i, ssh_channelfind);
+    if (c && ((int)c->remoteid) != -1) {
+       int closetype;
+       closetype =
+           (pktin->type == SSH1_MSG_CHANNEL_CLOSE ? 1 : 2);
+
+       if ((c->closes == 0) && (c->type == CHAN_X11)) {
+           logevent("Forwarded X11 connection terminated");
+           assert(c->u.x11.s != NULL);
+           x11_close(c->u.x11.s);
+           c->u.x11.s = NULL;
+       }
+       if ((c->closes == 0) && (c->type == CHAN_SOCKDATA)) {
+           logevent("Forwarded port closed");
+           assert(c->u.pfd.s != NULL);
+           pfd_close(c->u.pfd.s);
+           c->u.pfd.s = NULL;
+       }
+
+       c->closes |= (closetype << 2);   /* seen this message */
+       if (!(c->closes & closetype)) {
+           send_packet(ssh, pktin->type, PKT_INT, c->remoteid,
+                       PKT_END);
+           c->closes |= closetype;      /* sent it too */
+       }
+
+       if (c->closes == 15) {
+           del234(ssh->channels, c);
+           sfree(c);
+       }
+    } else {
+       bombout(("Received CHANNEL_CLOSE%s for %s channel %d\n",
+                pktin->type == SSH1_MSG_CHANNEL_CLOSE ? "" :
+                "_CONFIRMATION", c ? "half-open" : "nonexistent",
+                i));
+    }
+}
+
+static void ssh1_msg_channel_data(Ssh ssh, struct Packet *pktin)
+{
+    /* Data sent down one of our channels. */
+    int i = ssh_pkt_getuint32(pktin);
+    char *p;
+    int len;
+    struct ssh_channel *c;
+
+    ssh_pkt_getstring(pktin, &p, &len);
+
+    c = find234(ssh->channels, &i, ssh_channelfind);
+    if (c) {
+       int bufsize = 0;
+       switch (c->type) {
+         case CHAN_X11:
+           bufsize = x11_send(c->u.x11.s, p, len);
+           break;
+         case CHAN_SOCKDATA:
+           bufsize = pfd_send(c->u.pfd.s, p, len);
+           break;
+         case CHAN_AGENT:
+           /* Data for an agent message. Buffer it. */
+           while (len > 0) {
+               if (c->u.a.lensofar < 4) {
+                   int l = min(4 - c->u.a.lensofar, len);
+                   memcpy(c->u.a.msglen + c->u.a.lensofar, p,
+                          l);
+                   p += l;
+                   len -= l;
+                   c->u.a.lensofar += l;
+               }
+               if (c->u.a.lensofar == 4) {
+                   c->u.a.totallen =
+                       4 + GET_32BIT(c->u.a.msglen);
+                   c->u.a.message = snewn(c->u.a.totallen,
+                                          unsigned char);
+                   memcpy(c->u.a.message, c->u.a.msglen, 4);
+               }
+               if (c->u.a.lensofar >= 4 && len > 0) {
+                   int l =
+                       min(c->u.a.totallen - c->u.a.lensofar,
+                           len);
+                   memcpy(c->u.a.message + c->u.a.lensofar, p,
+                          l);
+                   p += l;
+                   len -= l;
+                   c->u.a.lensofar += l;
+               }
+               if (c->u.a.lensofar == c->u.a.totallen) {
+                   void *reply;
+                   int replylen;
+                   if (agent_query(c->u.a.message,
+                                   c->u.a.totallen,
+                                   &reply, &replylen,
+                                   ssh_agentf_callback, c))
+                       ssh_agentf_callback(c, reply, replylen);
+                   sfree(c->u.a.message);
+                   c->u.a.lensofar = 0;
+               }
+           }
+           bufsize = 0;   /* agent channels never back up */
+           break;
+       }
+       if (!c->v.v1.throttling && bufsize > SSH1_BUFFER_LIMIT) {
+           c->v.v1.throttling = 1;
+           ssh1_throttle(ssh, +1);
+       }
+    }
+}
+
+static void ssh1_smsg_exit_status(Ssh ssh, struct Packet *pktin)
+{
+    char buf[100];
+    ssh->exitcode = ssh_pkt_getuint32(pktin);
+    sprintf(buf, "Server sent command exit status %d",
+           ssh->exitcode);
+    logevent(buf);
+    send_packet(ssh, SSH1_CMSG_EXIT_CONFIRMATION, PKT_END);
+    /*
+     * In case `helpful' firewalls or proxies tack
+     * extra human-readable text on the end of the
+     * session which we might mistake for another
+     * encrypted packet, we close the session once
+     * we've sent EXIT_CONFIRMATION.
+     */
+    ssh_closing((Plug)ssh, NULL, 0, 0);
+}
+
 static void do_ssh1_connection(Ssh ssh, unsigned char *in, int inlen,
                               struct Packet *pktin)
 {
     crBegin(ssh->do_ssh1_connection_crstate);
 
+    ssh->packet_dispatch[SSH1_SMSG_STDOUT_DATA] = 
+       ssh->packet_dispatch[SSH1_SMSG_STDERR_DATA] =
+       ssh1_smsg_stdout_stderr_data;
+
+    ssh->packet_dispatch[SSH1_MSG_CHANNEL_OPEN_CONFIRMATION] =
+       ssh1_msg_channel_open_confirmation;
+    ssh->packet_dispatch[SSH1_MSG_CHANNEL_OPEN_FAILURE] =
+       ssh1_msg_channel_open_failure;
+    ssh->packet_dispatch[SSH1_MSG_CHANNEL_CLOSE] =
+       ssh->packet_dispatch[SSH1_MSG_CHANNEL_CLOSE_CONFIRMATION] =
+       ssh1_msg_channel_close;
+    ssh->packet_dispatch[SSH1_MSG_CHANNEL_DATA] = ssh1_msg_channel_data;
+    ssh->packet_dispatch[SSH1_SMSG_EXIT_STATUS] = ssh1_smsg_exit_status;
+
     if (ssh->cfg.agentfwd && agent_exists()) {
        logevent("Requesting agent forwarding");
        send_packet(ssh, SSH1_CMSG_AGENT_REQUEST_FORWARDING, PKT_END);
@@ -3458,6 +3826,7 @@ static void do_ssh1_connection(Ssh ssh, unsigned char *in, int inlen,
        } else {
            logevent("Agent forwarding enabled");
            ssh->agentfwd_enabled = TRUE;
+           ssh->packet_dispatch[SSH1_SMSG_AGENT_OPEN] = ssh1_smsg_agent_open;
        }
     }
 
@@ -3488,6 +3857,7 @@ static void do_ssh1_connection(Ssh ssh, unsigned char *in, int inlen,
        } else {
            logevent("X11 forwarding enabled");
            ssh->X11_fwd_enabled = TRUE;
+           ssh->packet_dispatch[SSH1_SMSG_X11_OPEN] = ssh1_smsg_x11_open;
        }
     }
 
@@ -3637,8 +4007,12 @@ static void do_ssh1_connection(Ssh ssh, unsigned char *in, int inlen,
                        } else if (pktin->type == SSH1_SMSG_FAILURE) {
                            c_write_str(ssh, "Server refused port"
                                        " forwarding\r\n");
+                           logevent("Server refused this port forwarding");
+                       } else {
+                           logevent("Remote port forwarding enabled");
+                           ssh->packet_dispatch[SSH1_MSG_PORT_OPEN] =
+                               ssh1_msg_port_open;
                        }
-                       logevent("Remote port forwarding enabled");
                    }
                }
                sfree(sportdesc);
@@ -3730,313 +4104,20 @@ static void do_ssh1_connection(Ssh ssh, unsigned char *in, int inlen,
     ssh->send_ok = 1;
     ssh->channels = newtree234(ssh_channelcmp);
     while (1) {
-       crReturnV;
-       if (pktin) {
-           if (pktin->type == SSH1_SMSG_STDOUT_DATA ||
-               pktin->type == SSH1_SMSG_STDERR_DATA) {
-               char *string;
-               int stringlen, bufsize;
-
-               ssh_pkt_getstring(pktin, &string, &stringlen);
-               if (string == NULL) {
-                   bombout(("Incoming terminal data packet was badly formed"));
-                   crStopV;
-               }
-
-               bufsize =
-                   from_backend(ssh->frontend,
-                                pktin->type == SSH1_SMSG_STDERR_DATA,
-                                string, stringlen);
-               if (!ssh->v1_stdout_throttling && bufsize > SSH1_BUFFER_LIMIT) {
-                   ssh->v1_stdout_throttling = 1;
-                   ssh1_throttle(ssh, +1);
-               }
-           } else if (pktin->type == SSH1_MSG_DISCONNECT) {
-                ssh_closing((Plug)ssh, NULL, 0, 0);
-               logevent("Received disconnect request");
-               crStopV;
-           } else if (pktin->type == SSH1_SMSG_X11_OPEN) {
-               /* Remote side is trying to open a channel to talk to our
-                * X-Server. Give them back a local channel number. */
-               struct ssh_channel *c;
-               int remoteid = ssh_pkt_getuint32(pktin);
-
-               logevent("Received X11 connect request");
-               /* Refuse if X11 forwarding is disabled. */
-               if (!ssh->X11_fwd_enabled) {
-                   send_packet(ssh, SSH1_MSG_CHANNEL_OPEN_FAILURE,
-                               PKT_INT, remoteid, PKT_END);
-                   logevent("Rejected X11 connect request");
-               } else {
-                   c = snew(struct ssh_channel);
-                   c->ssh = ssh;
-
-                   if (x11_init(&c->u.x11.s, ssh->cfg.x11_display, c,
-                                ssh->x11auth, NULL, -1, &ssh->cfg) != NULL) {
-                       logevent("Opening X11 forward connection failed");
-                       sfree(c);
-                       send_packet(ssh, SSH1_MSG_CHANNEL_OPEN_FAILURE,
-                                   PKT_INT, remoteid, PKT_END);
-                   } else {
-                       logevent
-                           ("Opening X11 forward connection succeeded");
-                       c->remoteid = remoteid;
-                       c->localid = alloc_channel_id(ssh);
-                       c->closes = 0;
-                       c->v.v1.throttling = 0;
-                       c->type = CHAN_X11;     /* identify channel type */
-                       add234(ssh->channels, c);
-                       send_packet(ssh, SSH1_MSG_CHANNEL_OPEN_CONFIRMATION,
-                                   PKT_INT, c->remoteid, PKT_INT,
-                                   c->localid, PKT_END);
-                       logevent("Opened X11 forward channel");
-                   }
-               }
-           } else if (pktin->type == SSH1_SMSG_AGENT_OPEN) {
-               /* Remote side is trying to open a channel to talk to our
-                * agent. Give them back a local channel number. */
-               struct ssh_channel *c;
-               int remoteid = ssh_pkt_getuint32(pktin);
-
-               /* Refuse if agent forwarding is disabled. */
-               if (!ssh->agentfwd_enabled) {
-                   send_packet(ssh, SSH1_MSG_CHANNEL_OPEN_FAILURE,
-                               PKT_INT, remoteid, PKT_END);
-               } else {
-                   c = snew(struct ssh_channel);
-                   c->ssh = ssh;
-                   c->remoteid = remoteid;
-                   c->localid = alloc_channel_id(ssh);
-                   c->closes = 0;
-                   c->v.v1.throttling = 0;
-                   c->type = CHAN_AGENT;       /* identify channel type */
-                   c->u.a.lensofar = 0;
-                   add234(ssh->channels, c);
-                   send_packet(ssh, SSH1_MSG_CHANNEL_OPEN_CONFIRMATION,
-                               PKT_INT, c->remoteid, PKT_INT, c->localid,
-                               PKT_END);
-               }
-           } else if (pktin->type == SSH1_MSG_PORT_OPEN) {
-               /* Remote side is trying to open a channel to talk to a
-                * forwarded port. Give them back a local channel number. */
-               struct ssh_channel *c;
-               struct ssh_rportfwd pf;
-               int remoteid;
-               int hostsize, port;
-               char *host, buf[1024];
-               const char *e;
-               c = snew(struct ssh_channel);
-               c->ssh = ssh;
-
-               remoteid = ssh_pkt_getuint32(pktin);
-               ssh_pkt_getstring(pktin, &host, &hostsize);
-               port = ssh_pkt_getuint32(pktin);
-
-               if (hostsize >= lenof(pf.dhost))
-                   hostsize = lenof(pf.dhost)-1;
-               memcpy(pf.dhost, host, hostsize);
-               pf.dhost[hostsize] = '\0';
-               pf.dport = port;
-
-               if (find234(ssh->rportfwds, &pf, NULL) == NULL) {
-                   sprintf(buf, "Rejected remote port open request for %s:%d",
-                           pf.dhost, port);
-                   logevent(buf);
-                    send_packet(ssh, SSH1_MSG_CHANNEL_OPEN_FAILURE,
-                                PKT_INT, remoteid, PKT_END);
-               } else {
-                   sprintf(buf, "Received remote port open request for %s:%d",
-                           pf.dhost, port);
-                   logevent(buf);
-                   e = pfd_newconnect(&c->u.pfd.s, pf.dhost, port,
-                                      c, &ssh->cfg);
-                   if (e != NULL) {
-                       char buf[256];
-                       sprintf(buf, "Port open failed: %s", e);
-                       logevent(buf);
-                       sfree(c);
-                       send_packet(ssh, SSH1_MSG_CHANNEL_OPEN_FAILURE,
-                                   PKT_INT, remoteid, PKT_END);
-                   } else {
-                       c->remoteid = remoteid;
-                       c->localid = alloc_channel_id(ssh);
-                       c->closes = 0;
-                       c->v.v1.throttling = 0;
-                       c->type = CHAN_SOCKDATA;        /* identify channel type */
-                       add234(ssh->channels, c);
-                       send_packet(ssh, SSH1_MSG_CHANNEL_OPEN_CONFIRMATION,
-                                   PKT_INT, c->remoteid, PKT_INT,
-                                   c->localid, PKT_END);
-                       logevent("Forwarded port opened successfully");
-                   }
-               }
-
-           } else if (pktin->type == SSH1_MSG_CHANNEL_OPEN_CONFIRMATION) {
-               unsigned int remoteid = ssh_pkt_getuint32(pktin);
-               unsigned int localid = ssh_pkt_getuint32(pktin);
-               struct ssh_channel *c;
-
-               c = find234(ssh->channels, &remoteid, ssh_channelfind);
-               if (c && c->type == CHAN_SOCKDATA_DORMANT) {
-                   c->remoteid = localid;
-                   c->type = CHAN_SOCKDATA;
-                   c->v.v1.throttling = 0;
-                   pfd_confirm(c->u.pfd.s);
-               }
-
-               if (c && c->closes) {
-                   /*
-                    * We have a pending close on this channel,
-                    * which we decided on before the server acked
-                    * the channel open. So now we know the
-                    * remoteid, we can close it again.
-                    */
-                   send_packet(ssh, SSH1_MSG_CHANNEL_CLOSE,
-                               PKT_INT, c->remoteid, PKT_END);
-               }
-
-           } else if (pktin->type == SSH1_MSG_CHANNEL_OPEN_FAILURE) {
-               unsigned int remoteid = ssh_pkt_getuint32(pktin);
-               struct ssh_channel *c;
-
-               c = find234(ssh->channels, &remoteid, ssh_channelfind);
-               if (c && c->type == CHAN_SOCKDATA_DORMANT) {
-                   logevent("Forwarded connection refused by server");
-                   pfd_close(c->u.pfd.s);
-                   del234(ssh->channels, c);
-                   sfree(c);
-               }
-
-           } else if (pktin->type == SSH1_MSG_CHANNEL_CLOSE ||
-                      pktin->type == SSH1_MSG_CHANNEL_CLOSE_CONFIRMATION) {
-               /* Remote side closes a channel. */
-               unsigned i = ssh_pkt_getuint32(pktin);
-               struct ssh_channel *c;
-               c = find234(ssh->channels, &i, ssh_channelfind);
-               if (c && ((int)c->remoteid) != -1) {
-                   int closetype;
-                   closetype =
-                       (pktin->type == SSH1_MSG_CHANNEL_CLOSE ? 1 : 2);
-
-                   if ((c->closes == 0) && (c->type == CHAN_X11)) {
-                       logevent("Forwarded X11 connection terminated");
-                       assert(c->u.x11.s != NULL);
-                       x11_close(c->u.x11.s);
-                       c->u.x11.s = NULL;
-                   }
-                   if ((c->closes == 0) && (c->type == CHAN_SOCKDATA)) {
-                       logevent("Forwarded port closed");
-                       assert(c->u.pfd.s != NULL);
-                       pfd_close(c->u.pfd.s);
-                       c->u.pfd.s = NULL;
-                   }
 
-                   c->closes |= (closetype << 2);   /* seen this message */
-                   if (!(c->closes & closetype)) {
-                       send_packet(ssh, pktin->type, PKT_INT, c->remoteid,
-                                   PKT_END);
-                       c->closes |= closetype;      /* sent it too */
-                   }
+       /*
+        * By this point, most incoming packets are already being
+        * handled by the dispatch table, and we need only pay
+        * attention to the unusual ones.
+        */
 
-                   if (c->closes == 15) {
-                       del234(ssh->channels, c);
-                       sfree(c);
-                   }
-               } else {
-                   bombout(("Received CHANNEL_CLOSE%s for %s channel %d\n",
-                            pktin->type == SSH1_MSG_CHANNEL_CLOSE ? "" :
-                            "_CONFIRMATION", c ? "half-open" : "nonexistent",
-                            i));
-                   crStopV;
-               }
-           } else if (pktin->type == SSH1_MSG_CHANNEL_DATA) {
-               /* Data sent down one of our channels. */
-               int i = ssh_pkt_getuint32(pktin);
-               char *p;
-               int len;
-               struct ssh_channel *c;
-
-               ssh_pkt_getstring(pktin, &p, &len);
-
-               c = find234(ssh->channels, &i, ssh_channelfind);
-               if (c) {
-                   int bufsize = 0;
-                   switch (c->type) {
-                     case CHAN_X11:
-                       bufsize = x11_send(c->u.x11.s, p, len);
-                       break;
-                     case CHAN_SOCKDATA:
-                       bufsize = pfd_send(c->u.pfd.s, p, len);
-                       break;
-                     case CHAN_AGENT:
-                       /* Data for an agent message. Buffer it. */
-                       while (len > 0) {
-                           if (c->u.a.lensofar < 4) {
-                               int l = min(4 - c->u.a.lensofar, len);
-                               memcpy(c->u.a.msglen + c->u.a.lensofar, p,
-                                      l);
-                               p += l;
-                               len -= l;
-                               c->u.a.lensofar += l;
-                           }
-                           if (c->u.a.lensofar == 4) {
-                               c->u.a.totallen =
-                                   4 + GET_32BIT(c->u.a.msglen);
-                               c->u.a.message = snewn(c->u.a.totallen,
-                                                      unsigned char);
-                               memcpy(c->u.a.message, c->u.a.msglen, 4);
-                           }
-                           if (c->u.a.lensofar >= 4 && len > 0) {
-                               int l =
-                                   min(c->u.a.totallen - c->u.a.lensofar,
-                                       len);
-                               memcpy(c->u.a.message + c->u.a.lensofar, p,
-                                      l);
-                               p += l;
-                               len -= l;
-                               c->u.a.lensofar += l;
-                           }
-                           if (c->u.a.lensofar == c->u.a.totallen) {
-                               void *reply;
-                               int replylen;
-                               if (agent_query(c->u.a.message,
-                                               c->u.a.totallen,
-                                               &reply, &replylen,
-                                               ssh_agentf_callback, c))
-                                   ssh_agentf_callback(c, reply, replylen);
-                               sfree(c->u.a.message);
-                               c->u.a.lensofar = 0;
-                           }
-                       }
-                       bufsize = 0;   /* agent channels never back up */
-                       break;
-                   }
-                   if (!c->v.v1.throttling && bufsize > SSH1_BUFFER_LIMIT) {
-                       c->v.v1.throttling = 1;
-                       ssh1_throttle(ssh, +1);
-                   }
-               }
-           } else if (pktin->type == SSH1_SMSG_SUCCESS) {
+       crReturnV;
+       if (pktin) {
+           if (pktin->type == SSH1_SMSG_SUCCESS) {
                /* may be from EXEC_SHELL on some servers */
            } else if (pktin->type == SSH1_SMSG_FAILURE) {
                /* may be from EXEC_SHELL on some servers
                 * if no pty is available or in other odd cases. Ignore */
-           } else if (pktin->type == SSH1_SMSG_EXIT_STATUS) {
-               char buf[100];
-               ssh->exitcode = ssh_pkt_getuint32(pktin);
-               sprintf(buf, "Server sent command exit status %d",
-                       ssh->exitcode);
-               logevent(buf);
-               send_packet(ssh, SSH1_CMSG_EXIT_CONFIRMATION, PKT_END);
-                /*
-                 * In case `helpful' firewalls or proxies tack
-                 * extra human-readable text on the end of the
-                 * session which we might mistake for another
-                 * encrypted packet, we close the session once
-                 * we've sent EXIT_CONFIRMATION.
-                 */
-                ssh_closing((Plug)ssh, NULL, 0, 0);
-                crStopV;
            } else {
                bombout(("Strange packet received: type %d", pktin->type));
                crStopV;
@@ -4216,7 +4297,6 @@ static int do_ssh2_transport(Ssh ssh, unsigned char *in, int inlen,
     s->csmac_tobe = s->scmac_tobe = NULL;
     s->cscomp_tobe = s->sccomp_tobe = NULL;
 
-    random_init();
     s->first_kex = 1;
 
     {
@@ -4279,6 +4359,11 @@ static int do_ssh2_transport(Ssh ssh, unsigned char *in, int inlen,
        ssh->queueing = TRUE;
 
        /*
+        * Flag that KEX is in progress.
+        */
+       ssh->kex_in_progress = TRUE;
+
+       /*
         * Construct and send our key exchange packet.
         */
        s->pktout = ssh2_pkt_init(SSH2_MSG_KEXINIT);
@@ -4630,10 +4715,61 @@ static int do_ssh2_transport(Ssh ssh, unsigned char *in, int inlen,
     ssh->hostkey->freekey(s->hkey);
 
     /*
+     * The exchange hash from the very first key exchange is also
+     * the session id, used in session key construction and
+     * authentication.
+     */
+    if (s->first_kex)
+       memcpy(ssh->v2_session_id, s->exchange_hash,
+              sizeof(s->exchange_hash));
+
+    /*
      * Send SSH2_MSG_NEWKEYS.
      */
     s->pktout = ssh2_pkt_init(SSH2_MSG_NEWKEYS);
     ssh2_pkt_send_noqueue(ssh, s->pktout);
+    ssh->outgoing_data_size = 0;       /* start counting from here */
+
+    /*
+     * We've sent client NEWKEYS, so create and initialise
+     * client-to-servere session keys.
+     */
+    if (ssh->cs_cipher_ctx)
+       ssh->cscipher->free_context(ssh->cs_cipher_ctx);
+    ssh->cscipher = s->cscipher_tobe;
+    ssh->cs_cipher_ctx = ssh->cscipher->make_context();
+
+    if (ssh->cs_mac_ctx)
+       ssh->csmac->free_context(ssh->cs_mac_ctx);
+    ssh->csmac = s->csmac_tobe;
+    ssh->cs_mac_ctx = ssh->csmac->make_context();
+
+    if (ssh->cs_comp_ctx)
+       ssh->cscomp->compress_cleanup(ssh->cs_comp_ctx);
+    ssh->cscomp = s->cscomp_tobe;
+    ssh->cs_comp_ctx = ssh->cscomp->compress_init();
+
+    /*
+     * Set IVs on client-to-server keys. Here we use the exchange
+     * hash from the _first_ key exchange.
+     */
+    {
+       unsigned char keyspace[40];
+       ssh2_mkkey(ssh,s->K,s->exchange_hash,ssh->v2_session_id,'C',keyspace);
+       ssh->cscipher->setkey(ssh->cs_cipher_ctx, keyspace);
+       ssh2_mkkey(ssh,s->K,s->exchange_hash,ssh->v2_session_id,'A',keyspace);
+       ssh->cscipher->setiv(ssh->cs_cipher_ctx, keyspace);
+       ssh2_mkkey(ssh,s->K,s->exchange_hash,ssh->v2_session_id,'E',keyspace);
+       ssh->csmac->setkey(ssh->cs_mac_ctx, keyspace);
+    }
+
+    logeventf(ssh, "Initialised %.200s client->server encryption",
+             ssh->cscipher->text_name);
+    logeventf(ssh, "Initialised %.200s client->server MAC algorithm",
+             ssh->csmac->text_name);
+    if (ssh->cscomp->text_name)
+       logeventf(ssh, "Initialised %s compression",
+                 ssh->cscomp->text_name);
 
     /*
      * Now our end of the key exchange is complete, we can send all
@@ -4650,76 +4786,51 @@ static int do_ssh2_transport(Ssh ssh, unsigned char *in, int inlen,
        bombout(("expected new-keys packet from server"));
        crStop(0);
     }
+    ssh->incoming_data_size = 0;       /* start counting from here */
 
     /*
-     * Create and initialise session keys.
+     * We've seen server NEWKEYS, so create and initialise
+     * server-to-client session keys.
      */
-    if (ssh->cs_cipher_ctx)
-       ssh->cscipher->free_context(ssh->cs_cipher_ctx);
-    ssh->cscipher = s->cscipher_tobe;
-    ssh->cs_cipher_ctx = ssh->cscipher->make_context();
-
     if (ssh->sc_cipher_ctx)
        ssh->sccipher->free_context(ssh->sc_cipher_ctx);
     ssh->sccipher = s->sccipher_tobe;
     ssh->sc_cipher_ctx = ssh->sccipher->make_context();
 
-    if (ssh->cs_mac_ctx)
-       ssh->csmac->free_context(ssh->cs_mac_ctx);
-    ssh->csmac = s->csmac_tobe;
-    ssh->cs_mac_ctx = ssh->csmac->make_context();
-
     if (ssh->sc_mac_ctx)
        ssh->scmac->free_context(ssh->sc_mac_ctx);
     ssh->scmac = s->scmac_tobe;
     ssh->sc_mac_ctx = ssh->scmac->make_context();
 
-    if (ssh->cs_comp_ctx)
-       ssh->cscomp->compress_cleanup(ssh->cs_comp_ctx);
-    ssh->cscomp = s->cscomp_tobe;
-    ssh->cs_comp_ctx = ssh->cscomp->compress_init();
-
     if (ssh->sc_comp_ctx)
        ssh->sccomp->decompress_cleanup(ssh->sc_comp_ctx);
     ssh->sccomp = s->sccomp_tobe;
     ssh->sc_comp_ctx = ssh->sccomp->decompress_init();
 
     /*
-     * Set IVs after keys. Here we use the exchange hash from the
-     * _first_ key exchange.
+     * Set IVs on server-to-client keys. Here we use the exchange
+     * hash from the _first_ key exchange.
      */
     {
        unsigned char keyspace[40];
-       if (s->first_kex)
-           memcpy(ssh->v2_session_id, s->exchange_hash,
-                  sizeof(s->exchange_hash));
-       ssh2_mkkey(ssh,s->K,s->exchange_hash,ssh->v2_session_id,'C',keyspace);
-       ssh->cscipher->setkey(ssh->cs_cipher_ctx, keyspace);
        ssh2_mkkey(ssh,s->K,s->exchange_hash,ssh->v2_session_id,'D',keyspace);
        ssh->sccipher->setkey(ssh->sc_cipher_ctx, keyspace);
-       ssh2_mkkey(ssh,s->K,s->exchange_hash,ssh->v2_session_id,'A',keyspace);
-       ssh->cscipher->setiv(ssh->cs_cipher_ctx, keyspace);
        ssh2_mkkey(ssh,s->K,s->exchange_hash,ssh->v2_session_id,'B',keyspace);
        ssh->sccipher->setiv(ssh->sc_cipher_ctx, keyspace);
-       ssh2_mkkey(ssh,s->K,s->exchange_hash,ssh->v2_session_id,'E',keyspace);
-       ssh->csmac->setkey(ssh->cs_mac_ctx, keyspace);
        ssh2_mkkey(ssh,s->K,s->exchange_hash,ssh->v2_session_id,'F',keyspace);
        ssh->scmac->setkey(ssh->sc_mac_ctx, keyspace);
     }
-    logeventf(ssh, "Initialised %.200s client->server encryption",
-             ssh->cscipher->text_name);
     logeventf(ssh, "Initialised %.200s server->client encryption",
              ssh->sccipher->text_name);
-    logeventf(ssh, "Initialised %.200s client->server MAC algorithm",
-             ssh->csmac->text_name);
     logeventf(ssh, "Initialised %.200s server->client MAC algorithm",
              ssh->scmac->text_name);
-    if (ssh->cscomp->text_name)
-       logeventf(ssh, "Initialised %s compression",
-                 ssh->cscomp->text_name);
     if (ssh->sccomp->text_name)
        logeventf(ssh, "Initialised %s decompression",
                  ssh->sccomp->text_name);
+
+    /*
+     * Free key exchange data.
+     */
     freebn(s->f);
     freebn(s->K);
     if (ssh->kex == &ssh_diffiehellman_gex) {
@@ -4728,6 +4839,12 @@ static int do_ssh2_transport(Ssh ssh, unsigned char *in, int inlen,
     }
 
     /*
+     * Key exchange is over. Schedule a timer for our next rekey.
+     */
+    ssh->kex_in_progress = FALSE;
+    ssh->next_rekey = schedule_timer(REKEY_TIMEOUT, ssh2_timer, ssh);
+
+    /*
      * If this is the first key exchange phase, we must pass the
      * SSH2_MSG_NEWKEYS packet to the next layer, not because it
      * wants to see it but because it will need time to initialise
@@ -4745,11 +4862,21 @@ static int do_ssh2_transport(Ssh ssh, unsigned char *in, int inlen,
      * function so that other things can run on top of the
      * transport. If we ever see a KEXINIT, we must go back to the
      * start.
+     * 
+     * We _also_ go back to the start if we see pktin==NULL and
+     * inlen==-1, because this is a special signal meaning
+     * `initiate client-driven rekey', and `in' contains a message
+     * giving the reason for the rekey.
      */
-    while (!(pktin && pktin->type == SSH2_MSG_KEXINIT)) {
+    while (!((pktin && pktin->type == SSH2_MSG_KEXINIT) ||
+            (!pktin && inlen == -1))) {
        crReturn(1);
     }
-    logevent("Server initiated key re-exchange");
+    if (pktin) {
+       logevent("Server initiated key re-exchange");
+    } else {
+       logevent((char *)in);
+    }
     goto begin_key_exchange;
 
     crFinish(1);
@@ -4824,7 +4951,7 @@ static void ssh2_set_window(struct ssh_channel *c, unsigned newwin)
     }
 }
 
-void ssh2_msg_channel_window_adjust(Ssh ssh, struct Packet *pktin)
+static void ssh2_msg_channel_window_adjust(Ssh ssh, struct Packet *pktin)
 {
     unsigned i = ssh_pkt_getuint32(pktin);
     struct ssh_channel *c;
@@ -4833,6 +4960,523 @@ void ssh2_msg_channel_window_adjust(Ssh ssh, struct Packet *pktin)
        c->v.v2.remwindow += ssh_pkt_getuint32(pktin);
 }
 
+static void ssh2_msg_channel_data(Ssh ssh, struct Packet *pktin)
+{
+    char *data;
+    int length;
+    unsigned i = ssh_pkt_getuint32(pktin);
+    struct ssh_channel *c;
+    c = find234(ssh->channels, &i, ssh_channelfind);
+    if (!c)
+       return;                        /* nonexistent channel */
+    if (pktin->type == SSH2_MSG_CHANNEL_EXTENDED_DATA &&
+       ssh_pkt_getuint32(pktin) != SSH2_EXTENDED_DATA_STDERR)
+       return;                        /* extended but not stderr */
+    ssh_pkt_getstring(pktin, &data, &length);
+    if (data) {
+       int bufsize = 0;
+       c->v.v2.locwindow -= length;
+       switch (c->type) {
+         case CHAN_MAINSESSION:
+           bufsize =
+               from_backend(ssh->frontend, pktin->type ==
+                            SSH2_MSG_CHANNEL_EXTENDED_DATA,
+                            data, length);
+           break;
+         case CHAN_X11:
+           bufsize = x11_send(c->u.x11.s, data, length);
+           break;
+         case CHAN_SOCKDATA:
+           bufsize = pfd_send(c->u.pfd.s, data, length);
+           break;
+         case CHAN_AGENT:
+           while (length > 0) {
+               if (c->u.a.lensofar < 4) {
+                   int l = min(4 - c->u.a.lensofar, length);
+                   memcpy(c->u.a.msglen + c->u.a.lensofar,
+                          data, l);
+                   data += l;
+                   length -= l;
+                   c->u.a.lensofar += l;
+               }
+               if (c->u.a.lensofar == 4) {
+                   c->u.a.totallen =
+                       4 + GET_32BIT(c->u.a.msglen);
+                   c->u.a.message = snewn(c->u.a.totallen,
+                                          unsigned char);
+                   memcpy(c->u.a.message, c->u.a.msglen, 4);
+               }
+               if (c->u.a.lensofar >= 4 && length > 0) {
+                   int l =
+                       min(c->u.a.totallen - c->u.a.lensofar,
+                           length);
+                   memcpy(c->u.a.message + c->u.a.lensofar,
+                          data, l);
+                   data += l;
+                   length -= l;
+                   c->u.a.lensofar += l;
+               }
+               if (c->u.a.lensofar == c->u.a.totallen) {
+                   void *reply;
+                   int replylen;
+                   if (agent_query(c->u.a.message,
+                                   c->u.a.totallen,
+                                   &reply, &replylen,
+                                   ssh_agentf_callback, c))
+                       ssh_agentf_callback(c, reply, replylen);
+                   sfree(c->u.a.message);
+                   c->u.a.lensofar = 0;
+               }
+           }
+           bufsize = 0;
+           break;
+       }
+       /*
+        * If we are not buffering too much data,
+        * enlarge the window again at the remote side.
+        */
+       if (bufsize < OUR_V2_WINSIZE)
+           ssh2_set_window(c, OUR_V2_WINSIZE - bufsize);
+    }
+}
+
+static void ssh2_msg_channel_eof(Ssh ssh, struct Packet *pktin)
+{
+    unsigned i = ssh_pkt_getuint32(pktin);
+    struct ssh_channel *c;
+
+    c = find234(ssh->channels, &i, ssh_channelfind);
+    if (!c)
+       return;                        /* nonexistent channel */
+
+    if (c->type == CHAN_X11) {
+       /*
+        * Remote EOF on an X11 channel means we should
+        * wrap up and close the channel ourselves.
+        */
+       x11_close(c->u.x11.s);
+       sshfwd_close(c);
+    } else if (c->type == CHAN_AGENT) {
+       sshfwd_close(c);
+    } else if (c->type == CHAN_SOCKDATA) {
+       pfd_close(c->u.pfd.s);
+       sshfwd_close(c);
+    }
+}
+
+static void ssh2_msg_channel_close(Ssh ssh, struct Packet *pktin)
+{
+    unsigned i = ssh_pkt_getuint32(pktin);
+    struct ssh_channel *c;
+    struct Packet *pktout;
+
+    c = find234(ssh->channels, &i, ssh_channelfind);
+    if (!c || ((int)c->remoteid) == -1) {
+       bombout(("Received CHANNEL_CLOSE for %s channel %d\n",
+                c ? "half-open" : "nonexistent", i));
+       return;
+    }
+    /* Do pre-close processing on the channel. */
+    switch (c->type) {
+      case CHAN_MAINSESSION:
+       ssh->mainchan = NULL;
+       update_specials_menu(ssh->frontend);
+       break;
+      case CHAN_X11:
+       if (c->u.x11.s != NULL)
+           x11_close(c->u.x11.s);
+       sshfwd_close(c);
+       break;
+      case CHAN_AGENT:
+       sshfwd_close(c);
+       break;
+      case CHAN_SOCKDATA:
+       if (c->u.pfd.s != NULL)
+           pfd_close(c->u.pfd.s);
+       sshfwd_close(c);
+       break;
+    }
+    if (c->closes == 0) {
+       pktout = ssh2_pkt_init(SSH2_MSG_CHANNEL_CLOSE);
+       ssh2_pkt_adduint32(pktout, c->remoteid);
+       ssh2_pkt_send(ssh, pktout);
+    }
+    del234(ssh->channels, c);
+    bufchain_clear(&c->v.v2.outbuffer);
+    sfree(c);
+
+    /*
+     * See if that was the last channel left open.
+     * (This is only our termination condition if we're
+     * not running in -N mode.)
+     */
+    if (!ssh->cfg.ssh_no_shell && count234(ssh->channels) == 0) {
+       logevent("All channels closed. Disconnecting");
+#if 0
+       /*
+        * We used to send SSH_MSG_DISCONNECT here,
+        * because I'd believed that _every_ conforming
+        * SSH2 connection had to end with a disconnect
+        * being sent by at least one side; apparently
+        * I was wrong and it's perfectly OK to
+        * unceremoniously slam the connection shut
+        * when you're done, and indeed OpenSSH feels
+        * this is more polite than sending a
+        * DISCONNECT. So now we don't.
+        */
+       s->pktout = ssh2_pkt_init(SSH2_MSG_DISCONNECT);
+       ssh2_pkt_adduint32(s->pktout, SSH2_DISCONNECT_BY_APPLICATION);
+       ssh2_pkt_addstring(s->pktout, "All open channels closed");
+       ssh2_pkt_addstring(s->pktout, "en");    /* language tag */
+       ssh2_pkt_send_noqueue(ssh, s->pktout);
+#endif
+       ssh_closing((Plug)ssh, NULL, 0, 0);
+    }
+}
+
+static void ssh2_msg_channel_open_confirmation(Ssh ssh, struct Packet *pktin)
+{
+    unsigned i = ssh_pkt_getuint32(pktin);
+    struct ssh_channel *c;
+    struct Packet *pktout;
+
+    c = find234(ssh->channels, &i, ssh_channelfind);
+    if (!c)
+       return;                        /* nonexistent channel */
+    if (c->type != CHAN_SOCKDATA_DORMANT)
+       return;                        /* dunno why they're confirming this */
+    c->remoteid = ssh_pkt_getuint32(pktin);
+    c->type = CHAN_SOCKDATA;
+    c->v.v2.remwindow = ssh_pkt_getuint32(pktin);
+    c->v.v2.remmaxpkt = ssh_pkt_getuint32(pktin);
+    if (c->u.pfd.s)
+       pfd_confirm(c->u.pfd.s);
+    if (c->closes) {
+       /*
+        * We have a pending close on this channel,
+        * which we decided on before the server acked
+        * the channel open. So now we know the
+        * remoteid, we can close it again.
+        */
+       pktout = ssh2_pkt_init(SSH2_MSG_CHANNEL_CLOSE);
+       ssh2_pkt_adduint32(pktout, c->remoteid);
+       ssh2_pkt_send(ssh, pktout);
+    }
+}
+
+static void ssh2_msg_channel_open_failure(Ssh ssh, struct Packet *pktin)
+{
+    static const char *const reasons[] = {
+       "<unknown reason code>",
+           "Administratively prohibited",
+           "Connect failed",
+           "Unknown channel type",
+           "Resource shortage",
+    };
+    unsigned i = ssh_pkt_getuint32(pktin);
+    unsigned reason_code;
+    char *reason_string;
+    int reason_length;
+    char *message;
+    struct ssh_channel *c;
+    c = find234(ssh->channels, &i, ssh_channelfind);
+    if (!c)
+       return;                        /* nonexistent channel */
+    if (c->type != CHAN_SOCKDATA_DORMANT)
+       return;                        /* dunno why they're failing this */
+
+    reason_code = ssh_pkt_getuint32(pktin);
+    if (reason_code >= lenof(reasons))
+       reason_code = 0; /* ensure reasons[reason_code] in range */
+    ssh_pkt_getstring(pktin, &reason_string, &reason_length);
+    message = dupprintf("Forwarded connection refused by"
+                       " server: %s [%.*s]", reasons[reason_code],
+                       reason_length, reason_string);
+    logevent(message);
+    sfree(message);
+
+    pfd_close(c->u.pfd.s);
+
+    del234(ssh->channels, c);
+    sfree(c);
+}
+
+static void ssh2_msg_channel_request(Ssh ssh, struct Packet *pktin)
+{
+    unsigned localid;
+    char *type;
+    int typelen, want_reply;
+    int reply = SSH2_MSG_CHANNEL_FAILURE; /* default */
+    struct ssh_channel *c;
+    struct Packet *pktout;
+
+    localid = ssh_pkt_getuint32(pktin);
+    ssh_pkt_getstring(pktin, &type, &typelen);
+    want_reply = ssh2_pkt_getbool(pktin);
+
+    /*
+     * First, check that the channel exists. Otherwise,
+     * we can instantly disconnect with a rude message.
+     */
+    c = find234(ssh->channels, &localid, ssh_channelfind);
+    if (!c) {
+       char buf[80];
+       sprintf(buf, "Received channel request for nonexistent"
+               " channel %d", localid);
+       logevent(buf);
+       pktout = ssh2_pkt_init(SSH2_MSG_DISCONNECT);
+       ssh2_pkt_adduint32(pktout, SSH2_DISCONNECT_BY_APPLICATION);
+       ssh2_pkt_addstring(pktout, buf);
+       ssh2_pkt_addstring(pktout, "en");       /* language tag */
+       ssh2_pkt_send_noqueue(ssh, pktout);
+       connection_fatal(ssh->frontend, "%s", buf);
+       ssh_closing((Plug)ssh, NULL, 0, 0);
+       return;
+    }
+
+    /*
+     * Having got the channel number, we now look at
+     * the request type string to see if it's something
+     * we recognise.
+     */
+    if (c == ssh->mainchan) {
+       /*
+        * We recognise "exit-status" and "exit-signal" on
+        * the primary channel.
+        */
+       if (typelen == 11 &&
+           !memcmp(type, "exit-status", 11)) {
+
+           ssh->exitcode = ssh_pkt_getuint32(pktin);
+           logeventf(ssh, "Server sent command exit status %d",
+                     ssh->exitcode);
+           reply = SSH2_MSG_CHANNEL_SUCCESS;
+
+       } else if (typelen == 11 &&
+                  !memcmp(type, "exit-signal", 11)) {
+
+           int is_plausible = TRUE, is_int = FALSE;
+           char *fmt_sig = "", *fmt_msg = "";
+           char *msg;
+           int msglen = 0, core = FALSE;
+           /* ICK: older versions of OpenSSH (e.g. 3.4p1)
+            * provide an `int' for the signal, despite its
+            * having been a `string' in the drafts since at
+            * least 2001. (Fixed in session.c 1.147.) Try to
+            * infer which we can safely parse it as. */
+           {
+               unsigned char *p = pktin->body +
+                   pktin->savedpos;
+               long len = pktin->length - pktin->savedpos;
+               unsigned long num = GET_32BIT(p); /* what is it? */
+               /* If it's 0, it hardly matters; assume string */
+               if (num == 0) {
+                   is_int = FALSE;
+               } else {
+                   int maybe_int = FALSE, maybe_str = FALSE;
+#define CHECK_HYPOTHESIS(offset, result) \
+    do { \
+       long q = offset; \
+       if (q >= 0 && q+4 <= len) { \
+           q = q + 4 + GET_32BIT(p+q); \
+           if (q >= 0 && q+4 <= len && \
+                   (q = q + 4 + GET_32BIT(p+q)) && q == len) \
+               result = TRUE; \
+       } \
+    } while(0)
+                   CHECK_HYPOTHESIS(4+1, maybe_int);
+                   CHECK_HYPOTHESIS(4+num+1, maybe_str);
+#undef CHECK_HYPOTHESIS
+                   if (maybe_int && !maybe_str)
+                       is_int = TRUE;
+                   else if (!maybe_int && maybe_str)
+                       is_int = FALSE;
+                   else
+                       /* Crikey. Either or neither. Panic. */
+                       is_plausible = FALSE;
+               }
+           }
+           if (is_plausible) {
+               if (is_int) {
+                   /* Old non-standard OpenSSH. */
+                   int signum = ssh_pkt_getuint32(pktin);
+                   fmt_sig = dupprintf(" %d", signum);
+               } else {
+                   /* As per the drafts. */
+                   char *sig;
+                   int siglen;
+                   ssh_pkt_getstring(pktin, &sig, &siglen);
+                   /* Signal name isn't supposed to be blank, but
+                    * let's cope gracefully if it is. */
+                   if (siglen) {
+                       fmt_sig = dupprintf(" \"%.*s\"",
+                                           siglen, sig);
+                   }
+               }
+               core = ssh2_pkt_getbool(pktin);
+               ssh_pkt_getstring(pktin, &msg, &msglen);
+               if (msglen) {
+                   fmt_msg = dupprintf(" (\"%.*s\")", msglen, msg);
+               }
+               /* ignore lang tag */
+           } /* else don't attempt to parse */
+           logeventf(ssh, "Server exited on signal%s%s%s",
+                     fmt_sig, core ? " (core dumped)" : "",
+                     fmt_msg);
+           if (*fmt_sig) sfree(fmt_sig);
+           if (*fmt_msg) sfree(fmt_msg);
+           reply = SSH2_MSG_CHANNEL_SUCCESS;
+
+       }
+    } else {
+       /*
+        * This is a channel request we don't know
+        * about, so we now either ignore the request
+        * or respond with CHANNEL_FAILURE, depending
+        * on want_reply.
+        */
+       reply = SSH2_MSG_CHANNEL_FAILURE;
+    }
+    if (want_reply) {
+       pktout = ssh2_pkt_init(reply);
+       ssh2_pkt_adduint32(pktout, c->remoteid);
+       ssh2_pkt_send(ssh, pktout);
+    }
+}
+
+static void ssh2_msg_global_request(Ssh ssh, struct Packet *pktin)
+{
+    char *type;
+    int typelen, want_reply;
+    struct Packet *pktout;
+
+    ssh_pkt_getstring(pktin, &type, &typelen);
+    want_reply = ssh2_pkt_getbool(pktin);
+
+    /*
+     * We currently don't support any global requests
+     * at all, so we either ignore the request or
+     * respond with REQUEST_FAILURE, depending on
+     * want_reply.
+     */
+    if (want_reply) {
+       pktout = ssh2_pkt_init(SSH2_MSG_REQUEST_FAILURE);
+       ssh2_pkt_send(ssh, pktout);
+    }
+}
+
+static void ssh2_msg_channel_open(Ssh ssh, struct Packet *pktin)
+{
+    char *type;
+    int typelen;
+    char *peeraddr;
+    int peeraddrlen;
+    int peerport;
+    char *error = NULL;
+    struct ssh_channel *c;
+    unsigned remid, winsize, pktsize;
+    struct Packet *pktout;
+
+    ssh_pkt_getstring(pktin, &type, &typelen);
+    c = snew(struct ssh_channel);
+    c->ssh = ssh;
+
+    remid = ssh_pkt_getuint32(pktin);
+    winsize = ssh_pkt_getuint32(pktin);
+    pktsize = ssh_pkt_getuint32(pktin);
+
+    if (typelen == 3 && !memcmp(type, "x11", 3)) {
+       char *addrstr;
+
+       ssh_pkt_getstring(pktin, &peeraddr, &peeraddrlen);
+       addrstr = snewn(peeraddrlen+1, char);
+       memcpy(addrstr, peeraddr, peeraddrlen);
+       addrstr[peeraddrlen] = '\0';
+       peerport = ssh_pkt_getuint32(pktin);
+
+       logeventf(ssh, "Received X11 connect request from %s:%d",
+                 addrstr, peerport);
+
+       if (!ssh->X11_fwd_enabled)
+           error = "X11 forwarding is not enabled";
+       else if (x11_init(&c->u.x11.s, ssh->cfg.x11_display, c,
+                         ssh->x11auth, addrstr, peerport,
+                         &ssh->cfg) != NULL) {
+           error = "Unable to open an X11 connection";
+       } else {
+           logevent("Opening X11 forward connection succeeded");
+           c->type = CHAN_X11;
+       }
+
+       sfree(addrstr);
+    } else if (typelen == 15 &&
+              !memcmp(type, "forwarded-tcpip", 15)) {
+       struct ssh_rportfwd pf, *realpf;
+       char *dummy;
+       int dummylen;
+       ssh_pkt_getstring(pktin, &dummy, &dummylen);/* skip address */
+       pf.sport = ssh_pkt_getuint32(pktin);
+       ssh_pkt_getstring(pktin, &peeraddr, &peeraddrlen);
+       peerport = ssh_pkt_getuint32(pktin);
+       realpf = find234(ssh->rportfwds, &pf, NULL);
+       logeventf(ssh, "Received remote port %d open request "
+                 "from %s:%d", pf.sport, peeraddr, peerport);
+       if (realpf == NULL) {
+           error = "Remote port is not recognised";
+       } else {
+           const char *e = pfd_newconnect(&c->u.pfd.s,
+                                          realpf->dhost,
+                                          realpf->dport, c,
+                                          &ssh->cfg);
+           logeventf(ssh, "Attempting to forward remote port to "
+                     "%s:%d", realpf->dhost, realpf->dport);
+           if (e != NULL) {
+               logeventf(ssh, "Port open failed: %s", e);
+               error = "Port open failed";
+           } else {
+               logevent("Forwarded port opened successfully");
+               c->type = CHAN_SOCKDATA;
+           }
+       }
+    } else if (typelen == 22 &&
+              !memcmp(type, "auth-agent@openssh.com", 3)) {
+       if (!ssh->agentfwd_enabled)
+           error = "Agent forwarding is not enabled";
+       else {
+           c->type = CHAN_AGENT;       /* identify channel type */
+           c->u.a.lensofar = 0;
+       }
+    } else {
+       error = "Unsupported channel type requested";
+    }
+
+    c->remoteid = remid;
+    if (error) {
+       pktout = ssh2_pkt_init(SSH2_MSG_CHANNEL_OPEN_FAILURE);
+       ssh2_pkt_adduint32(pktout, c->remoteid);
+       ssh2_pkt_adduint32(pktout, SSH2_OPEN_CONNECT_FAILED);
+       ssh2_pkt_addstring(pktout, error);
+       ssh2_pkt_addstring(pktout, "en");       /* language tag */
+       ssh2_pkt_send(ssh, pktout);
+       logeventf(ssh, "Rejected channel open: %s", error);
+       sfree(c);
+    } else {
+       c->localid = alloc_channel_id(ssh);
+       c->closes = 0;
+       c->v.v2.locwindow = OUR_V2_WINSIZE;
+       c->v.v2.remwindow = winsize;
+       c->v.v2.remmaxpkt = pktsize;
+       bufchain_init(&c->v.v2.outbuffer);
+       add234(ssh->channels, c);
+       pktout = ssh2_pkt_init(SSH2_MSG_CHANNEL_OPEN_CONFIRMATION);
+       ssh2_pkt_adduint32(pktout, c->remoteid);
+       ssh2_pkt_adduint32(pktout, c->localid);
+       ssh2_pkt_adduint32(pktout, c->v.v2.locwindow);
+       ssh2_pkt_adduint32(pktout, 0x4000UL);   /* our max pkt size */
+       ssh2_pkt_send(ssh, pktout);
+    }
+}
+
 /*
  * Handle the SSH2 userauth and connection layers.
  */
@@ -5713,6 +6357,8 @@ static void do_ssh2_authconn(Ssh ssh, unsigned char *in, int inlen,
      */
     ssh->packet_dispatch[SSH2_MSG_CHANNEL_WINDOW_ADJUST] =
        ssh2_msg_channel_window_adjust;
+    ssh->packet_dispatch[SSH2_MSG_GLOBAL_REQUEST] =
+       ssh2_msg_global_request;
 
     /*
      * Create the main session channel.
@@ -5751,6 +6397,24 @@ static void do_ssh2_authconn(Ssh ssh, unsigned char *in, int inlen,
        ssh->mainchan = NULL;
 
     /*
+     * Now we have a channel, make dispatch table entries for
+     * general channel-based messages.
+     */
+    ssh->packet_dispatch[SSH2_MSG_CHANNEL_DATA] =
+    ssh->packet_dispatch[SSH2_MSG_CHANNEL_EXTENDED_DATA] =
+       ssh2_msg_channel_data;
+    ssh->packet_dispatch[SSH2_MSG_CHANNEL_EOF] = ssh2_msg_channel_eof;
+    ssh->packet_dispatch[SSH2_MSG_CHANNEL_CLOSE] = ssh2_msg_channel_close;
+    ssh->packet_dispatch[SSH2_MSG_CHANNEL_OPEN_CONFIRMATION] =
+       ssh2_msg_channel_open_confirmation;
+    ssh->packet_dispatch[SSH2_MSG_CHANNEL_OPEN_FAILURE] =
+       ssh2_msg_channel_open_failure;
+    ssh->packet_dispatch[SSH2_MSG_CHANNEL_REQUEST] =
+       ssh2_msg_channel_request;
+    ssh->packet_dispatch[SSH2_MSG_CHANNEL_OPEN] =
+       ssh2_msg_channel_open;
+
+    /*
      * Potentially enable X11 forwarding.
      */
     if (ssh->mainchan && ssh->cfg.x11_forward) {
@@ -6159,499 +6823,15 @@ static void do_ssh2_authconn(Ssh ssh, unsigned char *in, int inlen,
        crReturnV;
        s->try_send = FALSE;
        if (pktin) {
-           if (pktin->type == SSH2_MSG_CHANNEL_DATA ||
-               pktin->type == SSH2_MSG_CHANNEL_EXTENDED_DATA) {
-               char *data;
-               int length;
-               unsigned i = ssh_pkt_getuint32(pktin);
-               struct ssh_channel *c;
-               c = find234(ssh->channels, &i, ssh_channelfind);
-               if (!c)
-                   continue;          /* nonexistent channel */
-               if (pktin->type == SSH2_MSG_CHANNEL_EXTENDED_DATA &&
-                   ssh_pkt_getuint32(pktin) != SSH2_EXTENDED_DATA_STDERR)
-                   continue;          /* extended but not stderr */
-               ssh_pkt_getstring(pktin, &data, &length);
-               if (data) {
-                   int bufsize = 0;
-                   c->v.v2.locwindow -= length;
-                   switch (c->type) {
-                     case CHAN_MAINSESSION:
-                       bufsize =
-                           from_backend(ssh->frontend, pktin->type ==
-                                        SSH2_MSG_CHANNEL_EXTENDED_DATA,
-                                        data, length);
-                       break;
-                     case CHAN_X11:
-                       bufsize = x11_send(c->u.x11.s, data, length);
-                       break;
-                     case CHAN_SOCKDATA:
-                       bufsize = pfd_send(c->u.pfd.s, data, length);
-                       break;
-                     case CHAN_AGENT:
-                       while (length > 0) {
-                           if (c->u.a.lensofar < 4) {
-                               int l = min(4 - c->u.a.lensofar, length);
-                               memcpy(c->u.a.msglen + c->u.a.lensofar,
-                                      data, l);
-                               data += l;
-                               length -= l;
-                               c->u.a.lensofar += l;
-                           }
-                           if (c->u.a.lensofar == 4) {
-                               c->u.a.totallen =
-                                   4 + GET_32BIT(c->u.a.msglen);
-                               c->u.a.message = snewn(c->u.a.totallen,
-                                                      unsigned char);
-                               memcpy(c->u.a.message, c->u.a.msglen, 4);
-                           }
-                           if (c->u.a.lensofar >= 4 && length > 0) {
-                               int l =
-                                   min(c->u.a.totallen - c->u.a.lensofar,
-                                       length);
-                               memcpy(c->u.a.message + c->u.a.lensofar,
-                                      data, l);
-                               data += l;
-                               length -= l;
-                               c->u.a.lensofar += l;
-                           }
-                           if (c->u.a.lensofar == c->u.a.totallen) {
-                               void *reply;
-                               int replylen;
-                               if (agent_query(c->u.a.message,
-                                               c->u.a.totallen,
-                                               &reply, &replylen,
-                                               ssh_agentf_callback, c))
-                                   ssh_agentf_callback(c, reply, replylen);
-                               sfree(c->u.a.message);
-                               c->u.a.lensofar = 0;
-                           }
-                       }
-                       bufsize = 0;
-                       break;
-                   }
-                   /*
-                    * If we are not buffering too much data,
-                    * enlarge the window again at the remote side.
-                    */
-                   if (bufsize < OUR_V2_WINSIZE)
-                       ssh2_set_window(c, OUR_V2_WINSIZE - bufsize);
-               }
-           } else if (pktin->type == SSH2_MSG_CHANNEL_EOF) {
-               unsigned i = ssh_pkt_getuint32(pktin);
-               struct ssh_channel *c;
-
-               c = find234(ssh->channels, &i, ssh_channelfind);
-               if (!c)
-                   continue;          /* nonexistent channel */
-
-               if (c->type == CHAN_X11) {
-                   /*
-                    * Remote EOF on an X11 channel means we should
-                    * wrap up and close the channel ourselves.
-                    */
-                   x11_close(c->u.x11.s);
-                   sshfwd_close(c);
-               } else if (c->type == CHAN_AGENT) {
-                   sshfwd_close(c);
-               } else if (c->type == CHAN_SOCKDATA) {
-                   pfd_close(c->u.pfd.s);
-                   sshfwd_close(c);
-               }
-           } else if (pktin->type == SSH2_MSG_CHANNEL_CLOSE) {
-               unsigned i = ssh_pkt_getuint32(pktin);
-               struct ssh_channel *c;
-
-               c = find234(ssh->channels, &i, ssh_channelfind);
-               if (!c || ((int)c->remoteid) == -1) {
-                   bombout(("Received CHANNEL_CLOSE for %s channel %d\n",
-                            c ? "half-open" : "nonexistent", i));
-                   crStopV;
-               }
-               /* Do pre-close processing on the channel. */
-               switch (c->type) {
-                 case CHAN_MAINSESSION:
-                   ssh->mainchan = NULL;
-                   update_specials_menu(ssh->frontend);
-                   break;
-                 case CHAN_X11:
-                   if (c->u.x11.s != NULL)
-                       x11_close(c->u.x11.s);
-                   sshfwd_close(c);
-                   break;
-                 case CHAN_AGENT:
-                   sshfwd_close(c);
-                   break;
-                 case CHAN_SOCKDATA:
-                   if (c->u.pfd.s != NULL)
-                       pfd_close(c->u.pfd.s);
-                   sshfwd_close(c);
-                   break;
-               }
-               if (c->closes == 0) {
-                   s->pktout = ssh2_pkt_init(SSH2_MSG_CHANNEL_CLOSE);
-                   ssh2_pkt_adduint32(s->pktout, c->remoteid);
-                   ssh2_pkt_send(ssh, s->pktout);
-               }
-               del234(ssh->channels, c);
-               bufchain_clear(&c->v.v2.outbuffer);
-               sfree(c);
 
-               /*
-                * See if that was the last channel left open.
-                * (This is only our termination condition if we're
-                * not running in -N mode.)
-                */
-               if (!ssh->cfg.ssh_no_shell && count234(ssh->channels) == 0) {
-                   logevent("All channels closed. Disconnecting");
-#if 0
-                    /*
-                     * We used to send SSH_MSG_DISCONNECT here,
-                     * because I'd believed that _every_ conforming
-                     * SSH2 connection had to end with a disconnect
-                     * being sent by at least one side; apparently
-                     * I was wrong and it's perfectly OK to
-                     * unceremoniously slam the connection shut
-                     * when you're done, and indeed OpenSSH feels
-                     * this is more polite than sending a
-                     * DISCONNECT. So now we don't.
-                     */
-                   s->pktout = ssh2_pkt_init(SSH2_MSG_DISCONNECT);
-                   ssh2_pkt_adduint32(s->pktout, SSH2_DISCONNECT_BY_APPLICATION);
-                   ssh2_pkt_addstring(s->pktout, "All open channels closed");
-                   ssh2_pkt_addstring(s->pktout, "en");        /* language tag */
-                   ssh2_pkt_send_noqueue(ssh, s->pktout);
-#endif
-                    ssh_closing((Plug)ssh, NULL, 0, 0);
-                   crStopV;
-               }
-               continue;              /* remote sends close; ignore (FIXME) */
-           } else if (pktin->type == SSH2_MSG_CHANNEL_OPEN_CONFIRMATION) {
-               unsigned i = ssh_pkt_getuint32(pktin);
-               struct ssh_channel *c;
-               c = find234(ssh->channels, &i, ssh_channelfind);
-               if (!c)
-                   continue;          /* nonexistent channel */
-               if (c->type != CHAN_SOCKDATA_DORMANT)
-                   continue;          /* dunno why they're confirming this */
-               c->remoteid = ssh_pkt_getuint32(pktin);
-               c->type = CHAN_SOCKDATA;
-               c->v.v2.remwindow = ssh_pkt_getuint32(pktin);
-               c->v.v2.remmaxpkt = ssh_pkt_getuint32(pktin);
-               if (c->u.pfd.s)
-                   pfd_confirm(c->u.pfd.s);
-               if (c->closes) {
-                   /*
-                    * We have a pending close on this channel,
-                    * which we decided on before the server acked
-                    * the channel open. So now we know the
-                    * remoteid, we can close it again.
-                    */
-                   s->pktout = ssh2_pkt_init(SSH2_MSG_CHANNEL_CLOSE);
-                   ssh2_pkt_adduint32(s->pktout, c->remoteid);
-                   ssh2_pkt_send(ssh, s->pktout);
-               }
-           } else if (pktin->type == SSH2_MSG_CHANNEL_OPEN_FAILURE) {
-                static const char *const reasons[] = {
-                    "<unknown reason code>",
-                    "Administratively prohibited",
-                    "Connect failed",
-                    "Unknown channel type",
-                    "Resource shortage",
-                };
-               unsigned i = ssh_pkt_getuint32(pktin);
-                unsigned reason_code;
-                char *reason_string;
-                int reason_length;
-                char *message;
-               struct ssh_channel *c;
-               c = find234(ssh->channels, &i, ssh_channelfind);
-               if (!c)
-                   continue;          /* nonexistent channel */
-               if (c->type != CHAN_SOCKDATA_DORMANT)
-                   continue;          /* dunno why they're failing this */
-
-                reason_code = ssh_pkt_getuint32(pktin);
-                if (reason_code >= lenof(reasons))
-                    reason_code = 0; /* ensure reasons[reason_code] in range */
-                ssh_pkt_getstring(pktin, &reason_string, &reason_length);
-                message = dupprintf("Forwarded connection refused by"
-                                    " server: %s [%.*s]", reasons[reason_code],
-                                    reason_length, reason_string);
-               logevent(message);
-                sfree(message);
-
-               pfd_close(c->u.pfd.s);
-
-               del234(ssh->channels, c);
-               sfree(c);
-           } else if (pktin->type == SSH2_MSG_CHANNEL_REQUEST) {
-               unsigned localid;
-               char *type;
-               int typelen, want_reply;
-               int reply = SSH2_MSG_CHANNEL_FAILURE; /* default */
-               struct ssh_channel *c;
-
-               localid = ssh_pkt_getuint32(pktin);
-               ssh_pkt_getstring(pktin, &type, &typelen);
-               want_reply = ssh2_pkt_getbool(pktin);
-
-               /*
-                * First, check that the channel exists. Otherwise,
-                * we can instantly disconnect with a rude message.
-                */
-               c = find234(ssh->channels, &localid, ssh_channelfind);
-               if (!c) {
-                   char buf[80];
-                   sprintf(buf, "Received channel request for nonexistent"
-                           " channel %d", localid);
-                   logevent(buf);
-                   s->pktout = ssh2_pkt_init(SSH2_MSG_DISCONNECT);
-                   ssh2_pkt_adduint32(s->pktout, SSH2_DISCONNECT_BY_APPLICATION);
-                   ssh2_pkt_addstring(s->pktout, buf);
-                   ssh2_pkt_addstring(s->pktout, "en");        /* language tag */
-                   ssh2_pkt_send_noqueue(ssh, s->pktout);
-                   connection_fatal(ssh->frontend, "%s", buf);
-                    ssh_closing((Plug)ssh, NULL, 0, 0);
-                   crStopV;
-               }
-
-               /*
-                * Having got the channel number, we now look at
-                * the request type string to see if it's something
-                * we recognise.
-                */
-               if (c == ssh->mainchan) {
-                   /*
-                    * We recognise "exit-status" and "exit-signal" on
-                    * the primary channel.
-                    */
-                   if (typelen == 11 &&
-                       !memcmp(type, "exit-status", 11)) {
-
-                       ssh->exitcode = ssh_pkt_getuint32(pktin);
-                       logeventf(ssh, "Server sent command exit status %d",
-                                 ssh->exitcode);
-                       reply = SSH2_MSG_CHANNEL_SUCCESS;
-
-                   } else if (typelen == 11 &&
-                              !memcmp(type, "exit-signal", 11)) {
-
-                       int is_plausible = TRUE, is_int = FALSE;
-                       char *fmt_sig = "", *fmt_msg = "";
-                       char *msg;
-                       int msglen = 0, core = FALSE;
-                       /* ICK: older versions of OpenSSH (e.g. 3.4p1)
-                        * provide an `int' for the signal, despite its
-                        * having been a `string' in the drafts since at
-                        * least 2001. (Fixed in session.c 1.147.) Try to
-                        * infer which we can safely parse it as. */
-                       {
-                           unsigned char *p = pktin->body +
-                                              pktin->savedpos;
-                           long len = pktin->length - pktin->savedpos;
-                           unsigned long num = GET_32BIT(p); /* what is it? */
-                           /* If it's 0, it hardly matters; assume string */
-                           if (num == 0) {
-                               is_int = FALSE;
-                           } else {
-                               int maybe_int = FALSE, maybe_str = FALSE;
-#define CHECK_HYPOTHESIS(offset, result) \
-    do { \
-       long q = offset; \
-       if (q >= 0 && q+4 <= len) { \
-           q = q + 4 + GET_32BIT(p+q); \
-           if (q >= 0 && q+4 <= len && \
-                   (q = q + 4 + GET_32BIT(p+q)) && q == len) \
-               result = TRUE; \
-       } \
-    } while(0)
-                               CHECK_HYPOTHESIS(4+1, maybe_int);
-                               CHECK_HYPOTHESIS(4+num+1, maybe_str);
-#undef CHECK_HYPOTHESIS
-                               if (maybe_int && !maybe_str)
-                                   is_int = TRUE;
-                               else if (!maybe_int && maybe_str)
-                                   is_int = FALSE;
-                               else
-                                   /* Crikey. Either or neither. Panic. */
-                                   is_plausible = FALSE;
-                           }
-                       }
-                       if (is_plausible) {
-                           if (is_int) {
-                               /* Old non-standard OpenSSH. */
-                               int signum = ssh_pkt_getuint32(pktin);
-                               fmt_sig = dupprintf(" %d", signum);
-                           } else {
-                               /* As per the drafts. */
-                               char *sig;
-                               int siglen;
-                               ssh_pkt_getstring(pktin, &sig, &siglen);
-                               /* Signal name isn't supposed to be blank, but
-                                * let's cope gracefully if it is. */
-                               if (siglen) {
-                                   fmt_sig = dupprintf(" \"%.*s\"",
-                                                       siglen, sig);
-                               }
-                           }
-                           core = ssh2_pkt_getbool(pktin);
-                           ssh_pkt_getstring(pktin, &msg, &msglen);
-                           if (msglen) {
-                               fmt_msg = dupprintf(" (\"%.*s\")", msglen, msg);
-                           }
-                           /* ignore lang tag */
-                       } /* else don't attempt to parse */
-                       logeventf(ssh, "Server exited on signal%s%s%s",
-                                 fmt_sig, core ? " (core dumped)" : "",
-                                 fmt_msg);
-                       if (*fmt_sig) sfree(fmt_sig);
-                       if (*fmt_msg) sfree(fmt_msg);
-                       reply = SSH2_MSG_CHANNEL_SUCCESS;
-
-                   }
-               } else {
-                   /*
-                    * This is a channel request we don't know
-                    * about, so we now either ignore the request
-                    * or respond with CHANNEL_FAILURE, depending
-                    * on want_reply.
-                    */
-                   reply = SSH2_MSG_CHANNEL_FAILURE;
-               }
-               if (want_reply) {
-                   s->pktout = ssh2_pkt_init(reply);
-                   ssh2_pkt_adduint32(s->pktout, c->remoteid);
-                   ssh2_pkt_send(ssh, s->pktout);
-               }
-           } else if (pktin->type == SSH2_MSG_GLOBAL_REQUEST) {
-               char *type;
-               int typelen, want_reply;
-
-               ssh_pkt_getstring(pktin, &type, &typelen);
-               want_reply = ssh2_pkt_getbool(pktin);
-
-                /*
-                 * We currently don't support any global requests
-                 * at all, so we either ignore the request or
-                 * respond with REQUEST_FAILURE, depending on
-                 * want_reply.
-                 */
-                if (want_reply) {
-                    s->pktout = ssh2_pkt_init(SSH2_MSG_REQUEST_FAILURE);
-                    ssh2_pkt_send(ssh, s->pktout);
-               }
-           } else if (pktin->type == SSH2_MSG_CHANNEL_OPEN) {
-               char *type;
-               int typelen;
-               char *peeraddr;
-               int peeraddrlen;
-               int peerport;
-               char *error = NULL;
-               struct ssh_channel *c;
-               unsigned remid, winsize, pktsize;
-               ssh_pkt_getstring(pktin, &type, &typelen);
-               c = snew(struct ssh_channel);
-               c->ssh = ssh;
-
-               remid = ssh_pkt_getuint32(pktin);
-               winsize = ssh_pkt_getuint32(pktin);
-               pktsize = ssh_pkt_getuint32(pktin);
-
-               if (typelen == 3 && !memcmp(type, "x11", 3)) {
-                   char *addrstr;
-
-                    ssh_pkt_getstring(pktin, &peeraddr, &peeraddrlen);
-                   addrstr = snewn(peeraddrlen+1, char);
-                   memcpy(addrstr, peeraddr, peeraddrlen);
-                   addrstr[peeraddrlen] = '\0';
-                    peerport = ssh_pkt_getuint32(pktin);
-
-                   logeventf(ssh, "Received X11 connect request from %s:%d",
-                             addrstr, peerport);
-
-                   if (!ssh->X11_fwd_enabled)
-                       error = "X11 forwarding is not enabled";
-                   else if (x11_init(&c->u.x11.s, ssh->cfg.x11_display, c,
-                                     ssh->x11auth, addrstr, peerport,
-                                     &ssh->cfg) != NULL) {
-                       error = "Unable to open an X11 connection";
-                   } else {
-                       logevent("Opening X11 forward connection succeeded");
-                       c->type = CHAN_X11;
-                   }
-
-                   sfree(addrstr);
-               } else if (typelen == 15 &&
-                          !memcmp(type, "forwarded-tcpip", 15)) {
-                   struct ssh_rportfwd pf, *realpf;
-                   char *dummy;
-                   int dummylen;
-                   ssh_pkt_getstring(pktin, &dummy, &dummylen);/* skip address */
-                   pf.sport = ssh_pkt_getuint32(pktin);
-                    ssh_pkt_getstring(pktin, &peeraddr, &peeraddrlen);
-                    peerport = ssh_pkt_getuint32(pktin);
-                   realpf = find234(ssh->rportfwds, &pf, NULL);
-                   logeventf(ssh, "Received remote port %d open request "
-                             "from %s:%d", pf.sport, peeraddr, peerport);
-                   if (realpf == NULL) {
-                       error = "Remote port is not recognised";
-                   } else {
-                       const char *e = pfd_newconnect(&c->u.pfd.s,
-                                                      realpf->dhost,
-                                                      realpf->dport, c,
-                                                      &ssh->cfg);
-                       logeventf(ssh, "Attempting to forward remote port to "
-                                 "%s:%d", realpf->dhost, realpf->dport);
-                       if (e != NULL) {
-                           logeventf(ssh, "Port open failed: %s", e);
-                           error = "Port open failed";
-                       } else {
-                           logevent("Forwarded port opened successfully");
-                           c->type = CHAN_SOCKDATA;
-                       }
-                   }
-               } else if (typelen == 22 &&
-                          !memcmp(type, "auth-agent@openssh.com", 3)) {
-                   if (!ssh->agentfwd_enabled)
-                       error = "Agent forwarding is not enabled";
-                   else {
-                       c->type = CHAN_AGENT;   /* identify channel type */
-                       c->u.a.lensofar = 0;
-                   }
-               } else {
-                   error = "Unsupported channel type requested";
-               }
+           /*
+            * _All_ the connection-layer packets we expect to
+            * receive are now handled by the dispatch table.
+            * Anything that reaches here must be bogus.
+            */
 
-               c->remoteid = remid;
-               if (error) {
-                   s->pktout = ssh2_pkt_init(SSH2_MSG_CHANNEL_OPEN_FAILURE);
-                   ssh2_pkt_adduint32(s->pktout, c->remoteid);
-                   ssh2_pkt_adduint32(s->pktout, SSH2_OPEN_CONNECT_FAILED);
-                   ssh2_pkt_addstring(s->pktout, error);
-                   ssh2_pkt_addstring(s->pktout, "en");        /* language tag */
-                   ssh2_pkt_send(ssh, s->pktout);
-                   logeventf(ssh, "Rejected channel open: %s", error);
-                   sfree(c);
-               } else {
-                   c->localid = alloc_channel_id(ssh);
-                   c->closes = 0;
-                   c->v.v2.locwindow = OUR_V2_WINSIZE;
-                   c->v.v2.remwindow = winsize;
-                   c->v.v2.remmaxpkt = pktsize;
-                   bufchain_init(&c->v.v2.outbuffer);
-                   add234(ssh->channels, c);
-                   s->pktout = ssh2_pkt_init(SSH2_MSG_CHANNEL_OPEN_CONFIRMATION);
-                   ssh2_pkt_adduint32(s->pktout, c->remoteid);
-                   ssh2_pkt_adduint32(s->pktout, c->localid);
-                   ssh2_pkt_adduint32(s->pktout, c->v.v2.locwindow);
-                   ssh2_pkt_adduint32(s->pktout, 0x4000UL);    /* our max pkt size */
-                   ssh2_pkt_send(ssh, s->pktout);
-               }
-           } else {
-               bombout(("Strange packet received: type %d", pktin->type));
-               crStopV;
-           }
+           bombout(("Strange packet received: type %d", pktin->type));
+           crStopV;
        } else if (ssh->mainchan) {
            /*
             * We have spare data. Add it to the channel buffer.
@@ -6814,12 +6994,31 @@ static void ssh2_protocol_setup(Ssh ssh)
     ssh->packet_dispatch[SSH2_MSG_DEBUG] = ssh2_msg_debug;
 }
 
+static void ssh2_timer(void *ctx, long now)
+{
+    Ssh ssh = (Ssh)ctx;
+
+    if (!ssh->kex_in_progress &&
+       now - ssh->next_rekey >= 0) {
+       do_ssh2_transport(ssh, "Initiating key re-exchange (timeout)",
+                         -1, NULL);
+    }
+}
+
 static void ssh2_protocol(Ssh ssh, unsigned char *in, int inlen,
                          struct Packet *pktin)
 {
     if (ssh->state == SSH_STATE_CLOSED)
        return;
 
+    if (pktin) {
+       ssh->incoming_data_size += pktin->encrypted_len;
+       if (!ssh->kex_in_progress &&
+           ssh->incoming_data_size > MAX_DATA_BEFORE_REKEY)
+           do_ssh2_transport(ssh, "Initiating key re-exchange "
+                             "(too much data received)", -1, NULL);
+    }
+
     if (pktin && ssh->packet_dispatch[pktin->type]) {
        ssh->packet_dispatch[pktin->type](ssh, pktin);
        return;
@@ -6933,10 +7132,18 @@ static const char *ssh_init(void *frontend_handle, void **backend_handle,
 
     ssh->protocol_initial_phase_done = FALSE;
 
+    ssh->pinger = NULL;
+
+    ssh->incoming_data_size = ssh->outgoing_data_size =
+       ssh->deferred_data_size = 0L;
+    ssh->kex_in_progress = FALSE;
+
     p = connect_to_host(ssh, host, port, realhost, nodelay, keepalive);
     if (p != NULL)
        return p;
 
+    random_ref();
+
     return NULL;
 }
 
@@ -7011,7 +7218,12 @@ static void ssh_free(void *handle)
     }
     if (ssh->s)
        ssh_do_close(ssh);
+    expire_timer_context(ssh);
     sfree(ssh);
+    if (ssh->pinger)
+       pinger_free(ssh->pinger);
+
+    random_unref();
 }
 
 /*
@@ -7026,6 +7238,7 @@ static void ssh_free(void *handle)
 static void ssh_reconfig(void *handle, Config *cfg)
 {
     Ssh ssh = (Ssh) handle;
+    pinger_reconfig(ssh->pinger, &ssh->cfg, cfg);
     ssh->cfg = *cfg;                  /* STRUCTURE COPY */
 }
 
@@ -7126,6 +7339,7 @@ static const struct telnet_special *ssh_get_specials(void *handle)
 {
     static const struct telnet_special ignore_special[] = {
        {"IGNORE message", TS_NOP},
+       {"Repeat key exchange", TS_REKEY},
     };
     static const struct telnet_special ssh2_session_specials[] = {
        {NULL, TS_SEP},
@@ -7167,7 +7381,6 @@ static const struct telnet_special *ssh_get_specials(void *handle)
        if (!(ssh->remote_bugs & BUG_CHOKES_ON_SSH1_IGNORE))
            ADD_SPECIALS(ignore_special);
     } else if (ssh->version == 2) {
-       /* XXX add rekey, when implemented */
        ADD_SPECIALS(ignore_special);
        if (ssh->mainchan)
            ADD_SPECIALS(ssh2_session_specials);
@@ -7221,6 +7434,11 @@ static void ssh_special(void *handle, Telnet_Special code)
            ssh2_pkt_addstring_start(pktout);
            ssh2_pkt_send_noqueue(ssh, pktout);
        }
+    } else if (code == TS_REKEY) {
+       if (!ssh->kex_in_progress && ssh->version == 2) {
+           do_ssh2_transport(ssh, "Initiating key re-exchange at"
+                             " user request", -1, NULL);
+       }
     } else if (code == TS_BRK) {
        if (ssh->state == SSH_STATE_CLOSED
            || ssh->state == SSH_STATE_PREPACKET) return;