Colin's const-fixing Patch Of Death. Seems to build fine on Windows
[u/mdw/putty] / ssh.c
diff --git a/ssh.c b/ssh.c
index 925c5b5..337cfa8 100644 (file)
--- a/ssh.c
+++ b/ssh.c
@@ -322,6 +322,8 @@ static unsigned char *ssh2_mpint_fmt(Bignum b, int *len);
 static void ssh2_pkt_addmp(Ssh, Bignum b);
 static int ssh2_pkt_construct(Ssh);
 static void ssh2_pkt_send(Ssh);
+static int do_ssh1_login(Ssh ssh, unsigned char *in, int inlen, int ispkt);
+static void do_ssh2_authconn(Ssh ssh, unsigned char *in, int inlen, int ispkt);
 
 /*
  * Buffer management constants. There are several of these for
@@ -515,6 +517,7 @@ 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);
 
 struct rdpkt1_state_tag {
     long len, pad, biglen, to_read;
@@ -648,12 +651,18 @@ struct ssh_tag {
      * potentially reconfigure port forwardings etc in mid-session.
      */
     Config cfg;
+
+    /*
+     * Used to transfer data back from async agent callbacks.
+     */
+    void *agent_response;
+    int agent_response_len;
 };
 
 #define logevent(s) logevent(ssh->frontend, s)
 
 /* logevent, only printf-formatted. */
-static void logeventf(Ssh ssh, char *fmt, ...)
+static void logeventf(Ssh ssh, const char *fmt, ...)
 {
     va_list ap;
     char *buf;
@@ -668,8 +677,7 @@ static void logeventf(Ssh ssh, char *fmt, ...)
 #define bombout(msg) \
     do { \
         char *text = dupprintf msg; \
-        ssh->state = SSH_STATE_CLOSED; \
-        if (ssh->s) { sk_close(ssh->s); ssh->s = NULL; } \
+       ssh_do_close(ssh); \
         logevent(text); \
         connection_fatal(ssh->frontend, "%s", text); \
         sfree(text); \
@@ -842,7 +850,7 @@ static int ssh1_rdpkt(Ssh ssh, unsigned char **data, int *datalen)
     if (ssh->cipher && detect_attack(ssh->crcda_ctx, ssh->pktin.data,
                                     st->biglen, NULL)) {
         bombout(("Network attack (CRC compensation) detected!"));
-        crReturn(0);
+        crStop(0);
     }
 
     if (ssh->cipher)
@@ -852,7 +860,7 @@ static int ssh1_rdpkt(Ssh ssh, unsigned char **data, int *datalen)
     st->gotcrc = GET_32BIT(ssh->pktin.data + st->biglen - 4);
     if (st->gotcrc != st->realcrc) {
        bombout(("Incorrect CRC received on packet"));
-       crReturn(0);
+       crStop(0);
     }
 
     ssh->pktin.body = ssh->pktin.data + st->pad + 1;
@@ -893,7 +901,7 @@ static int ssh1_rdpkt(Ssh ssh, unsigned char **data, int *datalen)
        long stringlen = GET_32BIT(ssh->pktin.body);
        if (stringlen + 4 != ssh->pktin.length) {
            bombout(("Received data packet with bogus string length"));
-           crReturn(0);
+           crStop(0);
        }
     }
 
@@ -926,7 +934,7 @@ static int ssh1_rdpkt(Ssh ssh, unsigned char **data, int *datalen)
        buf[nowlen + msglen] = '\0';
        /* logevent(buf); (this is now done within the bombout macro) */
        bombout(("Server sent disconnect message:\n\"%s\"", buf+nowlen));
-       crReturn(0);
+       crStop(0);
     }
 
     crFinish(0);
@@ -981,7 +989,7 @@ static int ssh2_rdpkt(Ssh ssh, unsigned char **data, int *datalen)
      */
     if (st->len < 0 || st->pad < 0 || st->len + st->pad < 0) {
        bombout(("Incoming packet was garbled on decryption"));
-       crReturn(0);
+       crStop(0);
     }
 
     /*
@@ -1030,7 +1038,7 @@ static int ssh2_rdpkt(Ssh ssh, unsigned char **data, int *datalen)
        && !ssh->scmac->verify(ssh->sc_mac_ctx, ssh->pktin.data, st->len + 4,
                               st->incoming_sequence)) {
        bombout(("Incorrect MAC received on packet"));
-       crReturn(0);
+       crStop(0);
     }
     st->incoming_sequence++;          /* whether or not we MACed */
 
@@ -1094,7 +1102,7 @@ static int ssh2_rdpkt(Ssh ssh, unsigned char **data, int *datalen)
                      ssh2_disconnect_reasons[reason] : "unknown",
                      buf+nowlen));
            sfree(buf);
-            crReturn(0);
+            crStop(0);
         }
         break;
       case SSH2_MSG_IGNORE:
@@ -1938,11 +1946,11 @@ static int do_ssh_init(Ssh ssh, unsigned char c)
 
     if (ssh->cfg.sshprot == 0 && !s->proto1) {
        bombout(("SSH protocol version 1 required by user but not provided by server"));
-       crReturn(0);
+       crStop(0);
     }
     if (ssh->cfg.sshprot == 3 && !s->proto2) {
        bombout(("SSH protocol version 2 required by user but not provided by server"));
-       crReturn(0);
+       crStop(0);
     }
 
     if (s->proto2 && (ssh->cfg.sshprot >= 2 || !s->proto1)) {
@@ -2037,19 +2045,47 @@ static void ssh_gotdata(Ssh ssh, unsigned char *data, int datalen)
     crFinishV;
 }
 
-static int ssh_closing(Plug plug, char *error_msg, int error_code,
-                      int calling_back)
+static void ssh_do_close(Ssh ssh)
 {
-    Ssh ssh = (Ssh) plug;
+    int i;
+    struct ssh_channel *c;
+
     ssh->state = SSH_STATE_CLOSED;
     if (ssh->s) {
         sk_close(ssh->s);
         ssh->s = NULL;
     }
+    /*
+     * Now we must shut down any port and X forwardings going
+     * through this connection.
+     */
+    if (ssh->channels) {
+       for (i = 0; NULL != (c = index234(ssh->channels, i)); i++) {
+           switch (c->type) {
+             case CHAN_X11:
+               x11_close(c->u.x11.s);
+               break;
+             case CHAN_SOCKDATA:
+               pfd_close(c->u.pfd.s);
+               break;
+           }
+           del234(ssh->channels, c);
+           if (ssh->version == 2)
+               bufchain_clear(&c->v.v2.outbuffer);
+           sfree(c);
+       }
+    }
+}
+
+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. */
        logevent(error_msg);
-       connection_fatal(ssh->frontend, error_msg);
+       connection_fatal(ssh->frontend, "%s", error_msg);
     } else {
        /* Otherwise, the remote side closed the connection normally. */
     }
@@ -2061,10 +2097,7 @@ 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) {
-       if (ssh->s) {
-           sk_close(ssh->s);
-           ssh->s = NULL;
-       }
+       ssh_do_close(ssh);
        return 0;
     }
     return 1;
@@ -2087,8 +2120,8 @@ static void ssh_sent(Plug plug, int bufsize)
  * Also places the canonical host name into `realhost'. It must be
  * freed by the caller.
  */
-static char *connect_to_host(Ssh ssh, char *host, int port,
-                            char **realhost, int nodelay)
+static const char *connect_to_host(Ssh ssh, char *host, int port,
+                                  char **realhost, int nodelay)
 {
     static const struct plug_function_table fn_table = {
        ssh_closing,
@@ -2098,7 +2131,7 @@ static char *connect_to_host(Ssh ssh, char *host, int port,
     };
 
     SockAddr addr;
-    char *err;
+    const char *err;
 
     ssh->savedhost = snewn(1 + strlen(host), char);
     if (!ssh->savedhost)
@@ -2180,7 +2213,7 @@ static void ssh_throttle_all(Ssh ssh, int enable, int bufsize)
            /* Agent channels require no buffer management. */
            break;
          case CHAN_SOCKDATA:
-           pfd_override_throttle(c->u.x11.s, enable);
+           pfd_override_throttle(c->u.pfd.s, enable);
            break;
        }
     }
@@ -2258,6 +2291,44 @@ static int process_userpass_input(Ssh ssh, unsigned char *in, int inlen)
     return 0;
 }
 
+void ssh_agent_callback(void *sshv, void *reply, int replylen)
+{
+    Ssh ssh = (Ssh) sshv;
+
+    ssh->agent_response = reply;
+    ssh->agent_response_len = replylen;
+
+    if (ssh->version == 1)
+       do_ssh1_login(ssh, NULL, -1, 0);
+    else
+       do_ssh2_authconn(ssh, NULL, -1, 0);
+}
+
+void ssh_agentf_callback(void *cv, void *reply, int replylen)
+{
+    struct ssh_channel *c = (struct ssh_channel *)cv;
+    Ssh ssh = c->ssh;
+    void *sentreply = reply;
+
+    if (!sentreply) {
+       /* Fake SSH_AGENT_FAILURE. */
+       sentreply = "\0\0\0\1\5";
+       replylen = 5;
+    }
+    if (ssh->version == 2) {
+       ssh2_add_channel_data(c, sentreply, replylen);
+       ssh2_try_send(c);
+    } else {
+       send_packet(ssh, SSH1_MSG_CHANNEL_DATA,
+                   PKT_INT, c->remoteid,
+                   PKT_INT, replylen,
+                   PKT_DATA, sentreply, replylen,
+                   PKT_END);
+    }
+    if (reply)
+       sfree(reply);
+}
+
 /*
  * Handle the key exchange and user authentication phases.
  */
@@ -2301,7 +2372,7 @@ static int do_ssh1_login(Ssh ssh, unsigned char *in, int inlen, int ispkt)
 
     if (ssh->pktin.type != SSH1_SMSG_PUBLIC_KEY) {
        bombout(("Public key packet not received"));
-       crReturn(0);
+       crStop(0);
     }
 
     logevent("Received public keys");
@@ -2415,7 +2486,7 @@ static int do_ssh1_login(Ssh ssh, unsigned char *in, int inlen, int ispkt)
            else
                /* shouldn't happen */
                bombout(("No supported ciphers found"));
-           crReturn(0);
+           crStop(0);
        }
 
        /* Warn about chosen cipher if necessary. */
@@ -2460,7 +2531,7 @@ static int do_ssh1_login(Ssh ssh, unsigned char *in, int inlen, int ispkt)
 
     if (ssh->pktin.type != SSH1_SMSG_SUCCESS) {
        bombout(("Encryption not successfully enabled"));
-       crReturn(0);
+       crStop(0);
     }
 
     logevent("Successfully started encryption");
@@ -2477,7 +2548,7 @@ static int do_ssh1_login(Ssh ssh, unsigned char *in, int inlen, int ispkt)
                     */
                    logevent("No username provided. Abandoning session.");
                     ssh_closing((Plug)ssh, NULL, 0, 0);
-                   crReturn(1);
+                   crStop(1);
                }
            } else {
                int ret;               /* need not be kept over crReturn */
@@ -2544,7 +2615,19 @@ static int do_ssh1_login(Ssh ssh, unsigned char *in, int inlen, int ispkt)
            /* Request the keys held by the agent. */
            PUT_32BIT(s->request, 1);
            s->request[4] = SSH1_AGENTC_REQUEST_RSA_IDENTITIES;
-           agent_query(s->request, 5, &r, &s->responselen);
+           if (!agent_query(s->request, 5, &r, &s->responselen,
+                            ssh_agent_callback, ssh)) {
+               do {
+                   crReturn(0);
+                   if (ispkt) {
+                       bombout(("Unexpected data from server while waiting"
+                                " for agent response"));
+                       crStop(0);
+                   }
+               } while (ispkt || inlen > 0);
+               r = ssh->agent_response;
+               s->responselen = ssh->agent_response_len;
+           }
            s->response = (unsigned char *) r;
            if (s->response && s->responselen >= 5 &&
                s->response[4] == SSH1_AGENT_RSA_IDENTITIES_ANSWER) {
@@ -2606,9 +2689,23 @@ static int do_ssh1_login(Ssh ssh, unsigned char *in, int inlen, int ispkt)
                        memcpy(q, s->session_id, 16);
                        q += 16;
                        PUT_32BIT(q, 1);        /* response format */
-                       agent_query(agentreq, len + 4, &vret, &retlen);
+                       if (!agent_query(agentreq, len + 4, &vret, &retlen,
+                                        ssh_agent_callback, ssh)) {
+                           sfree(agentreq);
+                           do {
+                               crReturn(0);
+                               if (ispkt) {
+                                   bombout(("Unexpected data from server"
+                                            " while waiting for agent"
+                                            " response"));
+                                   crStop(0);
+                               }
+                           } while (ispkt || inlen > 0);
+                           vret = ssh->agent_response;
+                           retlen = ssh->agent_response_len;
+                       } else
+                           sfree(agentreq);
                        ret = vret;
-                       sfree(agentreq);
                        if (ret) {
                            if (ret[4] == SSH1_AGENT_RSA_RESPONSE) {
                                logevent("Sending Pageant's response");
@@ -2755,7 +2852,7 @@ static int do_ssh1_login(Ssh ssh, unsigned char *in, int inlen, int ispkt)
                logevent("Unable to authenticate");
                connection_fatal(ssh->frontend, "Unable to authenticate");
                 ssh_closing((Plug)ssh, NULL, 0, 0);
-               crReturn(1);
+               crStop(1);
            }
        } else {
            /* Prompt may have come from server. We've munged it a bit, so
@@ -2810,7 +2907,7 @@ static int do_ssh1_login(Ssh ssh, unsigned char *in, int inlen, int ispkt)
            }
            if (ssh->pktin.type != SSH1_SMSG_AUTH_RSA_CHALLENGE) {
                bombout(("Bizarre response to offer of public key"));
-               crReturn(0);
+               crStop(0);
            }
 
            {
@@ -2846,7 +2943,7 @@ static int do_ssh1_login(Ssh ssh, unsigned char *in, int inlen, int ispkt)
                continue;              /* go and try password */
            } else if (ssh->pktin.type != SSH1_SMSG_SUCCESS) {
                bombout(("Bizarre response to RSA authentication response"));
-               crReturn(0);
+               crStop(0);
            }
 
            break;                     /* we're through! */
@@ -2979,7 +3076,7 @@ static int do_ssh1_login(Ssh ssh, unsigned char *in, int inlen, int ispkt)
            logevent("Authentication refused");
        } else if (ssh->pktin.type != SSH1_SMSG_SUCCESS) {
            bombout(("Strange packet received, type %d", ssh->pktin.type));
-           crReturn(0);
+           crStop(0);
        }
     }
 
@@ -2992,6 +3089,11 @@ void sshfwd_close(struct ssh_channel *c)
 {
     Ssh ssh = c->ssh;
 
+    if (ssh->state != SSH_STATE_SESSION) {
+       assert(ssh->state == SSH_STATE_CLOSED);
+       return;
+    }
+
     if (c && !c->closes) {
        /*
         * If the channel's remoteid is -1, we have sent
@@ -3026,6 +3128,11 @@ 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);
+       return 0;
+    }
+
     if (ssh->version == 1) {
        send_packet(ssh, SSH1_MSG_CHANNEL_DATA,
                    PKT_INT, c->remoteid,
@@ -3048,6 +3155,11 @@ 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);
+       return;
+    }
+
     if (ssh->version == 1) {
        if (c->v.v1.throttling && bufsize < SSH1_BUFFER_LIMIT) {
            c->v.v1.throttling = 0;
@@ -3079,7 +3191,7 @@ static void ssh1_protocol(Ssh ssh, unsigned char *in, int inlen, int ispkt)
        if (ssh->pktin.type != SSH1_SMSG_SUCCESS
            && ssh->pktin.type != SSH1_SMSG_FAILURE) {
            bombout(("Protocol confusion"));
-           crReturnV;
+           crStopV;
        } else if (ssh->pktin.type == SSH1_SMSG_FAILURE) {
            logevent("Agent forwarding refused");
        } else {
@@ -3109,7 +3221,7 @@ static void ssh1_protocol(Ssh ssh, unsigned char *in, int inlen, int ispkt)
        if (ssh->pktin.type != SSH1_SMSG_SUCCESS
            && ssh->pktin.type != SSH1_SMSG_FAILURE) {
            bombout(("Protocol confusion"));
-           crReturnV;
+           crStopV;
        } else if (ssh->pktin.type == SSH1_SMSG_FAILURE) {
            logevent("X11 forwarding refused");
        } else {
@@ -3177,6 +3289,7 @@ static void ssh1_protocol(Ssh ssh, unsigned char *in, int inlen, int ispkt)
                }
            } else {
                while (*ssh->portfwd_strptr) ssh->portfwd_strptr++;
+               dport = dserv = -1;
            }
            sport = atoi(sports);
            sserv = 0;
@@ -3244,7 +3357,7 @@ static void ssh1_protocol(Ssh ssh, unsigned char *in, int inlen, int ispkt)
                        if (ssh->pktin.type != SSH1_SMSG_SUCCESS
                            && ssh->pktin.type != SSH1_SMSG_FAILURE) {
                            bombout(("Protocol confusion"));
-                           crReturnV;
+                           crStopV;
                        } else if (ssh->pktin.type == SSH1_SMSG_FAILURE) {
                            c_write_str(ssh, "Server refused port"
                                        " forwarding\r\n");
@@ -3269,7 +3382,7 @@ static void ssh1_protocol(Ssh ssh, unsigned char *in, int inlen, int ispkt)
        if (ssh->pktin.type != SSH1_SMSG_SUCCESS
            && ssh->pktin.type != SSH1_SMSG_FAILURE) {
            bombout(("Protocol confusion"));
-           crReturnV;
+           crStopV;
        } else if (ssh->pktin.type == SSH1_SMSG_FAILURE) {
            c_write_str(ssh, "Server refused to allocate pty\r\n");
            ssh->editing = ssh->echoing = 1;
@@ -3287,7 +3400,7 @@ static void ssh1_protocol(Ssh ssh, unsigned char *in, int inlen, int ispkt)
        if (ssh->pktin.type != SSH1_SMSG_SUCCESS
            && ssh->pktin.type != SSH1_SMSG_FAILURE) {
            bombout(("Protocol confusion"));
-           crReturnV;
+           crStopV;
        } else if (ssh->pktin.type == SSH1_SMSG_FAILURE) {
            c_write_str(ssh, "Server refused to compress\r\n");
        }
@@ -3347,7 +3460,7 @@ static void ssh1_protocol(Ssh ssh, unsigned char *in, int inlen, int ispkt)
            } else if (ssh->pktin.type == SSH1_MSG_DISCONNECT) {
                 ssh_closing((Plug)ssh, NULL, 0, 0);
                logevent("Received disconnect request");
-               crReturnV;
+               crStopV;
            } else if (ssh->pktin.type == SSH1_SMSG_X11_OPEN) {
                /* Remote side is trying to open a channel to talk to our
                 * X-Server. Give them back a local channel number. */
@@ -3415,7 +3528,8 @@ static void ssh1_protocol(Ssh ssh, unsigned char *in, int inlen, int ispkt)
                struct ssh_rportfwd pf;
                int hostsize, port;
                char host[256], buf[1024];
-               char *p, *h, *e;
+               char *p, *h;
+               const char *e;
                c = snew(struct ssh_channel);
                c->ssh = ssh;
 
@@ -3541,6 +3655,7 @@ static void ssh1_protocol(Ssh ssh, unsigned char *in, int inlen, int ispkt)
                             ssh->pktin.type == SSH1_MSG_CHANNEL_CLOSE ? "" :
                             "_CONFIRMATION", c ? "half-open" : "nonexistent",
                             i));
+                   crStopV;
                }
            } else if (ssh->pktin.type == SSH1_MSG_CHANNEL_DATA) {
                /* Data sent down one of our channels. */
@@ -3550,7 +3665,7 @@ static void ssh1_protocol(Ssh ssh, unsigned char *in, int inlen, int ispkt)
                struct ssh_channel *c;
                c = find234(ssh->channels, &i, ssh_channelfind);
                if (c) {
-                   int bufsize;
+                   int bufsize = 0;
                    switch (c->type) {
                      case CHAN_X11:
                        bufsize = x11_send(c->u.x11.s, (char *)p, len);
@@ -3587,25 +3702,13 @@ static void ssh1_protocol(Ssh ssh, unsigned char *in, int inlen, int ispkt)
                                c->u.a.lensofar += l;
                            }
                            if (c->u.a.lensofar == c->u.a.totallen) {
-                               void *reply, *sentreply;
+                               void *reply;
                                int replylen;
-                               agent_query(c->u.a.message,
-                                           c->u.a.totallen, &reply,
-                                           &replylen);
-                               if (reply)
-                                   sentreply = reply;
-                               else {
-                                   /* Fake SSH_AGENT_FAILURE. */
-                                   sentreply = "\0\0\0\1\5";
-                                   replylen = 5;
-                               }
-                               send_packet(ssh, SSH1_MSG_CHANNEL_DATA,
-                                           PKT_INT, c->remoteid,
-                                           PKT_INT, replylen,
-                                           PKT_DATA, sentreply, replylen,
-                                           PKT_END);
-                               if (reply)
-                                   sfree(reply);
+                               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;
                            }
@@ -3638,10 +3741,10 @@ static void ssh1_protocol(Ssh ssh, unsigned char *in, int inlen, int ispkt)
                  * we've sent EXIT_CONFIRMATION.
                  */
                 ssh_closing((Plug)ssh, NULL, 0, 0);
-                crReturnV;
+                crStopV;
            } else {
                bombout(("Strange packet received: type %d", ssh->pktin.type));
-               crReturnV;
+               crStopV;
            }
        } else {
            while (inlen > 0) {
@@ -3914,7 +4017,7 @@ static int do_ssh2_transport(Ssh ssh, unsigned char *in, int inlen, int ispkt)
 
        if (ssh->pktin.type != SSH2_MSG_KEXINIT) {
            bombout(("expected key exchange packet from server"));
-           crReturn(0);
+           crStop(0);
        }
        ssh->kex = NULL;
        ssh->hostkey = NULL;
@@ -3965,7 +4068,7 @@ static int do_ssh2_transport(Ssh ssh, unsigned char *in, int inlen, int ispkt)
        if (!s->cscipher_tobe) {
            bombout(("Couldn't agree a client-to-server cipher (available: %s)",
                     str ? str : "(null)"));
-           crReturn(0);
+           crStop(0);
        }
 
        ssh2_pkt_getstring(ssh, &str, &len);    /* server->client cipher */
@@ -3991,7 +4094,7 @@ static int do_ssh2_transport(Ssh ssh, unsigned char *in, int inlen, int ispkt)
        if (!s->sccipher_tobe) {
            bombout(("Couldn't agree a server-to-client cipher (available: %s)",
                     str ? str : "(null)"));
-           crReturn(0);
+           crStop(0);
        }
 
        ssh2_pkt_getstring(ssh, &str, &len);    /* client->server mac */
@@ -4064,7 +4167,7 @@ static int do_ssh2_transport(Ssh ssh, unsigned char *in, int inlen, int ispkt)
        crWaitUntil(ispkt);
        if (ssh->pktin.type != SSH2_MSG_KEX_DH_GEX_GROUP) {
            bombout(("expected key exchange group packet from server"));
-           crReturn(0);
+           crStop(0);
        }
        s->p = ssh2_pkt_getmp(ssh);
        s->g = ssh2_pkt_getmp(ssh);
@@ -4090,7 +4193,7 @@ static int do_ssh2_transport(Ssh ssh, unsigned char *in, int inlen, int ispkt)
     crWaitUntil(ispkt);
     if (ssh->pktin.type != s->kex_reply_value) {
        bombout(("expected key exchange reply packet from server"));
-       crReturn(0);
+       crStop(0);
     }
     ssh2_pkt_getstring(ssh, &s->hostkeydata, &s->hostkeylen);
     s->f = ssh2_pkt_getmp(ssh);
@@ -4122,7 +4225,7 @@ static int do_ssh2_transport(Ssh ssh, unsigned char *in, int inlen, int ispkt)
        !ssh->hostkey->verifysig(s->hkey, s->sigdata, s->siglen,
                                 (char *)s->exchange_hash, 20)) {
        bombout(("Server's host key did not match the signature supplied"));
-       crReturn(0);
+       crStop(0);
     }
 
     /*
@@ -4154,7 +4257,7 @@ static int do_ssh2_transport(Ssh ssh, unsigned char *in, int inlen, int ispkt)
     crWaitUntil(ispkt);
     if (ssh->pktin.type != SSH2_MSG_NEWKEYS) {
        bombout(("expected new-keys packet from server"));
-       crReturn(0);
+       crStop(0);
     }
 
     /*
@@ -4369,7 +4472,7 @@ static void do_ssh2_authconn(Ssh ssh, unsigned char *in, int inlen, int ispkt)
     crWaitUntilV(ispkt);
     if (ssh->pktin.type != SSH2_MSG_SERVICE_ACCEPT) {
        bombout(("Server refused user authentication protocol"));
-       crReturnV;
+       crStopV;
     }
 
     /*
@@ -4418,7 +4521,7 @@ static void do_ssh2_authconn(Ssh ssh, unsigned char *in, int inlen, int ispkt)
                     */
                    logevent("No username provided. Abandoning session.");
                     ssh_closing((Plug)ssh, NULL, 0, 0);
-                   crReturnV;
+                   crStopV;
                }
            } else {
                int ret;               /* need not be saved across crReturn */
@@ -4535,7 +4638,7 @@ static void do_ssh2_authconn(Ssh ssh, unsigned char *in, int inlen, int ispkt)
            } else if (ssh->pktin.type != SSH2_MSG_USERAUTH_FAILURE) {
                bombout(("Strange packet received during authentication: type %d",
                         ssh->pktin.type));
-               crReturnV;
+               crStopV;
            }
 
            s->gotit = FALSE;
@@ -4631,7 +4734,19 @@ static void do_ssh2_authconn(Ssh ssh, unsigned char *in, int inlen, int ispkt)
                /* Request the keys held by the agent. */
                PUT_32BIT(s->request, 1);
                s->request[4] = SSH2_AGENTC_REQUEST_IDENTITIES;
-               agent_query(s->request, 5, &r, &s->responselen);
+               if (!agent_query(s->request, 5, &r, &s->responselen,
+                                ssh_agent_callback, ssh)) {
+                   do {
+                       crReturnV;
+                       if (ispkt) {
+                           bombout(("Unexpected data from server while"
+                                    " waiting for agent response"));
+                           crStopV;
+                       }
+                   } while (ispkt || inlen > 0);
+                   r = ssh->agent_response;
+                   s->responselen = ssh->agent_response_len;
+               }
                s->response = (unsigned char *) r;
                if (s->response && s->responselen >= 5 &&
                    s->response[4] == SSH2_AGENT_IDENTITIES_ANSWER) {
@@ -4735,7 +4850,21 @@ static void do_ssh2_authconn(Ssh ssh, unsigned char *in, int inlen, int ispkt)
                        s->q += ssh->pktout.length - 5;
                        /* And finally the (zero) flags word. */
                        PUT_32BIT(s->q, 0);
-                       agent_query(s->agentreq, s->len + 4, &vret, &s->retlen);
+                       if (!agent_query(s->agentreq, s->len + 4,
+                                        &vret, &s->retlen,
+                                        ssh_agent_callback, ssh)) {
+                           do {
+                               crReturnV;
+                               if (ispkt) {
+                                   bombout(("Unexpected data from server"
+                                            " while waiting for agent"
+                                            " response"));
+                                   crStopV;
+                               }
+                           } while (ispkt || inlen > 0);
+                           vret = ssh->agent_response;
+                           s->retlen = ssh->agent_response_len;
+                       }
                        s->ret = vret;
                        sfree(s->agentreq);
                        if (s->ret) {
@@ -4932,7 +5061,7 @@ static void do_ssh2_authconn(Ssh ssh, unsigned char *in, int inlen, int ispkt)
                        connection_fatal(ssh->frontend,
                                         "Unable to authenticate");
                         ssh_closing((Plug)ssh, NULL, 0, 0);
-                       crReturnV;
+                       crStopV;
                    }
                } else {
                    int ret;           /* need not be saved across crReturn */
@@ -5121,7 +5250,7 @@ static void do_ssh2_authconn(Ssh ssh, unsigned char *in, int inlen, int ispkt)
                ssh2_pkt_addstring(ssh, "en");  /* language tag */
                ssh2_pkt_send(ssh);
                 ssh_closing((Plug)ssh, NULL, 0, 0);
-               crReturnV;
+               crStopV;
            }
        }
     } while (!s->we_are_in);
@@ -5149,12 +5278,12 @@ static void do_ssh2_authconn(Ssh ssh, unsigned char *in, int inlen, int ispkt)
     crWaitUntilV(ispkt);
     if (ssh->pktin.type != SSH2_MSG_CHANNEL_OPEN_CONFIRMATION) {
        bombout(("Server refused to open a session"));
-       crReturnV;
+       crStopV;
        /* FIXME: error data comes back in FAILURE packet */
     }
     if (ssh2_pkt_getuint32(ssh) != ssh->mainchan->localid) {
        bombout(("Server's channel confirmation cited wrong channel"));
-       crReturnV;
+       crStopV;
     }
     ssh->mainchan->remoteid = ssh2_pkt_getuint32(ssh);
     ssh->mainchan->type = CHAN_MAINSESSION;
@@ -5200,7 +5329,7 @@ static void do_ssh2_authconn(Ssh ssh, unsigned char *in, int inlen, int ispkt)
            if (ssh->pktin.type != SSH2_MSG_CHANNEL_FAILURE) {
                bombout(("Unexpected response to X11 forwarding request:"
                         " packet type %d", ssh->pktin.type));
-               crReturnV;
+               crStopV;
            }
            logevent("X11 forwarding refused");
        } else {
@@ -5271,6 +5400,7 @@ static void do_ssh2_authconn(Ssh ssh, unsigned char *in, int inlen, int ispkt)
                }
            } else {
                while (*ssh->portfwd_strptr) ssh->portfwd_strptr++;
+               dport = dserv = -1;
            }
            sport = atoi(sports);
            sserv = 0;
@@ -5355,7 +5485,7 @@ static void do_ssh2_authconn(Ssh ssh, unsigned char *in, int inlen, int ispkt)
                                bombout(("Unexpected response to port "
                                         "forwarding request: packet type %d",
                                         ssh->pktin.type));
-                               crReturnV;
+                               crStopV;
                            }
                            logevent("Server refused this port forwarding");
                        } else {
@@ -5394,7 +5524,7 @@ static void do_ssh2_authconn(Ssh ssh, unsigned char *in, int inlen, int ispkt)
            if (ssh->pktin.type != SSH2_MSG_CHANNEL_FAILURE) {
                bombout(("Unexpected response to agent forwarding request:"
                         " packet type %d", ssh->pktin.type));
-               crReturnV;
+               crStopV;
            }
            logevent("Agent forwarding refused");
        } else {
@@ -5437,7 +5567,7 @@ static void do_ssh2_authconn(Ssh ssh, unsigned char *in, int inlen, int ispkt)
            if (ssh->pktin.type != SSH2_MSG_CHANNEL_FAILURE) {
                bombout(("Unexpected response to pty request:"
                         " packet type %d", ssh->pktin.type));
-               crReturnV;
+               crStopV;
            }
            c_write_str(ssh, "Server refused to allocate pty\r\n");
            ssh->editing = ssh->echoing = 1;
@@ -5495,7 +5625,7 @@ static void do_ssh2_authconn(Ssh ssh, unsigned char *in, int inlen, int ispkt)
            if (ssh->pktin.type != SSH2_MSG_CHANNEL_FAILURE) {
                bombout(("Unexpected response to shell/command request:"
                         " packet type %d", ssh->pktin.type));
-               crReturnV;
+               crStopV;
            }
            /*
             * We failed to start the command. If this is the
@@ -5509,7 +5639,7 @@ static void do_ssh2_authconn(Ssh ssh, unsigned char *in, int inlen, int ispkt)
                continue;
            }
            bombout(("Server refused to start a shell/command"));
-           crReturnV;
+           crStopV;
        } else {
            logevent("Started a shell/command");
        }
@@ -5546,7 +5676,7 @@ static void do_ssh2_authconn(Ssh ssh, unsigned char *in, int inlen, int ispkt)
                    continue;          /* extended but not stderr */
                ssh2_pkt_getstring(ssh, &data, &length);
                if (data) {
-                   int bufsize;
+                   int bufsize = 0;
                    c->v.v2.locwindow -= length;
                    switch (c->type) {
                      case CHAN_MAINSESSION:
@@ -5589,22 +5719,13 @@ static void do_ssh2_authconn(Ssh ssh, unsigned char *in, int inlen, int ispkt)
                                c->u.a.lensofar += l;
                            }
                            if (c->u.a.lensofar == c->u.a.totallen) {
-                               void *reply, *sentreply;
+                               void *reply;
                                int replylen;
-                               agent_query(c->u.a.message,
-                                           c->u.a.totallen, &reply,
-                                           &replylen);
-                               if (reply)
-                                   sentreply = reply;
-                               else {
-                                   /* Fake SSH_AGENT_FAILURE. */
-                                   sentreply = "\0\0\0\1\5";
-                                   replylen = 5;
-                               }
-                               ssh2_add_channel_data(c, sentreply, replylen);
-                               s->try_send = TRUE;
-                               if (reply)
-                                   sfree(reply);
+                               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;
                            }
@@ -5648,6 +5769,7 @@ static void do_ssh2_authconn(Ssh ssh, unsigned char *in, int inlen, int ispkt)
                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) {
@@ -5700,7 +5822,7 @@ static void do_ssh2_authconn(Ssh ssh, unsigned char *in, int inlen, int ispkt)
                    ssh2_pkt_send(ssh);
 #endif
                     ssh_closing((Plug)ssh, NULL, 0, 0);
-                   crReturnV;
+                   crStopV;
                }
                continue;              /* remote sends close; ignore (FIXME) */
            } else if (ssh->pktin.type == SSH2_MSG_CHANNEL_WINDOW_ADJUST) {
@@ -5778,7 +5900,7 @@ static void do_ssh2_authconn(Ssh ssh, unsigned char *in, int inlen, int ispkt)
                    ssh2_pkt_send(ssh);
                    connection_fatal(ssh->frontend, "%s", buf);
                     ssh_closing((Plug)ssh, NULL, 0, 0);
-                   crReturnV;
+                   crStopV;
                }
 
                /*
@@ -5879,8 +6001,10 @@ static void do_ssh2_authconn(Ssh ssh, unsigned char *in, int inlen, int ispkt)
                    if (realpf == NULL) {
                        error = "Remote port is not recognised";
                    } else {
-                       char *e = pfd_newconnect(&c->u.pfd.s, realpf->dhost,
-                                                realpf->dport, c, &ssh->cfg);
+                       const char *e = pfd_newconnect(&c->u.pfd.s,
+                                                      realpf->dhost,
+                                                      realpf->dport, c,
+                                                      &ssh->cfg);
                        logeventf(ssh, "Received remote port open request"
                                  " for %s:%d", realpf->dhost, realpf->dport);
                        if (e != NULL) {
@@ -5929,7 +6053,7 @@ static void do_ssh2_authconn(Ssh ssh, unsigned char *in, int inlen, int ispkt)
                }
            } else {
                bombout(("Strange packet received: type %d", ssh->pktin.type));
-               crReturnV;
+               crStopV;
            }
        } else {
            /*
@@ -5989,11 +6113,11 @@ static void ssh2_protocol(Ssh ssh, unsigned char *in, int inlen, int ispkt)
  *
  * Returns an error message, or NULL on success.
  */
-static char *ssh_init(void *frontend_handle, void **backend_handle,
-                     Config *cfg,
-                     char *host, int port, char **realhost, int nodelay)
+static const char *ssh_init(void *frontend_handle, void **backend_handle,
+                           Config *cfg,
+                           char *host, int port, char **realhost, int nodelay)
 {
-    char *p;
+    const char *p;
     Ssh ssh;
 
     ssh = snew(struct ssh_tag);
@@ -6137,7 +6261,7 @@ static void ssh_free(void *handle)
     sfree(ssh->do_ssh2_authconn_state);
     
     if (ssh->s)
-       sk_close(ssh->s);
+       ssh_do_close(ssh);
     sfree(ssh);
 }