]> asedeno.scripts.mit.edu Git - PuTTY.git/blobdiff - ssh.c
Check the x argument to check_boundary() more carefully.
[PuTTY.git] / ssh.c
diff --git a/ssh.c b/ssh.c
index 8bcb1e8564a10c2eca99fe03661c48116a0594d9..1077209ae8e1fee800c0c0258db04da3b2742934 100644 (file)
--- a/ssh.c
+++ b/ssh.c
@@ -75,6 +75,11 @@ static const char *const ssh2_disconnect_reasons[] = {
 #define BUG_SSH2_MAXPKT                                256
 #define BUG_CHOKES_ON_SSH2_IGNORE               512
 #define BUG_CHOKES_ON_WINADJ                   1024
+#define BUG_SENDS_LATE_REQUEST_REPLY           2048
+#define BUG_SSH2_OLDGEX                        4096
+
+#define DH_MIN_SIZE 1024
+#define DH_MAX_SIZE 8192
 
 /*
  * Codes for terminal modes.
@@ -246,6 +251,7 @@ static char *ssh2_pkt_type(Pkt_KCtx pkt_kctx, Pkt_ACtx pkt_actx, int type)
     translate(SSH2_MSG_NEWKEYS);
     translatek(SSH2_MSG_KEXDH_INIT, SSH2_PKTCTX_DHGROUP);
     translatek(SSH2_MSG_KEXDH_REPLY, SSH2_PKTCTX_DHGROUP);
+    translatek(SSH2_MSG_KEX_DH_GEX_REQUEST_OLD, SSH2_PKTCTX_DHGEX);
     translatek(SSH2_MSG_KEX_DH_GEX_REQUEST, SSH2_PKTCTX_DHGEX);
     translatek(SSH2_MSG_KEX_DH_GEX_GROUP, SSH2_PKTCTX_DHGEX);
     translatek(SSH2_MSG_KEX_DH_GEX_INIT, SSH2_PKTCTX_DHGEX);
@@ -354,6 +360,7 @@ static void do_ssh2_authconn(Ssh ssh, unsigned char *in, int inlen,
                             struct Packet *pktin);
 static void ssh2_channel_check_close(struct ssh_channel *c);
 static void ssh_channel_destroy(struct ssh_channel *c);
+static void ssh2_msg_something_unimplemented(Ssh ssh, struct Packet *pktin);
 
 /*
  * Buffer management constants. There are several of these for
@@ -1736,6 +1743,15 @@ static struct Packet *ssh2_rdpkt(Ssh ssh, unsigned char **data, int *datalen)
        }
     }
 
+    /*
+     * RFC 4253 doesn't explicitly say that completely empty packets
+     * with no type byte are forbidden, so treat them as deserving
+     * an SSH_MSG_UNIMPLEMENTED.
+     */
+    if (st->pktin->length <= 5) { /* == 5 we hope, but robustness */
+        ssh2_msg_something_unimplemented(ssh, st->pktin);
+        crStop(NULL);
+    }
     /*
      * pktin->body and pktin->length should identify the semantic
      * content of the packet, excluding the initial type byte.
@@ -2747,7 +2763,9 @@ static void ssh_detect_bugs(Ssh ssh, char *vstring)
     if (conf_get_int(ssh->conf, CONF_sshbug_rsapad2) == FORCE_ON ||
        (conf_get_int(ssh->conf, CONF_sshbug_rsapad2) == AUTO &&
         (wc_match("OpenSSH_2.[5-9]*", imp) ||
-         wc_match("OpenSSH_3.[0-2]*", imp)))) {
+         wc_match("OpenSSH_3.[0-2]*", imp) ||
+         wc_match("mod_sftp/0.[0-8]*", imp) ||
+         wc_match("mod_sftp/0.9.[0-8]", imp)))) {
        /*
         * These versions have the SSH-2 RSA padding bug.
         */
@@ -2802,6 +2820,17 @@ static void ssh_detect_bugs(Ssh ssh, char *vstring)
        logevent("We believe remote version has SSH-2 ignore bug");
     }
 
+    if (conf_get_int(ssh->conf, CONF_sshbug_oldgex2) == FORCE_ON ||
+       (conf_get_int(ssh->conf, CONF_sshbug_oldgex2) == AUTO &&
+        (wc_match("OpenSSH_2.[235]*", imp)))) {
+       /*
+        * These versions only support the original (pre-RFC4419)
+        * SSH-2 GEX request.
+        */
+       ssh->remote_bugs |= BUG_SSH2_OLDGEX;
+       logevent("We believe remote version has outdated SSH-2 GEX");
+    }
+
     if (conf_get_int(ssh->conf, CONF_sshbug_winadj) == FORCE_ON) {
        /*
         * Servers that don't support our winadj request for one
@@ -2810,6 +2839,23 @@ static void ssh_detect_bugs(Ssh ssh, char *vstring)
        ssh->remote_bugs |= BUG_CHOKES_ON_WINADJ;
        logevent("We believe remote version has winadj bug");
     }
+
+    if (conf_get_int(ssh->conf, CONF_sshbug_chanreq) == FORCE_ON ||
+       (conf_get_int(ssh->conf, CONF_sshbug_chanreq) == AUTO &&
+        (wc_match("OpenSSH_[2-5].*", imp) ||
+         wc_match("OpenSSH_6.[0-6]*", imp) ||
+         wc_match("dropbear_0.[2-4][0-9]*", imp) ||
+         wc_match("dropbear_0.5[01]*", imp)))) {
+       /*
+        * These versions have the SSH-2 channel request bug.
+        * OpenSSH 6.7 and above do not:
+        * https://bugzilla.mindrot.org/show_bug.cgi?id=1818
+        * dropbear_0.52 and above do not:
+        * https://secure.ucc.asn.au/hg/dropbear/rev/cd02449b709c
+        */
+       ssh->remote_bugs |= BUG_SENDS_LATE_REQUEST_REPLY;
+       logevent("We believe remote version has SSH-2 channel request bug");
+    }
 }
 
 /*
@@ -2944,11 +2990,13 @@ static int do_ssh_init(Ssh ssh, unsigned char c)
     s->proto2 = ssh_versioncmp(s->version, "1.99") >= 0;
 
     if (conf_get_int(ssh->conf, CONF_sshprot) == 0 && !s->proto1) {
-       bombout(("SSH protocol version 1 required by user but not provided by server"));
+       bombout(("SSH protocol version 1 required by configuration but "
+                "not provided by server"));
        crStop(0);
     }
     if (conf_get_int(ssh->conf, CONF_sshprot) == 3 && !s->proto2) {
-       bombout(("SSH protocol version 2 required by user but not provided by server"));
+       bombout(("SSH protocol version 2 required by configuration but "
+                "not provided by server"));
        crStop(0);
     }
 
@@ -3269,6 +3317,14 @@ static int ssh_do_close(Ssh ssh, int notify_exit)
        ssh->portfwds = NULL;
     }
 
+    /*
+     * Also stop attempting to connection-share.
+     */
+    if (ssh->connshare) {
+        sharestate_free(ssh->connshare);
+        ssh->connshare = NULL;
+    }
+
     return ret;
 }
 
@@ -3411,25 +3467,28 @@ static const char *connect_to_host(Ssh ssh, char *host, int port,
     
     loghost = conf_get_str(ssh->conf, CONF_loghost);
     if (*loghost) {
-       char *colon;
+       char *tmphost;
+        char *colon;
 
-       ssh->savedhost = dupstr(loghost);
+        tmphost = dupstr(loghost);
        ssh->savedport = 22;           /* default ssh port */
 
        /*
-        * A colon suffix on savedhost also lets us affect
-        * savedport.
-        * 
-        * (FIXME: do something about IPv6 address literals here.)
+        * A colon suffix on the hostname string also lets us affect
+        * savedport. (Unless there are multiple colons, in which case
+        * we assume this is an unbracketed IPv6 literal.)
         */
-       colon = strrchr(ssh->savedhost, ':');
-       if (colon) {
+       colon = host_strrchr(tmphost, ':');
+       if (colon && colon == host_strchr(tmphost, ':')) {
            *colon++ = '\0';
            if (*colon)
                ssh->savedport = atoi(colon);
        }
+
+        ssh->savedhost = host_strduptrim(tmphost);
+        sfree(tmphost);
     } else {
-       ssh->savedhost = dupstr(host);
+       ssh->savedhost = host_strduptrim(host);
        if (port < 0)
            port = 22;                 /* default ssh port */
        ssh->savedport = port;
@@ -3658,6 +3717,59 @@ static void ssh_disconnect(Ssh ssh, char *client_reason, char *wire_reason,
     sfree(error);
 }
 
+int verify_ssh_manual_host_key(Ssh ssh, const char *fingerprint,
+                               const struct ssh_signkey *ssh2keytype,
+                               void *ssh2keydata)
+{
+    if (!conf_get_str_nthstrkey(ssh->conf, CONF_ssh_manual_hostkeys, 0)) {
+        return -1;                     /* no manual keys configured */
+    }
+
+    if (fingerprint) {
+        /*
+         * The fingerprint string we've been given will have things
+         * like 'ssh-rsa 2048' at the front of it. Strip those off and
+         * narrow down to just the colon-separated hex block at the
+         * end of the string.
+         */
+        const char *p = strrchr(fingerprint, ' ');
+        fingerprint = p ? p+1 : fingerprint;
+        /* Quick sanity checks, including making sure it's in lowercase */
+        assert(strlen(fingerprint) == 16*3 - 1);
+        assert(fingerprint[2] == ':');
+        assert(fingerprint[strspn(fingerprint, "0123456789abcdef:")] == 0);
+
+        if (conf_get_str_str_opt(ssh->conf, CONF_ssh_manual_hostkeys,
+                                 fingerprint))
+            return 1;                  /* success */
+    }
+
+    if (ssh2keydata) {
+        /*
+         * Construct the base64-encoded public key blob and see if
+         * that's listed.
+         */
+        unsigned char *binblob;
+        char *base64blob;
+        int binlen, atoms, i;
+        binblob = ssh2keytype->public_blob(ssh2keydata, &binlen);
+        atoms = (binlen + 2) / 3;
+        base64blob = snewn(atoms * 4 + 1, char);
+        for (i = 0; i < atoms; i++)
+            base64_encode_atom(binblob + 3*i, binlen - 3*i, base64blob + 4*i);
+        base64blob[atoms * 4] = '\0';
+        sfree(binblob);
+        if (conf_get_str_str_opt(ssh->conf, CONF_ssh_manual_hostkeys,
+                                 base64blob)) {
+            sfree(base64blob);
+            return 1;                  /* success */
+        }
+        sfree(base64blob);
+    }
+
+    return 0;
+}
+
 /*
  * Handle the key exchange and user authentication phases.
  */
@@ -3781,29 +3893,39 @@ static int do_ssh1_login(Ssh ssh, unsigned char *in, int inlen,
        rsastr_fmt(keystr, &s->hostkey);
        rsa_fingerprint(fingerprint, sizeof(fingerprint), &s->hostkey);
 
-        ssh_set_frozen(ssh, 1);
-       s->dlgret = verify_ssh_host_key(ssh->frontend,
-                                        ssh->savedhost, ssh->savedport,
-                                        "rsa", keystr, fingerprint,
-                                        ssh_dialog_callback, ssh);
-       sfree(keystr);
-        if (s->dlgret < 0) {
-            do {
-                crReturn(0);
-                if (pktin) {
-                    bombout(("Unexpected data from server while waiting"
-                             " for user host key response"));
-                    crStop(0);
-                }
-            } while (pktin || inlen > 0);
-            s->dlgret = ssh->user_response;
-        }
-        ssh_set_frozen(ssh, 0);
+        /* First check against manually configured host keys. */
+        s->dlgret = verify_ssh_manual_host_key(ssh, fingerprint, NULL, NULL);
+        if (s->dlgret == 0) {          /* did not match */
+            bombout(("Host key did not appear in manually configured list"));
+            sfree(keystr);
+            crStop(0);
+        } else if (s->dlgret < 0) { /* none configured; use standard handling */
+            ssh_set_frozen(ssh, 1);
+            s->dlgret = verify_ssh_host_key(ssh->frontend,
+                                            ssh->savedhost, ssh->savedport,
+                                            "rsa", keystr, fingerprint,
+                                            ssh_dialog_callback, ssh);
+            sfree(keystr);
+            if (s->dlgret < 0) {
+                do {
+                    crReturn(0);
+                    if (pktin) {
+                        bombout(("Unexpected data from server while waiting"
+                                 " for user host key response"));
+                        crStop(0);
+                    }
+                } while (pktin || inlen > 0);
+                s->dlgret = ssh->user_response;
+            }
+            ssh_set_frozen(ssh, 0);
 
-        if (s->dlgret == 0) {
-           ssh_disconnect(ssh, "User aborted at host key verification",
-                          NULL, 0, TRUE);
-           crStop(0);
+            if (s->dlgret == 0) {
+                ssh_disconnect(ssh, "User aborted at host key verification",
+                               NULL, 0, TRUE);
+                crStop(0);
+            }
+        } else {
+            sfree(keystr);
         }
     }
 
@@ -4915,13 +5037,15 @@ static void ssh_setup_portfwd(Ssh ssh, Conf *conf)
        if (*kp == 'L' || *kp == 'R')
            type = *kp++;
 
-       if ((kp2 = strchr(kp, ':')) != NULL) {
+       if ((kp2 = host_strchr(kp, ':')) != NULL) {
            /*
             * There's a colon in the middle of the source port
             * string, which means that the part before it is
             * actually a source address.
             */
-           saddr = dupprintf("%.*s", (int)(kp2 - kp), kp);
+           char *saddr_tmp = dupprintf("%.*s", (int)(kp2 - kp), kp);
+            saddr = host_strduptrim(saddr_tmp);
+            sfree(saddr_tmp);
            sports = kp2+1;
        } else {
            saddr = NULL;
@@ -4948,9 +5072,9 @@ static void ssh_setup_portfwd(Ssh ssh, Conf *conf)
         } else {
             /* ordinary forwarding */
            vp = val;
-           vp2 = vp + strcspn(vp, ":");
+           vp2 = vp + host_strcspn(vp, ":");
            host = dupprintf("%.*s", (int)(vp2 - vp), vp);
-           if (vp2)
+           if (*vp2)
                vp2++;
            dports = vp2;
            dport = atoi(dports);
@@ -6205,6 +6329,10 @@ static void do_ssh2_transport(Ssh ssh, void *vin, int inlen,
 
        pktin->savedpos += 16;          /* skip garbage cookie */
        ssh_pkt_getstring(pktin, &str, &len);    /* key exchange algorithms */
+        if (!str) {
+            bombout(("KEXINIT packet was incomplete"));
+            crStopV;
+        }
 
        preferred = NULL;
        for (i = 0; i < s->n_preferred_kex; i++) {
@@ -6224,8 +6352,8 @@ static void do_ssh2_transport(Ssh ssh, void *vin, int inlen,
                break;
        }
        if (!ssh->kex) {
-           bombout(("Couldn't agree a key exchange algorithm (available: %s)",
-                    str ? str : "(null)"));
+            bombout(("Couldn't agree a key exchange algorithm"
+                     " (available: %.*s)", len, str));
            crStopV;
        }
        /*
@@ -6235,6 +6363,10 @@ static void do_ssh2_transport(Ssh ssh, void *vin, int inlen,
         */
        s->guessok = first_in_commasep_string(preferred, str, len);
        ssh_pkt_getstring(pktin, &str, &len);    /* host key algorithms */
+        if (!str) {
+            bombout(("KEXINIT packet was incomplete"));
+            crStopV;
+        }
        for (i = 0; i < lenof(hostkey_algs); i++) {
            if (in_commasep_string(hostkey_algs[i]->name, str, len)) {
                ssh->hostkey = hostkey_algs[i];
@@ -6242,14 +6374,18 @@ static void do_ssh2_transport(Ssh ssh, void *vin, int inlen,
            }
        }
        if (!ssh->hostkey) {
-           bombout(("Couldn't agree a host key algorithm (available: %s)",
-                    str ? str : "(null)"));
+            bombout(("Couldn't agree a host key algorithm"
+                     " (available: %.*s)", len, str));
            crStopV;
        }
 
        s->guessok = s->guessok &&
            first_in_commasep_string(hostkey_algs[0]->name, str, len);
        ssh_pkt_getstring(pktin, &str, &len);    /* client->server cipher */
+        if (!str) {
+            bombout(("KEXINIT packet was incomplete"));
+            crStopV;
+        }
        for (i = 0; i < s->n_preferred_ciphers; i++) {
            const struct ssh2_ciphers *c = s->preferred_ciphers[i];
            if (!c) {
@@ -6266,12 +6402,16 @@ static void do_ssh2_transport(Ssh ssh, void *vin, int inlen,
                break;
        }
        if (!s->cscipher_tobe) {
-           bombout(("Couldn't agree a client-to-server cipher (available: %s)",
-                    str ? str : "(null)"));
+            bombout(("Couldn't agree a client-to-server cipher"
+                     " (available: %.*s)", len, str));
            crStopV;
        }
 
        ssh_pkt_getstring(pktin, &str, &len);    /* server->client cipher */
+        if (!str) {
+            bombout(("KEXINIT packet was incomplete"));
+            crStopV;
+        }
        for (i = 0; i < s->n_preferred_ciphers; i++) {
            const struct ssh2_ciphers *c = s->preferred_ciphers[i];
            if (!c) {
@@ -6288,12 +6428,16 @@ static void do_ssh2_transport(Ssh ssh, void *vin, int inlen,
                break;
        }
        if (!s->sccipher_tobe) {
-           bombout(("Couldn't agree a server-to-client cipher (available: %s)",
-                    str ? str : "(null)"));
+            bombout(("Couldn't agree a server-to-client cipher"
+                     " (available: %.*s)", len, str));
            crStopV;
        }
 
        ssh_pkt_getstring(pktin, &str, &len);    /* client->server mac */
+        if (!str) {
+            bombout(("KEXINIT packet was incomplete"));
+            crStopV;
+        }
        for (i = 0; i < s->nmacs; i++) {
            if (in_commasep_string(s->maclist[i]->name, str, len)) {
                s->csmac_tobe = s->maclist[i];
@@ -6301,6 +6445,10 @@ static void do_ssh2_transport(Ssh ssh, void *vin, int inlen,
            }
        }
        ssh_pkt_getstring(pktin, &str, &len);    /* server->client mac */
+        if (!str) {
+            bombout(("KEXINIT packet was incomplete"));
+            crStopV;
+        }
        for (i = 0; i < s->nmacs; i++) {
            if (in_commasep_string(s->maclist[i]->name, str, len)) {
                s->scmac_tobe = s->maclist[i];
@@ -6308,6 +6456,10 @@ static void do_ssh2_transport(Ssh ssh, void *vin, int inlen,
            }
        }
        ssh_pkt_getstring(pktin, &str, &len);  /* client->server compression */
+        if (!str) {
+            bombout(("KEXINIT packet was incomplete"));
+            crStopV;
+        }
        for (i = 0; i < lenof(compressions) + 1; i++) {
            const struct ssh_compress *c =
                i == 0 ? s->preferred_comp : compressions[i - 1];
@@ -6324,6 +6476,10 @@ static void do_ssh2_transport(Ssh ssh, void *vin, int inlen,
            }
        }
        ssh_pkt_getstring(pktin, &str, &len);  /* server->client compression */
+        if (!str) {
+            bombout(("KEXINIT packet was incomplete"));
+            crStopV;
+        }
        for (i = 0; i < lenof(compressions) + 1; i++) {
            const struct ssh_compress *c =
                i == 0 ? s->preferred_comp : compressions[i - 1];
@@ -6465,8 +6621,19 @@ static void do_ssh2_transport(Ssh ssh, void *vin, int inlen,
              * much data.
              */
             s->pbits = 512 << ((s->nbits - 1) / 64);
-            s->pktout = ssh2_pkt_init(SSH2_MSG_KEX_DH_GEX_REQUEST);
-            ssh2_pkt_adduint32(s->pktout, s->pbits);
+            if (s->pbits < DH_MIN_SIZE)
+                s->pbits = DH_MIN_SIZE;
+            if (s->pbits > DH_MAX_SIZE)
+                s->pbits = DH_MAX_SIZE;
+            if ((ssh->remote_bugs & BUG_SSH2_OLDGEX)) {
+                s->pktout = ssh2_pkt_init(SSH2_MSG_KEX_DH_GEX_REQUEST_OLD);
+                ssh2_pkt_adduint32(s->pktout, s->pbits);
+            } else {
+                s->pktout = ssh2_pkt_init(SSH2_MSG_KEX_DH_GEX_REQUEST);
+                ssh2_pkt_adduint32(s->pktout, DH_MIN_SIZE);
+                ssh2_pkt_adduint32(s->pktout, s->pbits);
+                ssh2_pkt_adduint32(s->pktout, DH_MAX_SIZE);
+            }
             ssh2_pkt_send_noqueue(ssh, s->pktout);
 
             crWaitUntilV(pktin);
@@ -6511,6 +6678,10 @@ static void do_ssh2_transport(Ssh ssh, void *vin, int inlen,
         }
         set_busy_status(ssh->frontend, BUSY_CPU); /* cogitate */
         ssh_pkt_getstring(pktin, &s->hostkeydata, &s->hostkeylen);
+        if (!s->hostkeydata) {
+            bombout(("unable to parse key exchange reply packet"));
+            crStopV;
+        }
         s->hkey = ssh->hostkey->newkey(s->hostkeydata, s->hostkeylen);
         s->f = ssh2_pkt_getmp(pktin);
         if (!s->f) {
@@ -6518,7 +6689,18 @@ static void do_ssh2_transport(Ssh ssh, void *vin, int inlen,
             crStopV;
         }
         ssh_pkt_getstring(pktin, &s->sigdata, &s->siglen);
+        if (!s->sigdata) {
+            bombout(("unable to parse key exchange reply packet"));
+            crStopV;
+        }
 
+        {
+            const char *err = dh_validate_f(ssh->kex_ctx, s->f);
+            if (err) {
+                bombout(("key exchange reply failed validation: %s", err));
+                crStopV;
+            }
+        }
         s->K = dh_find_K(ssh->kex_ctx, s->f);
 
         /* We assume everything from now on will be quick, and it might
@@ -6527,7 +6709,11 @@ static void do_ssh2_transport(Ssh ssh, void *vin, int inlen,
 
         hash_string(ssh->kex->hash, ssh->exhash, s->hostkeydata, s->hostkeylen);
         if (!ssh->kex->pdata) {
+            if (!(ssh->remote_bugs & BUG_SSH2_OLDGEX))
+                hash_uint32(ssh->kex->hash, ssh->exhash, DH_MIN_SIZE);
             hash_uint32(ssh->kex->hash, ssh->exhash, s->pbits);
+            if (!(ssh->remote_bugs & BUG_SSH2_OLDGEX))
+                hash_uint32(ssh->kex->hash, ssh->exhash, DH_MAX_SIZE);
             hash_mpint(ssh->kex->hash, ssh->exhash, s->p);
             hash_mpint(ssh->kex->hash, ssh->exhash, s->g);
         }
@@ -6555,6 +6741,10 @@ static void do_ssh2_transport(Ssh ssh, void *vin, int inlen,
         }
 
         ssh_pkt_getstring(pktin, &s->hostkeydata, &s->hostkeylen);
+        if (!s->hostkeydata) {
+            bombout(("unable to parse RSA public key packet"));
+            crStopV;
+        }
         hash_string(ssh->kex->hash, ssh->exhash,
                    s->hostkeydata, s->hostkeylen);
        s->hkey = ssh->hostkey->newkey(s->hostkeydata, s->hostkeylen);
@@ -6562,6 +6752,10 @@ static void do_ssh2_transport(Ssh ssh, void *vin, int inlen,
         {
             char *keydata;
             ssh_pkt_getstring(pktin, &keydata, &s->rsakeylen);
+            if (!keydata) {
+                bombout(("unable to parse RSA public key packet"));
+                crStopV;
+            }
             s->rsakeydata = snewn(s->rsakeylen, char);
             memcpy(s->rsakeydata, keydata, s->rsakeylen);
         }
@@ -6638,6 +6832,10 @@ static void do_ssh2_transport(Ssh ssh, void *vin, int inlen,
         }
 
         ssh_pkt_getstring(pktin, &s->sigdata, &s->siglen);
+        if (!s->sigdata) {
+            bombout(("unable to parse signature packet"));
+            crStopV;
+        }
 
         sfree(s->rsakeydata);
     }
@@ -6668,31 +6866,39 @@ static void do_ssh2_transport(Ssh ssh, void *vin, int inlen,
          * checked the signature of the exchange hash.)
          */
         s->fingerprint = ssh->hostkey->fingerprint(s->hkey);
-        ssh_set_frozen(ssh, 1);
-        s->dlgret = verify_ssh_host_key(ssh->frontend,
-                                        ssh->savedhost, ssh->savedport,
-                                        ssh->hostkey->keytype, s->keystr,
-                                        s->fingerprint,
-                                        ssh_dialog_callback, ssh);
-        if (s->dlgret < 0) {
-            do {
-                crReturnV;
-                if (pktin) {
-                    bombout(("Unexpected data from server while waiting"
-                             " for user host key response"));
-                    crStopV;
-                }
-            } while (pktin || inlen > 0);
-            s->dlgret = ssh->user_response;
-        }
-        ssh_set_frozen(ssh, 0);
-        if (s->dlgret == 0) {
-            ssh_disconnect(ssh, "User aborted at host key verification", NULL,
-                           0, TRUE);
-            crStopV;
-        }
         logevent("Host key fingerprint is:");
         logevent(s->fingerprint);
+        /* First check against manually configured host keys. */
+        s->dlgret = verify_ssh_manual_host_key(ssh, s->fingerprint,
+                                               ssh->hostkey, s->hkey);
+        if (s->dlgret == 0) {          /* did not match */
+            bombout(("Host key did not appear in manually configured list"));
+            crStopV;
+        } else if (s->dlgret < 0) { /* none configured; use standard handling */
+            ssh_set_frozen(ssh, 1);
+            s->dlgret = verify_ssh_host_key(ssh->frontend,
+                                            ssh->savedhost, ssh->savedport,
+                                            ssh->hostkey->keytype, s->keystr,
+                                            s->fingerprint,
+                                            ssh_dialog_callback, ssh);
+            if (s->dlgret < 0) {
+                do {
+                    crReturnV;
+                    if (pktin) {
+                        bombout(("Unexpected data from server while waiting"
+                                 " for user host key response"));
+                        crStopV;
+                    }
+                } while (pktin || inlen > 0);
+                s->dlgret = ssh->user_response;
+            }
+            ssh_set_frozen(ssh, 0);
+            if (s->dlgret == 0) {
+                ssh_disconnect(ssh, "Aborted at host key verification", NULL,
+                               0, TRUE);
+                crStopV;
+            }
+        }
         sfree(s->fingerprint);
         /*
          * Save this host key, to check against the one presented in
@@ -7112,10 +7318,11 @@ static void ssh2_queue_chanreq_handler(struct ssh_channel *c,
  * request-specific data added and be sent.  Note that if a handler is
  * provided, it's essential that the request actually be sent.
  *
- * The handler will usually be passed the response packet in pktin.
- * If pktin is NULL, this means that no reply will ever be forthcoming
- * (e.g. because the entire connection is being destroyed) and the
- * handler should free any storage it's holding.
+ * The handler will usually be passed the response packet in pktin. If
+ * pktin is NULL, this means that no reply will ever be forthcoming
+ * (e.g. because the entire connection is being destroyed, or because
+ * the server initiated channel closure before we saw the response)
+ * and the handler should free any storage it's holding.
  */
 static struct Packet *ssh2_chanreq_init(struct ssh_channel *c, char *type,
                                        cchandler_fn_t handler, void *ctx)
@@ -7416,7 +7623,7 @@ static void ssh_check_termination(Ssh ssh)
 {
     if (ssh->version == 2 &&
         !conf_get_int(ssh->conf, CONF_ssh_no_shell) &&
-        count234(ssh->channels) == 0 &&
+        (ssh->channels && count234(ssh->channels) == 0) &&
         !(ssh->connshare && share_ndownstreams(ssh->connshare) > 0)) {
         /*
          * We used to send SSH_MSG_DISCONNECT here, because I'd
@@ -7431,9 +7638,14 @@ static void ssh_check_termination(Ssh ssh)
     }
 }
 
-void ssh_sharing_downstream_connected(Ssh ssh, unsigned id)
+void ssh_sharing_downstream_connected(Ssh ssh, unsigned id,
+                                      const char *peerinfo)
 {
-    logeventf(ssh, "Connection sharing downstream #%u connected", id);
+    if (peerinfo)
+        logeventf(ssh, "Connection sharing downstream #%u connected from %s",
+                  id, peerinfo);
+    else
+        logeventf(ssh, "Connection sharing downstream #%u connected", id);
 }
 
 void ssh_sharing_downstream_disconnected(Ssh ssh, unsigned id)
@@ -7605,6 +7817,21 @@ static void ssh2_msg_channel_close(Ssh ssh, struct Packet *pktin)
      */
     ssh2_channel_got_eof(c);
 
+    if (!(ssh->remote_bugs & BUG_SENDS_LATE_REQUEST_REPLY)) {
+        /*
+         * It also means we stop expecting to see replies to any
+         * outstanding channel requests, so clean those up too.
+         * (ssh_chanreq_init will enforce by assertion that we don't
+         * subsequently put anything back on this list.)
+         */
+        while (c->v.v2.chanreq_head) {
+            struct outstanding_channel_request *ocr = c->v.v2.chanreq_head;
+            ocr->handler(c, NULL, ocr->ctx);
+            c->v.v2.chanreq_head = ocr->next;
+            sfree(ocr);
+        }
+    }
+
     /*
      * And we also send an outgoing EOF, if we haven't already, on the
      * assumption that CLOSE is a pretty forceful announcement that
@@ -7780,6 +8007,16 @@ static void ssh2_msg_channel_request(Ssh ssh, struct Packet *pktin)
     ssh_pkt_getstring(pktin, &type, &typelen);
     want_reply = ssh2_pkt_getbool(pktin);
 
+    if (c->closes & CLOSES_SENT_CLOSE) {
+        /*
+         * We don't reply to channel requests after we've sent
+         * CHANNEL_CLOSE for the channel, because our reply might
+         * cross in the network with the other side's CHANNEL_CLOSE
+         * and arrive after they have wound the channel up completely.
+         */
+        want_reply = FALSE;
+    }
+
     /*
      * Having got the channel number, we now look at
      * the request type string to see if it's something
@@ -8409,7 +8646,8 @@ static void ssh2_msg_authconn(Ssh ssh, struct Packet *pktin)
 static void ssh2_response_authconn(struct ssh_channel *c, struct Packet *pktin,
                                   void *ctx)
 {
-    do_ssh2_authconn(c->ssh, NULL, 0, pktin);
+    if (pktin)
+        do_ssh2_authconn(c->ssh, NULL, 0, pktin);
 }
 
 static void do_ssh2_authconn(Ssh ssh, unsigned char *in, int inlen,
@@ -8920,11 +9158,20 @@ static void do_ssh2_authconn(Ssh ssh, unsigned char *in, int inlen,
                s->can_keyb_inter = conf_get_int(ssh->conf, CONF_try_ki_auth) &&
                    in_commasep_string("keyboard-interactive", methods, methlen);
 #ifndef NO_GSSAPI
-               if (!ssh->gsslibs)
-                   ssh->gsslibs = ssh_gss_setup(ssh->conf);
-               s->can_gssapi = conf_get_int(ssh->conf, CONF_try_gssapi_auth) &&
-                   in_commasep_string("gssapi-with-mic", methods, methlen) &&
-                   ssh->gsslibs->nlibraries > 0;
+                if (conf_get_int(ssh->conf, CONF_try_gssapi_auth) &&
+                   in_commasep_string("gssapi-with-mic", methods, methlen)) {
+                    /* Try loading the GSS libraries and see if we
+                     * have any. */
+                    if (!ssh->gsslibs)
+                        ssh->gsslibs = ssh_gss_setup(ssh->conf);
+                    s->can_gssapi = (ssh->gsslibs->nlibraries > 0);
+                } else {
+                    /* No point in even bothering to try to load the
+                     * GSS libraries, if the user configuration and
+                     * server aren't both prepared to attempt GSSAPI
+                     * auth in the first place. */
+                    s->can_gssapi = FALSE;
+                }
 #endif
            }
 
@@ -9255,6 +9502,8 @@ static void do_ssh2_authconn(Ssh ssh, unsigned char *in, int inlen,
                     logevent("Sent public key signature");
                    s->type = AUTH_TYPE_PUBLICKEY;
                    key->alg->freekey(key->data);
+                    sfree(key->comment);
+                    sfree(key);
                }
 
 #ifndef NO_GSSAPI
@@ -10115,7 +10364,8 @@ static void do_ssh2_authconn(Ssh ssh, unsigned char *in, int inlen,
             * Try to send data on all channels if we can.
             */
            for (i = 0; NULL != (c = index234(ssh->channels, i)); i++)
-               ssh2_try_send_and_unthrottle(ssh, c);
+                if (c->type != CHAN_SHARING)
+                    ssh2_try_send_and_unthrottle(ssh, c);
        }
     }
 
@@ -10437,6 +10687,8 @@ static const char *ssh_init(void *frontend_handle, void **backend_handle,
     ssh->sent_console_eof = FALSE;
     ssh->got_pty = FALSE;
     ssh->bare_connection = FALSE;
+    ssh->X11_fwd_enabled = FALSE;
+    ssh->connshare = NULL;
     ssh->attempting_connshare = FALSE;
 
     *backend_handle = ssh;
@@ -10477,11 +10729,13 @@ static const char *ssh_init(void *frontend_handle, void **backend_handle,
     ssh->gsslibs = NULL;
 #endif
 
+    random_ref(); /* do this now - may be needed by sharing setup code */
+
     p = connect_to_host(ssh, host, port, realhost, nodelay, keepalive);
-    if (p != NULL)
+    if (p != NULL) {
+        random_unref();
        return p;
-
-    random_ref();
+    }
 
     return NULL;
 }
@@ -11024,7 +11278,11 @@ void ssh_send_port_open(void *channel, char *hostname, int port, char *org)
                    PKT_END);
     } else {
        pktout = ssh2_chanopen_init(c, "direct-tcpip");
-       ssh2_pkt_addstring(pktout, hostname);
+        {
+            char *trimmed_host = host_strduptrim(hostname);
+            ssh2_pkt_addstring(pktout, trimmed_host);
+            sfree(trimmed_host);
+        }
        ssh2_pkt_adduint32(pktout, port);
        /*
         * We make up values for the originator data; partly it's
@@ -11085,13 +11343,19 @@ static int ssh_return_exitcode(void *handle)
 }
 
 /*
- * cfg_info for SSH is the currently running version of the
- * protocol. (1 for 1; 2 for 2; 0 for not-decided-yet.)
+ * cfg_info for SSH is the protocol running in this session.
+ * (1 or 2 for the full SSH-1 or SSH-2 protocol; -1 for the bare
+ * SSH-2 connection protocol, i.e. a downstream; 0 for not-decided-yet.)
  */
 static int ssh_cfg_info(void *handle)
 {
     Ssh ssh = (Ssh) handle;
-    return ssh->version;
+    if (ssh->version == 0)
+       return 0; /* don't know yet */
+    else if (ssh->bare_connection)
+       return -1;
+    else
+       return ssh->version;
 }
 
 /*