Handle packets with no type byte by returning SSH_MSG_UNIMPLEMENTED.

[PuTTY.git] / ssh.c

diff --git a/ssh.c b/ssh.c
index a37b04416ac50c0f15f73d3cc9230167e6cb2588..1077209ae8e1fee800c0c0258db04da3b2742934 100644 (file)
--- a/ssh.c
+++ b/ssh.c
@@ -360,6 +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
@@ -1742,6 +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.
@@ -6672,6 +6682,7 @@ static void do_ssh2_transport(Ssh ssh, void *vin, int inlen,
             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) {
             bombout(("unable to parse key exchange reply packet"));
@@ -7612,7 +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
@@ -9147,11 +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
            }