Log when we avoid using an unknown host key.

Intended as a hint that users may want to use the "Cache new host key type"
special command.

diff --git a/ssh.c b/ssh.c
index 643e5df6a316acd453339543e6a06a0b492b0a5b..ee9798af5e6d6485440afc544a8dc9c25968c416 100644 (file)
--- a/ssh.c
+++ b/ssh.c
@@ -6685,7 +6685,7 @@ static void do_ssh2_transport(Ssh ssh, const void *vin, int inlen,
                    in_commasep_string(alg->u.comp->delayed_name, str, len))
                    s->pending_compression = TRUE;  /* try this later */
            }
-           bombout(("Couldn't agree a %s ((available: %.*s)",
+           bombout(("Couldn't agree a %s (available: %.*s)",
                     kexlist_descr[i], len, str));
            crStopV;
          matched:;
@@ -7175,6 +7175,46 @@ static void do_ssh2_transport(Ssh ssh, const void *vin, int inlen,
 
     s->keystr = ssh->hostkey->fmtkey(s->hkey);
     if (!s->got_session_id) {
+       /*
+        * Make a note of any host key format we'd have preferred to use,
+        * had we already known the corresponding keys.
+        */
+       {
+           int i, j = 0;
+           char *list = NULL;
+           for (i = 0; i < lenof(hostkey_algs); i++) {
+               if (hostkey_algs[i] == ssh->hostkey)
+                   /* Not worth mentioning key types we wouldn't use */
+                   break;
+               else if (ssh->uncert_hostkeys[j] == i) {
+                   char *newlist;
+                   if (list)
+                       newlist = dupprintf("%s/%s", list,
+                                           hostkey_algs[i]->name);
+                   else
+                       newlist = dupprintf("%s", hostkey_algs[i]->name);
+                   sfree(list);
+                   list = newlist;
+                   j++;
+                   /* Assumes that hostkey_algs and uncert_hostkeys are
+                    * sorted in the same order */
+                   if (j == ssh->n_uncert_hostkeys)
+                       break;
+                   else
+                       assert(ssh->uncert_hostkeys[j] >
+                              ssh->uncert_hostkeys[j-1]);
+               }
+           }
+           if (list) {
+               logeventf(ssh,
+                         "Server has %s host key%s, but we don't know %s; "
+                         "using %s instead",
+                         list, j ? "s" : "", j ? "any of them" : "it",
+                         ssh->hostkey->name);
+               sfree(list);
+           }
+       }
+
         /*
          * Authenticate remote host: verify host key. (We've already
          * checked the signature of the exchange hash.)