2 files changed, 31 insertions, 6 deletions

diff --git a/ChangeLog b/ChangeLog
index 48d49dea1..84833fb3c 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,10 @@
+20140227
+ - OpenBSD CVS Sync
+   - djm@cvs.openbsd.org 2014/02/26 20:18:37
+     [ssh.c]
+     bz#2205: avoid early hostname lookups unless canonicalisation is enabled;
+     ok dtucker@ markus@
+
 20140224
  - OpenBSD CVS Sync
    - djm@cvs.openbsd.org 2014/02/07 06:55:54
diff --git a/ssh.c b/ssh.c
index b7dbea2b6..1e6cb9000 100644
--- a/ssh.c
+++ b/ssh.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: ssh.c,v 1.400 2014/02/23 20:11:36 djm Exp $ */
+/* $OpenBSD: ssh.c,v 1.401 2014/02/26 20:18:37 djm Exp $ */
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@@ -899,12 +899,20 @@ main(int ac, char **av)
                 addrs = resolve_canonicalize(&host, options.port);
 
         /*
-         * If canonicalization not requested, or if it failed then try to
-         * resolve the bare hostname name using the system resolver's usual
-         * search rules. Skip the lookup if a ProxyCommand is being used
-         * unless the user has specifically requested canonicalisation.
+         * If CanonicalizePermittedCNAMEs have been specified but
+         * other canonicalization did not happen (by not being requested
+         * or by failing with fallback) then the hostname may still be changed
+         * as a result of CNAME following. 
+         *
+         * Try to resolve the bare hostname name using the system resolver's
+         * usual search rules and then apply the CNAME follow rules.
+         *
+         * Skip the lookup if a ProxyCommand is being used unless the user
+         * has specifically requested canonicalisation for this case via
+         * CanonicalizeHostname=always
          */
-        if (addrs == NULL && (option_clear_or_none(options.proxy_command) ||
+        if (addrs == NULL && options.num_permitted_cnames != 0 &&
+            (option_clear_or_none(options.proxy_command) ||
             options.canonicalize_hostname == SSH_CANONICALISE_ALWAYS)) {
                 if ((addrs = resolve_host(host, options.port, 1,
                     cname, sizeof(cname))) == NULL)
@@ -1000,6 +1008,16 @@ main(int ac, char **av)
         if (options.control_path != NULL)
                 muxclient(options.control_path);
 
+        /*
+         * If hostname canonicalisation was not enabled, then we may not
+         * have yet resolved the hostname. Do so now.
+         */
+        if (addrs == NULL && options.proxy_command == NULL) {
+                if ((addrs = resolve_host(host, options.port, 1,
+                    cname, sizeof(cname))) == NULL)
+                        cleanup_exit(255); /* resolve_host logs the error */
+        }
+
         timeout_ms = options.connection_timeout * 1000;
 
         /* Open a connection to the remote host. */