* New upstream release (closes: #536182). Yes, I know 5.3p1 has been out

  for a while, but there's no GSSAPI patch available for it yet.
  - Change the default cipher order to prefer the AES CTR modes and the
    revised "arcfour256" mode to CBC mode ciphers that are susceptible to
    CPNI-957037 "Plaintext Recovery Attack Against SSH".
  - Add countermeasures to mitigate CPNI-957037-style attacks against the
    SSH protocol's use of CBC-mode ciphers. Upon detection of an invalid
    packet length or Message Authentication Code, ssh/sshd will continue
    reading up to the maximum supported packet length rather than
    immediately terminating the connection. This eliminates most of the
    known differences in behaviour that leaked information about the
    plaintext of injected data which formed the basis of this attack
    (closes: #506115, LP: #379329).
  - ForceCommand directive now accepts commandline arguments for the
    internal-sftp server (closes: #524423, LP: #362511).
  - Add AllowAgentForwarding to available Match keywords list (closes:
    #540623).
  - Make ssh(1) send the correct channel number for
    SSH2_MSG_CHANNEL_SUCCESS and SSH2_MSG_CHANNEL_FAILURE messages to
    avoid triggering 'Non-public channel' error messages on sshd(8) in
    openssh-5.1.
  - Avoid printing 'Non-public channel' warnings in sshd(8), since the
    ssh(1) has sent incorrect channel numbers since ~2004 (this reverts a
    behaviour introduced in openssh-5.1; closes: #496017).
* Update to GSSAPI patch from
  http://www.sxw.org.uk/computing/patches/openssh-5.2p1-gsskex-all-20090726.patch,
  including cascading credentials support (LP: #416958).

1 files changed, 15 insertions, 12 deletions

diff --git a/kexgexs.c b/kexgexs.c
index a037f57f2..76a0f8ca7 100644
--- a/kexgexs.c
+++ b/kexgexs.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: kexgexs.c,v 1.10 2006/11/06 21:25:28 markus Exp $ */
+/* $OpenBSD: kexgexs.c,v 1.11 2009/01/01 21:17:36 djm Exp $ */
 /*
  * Copyright (c) 2000 Niels Provos.  All rights reserved.
  * Copyright (c) 2001 Markus Friedl.  All rights reserved.
@@ -56,7 +56,8 @@ kexgex_server(Kex *kex)
         DH *dh;
         u_char *kbuf, *hash, *signature = NULL, *server_host_key_blob = NULL;
         u_int sbloblen, klen, slen, hashlen;
-        int min = -1, max = -1, nbits = -1, type, kout;
+        int omin = -1, min = -1, omax = -1, max = -1, onbits = -1, nbits = -1;
+        int type, kout;
 
         if (kex->load_host_key == NULL)
                 fatal("Cannot load hostkey");
@@ -68,27 +69,29 @@ kexgex_server(Kex *kex)
         switch (type) {
         case SSH2_MSG_KEX_DH_GEX_REQUEST:
                 debug("SSH2_MSG_KEX_DH_GEX_REQUEST received");
-                min = packet_get_int();
-                nbits = packet_get_int();
-                max = packet_get_int();
+                omin = min = packet_get_int();
+                onbits = nbits = packet_get_int();
+                omax = max = packet_get_int();
                 min = MAX(DH_GRP_MIN, min);
                 max = MIN(DH_GRP_MAX, max);
+                nbits = MAX(DH_GRP_MIN, nbits);
+                nbits = MIN(DH_GRP_MAX, nbits);
                 break;
         case SSH2_MSG_KEX_DH_GEX_REQUEST_OLD:
                 debug("SSH2_MSG_KEX_DH_GEX_REQUEST_OLD received");
-                nbits = packet_get_int();
-                min = DH_GRP_MIN;
-                max = DH_GRP_MAX;
+                onbits = nbits = packet_get_int();
                 /* unused for old GEX */
+                omin = min = DH_GRP_MIN;
+                omax = max = DH_GRP_MAX;
                 break;
         default:
                 fatal("protocol error during kex, no DH_GEX_REQUEST: %d", type);
         }
         packet_check_eom();
 
-        if (max < min || nbits < min || max < nbits)
+        if (omax < omin || onbits < omin || omax < onbits)
                 fatal("DH_GEX_REQUEST, bad parameters: %d !< %d !< %d",
-                    min, nbits, max);
+                    omin, onbits, omax);
 
         /* Contact privileged parent */
         dh = PRIVSEP(choose_dh(min, nbits, max));
@@ -149,7 +152,7 @@ kexgex_server(Kex *kex)
         key_to_blob(server_host_key, &server_host_key_blob, &sbloblen);
 
         if (type == SSH2_MSG_KEX_DH_GEX_REQUEST_OLD)
-                min = max = -1;
+                omin = min = omax = max = -1;
 
         /* calc H */
         kexgex_hash(
@@ -159,7 +162,7 @@ kexgex_server(Kex *kex)
             buffer_ptr(&kex->peer), buffer_len(&kex->peer),
             buffer_ptr(&kex->my), buffer_len(&kex->my),
             server_host_key_blob, sbloblen,
-            min, nbits, max,
+            omin, onbits, omax,
             dh->p, dh->g,
             dh_client_pub,
             dh->pub_key,