- djm@cvs.openbsd.org 2014/01/09 23:26:48

     [sshconnect.c sshd.c]
     ban clients/servers that suffer from SSH_BUG_DERIVEKEY, they are ancient,
     deranged and might make some attacks on KEX easier; ok markus@

3 files changed, 15 insertions, 3 deletions

diff --git a/ChangeLog b/ChangeLog
index a1d37bc25..be7d868bf 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -18,6 +18,10 @@
      rather than calling OpenSSL EVP_Digest* directly. Will make it easier
      to build a reduced-feature OpenSSH without OpenSSL in future;
      feedback, ok markus@
+   - djm@cvs.openbsd.org 2014/01/09 23:26:48
+     [sshconnect.c sshd.c]
+     ban clients/servers that suffer from SSH_BUG_DERIVEKEY, they are ancient,
+     deranged and might make some attacks on KEX easier; ok markus@
 
 20140108
  - (djm) [regress/.cvsignore] Ignore regress test droppings; ok dtucker@
diff --git a/sshconnect.c b/sshconnect.c
index 791b31c12..d21781ea4 100644
--- a/sshconnect.c
+++ b/sshconnect.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: sshconnect.c,v 1.243 2013/12/30 23:52:27 djm Exp $ */
+/* $OpenBSD: sshconnect.c,v 1.244 2014/01/09 23:26:48 djm Exp $ */
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@@ -662,6 +662,9 @@ ssh_exchange_identification(int timeout_ms)
                 fatal("Protocol major versions differ: %d vs. %d",
                     (options.protocol & SSH_PROTO_2) ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1,
                     remote_major);
+        if ((datafellows & SSH_BUG_DERIVEKEY) != 0)
+                fatal("Server version \"%.100s\" uses unsafe key agreement; "
+                    "refusing connection", remote_version);
         if ((datafellows & SSH_BUG_RSASIGMD5) != 0)
                 logit("Server version \"%.100s\" uses unsafe RSA signature "
                     "scheme; disabling use of RSA keys", remote_version);
diff --git a/sshd.c b/sshd.c
index 87795bea5..60b416e30 100644
--- a/sshd.c
+++ b/sshd.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: sshd.c,v 1.413 2013/12/30 23:52:28 djm Exp $ */
+/* $OpenBSD: sshd.c,v 1.414 2014/01/09 23:26:48 djm Exp $ */
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@@ -502,9 +502,14 @@ sshd_exchange_identification(int sock_in, int sock_out)
                     get_remote_ipaddr(), client_version_string);
                 cleanup_exit(255);
         }
-        if ((datafellows & SSH_BUG_RSASIGMD5) != 0)
+        if ((datafellows & SSH_BUG_RSASIGMD5) != 0) {
                 logit("Client version \"%.100s\" uses unsafe RSA signature "
                     "scheme; disabling use of RSA keys", remote_version);
+        }
+        if ((datafellows & SSH_BUG_DERIVEKEY) != 0) {
+                fatal("Client version \"%.100s\" uses unsafe key agreement; "
+                    "refusing connection", remote_version);
+        }
 
         mismatch = 0;
         switch (remote_major) {