ban clients/servers that suffer from SSH_BUG_DERIVEKEY, they are ancient,

deranged and might make some attacks on KEX easier; ok markus@

diff --git a/usr.bin/ssh/sshconnect.c b/usr.bin/ssh/sshconnect.c
index 28ea1d0..f8ecb78 100644 (file)
--- a/usr.bin/ssh/sshconnect.c
+++ b/usr.bin/ssh/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
@@ -652,6 +652,9 @@ 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/usr.bin/ssh/sshd.c b/usr.bin/ssh/sshd.c
index b4fd347..658e79e 100644 (file)
--- a/usr.bin/ssh/sshd.c
+++ b/usr.bin/ssh/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
@@ -481,9 +481,14 @@ 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) {