Cap DH-GEX group size at 4kbits for Cisco implementations. Some of them

will choke when asked for preferred sizes >4k instead of returning the 4k
group that they do have.  bz#2209, ok djm@

diff --git a/usr.bin/ssh/compat.c b/usr.bin/ssh/compat.c
index 2475eaf..23dacf2 100644 (file)
--- a/usr.bin/ssh/compat.c
+++ b/usr.bin/ssh/compat.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: compat.c,v 1.93 2015/05/06 04:07:18 dtucker Exp $ */
+/* $OpenBSD: compat.c,v 1.94 2015/05/26 23:23:40 dtucker Exp $ */
 /*
  * Copyright (c) 1999, 2000, 2001, 2002 Markus Friedl.  All rights reserved.
  *
@@ -150,6 +150,7 @@ compat_datafellows(const char *version)
                  "1.2.22*",            SSH_BUG_IGNOREMSG },
                { "1.3.2*",             /* F-Secure */
                                        SSH_BUG_IGNOREMSG },
+               { "Cisco-1.*",          SSH_BUG_DHGEX_LARGE },
                { "*SSH Compatible Server*",                    /* Netscreen */
                                        SSH_BUG_PASSWORDPAD },
                { "*OSU_0*,"

diff --git a/usr.bin/ssh/compat.h b/usr.bin/ssh/compat.h
index 83507f0..2be290a 100644 (file)
--- a/usr.bin/ssh/compat.h
+++ b/usr.bin/ssh/compat.h
@@ -1,4 +1,4 @@
-/* $OpenBSD: compat.h,v 1.47 2015/04/10 05:16:50 dtucker Exp $ */
+/* $OpenBSD: compat.h,v 1.48 2015/05/26 23:23:40 dtucker Exp $ */
 
 /*
  * Copyright (c) 1999, 2000, 2001 Markus Friedl.  All rights reserved.
@@ -61,6 +61,7 @@
 #define SSH_BUG_DYNAMIC_RPORT  0x08000000
 #define SSH_BUG_CURVE25519PAD  0x10000000
 #define SSH_BUG_HOSTKEYS       0x20000000
+#define SSH_BUG_DHGEX_LARGE    0x40000000
 
 void     enable_compat13(void);
 void     enable_compat20(void);

diff --git a/usr.bin/ssh/kexgexc.c b/usr.bin/ssh/kexgexc.c
index 8c5d631..74ede3a 100644 (file)
--- a/usr.bin/ssh/kexgexc.c
+++ b/usr.bin/ssh/kexgexc.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: kexgexc.c,v 1.21 2015/04/13 02:04:08 djm Exp $ */
+/* $OpenBSD: kexgexc.c,v 1.22 2015/05/26 23:23:40 dtucker Exp $ */
 /*
  * Copyright (c) 2000 Niels Provos.  All rights reserved.
  * Copyright (c) 2001 Markus Friedl.  All rights reserved.
@@ -24,6 +24,7 @@
  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
+#include <sys/param.h>
 #include <sys/types.h>
 
 #include <openssl/dh.h>
@@ -60,6 +61,8 @@ kexgex_client(struct ssh *ssh)
        kex->min = DH_GRP_MIN;
        kex->max = DH_GRP_MAX;
        kex->nbits = nbits;
+       if (datafellows & SSH_BUG_DHGEX_LARGE)
+               kex->nbits = MIN(kex->nbits, 4096);
        /* New GEX request */
        if ((r = sshpkt_start(ssh, SSH2_MSG_KEX_DH_GEX_REQUEST)) != 0 ||
            (r = sshpkt_put_u32(ssh, kex->min)) != 0 ||