From 552c8d8e8793a2da4281fb5f2a2a070a82ba8b77 Mon Sep 17 00:00:00 2001 From: Damien Miller Date: Fri, 18 Apr 2014 23:52:26 +0000 Subject: OpenSSH 6.5 and 6.6 have a bug that causes ~0.2% of connections using the curve25519-sha256@libssh.org KEX exchange method to fail when connecting with something that implements the spec properly. Disable this KEX method when speaking to one of the affected versions. reported by Aris Adamantiadis; ok markus@ --- usr.bin/ssh/compat.c | 18 ++++++++++++++++-- usr.bin/ssh/compat.h | 4 +++- usr.bin/ssh/sshconnect2.c | 4 +++- usr.bin/ssh/sshd.c | 5 ++++- usr.bin/ssh/version.h | 4 ++-- 5 files changed, 28 insertions(+), 7 deletions(-) (limited to 'usr.bin') diff --git a/usr.bin/ssh/compat.c b/usr.bin/ssh/compat.c index 52ce971e541..5f9e363eeec 100644 --- a/usr.bin/ssh/compat.c +++ b/usr.bin/ssh/compat.c @@ -1,4 +1,4 @@ -/* $OpenBSD: compat.c,v 1.82 2013/12/30 23:52:27 djm Exp $ */ +/* $OpenBSD: compat.c,v 1.83 2014/04/18 23:52:25 djm Exp $ */ /* * Copyright (c) 1999, 2000, 2001, 2002 Markus Friedl. All rights reserved. * @@ -93,6 +93,8 @@ compat_datafellows(const char *version) { "Sun_SSH_1.0*", SSH_BUG_NOREKEY|SSH_BUG_EXTEOF}, { "OpenSSH_4*", 0 }, { "OpenSSH_5*", SSH_NEW_OPENSSH|SSH_BUG_DYNAMIC_RPORT}, + { "OpenSSH_6.5*," + "OpenSSH_6.6", SSH_NEW_OPENSSH|SSH_BUG_CURVE25519PAD}, { "OpenSSH*", SSH_NEW_OPENSSH }, { "*MindTerm*", 0 }, { "2.1.0*", SSH_BUG_SIGBLOB|SSH_BUG_HMAC| @@ -249,7 +251,6 @@ compat_cipher_proposal(char *cipher_prop) return cipher_prop; } - char * compat_pkalg_proposal(char *pkalg_prop) { @@ -263,3 +264,16 @@ compat_pkalg_proposal(char *pkalg_prop) return pkalg_prop; } +char * +compat_kex_proposal(char *kex_prop) +{ + if (!(datafellows & SSH_BUG_CURVE25519PAD)) + return kex_prop; + debug2("%s: original KEX proposal: %s", __func__, kex_prop); + kex_prop = filter_proposal(kex_prop, "curve25519-sha256@libssh.org"); + debug2("%s: compat KEX proposal: %s", __func__, kex_prop); + if (*kex_prop == '\0') + fatal("No supported key exchange algorithms found"); + return kex_prop; +} + diff --git a/usr.bin/ssh/compat.h b/usr.bin/ssh/compat.h index b174fa1719c..2e25d5ba991 100644 --- a/usr.bin/ssh/compat.h +++ b/usr.bin/ssh/compat.h @@ -1,4 +1,4 @@ -/* $OpenBSD: compat.h,v 1.44 2013/12/30 23:52:27 djm Exp $ */ +/* $OpenBSD: compat.h,v 1.45 2014/04/18 23:52:25 djm Exp $ */ /* * Copyright (c) 1999, 2000, 2001 Markus Friedl. All rights reserved. @@ -59,6 +59,7 @@ #define SSH_BUG_RFWD_ADDR 0x02000000 #define SSH_NEW_OPENSSH 0x04000000 #define SSH_BUG_DYNAMIC_RPORT 0x08000000 +#define SSH_BUG_CURVE25519PAD 0x10000000 void enable_compat13(void); void enable_compat20(void); @@ -66,6 +67,7 @@ void compat_datafellows(const char *); int proto_spec(const char *); char *compat_cipher_proposal(char *); char *compat_pkalg_proposal(char *); +char *compat_kex_proposal(char *); extern int compat13; extern int compat20; diff --git a/usr.bin/ssh/sshconnect2.c b/usr.bin/ssh/sshconnect2.c index 4848cd48af8..8e7e7ca75b7 100644 --- a/usr.bin/ssh/sshconnect2.c +++ b/usr.bin/ssh/sshconnect2.c @@ -1,4 +1,4 @@ -/* $OpenBSD: sshconnect2.c,v 1.205 2014/03/27 23:01:27 markus Exp $ */ +/* $OpenBSD: sshconnect2.c,v 1.206 2014/04/18 23:52:25 djm Exp $ */ /* * Copyright (c) 2000 Markus Friedl. All rights reserved. * Copyright (c) 2008 Damien Miller. All rights reserved. @@ -190,6 +190,8 @@ ssh_kex2(char *host, struct sockaddr *hostaddr, u_short port) } if (options.kex_algorithms != NULL) myproposal[PROPOSAL_KEX_ALGS] = options.kex_algorithms; + myproposal[PROPOSAL_KEX_ALGS] = compat_kex_proposal( + myproposal[PROPOSAL_KEX_ALGS]); if (options.rekey_limit || options.rekey_interval) packet_set_rekey_limits((u_int32_t)options.rekey_limit, diff --git a/usr.bin/ssh/sshd.c b/usr.bin/ssh/sshd.c index e15dedd421a..cf013ee5af7 100644 --- a/usr.bin/ssh/sshd.c +++ b/usr.bin/ssh/sshd.c @@ -1,4 +1,4 @@ -/* $OpenBSD: sshd.c,v 1.423 2014/04/12 04:55:53 djm Exp $ */ +/* $OpenBSD: sshd.c,v 1.424 2014/04/18 23:52:25 djm Exp $ */ /* * Author: Tatu Ylonen * Copyright (c) 1995 Tatu Ylonen , Espoo, Finland @@ -2292,6 +2292,9 @@ do_ssh2_kex(void) if (options.kex_algorithms != NULL) myproposal[PROPOSAL_KEX_ALGS] = options.kex_algorithms; + myproposal[PROPOSAL_KEX_ALGS] = compat_kex_proposal( + myproposal[PROPOSAL_KEX_ALGS]); + if (options.rekey_limit || options.rekey_interval) packet_set_rekey_limits((u_int32_t)options.rekey_limit, (time_t)options.rekey_interval); diff --git a/usr.bin/ssh/version.h b/usr.bin/ssh/version.h index 5fb6a69cf24..fa2e4b07bd3 100644 --- a/usr.bin/ssh/version.h +++ b/usr.bin/ssh/version.h @@ -1,3 +1,3 @@ -/* $OpenBSD: version.h,v 1.70 2014/02/27 22:57:40 djm Exp $ */ +/* $OpenBSD: version.h,v 1.71 2014/04/18 23:52:25 djm Exp $ */ -#define SSH_VERSION "OpenSSH_6.6" +#define SSH_VERSION "OpenSSH_6.7" -- cgit v1.2.3