From 9395b28223334826837c15e8c1bb4dfb3b0d2ca5 Mon Sep 17 00:00:00 2001 From: Damien Miller Date: Sun, 20 Apr 2014 13:25:30 +1000 Subject: [PATCH] - djm@cvs.openbsd.org 2014/04/18 23:52:25 [compat.c compat.h sshconnect2.c sshd.c version.h] 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@ --- ChangeLog | 10 ++++++++++ compat.c | 18 ++++++++++++++++-- compat.h | 4 +++- sshconnect2.c | 4 +++- sshd.c | 5 ++++- version.h | 4 ++-- 6 files changed, 38 insertions(+), 7 deletions(-) diff --git a/ChangeLog b/ChangeLog index 3e8592118..5b53c216c 100644 --- a/ChangeLog +++ b/ChangeLog @@ -98,6 +98,16 @@ remove the identity files from this manpage - ssh-agent doesn't deal with them at all and the same information is duplicated in ssh-add.1 (which does deal with them); prodded by deraadt@ + - djm@cvs.openbsd.org 2014/04/18 23:52:25 + [compat.c compat.h sshconnect2.c sshd.c version.h] + 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@ 20140401 - (djm) On platforms that support it, use prctl() to prevent sftp-server diff --git a/compat.c b/compat.c index 9d9fabef3..64f9790a8 100644 --- a/compat.c +++ b/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. * @@ -95,6 +95,8 @@ 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| @@ -251,7 +253,6 @@ compat_cipher_proposal(char *cipher_prop) return cipher_prop; } - char * compat_pkalg_proposal(char *pkalg_prop) { @@ -265,3 +266,16 @@ 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/compat.h b/compat.h index b174fa171..2e25d5ba9 100644 --- a/compat.h +++ b/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/sshconnect2.c b/sshconnect2.c index f123194b0..b1aa69c24 100644 --- a/sshconnect2.c +++ b/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. @@ -196,6 +196,8 @@ 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/sshd.c b/sshd.c index f0fc07896..3ca722c5c 100644 --- a/sshd.c +++ b/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 @@ -2438,6 +2438,9 @@ 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/version.h b/version.h index a1579ace1..cc8a079a9 100644 --- a/version.h +++ b/version.h @@ -1,6 +1,6 @@ -/* $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" #define SSH_PORTABLE "p1" #define SSH_RELEASE SSH_VERSION SSH_PORTABLE