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- djm@cvs.openbsd.org 2014/04/18 23:52:25

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[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@
This commit is contained in:
Damien Miller 2014-04-20 13:25:30 +10:00
parent 8c492da58f
commit 9395b28223
6 changed files with 38 additions and 7 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

10
ChangeLog
View File

@ -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

18
compat.c
View File

@ -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;
}

4
compat.h
View File

@ -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;

4
sshconnect2.c
View File

@ -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,

5
sshd.c
View File

@ -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 <ylo@cs.hut.fi>
* Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, 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);

4
version.h
View File

@ -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