nanog mailing list archives
Re: Heads up -- potential problems in 3.7, too? [Fwd: OpenSSH Security Advisory: buffer.adv]
From: up () 3 am
Date: Tue, 16 Sep 2003 20:58:13 -0400 (EDT)
I hope you mean OpenSSH 3.7p1 ? On Tue, 16 Sep 2003, Alex Lambert wrote:
3.7.1 was just released. Two patches for similar issues in a very short timeframe. Who do they think they are -- Microsoft? <grin> apl -------- Original Message -------- Subject: OpenSSH Security Advisory: buffer.adv Date: Wed, 17 Sep 2003 01:13:30 +0200 From: Markus Friedl <markus () openbsd org> To: misc () openbsd org This is the 2nd revision of the Advisory. This document can be found at: http://www.openssh.com/txt/buffer.adv 1. Versions affected: All versions of OpenSSH's sshd prior to 3.7.1 contain buffer management errors. It is uncertain whether these errors are potentially exploitable, however, we prefer to see bugs fixed proactively. Other implementations sharing common origin may also have these issues. 2. Solution: Upgrade to OpenSSH 3.7.1 or apply the following patch. =================================================================== Appendix A: patch for OpenSSH 3.6.1 and earlier Index: buffer.c =================================================================== RCS file: /cvs/src/usr.bin/ssh/buffer.c,v retrieving revision 1.16 retrieving revision 1.18 diff -u -r1.16 -r1.18 --- buffer.c 26 Jun 2002 08:54:18 -0000 1.16 +++ buffer.c 16 Sep 2003 21:02:39 -0000 1.18 @@ -23,8 +23,11 @@ void buffer_init(Buffer *buffer) { - buffer->alloc = 4096; - buffer->buf = xmalloc(buffer->alloc); + const u_int len = 4096; + + buffer->alloc = 0; + buffer->buf = xmalloc(len); + buffer->alloc = len; buffer->offset = 0; buffer->end = 0; } @@ -34,8 +37,10 @@ void buffer_free(Buffer *buffer) { - memset(buffer->buf, 0, buffer->alloc); - xfree(buffer->buf); + if (buffer->alloc > 0) { + memset(buffer->buf, 0, buffer->alloc); + xfree(buffer->buf); + } } /* @@ -69,6 +74,7 @@ void * buffer_append_space(Buffer *buffer, u_int len) { + u_int newlen; void *p; if (len > 0x100000) @@ -98,11 +104,13 @@ goto restart; } /* Increase the size of the buffer and retry. */ - buffer->alloc += len + 32768; - if (buffer->alloc > 0xa00000) + + newlen = buffer->alloc + len + 32768; + if (newlen > 0xa00000) fatal("buffer_append_space: alloc %u not supported", - buffer->alloc); - buffer->buf = xrealloc(buffer->buf, buffer->alloc); + newlen); + buffer->buf = xrealloc(buffer->buf, newlen); + buffer->alloc = newlen; goto restart; /* NOTREACHED */ } Index: channels.c =================================================================== RCS file: /cvs/src/usr.bin/ssh/channels.c,v retrieving revision 1.194 retrieving revision 1.195 diff -u -r1.194 -r1.195 --- channels.c 29 Aug 2003 10:04:36 -0000 1.194 +++ channels.c 16 Sep 2003 21:02:40 -0000 1.195 @@ -228,12 +228,13 @@ if (found == -1) { /* There are no free slots. Take last+1 slot and expand the array. */ found = channels_alloc; - channels_alloc += 10; if (channels_alloc > 10000) fatal("channel_new: internal error: channels_alloc %d " "too big.", channels_alloc); + channels = xrealloc(channels, + (channels_alloc + 10) * sizeof(Channel *)); + channels_alloc += 10; debug2("channel: expanding %d", channels_alloc); - channels = xrealloc(channels, channels_alloc * sizeof(Channel *)); for (i = found; i < channels_alloc; i++) channels[i] = NULL; } =================================================================== Appendix B: patch for OpenSSH 3.7 Index: buffer.c =================================================================== RCS file: /cvs/src/usr.bin/ssh/buffer.c,v retrieving revision 1.17 retrieving revision 1.18 diff -u -r1.17 -r1.18 --- buffer.c 16 Sep 2003 03:03:47 -0000 1.17 +++ buffer.c 16 Sep 2003 21:02:39 -0000 1.18 @@ -23,8 +23,11 @@ void buffer_init(Buffer *buffer) { - buffer->alloc = 4096; - buffer->buf = xmalloc(buffer->alloc); + const u_int len = 4096; + + buffer->alloc = 0; + buffer->buf = xmalloc(len); + buffer->alloc = len; buffer->offset = 0; buffer->end = 0; } @@ -34,8 +37,10 @@ void buffer_free(Buffer *buffer) { - memset(buffer->buf, 0, buffer->alloc); - xfree(buffer->buf); + if (buffer->alloc > 0) { + memset(buffer->buf, 0, buffer->alloc); + xfree(buffer->buf); + } } /* Index: channels.c =================================================================== RCS file: /cvs/src/usr.bin/ssh/channels.c,v retrieving revision 1.194 retrieving revision 1.195 diff -u -r1.194 -r1.195 --- channels.c 29 Aug 2003 10:04:36 -0000 1.194 +++ channels.c 16 Sep 2003 21:02:40 -0000 1.195 @@ -228,12 +228,13 @@ if (found == -1) { /* There are no free slots. Take last+1 slot and expand the array. */ found = channels_alloc; - channels_alloc += 10; if (channels_alloc > 10000) fatal("channel_new: internal error: channels_alloc %d " "too big.", channels_alloc); + channels = xrealloc(channels, + (channels_alloc + 10) * sizeof(Channel *)); + channels_alloc += 10; debug2("channel: expanding %d", channels_alloc); - channels = xrealloc(channels, channels_alloc * sizeof(Channel *)); for (i = found; i < channels_alloc; i++) channels[i] = NULL; } ===================================================================
James Smallacombe PlantageNet, Inc. CEO and Janitor up () 3 am http://3.am =========================================================================
Current thread:
- Heads up -- potential problems in 3.7, too? [Fwd: OpenSSH Security Advisory: buffer.adv] Alex Lambert (Sep 16)
- Re: Heads up -- potential problems in 3.7, too? [Fwd: OpenSSH Security Advisory: buffer.adv] up (Sep 16)
- Re: Heads up -- potential problems in 3.7, too? [Fwd: OpenSSH Security Advisory: buffer.adv] E.B. Dreger (Sep 16)