Bug#211324: ssh: Further potential security bugs
Package: ssh
Version: 1:3.4p1-1.1
Severity: grave
Tags: security
Justification: user security hole
Further to bug 211205 which was resolved by DSA-382-1:
http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=211205
the OpenBSD project have released OpenSSH 3.7.1 which contains further
updates for similar issues to the one fixed by OpenSSH 3.7. While they
do not know if these bugs are exploitable (which they also said about
the 3.7 buffer.c update) it may be worth investigating the additional
updates in 3.7.1 and seeing if any of them are applicable to the
versions in Debian, and if so reissuing the security update. (The diff
between 3.7 and 3.7.1 is short and only seems to contain the potential
security fixes.)
The grave/user security rating on the bug is because of the concern
that some of these additional issues found may be security issues.
I enclose the OpenBSD advisory:
-=- cut here -=-
From: Markus Friedl <markus@openbsd.org>
To: security-announce@openbsd.org
Subject: OpenSSH Security Advisory: buffer.adv
Date: Wed, 17 Sep 2003 01:13:29 +0200
Message-ID: <20030916231329.GA25160@folly>
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;
}
===================================================================
-=- cut here -=-
Ewen
-- System Information
Debian Release: 3.0
Architecture: i386
Kernel: Linux basilica 2.4.21-xfs-lvm107-ll-acpi-skas-bluezmh2-nomodv #1 Mon Sep 8 18:19:23 NZST 2003 i686
Locale: LANG=C, LC_CTYPE=C
Versions of packages ssh depends on:
ii adduser 3.47 Add and remove users and groups
ii debconf 1.2.35woody1 Debian configuration management sy
ii libc6 2.2.5-11.5 GNU C Library: Shared libraries an
ii libpam-modules 0.72-35 Pluggable Authentication Modules f
ii libpam0g 0.72-35 Pluggable Authentication Modules l
ii libssl0.9.6 0.9.6c-2.woody.3 SSL shared libraries
ii libwrap0 7.6-9 Wietse Venema's TCP wrappers libra
ii zlib1g 1:1.1.4-1 compression library - runtime
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