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Home » Hacking News » NetBSD 2002-004-Off-by-one error in openssh session

NetBSD 2002-004-Off-by-one error in openssh session

by Nikola Strahija on March 13th, 2002 OpenSSH prior to version 3.1 has an off-by-one error in the channel code. This bug can be exploited locally by an authenticated user logging into a vulnerable OpenSSH server or remotely by a malicious SSH server attacking a vulnerable OpenSSH client.


Technical Details
=================

http://www.pine.nl/advisories/pine-cert-20020301.html


Solutions and Workarounds
=========================

To identify if your binary is vulnerable, you can use "ssh -V" and "sshd -V"
command.

On NetBSD-current, the following version string identifies the fixed version.
If you see version string prior to this date, the binary is vulnerable.
sshd version OpenSSH_3.1 NetBSD_Secure_Shell-20020308

On NetBSD 1.5 branch, the following string identifies the fixed version.
If you see version string prior to this date, the binary is vulnerable.
sshd version OpenSSH_3.0.2 NetBSD_Secure_Shell-20020307

With pkgsrc, use pkg_info(1) to identify the version. The following version
is not vulnerable. Versions prior to this is vulnerable.
openssh-3.0.2.1nb2

* NetBSD-current:

Systems running NetBSD-current dated from before 2002-03-06
should be upgraded to NetBSD-current dated 2002-03-07 or later.

The following directories need to be updated from the
netbsd-current CVS branch (aka HEAD):
crypto/dist/ssh
usr.bin/ssh

To update from CVS, re-build, and re-install the ssh suite:
# cd src
# cvs update -d -P crypto/dist/ssh usr.bin/ssh
# cd usr.bin/ssh

# make cleandir dependall
# make install

Be sure to restart a running instance of ssh daemon (/usr/sbin/sshd).

* NetBSD 1.5, 1.5.1, 1.5.2:

Systems running NetBSD 1.5, 1.5.1 or 1.5.2 sources dated from
before 2002-03-06 should be upgraded from NetBSD 1.5.*
sources dated 2002-03-07 or later.

NetBSD 1.5.3 will include the fix.

The following directories need to be updated from the
netbsd-1-5 CVS branch:
crypto/dist/ssh
usr.bin/ssh

To update from CVS, re-build, and re-install the ssh suite:

# cd src
# cvs update -d -P crypto/dist/ssh usr.bin/ssh
# cd usr.bin/ssh

# make cleandir dependall
# make install

Be sure to restart a running instance of ssh daemon (/usr/sbin/sshd).

Alternatively, you can install openssh newer than openssh-3.1.0.1
from pkgsrc and use them instead. Be certain to remove the old executables
in /usr/bin and /usr/sbin if you choose this method, so that the /usr/pkg/
binaries will be used.

* pkgsrc

OpenSSH pkgsrc prior to openssh-3.0.2.1nb2 must be upgraded to
openssh-3.0.2.1nb2 or later.


Thanks To
=========

Markus Friedl

Jun-ichiro itojun Hagino for patches, and preparing advisory text.


Revision History
================

2002-03-11 Initial release


More Information
================

An up-to-date PGP signed copy of this release will be maintained at
ftp://ftp.netbsd.org/pub/NetBSD/security/advisories/NetBSD-SA2002-004.txt.asc

Information about NetBSD and NetBSD security can be found at
http://www.NetBSD.ORG/ and http://www.NetBSD.ORG/Security/.


Copyright 2002, The NetBSD Foundation, Inc. All Rights Reserved.

$NetBSD: NetBSD-SA2002-004.txt,v 1.5 2002/03/12 16:49:16 david Exp $


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