NetBSD Security Advisory 2002-004: Off-by-one error in openssh session

[NetBSD Security Officer <security-officer () netbsd org>]

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                 NetBSD Security Advisory 2002-004
                 =================================

Topic:          Off-by-one error in openssh session

Version:        NetBSD-current: source prior to March 7, 2002
                NetBSD-1.5.2:   affected
                NetBSD-1.5.1:   affected
                NetBSD-1.5:     affected
                NetBSD-1.4.*:   not included in base system
                pkgsrc:         packages prior to 3.0.2.1nb2

Severity:       local exploit (against sshd) by an authenticated user
                remote exploit (against ssh) by a malicious SSH server

Fixed:          NetBSD-current:         March 7, 2002
                NetBSD-1.5 branch:      March 7, 2002 (1.5.3 will include the fix)
                pkgsrc:                 openssh-3.0.2.1nb2 corrects this issue


Abstract
========

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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