Date: 02 October 2006
References: ESB-2006.0709
Click here for printable version
Click here for PGP verifiable version
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1
===========================================================================
AUSCERT External Security Bulletin Redistribution
ESB-2006.0719 -- [FreeBSD]
Multiple vulnerabilities in OpenSSH
2 October 2006
===========================================================================
AusCERT Security Bulletin Summary
---------------------------------
Product: openssh
Publisher: FreeBSD
Operating System: FreeBSD
Impact: Denial of Service
Execute Arbitrary Code/Commands
Reduced Security
Access: Remote/Unauthenticated
CVE Names: CVE-2006-5051 CVE-2006-4924
Ref: ESB-2006.0709
Original Bulletin:
ftp://ftp.freebsd.org/pub/FreeBSD/CERT/advisories/FreeBSD-SA-06:22.openssh.asc
- --------------------------BEGIN INCLUDED TEXT--------------------
- -----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1
=============================================================================
FreeBSD-SA-06:22.openssh Security Advisory
The FreeBSD Project
Topic: Multiple vulnerabilities in OpenSSH
Category: contrib
Module: openssh
Announced: 2006-09-30
Credits: Tavis Ormandy, Mark Dowd
Affects: All FreeBSD releases.
Corrected: 2006-09-30 19:50:57 UTC (RELENG_6, 6.2-PRERELEASE)
2006-09-30 19:51:56 UTC (RELENG_6_1, 6.1-RELEASE-p10)
2006-09-30 19:53:21 UTC (RELENG_6_0, 6.0-RELEASE-p15)
2006-09-30 19:54:03 UTC (RELENG_5, 5.5-STABLE)
2006-09-30 19:54:58 UTC (RELENG_5_5, 5.5-RELEASE-p8)
2006-09-30 19:55:52 UTC (RELENG_5_4, 5.4-RELEASE-p22)
2006-09-30 19:56:38 UTC (RELENG_5_3, 5.3-RELEASE-p37)
2006-09-30 19:57:15 UTC (RELENG_4, 4.11-STABLE)
2006-09-30 19:58:07 UTC (RELENG_4_11, 4.11-RELEASE-p25)
CVE Name: CVE-2006-4924, CVE-2006-5051
For general information regarding FreeBSD Security Advisories,
including descriptions of the fields above, security branches, and the
following sections, please visit <URL:http://security.FreeBSD.org/>.
I. Background
OpenSSH is an implementation of the SSH protocol suite, providing an
encrypted, authenticated transport for a variety of services,
including remote shell access.
II. Problem Description
The CRC compensation attack detector in the sshd(8) daemon, upon receipt
of duplicate blocks, uses CPU time cubic in the number of duplicate
blocks received. [CVE-2006-4924]
A race condition exists in a signal handler used by the sshd(8) daemon
to handle the LoginGraceTime option, which can potentially cause some
cleanup routines to be executed multiple times. [CVE-2006-5051]
III. Impact
An attacker sending specially crafted packets to sshd(8) can cause a
Denial of Service by using 100% of CPU time until a connection timeout
occurs. Since this attack can be performed over multiple connections
simultaneously, it is possible to cause up to MaxStartups (10 by default)
sshd processes to use all the CPU time they can obtain. [CVE-2006-4924]
The OpenSSH project believe that the race condition can lead to a Denial
of Service or potentially remote code execution, but the FreeBSD Security
Team has been unable to verify the exact impact. [CVE-2006-5051]
IV. Workaround
The attack against the CRC compensation attack detector can be avoided
by disabling SSH Protocol version 1 support in sshd_config(5).
There is no workaround for the second issue.
V. Solution
Perform one of the following:
1) Upgrade your vulnerable system to 4-STABLE, 5-STABLE, or 6-STABLE,
or to the RELENG_6_1, RELENG_6_0, RELENG_5_5, RELENG_5_4, RELENG_5_3,
or RELENG_4_11 security branch dated after the correction date.
2) To patch your present system:
The following patches have been verified to apply to FreeBSD 4.11, 5.3,
5.4, 5.5, 6.0, and 6.1 systems.
a) Download the relevant patch from the location below, and verify the
detached PGP signature using your PGP utility.
[FreeBSD 4.11]
# fetch http://security.FreeBSD.org/patches/SA-06:22/openssh4x.patch
# fetch http://security.FreeBSD.org/patches/SA-06:22/openssh4x.patch.asc
[FreeBSD 5.x]
# fetch http://security.FreeBSD.org/patches/SA-06:22/openssh5x.patch
# fetch http://security.FreeBSD.org/patches/SA-06:22/openssh5x.patch.asc
[FreeBSD 6.x]
# fetch http://security.FreeBSD.org/patches/SA-06:22/openssh6x.patch
# fetch http://security.FreeBSD.org/patches/SA-06:22/openssh6x.patch.asc
b) Execute the following commands as root:
# cd /usr/src
# patch < /path/to/patch
# cd /usr/src/secure/lib/libssh
# make obj && make depend && make && make install
# cd /usr/src/secure/usr.sbin/sshd
# make obj && make depend && make && make install
c) Restart the SSH daemon. On FreeBSD 5.x and 6.x, this can be done via
# /etc/rc.d/sshd restart
VI. Correction details
The following list contains the revision numbers of each file that was
corrected in FreeBSD.
Branch Revision
Path
- - -------------------------------------------------------------------------
RELENG_4
src/crypto/openssh/deattack.c 1.1.1.1.2.6
src/crypto/openssh/deattack.h 1.1.1.1.2.3
src/crypto/openssh/defines.h 1.1.1.2.2.3
src/crypto/openssh/log.c 1.1.1.1.2.6
src/crypto/openssh/log.h 1.1.1.1.2.4
src/crypto/openssh/packet.c 1.1.1.1.2.7
src/crypto/openssh/ssh_config 1.2.2.10
src/crypto/openssh/ssh_config.5 1.4.2.6
src/crypto/openssh/sshd.c 1.6.2.12
src/crypto/openssh/sshd_config 1.4.2.14
src/crypto/openssh/sshd_config.5 1.5.2.8
src/crypto/openssh/version.h 1.1.1.1.2.14
RELENG_4_11
src/UPDATING 1.73.2.91.2.26
src/sys/conf/newvers.sh 1.44.2.39.2.29
src/crypto/openssh/deattack.c 1.1.1.1.2.5.6.1
src/crypto/openssh/deattack.h 1.1.1.1.2.2.10.1
src/crypto/openssh/defines.h 1.1.1.2.2.2.8.1
src/crypto/openssh/log.c 1.1.1.1.2.5.8.1
src/crypto/openssh/log.h 1.1.1.1.2.3.8.1
src/crypto/openssh/packet.c 1.1.1.1.2.6.8.1
src/crypto/openssh/ssh_config 1.2.2.9.6.1
src/crypto/openssh/ssh_config.5 1.4.2.5.6.1
src/crypto/openssh/sshd.c 1.6.2.11.8.1
src/crypto/openssh/sshd_config 1.4.2.13.6.1
src/crypto/openssh/sshd_config.5 1.5.2.7.4.1
src/crypto/openssh/version.h 1.1.1.1.2.13.6.1
RELENG_5
src/crypto/openssh/auth.h 1.13.2.1
src/crypto/openssh/deattack.c 1.1.1.7.2.1
src/crypto/openssh/deattack.h 1.1.1.3.8.1
src/crypto/openssh/defines.h 1.1.1.7.2.1
src/crypto/openssh/log.c 1.1.1.10.2.1
src/crypto/openssh/log.h 1.5.2.1
src/crypto/openssh/packet.c 1.1.1.14.2.1
src/crypto/openssh/session.c 1.44.2.1
src/crypto/openssh/ssh_config 1.25.2.2
src/crypto/openssh/ssh_config.5 1.15.2.2
src/crypto/openssh/sshd.c 1.37.2.1
src/crypto/openssh/sshd_config 1.40.2.2
src/crypto/openssh/sshd_config.5 1.21.2.2
src/crypto/openssh/version.h 1.27.2.2
RELENG_5_5
src/UPDATING 1.342.2.35.2.8
src/sys/conf/newvers.sh 1.62.2.21.2.10
src/crypto/openssh/auth.h 1.13.8.1
src/crypto/openssh/deattack.c 1.1.1.7.14.1
src/crypto/openssh/deattack.h 1.1.1.3.20.1
src/crypto/openssh/defines.h 1.1.1.7.8.1
src/crypto/openssh/log.c 1.1.1.10.8.1
src/crypto/openssh/log.h 1.5.8.1
src/crypto/openssh/packet.c 1.1.1.14.8.1
src/crypto/openssh/session.c 1.44.8.1
src/crypto/openssh/ssh_config 1.25.2.1.2.1
src/crypto/openssh/ssh_config.5 1.15.2.1.2.1
src/crypto/openssh/sshd.c 1.37.8.1
src/crypto/openssh/sshd_config 1.40.2.1.2.1
src/crypto/openssh/sshd_config.5 1.21.2.1.2.1
src/crypto/openssh/version.h 1.27.2.1.2.1
RELENG_5_4
src/UPDATING 1.342.2.24.2.31
src/sys/conf/newvers.sh 1.62.2.18.2.27
src/crypto/openssh/auth.h 1.13.6.1
src/crypto/openssh/deattack.c 1.1.1.7.6.1
src/crypto/openssh/deattack.h 1.1.1.3.12.1
src/crypto/openssh/defines.h 1.1.1.7.6.1
src/crypto/openssh/log.c 1.1.1.10.6.1
src/crypto/openssh/log.h 1.5.6.1
src/crypto/openssh/packet.c 1.1.1.14.6.1
src/crypto/openssh/session.c 1.44.6.1
src/crypto/openssh/ssh_config 1.25.6.2
src/crypto/openssh/ssh_config.5 1.15.6.2
src/crypto/openssh/sshd.c 1.37.6.1
src/crypto/openssh/sshd_config 1.40.6.2
src/crypto/openssh/sshd_config.5 1.21.6.2
src/crypto/openssh/version.h 1.27.6.2
RELENG_5_3
src/UPDATING 1.342.2.13.2.40
src/sys/conf/newvers.sh 1.62.2.15.2.42
src/crypto/openssh/auth.h 1.13.4.1
src/crypto/openssh/deattack.c 1.1.1.7.4.1
src/crypto/openssh/deattack.h 1.1.1.3.10.1
src/crypto/openssh/defines.h 1.1.1.7.4.1
src/crypto/openssh/log.c 1.1.1.10.4.1
src/crypto/openssh/log.h 1.5.4.1
src/crypto/openssh/packet.c 1.1.1.14.4.1
src/crypto/openssh/session.c 1.44.4.1
src/crypto/openssh/ssh_config 1.25.4.2
src/crypto/openssh/ssh_config.5 1.15.4.2
src/crypto/openssh/sshd.c 1.37.4.1
src/crypto/openssh/sshd_config 1.40.4.2
src/crypto/openssh/sshd_config.5 1.21.4.2
src/crypto/openssh/version.h 1.27.4.2
RELENG_6
src/crypto/openssh/auth.h 1.15.2.2
src/crypto/openssh/deattack.c 1.1.1.7.8.1
src/crypto/openssh/deattack.h 1.1.1.3.14.1
src/crypto/openssh/defines.h 1.1.1.9.2.2
src/crypto/openssh/log.c 1.1.1.13.2.1
src/crypto/openssh/log.h 1.6.2.1
src/crypto/openssh/packet.c 1.1.1.16.2.2
src/crypto/openssh/session.c 1.46.2.2
src/crypto/openssh/ssh_config 1.27.2.2
src/crypto/openssh/ssh_config.5 1.17.2.2
src/crypto/openssh/sshd.c 1.39.2.2
src/crypto/openssh/sshd_config 1.42.2.2
src/crypto/openssh/sshd_config.5 1.23.2.2
src/crypto/openssh/version.h 1.30.2.2
RELENG_6_1
src/UPDATING 1.416.2.22.2.12
src/sys/conf/newvers.sh 1.69.2.11.2.12
src/crypto/openssh/auth.h 1.15.2.1.4.1
src/crypto/openssh/deattack.c 1.1.1.7.12.1
src/crypto/openssh/deattack.h 1.1.1.3.18.1
src/crypto/openssh/defines.h 1.1.1.9.2.1.4.1
src/crypto/openssh/log.c 1.1.1.13.6.1
src/crypto/openssh/log.h 1.6.6.1
src/crypto/openssh/packet.c 1.1.1.16.2.1.4.1
src/crypto/openssh/session.c 1.46.2.1.4.1
src/crypto/openssh/ssh_config 1.27.2.1.4.1
src/crypto/openssh/ssh_config.5 1.17.2.1.4.1
src/crypto/openssh/sshd.c 1.39.2.1.4.1
src/crypto/openssh/sshd_config 1.42.2.1.4.1
src/crypto/openssh/sshd_config.5 1.23.2.1.4.1
src/crypto/openssh/version.h 1.30.2.1.4.1
RELENG_6_0
src/UPDATING 1.416.2.3.2.20
src/sys/conf/newvers.sh 1.69.2.8.2.16
src/crypto/openssh/auth.h 1.15.2.1.2.1
src/crypto/openssh/deattack.c 1.1.1.7.10.1
src/crypto/openssh/deattack.h 1.1.1.3.16.1
src/crypto/openssh/defines.h 1.1.1.9.2.1.2.1
src/crypto/openssh/log.c 1.1.1.13.4.1
src/crypto/openssh/log.h 1.6.4.1
src/crypto/openssh/packet.c 1.1.1.16.2.1.2.1
src/crypto/openssh/session.c 1.46.2.1.2.1
src/crypto/openssh/ssh_config 1.27.2.1.2.1
src/crypto/openssh/ssh_config.5 1.17.2.1.2.1
src/crypto/openssh/sshd.c 1.39.2.1.2.1
src/crypto/openssh/sshd_config 1.42.2.1.2.1
src/crypto/openssh/sshd_config.5 1.23.2.1.2.1
src/crypto/openssh/version.h 1.30.2.1.2.1
- - -------------------------------------------------------------------------
VII. References
http://www.openssh.com/txt/release-4.4
http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2006-4924
http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2006-5051
The latest revision of this advisory is available at
http://security.FreeBSD.org/advisories/FreeBSD-SA-06:22.openssh.asc
- -----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.5 (FreeBSD)
iD8DBQFFHtD+FdaIBMps37IRAhw8AJ0dNrOCiYVEmqQqePByx/KUrdi+AACeNcB0
T5VfZGGXDv31Py3yxejjhlw=
=f1ch
- -----END PGP SIGNATURE-----
- --------------------------END INCLUDED TEXT--------------------
You have received this e-mail bulletin as a result of your organisation's
registration with AusCERT. The mailing list you are subscribed to is
maintained within your organisation, so if you do not wish to continue
receiving these bulletins you should contact your local IT manager. If
you do not know who that is, please send an email to auscert@auscert.org.au
and we will forward your request to the appropriate person.
NOTE: Third Party Rights
This security bulletin is provided as a service to AusCERT's members. As
AusCERT did not write the document quoted above, AusCERT has had no control
over its content. The decision to follow or act on information or advice
contained in this security bulletin is the responsibility of each user or
organisation, and should be considered in accordance with your organisation's
site policies and procedures. AusCERT takes no responsibility for consequences
which may arise from following or acting on information or advice contained in
this security bulletin.
NOTE: This is only the original release of the security bulletin. It may
not be updated when updates to the original are made. If downloading at
a later date, it is recommended that the bulletin is retrieved directly
from the author's website to ensure that the information is still current.
Contact information for the authors of the original document is included
in the Security Bulletin above. If you have any questions or need further
information, please contact them directly.
Previous advisories and external security bulletins can be retrieved from:
http://www.auscert.org.au/render.html?cid=1980
If you believe that your computer system has been compromised or attacked in
any way, we encourage you to let us know by completing the secure National IT
Incident Reporting Form at:
http://www.auscert.org.au/render.html?it=3192
===========================================================================
Australian Computer Emergency Response Team
The University of Queensland
Brisbane
Qld 4072
Internet Email: auscert@auscert.org.au
Facsimile: (07) 3365 7031
Telephone: (07) 3365 4417 (International: +61 7 3365 4417)
AusCERT personnel answer during Queensland business hours
which are GMT+10:00 (AEST).
On call after hours for member emergencies only.
===========================================================================
-----BEGIN PGP SIGNATURE-----
Comment: http://www.auscert.org.au/render.html?it=1967
iQCVAwUBRSBtJCh9+71yA2DNAQLnuwP7BTJO/gjS5B/35xgBSqfLs1h/9eA2ZCru
G0vFGW43ibkNjdvt2e84P3N7VAuhMZ7nKhOHbKI1/IkkCH3HZDet+WCJCYng6ccg
/f5KqWgesx1M7Bq9jl9h4oXAT6YsVH0x+s1JP9f/itV8vXoyPwp8x5NZmpjNU2P9
ICOzLdbWdK4=
=hfdz
-----END PGP SIGNATURE-----
|