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AUSCERT External Security Bulletin Redistribution
ESB-2005.0270 -- IBM Security Advisory
AIX 5.3 Remotely Exploitable Vulnerability When Configured to Use NIS
5 April 2005
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AusCERT Security Bulletin Summary
---------------------------------
Product: NIS
Publisher: IBM
Operating System: AIX 5.3
Impact: Root Compromise
Access: Remote/Unauthenticated
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IBM SECURITY ADVISORY
First Issued: Thu Mar 24 16:29:18 CST 2005
===========================================================================
VULNERABILITY SUMMARY
VULNERABILITY: A remote user may gain root access to a system
configured as a NIS client.
PLATFORMS: AIX 5.3.
SOLUTION: Apply the workaround, efix or APAR as described
below.
THREAT: A remote user may gain root access to a system
configured as a NIS client.
CERT VU Number: N/A
CVE Number: N/A
===========================================================================
DETAILED INFORMATION
I. Description
===============
A vulnerability was discovered that can be exploited by a remote user to
gain root privileges. Note that it is also possible for a local attacker to
exploit this vulnerability. This vulnerability only affects AIX 5.3 when
configured as a NIS client. Versions of AIX prior to AIX 5.3 are not
affected by this issue.
Please note that this vulnerability is a different issue than the NIS
vulnerability announced on January 31st, 2005. All fixes described in this
advisory will also address the NIS vulnerability announced on January
31st, 2005.
II. Impact
==========
A remote attacker may gain root access to a system configured as a NIS
client.
III. Solutions
===============
A. Official Fix
IBM provides the following fixes:
APAR number for AIX 5.3.0: IY68825 (available approx. 04/15/05)
NOTE: Affected customers are urged to upgrade to 5.3.0 at the latest
maintenance level.
B. Emergency Fix
Efixes are available for AIX 5.3.0. The efixes can be downloaded via ftp
from:
ftp://aix.software.ibm.com/aix/efixes/security/nis_2_efix.tar.Z
nis_2_efix.tar.Z is a compressed tarball containing this advisory, two efix
packages for 5.3.0 and a cleartext PGP signature for each efix package.
The efix package named IY68825_00.050323.epkg.Z is for AIX 5.3.0 with no
maintenance level applied. This efix has the filesets bos.rte.libc.5.3.0.5
and bos.rte.security.5.3.0.5 as prerequisites and will not install unless
these prerequisites are installed on the system. The efix package named
IY68825_01.050323.epkg.Z is for AIX 5.3.0 with maintenance level one
applied. This efix has the filesets bos.rte.libc.5.3.0.11 and
bos.rte.security.5.3.0.10 as prerequisites and will not install unless
these prerequisites are installed on the system.
Verify you have retrieved the efixes intact:
- - ---------------------------------------------
The checksums below were generated using the "sum" and "md5sum" commands
and are as follows:
Filename sum md5
======================================================================
IY68825_00.050323.epkg.Z 64933 3562 81786373cc19db9c62f51c995179e732
IY68825_01.050323.epkg.Z 54661 3627 3a9ba60ddd561b10a4f88a12b513692c
These sums should match exactly. The PGP signatures in the compressed
tarball and on this advisory can also be used to verify the integrity of
the various files they correspond to. If the sums or signatures cannot be
confirmed, double check the command results and the download site address.
If those are OK, contact IBM AIX Security at security-alert@austin.ibm.com
and describe the discrepancy.
IMPORTANT: If possible, it is recommended that a mksysb backup of the
system is created. Verify it is both bootable, and readable before
proceeding.
These efixes have not been fully regression tested; thus, IBM does not
warrant the fully correct functioning of the efix. Customers install the
efix and operate the modified version of AIX at their own risk.
Efix Installation Instructions:
- - --------------------------------
The efix package for AIX 5.3.0 with no maintenance level is named
IY68825_00.050323.epkg.Z and the efix package for AIX 5.3.0 with
maintenance level one installed is named IY68825_01.050323.epkg.Z.
These packages use the new Emergency Fix Management Solution to install
and manage efixes. More information can be found at:
http://techsupport.services.ibm.com/server/aix.efixmgmt
To preview an epkg efix installation execute the following command:
# emgr -e epkg_name -p # where epkg_name is the name of the
# efix package being previewed.
To install an epkg efix package, execute the following command:
# emgr -e epkg_name -X # where epkg_name is the name of the
# efix package being installed.
It is strongly recommended that this efix be mount installed before doing
a regular install. A mount install will mount the patched binaries over
existing system binaries. If any issues arise, the efix can be unmounted or
the system can be rebooted to revert of the original system files. The
mount an epkg efix package, execute the following command:
# emgr -e epkg_name -mX # where epkg_name is the name of the
# efix package being installed.
The "X" flag will expand any filesystems if required.
C. Workaround
This workaround is only valid if AIX is configured to use NIS. The
/etc/passwd system file contains entries for NIS users. These entries
begin with the "+" character. /etc/passwd may also contain a global escape
sequence ("+::0:0:::"). To remove this vulnerability, ensure that no entry
in /etc/passwd that begins with the "+" character specifies a gecos, home
directory or shell. These are the fifth, sixth and seventh fields
respectively. Additionally, to protect against the previous NIS
vulnerability, the global escape sequence should be changed to "+:". Note
that these change can only be done by the root user.
IV. Obtaining Fixes
===================
AIX Version 5 APARs can be downloaded from:
http://www-1.ibm.com/servers/eserver/support/pseries/aixfixes.html
Security related Emergency Fixes can be downloaded from:
ftp://aix.software.ibm.com/aix/efixes/security
V. Contact Information
========================
If you would like to receive AIX Security Advisories via email, please visit:
https://techsupport.services.ibm.com/server/pseries.subscriptionSvcs
Comments regarding the content of this announcement can be directed to:
security-alert@austin.ibm.com
To request the PGP public key that can be used to communicate securely with
the AIX Security Team send email to security-alert@austin.ibm.com with a
subject of "get key". The key can also be downloaded from a PGP Public Key
Server. The key id is 0x9391C1F2.
Please contact your local IBM AIX support center for any assistance.
eServer is a trademark of International Business Machines Corporation.
IBM, AIX and pSeries are registered trademarks of International Business
Machines Corporation. All other trademarks are property of their
respective holders.
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