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Category:   OS (UNIX)  >   AIX Console Vendors:   IBM
IBM AIX Console Command Temporary Files May Let Local Users Gain Elevated Privileges
SecurityTracker Alert ID:  1009975
SecurityTracker URL:  http://securitytracker.com/id/1009975
CVE Reference:   GENERIC-MAP-NOMATCH   (Links to External Site)
Date:  Apr 28 2004
Impact:   Denial of service via local system, Modification of system information, Modification of user information, Root access via local system, User access via local system
Fix Available:  Yes  Vendor Confirmed:  Yes  
Version(s): AIX 5.1 and 5.2
Description:   A vulnerability was reported in some IBM AIX console commands. A local user may be able to gain elevated privileges.

IBM reported that they discovered that some console commands use temporary files in an unsafe manner. A local user can create a symbolic link (symlink) from a critical file on the system to one of the temporary files. Then, when the affected console command is executed by a root-level user or by a user in the system group, the symlinked file will be overwritten.

The report indicates that a local user can cause cause data destruction or denial of service conditions. [Editor's note: Although IBM does not report this, in symlink attacks it may be possible for a local user to gain root privileges.]

Impact:   A local user can cause modify or overwrite files on the system with root privileges.

[Editor's note: Although IBM does not report this, in symlink attacks it may be possible for a local user to gain root privileges.]

Solution:   IBM has issued Efixes for AIX 5.1.0 and 5.2.0, available at:

ftp://aix.software.ibm.com/aix/efixes/security/conscmd_efix.tar.Z

IBM plans to issue the following fixes:

APAR number for AIX 5.1.0: IY55790 (available approx. 06/02/04)
APAR number for AIX 5.2.0: IY55789 (available approx. 05/19/04)

Vendor URL:  www.ibm.com/ (Links to External Site)
Cause:   Access control error, State error

Message History:   None.


 Source Message Contents

Subject:  symlink vulnerabilities in console commands


-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

IBM SECURITY ADVISORY

First Issued: Thu Apr 22 15:17:51 CDT 2004

===========================================================================
                            VULNERABILITY SUMMARY

VULNERABILITY:      symlink vulnerabilities in console commands.

PLATFORMS:          AIX 5.1 and 5.2.

SOLUTION:           Apply the efixes or APARs as described below.

THREAT:             A local attacker may cause data destruction or a denial
                     of service.

CERT VU Number:     N/A
CVE Number:         N/A
===========================================================================
                            DETAILED INFORMATION


I.  Description
===============

A symlink vulnerability was discovered in some console commands that allow
an attacker to overwrite arbitrary system files. This could lead to data
destruction or a denial of service. Successful exploitation of this issue
would require the root user to execute the vulnerable commands and
unintentionally write to the source file of a symbolic link created by
the attacker. In some cases a non-root user in the system group may exploit
this vulnerability. These issues were discovered internally; at this time
there are no known exploits in the wild.

The commands affected by these issues ship as part of the bos.rte.console
and bos.rte.serv_aid filesets. To determine if these filesets are
installed, execute the following commands:

# lslpp -L bos.rte.console bos.rte.serv_aid

If the filesets are installed they will be listed along with their version
information, state, type and a description.


II. Impact
==========

A local attacker may cause data destruction or a denial of service.


III.  Solutions
===============

A. Official Fix

IBM provides the following fixes:

       APAR number for AIX 5.1.0:  IY55790 (available approx. 06/02/04)
       APAR number for AIX 5.2.0:  IY55789 (available approx. 05/19/04)


NOTE: Affected customers are urged to upgrade to 5.1.0 or 5.2.0 at
the latest maintenance level.

B. Emergency Fix

Efixes are available for AIX 5.1.0 and 5.2.0. The efixes can be
downloaded via ftp from:

      ftp://aix.software.ibm.com/aix/efixes/security/conscmd_efix.tar.Z

conscmd_efix.tar.Z is a compressed tarball containing this advisory, two
efix packages for 5.1.0 and 5.2.0 and cleartext PGP signatures for
each efix package.

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
======================================================================
IY55790.040422.epkg.Z    18401    43  840d68dcd0b7e256896d5f9f05a84e49
IY55789.040422.epkg.Z    22961    40  417bdda79f8e9291efc1cf82522eb552


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 5.1.0 and 5.2.0 are named IY55790.040422.epkg.Z and
IY55789.040422.epkg.Z respectively.

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.

The "X" flag will expand any filesystems if required.


IV. Obtaining Fixes
===================

AIX Version 5 APARs can be downloaded from the eServer pSeries Fix Central
web site:

      http://www-912.ibm.com/eserver/support/fixes/fcgui.jsp

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 0x3AE561C3.

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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