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             AUSCERT External Security Bulletin Redistribution

                  ESB-2006.0742 -- [UNIX/Linux][Solaris]
   Security Vulnerability in X Display Manager (xdm(1)) Xsession Script
                              31 January 2007

===========================================================================

        AusCERT Security Bulletin Summary
        ---------------------------------

Product:              xdm
Publisher:            Sun Microsystems
Operating System:     Solaris 10
                      Solaris 9
                      Solaris 8
                      UNIX variants (UNIX, Linux, OSX)
Impact:               Overwrite Arbitrary Files
                      Read-only Data Access
Access:               Existing Account
CVE Names:            CVE-2006-5215 CVE-2006-5214

Original Bulletin:
  http://sunsolve.sun.com/search/printfriendly.do?assetkey=1-26-102652-1

Comment: This advisory references vulnerabilities in products which run on
         platforms other than Solaris. It is recommended that administrators
         running xdm check for an updated version of the software from their
         vendor.

Revision History:  January 31 2007: Patches are now available
                   October 18 2006: Updated Contributing Factors and
                                    Workaround sections and added CVE Name
                   October 16 2006: Updates to Relief/Workaround section
                   October  9 2006: Initial Release

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Sun(sm) Alert Notification
     * Sun Alert ID: 102652
     * Synopsis: Security Vulnerability in X Display Manager (xdm(1))
       Xsession Script
     * Category: Security
     * Product: Solaris 9 Operating System, Solaris 10 Operating System,
       Solaris 8 Operating System
     * BugIDs: 6388471, 6423858
     * Avoidance: Patch, Workaround
     * State: Resolved
     * Date Released: 06-Oct-2006, 29-Jan-2007
     * Date Closed: 29-Jan-2007
     * Date Modified: 12-Oct-2006, 16-Oct-2006, 14-Dec-2006, 29-Jan-2007

1. Impact

   The X Display Manager (xdm(1)) manages a collection of X displays
   which may be on the local host or remote servers. A race condition in
   the Xsession script executed by xdm(1) my lead to either of the
   following issues:

   1. A local unprivileged user may be able to view the xdm(1) error log
   file, $HOME/.xsession-errors, of another user (BugID 6388471).

   This issue is also described in Xorg bug 5897:

   https://bugs.freedesktop.org/show_bug.cgi?id=5897

   2. A local unprivileged user may be able to view the alternate xdm(1)
   error log file, ${TMP-/tmp}/xses-$USER, of another user. In addition,
   when this alternate log file is in use, a local unprivileged user may
   be able to erase the contents of arbitrary files which are writable by
   another user. This alternate log file is only used if the
   $HOME/.xsession-errors file could not be created (BugID 6423858).

   This issue is also described in Xorg bug 5898:

   https://bugs.freedesktop.org/show_bug.cgi?id=5898

2. Contributing Factors

   This issue can occur in the following releases:

   SPARC Platform
     * Solaris 8 without patch 111844-04
     * Solaris 9 without patch 124830-01
     * Solaris 10 without patch 124457-01

   x86 Platform
     * Solaris 8 without patch 111845-04
     * Solaris 9 without patch 124831-01
     * Solaris 10 without patch 124458-01

3. Symptoms

   There are no predictable symptoms that would indicate the described
   issues have been exploited. 

4. Relief/Workaround

   To work around the described issues (until a patch is available),
   consider one of the two following workarounds:

   A) Use an alternate login mechanism such as dtlogin(1) or if using
   Solaris 10, gdm(1).

   or:

   B) Modify the xdm(1) configuration file, xdm-config, and create a new
   Xsession file using the following commands as the root user:
    # cd /usr/openwin/lib/X11/xdm

    # mv xdm-config xdm-config.orig

    # sed -e 's/cp \/dev\/null "$errfile"/umask 077 \&\& cp \/dev\/null "$errfi
le"/' Xsession > /etc/X11/Xsession

    # sed -e 's/\/usr\/openwin\/lib\/X11\/xdm\/Xsession/\/etc\/X11\/Xsession/'
xdm-config.orig > xdm-config

   then restore executable permissions to the file by running the
   following command:
    # chmod 755 Xsession

5. Resolution

   This issue is addressed in the following releases:

   SPARC Platform
     * Solaris 8 with patch 111844-04 or later
     * Solaris 9 with patch 124830-01 or later
     * Solaris 10 with patch 124457-01 or later

   x86 Platform
     * Solaris 8 with patch 111845-04 or later
     * Solaris 9 with patch 124831-01 or later
     * Solaris 10 with patch 124458-01 or later

Change History

   12-Oct-2006:
     * Updated Relief/Workaround section

   16-Oct-2006:
     * Updated Contributing Factors and Workaround sections

   14-Dec-2006:
     * Updated Contributing Factors and Resolution sections

   29-Jan-2007:
     * Updated Contributing Factors and Resolution sections
     * State: Resolved

   This Sun Alert notification is being provided to you on an "AS IS"
   basis. This Sun Alert notification may contain information provided by
   third parties. The issues described in this Sun Alert notification may
   or may not impact your system(s). Sun makes no representations,
   warranties, or guarantees as to the information contained herein. ANY
   AND ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING WITHOUT LIMITATION
   WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, OR
   NON-INFRINGEMENT, ARE HEREBY DISCLAIMED. BY ACCESSING THIS DOCUMENT
   YOU ACKNOWLEDGE THAT SUN SHALL IN NO EVENT BE LIABLE FOR ANY DIRECT,
   INDIRECT, INCIDENTAL, PUNITIVE, OR CONSEQUENTIAL DAMAGES THAT ARISE
   OUT OF YOUR USE OR FAILURE TO USE THE INFORMATION CONTAINED HEREIN.
   This Sun Alert notification contains Sun proprietary and confidential
   information. It is being provided to you pursuant to the provisions of
   your agreement to purchase services from Sun, or, if you do not have
   such an agreement, the Sun.com Terms of Use. This Sun Alert
   notification may only be used for the purposes contemplated by these
   agreements.

   Copyright 2000-2006 Sun Microsystems, Inc., 4150 Network Circle, Santa
   Clara, CA 95054 U.S.A. All rights reserved

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