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Category: Application (Generic) > GNOME Display Manager

Vendors: Gnome Development Team

(Red Hat Issues Fix) GNOME Display Manager (gdm) Lets Local Users View Files With Root Privileges

SecurityTracker Alert ID: 1007551

CVE Reference: CAN-2003-0547 (Links to External Site)

Updated: Dec 1 2003

Original Entry Date: Aug 21 2003

Impact: Denial of service via network, Disclosure of system information, Disclosure of user information

Fix Available: Yes Vendor Confirmed: Yes

Version(s): prior to 2.4.1.6

Description: Several vulnerabilities were reported in the GNOME Display Manager (gdm). A local user can view arbitrary files on the system. A remote user may be able to cause the gdm daemon may crash.

It is reported that a local user can make a symbolic link (symlink) from an arbitrary file on the system to the '~/.xsession-errors' file. Then, when gdm runs and is configured with the "examine session errors" option, the local user can view the symlinked file (CVE: CAN-2003-0547). Any file can be read with root privileges, according to the report.

It is also reported that there are two vulnerabilties in the X Display Manager Control Protocol (XDMCP) implementation. A remote user can cause the gdm daemon to crash. If a host expires, the gdm daemon may crash (CVE: CAN-2003-0548). If an authorization key name is shorter then 18 bytes, the gdm daemon may crash (CVE: CAN-2003-0549).

Impact: A local user can view arbitrary files with root privileges.

A remote user may be able to cause the daemon to crash.

Vendor URL: www.5z.com/jirka/gdm.html (Links to External Site)

Cause: Access control error, Exception handling error

Underlying OS: Linux (Red Hat)

Underlying OS Comments: 7.1, 7.2, 7.3, 8.0, 9

Reported By: bugzilla@redhat.com

Message History: This archive entry is a follow-up to the message listed below.

Aug 21 2003

GNOME Display Manager (gdm) Lets Local Users View Files With Root Privileges

Source Message Contents

Date: Thu, 21 Aug 2003 15:18 -0400
From: bugzilla@redhat.com
Subject: [RHSA-2003:258-01] GDM allows local user to read any file.

 

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

- ---------------------------------------------------------------------
                   Red Hat Security Advisory

Synopsis:          GDM allows local user to read any file.
Advisory ID:       RHSA-2003:258-01
Issue date:        2003-08-21
Updated on:        2003-08-21
Product:           Red Hat Linux
Keywords:          DoS
Cross references:  
Obsoletes:         
CVE Names:         CAN-2003-0547 CAN-2003-0548 CAN-2003-0549
- ---------------------------------------------------------------------

1. Topic:

Updated GDM packages are available which correct a bug allowing local users
to read any text files on the system, and a denial of service issue if
XDMCP is enabled.

2. Relevant releases/architectures:

Red Hat Linux 7.1 - i386
Red Hat Linux 7.1 for iSeries (64 bit) - ppc
Red Hat Linux 7.1 for pSeries (64 bit) - ppc
Red Hat Linux 7.2 - i386, ia64
Red Hat Linux 7.3 - i386
Red Hat Linux 8.0 - i386
Red Hat Linux 9 - i386

3. Problem description:

GDM is the GNOME Display Manager for X.

Versions of GDM prior to 2.4.1.6 contain a bug where GDM will run as root
when examining the ~/.xsession-errors file when using the "examine session
errors" feature, allowing local users the ability to read any text file
on the system by creating a symlink. The Common Vulnerabilities and
Exposures project (cve.mitre.org) has assigned the name CAN-2003-0547 to
this issue.

Red Hat Linux 8.0 and 9 are vulnerable to this issue. Versions of GDM in
earlier releases did not have the "examine session errors" feature and
therefore are not vulnerable to this issue. 

Also addressed by these erratum packages are two problems in the X Display
Manager Control Protocol (XDMCP) which allow a denial of service attack
(DoS) by crashing the gdm daemon. The Common Vulnerabilities and
Exposures project (cve.mitre.org) has assigned the names CAN-2003-0548 and
CAN-2003-0549 to these issues.

This attack is only possible if XDMCP is enabled. XDMCP is not enabled by
default in Red Hat Linux distributions, and as documented XDMCP should only
ever be run on trusted networks.

Users of GDM are advised to upgrade to these erratum packages which disable
the "examine session errors" feature and contain backported security fixes
for the XDMCP issues.

4. Solution:

Before applying this update, make sure all previously released errata
relevant to your system have been applied.

To update all RPMs for your particular architecture, run:

rpm -Fvh [filenames]

where [filenames] is a list of the RPMs you wish to upgrade.  Only those
RPMs which are currently installed will be updated.  Those RPMs which are
not installed but included in the list will not be updated.  Note that you
can also use wildcards (*.rpm) if your current directory *only* contains the
desired RPMs.

Please note that this update is also available via Red Hat Network.  Many
people find this an easier way to apply updates.  To use Red Hat Network,
launch the Red Hat Update Agent with the following command:

up2date

This will start an interactive process that will result in the appropriate
RPMs being upgraded on your system.

5. RPMs required:

Red Hat Linux 7.1:

SRPMS:
ftp://updates.redhat.com/7.1/en/os/SRPMS/gdm-2.0beta2-46.src.rpm

i386:
ftp://updates.redhat.com/7.1/en/os/i386/gdm-2.0beta2-46.i386.rpm

Red Hat Linux 7.1 for iSeries (64 bit):

SRPMS:
ftp://updates.redhat.com/7.1/en/os/iSeries/SRPMS/gdm-2.0beta2-46.src.rpm

ppc:
ftp://updates.redhat.com/7.1/en/os/iSeries/ppc/gdm-2.0beta2-46.ppc.rpm

Red Hat Linux 7.1 for pSeries (64 bit):

SRPMS:
ftp://updates.redhat.com/7.1/en/os/pSeries/SRPMS/gdm-2.0beta2-46.src.rpm

ppc:
ftp://updates.redhat.com/7.1/en/os/pSeries/ppc/gdm-2.0beta2-46.ppc.rpm

Red Hat Linux 7.2:

SRPMS:
ftp://updates.redhat.com/7.2/en/os/SRPMS/gdm-2.2.3.1-21.src.rpm

i386:
ftp://updates.redhat.com/7.2/en/os/i386/gdm-2.2.3.1-21.i386.rpm

ia64:
ftp://updates.redhat.com/7.2/en/os/ia64/gdm-2.2.3.1-21.ia64.rpm

Red Hat Linux 7.3:

SRPMS:
ftp://updates.redhat.com/7.3/en/os/SRPMS/gdm-2.2.3.1-23.src.rpm

i386:
ftp://updates.redhat.com/7.3/en/os/i386/gdm-2.2.3.1-23.i386.rpm

Red Hat Linux 8.0:

SRPMS:
ftp://updates.redhat.com/8.0/en/os/SRPMS/gdm-2.4.0.7-14.src.rpm

i386:
ftp://updates.redhat.com/8.0/en/os/i386/gdm-2.4.0.7-14.i386.rpm

Red Hat Linux 9:

SRPMS:
ftp://updates.redhat.com/9/en/os/SRPMS/gdm-2.4.1.3-5.1.src.rpm

i386:
ftp://updates.redhat.com/9/en/os/i386/gdm-2.4.1.3-5.1.i386.rpm



6. Verification:

MD5 sum                          Package Name
- --------------------------------------------------------------------------
9704d602c1d7101b95ca80f09d115cf4 7.1/en/os/SRPMS/gdm-2.0beta2-46.src.rpm
1badaf70349be1f21e4b4a990835a247 7.1/en/os/i386/gdm-2.0beta2-46.i386.rpm
9704d602c1d7101b95ca80f09d115cf4 7.1/en/os/iSeries/SRPMS/gdm-2.0beta2-46.src.rpm
c4d56f8b41f1a006c575dd7c5fdbad03 7.1/en/os/iSeries/ppc/gdm-2.0beta2-46.ppc.rpm
9704d602c1d7101b95ca80f09d115cf4 7.1/en/os/pSeries/SRPMS/gdm-2.0beta2-46.src.rpm
c4d56f8b41f1a006c575dd7c5fdbad03 7.1/en/os/pSeries/ppc/gdm-2.0beta2-46.ppc.rpm
380aa52d404a7e1a5ad64e94ced8a938 7.2/en/os/SRPMS/gdm-2.2.3.1-21.src.rpm
abeb24df46ba93d175819a9222f86071 7.2/en/os/i386/gdm-2.2.3.1-21.i386.rpm
987175704054c3852c3275d4ce8155c2 7.2/en/os/ia64/gdm-2.2.3.1-21.ia64.rpm
9c6defce518879748d5e335e5ff54d4f 7.3/en/os/SRPMS/gdm-2.2.3.1-23.src.rpm
a8b30c05951f1d88f0f374b84772be16 7.3/en/os/i386/gdm-2.2.3.1-23.i386.rpm
3085c2df6e5215d23f2f0458cccaa578 8.0/en/os/SRPMS/gdm-2.4.0.7-14.src.rpm
22311861baaec59b7c32b3258f6f40b1 8.0/en/os/i386/gdm-2.4.0.7-14.i386.rpm
8df8308fc16b3a2c8fbaf1fd99142274 9/en/os/SRPMS/gdm-2.4.1.3-5.1.src.rpm
64eea2519454422dba6f451573e0c3e3 9/en/os/i386/gdm-2.4.1.3-5.1.i386.rpm


These packages are GPG signed by Red Hat for security.  Our key is
available from http://www.redhat.com/security/keys.html

You can verify each package with the following command:
    
    rpm --checksig -v <filename>

If you only wish to verify that each package has not been corrupted or
tampered with, examine only the md5sum with the following command:
    
    md5sum <filename>


7. References:

http://www.tldp.org/HOWTO/XDMCP-HOWTO/procedure.html#SECURITY
http://cve.mitre.org/cgi-bin/cvename.cgi?name=CAN-2003-0547
http://cve.mitre.org/cgi-bin/cvename.cgi?name=CAN-2003-0548
http://cve.mitre.org/cgi-bin/cvename.cgi?name=CAN-2003-0549

8. Contact:

The Red Hat security contact is <secalert@redhat.com>.  More contact
details at http://www.redhat.com/solutions/security/news/contact.html

Copyright 2003 Red Hat, Inc.
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