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Date: Thu, 14 Jun 2012 23:52:02 +0100
From: Simon McVittie <smcv@...ian.org>
To: oss-security@...ts.openwall.com
Subject: CVE-2012-3345: symlink attack in ioquake3 >= r1773, < r2253

This was meant to be released tomorrow (and that's what I told vendors),
but the patch was accidentally committed and announced upstream a day
early, so I'm sending the advisory out straight away.

Background
==========

ioquake3 [IOQ] is a fork of the Quake III Arena (id Tech 3) game engine,
and has become the de facto upstream for that engine since id Software
ceased to develop it. It is also used (unmodified, modified or forked)
in various open-source and proprietary games including OpenArena [OA],
Reaction [REA], Smokin' Guns [SGN], Tremulous [TREM], Turtle Arena [TA],
Urban Terror [URT] and World of Padman [WOP].

Vulnerability
=============

Access vector: local
Authentication required: local system
Impact: victim overwrites file of attacker's choice with a predictable
integer

Since svn revision 1773, ioquake3 has written its process ID to the file
/tmp/ioq3.pid (or ioq3.pid in a world-writeable location) under the
following circumstances:

* running on non-Mac Unix and TMPDIR not set, or set to a
  world-writeable location; or
* running on Mac OS and FSFindFolder() for a temporary directory fails
  or returns a world-writeable location

On a multi-user system, an attacker could create a symbolic link
/tmp/ioq3.pid pointing to any file owned by a user who plays an
ioquake3-based game. When the victim runs ioquake3, the target file will
be overwritten and replaced with the process ID of ioquake3.

The effect of this attack depends on the file being overwritten: it
could be simple vandalism (destroy one of the victim's files), or it
could have further security implications if knowledge of the contents of
a target file is used for authentication (in a system similar to
pam_dotfile [DOT], for instance).

For the dedicated server, the process ID is written to ioq3_server.pid,
but the attack is essentially the same. For forks of ioquake3, the
filename will typically include the name of the fork instead, e.g.
openarena.pid.

Affected versions
=================

* ioquake3 >= svn r1773, < r2253 [ANNOUNCE]
* OpenArena 0.8.8
* Reaction beta 1.0
* Smokin' Guns 1.1
* Tremulous "trunk" >= svn r2125
* Tremulous "gpp" >= svn r2140
* Turtle Arena >= svn r204 (all releases named Turtle Arena)
* World of Padman >= 1.5.2 beta

Unaffected versions
===================

* ioquake3 1.36
* ioquake3 <= svn r1772
* OpenArena <= 0.8.5
* Smokin' Guns <= 1.1b4
* Tremulous "trunk" <= svn r2124
* Tremulous "gpp" <= svn r2139
* Tremulous GPP1
* Tremulous <= 1.1.0
* Turtle Arena <= svn r203
* TMNT Arena 20091211 (former name of Turtle Arena)
* ioUrbanTerror 2007-12-20 client
* ioUrbanTerror 2007-12-20 server
* World of Padman <= 1.5.0

Solution
========

The patches at <http://ioquake3.org/files/CVE-2012-3345/> have been
reviewed by the ioquake3 maintainers and were committed to ioquake3 svn
(as a single patch) as r2253.

Patch 0001 fixes the vulnerability by writing the pid file into the
ioquake3 user's home directory (e.g. ~/.q3a/ioq3.pid for an unmodified
engine with default configuration) instead of the temporary directory.

Patch 0002 is recommended, but not strictly necessary to fix the
vulnerability. It removes the functions to get the temporary directory,
as a precaution against other unsafe uses.

On Debian testing/unstable systems, this is fixed in ioquake3 version
1.36+svn2224-4. Debian stable is not vulnerable.

References
==========

[ANNOUNCE]
http://ioquake3.org/2012/06/14/cve-2012-3345-symlink-attack-in-ioquake3-r1773/
[IOQ] http://ioquake3.org/
[OA] http://openarena.ws/
[REA] http://www.rq3.com/
[SGN] http://www.smokin-guns.net/
[TREM] http://tremulous.net/
[TA] http://ztm.x10hosting.com/ta/
[URT] http://www.urbanterror.info/home/
[WOP] http://worldofpadman.com/website/
[DOT] http://0pointer.de/lennart/projects/pam_dotfile/

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