QNX crttrap Possible Race Condition Vulnerability

Submitted by newsagent on

RDFS Labs identifies a possible race condition with the way crttrap spawns io-graphics. This was reported to QSS with apparently no response, therefor the information was released on the web.*** rfdslabs security advisory ***

Title: QNX crrtrap possible race condition vulnerability [RLSA_04-2004]
Versions: QNX RTP 6.1 (possibly others)
Vendor: http://www.qnx.com
Date: Sep 13 2004

Author: Julio Cesar Fort

1. Introduction

crrtrap is a tool to detect video hardware and starts the correct driver for QNX.

2. Details

crttrap does a sequence of commands before calls 'io-graphics', an external program part of Photon. Because of this, there is a theorical race condition vulnerability.

(1) /bin/cd /usr/photon/bin
(2) io-graphics [arguments]

This spot (*) is where the race condition lies. If we are able to modify $PATH in the exact moment before crrtrap calls step 2, we could obtain local root priviledges because it will execute 'io-graphics' (our code) looking for it in /tmp directory.
If an attacker writes a code to neverend loop changing everytime $PATH and runs it into background, there is a theorical possiblility to modify environment and trick crttrap.

3. Solution

QNX Software Systems was contacted in september 8th but vendor didn't reply. It seems they don't care much about security (they don't even have a security staff e-mail, but SALES e-mail adddress is everywhere at qnx.com!).

4. Timeline

26 Aug 2004: Vulnerability detected;
08 Sep 2004: rfdslabs contacts QNX: no success;

Thanks to DataStorm Technologies and some stranger in mobius.qnx.com who was intersted in rfdslabs.com.br.