QNX Neutrino RTOS libAp ABLPATH Buffer Overflow Vulnerability

iDefense Security Advisory 02.07.06
http://www.idefense.com/intelligence/vulnerabilities/display.php?id=381
February 7, 2006

I. BACKGROUND

QNX Software Systems Ltd.'s Neutrino RTOS (QNX) is a real-time operating
system designed for use in embedded systems. More information is
available at:

http://www.qnx.com/products/rtos/

II. DESCRIPTION

Local exploitation of a stack-based buffer overflow vulnerability in
QNX Inc.'s Neutrino RTOS Operating System allows local attackers to
gain root privileges.

The vulnerability specifically exists due to improper handling of
environment variables in the libAP system library. The libAP system
library is utilized by various setuid applications, including all
applications that are PhAB-generated. The _ApFindTranslationFile()
function fails to check bounds on the ABLPATH environment variable
prior to a strcat operation. An attacker can supply an overly long
value for ABLPATH to overflow the stack buffer and overwrite the return
address as shown here:

Program received signal SIGSEGV, Segmentation fault.
0xb8242bf7 in ApMultiStrcat () from
/usr/qnx630/target/qnx6/x86/usr/lib/libAp.so.2
(gdb) x/i $pc
0xb8242bf7 <ApMultiStrcat+15>: mov (%eax),%dl
(gdb) bt
#0 0xb8242bf7 in ApMultiStrcat () from
/usr/qnx630/target/qnx6/x86/usr/lib/libAp.so.2
#1 0xb823ce07 in _ApFindTranslationFile () from
/usr/qnx630/target/qnx6/x86/usr/lib/libAp.so.2
#2 0x42424242 in ?? ()

Attackers can supply a specially crafted value to overflow the buffer
and execute arbitrary code.

III. ANALYSIS

Successful exploitation of the vulnerability allows local attackers to
gain root privileges. The libAP library is a core system library on
Neutrino RTOS, however it has had a number of trivial vulnerabilities
similar to this one. A related vulnerability is the ABLANG environment
variable overflow which results in a similarly exploitable scenario.

IV. DETECTION

iDefense has confirmed the existence of this vulnerability on QNX
Neutrino RTOS 6.3.0. All versions are suspected vulnerable.

V. WORKAROUND

As a workaround solution, remove the setuid bit from any programs
linked to libAP.so.2. An example is shown here:

ls -l /usr/photon/bin/phlocale

-rwsrwxr-x 1 root root 54244 May 05 2004 /usr/photon/bin/phlocale

ldd /usr/photon/bin/phlocale

/usr/photon/bin/phlocale:
libAp.so.3 => /usr/lib/libAp.so.3 (0xb8200000)
libph.so.3 => /usr/lib/libph.so.3 (0xb8210000)
libphrender.so.2 => /usr/lib/libphrender.so.2 (0xb8312000)
libm.so.2 => /lib/libm.so.2 (0xb8347000)
libfont.so.1 => /lib/libfont.so.1 (0xb8363000)
libc.so.2 => /usr/lib/ldqnx.so.2 (0xb0300000)

chmod -s /usr/photon/bin/phlocale

VI. VENDOR RESPONSE

The vendor has not responded to communication regarding this issue.

VII. CVE INFORMATION

A Mitre Corp. Common Vulnerabilities and Exposures (CVE) number has not
been assigned yet.

VIII. DISCLOSURE TIMELINE

12/15/2005 Initial vendor notification
02/07/2006 Public disclosure

IX. CREDIT

iDefense credits Filipe Balestra ([email protected]) with the
discovery of this vulnerability.

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X. LEGAL NOTICES

Copyright © 2006 iDefense, Inc.

Permission is granted for the redistribution of this alert
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Disclaimer: The information in the advisory is believed to be accurate
at the time of publishing based on currently available information. Use
of the information constitutes acceptance for use in an AS IS condition.
There are no warranties with regard to this information. Neither the
author nor the publisher accepts any liability for any direct, indirect,
or consequential loss or damage arising from use of, or reliance on,
this information.

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