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 :
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
This issue has been corrected in QNX Momentics 6.3.0 SP3 and later
versions. Patches are also available for 6.3.0 (Patch ID:230), 6.3.0
SP1 (Patch ID:231), and 6.3.0 SP2 (Patch ID:232). Please contact your
QNX representative, or visit http://www.qnx.com/account/login.html to
obtain these patches.
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 (filipe@balestra.com.br) 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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edited in any way without the express
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part of this alert in any other medium other than electronically, please
email customerservice@idefense.com for permission.
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.
