QNX Neutrino RTOS libph PHOTON_PATH Buffer Overflow Vulnerability

iDefense Security Advisory 02.07.06
http://www.idefense.com/intelligence/vulnerabilities/display.php?id=382
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 libph system library. The libph system
library is utilized by various setuid applications that utilize the
Photon API. The setitem() function fails to check bounds on the
PHOTON_PATH environment variable prior to a strcpy operation. An
attacker can supply an overly long value for PHOTON_PATH to overflow the
stack buffer and overwrite the return address as shown here:

Breakpoint 1, 0xb0343624 in strcpy ()
  from /usr/qnx630/target/qnx6/x86/lib/libc.so.2
(gdb) bt
#0 0xb0343624 in strcpy () from /usr/qnx630/target/qnx6/x86/lib/libc.so.2
#1 0xb826f58b in setitem ()
  from /usr/qnx630/target/qnx6/x86/usr/lib/libph.so.3
#2 0xb826f7ec in additems ()
  from /usr/qnx630/target/qnx6/x86/usr/lib/libph.so.3
#3 0xb826ffa9 in list_modify ()
  from /usr/qnx630/target/qnx6/x86/usr/lib/libph.so.3
#4 0xb82ef2fe in PtSetValue ()
  from /usr/qnx630/target/qnx6/x86/usr/lib/libph.so.3
#5 0xb82c7ceb in PtCompoundSetResources ()
  from /usr/qnx630/target/qnx6/x86/usr/lib/libph.so.3
#6 0xb82ed018 in PtSetResources ()
  from /usr/qnx630/target/qnx6/x86/usr/lib/libph.so.3
#7 0xb8244bf3 in set_list_res ()
  from /usr/qnx630/target/qnx6/x86/usr/lib/libph.so.3
#8 0xb82ef2fe in PtSetValue ()
  from /usr/qnx630/target/qnx6/x86/usr/lib/libph.so.3
#9 0xb82c7ceb in PtCompoundSetResources ()
  from /usr/qnx630/target/qnx6/x86/usr/lib/libph.so.3
#10 0xb82ed018 in PtSetResources ()
  from /usr/qnx630/target/qnx6/x86/usr/lib/libph.so.3
#11 0x0804db32 in main ()
#12 0x44444444 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 libph library is a core system library on
Neutrino RTOS, however it has had a number of trivial vulnerabilities
similar to this one.

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 libph.so.3. 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 (filipe@balestra.com.br) with the
discovery of this vulnerability.

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X. LEGAL NOTICES

Copyright © 2006 iDefense, Inc.

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