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ISS Security Advisory
April 26, 2000

Insecure file handling in IBM AIX frcactrl program

Synopsis:

Internet Security Systems (ISS) X-Force has discovered a vulnerability in
the AIX frcactrl program. The Fast Response Cache Accelerator (FRCA) is a
kernel module that can be used with the IBM HTTP server to improve the
performance of a web server.  If the FRCA module is loaded, a local attacker
could use frcactrl, a program used to manage FRCA configuration, to modify
files.

Impact:

An attacker could gain root privileges by using the frcactrl program if the
FRCA kernel module is loaded.

Affected Versions:

The frcactrl command shipped with AIX 4.3 APAR IY02669 is vulnerable.

Description:

The AIX Fast Response Cache Accelerator (FRCA) is a kernel extension module
that improves the performance of a web server by using a memory cache to
store data being served from the web server. FRCA is used primarily with the
Apache-based IBM HTTP server, but it may also be used with other web
servers. The frcactrl program is used to manage the FRCA configuration and
is distributed as part of the base operating system in AIX 4.3. The
vulnerability is present on systems with AIX fix IY02669 applied and with
the FRCA kernel extension loaded (the kernel extension is not enabled by
default). The setuid bit of the frcactrl file is turned on by APAR
(Authorized Problem Analysis Report) IY02669, which allows non-root users to
configure the module. A malicious user may use frcactrl to manipulate the
configuration of the FRCA log files to create, append, or overwrite files as
root. 

Recommendations:

ISS recommends that if FRCA is not needed, the module can be unloaded with
the following command:
# /usr/sbin/frcactrl unload ; /usr/sbin/slibclean

Until an official fix is available, IBM recommends removing the setuid bit
from the frcactrl command:
# chmod 555 /usr/sbin/frcactrl

IBM is currently working on the following APARs, which will be available
soon:
APAR 4.3.x:  IY09514

APARs may be ordered using Electronic Fix Distribution (via FixDist) or from
the IBM Support Center. For more information on Fix Distribution go to:
http://service.software.ibm.com/support/rs6000 or send an email to
aixserv@austin.ibm.com with a subject of "FixDist".

Additional Information:

The Common Vulnerabilities and Exposures (CVE) project has assigned the name
CAN-2000-0249 to this issue. This is a candidate for inclusion in the CVE
list (http://cve.mitre.org), which standardizes names for security problems.

Credits:

This vulnerability was discovered and researched by Oliver Atoa-Ortiz of the
ISS X-Force. ISS would like to thank IBM for their response and handling of
this vulnerability.

_____

About Internet Security Systems (ISS)
ISS is a leading global provider of security management solutions for
e-business. By offering best-of-breed SAFEsuite (tm) security software,
industry-leading ePatrol (tm) managed security services, and strategic
consulting and education services, ISS is a trusted security provider to its
customers, protecting digital assets and ensuring the availability,
confidentiality and integrity of computer systems and information critical
to e-business success. ISS' lifecycle e-business security management
solutions protect more than 5,000 customers including 21 of the 25 largest
U.S. commercial banks, 9 of the 10 largest telecommunications companies and
over 35 government agencies. Founded in 1994, ISS is headquartered in
Atlanta, GA, with additional offices throughout North America and
international operations in Asia, Australia, Europe, Latin America and the
Middle East. For more information, visit the ISS Web site at www.iss.net or
call 888-901-7477.

Copyright (c) 2000 by Internet Security Systems, Inc.

Permission is hereby granted for the redistribution of this Alert
electronically. It is not to be edited in any way without express consent of
the X-Force. If you wish to reprint the whole or any part of this Alert in
any other medium excluding electronic medium, please e-mail xforce@iss.net
for permission.

Disclaimer

The information within this paper may change without notice. Use of this
information constitutes acceptance for use in an AS IS condition. There are
NO warranties with regard to this information. In no event shall the author
be liable for any damages whatsoever arising out of or in connection with
the use or spread of this information. Any use of this information is at the
user's own risk.

X-Force PGP Key available at: http://xforce.iss.net/sensitive.php3 as well
as on MIT's PGP key server and PGP.com's key server.

Please send suggestions, updates, and comments to: X-Force (xforce@iss.net)
of Internet Security Systems, Inc.

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