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Apple Mac OS X vpnd Server_id Buffer Overflow Vulnerability

05.04.05

BACKGROUND

Mac OS X is an operating system for the Apple family of microcomputers.
More information is available at the following link:

    http://www.apple.com/macosx/

DESCRIPTION

Local exploitation of a buffer overflow vulnerability in Apple Computer,
Inc.'s Mac OS X allows attackers to execute arbitrary code.

vpnd is the system daemon which manages IPSEC or PPTP connections. The
vulnerability specifically exists due to insufficient bounds checking on
the value given to the Server_id parameter. Server_id may be set from
the command line via the -i option. The Server_id is then referenced
from the com.apple.RemoteAccessServers.pslist file in the
/Library/Preferences/SystemConfiguration directory to load the
appropriate configuration profile. Local attackers can supply an overly
long Server_id value to overflow the buffer and execute arbitrary code.

ANALYSIS

Successful exploitation of this vulnerability will result in execution of
arbitrary code with root privileges. It should be noted that the
com.apple.RemoteAccessServers.pslist file is only present by default on
Server platforms. On standard OS X installs, the file must be created
manually or generated by the graphical network configuration tools in
order for vpnd to execute far enough to cause the overflow to occur.

DETECTION

iDEFENSE has confirmed that Mac OS X 10.3.7 is vulnerable. The vendor
has indicated that all versions prior to OS X 10.3.9 are vulnerable.

WORKAROUND

As a workaround solution, remove the executable privilege bit for
non-root users from the /usr/sbin/vpnd binary until the vendor releases
a patch.

VENDOR RESPONSE

The vulnerability is addressed in Apple Security Update 2005-005:

    http://docs.info.apple.com/article.html?artnum=301528

CVE INFORMATION

The Common Vulnerabilities and Exposures (CVE) project has assigned the
name CAN-2005-1343 to this issue. This is a candidate for inclusion in
the CVE list (http://cve.mitre.org), which standardizes names for
security problems.

DISCLOSURE TIMELINE

04/25/2005   Initial vendor notification
04/27/2005   Initial vendor response
05/04/2005   Coordinated public disclosure

CREDIT

Jason Aras is credited with this vulnerability.

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LEGAL NOTICES

Copyright © 2005 Verisign, Inc.

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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.