iDefense Security Advisory 05.24.07: Apple Computer Mac OS X pppd Plugin Loading Privilege Escalation Vulnerability

Apple Computer Mac OS X pppd Plugin Loading Privilege Escalation
Vulnerability

iDefense Security Advisory 05.24.07
http://labs.idefense.com/intelligence/vulnerabilities/
May 24, 2007

I. BACKGROUND

Apple Mac OS X pppd is a setuid root application that is used to
establish and configure connections for point to point links. It is
commonly used for configuring traditional dial-up modem and DSL
connections. More information can be found at the following URL.

http://developer.apple.com/documentation/Darwin/Reference/Manpages/man8/pppd.8.html

II. DESCRIPTION

Local exploitation of a privilege escalation vulnerability in Apple
Computer Inc.'s Mac OS X pppd could allow an attacker to gain root
privileges.

The vulnerability exists due to insufficient access validation when
processing the "plugin" command line option. The application does not
properly verify that the requesting user has root privileges and allows
any user to load plug-ins.

When checking to see if the executing user has root privileges, a check
is made to see if the stdin file descriptor is owned by root. Passing
this check is trivial and allows the attacker to load arbitrary
plug-ins resulting in arbitrary code execution with root privileges.

III. ANALYSIS

Exploitation is trivial and grants root access.

This vulnerability cannot be triggered remotely; an attacker needs local
access to the victim's system in order to exploit this vulnerability.
pppd is installed by default.

IV. DETECTION

iDefense has confirmed the existence of this vulnerability in version
10.4.8 of Mac OS X. Other versions may also be affected.

V. WORKAROUND

Remove the setuid bit from the pppd binary. This will prevent users
without root privileges from being able to properly use the program.

VI. VENDOR RESPONSE

Apple Inc has addressed this vulnerability in Apple Security Update
2007-005. More information can be found from Apple's Security Update
page or the Security Update 2007-005 advisory page at the respective
URLs below.

http://docs.info.apple.com/article.html?artnum=61798
http://docs.info.apple.com/article.html?artnum=305530

VII. CVE INFORMATION

The Common Vulnerabilities and Exposures (CVE) project has assigned the
name CVE-2007-0752 to this issue. This is a candidate for inclusion in
the CVE list (http://cve.mitre.org/), which standardizes names for
security problems.

VIII. DISCLOSURE TIMELINE

01/08/2007 Initial vendor notification
01/09/2007 Initial vendor response
05/24/2007 Coordinated public disclosure

IX. CREDIT

The discoverer of this vulnerability wishes to remain anonymous.

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X. LEGAL NOTICES

Copyright © 2007 iDefense, 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.