[NEWS] MacOS X DirectoryService Privilege Escalation and DoS Attack

From: support@securiteam.com
Date: 04/18/03

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    From: support@securiteam.com
To: list@securiteam.com
Date: 18 Apr 2003 12:30:45 +0200

    The following security advisory is sent to the securiteam mailing list, and can be found at the SecuriTeam web site: http://www.securiteam.com
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      MacOS X DirectoryService Privilege Escalation and DoS Attack
    ------------------------------------------------------------------------

    SUMMARY

    DirectoryServices is part of the MacOS X information and authentication
    subsystem. It is launched at startup, setuid root and installed by
    default. It is vulnerable to several attacks ultimately allowing a local
    user to obtain root privileges.

    DETAILS

    Vulnerable systems:
     * MacOS X (10.2.4 and below)

    Immune systems:
     * Mac OS X 10.2.5

    During the startup of DirectoryService, the application creates a lock
    file by executing the touch(1) UNIX command. It executes touch through the
    system() libc function. This function is inherently insecure and its use
    is strongly discouraged in privileged applications.

    Since this call to system() does not specify a full path to the touch(1)
    command, it is possible for an attacker to modify the PATH environment
    variable to specify a directory containing her own version of the touch(1)
    command. In this instance, this would cause DirectoryService to execute
    arbitrary commands as root.

    In order for an attacker to exploit this vulnerability, they must first
    cause DirectoryServices to terminate. This can be done by simply
    connecting to port 625 repeatedly using an automated program.

    Timeline:
    03/25/2003 Apple notified via email.
    03/28/2003 Apple verified.
    04/10/2003 Coordinated release.

    Vendor Response:
    "Directory Services: Fixes CAN-2003-0171 DirectoryServices Privilege
    Escalation and DoS Attack. DirectoryService is part of the Mac OS X and
    Mac OS X Server information services subsystem. It is launched at startup,
    setuid root and installed by default. It is possible for a local attacker
    to modify an environment variable that would allow the execution of
    arbitrary commands as root. Credit to Dave G. from @stake, Inc. for the
    discovery of this vulnerability."

    @stake Recommendation:
    @stake recommends that user upgrade to Mac OS X 10.2.5.

    ADDITIONAL INFORMATION

    The original advisory can be downloaded from:
    <www.atstake.com/research/advisories/2003/a041003-1.txt>
    www.atstake.com/research/advisories/2003/a041003-1.txt

    The information has been provided by <mailto:daveg@atstake.com> Dave G.
    of @Stake.

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