[VulnWatch] @stake: AppleFileServer Remote Command Execution

From: _at_stake Advisories (_at_stake)
Date: 05/04/04

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    Date: Mon, 03 May 2004 18:30:50 -0400
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                                    @stake, Inc.
                                  www.atstake.com

                                 Security Advisory

    Advisory Name: AppleFileServer Remote Command Execution
     Release Date: 05/03/2004
      Application: AppleFileServer
         Platform: MacOS X 10.3.3 and below
         Severity: A remote attacker can execute arbitrary
                   commands as root
          Authors: Dave G. <daveg@atstake.com>
                   Dino Dai Zovi <ddaizovi@atstake.com>
    Vendor Status: Informed, Upgrade Available
    CVE Candidate: CAN-2004-0430
        Reference: www.atstake.com/research/advisories/2004/a050304-1.txt

    Overview:

    The AppleFileServer provides Apple Filing Protocol (AFP) services for
    both Mac OS X and Mac OS X server. AFP is a protocol used to
    remotely mount drives, similar to NFS or SMB/CIFS. There is a
    pre-authentication, remotely exploitable stack buffer overflow that
    allows an attacker to obtain administrative privileges and execute
    commands as root.

    Details:

    The AppleFileServer provides Apple Filing Protocol (AFP) services
    for both Mac OS X and Mac OS X server. AFP is a protocol used to
    remotely mount drives, similar to NFS or SMB/CIFS. AFP is not
    enabled by default. It is enabled through the Sharing Preferences
    section by selecting the 'Personal File Sharing' checkbox.

    Thereis a pre-authentication remotely exploitable stack buffer
    overflow that allows an attacker to obtain administrative
    privileges. The overflow occurs when parsing the PathName argument
    from LoginExt packet requesting authentication using the Cleartext
    Password User Authentication Method (UAM). The PathName argument
    is encoded as one-byte specifying the string type, two-bytes
    specifying the string length, and finally the string itself. A
    string of type AFPName (0x3) that is longer than the length declared
    in the packet will overflow the fixed-size stack buffer.

    The previously described malformed request results in a trivially
    exploitable stack buffer overflow. @stake was able to quickly
    develop a proof-of-concept exploit that portably demonstrates this
    vulnerability across multiple Mac OS X versions including Mac OS X
    10.3.3, 10.3.2, and 10.2.8.

    Vendor Response:

    - From APPLE-SA-2004-05-03 Security Update 2004-05-03

    AppleFileServer: Fixes CAN-2004-0430 to improve the handling of long
    passwords. Credit to Dave G. from @stake for reporting this issue.

    Security Update 2004-05-03 may be obtained from:

      * Software Update pane in System Preferences

      * Apple's Software Downloads web site:

        For Mac OS X 10.3.3 "Panther"
        =============================
        http://download.info.apple.com/Mac_OS_X/061-1213.20040503.vngr3/
    2Z/SecUpd2004-05-03Pan.dmg
        The download file is named: "SecUpd2004-05-03Pan.dmg"
        Its SHA-1 digest is: 6f35539668d80ee536305a4146bd982a93706532
        
        For Mac OS X Server 10.3.3
        ==========================
        http://download.info.apple.com/Mac_OS_X/061-1215.20040503.mPp9k/
    2Z/SecUpdSrvr2004-05-03Pan.dmg
        The download file is named: "SecUpdSrvr2004-05-03Pan.dmg"
        Its SHA-1 digest is: 3c7da910601fd36d4cdfb276af4783ae311ac5d7
        
        For Mac OS X 10.2.8 "Jaguar"
        =============================
        http://download.info.apple.com/Mac_OS_X/061-1217.20040503.BmkY5/
    2Z/SecUpd2004-05-03Jag.dmg
        The download file is named: "SecUpd2004-05-03Jag.dmg"
        Its SHA-1 digest is: 11d5f365e0db58b369d85aa909ac6209e2f49945
        
        For Mac OS X Server 10.2.8
        ==========================
        http://download.info.apple.com/Mac_OS_X/061-1219.20040503.Zsw3S/
    2Z/SecUpdSrvr2004-05-03Jag.dmg
        The download file is named: "SecUpdSrvr2004-05-03Jag.dmg"
        Its SHA-1 digest is: 28859a4c88f6e1d1fe253388b233a5732b6e42fb

    Timeline

    3/26/2004 Vendor notified of issue
    5/04/2004 Vendor informs us that they have a patch available
    4/04/2004 Advisory released

    Recommendation:

    If you do not need AFS, disable it. If you do need it, upgrade to
    the latest version of Panther.

    Common Vulnerabilities and Exposures (CVE) Information:

    The Common Vulnerabilities and Exposures (CVE) project has assigned
    the following names to these issues. These are candidates for
    inclusion in the CVE list (http://cve.mitre.org), which standardizes
    names for security problems.

      CAN-2004-0430 AppleFileServer Remote Command Execution

    Open Source Vulnerability Database (OSVDB) Information:
    More information available at www.osvdb.org

      OSVDB ID 5762

    @stake Vulnerability Reporting Policy:
    http://www.atstake.com/research/policy/

    @stake Advisory Archive:
    http://www.atstake.com/research/advisories/

    PGP Key:
    http://www.atstake.com/research/pgp_key.asc

    Copyright 2004 @stake, Inc. All rights reserved.

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