[VulnWatch] iDEFENSE Security Advisory 06.23.05: Veritas Backup Exec Agent CONNECT_CLIENT_AUTH Buffer Overflow Vulnerability

From: iDEFENSE Labs (labs-no-reply_at_idefense.com)
Date: 06/23/05

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    Date: Thu, 23 Jun 2005 17:44:03 -0400
    To: <bugtraq@securityfocus.com>, <vulnwatch@vulnwatch.org>, <full-disclosure@lists.grok.org.uk>
    
    

    Veritas Backup Exec Agent CONNECT_CLIENT_AUTH Buffer Overflow
    Vulnerability

    iDEFENSE Security Advisory 06.23.05
    www.idefense.com/application/poi/display?id=272&type=vulnerabilities
    June 23, 2005

    I. BACKGROUND

    VERITAS Backup Exec is an advanced backup and restore solution for
    Microsoft Windows server environments. More information is available
    from the vendor's website:

       http://veritas.com/Products/www?c=product&refId=57

    II. DESCRIPTION

    Exploitation of a buffer overflow vulnerability in Veritas Software
    Corp.'s Backup Exec allows remote attackers to execute arbitrary code.

    The Veritas Backup Exec Agent listens on TCP port 10000 and is
    responsible for accepting connections from the backup server when a
    backup is to occur. Typically the agent would be installed on most
    servers and important workstations in an enterprise environment.

    Veritas Backup Exec uses the standard NMDP protocol to communicate with
    the listening agents. The NMDP protocol allows multiple authentication
    types, including support for Windows user credentials.

    The vulnerability specifically exists because of insufficient input
    validation on CONNECT_CLIENT_AUTH requests. CONNECT_CLIENT_AUTH requests
    sent with an authentication method type "3," indicating Windows user
    credentials, and an overly long password argument can overflow the
    buffer and lead to arbitrary code execution. The overflow will copy the
    user-supplied password to the stack until it attempts to run off the
    page of memory. At this point, the SEH frame will be overwritten and the
    program will jump to a user-defined location when the page fault occurs.
    Debugger output showing control of execution from the SEH frame is
    detailed as follows:

    (1d8.b1c): Access violation - code c0000005 (first chance)
    First chance exceptions are reported before any exception handling.
    This exception may be expected and handled.

    eax=00002001 ebx=0032ad78 ecx=0000037e
    edx=00fbedf8 esi=01045928 edi=00fc0000
    eip=0141b77f esp=00fbedd8 ebp=0032c040 iopl=0
    nv up ei pl nz na po nc
    cs=001b ss=0023 ds=0023 es=0023 fs=003b gs=0000 efl=00010206

    *** ERROR: Symbol file could not be found. Defaulted to export symbols
    for C:\Program Files\VERITAS\Backup Exec\NT\beclass.dll -
    beclass!DeasciifyAndDecrypt+0xaf:

    0141b77f f3a5 rep movsd ds:01045928=39784638 es:00fc0000=????????
    0:005> g

    (1d8.b1c): Access violation - code c0000005 (first chance)
    First chance exceptions are reported before any exception handling.
    This exception may be expected and handled.

    eax=00000000 ebx=00000000 ecx=41424344
    edx=7c9037d8 esi=00000000 edi=00000000
    eip=41424344 esp=00fbea08 ebp=00fbea28 iopl=0
    nv up ei pl zr na po nc
    cs=001b ss=0023 ds=0023 es=0023 fs=003b gs=0000 efl=00010246
    41424344 ?? ???
    0:005> kp
    ChildEBP RetAddr
    WARNING: Frame IP not in any known module. Following frames may be
    wrong.
    00fbea04 7c9037bf 0x41424344
    00fbea28 7c90378b ntdll!RtlConvertUlongToLargeInteger+0x7a
    00fbead8 7c90eafa ntdll!RtlConvertUlongToLargeInteger+0x46
    0032c040 0032b470 ntdll!KiUserExceptionDispatcher+0xe
    00000003 00000000 0x32b470

    III. ANALYSIS

    Exploitation does not require authentication, thereby allowing any
    remote attacker to execute arbitrary code under the privileges of the
    Backup Exec Agent Browser (benetns.exe) process, which is usually a
    domain administrative account. Exploitation can occur fairly reliably
    since the overflow is able to control code execution via the structured
    exception handler.

    IV. DETECTION

    iDEFENSE has confirmed the existence of this vulnerability in Backup
    Exec for Windows Servers versions 9.1 and 10.0. It is suspected
    that other versions are also vulnerable.

    Several vendors ship or use Veritas software including Hitachi and NEC
    Corporation.

    V. WORKAROUND

    Use a firewall to restrict incoming connections to trusted workstations
    running the Backup Exec client software which uses port 10000 TCP.

    VI. VENDOR RESPONSE

    The vendor has addressed this vulnerability in security advisory
    VX05-002:

       http://seer.support.veritas.com/docs/276604.htm

    VII. CVE INFORMATION

    The Common Vulnerabilities and Exposures (CVE) project has assigned the
    name CAN-2005-0773 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

    03/16/2005 Initial vendor notification
    03/30/2005 Initial vendor response
    06/22/2005 Coordinated public disclosure

    IX. CREDIT

    The discoverer of this vulnerability wishes to remain anonymous.

    Get paid for vulnerability research
    http://www.idefense.com/poi/teams/vcp.jsp

    Free tools, research and upcoming events
    http://labs.idefense.com

    X. LEGAL NOTICES

    Copyright (c) 2005 iDEFENSE, Inc.

    Permission is granted for the redistribution of this alert
    electronically. It may not be edited in any way without the express
    written consent of iDEFENSE. If you wish to reprint the whole or any
    part of this alert in any other medium other than electronically, please
    email customerservice@idefense.com for permission.

    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.


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