IBM DB2 generate_distfile buffer overflow vulnerability (#NISR2122004L)

From: NGSSoftware Insight Security Research (nisr_at_nextgenss.com)
Date: 12/23/04

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    To: <bugtraq@securityfocus.com>, <ntbugtraq@listserv.ntbugtraq.com>, <vulnwatch@vulnwatch.org>
Date: Thu, 23 Dec 2004 17:05:53 -0000

    NGSSoftware Insight Security Research Advisory

    Name: IBM DB2 generate_distfile buffer overflow
    Systems Affected: DB2 8.1/7.x
    Severity: High risk
    Vendor URL: http://www.ibm.com/
    Author: David Litchfield [ david at ngssoftware.com ]
    Relates to: http://www.nextgenss.com/advisories/db2-01.txt
    Date of Public Advisory: 23rd December 2004
    Advisory number: #NISR2122004L
    Advisory URL: http://www.ngssoftware.com/advisories/db223122004L.txt

    Description
    ***********
    IBM's DB2 database server contains a procedure, generate_distfile. This
    procedure suffers from a stack based buffer overflow vulnerability.

    Details
    *******
    The generate_distfile procedure is vulnerable to a buffer overflow
    vulnerability. generate_distfile is implemented as a C function, exported by
    db2dbappext.dll. It takes as its third parameter the name of a file. This
    parameter can be up to 255 characters long.

    One of the sub functions of generate_distfile takes the third parameter, the
    user supplied filename, and appends it to the directory where DB2 has been
    installed. It does this by creating a 264 byte buffer on the stack. The
    subfunction then calls sqloInstancePath() to get the install path for DB2.
    This returns C:\PROGRA~1\IBM\SQLLIB\DB2. \tmp\ is then appended to this.
    After \tmp\ is appended the user supplied filename is appended using a while
    loop that continues to copy data until a NULL terminator is found. Because
    the DB2 install path (C:\PROGRA~1\IBM\SQLLIB\DB2\tmp\) takes up some of the
    buffer, if the user has supplied a thrid parameter of 255 bytes the stack
    based buffer is overflowed.

    However, once the buffer is overflowed, as well as overwriting the saved
    return address, a pointer is also overwritten. This pointer points to a
    buffer where the resulting full path should be copied to. This interupts a
    straight return address overwrite exploit; however it can still easily be
    exploited in several ways. Due to the fact that the attacker "owns" the
    pointer to where the path is copied to, they can write arbitrary data to an
    arbitrary location allowing a full compromise. Once such method would be to
    overwrite the pointer to the Windows UnhandledExceptionFilter function; as
    access violations aren't handled, the UEF kicks in an as the attacker
    controls the UEF the flow of execution can be redirected by the attacker to
    arbitrary code.

    Note - whilst the discussion has used Windows paths *nix versions of DB2 are
    also vulnerable.

    Fix Information
    ***************
    IBM has written a patch and can be obtained with the latest fixpak.

    http://www-306.ibm.com/software/data/db2/udb/support/downloadv8.html - DB2
    v8.1
    http://www-306.ibm.com/software/data/db2/udb/support/downloadv7.html - DB2
    v7.x

    NGSSQuirreL for DB2 (http://www.nextgenss.com/db2.htm) can be used to assess
    whether your DB2 server is vulnerable to this.

    About NGSSoftware
    *****************
    NGSSoftware design, research and develop intelligent, advanced application
    security assessment scanners. Based in the United Kingdom, NGSSoftware have
    offices in the South of London and the East Coast of Scotland. NGSSoftware's
    sister company NGSConsulting, offers best of breed security consulting
    services, specialising in application, host and network security
    assessments.

    http://www.ngssoftware.com/

    Telephone +44 208 401 0070
    Fax +44 208 401 0076

    enquiries@ngssoftware.com

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