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IBM SECURITY ADVISORY

First Issued: Thu Aug 16 20:31:59 CDT 2007
===============================================================================
                           VULNERABILITY SUMMARY

VULNERABILITY:   BIND remote DNS cache poisoning

PLATFORMS:       AIX 5.2, 5.3

SOLUTION:        Apply the APAR, interim fix or workaround as described
                 below.

THREAT:          DNS cache may be poisoned due to week DNS query IDs.

CERT VU Number:  CVE-2007-2926
CVE Number:      252735
===============================================================================
                           DETAILED INFORMATION

I. OVERVIEW

    Berkeley Internet Name Domain 9 (BIND9) is a Domain Name System (DNS)
    distribution from the Internet Systems Consortium (ISC) and it is included
    with AIX 5.2 and 5.3. At this time, all versions of AIX 5.2 and 5.3 include
    BIND 9.2.

II. DESCRIPTION

    The ISC has issued a patch for a security vulnerability in some versions of
    BIND 9 that can be exploited by a remote attacker to guess the DNS query
    IDs and poison the DNS cache.

    For more details please visit:

        http://www.isc.org/sw/bind/bind-security.php
        http://www.kb.cert.org/vuls/id/252735

III. IMPACT

    From the ISC BIND advisory:

        The DNS query id generation is vulnerable to cryptographic analysis
        which provides a 1 in 8 chance of guessing the next query id for 50% of
        the query ids.  This can be used to perform cache poisoning by an
        attacker.

        This bug only affects outgoing queries, generated by BIND 9 to answer
        questions as a resolver, or when it is looking up data for internal
        uses, such as when sending NOTIFYs to slave name servers.

IV. PLATFORM VULNERABILITY ASSESSMENT

    To determine if your system is vulnerable, run the following command:

    # lslpp -l | grep bos.net.tcp.server
    # lslpp -l | grep bos.net.tcp.client

    The following filesets are vulnerable:

    AIX Level    Fileset                Lower Level     Upper Level
    ---------------------------------------------------------------
    5.2.0        bos.net.tcp.server     5.2.0.85        5.2.0.107
    5.2.0        bos.net.tcp.client     5.2.0.85        5.2.0.107
    5.3.0        bos.net.tcp.server     5.3.0.40        5.3.0.62
    5.3.0        bos.net.tcp.client     5.3.0.40        5.3.0.62

    NOTE: The above filesets are those currently supported by IBM.  Previous
    versions of the fileset may also be vulnerable.  Affected customers are
    urged to upgrade to the latest applicable Technology Level and Service
    Pack.

V. SOLUTIONS

    A. APARS

        IBM provides the following fixes:

        AIX Level           APAR number       Availability
        --------------------------------------------------------------------
        5.2.0               IZ02218           10/31/2007 (subject to change)
        5.3.0               IZ02219           11/27/2007 (subject to change)

        AIX Version 5 APARs can be downloaded from:

        http://www.ibm.com/servers/eserver/support/unixservers/aixfixes.html

        NOTE: Affected customers are urged to upgrade to the latest applicable
        Technology Level and Service Pack.

    B. INTERIM FIXES

        Interim fixes are available.  The interim fix can be downloaded via
        ftp from:

        ftp://aix.software.ibm.com/aix/efixes/security/bindcrypt_ifix.tar.Z

        This is a compressed tarball containing this advisory, interim fix
        packages and PGP signatures for each package.  The interim fixes below
        include prerequisite checking. This will enforce the correct mapping
        between the fixes and AIX Technology Levels.

        AIX Release & Technology Level         Interim fix
        ---------------------------------------------------------------
        5200-08                                IZ02218_08.070814.epkg.Z
        5200-09                                IZ02218_09.070814.epkg.Z
        5200-10                                IZ02218_10.070810.epkg.Z
        5300-04                                IZ02219_04.070814.epkg.Z
        5300-05                                IZ02219_05.070814.epkg.Z
        5300-06                                IZ02219_06.070810.epkg.Z

        IMPORTANT: If possible, it is recommended that a mksysb backup of the
        system be created.  Verify it is both bootable and readable before
        proceeding.

        These interim fixes have not been fully regression tested; thus, IBM
        does not warrant the fully correct functionality of the interim fix.
        Customers install the interim fix and operate the modified version of
        AIX at their own risk.

        Verify you have retrieved the fixes intact:

        The interim fixes below are named by using the technology level
        corresponding to the release that the fix applies to. The checksums
        below were generated using the "sum" and "md5sum" commands and are as
        follows:

        Filename                   sum        md5sum
        ----------------------------------------------------------------------
        IZ02218_08.070814.epkg.Z  40008 3296  5bf5384341dc7e00e0cc378e3144ae8b
        IZ02218_09.070814.epkg.Z  26768 3291  e0e6ea57ff375715ed5cedd3238b8317
        IZ02218_10.070810.epkg.Z  39720 3293  9528b87acaddfd83f7351eca2d946fb7
        IZ02219_04.070814.epkg.Z  08276 3214  eb1326b75f19ac84eae237882044beb8
        IZ02219_05.070814.epkg.Z  44939 3220  edaa7f8e167cbe3f5ca14040d648e1a9
        IZ02219_06.070810.epkg.Z  29152 3228  886a25c351f61e2f1f1fa994bd780da3

        These sums should match exactly. The PGP signatures in the
        compressed tarball and on this advisory can also be used to verify
        the integrity of the various files they correspond to.  If the sums
        or signatures cannot be confirmed, double check the command results
        and the download site address.  If those are OK, contact IBM AIX
        Security at security-alert@austin.ibm.com and describe the
        discrepancy.

    C. INTERIM FIX INSTALLATION

        These packages use the new Interim Fix Management Solution to install
        and manage interim fixes.  More information can be found at:

        http://www14.software.ibm.com/webapp/set2/sas/f/aix.efixmgmt/home.html

        To preview an epkg interim fix installation execute the following
        command:

        # emgr -e ipkg_name -p       # where ipkg_name is the name of the
                                     # interim fix package being previewed.

        To install an epkg interim fix package, execute the following command:

        # emgr -e ipkg_name -X       # where ipkg_name is the name of the
                                     # interim fix package being installed.

        The "X" flag will expand any filesystems if required.

VI. WORKAROUNDS

    If you are running BIND9 there are no known workarounds.  If the service
    is not needed and is running, shut it down.

VII. OBTAINING FIXES

    AIX Version 5 APARs can be downloaded from:

        http://www.ibm.com/servers/eserver/support/unixservers/aixfixes.html

    Security related Interim Fixes can be downloaded from:

        ftp://aix.software.ibm.com/aix/efixes/security

VII. CONTACT INFORMATION

    If you would like to receive AIX Security Advisories via email, please
    visit:

        http://www14.software.ibm.com/webapp/set2/subscriptions/pqvcmjd

    Comments regarding the content of this announcement can be directed to:

        security-alert@austin.ibm.com

    To request the PGP public key that can be used to communicate
    securely with the AIX Security Team send email to
    security-alert@austin.ibm.com with a subject of "get key". The key
    can also be downloaded from a PGP Public Key Server. The key id is
    0x4265D862.

    Please contact your local IBM AIX support center for any assistance.

    eServer is a trademark of International Business Machines Corporation.
    IBM, AIX and pSeries are registered trademarks of International Business
    Machines Corporation.  All other trademarks are property of their
    respective holders.

VIII. ACKNOWLEDGMENTS

    This vulnerability was reported by ISC who credit Amit Klein from Trusteer
    (http://www.trusteer.com/).

    http://www.trusteer.com/docs/bind9dns.html

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