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                        SUSE Security Announcement

        Package:                kernel
        Announcement ID:        SUSE-SA:2009:047
        Date:                   Fri, 02 Oct 2009 10:00:00 +0000
        Affected Products:      All SUSE Linux and openSUSE products
        Vulnerability Type:     remote denial of service
        Severity (1-10):        6
        SUSE Default Package:   yes
        Cross-References:       CVE-2008-4609
                                FICORA #193744
                                CERT VU#943657
    Content of This Advisory:
        1) Security Vulnerability Resolved:
             TCP/IP denial of service attacks
           Problem Description
        2) Solution or Work-Around
        3) Special Instructions and Notes
        4) Pending Vulnerabilities, Solutions, and Work-Arounds:
            Please see SUSE Security Summary Report.
        5) Authenticity Verification and Additional Information

______________________________________________________________________________

1) Problem Description and Brief Discussion

   Outpost24 AB researchers Robert E. Lee and Jack C. Louis have found
   TCP/IP denial of service vulnerabilities which allow remote attackers   to allocate resources (memory and socket slots) on a targeted system
   indefinitely and so may cause a denial of the services on the
   attacked machine.

   The attack requires the attacker to be able to establish TCP/IP
   connections on the machine.  If all incoming connections are blocked,
   the system is not affected.

   The attacks itself are exploiting specific design limitations in the
   TCP/IP protocol.

   The upstream Linux kernel developers decided not to release updates at
   this time, so SUSE also does not plan to release updates to resolve
   this issue. Refer to the Workarounds section for suggestions on
   limiting the attack.

   Further references and information on this issue can be found on the
   CERT-FI page:
       https://www.kyberturvallisuuskeskus.fi/fi

   And in a generic paper on TCP/IP denial of service attacks:
       
   SUSE wishes to thank Outpost AB and CERT-FI for reporting these issues.

2) Solution or Work-Around

   As these attacks look like valid accesses to your internet facing
   services generally blocking them will not be possible.

   Options are to by-host limit incoming TCP/IP connections (before they
   are accepted) or block out sub nets if you see attacks coming from them.

   With today's botnets this will be difficult as any such blocks could
   be worked around by attackers.

3) Special Instructions and Notes

   Denial of service attack patterns these days are mostly flooding
   using large distributed botnets.
   Attackers will probably chose these more common methods instead of
   this more subtle one.

______________________________________________________________________________

4) Pending Vulnerabilities, Solutions, and Work-Arounds:

   See SUSE Security Summary Report.
______________________________________________________________________________

5) Authenticity Verification and Additional Information

  - Announcement authenticity verification:

    SUSE security announcements are published via mailing lists and on Web
    sites. The authenticity and integrity of a SUSE security announcement is
    guaranteed by a cryptographic signature in each announcement. All SUSE
    security announcements are published with a valid signature.

    To verify the signature of the announcement, save it as text into a file
    and run the command

      gpg --verify 

    replacing  with the name of the file where you saved the
    announcement. The output for a valid signature looks like:

      gpg: Signature made  using RSA key ID 3D25D3D9
      gpg: Good signature from "SuSE Security Team "

    where  is replaced by the date the document was signed.

    If the security team's key is not contained in your key ring, you can
    import it from the first installation CD. To import the key, use the
    command

      gpg --import gpg-pubkey-3d25d3d9-36e12d04.asc

  - Package authenticity verification:

    SUSE update packages are available on many mirror FTP servers all over the
    world. While this service is considered valuable and important to the free
    and open source software community, the authenticity and the integrity of
    a package needs to be verified to ensure that it has not been tampered
    with.

    The internal rpm package signatures provide an easy way to verify the
    authenticity of an RPM package. Use the command

     rpm -v --checksig 

    to verify the signature of the package, replacing  with the
    filename of the RPM package downloaded. The package is unmodified if it
    contains a valid signature from build@suse.de with the key ID 9C800ACA.

    This key is automatically imported into the RPM database (on
    RPMv4-based distributions) and the gpg key ring of 'root' during
    installation. You can also find it on the first installation CD and at
    the end of this announcement.

  - SUSE runs two security mailing lists to which any interested party may
    subscribe:

    opensuse-security@opensuse.org
        -   General Linux and SUSE security discussion.
            All SUSE security announcements are sent to this list.
            To subscribe, send an e-mail to
                .

    opensuse-security-announce@opensuse.org
        -   SUSE's announce-only mailing list.
            Only SUSE's security announcements are sent to this list.
            To subscribe, send an e-mail to
                .

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