[Security Bulletin] SSRT4696 rev.0 - HP Tru64 UNIX TCP Stack Remote Denial of Service (DoS)

From: Boren, Rich (SSRT) (rich.boren_at_hp.com)
Date: 12/23/04

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    SSRT4696 rev.0 - HP Tru64 UNIX TCP Stack
                     Remote Denial of Service (DoS)

    There are no restrictions for distribution of this Bulletin
    provided that it remains complete and intact.

    The information in this Security bulletin should be acted upon
    as soon as possible.

    22 December 2004

    Remote Denial of Service (DoS)

    HP Software Security Response Team

    NISCC Advisory 236929, CVE CAN-2004-0230

        A potential security vulnerability has been identified in the
        Transmission Control Protocol (TCP) on HP Tru64 UNIX systems.
        The potential vulnerability could be remotely exploitable,
        resulting in denial of service (DoS).

    SUPPORTED SOFTWARE VERSIONS*: ONLY impacted versions are listed.
            HP Tru64 UNIX V5.1B PK4
            HP Tru64 UNIX V5.1B PK3
            HP Tru64 UNIX V5.1A PK6
            HP Tru64 UNIX V4.0G PK4
            HP Tru64 UNIX V4.0F PK8

      Special Instructions:

      The industry standard TCP specification (RFC793) has a
      vulnerability whereby established TCP connections can be
      reset by an attacker.

      TCP sessions, including Telnet, SSH, SFTP and HTTP may be
      disconnected without warning. TCP sessions that have been
      disconnected can be re-established.

      HP Tru64 UNIX has addressed this potential vulnerability, called
      a TCP reset attack, by providing a new kernel tunable variable,
      tcp_rst_win (TCP reset window).

      The tcp_rst_win variable mitigates the TCP reset attack by
      reducing the window size in which a TCP reset packet will be
      accepted by the Tru64 system.

      Set the tunable as follows:

      tcp_rst_win = -1 (default)

        Retains existing TCP behavior.

      tcp_rst_win = 2048

      Provides a level of protection which will significantly reduce
      the size of the TCP reset window while allowing for common TCP
      client/server sequence number variations. This will allow a
      reset packet to be accepted by the Tru64 system when the remote
      machine has unacknowledged outstanding packets of up to a total
      of 2048 bytes.

      tcp_rst_win = 0

       Provides maximum security against the potential DoS condition.

       Setting tcp_rst_win to "0" provides the highest level of
       protection without migrating to an IPSec environment. This
       setting restricts the acceptance of a reset packet to the
       current sequence number and may result in the rejection of
       valid reset packets where sent data packets have not been

       Customers who are extremely sensitive to this security threat
       should implement IPSec, available in HP Tru64 UNIX 5.1A and
       5.1B. Tru64 UNIX V4.0F and V4.0G can receive maximum available
       protection with tcp_rst_win to "0".

      The TCP reset window variable (tcp_rst_win) may be adjusted
      using the "sysconfig" and "sysconfigdb" commands:

      # sysconfig -q inet tcp_rst_win
      tcp_rst_win = -1

      # sysconfig -r inet tcp_rst_win=2048
      tcp_rst_win: reconfigured

      # sysconfig -q inet tcp_rst_win
      tcp_rst_win = 2048

      # sysconfig -q inet tcp_rst_win > /tmp/tcp_rst_win_merge

      # sysconfigdb -m -f /tmp/tcp_rst_win_merge inet

      # sysconfigdb -l inet

            tcp_rst_win = 2048

        The fixes contained in the ERP kits are scheduled to be
        available in the following mainstream patch kits:

        HP Tru64 UNIX V5.1B PK 5
        HP Tru64 UNIX V5.1A PK 7

        Until the corrections are available in mainstream release
        patch kits, HP is releasing the following Early Release Patch
       (ERP) kits publicly for use by any customer.

        The ERP kits use dupatch to install and will not install over
        any installed Customer Specific Patches (CSPs) that have file
        intersections with the ERPs. Contact your service provider
        for assistance if the installation of the ERPs is blocked by
        any of your installed CSPs.

    HP Tru64 UNIX 5.1B-2/PK4
    ERP Kit Name: T64KIT0024531-V51BB25-ES-20041219
    General ITRC Patch Page:
    Kit Location:

    HP Tru64 UNIX 5.1B-1/PK3
    ERP Kit Name: T64KIT0024529-V51BB24-ES-20041219
    General ITRC Patch Page:
    Kit Location:

    HP Tru64 UNIX 5.1A
    PREREQUISITE: HP Tru64 UNIX with 5.1A with PK6 installed
    ERP Kit Name: T64KIT0024527-V51AB24-ES-20041219
    General ITRC Patch Page:
    Kit Location:

    HP Tru64 UNIX 4.0G
    PREREQUISITE: HP Tru64 UNIX with 4.0G with PK4 installed
    ERP Kit Name: T64KIT0024524-V40GB22-ES-20041219
    General ITRC Patch Page:
    Kit Location:

    HP Tru64 UNIX 4.0F
    PREREQUISITE: HP Tru64 UNIX with 4.0F with PK8 (BL22) installed
    ERP Kit Name: DUXKIT0024523-V40FB22-ES-20041219
    General ITRC Patch Page:
    Kit Location:

        Revision 0 - 22 December 2004
                  Initial Release

    * The software product category that this Security Bulletin
      relates to is represented by the 5th and 6th characters of the
      Bulletin number: GN=General, MA=Management Agents,
      MI=Misc. 3rd party, MP=HP-MPE/iX, NS=HP NonStop Servers,
      OV=HP OpenVMS, PI=HP Printing & Imaging, ST=HP Storage,
      TU=HP Tru64 UNIX, TL=Trusted Linux, UX=HP-UX, VV=Virtual Vault

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    System management and security procedures must be reviewed
    frequently to maintain system integrity. HP is continually
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    to provide customers with current secure solutions.

    "HP is broadly distributing this Security Bulletin in order to
    bring to the attention of users of the affected HP products the
    important security information contained in this Bulletin. HP
    recommends that all users determine the applicability of this
    information to their individual situations and take appropriate
    action. HP does not warrant that this information is necessarily
    accurate or complete for all user situations and, consequently,
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    (c)Copyright 2004 Hewlett-Packard Development Company, L.P.
    Hewlett-Packard Company shall not be liable for technical or
    editorial errors or omissions contained herein. The information
    provided is provided "as is" without warranty of any kind. To the
    extent permitted by law, neither HP or its affiliates,
    subcontractors or suppliers will be liable for incidental, special
    or consequential damages including downtime cost; lost profits;
    damages relating to the procurement of substitute products or
    services; or damages for loss of data, or software restoration.
    The information in this document is subject to change without
    notice. Hewlett-Packard Company and the names of Hewlett-Packard
    products referenced herein are trademarks of Hewlett-Packard
    Company in the United States and other countries. Other product
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    Version: PGP 8.1

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