HP SECURITY BULLETIN

HPSBTU01077     REVISION: 0

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

NOTICE:  
	

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.
INITIAL RELEASE:   	

22 December 2004 

POTENTIAL SECURITY IMPACT:   	

Remote Denial of Service (DoS)
SOURCE:   	

HEWLETT-PACKARD COMPANY
HP Software Security Response Team
REFERENCES:   	

NISCC Advisory 236929, CVE CAN-2004-0230
VULNERABILITY SUMMARY:
    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
BACKGROUND:

For a PGP signed version of this bulletin please write
to security-alert@hp.com


  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
   acknowledged.

   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
  inet:
  tcp_rst_win = -1

  # sysconfig -r inet tcp_rst_win=2048
  tcp_rst_win: reconfigured

  # sysconfig -q inet tcp_rst_win
  inet:
  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

  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
RESOLUTION:
    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:  http://www.itrc.hp.com/service/patch/mainPage.do
Kit Location:  
http://www.itrc.hp.com/service/patch/patchDetail.do?patchid=T64KIT0024531-V51BB25-ES-20041219

HP Tru64 UNIX 5.1B-1/PK3
ERP Kit Name:        T64KIT0024529-V51BB24-ES-20041219
General ITRC Patch Page:  http://www.itrc.hp.com/service/patch/mainPage.do
Kit Location:  
http://www.itrc.hp.com/service/patch/patchDetail.do?patchid=T64KIT0024529-V51BB24-ES-20041219

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:  http://www.itrc.hp.com/service/patch/mainPage.do
Kit Location:  
http://www.itrc.hp.com/service/patch/patchDetail.do?patchid=T64KIT0024527-V51AB24-ES-20041219

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:  http://www.itrc.hp.com/service/patch/mainPage.do
Kit Location:
http://www.itrc.hp.com/service/patch/patchDetail.do?patchid=T64KIT0024524-V40GB22-ES-20041219

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:  http://www.itrc.hp.com/service/patch/mainPage.do
Kit Location:
http://www.itrc.hp.com/service/patch/patchDetail.do?patchid=DUXKIT0024523-V40FB22-ES-20041219
BULLETIN REVISION HISTORY:
    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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REPORT: To report a potential security vulnerability with any HP supported product, 
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System management and security procedures must be reviewed frequently to maintain 
system integrity. HP is continually reviewing and enhancing the security features of 
software products 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 
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©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 
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