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HP SECURITY BULLETIN

HPSBUX01137     REVISION: 4

SSRT5954 rev.4 - HP-UX TCP/IP Remote Denial of Service (DoS)

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

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

INITIAL RELEASE:
10 July 2005

POTENTIAL SECURITY IMPACT:
Remote Denial of Service (DoS)

SOURCE:
Hewlett-Packard Company
HP Software Security Response Team

VULNERABILITY SUMMARY:
A potential security vulnerability has been identified with HP-UX
running TCP/IP (IPv4). This vulnerability could be remotely
exploited by an unauthorized user to cause a Denial of Service
(DoS).

REFERENCES:
CAN-2005-1192

SUPPORTED SOFTWARE VERSIONS*:  ONLY impacted versions are listed.
HP-UX B.11.11, B.11.22, B.11.23.

BACKGROUND:

     AFFECTED VERSIONS

     Note: To determine if a system has an affected version,
           search the output of "swlist -a revision -l fileset"
           for an affected fileset.  Then determine if the
           recommended patch or update is installed.


     HP-UX B.11.22
     =============
     Networking.NET2-KRN
     action: install preliminary binary files per HPSBUX01164 OR
             set ip_pmtu_strategy=0 or 3

     HP-UX B.11.11
     =============
     Networking.NET2-KRN
     action: install PHNE_33159 OR set ip_pmtu_strategy=0 or 3

     HP-UX B.11.23
     =============
     Networking.NET2-KRN
    ->action: install PHNE_32606 OR set ip_pmtu_strategy=0 or 3

     HP-UX B.11.23
     HP-UX B.11.11
     =============
     IPSec.IPSEC2-KRN
     action: set ip_pmtu_strategy=0 or 3

     END AFFECTED VERSIONS

 ->Note: Setting ip_pmtu_strategy=0 is preferred.  Please refer to
         HPSBUX01164 for more information.

Certain network traffic can result in a Denial of Service (DoS)
for HP-UX systems running TCP/IP (IPv4).  Receiving a certain
packet on any open TCP/IP connection can result in a Denial of
Service (DoS) condition which can only be corrected by a reboot of
the affected system.
 ->The Denial of Service (DoS) is characterized by high cpu
utilization and a lack of response on any I/O port including the
system console.

Until patches are available to resolve the issue the Denial of
Service (DoS) can be avoided by setting the ip_pmtu_strategy
parameter to either 0 or 3.

 Discussion of ip_pmtu_strategy
 ----------------------------------

The default value for ip_pmtu_strategy is 1.  This allows for PMTU
discovery.  Once the issue of this Security Bulletin has been
resolved via patches the ip_pmtu_strategy value of 1 will again be
the preferred setting for most situations.

The ip_pmtu_strategy values of 0 and 3 set the PMTU to a fixed
size for destinations which are not on the local network.

The  ip_pmtu_strategy value of 0 sets the PMTU to 576 bytes.
Routers are required to handle packets of at least this size.

The ip_pmtu_strategy value of 3 sets the PMTU to 1500 bytes.  This
will generally result in more efficient transmission than the 576
byte PMTU.  If it is known that the routers  involved can handle a
1500 byte MTU the ip_pmtu_strategy value of 3 is preferred.

 Patch requirements for setting ip_pmtu_strategy to 3
 ----------------------------------------------------------

All affected HP-UX versions allow setting ip_pmtu_strategy to 0.

B.11.22 and B.11.23 have no patch requirements for
setting ip_pmtu_strategy to 3.

 ->B.11.11 requires PHNE_25642 or subsequent in order to set
ip_pmtu_strategy to 3.


 Reboot requirement for setting ip_pmtu_strategy
 ------------------------------------------------------

 ->Any existing connection presents the potential for a Denial of
Service (DoS).  Because of this it is recommended that the
/etc/rc.config.d/nddconf  be modified as discussed below and the
system be rebooted.

Note:
It has been recommended in several places including HP-UX
Bastille, System Health Check, and the Security Bulletin
HPSBUX0001-110 that ip_pmtu_strategy be set to 1.   This
recommendation was made to avoid issues with which
occurred when ip_pmtu_strategy was set to 2.  The value 1
was recommended because it is the system default and
for most situations results in the best performance.  However,
the values 0 and 3 also avoid the issues which occurred when
ip_pmtu_strategy was set to 2.  As mentioned above once the
issue of this Security Bulletin has been resolved via patches the
ip_pmtu_strategy setting of 1 will again be the preferred setting
for most situations.

Note:
There is a defect that will cause "ndd -c" to fail if there are
more than 10 directives in /etc/rc.config.d/nddconf.  That defect
is fixed in the following patch:

   B.11.11 - PHNE_25644 or subsequent

RESOLUTION:
Until patches are available the Denial of Service (DoS) can be
avoided by setting the ip_pmtu_strategy parameter to 0 or 3.

 ->Note: The preliminary binary files cited in HPSBUX01164 will
resolve the issue of this Security Bulletin as well for the core
TCP/IP product.   If the IPSec product is installed in B11.11 or
B.11.23 it will still be necessary to work around the issue of
this Security Bulletin by setting ip_pmtu_strategy=0 or 3.

If the ip_pmtu_strategy value of 3 is desired for B.11.11 apply
the patch listed in the Background section.

Edit /etc/rc.config.d/nddconf to add the following:

TRANSPORT_NAME[n]=ip
NDD_NAME[n]=ip_pmtu_strategy
NDD_VALUE[n]=0

or

TRANSPORT_NAME[n]=ip
NDD_NAME[n]=ip_pmtu_strategy
NDD_VALUE[n]=3

where 'n' is the next available index value as described in the
nddconf comments.

This value will take effect when the system is rebooted.
Until the system can be rebooted use the following command
to read the /etc/rc.config.d/nddconf file and set the tunable
parameters:

  /usr/bin/ndd -c

The ip_pmtu_strategy parameter can be displayed by the following
command:

  /usr/bin/ndd -get /dev/ip ip_pmtu_strategy

 ->Note: Since open connections will remain potentially vulnerable
until they are closed and certain internal data structures are
released it is recommended that the system be rebooted.



MANUAL ACTIONS:  Yes - NonUpdate
B.11.11, B.11.22, B.11.23
set ip_pmtu_strategy = 0 or 3

 ->The binary files  and patches cited in the HPSBUX01164 Security
Bulletin will resolve the issue of this Security Bulletin as well
for the core TCP/IP product.

 ->B11.11, B.11.23 running IPSec
 ->set ip_pmtu_strategy = 0 or 3

 ->The binary files and patches cited in the HPSBUX01164 Security
Bulletin will NOT resolve the issue of this Security Bulletin in
the case of the IPSec product.

BULLETIN REVISION HISTORY:
Revision 0: 24 April 2005
  Initial release

Revision 1: 25 May 2005
  The binary files of HPSBUX01164 will resolve the issue for
  B.11.11 and B.11.23.

Revision 2: 1 June 2005
   The binary files of HPSBUX01164 will resolve the issue for the
   core TCP/IP in B.11.11, B.11.22, and B.11.23.
   The binary files of HPSBUX01164 will resolve NOT resolve the
   issue for IPSec.
   B.11.00 and B.11.04 are NOT vulnerable.
   The recommended workaround is to modify
   /etc/rc.config.d/nddconf and reboot.

Revision 3: 27 June 2005
    PHNE_33159 is available for B.11.11.

Revision 4: 10 July 2005
    PHNE_32606 is available for B.11.23.



HP-UX SPECIFIC SECURITY BULLETINS*:  Security Patch Check revision
B.02.00 analyzes all HP-issued Security Bulletins to provide a
subset of recommended actions that potentially affect a specific
HP-UX system.

For more information:
http://www.software.hp.com/cgi-bin/swdepot_parser.cgi/cgi/
displayProductInfo.pl?productNumber=B6834AA


SUPPORT: For further information, contact normal HP Services
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* The Software Product Category that this Security Bulletin
  relates to is represented by the 5th and 6th characters of the
  Bulletin number:
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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 warrant that this information is necessarily
accurate or complete for all user situations and, consequently, HP
will not be responsible for any damages resulting from user's use
or disregard of the information provided in this Bulletin. To the
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(c)Copyright 2005 Hewlett-Packard Development Company, L.P.
Hewlett-Packard Company shall not be liable for technical or
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provided is provided "as is" without warranty of any kind. To the
extent permitted by law, neither HP nor its affiliates,
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or consequential damages including downtime cost; lost profits;
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