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SGI Security Advisory 19970701-01-PX - talkd Vulnerability
From: agent99 () BOYTOY CSD SGI COM (SGI Security Coordinator)
Date: Wed, 23 Jul 1997 14:13:58 -0700


DISTRIBUTION RESTRICTIONS  -  NONE   -   FOR PUBLIC RELEASE


-----BEGIN PGP SIGNED MESSAGE-----

______________________________________________________________________________
                Silicon Graphics Inc. Security Advisory

        Title:   talkd Vulnerability
        Number:  19970701-01-PX
        Date:    July 23, 1997
______________________________________________________________________________

Silicon Graphics provides this information freely to the SGI user community
for its consideration, interpretation, implementation and use.   Silicon
Graphics recommends that this information be acted upon as soon as possible.

Silicon Graphics provides the information in this Security Advisory on
an "AS-IS" basis only, and disclaims all warranties with respect thereto,
express, implied or otherwise, including, without limitation, any warranty
of merchantability or fitness for a particular purpose.  In no event shall
Silicon Graphics be liable for any loss of profits, loss of business, loss
of data or for any indirect, special, exemplary, incidental or consequential
damages of any kind arising from your use of, failure to use or improper
use of any of the instructions or information in this Security Advisory.
______________________________________________________________________________

- -----------------------
- --- Issue Specifics ---
- -----------------------

The talkd(8) program is a support program for the user to user communications
program talk(1).   As part of the start of talk communications between
two users, the talkd program obtains network hostname information from
DNS and then coordinates notifying users of a requested talk session.

A security vulnerability has been discovered in which manipulation of
provided network hostname information to the talkd program can be used
to execute arbitrary commands with root privileges.

Silicon Graphics Inc. has investigated the issue and recommends the
following steps for neutralizing the exposure.  It is HIGHLY RECOMMENDED
that these measures be implemented on ALL SGI systems.  This issue will
be corrected in future releases of IRIX.


- --------------
- --- Impact ---
- --------------

The talkd program (/usr/etc/talkd) is installed on all IRIX systems by
default.

For this particular vulnerability, a local account is not required.
Furthermore, the vulnerability can be exploited remotely.

This vulnerability can be utilized to execute commands with root
privileges.

This vulnerability has been public-ally discussed and reported in
AUSCERT advisory AA-97.01 and CERT advisory CA-97.04.



- --------------------------
- --- Temporary Solution ---
- --------------------------

Although patches are available for this issue, it is realized that
there may be situations where installing the patches immediately may
not be possible.

The steps below can be used to remove the vulnerability by disabling
the talkd program.




     1) Become the root user on the system.

                % /bin/su -
                Password:
                #

     2) Edit the file /etc/inetd.conf . Place a "#" as
     the first character of the talkd line to comment out
     and deactivate the service.


                # vi  /usr/etc/inetd.conf

        {Find the following line}

             ntalk  dgram  udp   wait   root  /usr/etc/talkd       talkd

        {Place a "#" as the first character of the ntalk line}

             #ntalk  dgram  udp   wait   root  /usr/etc/talkd       talkd

        {Save the file and exit}


     3) Force inetd to re-read the configuration file.

                # /etc/killall -HUP inetd


     4) Return to previous level.

                # exit
                $




- ----------------
- --- Solution ---
- ----------------



   OS Version     Vulnerable?     Patch #      Other Actions
   ----------     -----------     -------      -------------

   IRIX 3.x          yes          not avail    Note 1
   IRIX 4.x          yes          not avail    Note 1
   IRIX 5.0.x        yes          not avail    Note 1
   IRIX 5.1.x        yes          not avail    Note 1
   IRIX 5.2          yes          not avail    Note 1
   IRIX 5.3          yes          2132
   IRIX 6.0.x        yes          not avail    Note 1
   IRIX 6.1          yes          not avail    Note 1
   IRIX 6.2          yes          2133
   IRIX 6.3          yes          2133
   IRIX 6.4          yes          2133


   NOTES

     1) upgrade operating system or see "Temporary Solution" section.

Patches are available via anonymous FTP and your service/support provider.

The SGI anonymous FTP site is sgigate.sgi.com (204.94.209.1) or its
mirror, ftp.sgi.com.   Security information and patches can be found
in the ~ftp/security and ~ftp/patches directories, respectfully.



                 ##### Patch File Checksums ####

The actual patch will be a tar file containing the following files:



Filename:                 README.patch.2132
Algorithm #1 (sum -r):    58795 8 README.patch.2132
Algorithm #2 (sum):       22126 8 README.patch.2132
MD5 checksum:             1C16F01A682CC8DB605DEC4C515B3ADD

Filename:                 patchSG0002132
Algorithm #1 (sum -r):    39922 1 patchSG0002132
Algorithm #2 (sum):       24988 1 patchSG0002132
MD5 checksum:             1BD1683D23D164F954BEE893B3CF8B2F

Filename:                 patchSG0002132.eoe2_sw
Algorithm #1 (sum -r):    29839 26 patchSG0002132.eoe2_sw
Algorithm #2 (sum):       636 26 patchSG0002132.eoe2_sw
MD5 checksum:             EDB8C15F7D22F7104770D591952346E7

Filename:                 patchSG0002132.idb
Algorithm #1 (sum -r):    54227 1 patchSG0002132.idb
Algorithm #2 (sum):       34895 1 patchSG0002132.idb
MD5 checksum:             82E411637E20CB15E9EEFA3BA330F93D



Filename:                 README.patch.2133
Algorithm #1 (sum -r):    53634 8 README.patch.2133
Algorithm #2 (sum):       26859 8 README.patch.2133
MD5 checksum:             20FE236BEAC79EC8614BE84B5E291841

Filename:                 patchSG0002133
Algorithm #1 (sum -r):    05188 1 patchSG0002133
Algorithm #2 (sum):       27188 1 patchSG0002133
MD5 checksum:             A4E881E9682DA41DE8897DE71D2EE42C

Filename:                 patchSG0002133.eoe_sw
Algorithm #1 (sum -r):    24652 27 patchSG0002133.eoe_sw
Algorithm #2 (sum):       6068 27 patchSG0002133.eoe_sw
MD5 checksum:             7ECC472AFE5105D195BCC2B75834D666

Filename:                 patchSG0002133.idb
Algorithm #1 (sum -r):    45369 1 patchSG0002133.idb
Algorithm #2 (sum):       35211 1 patchSG0002133.idb
MD5 checksum:             5BE2481FB3F325399BEE961AF0FB476C



- ------------------------
- --- Acknowledgments ---
- ------------------------

Silicon Graphics Inc. wishes to thank the CERT Coordination Center
and AUSCERT for their assistance in this issue.



- -----------------------------------------------------------
- --- Silicon Graphics Inc. Security Information/Contacts ---
- -----------------------------------------------------------

If there are questions about this document, email can be sent to
cse-security-alert () sgi com 

                      ------oOo------

Silicon Graphics provides security information and patches for
use by the entire SGI community.  This information is freely
available to any person needing the information and is available
via anonymous FTP and the Web.

The primary SGI anonymous FTP site for security information and patches
is sgigate.sgi.com (204.94.209.1).  Security information and patches
are located under the directories ~ftp/security and ~ftp/patches,
respectively. The Silicon Graphics Security Headquarters Web page is
accessible at the URL http://www.sgi.com/Support/security.

For issues with the patches on the FTP sites, email can be sent to
cse-security-alert () sgi com 

For assistance obtaining or working with security patches, please
contact your SGI support provider.

                      ------oOo------

Silicon Graphics provides a free security mailing list service
called wiretap and encourages interested parties to self-subscribe
to receive (via email) all SGI Security Advisories when they are
released. Subscribing to the mailing list can be done via the Web
(http://www.sgi.com/Support/security/wiretap.html) or by sending email
to SGI as outlined below.

% mail wiretap-request () sgi com
subscribe wiretap <YourEmailAddress>
end
^d

In the example above, <YourEmailAddress> is the email address that you
wish the mailing list information sent to.  The word end must be on a
separate line to indicate the end of the body of the message. The
control-d (^d) is used to indicate to the mail program that you are
finished composing the mail message.


                      ------oOo------

Silicon Graphics provides a comprehensive customer World Wide Web site.
This site is located at http://www.sgi.com/Support/security.

                      ------oOo------

For reporting *NEW* SGI security issues, email can be sent to
security-alert () sgi com or contact your SGI support provider.  A
support contract is not required for submitting a security report.

______________________________________________________________________________
  This information is provided freely to all interested parties and may
  be redistributed provided that it is not altered in any way, Silicon
  Graphics is appropriately credited and the document retains and
  includes its valid PGP signature.


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