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SGI Security Advisory 19970502-02-PX - xlock Vulnerability
From: agent99 () BOYTOY CSD SGI COM (SGI Security Coordinator)
Date: Tue, 8 Jul 1997 07:56:26 -0700


DISTRIBUTION RESTRICTIONS  -   NONE   -    FOR PUBLIC RELEASE



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

______________________________________________________________________________
                Silicon Graphics Inc. Security Advisory

        Title:   xlock Vulnerability
        Number:  19970502-02-PX
        Date:    July 7, 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 xlock(1) program is used to lock the local X display of a system
until a correct password is entered at the keyboard.  The program is
setuid root and as part of the process of locking an X display accepts
user arguments to establish specific xlock operation.

It has been determined that an appropriately crafted set of arguments
could be input to the xlock program allowing execution of arbitrary
user commands with root privileges.   This resulting buffer overflow
condition is considered a security vulnerability in the xlock program.

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 xlock program (/usr/bin/X11/xlock) is installed on all IRIX systems
by default.

A local account is required in order to exploit this vulnerability both
locally and remotely.

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

This vulnerability has been publically discussed and reported in
CERT advisory CA-97.13 and AUSCERT advisory AA-97.24.



- --------------------------
- --- 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 removing
the permissions of the xlock program.



     1) Become the root user on the system.

                % /bin/su -
                Password:
                #

     2) Change the permissions on the xlock program.


                # /bin/chmod 500 /usr/bin/X11/xlock


                           ************
                           *** NOTE ***
                           ************

               Removing the setuid root permissions from the xlock
               program will prevent non-root users from using the xlock
               to lock their terminal.

     3) Return to previous level.

                # exit
                $



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



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

   IRIX 3.x          no
   IRIX 4.x          no
   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          2090
   IRIX 6.0.x        yes          not avail    Note 1
   IRIX 6.1          yes          not avail    Note 1
   IRIX 6.2          yes          2090
   IRIX 6.3          yes          2090
   IRIX 6.4          yes          2091


   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.2090
Algorithm #1 (sum -r):    50124 8 README.patch.2090
Algorithm #2 (sum):       49453 8 README.patch.2090
MD5 checksum:             4D51EA09250113215760C045BE8F5E14

Filename:                 patchSG0002090
Algorithm #1 (sum -r):    49562 1 patchSG0002090
Algorithm #2 (sum):       25201 1 patchSG0002090
MD5 checksum:             99F72D8E24773A63306A0118F56411E7

Filename:                 patchSG0002090.idb
Algorithm #1 (sum -r):    47573 1 patchSG0002090.idb
Algorithm #2 (sum):       35831 1 patchSG0002090.idb
MD5 checksum:             9E16916C33EA81D2C090A9162FB7B099

Filename:                 patchSG0002090.x_eoe_sw
Algorithm #1 (sum -r):    40887 114 patchSG0002090.x_eoe_sw
Algorithm #2 (sum):       62640 114 patchSG0002090.x_eoe_sw
MD5 checksum:             7088ECF05104E049DCC1D5150EE41F8C



Filename:                 README.patch.2091
Algorithm #1 (sum -r):    08547 8 README.patch.2091
Algorithm #2 (sum):       35395 8 README.patch.2091
MD5 checksum:             54836F64E12DDBAE09E1F165B42A7B01

Filename:                 patchSG0002091
Algorithm #1 (sum -r):    50655 1 patchSG0002091
Algorithm #2 (sum):       27369 1 patchSG0002091
MD5 checksum:             857AE0806FE273DB75F99264873828FD

Filename:                 patchSG0002091.idb
Algorithm #1 (sum -r):    07183 1 patchSG0002091.idb
Algorithm #2 (sum):       35505 1 patchSG0002091.idb
MD5 checksum:             134D7A6DC774425B6CC73A84A9468833

Filename:                 patchSG0002091.x_eoe_sw
Algorithm #1 (sum -r):    23378 102 patchSG0002091.x_eoe_sw
Algorithm #2 (sum):       26001 102 patchSG0002091.x_eoe_sw
MD5 checksum:             1FF45DAC2F7FDCCAB8A982ED77554DDA




- ------------------------
- --- 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/Secur/security.html.

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/Secur/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/Secur/security.html.

                      ------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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