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suid_exec Buffer Overflow
From: agent99 () BOYTOY CSD SGI COM (SGI Security Coordinator)
Date: Mon, 6 Apr 1998 15:10:23 -0700


DISTRIBUTION RESTRICTIONS - NONE - FOR PUBLIC RELEASE

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

______________________________________________________________________________
                Silicon Graphics Inc. Security Advisory

        Title:   suid_exec Buffer Overflow
        Title:   AUSCERT AA-96.17
        Number:  19980405-01-I
        Date:    April 6, 1998
______________________________________________________________________________

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 suid_exec program is part of the Korn Shell (ksh) software distributions.

Under normal operation, the suid_exec program will run shell scripts
setuid.  Unfortunately, a buffer overrun has been discovered in the
suid_exec program which could allow arbitrary commands to be run as the
privileged user root.

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 vulnerable SGI systems.


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

The suid_exec program is installed by default on all IRIX 5.x and 6.x
systems.

With a local account, the suid_exec buffer overrun vulnerability can be
exploited locally and remotely.

The suid_exec buffer overrun vulnerability can be utilized to execute
commands with root privileges.

The suid_exec buffer overrun vulnerability has been publicly discussed
in Usenet newsgroups and mailing lists and also reported in AUSCERT
Security Advisory AA-96.17.


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

To disable the programs that are believed to be vulnerable, use the
following steps.


     1) Become the root user on the system.


                % /bin/su -
                Password:
                #


     2) Change the setuid root permissions on the program.

                # /bin/chmod 400 /sbin/suid_exec

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

               Removing these permissions from suid_exec will stop
               non-root users from executing setuid/setgid shell
               scripts and scripts upon which read permissions have
               not been set.


     3) Confirm the new permissions on the program.

                # ls -la /sbin/suid_exec
                -r--------   1 root sys    14384 May 30 1996 /sbin/suid_exec


     4) Using the find command, locate any additional copies of suid_exec
        and disable them.

        Note that this is one long command, though we have separated it
        onto two lines using backslashes.

                # find / -local -type f -name suid_exec \
                  -print -ok chmod 400 '{}' \;

        This command will find all files on a system that are
        - only in the local file system you name (/ -local)
        - regular files (-type f)
        - named appropriately (-name suid_exec)

        Once found, those files will
        - have their names printed (-print)
        - have their modes changed, but only if you type `y' in response
          to the prompt (-ok chmod 400 '{}' \;)

     5) Return to previous level.

                # exit
                $


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

The suid_exec program is considered freeware and will not be patched.
As freeware software, all reasonable efforts will be made to address
the issue in future versions of the software.


   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          not avail    Note 1
   IRIX 6.0.x        yes          not avail    Note 1
   IRIX 6.1          yes          not avail    Note 1
   IRIX 6.2          yes          not avail    Note 1
   IRIX 6.3          yes          not avail    Note 1
   IRIX 6.4          yes          not avail    Note 1


Notes:

1) Freeware upgrades should be applied.


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

Silicon Graphics wishes to thank AUSCERT for their assistance in
this matter.


- -----------------------------------------------------------
- --- 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/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/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/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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