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TUCoPS :: Unix :: General :: ciach54a.txt

Vulnerability In Xlock



                       The U.S. Department of Energy
                    Computer Incident Advisory Capability
                           ___  __ __    _     ___
                          /       |     /_\   /
                          \___  __|__  /   \  \___

                             INFORMATION BULLETIN

                             Vulnerability in xlock

November 6, 1997 17:00 GMT                                        Number H-54a
PROBLEM:       A buffer overflow condition exists in some implementations of
PLATFORM:      See "Appendix A - Vendor Information" below for platforms
DAMAGE:        Local users may gain root privileges.
SOLUTION:      If your system is vulnerable, install vendor patches or apply
               the workaround described in Section III.B.
VULNERABILITY  Exploit details involving this vulnerability have been made
ASSESSMENT:    publicly available.

[ Appended to H-54 on November 6, 1997 with patch release information from
Hewlett-Packard ]

[ Start CERT Advisory ]

CERT* Advisory CA-97.13
Original issue date: May 7, 1997
Last revised: --
Topic: Vulnerability in xlock
- ------------------------------------------------------------------------------

The CERT Coordination Center has received reports that a buffer overflow
condition exists in some implementations of xlock. This vulnerability makes it
possible for local users (users with access to an account on the system) to
execute arbitrary programs as a privileged user.

Exploitation information involving this vulnerability has been made publicly

If your system is vulnerable, the CERT/CC team recommends installing a
patch from your vendor. If you are not certain whether your system is
vulnerable or if you know that your system is vulnerable and you cannot add a
patch immediately, we urge you to apply the workaround described in
Section III.B.

We will update this advisory as we receive additional information.
Please check our advisory files regularly for updates that relate to your

- ------------------------------------------------------------------------------

I.   Description

     xlock is a program that allows a user to "lock" an X terminal. A buffer
     overflow condition exists in some implementations of xlock. It is
     possible attain unauthorized access to a system by engineering a
     particular environment and calling a vulnerable version of xlock that has
     setuid or setgid bits set. Information about vulnerable versions must be
     obtained from vendors. Some vendor information can be found in Appendix A
     of this advisory.

     Exploitation information involving this vulnerability has been made
     publicly available.

     Note that this problem is different from that discussed in CERT Advisory

II.  Impact

     Local users are able to execute arbitrary programs as a privileged user
     without authorization.

III. Solution

     Install a patch from your vendor as described in Solution A. If you are
     not certain whether your system is vulnerable or if you know that your
     system is vulnerable and you cannot install a patch immediately, we
     recommend Solution B.

     A.  Obtain and install a patch for this problem.

         Below is a list of vendors who have provided information about
         xlock. Details are in Appendix A of this advisory; we will
         update the appendix as we receive more information. If your
         vendor's name is not on this list, the CERT/CC did not hear from
         that vendor. Please contact your vendor directly.

         Berkeley Software Design, Inc. (BSDI)
         Cray Research - A Silicon Graphics Company
         Data General Corporation
         Digital Equipment Corporation
         FreeBSD, Inc.
         Hewlett-Packard Company
         IBM Corporation
         NEC Corporation
         The Open Group [This group distributes the publicly available
                         that was formerly distributed by X Consortium]
         Sun Microsystems, Inc.

     B.  We recommend the following workaround if you are not certain
         whether your system is vulnerable or if you know that your system
         is vulnerable and you cannot install a patch immediately.

         1. Find and disable any copies of xlock that exist on your system and
            that have the setuid or setgid bits set.

         2. Install a version of xlock known to be immune to this
            vulnerablility. One such supported tool is xlockmore. The latest
            version of this tool is 4.02, and you should ensure that this is
            the version you are using. This utility can be obtained from the
            following site:

               MD5 (xlockmore-4.02.tar.gz) = c158e6b4b99b3cff4b52b39219dbfe0e

            You can also obtain this version from mirror sites. A list of
            these sites will be displayed if you are not able to access the
            above archive due to load.


Appendix A - Vendor Information

Below is a list of the vendors who have provided information for this
advisory. We will update this appendix as we receive additional information.
If you do not see your vendor's name, the CERT/CC did not hear from that
vendor. Please contact the vendor directly.

Berkeley Software Design, Inc. (BSDI)
BSD/OS is not vulnerable to the problem in xlock since our
xlock is not setuid.

Cray Research - A Silicon Graphics Company
Cray Research does not include xlock in its X Window releases, so we are
not at risk on the xlock buffer overflow problem.

Data General Corporation
The xlock sources (xlockmore-3.7) that DG includes in its contributed
software package have been modified to remove this vulnerability. These
will be available when release 8 comes out. We also recommend that our
customers who have the current version should change the sprintf calls in
resource.c to snprintf calls, rebuild and reinstall the package.

Digital Equipment Corporation
This reported problem is not present for Digital's ULTRIX or
Digital UNIX Operating Systems Software.

FreeBSD, Inc.
The xlockmore version we ship in our ports collection is vulnerable
in all shipped releases. The port in FreeBSD-current is fixed.
Solution is to install the latest xlockmore version (4.02).

Hewlett-Packard Company
We ship an suid root program vuelock that is based on xlock.
It does have the vulnerability.

The only workaround is to remove the executable, the patch is "in process".

IBM Corporation
AIX is vulnerable to the conditions described in this advisory.
The following APARs will be released soon:

     AIX 3.2:  APAR IX68189
     AIX 4.1:  APAR IX68190
     AIX 4.2:  APAR IX68191

IBM and AIX are registered trademarks of International Business Machines

Red Hat:
        Not vulnerable

        Not vulnerable

        An updated package is on the Debian site


And in general the new Xlockmore release fixes the problems.

NEC Corporation
UX/4800              Not vulnerable for all versions.
EWS-UX/V(Rel4.2MP)   Not vulnerable for all versions.
EWS-UX/V(Rel4.2)     Not vulnerable for all versions.
UP-UX/V(Rel4.2MP)    Not vulnerable for all versions.

The Open Group
Publicly available software that was formerly distributed by the X Consortium
- -

Not vulnerable.

Solbourne is not vulnerable to this attack.

Sun Microsystems, Inc.
We are producing patches for OpenWindows 3.0 for Sun OS versions
4.1.3_U1, 4.1.4, 5.3, 5.4, 5.5, and 5.5.1.

[ End CERT Advisory ]

[ Start Hewlett-Packard Advisory ]

Document ID:  HPSBUX9711-073
Date Loaded:  971105
      Title:  Security Vulnerability in xlock on VVOS, HP-UX 10.24

- -------------------------------------------------------------------------
         HEWLETT-PACKARD SECURITY BULLETIN: #00073, 4 November 1997
- -------------------------------------------------------------------------

The information in the following Security Bulletin should be acted upon
as soon as possible.  Hewlett-Packard will not be liable for any
consequences to any customer resulting from customer's failure to fully
implement instructions in this Security Bulletin as soon as possible.

- -------------------------------------------------------------------------
PROBLEM:  Vulnerabilities exist in xlock on VirtualVault 2.0/3.0 if patch
          PHSS_9905 is installed.

PLATFORM: HP9000 Series 700/800s running:
          HP-UX 10.24 (VVOS) with VirtualVault A.02.00 with patch PHSS_9905.
          HP-UX 10.24 (VVOS) with VirtualVault A.03.00 with Extensions
          Software (this includes PHSS_9905)

DAMAGE:   The xlock vulnerability could result in allowing a local user
          to gain unauthorized access to the system.

SOLUTION:  Apply PHSS_12961 to correct the vulnerability.

AVAILABILITY: The patch is available now.

   A. Background
      The xlock program allows a user to "lock" an X terminal while
      maintaining their login session.  A vulnerability exists in xlock
      that could allow a local user to attain unauthorized access to the

   B. Fixing the problem
      This problem can be eliminated by applying the recommended patch.

   C. Recommended solution
      Hewlett-Packard recommends that the PHSS_12961 patch be applied if
      PHSS_9905 has already been installed.  The PHSS_9905 patch is
      included in the Software Extension Media provided with VirtualVault

        These problems only apply to systems running the VirtualVault
        Operating System 10.24 that is part of the VirtualVault product
        A.02.00 and A.03.00.

   D. Impact of the patch
      Applying PHSS_12961 eliminates the vulnerability in the xlock
      program but does not otherwise impact the system.

   E. To subscribe to automatically receive future NEW HP Security
      Bulletins from the HP Electronic Support Center via electronic mail,
      do the following:

      Use your browser to get to the HP Electronic Support Center page at:
   (for US, Canada, Asia-Pacific, & Latin-America)
   (for Europe)

   Click on the Technical Knowledge Database, register as a user
   (remember to save the User ID assigned to you, and your password),
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   F. To report new security vulnerabilities, send email to

      Please encrypt any exploit information using the security-alert
      PGP key, available from your local key server, or by sending a
      message with a -subject- (not body) of 'get key' (no quotes) to

     Permission is granted for copying and circulating this Bulletin to
     Hewlett-Packard (HP) customers (or the Internet community) for the
     purpose of alerting them to problems, if and only if, the Bulletin is
     not edited or changed in any way, is attributed to HP, and provided
     such reproduction and/or distribution is performed for non-commercial

     Any other use of this information is prohibited. HP is not liable
     for any misuse of this information by any third party.
- -----End of Document ID:  HPSBUX9711-073--------------------------------------

[ End Hewlett-Packard Advisory ]


CIAC wishes to acknowledge the contributions of CERT, David Hedley, Kaleb
Keithley and Hewlett-Packard for the information contained in this bulletin.

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