IBM-ERS Security Vulnerability Alert: IBM AIX: automountd daemon

[ibm-ers () ERS IBM COM (ibm-ers () ERS IBM COM)]

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                           EMERGENCY RESPONSE SERVICE
                          SECURITY VULNERABILITY ALERT

26 October 1998 14:00 GMT                        Number: ERS-SVA-E01-1998:004.1
===============================================================================
                             VULNERABILITY  SUMMARY

VULNERABILITY:    The automountd daemon allows local and remote users to become
                  root.

PLATFORMS:        IBM AIX(r) 4.3.x

SOLUTION:         Apply the fixes listed below.

THREAT:           Remote users can execute arbitrary commands as root.

===============================================================================
                              DETAILED INFORMATION

I.  Description

The automountd daemon processes requests from the local AutoFS filesystem
kernel extension.  It uses local files or name service maps to locate file
systems to be mounted.  Because the daemon does not verify that requests
are actually from the kernel extension, local non-root users and remote
users can request automountd services.

II.  Impact

If the automountd daemon is active, local and remote users can cause
arbitrary commands to run as root.  Exploits for this problem have been
made publicly available.

To determine if the daemon is active on your system, run the following
command:

   $ lssrc -s automountd

To disable the daemon until the fix can be applied (run as root):

   # stopsrc -s automountd


III.  Solutions

  A.  Official fix

    IBM is working on the following fixes which will be available soon.

       AIX 4.1.x:  not vulnerable
       AIX 4.2.x:  not vulnerable
       AIX 4.3.x:  IX83752

  B.  How to alleviate the problem

    A temporary fix is available via anonymous ftp from:

       ftp://aix.software.ibm.com/aix/efixes/security/automountd.tar.Z

    Filename          sum             md5
    ==================================================================
    autofs.ext        26103   117     4afedf8fbe411e8be2588fa8843211ae
    automountd        16386    83     eb4c2e1c4cfe609b2ecba0c6a704640c

    NOTE - This temporary fix has not been fully regression tested.

    Use the following steps (as root) to install the temporary fix:

    1.  Determine the version of the NFS fileset on your machine.

      # lslpp -l bos.net.nfs.client

        The version of the fileset for your machine should be at 4.3.1.4
        or higher.  If not, install requisite APAR IX81896.  This will
        help ensure that the temporary fix will run properly.

    2. Uncompress and extract the fix.

      # uncompress < automountd.tar.Z | tar xf -
      # cd automountd

    3. Replace the vulnerable executables with the temporary fix.

      # (cd /usr/lib/drivers && mv autofs.ext autofs.ext.before_security_fix)
      # (cd /usr/sbin && mv automountd automountd.before_security_fix)
      # chmod 0 /usr/lib/drivers/autofs.ext.before_security_fix
      # chmod 0 /usr/sbin/automountd.before_security_fix
      # cp ./autofs.ext /usr/lib/drivers/autofs.ext
      # cp ./automountd /usr/sbin/automountd
      # chown root.system /usr/sbin/automountd /usr/lib/drivers/autofs.ext
      # chmod 555 /usr/sbin/automountd /usr/lib/drivers/autofs.ext

    4. Reboot.


IV. Obtaining Fixes

IBM AIX APARs may be ordered using Electronic Fix Distribution (via the
FixDist program), or from the IBM Support Center.  For more information
on FixDist, and to obtain fixes via the Internet, please reference

        http://aix.software.ibm.com/support/rs6000

or send email to "aixserv () austin ibm com" with the word "FixDist" in the
"Subject:" line.

To facilitate ease of ordering all security related APARs for each AIX
release, security fixes are periodically bundled into a cumulative APAR.
For more information on these cumulative APARs including last update and
list of individual fixes, send email to "aixserv () austin ibm com" with
the word "subscribe Security_APARs" in the "Subject:" line.


V.  Acknowledgements

Thanks to Repent Security Incorporated for bringing this problem to
our attention.  A copy of their autofsd advisory can be found at
http://www.repsec.com/.


VI.  Contact Information

Comments regarding the content of this announcement can be directed to
your local IBM support center or to:

   security-alert () austin ibm com

To request the PGP public key that can be used to encrypt new AIX
security vulnerabilities, send email to security-alert () austin ibm com
with a subject of "get key".

If you would like to subscribe to the AIX security newsletter, send a
note to aixserv () austin ibm com with a subject of "subscribe Security".
To cancel your subscription, use a subject of "unsubscribe Security".
To see a list of other available subscriptions, use a subject of
"help".

IBM and AIX are a registered trademark of International Business
Machines Corporation.  All other trademarks are property of their
respective holders.

===============================================================================

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Copyright 1998 International Business Machines Corporation.

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