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         SUN MICROSYSTEMS SECURITY BULLETIN: #00131, 14 September 1995
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BULLETIN TOPICS


In this bulletin Sun summarizes the availability of a new set of
security patches for Solaris 2.x (SunOS 5.x) systems. The patches close
the so-called "ps_data" vulnerability.

This bug does not affect SunOS 4.1.x systems. Additionally, not all
Solaris 2.x systems are affected. We discuss later in this bulletin how
to determine if your configuration is vulnerable.

This is the same bug that was discussed in CERT bulletin CA-95:09
(released 29 August 1995) and AUSCERT advisory AA-95.07 (released 15
August 95). We have quoted extensively from those two bulletins and
wish to thank both groups for their cooperation.

 
I.   Vulnerability history and analysis

II.  Announcement of patches for Solaris 2.x "ps_data" vulnerability

III. Checksum Table


APPENDICES

A.  How to obtain Sun security patches

B.  How to report or inquire about Sun security problems

C.  How to obtain Sun security bulletins




          /\         Send Replies or Inquiries To:
         \\ \        
        \ \\ /       Mark Graff
       / \/ / /      Sun Security Coordinator
      / /   \//\     MS MPK3
      \//\   / /     2550 Garcia Avenue
       / / /\ /      Mountain View, CA 94043-1100
        / \\ \       Phone: 415-688-9081
         \ \\        Fax:   415-688-9101
          \/         E-mail: security-alert@Sun.COM
 
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Permission is granted for the redistribution of this Bulletin for
the purpose of alerting Sun customers to problems, as long as the
Bulletin is not edited and is attributed to Sun Microsystems.

Any other use of this information without the express written consent
of Sun Microsystems is prohibited. Sun Microsystems expressly disclaims
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         SUN MICROSYSTEMS SECURITY BULLETIN: #00131, 14 September 1995
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I.  Vulnerability history and analysis

    A. Vulnerability history

    This set of new patches fixes a security hole involving the Solaris
    "ps" program. The effect of the bug is to create a race condition
    which can make it possible under some conditions for a
    non-privileged user of the system to gain root access.

    The existence of the flaw was publicly announced on August 14th on
    a mailing list known as "BUGTRAQ", maintained by Scott Chasin. The
    notice is "bugtraq-alert-081495.01". An exploitation script was
    released by Mr. Chasin that same day.

    We have reason to believe this bug is being actively exploited and
    recommend that the relevant patch be installed on any affected
    system. The workaround described below is also believed to be
    effective and is presented as an alternative.

    B. Vulnerability analysis

    The race condition can only be exploited if the attacker has access
    to certain temporary files used by the "ps" program. Access to
    these temporary files may be possible if the permissions on the
    /tmp directory are set incorrectly.

    The permissions on the /tmp directory are often reset incorrectly
    by the system at boot time if tmpfs (which is mounting swap as
    /tmp) is in use.

    To determine if you are running tmpfs, the following command can be
    used to verify if the filesystem for /tmp is swap:

       % /usr/sbin/df -k /tmp
       Filesystem          kbytes    used   avail capacity  Mounted on
       swap                 28348     12    28336     0%    /tmp

    or look in the file /etc/vfstab for the configuration line:

       #device     device   mount    FS      fsck    mount     mount
       #to mount   to fsck  point    type    pass    at boot   options
       swap          -      /tmp     tmpfs     -      yes         -

    If either of these two conditions exist, then you are running tmpfs
    and the system may automatically reset the permission bits of /tmp
    at the next reboot.

    To verify if your configuration is currently vulnerable, the
    following command may be used:

        % /usr/bin/ls -ld /tmp
        drwxrwxrwt   2 sys      sys        61 Aug 15 12:12 /tmp

    If the sticky bit is set, the final flag in the permissions setting
    will be a "t", as shown. With the permissions shown above, your
    system is not vulnerable. If the final flag is an "x" (not shown),
    the sticky bit is not set and your system is vulnerable.

    Setting the sticky bit on the /tmp and /var/tmp directories is
    sound security practice in general, and we recommend this be done
    even if the patch discussed in this bulletin is also installed.

    C. Temporary workaround

    A workaround that takes effect immediately is to set the sticky bit
    on the /tmp directory, by issuing the following command as root:

        # /usr/bin/chmod 1777 /tmp

    In addition, the ownership and group membership of the /tmp
    directory should be verified using /usr/bin/ls -ld /tmp. To reset

    them to their original settings, issue as root the commands:

        # /usr/bin/chown sys /tmp
        # /usr/bin/chgrp sys /tmp

    Note that the effect of the commands shown above will be lost when
    the system reboots. That is, the system will become vulnerable
    again every time it is rebooted.  In order to make the change
    permanent you will need to put similar commands into the system
    boot sequence.

    D. Permanent workaround

    The effect of the commands shown above will be lost when the system
    reboots. In order to make the change permanent you will need to put
    similar commands into the system boot sequence.

    You can do this by creating a script called (for example)
    "/etc/init.d/tmpfsfix" containing the lines:

             #!/bin/sh

             if [ -d /tmp ]
             then
                /usr/bin/chmod 1777 /tmp
                /usr/bin/chgrp sys /tmp
                /usr/bin/chown sys /tmp
             fi

    and executing as root a command similar to:

        # /usr/bin/ln -s /etc/init.d/tmpfsfix /etc/rc3.d/S79tmpfix

    The next time the system boots the sticky bit will be set on the
    /tmp directory, and the owner and group of /tmp will be set to
    sys.


II. Announcement of patches for Solaris 2.x "ps_data" vulnerability

    A. Patch list

    We have produced patches for the versions of SunOS shown below.

         OS version      Patch ID    Patch File Name
         ----------      ---------   --------------- 
         5.3             101545-02   101545-02.tar.Z
         5.4             102711-01   102711-01.tar.Z
         5.4_x86         102712-01   102712-01.tar.Z

    B. Patch notes
 
    1. SunOS 4.1.x systems are not affected by this bug.

    2. The fix has been applied to the upcoming version of Solaris.


III. Checksum Table

    In the checksum table we show the BSD and SVR4 checksums and MD5
    digital signatures for the compressed tar archives.

    File            BSD          SVR4        MD5
    Name            Checksum     Checksum    Digital Signature
    --------------- -----------  ----------  --------------------------------
    101545-02.tar.Z 41218    77  47754  153  A8FB866780E7207D26CF16210BCFDC83
    102711-01.tar.Z 17256    69  20376  138  98A449372C5ABBDB7C37B08BFE0E6ED7
    102712-01.tar.Z 29867    68  56717  136  E324004BB8C09990B2790CB5D29D3AF5

    The checksums shown above are from the BSD-based checksum
    (on 4.1.x, /bin/sum;  on Solaris 2.x, /usr/ucb/sum) and from
    the SVR4 version on Solaris 2.x (/usr/bin/sum).


APPENDICES

A.  How to obtain Sun security patches

    1. If you have a support contract

    Customers with Sun support contracts can obtain the patches listed
    here (and all other security patches, and a list of patches) from:

       - Local Sun answer centers, worldwide
       - SunSolve Online, and SunSITEs worldwide

    The patches are available via World Wide Web at http://sunsolve1.sun.com. 

    You should also contact your answer center if you have a support
    contract and:

       - You need assistance in installing a patch 
       - You need additional patches
       - You want an existing patch ported to another platform
       - You believe you have encountered a bug in a Sun patch
       - You want to know if a patch exists, or when one will be ready

    2. If you do not have a support contract

    Sun also makes its security patches available to customers who do
    not have a support contract, via anonymous ftp, from the directory
    /systems/sun/sun-dist on the system ftp.uu.net.

    Sun does not furnish patches to any external distribution sites
    other than the ones mentioned here. 


    3. About the checksums

    Patches announced in a Sun security bulletin are uploaded to the
    ftp.*.net sites just before the bulletin is released, and seldom
    updated.  In contrast, the "supported" patch databases are
    refreshed nightly, and will often contain newer versions of a patch
    incorporating changes which are not security-related.

    So that you can quickly verify the integrity of the patch files
    themselves, we supply checksums for the tar archives in each
    bulletin. The listed checksums should always match those on the
    ftp.*.net systems. (The rare exceptions are listed in the
    "checksums" file there.)

    Normally, the listed checksums will also match the patches on the
    SunSolve database. However, this will not be true if we have
    changed (as we sometimes do) the README file in the patch after the
    bulletin has been released.

    In the future we plan to provide checksum information for the
    individual components of a patch as well as the compressed archive
    file. This will allow customers to determine, if need be, which
    file(s) have been changed since we issued the bulletin containing
    the checksums.

    If you would like assistance in verifying the integrity of a patch
    file please contact this office or your local answer center.


B.  How to report or inquire about Sun security problems

    If you discover a security problem with Sun software or wish to
    inquire about a possible problem, contact one or more of the
    following:

       - Your local Sun answer centers
       - Your representative computer security response team, such as CERT 
       - This office. Address postal mail to:

         Sun Security Coordinator
         MS MPK2-04
         2550 Garcia Avenue Mountain
   View, CA 94043-1100

   Phone: 415-688-9081
         Fax:   415-688-9101
         E-mail: security-alert@Sun.COM

     We strongly recommend that you report problems to your local Answer
     Center. In some cases they will accept a report of a security bug
     even if you do not have a support contract. An additional notification
     to the security-alert alias is suggested but should not be used as your
     primary vehicle for reporting a bug.


C.   How to obtain Sun security bulletins

     1. Subscription information

     Sun Security Bulletins are available free of charge as part of
     our Customer Warning System. It is not necessary to have a Sun
     support contract in order to receive them.

     To subscribe to this bulletin series, send mail to the address
     "security-alert@Sun.COM" with the subject "subscribe CWS
     your-mail-address" and a message body containing affiliation and
     contact information. To request that your name be removed from the
     mailing list, send mail to the same address with the subject
     "unsubscribe CWS your-mail-address". Do not include other requests
     or reports in a subscription message.

     Due to the volume of subscription requests we receive, we cannot
     guarantee to acknowledge requests. Please contact this office if
     you wish to verify that your subscription request was received, or
     if you would like your bulletin delivered via postal mail or fax.

     2. Obtaining old bulletins

     Sun Security Bulletins are archived on ftp.uu.net (in the same
     directory as the patches) and on SunSolve. Please try these
     sources first before contacting this office for old bulletins.

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