RSI.0012.12-03-98.SOLARIS.MKCOOKIE



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                   Repent Security Incorporated, RSI
                       [ http://www.repsec.com ]


           *** RSI ALERT ADVISORY ***
 

--- [CREDIT] --------------------------------------------------------------

Nick Dubee: Discovered the vulnerability
Mark Zielinski: Author of the advisory

--- [SUMMARY] -------------------------------------------------------------

Announced:     November 12, 1998
Report code:   RSI.0012.12-03-98.SOLARIS.MKCOOKIE
Report title:  Solaris x86 mkcookie

Vulnerability: Please see the details section 
Vendor status: Sun Microsystems contacted on November 12, 1998
Patch status:  No patch is currently available

Platforms:     Solaris 2.5 x86, 2.5.1 x86, 2.6 x86, 2.7 x86

Reference:     http://www.repsec.com/advisories.html
Impact:        If exploited, an attacker could potentially compromise
               root access locally on your server

NOTE:          Solaris versions 2.3 x86, and 2.4 x86 were NOT tested
               however they could be subject to the same vulnerability.


--- [DETAILS] -------------------------------------------------------------

Description:   The mkcookie program is a Solaris utility used to 
               generate fresh 'Magic Cookies' each time the X server
               is run.  This program is installed SUID root as
               /usr/openwin/lib/mkcookie.

Problem:       A programming fault has been discovered in the way
               mkcookie copies the contents of the $HOME evironment
               variable into a buffer that has a predefined limit with
               no bounds checking.

Details:       Local users on the system can set their $HOME
               environment variable to machine code that will
               execute commands as root when mkcookie is run.

               This particular problem is not exploitable on the
               Sparc architecture due to the way the register values
               are saved.


--- [FIX] -----------------------------------------------------------------

Solution:      Sun is working on patches which relate to this mkcookie
               vulnerability.  The patches will be made available to all
               Sun customers via the World Wide Web at:

               <URL:http://sunsolve.sun.com/sunsolve/pubpatches/patches.html>

               In the meantime, take the SUID bit off mkcookie until
               a patch is released for the version of Solaris you are using.

               repent% su
               Password:
               # chmod 711 /usr/openwin/lib/mkcookie


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E-Mail: advise@repsec.com
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Copyright December 1998 RepSec, Inc.

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