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TUCoPS :: Linux :: Apps A-M :: n-062.txt

MIT krb5 Buffer Overrun and Underrun (CIAC N-062)




             __________________________________________________________

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

                             INFORMATION BULLETIN

        MIT krb5 Buffer overrun and underrun in Principal Name Handling
                     [MIT krb5 Security Advisory 2003-005]

March 20, 2003 22:00 GMT                                          Number N-062
______________________________________________________________________________
PROBLEM:       Buffer overrun and underrun problems exist in Kerberos 
               principal name handling in unusual cases, such as names with 
               zero components, names with one empty component, or host-based 
               service principal names with no host name component. 
PLATFORM:      MIT Kerberos 5, all released versions though 1.2.7 and 
               1.3-alpha1. 
DAMAGE:        Corruption of malloc pool, probably leading to program crash. 
SOLUTION:      Apply patch as stated in MIT's security bulletin. 
______________________________________________________________________________
VULNERABILITY  The risk is MEDIUM. Although this is a Denial-of-Service, krb5 
ASSESSMENT:    is widely implemented in security applications. This 
               vulnerability can lead to other exploits, dependent upon the 
               malloc implementation and platform. 
______________________________________________________________________________
LINKS: 
 CIAC BULLETIN:      http://www.ciac.org/ciac/bulletins/n-062.shtml 
 ORIGINAL BULLETIN:                                                           
                     http://web.mit.edu/kerberos/www/advisories
                           /MITKRB5-SA-2003-005-buf.txt 
______________________________________________________________________________

[***** Start MIT krb5 Security Advisory 2003-005 *****]

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                 MIT krb5 Security Advisory 2003-005

2003-03-19

Topic: Buffer overrun and underrun in principal name handling

Severity: SERIOUS

SUMMARY
=======

Buffer overrun and underrun problems exist in Kerberos principal name
handling in unusual cases, such as names with zero components, names
with one empty component, or host-based service principal names with
no host name component.

IMPACT
======

 * Corruption of malloc pool, probably leading to program crash.

   + The KDC may be vulnerable.

   + Depending on the malloc implementation and platform, it may be
     possible to build more serious exploits on this.

 * Reference to data just past the end of an array in the KDC, for
   comparison against certain fixed data.  May result in crashing the
   KDC.

AFFECTED SOFTWARE
=================

MIT Kerberos 5, all released versions though 1.2.7 and 1.3-alpha1.

FIX
===

The following patches should fix the most urgent aspects of the
problems in the 1.2.7 release.  If these patches do not apply cleanly
to 1.2.6 and earlier versions, the corresponding changes should be
fairly straightforward.  The patch to krb5.hin should change any
missed overrun cases in this area into null pointer dereferences,
which will be more likely to crash the program instead of referencing
arbitrary data.

Patch: http://web.mit.edu/kerberos/www/advisories/MITKRB5-SA-2003-005-patch.txt
Patch PGP signature: http://web.mit.edu/kerberos/www/advisories/MITKRB5-SA-2003-005-patch.txt.asc

The problem exists in other parts of the code as well, but should only
result in crashing application servers when the realm has been
misconfigured to use broken service names, or crashing application
clients when they are supplied broken principal names.

ACKNOWLEDGMENTS
===============

Thanks to Nalin Dahyabhai of Red Hat for bringing the problems to our
attention.

CONTACT
=======

For more information, contact Ken Raeburn <raeburn@mit.edu>, Sam
Hartman <hartmans@mit.edu>, or Marshall Vale <mjv@mit.edu>.

This announcement and related security advisories may be found on the
MIT Kerberos security advisory page at:

	http://web.mit.edu/kerberos/www/advisories/index.html

The main MIT Kerberos web page is at:

	http://web.mit.edu/kerberos/www/index.html

REVISION HISTORY
================
2003-03-19	original release
2003-03-19	moved patch to separate file with separate signature
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[***** End MIT krb5 Security Advisory 2003-005 *****]

_______________________________________________________________________________

CIAC wishes to acknowledge the contributions of Massachusetts Institute of 
Technology (MIT) for the information contained in this bulletin.
_______________________________________________________________________________


CIAC, the Computer Incident Advisory Capability, is the computer
security incident response team for the U.S. Department of Energy
(DOE) and the emergency backup response team for the National
Institutes of Health (NIH). CIAC is located at the Lawrence Livermore
National Laboratory in Livermore, California. CIAC is also a founding
member of FIRST, the Forum of Incident Response and Security Teams, a
global organization established to foster cooperation and coordination
among computer security teams worldwide.

CIAC services are available to DOE, DOE contractors, and the NIH. CIAC
can be contacted at:
    Voice:    +1 925-422-8193 (7x24)
    FAX:      +1 925-423-8002
    STU-III:  +1 925-423-2604
    E-mail:   ciac@ciac.org

Previous CIAC notices, anti-virus software, and other information are
available from the CIAC Computer Security Archive.

   World Wide Web:      http://www.ciac.org/
   Anonymous FTP:       ftp.ciac.org

PLEASE NOTE: Many users outside of the DOE, ESnet, and NIH computing
communities receive CIAC bulletins.  If you are not part of these
communities, please contact your agency's response team to report
incidents. Your agency's team will coordinate with CIAC. The Forum of
Incident Response and Security Teams (FIRST) is a world-wide
organization. A list of FIRST member organizations and their
constituencies can be obtained via WWW at http://www.first.org/.

This document was prepared as an account of work sponsored by an
agency of the United States Government. Neither the United States
Government nor the University of California nor any of their
employees, makes any warranty, express or implied, or assumes any
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