AUSCERT External Security Bulletin Redistribution

                 ESB-2002.381 -- CERT Advisory CA-2002-24
                     Trojan Horse OpenSSH Distribution
                               2 August 2002


        AusCERT Security Bulletin Summary

Product:                OpenSSH
Vendor:                 CERT/CC
Impact:                 Increased Privileges
                        Reduced Security
Access Required:        Remote

Ref:                    AL-2002.10

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CERT Advisory CA-2002-24 Trojan Horse OpenSSH Distribution

   Original issue date: August 1, 2002
   Last revised: --
   Source: CERT/CC

   A complete revision history is at the end of this file.


   The  CERT/CC  has received confirmation that some copies of the source
   code  for the OpenSSH package were modified by an intruder and contain
   a Trojan horse.

   We  strongly encourage sites which employ, redistribute, or mirror the
   OpenSSH   package   to  immediately  verify  the  integrity  of  their

I. Description

   The  CERT/CC  has received confirmation that some copies of the source
   code  for  the  OpenSSH  package have been modified by an intruder and
   contain  a  Trojan  horse. The following advisory has been released by
   the OpenSSH development team


   The following files were modified to include the malicious code:


   These  files  appear to have been placed on the FTP server which hosts
   ftp.openssh.com and ftp.openbsd.org on the 30th or 31st of July, 2002.
   The OpenSSH development team replaced the Trojan horse copies with the
   original,  uncompromised  versions at 13:00 UTC, August 1st, 2002. The
   Trojan  horse  copy  of  the source code was available long enough for
   copies to propagate to sites that mirror the OpenSSH site.

   The  Trojan  horse  versions of OpenSSH contain malicious code that is
   run  when  the  software  is  compiled.  This code connects to a fixed
   remote  server  on  6667/tcp.  It can then open a shell running as the
   user who compiled OpenSSH.

II. Impact

   An intruder operating from (or able to impersonate) the remote address
   specified in the malicious code can gain unauthorized remote access to
   any  host  which  compiled a version of OpenSSH from this Trojan horse
   version  of  the source code. The level of access would be that of the
   user who compiled the source code.

III. Solution

   We  encourage  sites who downloaded a copy of the OpenSSH distribution
   to  verify the authenticity of their distribution, regardless of where
   it  was  obtained.  Furthermore, we encourage users to inspect any and
   all  software that may have been downloaded from the compromised site.
   Note  that  it is not sufficient to rely on the timestamps or sizes of
   the  file  when  trying to determine whether or not you have a copy of
   the Trojan horse version.

Where to get OpenSSH

   The primary distribution site for OpenSSH is


   Sites that mirror the OpenSSH source code are encouraged to verify the
   integrity of their sources.

Verify MD5 checksums

   You  can  use  the  following MD5 checksums to verify the integrity of
   your OpenSSH source code distribution:
   Correct versions:

     459c1d0262e939d6432f193c7a4ba8a8 openssh-3.4p1.tar.gz
     d5a956263287e7fd261528bb1962f24c openssh-3.4p1.tar.gz.sig
     39659226ff5b0d16d0290b21f67c46f2 openssh-3.4.tgz
     9d3e1e31e8d6cdbfa3036cb183aa4a01 openssh-3.2.2p1.tar.gz
     be4f9ed8da1735efd770dc8fa2bb808a openssh-3.2.2p1.tar.gz.sig

   At  least  one  version of the modified Trojan horse distributions was
   reported to have the following checksum:
   Trojan horse version:

     3ac9bc346d736b4a51d676faa2a08a57 openssh-3.4p1.tar.gz

Verify PGP signature

   Additionally,  distributions  of  the  portable release of OpenSSH are
   distributed  with  detached PGP signatures. Note that the Trojan horse
   versions  were  not  signed  correctly,  and  attempts  to  verify the
   signatures would have failed.

   As a matter of good security practice, the CERT/CC encourages users to
   verify,  whenever  possible, the integrity of downloaded software. For
   more information, see


Appendix A. - Vendor Information

   This  appendix  contains  information  provided  by  vendors  for this
   advisory.  As  vendors  report new information to the CERT/CC, we will
   update this section and note the changes in our revision history. If a
   particular  vendor  is  not  listed  below, we have not received their

Connectiva Linux

     Conectiva Linux distributes openssh-3.4p1 as a security update. The
     distributed  copy  is  the original one and is not affected by this
     trojan.  The  detached  digital  signature is always checked before
     building third party packages.


     MandrakeSoft  has  verified  that the openssh-3.4p1 sources used to
     build  it's  latest  updates (ref. MDKSA-2002:040-1) do not contain
     this trojan.

   Feedback can be directed to the author: Chad Dougherty.

   This document is available from:

CERT/CC Contact Information

   Email: cert@cert.org
          Phone: +1 412-268-7090 (24-hour hotline)
          Fax: +1 412-268-6989
          Postal address:
          CERT Coordination Center
          Software Engineering Institute
          Carnegie Mellon University
          Pittsburgh PA 15213-3890

   CERT/CC   personnel   answer  the  hotline  08:00-17:00  EST(GMT-5)  /
   EDT(GMT-4)  Monday  through  Friday;  they are on call for emergencies
   during other hours, on U.S. holidays, and on weekends.

Using encryption

   We  strongly  urge you to encrypt sensitive information sent by email.
   Our public PGP key is available from

   If  you  prefer  to  use  DES,  please  call the CERT hotline for more

Getting security information

   CERT  publications  and  other security information are available from
   our web site

   To  subscribe  to  the CERT mailing list for advisories and bulletins,
   send  email  to majordomo@cert.org. Please include in the body of your

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   *  "CERT"  and  "CERT  Coordination Center" are registered in the U.S.
   Patent and Trademark Office.

   Any  material furnished by Carnegie Mellon University and the Software
   Engineering  Institute  is  furnished  on  an  "as is" basis. Carnegie
   Mellon University makes no warranties of any kind, either expressed or
   implied  as  to  any matter including, but not limited to, warranty of
   fitness  for  a  particular purpose or merchantability, exclusivity or
   results  obtained from use of the material. Carnegie Mellon University
   does  not  make  any warranty of any kind with respect to freedom from
   patent, trademark, or copyright infringement.

   Conditions for use, disclaimers, and sponsorship information

   Copyright 2002 Carnegie Mellon University.

   Revision History
August 1, 2002: Initial release

Version: PGP 6.5.8


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