============================================================================= CA-94:09 CERT Advisory May 23, 1994 /bin/login Vulnerability ----------------------------------------------------------------------------- The CERT Coordination Center has learned of a vulnerability in /bin/login. This vulnerability potentially affects all IBM AIX 3 systems and Linux systems. At this time, we believe that only IBM AIX 3 and Linux systems are at risk. Included with this advisory is an appendix containing the CA-94:09.README, which lists the vendors who have responded to our inquiries, and the status of their investigation into this vulnerability report. As we receive additional information relating to this advisory, we will place it, along with any clarifications, in the README file, available via anonymous FTP from info.cert.org. We encourage you to check the README files regularly for updates on advisories that relate to your site. ----------------------------------------------------------------------------- I. Description of IBM AIX vulnerability A vulnerability exists in /bin/login on all IBM AIX 3 systems. II. Impact of IBM AIX vulnerability Remote users can obtain unauthorized root access on the affected hosts. III. Solution for IBM AIX vulnerability IBM is working on an official fix, which is still under development. The reference number for this fix is APAR IX44254. Until you obtain the official fix from IBM, we encourage you to apply the workaround or install the emergency fix below. A. Workaround The recommended workaround is to disable the rlogin daemon: 1. As root, edit /etc/inetd.conf Comment out the line 'login ... rlogin' 2. Run 'inetimp' 3. Run 'refresh -s inetd' B. Emergency fix The emergency fix for the different levels of AIX 3 affected by this vulnerability is available via anonymous FTP from software.watson.ibm.com:/pub/rlogin/rlogin.tar.Z. Installation instructions are included in the README file (which is included in rlogin.tar.Z). Checksum information for rlogin.tar.Z: BSD: 25285 317 SystemV: 13021 633 rlogin.tar.Z MD5: MD5 (rlogin.tar.Z) = 803ee38c2e3b8c8c575e2ff5e921034c C. Official fix The official fix for this problem can be ordered as APAR IX44254. To order an APAR from IBM in the U.S., call 1-800-237-5511 and ask IBM to ship it as soon as it is available. According to IBM, this fix will be available in approximately two weeks. APARs may be obtained outside the U.S. by contacting your local IBM representative. IV. Description of Linux vulnerability A vulnerability exists in /bin/login for Linux systems. V. Impact of Linux vulnerability Any user, remote or local, can obtain unauthorized root access on the affected hosts. VI. Solution for Linux vulnerability A patch that addresses the remote access problem has been made available via anonymous FTP from sunsite.unc.edu: /pub/Linux/system/Network/sunacm/URGENT/README.security /pub/Linux/system/Network/sunacm/URGENT/security.tgz The "security.tgz" file includes other security fixes in addition to the /bin/login patch. Checksum information for README.security: BSD: 09575 1 SystemV: 20945 1 README.security MD5: MD5 (README.security) = 41d14d7b8725c7a1015adeb49601619b Checksum information for security.tgz: BSD: 32878 257 SystemV: 40797 513 security.tgz MD5: MD5 (security.tgz) = dd4585cf4da1b52d25d619bf45f55b75 To address the local access problem, we encourage you to install a version of /bin/login that does not allow the -f option in the form "-f<user>", but only allows this option in the form "-f <user>", as two arguments. At this time, we do not know which versions of login.c are vulnerable. As we receive additional information, we will update the CA-94:09.README file. Again, we encourage you to check this README file regularly for updates. --------------------------------------------------------------------------- The CERT Coordination Center wishes to thank Axel Clauberg of University of Cologne for reporting the IBM AIX problem, and IBM for their assistance in responding to this problem. --------------------------------------------------------------------------- If you believe that your system has been compromised, contact the CERT Coordination Center or your representative in 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 USA Past advisories and their associated README files, information about FIRST representatives, and other information related to computer security are available for anonymous FTP from info.cert.org. ----------------------------------------------------------------------------- Appendix CA-94:09.README This file is a supplement to the CERT Advisory CA-94:09.bin.login.vulnerability of May 23, 1994, and will be updated as additional information becomes available. We have received feedback from these vendors, who indicated that their products are not vulnerable: Amdahl Apple BSD BSDI Harris HP Motorola NeXT Pyramid SCO SGI Solbourne Sony Sun CERT has verified that the following vendor products are not vulnerable: Free BSD We have received feedback from these vendors, who have made patches available to address the /bin/login vulnerability: IBM workaround: see Section III. Solution for IBM AIX vulnerability A. Workaround of CERT advisory CA-94:xx emergency patch: software.watson.ibm.com:/pub/rlogin/rlogin.tar.Z Official patch: APAR IX44254 Linux patch: sunsite.unc.edu:/pub/Linux/system/Network/sunacm/URGENT/*