MCI Telecommunications internetMCI Security Group Report Title: iMCI MIIGS Security Alert Report Name: Vulnerability in xlock Report Number: iMCISE:IMCICERT:050797:01:P1R1 Report Date: 05/07/97 Report Format: Formal Report Classification: MCI Informational Report Reference: http://www.security.mci.net Report Distribution: iMCI Security, MCI Internal Internet Gateway Security (MIIGS), MCI Emergency Alert LiSt (MEALS) (names on file) -------------------------------------------------------------------------- -----BEGIN PGP SIGNED MESSAGE----- ============================================================================= CERT* Advisory CA-97.13 Original issue date: May 7, 1997 Last revised: -- Topic: Vulnerability in xlock - ----------------------------------------------------------------------------- The CERT Coordination Center has received reports that a buffer overflow condition exists in some implementations of xlock. This vulnerability makes it possible for local users (users with access to an account on the system) to execute arbitrary programs as a privileged user. Exploitation information involving this vulnerability has been made publicly available. If your system is vulnerable, the CERT/CC team recommends installing a patch from your vendor. If you are not certain whether your system is vulnerable or if you know that your system is vulnerable and you cannot add a patch immediately, we urge you to apply the workaround described in Section III.B. We will update this advisory as we receive additional information. Please check our advisory files regularly for updates that relate to your site. - ----------------------------------------------------------------------------- I. Description xlock is a program that allows a user to "lock" an X terminal. A buffer overflow condition exists in some implementations of xlock. It is possible attain unauthorized access to a system by engineering a particular environment and calling a vulnerable version of xlock that has setuid or setgid bits set. Information about vulnerable versions must be obtained from vendors. Some vendor information can be found in Appendix A of this advisory. Exploitation information involving this vulnerability has been made publicly available. Note that this problem is different from that discussed in CERT Advisory CA-97.11.libXt. II. Impact Local users are able to execute arbitrary programs as a privileged user without authorization. III. Solution Install a patch from your vendor as described in Solution A. If you are not certain whether your system is vulnerable or if you know that your system is vulnerable and you cannot install a patch immediately, we recommend Solution B. A. Obtain and install a patch for this problem. Below is a list of vendors who have provided information about xlock. Details are in Appendix A of this advisory; we will update the appendix as we receive more information. If your vendor's name is not on this list, the CERT/CC did not hear from that vendor. Please contact your vendor directly. Berkeley Software Design, Inc. (BSDI) Cray Research - A Silicon Graphics Company Data General Corporation Digital Equipment Corporation FreeBSD, Inc. Hewlett-Packard Company IBM Corporation LINUX NEC Corporation The Open Group [This group distributes the publicly available software that was formerly distributed by X Consortium] Solbourne Sun Microsystems, Inc. B. We recommend the following workaround if you are not certain whether your system is vulnerable or if you know that your system is vulnerable and you cannot install a patch immediately. 1. Find and disable any copies of xlock that exist on your system and that have the setuid or setgid bits set. 2. Install a version of xlock known to be immune to this vulnerablility. One such supported tool is xlockmore. The latest version of this tool is 4.02, and you should ensure that this is the version you are using. This utility can be obtained from the following site: ftp://ftp.x.org/contrib/applications/xlockmore-4.02.tar.gz MD5 (xlockmore-4.02.tar.gz) = c158e6b4b99b3cff4b52b39219dbfe0e You can also obtain this version from mirror sites. A list of these sites will be displayed if you are not able to access the above archive due to load. ........................................................................... Appendix A - Vendor Information Below is a list of the vendors who have provided information for this advisory. We will update this appendix as we receive additional information. If you do not see your vendor's name, the CERT/CC did not hear from that vendor. Please contact the vendor directly. Berkeley Software Design, Inc. (BSDI) ===================================== BSD/OS is not vulnerable to the problem in xlock since our xlock is not setuid. Cray Research - A Silicon Graphics Company ========================================== Cray Research does not include xlock in its X Window releases, so we are not at risk on the xlock buffer overflow problem. Data General Corporation ======================== The xlock sources (xlockmore-3.7) that DG includes in its contributed software package have been modified to remove this vulnerability. These will be available when release 8 comes out. We also recommend that our customers who have the current version should change the sprintf calls in resource.c to snprintf calls, rebuild and reinstall the package. Digital Equipment Corporation ============================= This reported problem is not present for Digital's ULTRIX or Digital UNIX Operating Systems Software. FreeBSD, Inc. ============= The xlockmore version we ship in our ports collection is vulnerable in all shipped releases. The port in FreeBSD-current is fixed. Solution is to install the latest xlockmore version (4.02). Hewlett-Packard Company ======================= We ship an suid root program vuelock that is based on xlock. It does have the vulnerability. The only workaround is to remove the executable, the patch is "in process". IBM Corporation =============== AIX is vulnerable to the conditions described in this advisory. The following APARs will be released soon: AIX 3.2: APAR IX68189 AIX 4.1: APAR IX68190 AIX 4.2: APAR IX68191 IBM and AIX are registered trademarks of International Business Machines Corporation. LINUX ===== Red Hat: Not vulnerable Caldera: Not vulnerable Debian: An updated package is on the Debian site SuSE: ftp://ftp.suse.com/pub/SuSE-Linux/suse_update/S.u.S.E.-4.4.1/xap1/xlock And in general the new Xlockmore release fixes the problems. NEC Corporation =============== UX/4800 Not vulnerable for all versions. EWS-UX/V(Rel4.2MP) Not vulnerable for all versions. EWS-UX/V(Rel4.2) Not vulnerable for all versions. UP-UX/V(Rel4.2MP) Not vulnerable for all versions. The Open Group ============== Publicly available software that was formerly distributed by the X Consortium - Not vulnerable. Solbourne ========= Solbourne is not vulnerable to this attack. Sun Microsystems, Inc. ====================== We are producing patches for OpenWindows 3.0 for Sun OS versions 4.1.3_U1, 4.1.4, 5.3, 5.4, 5.5, and 5.5.1. - ----------------------------------------------------------------------------- The CERT Coordination Center thanks David Hedley for reporting the original problem and Kaleb Keithley at The Open Group for his support in the development of this advisory. - ----------------------------------------------------------------------------- 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 (see http://www.first.org/team-info/). CERT/CC Contact Information - ---------------------------- Email cert@cert.org Phone +1 412-268-7090 (24-hour hotline) CERT personnel answer 8:30-5:00 p.m. EST(GMT-5) / EDT(GMT-4) and are on call for emergencies during other hours. Fax +1 412-268-6989 Postal address CERT Coordination Center Software Engineering Institute Carnegie Mellon University Pittsburgh PA 15213-3890 USA Using encryption We strongly urge you to encrypt sensitive information sent by email. We can support a shared DES key or PGP. Contact the CERT/CC for more information. Location of CERT PGP key ftp://info.cert.org/pub/CERT_PGP.key Getting security information CERT publications and other security information are available from http://www.cert.org/ ftp://info.cert.org/pub/ CERT advisories and bulletins are also posted on the USENET newsgroup comp.security.announce To be added to our mailing list for advisories and bulletins, send email to cert-advisory-request@cert.org In the subject line, type SUBSCRIBE your-email-address - --------------------------------------------------------------------------- * Registered U.S. Patent and Trademark Office. Copyright 1997 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. The CERT Coordination Center is part of the Software Engineering Institute (SEI). The SEI is sponsored by the U.S. Department of Defense. - --------------------------------------------------------------------------- This file: ftp://info.cert.org/pub/cert_advisories/CA-97.13.xlock http://www.cert.org click on "CERT Advisories" ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Revision history -----BEGIN PGP SIGNATURE----- Version: 2.6.2 iQCVAwUBM3DOFnVP+x0t4w7BAQH9MwQAwULlCDTqDbW+CiS0/Z36BtGf6Eqzx43B pEt72rQlQbw2AqRnHeq85dzVUB4eKmL0T//bGYyo0sCt+8nlFaS3cNYh0cyl3jdu JPDVoNhWB7v2+8nHvAEDz2UdomNVaxXDFvAbZ9JvEk/Ex6aFiXtl4qXdjxtcC4ze kGKLcu0+LzE= =nF5B -----END PGP SIGNATURE-----