-----BEGIN PGP SIGNED MESSAGE----- [ For Public Release ] __________________________________________________________ The U.S. Department of Energy Computer Incident Advisory Capability ___ __ __ _ ___ / | /_\ / \___ __|__ / \ \___ __________________________________________________________ INFORMATION BULLETIN Vulnerability in Bind (Update to Bulletin G-14, Domain Name Service Vulnerabilities) August 14, 1997 21:00 GMT Number H-96 ______________________________________________________________________________ PROBLEM: Domain Name Service (DNS) servers being exploited, using BIND and sendmail weaknesses. PLATFORM: Systems running any version of BIND before release 8.1.1. DAMAGE: Data becomes corrupted ("cache poisoning"). SOLUTION: Patches or workarounds are available for several platforms. See below. ______________________________________________________________________________ VULNERABILITY Intruders have been able to exploit this vulnerability on DNS ASSESSMENT: servers. This vulnerability may potentially extend to other network services. ______________________________________________________________________________ [Start CERT Advisory] ============================================================================= CERT* Advisory CA-97.22 Original issue date: August 13, 1997 Last revised: -- Topic: BIND - the Berkeley Internet Name Daemon - ----------------------------------------------------------------------------- *** This advisory supersedes CA-96.02. *** Several vulnerabilities in the Berkeley Internet Name Daemon (BIND) have been fixed in the current version of BIND. One of those vulnerabilities is now being exploited, a vulnerability that results in cache poisoning (malicious or misleading data from a remote name server is saved [cached] by another name server). All versions of BIND before release 8.1.1 are vulnerable. The CERT/CC team recommends installing a patch from your vendor (See Appendix A). Until you can install a vendor patch, we recommend the workaround described in Section III.B. We also urge you to take the additional precautions described in Section III.C. 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 The Berkeley Internet Name Daemon (BIND) is an implementation of the Domain Name Service (DNS) written primarily for UNIX Systems. BIND consists of three parts: * The client part. This part contains subroutine libraries used by programs that require DNS services. Example clients of these libraries are telnet, the X Windows System, and ssh (the secure shell). The client part consists of subroutine libraries, header files, and manual pages. * The server part. This part contains the name server daemon (named) and its support program (named-xfer). These programs provide one source of the data used for mapping between host names and IP addresses. When appropriately configured, these name server daemons can interoperate across a network (the Internet for example) to provide the mapping services for that network. The server part consists of the daemon, its support programs and scripts, and manual pages. * The tools part. This part contains various tools for interrogating name servers in a network. They use the client part to extract information from those servers. The tools part consists of these interrogation tools and manual pages. As BIND has matured, several vulnerabilities in the client, server, and tools parts have been fixed. Among these is server cache poisoning. Cache poisoning occurs when malicious or misleading data received from a remote name server is saved (cached) by another name server. This "bad" data is then made available to programs that request the cached data through the client interface. Analysis of recent incidents reported to the CERT Coordination Center has shown that the cache poisoning technique is being used to adversely affect the mapping between host names and IP addresses. Once this mapping has been changed, any information sent between hosts on a network may be subjected to inspection, capture, or corruption. Although the new BIND distributions do address important security problems, not all known problems are fixed. In particular, several problems can be fixed only with the use of cryptographic authentication techniques. Implementing and deploying this solution is non-trivial; work on this task is currently underway within the Internet community. II. Impact The mapping between host names and IP addresses may be changed. As a result, attackers can inspect, capture, or corrupt the information exchanged between hosts on a network. III. Solution A. Obtain and install a patch for this problem. Information from vendors can be found in Appendix A of this advisory; we will update the appendix as we receive more information. B. Until you are able to install the appropriate patch, we recommend the following workaround. The "best practice" for operating the publicly available BIND system can be either: * a heterogeneous solution that involves first installing BIND release 4.9.6 and then release 8.1.1, or * a homogeneous solution that involves installing only BIND release 8.1.1. In the paragraphs below, we describe how to determine which solution you should use. 1. Shared Object Client Subroutine Library If your system and its programs rely on the shared object client subroutine library that comes with some releases of BIND, probably named libresolv.so, then you need the shared object subroutine library and other client software from release 4.9.6. (As of this writing, BIND version 8 does not yet support the client part as a shared object library.) This client software is available at ftp://ftp.isc.org/isc/bind/src/4.9.6/bind-4.9.6-REL.tar.gz MD5 (bind-4.9.6-REL.tar.gz) = 76dd66e920ad0638c8a37545a6531594 Follow the instructions in the file named INSTALL in the top-level directory. After installing this client part, install the server and tool parts from release 8.1.1. This software is available at ftp://ftp.isc.org/isc/bind/src/8.1.1/bind-src.tar.gz MD5 (bind-src.tar.gz) = 7487b8d647edba2053edc1cda0c6afd0 Follow the instructions in the src/INSTALL file. Note that this version will install the client libraries and header files in a non-standard place, /usr/local/lib and /usr/local/include. The src/INSTALL file describes what is being installed and where. When you install release 4.9.6 first, its client, server, and tools parts will be installed in the production locations. When you then install release 8.1.1, the server and tools parts will be overwritten by that release's versions, but the 4.9.6 client part will not. 2. No Shared Object Client Subroutine Library If you do not need the shared object client subroutine library, then you need only upgrade to release 8.1.1. This software is available at ftp://ftp.isc.org/isc/bind/src/8.1.1/bind-src.tar.gz MD5 (bind-src.tar.gz) = 7487b8d647edba2053edc1cda0c6afd0 Follow the instructions in src/INSTALL. Note that the client subroutine library and header files are installed in /usr/local/lib and /usr/local/include respectively. To use these when building other systems, you will need to refer to their installed locations. Note: ftp://ftp.isc.org/isc/bind/src/ is mirrored in Germany at ftp://ftp.cert.dfn.de/pub/tools/net/bind/src/ As new versions of BIND are released in the future, you will be able to find them at these sites, as well as other mirrors. You can also check ftp://info.cert.org/pub/latest_sw_versions/ for version information. C. Take additional precautions. As good security practice in general, filter at a router all name-based authentication services so that you do not rely on DNS information for authentication. This includes the services rlogin, rsh (rcp), xhost, NFS, and any other locally installed services that provide trust based on domain name information. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 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. Cray Research - A Silicon Graphics Company =========================================== Cray Research has determined that the version of BIND shipped with all current releases of Unicos and Unicos/mk are susceptible to the problem described in this advisory. We are currently working on upgrading our version of BIND to the 4.9.6 release. Digital Equipment Corporation ============================= xref CASE ID: SSRT0494U At the time of writing this document, patches(binary kits) are in progress and final patch testing is expected to begin soon. Digital will provide notice of the completion/availability of the patches through AES services (DIA, DSNlink FLASH) and be available from your normal Digital Support channel. DIGITAL EQUIPMENT CORPORATION AUG/97 ----------------------------- ------ Hewlett-Packard Company ======================= HP is vulnerable. Patches in process. IBM Corporation =============== IBM is currently working on the following APARs which will be available soon: AIX 4.1: IX70236 AIX 4.2: IX70237 To Order -------- APARs may be ordered using Electronic Fix Distribution (via FixDist) or from the IBM Support Center. For more information on FixDist, reference URL: http://service.software.ibm.com/aixsupport/ or send e-mail to aixserv@austin.ibm.com with a subject of "FixDist". IBM and AIX are registered trademarks of International Business Machines Corporation. NEC Corporation =============== NEC is vulnerable. The systems affected by this problem are as follows: UX/4800 UX/4800(64) EWS-UX/V(Rel4.2MP) EWS-UX/V(Rel4.2) UP-UX/V(Rel4.2MP) Patches are in progress and will be made available from ftp://ftp.meshnet.or.jp/pub/48pub/security. Siemens-Nixdorf Informationssysteme AG ====================================== We are investigating this problem and will provide updated information for this advisory when it becomes available. The Santa Cruz Operation ======================== The following SCO operating systems are vulnerable: - SCO Open Desktop/Open Server 3.0, SCO UNIX 3.2v4 - SCO OpenServer 5.0 - SCO UnixWare 2.1 SCO CMW+ 3.0 is not vulnerable as bind is not supported on CMW+ platforms. SCO has made an interim fix available for anonymous ftp: ftp://ftp.sco.com/SSE/sse008.ltr.Z - cover letter ftp://ftp.sco.com/SSE/sse008.tar.Z - replacement binaries The fix includes binaries for the following SCO operating systems: - SCO Open Desktop/Open Server 3.0, SCO UNIX 3.2v4 - SCO OpenServer 5.0 - SCO UnixWare 2.1 Sun Microsystems, Inc. ====================== We are producing patches. - ----------------------------------------------------------------------------- The CERT Coordination Center staff thanks Paul Vixie and Wolfgang Ley for their contributions to 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 - ---------------------------------------------------------------------------- Copyright 1997 Carnegie Mellon University. Conditions apply; they can be found in http://www.cert.org/legal_stuff.html and ftp://info.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. - --------------------------------------------------------------------------- This file: ftp://info.cert.org/pub/cert_advisories/CA-97.22.bind http://www.cert.org click on "CERT Advisories" ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Revision history [End CERT Advisory] ______________________________________________________________________________ CIAC wishes to acknowledge the contributions of CERT for the information contained in this bulletin. ______________________________________________________________________________ CIAC, the Computer Incident Advisory Capability, is the computer security incident response team for the U.S. Department of Energy (DOE) and the emergency backup response team for the National Institutes of Health (NIH). CIAC is located at the Lawrence Livermore National Laboratory in Livermore, California. CIAC is also a founding member of FIRST, the Forum of Incident Response and Security Teams, a global organization established to foster cooperation and coordination among computer security teams worldwide. CIAC services are available to DOE, DOE contractors, and the NIH. CIAC can be contacted at: Voice: +1 510-422-8193 FAX: +1 510-423-8002 STU-III: +1 510-423-2604 E-mail: ciac@llnl.gov For emergencies and off-hour assistance, DOE, DOE contractor sites, and the NIH may contact CIAC 24-hours a day. During off hours (5PM - 8AM PST), call the CIAC voice number 510-422-8193 and leave a message, or call 800-759-7243 (800-SKY-PAGE) to send a Sky Page. CIAC has two Sky Page PIN numbers, the primary PIN number, 8550070, is for the CIAC duty person, and the secondary PIN number, 8550074 is for the CIAC Project Leader. Previous CIAC notices, anti-virus software, and other information are available from the CIAC Computer Security Archive. World Wide Web: http://ciac.llnl.gov/ Anonymous FTP: ciac.llnl.gov (198.128.39.53) Modem access: +1 (510) 423-4753 (28.8K baud) +1 (510) 423-3331 (28.8K baud) CIAC has several self-subscribing mailing lists for electronic publications: 1. CIAC-BULLETIN for Advisories, highest priority - time critical information and Bulletins, important computer security information; 2. CIAC-NOTES for Notes, a collection of computer security articles; 3. SPI-ANNOUNCE for official news about Security Profile Inspector (SPI) software updates, new features, distribution and availability; 4. SPI-NOTES, for discussion of problems and solutions regarding the use of SPI products. Our mailing lists are managed by a public domain software package called Majordomo, which ignores E-mail header subject lines. 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If you are not part of these communities, please contact your agency's response team to report incidents. Your agency's team will coordinate with CIAC. The Forum of Incident Response and Security Teams (FIRST) is a world-wide organization. A list of FIRST member organizations and their constituencies can be obtained via WWW at http://www.first.org/. This document was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor the University of California nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. 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LAST 10 CIAC BULLETINS ISSUED (Previous bulletins available from CIAC) H-86: ld.so Vulnerability H-87: HP-UX rlogin Vulnerability H-88: SGI IRIX talkd Vulnerability H-89: SunSO talkd Buffer Overrun Vulnerability H-90: SunOS, Solaris NIS+ Vulnerability H-91: HP-UX Large UID's and GID's Vulnerability H-92: HP-UX X11/Motif Lib & Novell Netware Vulerabilities H-93: SGI IRIX ordist Buffer Overrun Vulnerability H-94: SunOS Vulnerability in ps H-95: SunOS Vulnerability in x-lock -----BEGIN PGP SIGNATURE----- Version: 4.0 Business Edition iQCVAwUBM/SEh7nzJzdsy3QZAQGg0AP+Nq1twg0ExWg/s0FuJ30Q3aA5f1rZ6H0/ hkWkIh6WMOlbkLhGstboRKpr+nn3Lm06mNlbKCGDrEEpL3gxWSldNRTapXHW2bJM TlajsNj7idUhAtFZPtUQIJE1GzZpUEsoZG91k8oU4FgWO+FNNjEJxJW3WtGwGkW/ a3VHqySP93c= =GZ5b -----END PGP SIGNATURE-----