************************************************************************** Security Bulletin 9722 DISA Defense Communications System September 9, 1997 Published by: DISN Security Coordination Center (SCC@NIC.MIL) 1-(800) 365-3642 DEFENSE INFORMATION SYSTEM NETWORK SECURITY BULLETIN The DISN SECURITY BULLETIN is distributed by the DISN SCC (Security Coordination Center) under DISA contract as a means of communicating information on network and host security exposures, fixes, and concerns to security and management personnel at DISN facilities. Back issues may be obtained via FTP from NIC.MIL [207.132.116.5] using login= "anonymous" and password="guest". The bulletin pathname is scc/sec-yynn (where "yy" is the year the bulletin is issued and "nn" is a bulletin number, e.g. scc/sec-9705.txt). These are also available at our WWW site, http://nic.mil. ************************************************************************** + - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - + ! ! ! The following important advisory was issued by the Automated ! ! Systems Security Incident Support Team (ASSIST) and is being ! ! relayed unedited via the Defense Information Systems Agency's ! ! Security Coordination Center distribution system as a means ! ! of providing DISN subscribers with useful security information. ! ! ! + - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - + -----BEGIN PGP SIGNED MESSAGE----- <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> Automated Systems Security Incident Support Team _____ ___ ___ _____ ___ _____ | / /\ / \ / \ | / \ | | / Integritas / \ \___ \___ | \___ | | < et /____\ \ \ | \ | | \ Celeritas / \ \___/ \___/ __|__ \___/ | |_____\ <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> ADVISORY: 97-11 Release date: 08 Sep 1997 DESCRIPTION: Berkeley Internet Name Daemon (BIND) Vulnerability PLATFORM: Mostly UNIX systems. See list below IMPACT: Protocols relying on DNS resolution for authentication purposes are unreliable. These protocols include, but not limited to rsh, rlogin, NFS, etc. This vulnerability is actively being exploited. SOLUTIONS: Apply fixes mentioned in Section III as soon as possible. [ Beginning of CERT Bulletin ] ============================================================================= CERT* Advisory CA-97.22 Original issue date: August 13, 1997 Last revised: August 20, 1997 Introduction - Clarified that 4.9.6 is not vulnerable. Section III - Added a note why sites should upgrade to 8.1.1. 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). The vulnerability has been fixed in BIND version 4.9.6; however, we recommend upgrading according to our instructions in Section III.B or installing vendor patches (see Appendix A). 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 Install a patch from your vendor or implement the "best practice" workaround we recommend in Section III.B. In either case, take the extra precautions described in Section III.C. 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. Note: Although the security posture in BIND version 8.1.1 is identical to that of version 4.9.6, version 8.1.1 is the version that will continue to undergo changes and improvements, hence our selection of its use as the "best practice." 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. [ End of CERT Bulletin ] - ----------------------------------------------------------------------------- The ASSIST staff would like to thank the CERT Coordination Center for this advisory, as well as Paul Vixie and Wolfgang Ley for their contributions to this advisory. - ----------------------------------------------------------------------------- <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> ASSIST is an element of the Defense Information Systems Agency (DISA), Global Operations and Security Center (GOSC), which provides service to the entire DoD community. 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