-----BEGIN PGP SIGNED MESSAGE----- NetBSD Security Advisory 2002-006 ================================= (updated 2002/9/16) Topic: buffer overrun in libc/libresolv DNS resolver Version: NetBSD-current: source prior to June 28, 2002 NetBSD-1.6 beta:source prior to June 28, 2002 NetBSD-1.5.3: NOT affected NetBSD-1.5.2: affected NetBSD-1.5.1: affected NetBSD-1.5: affected NetBSD-1.4.*: affected All prior NetBSD releases. pkgsrc: net/bind4, prior to bind-4.9.9 are affected net/bind8, prior to bind-8.3.3 are affected net/bind9, bind-9.2.1 includes vulnerable code (not compiled for normal use) emulators/compat14 prior to 1.4.3.2 emulators/compat14-crypto prior to 1.4.3.2 emulators/netbsd32_compat14 prior to 1.4.3.2 emulators/compat15 prior to 1.5.3.1 if ships with libc/libresolv shlib emulators/netbsd32_compat15 prior to 1.5.3.1 emulators/* for other operating systems, if ships with libc/libresolv shlib any statically linked pkgsrc binaries (there could be more) Severity: remote buffer overrun on any application that uses DNS, possible remote root exploit (not confirmed) Fixed: NetBSD-current: June 28, 2002 NetBSD-1.6 branch: June 28, 2002 (1.6 includes the fix) NetBSD-1.5 branch: July 2, 2002 (1.5.3 includes the fix) NetBSD-1.4 branch: (not yet) pkgsrc: net/bind4, bind-4.9.8nb1 net/bind8, bind-8.3.3 net/bind9, (ISC is not planning a release, as vulnerable files are not used in the main server or utilites by default.) emulators/compat14 1.4.3.2 emulators/compat14-crypto 1.4.3.2 emulators/netbsd32_compat14 1.4.3.2 emulators/compat15 1.5.3.1 emulators/netbsd32_compat15 1.5.3.1 emulators/* for other operating systems - not yet NOTE: previous revisions of the advisory noted that fixed date was June 26. Since BIND8 was later found to also be vulnerable, the fixed date for NetBSD-current was moved to Jun 28, and branches for which pullups have not yet been completed or updated to distribution sites have been changed to (not yet). If you have upgraded your system on June 26, you will need to upgrade again. Thank you for your patience with this complex issue. NOTE: previous revisions of the advisory noted that the use of BIND9 as caching resolver would work around the problem. However, it was later found to be insufficient (CERT advisory CA-2002-19 got updated on 2002/8/28 for this). Therefore, the only fix to this problem is to upgrade your resolver library and any static binaries. Abstract ======== There was a buffer-length computation bug in BIND-based DNS resolver code. A malicious DNS response packet may be able to overwrite data outside the buffer, and it could lead to attacks as serious as a remote root exploit, though there are no public exploits in circulation at this time. NetBSD uses BIND4-based DNS resolver code in libc/libresolv, and is found to be vulnerable. We also use BIND8-based DNS resolver code in named related tools like /usr/bin/dig, and these are vulnerable (source located in dist/bind and usr.sbin/bind). Technical Details ================= In lib/libc/net/gethnamaddr.c:getanswer() and lib/libc/net/getnetnamadr.c:getnetanswer(), two variables manage packet buffer parsing - a pointer to the byte we are looking at, and the remaining length on the buffer. The remaining length was not updated consistently, and malicious DNS responses are able to write outside the buffer. This may present an attacker with the opportunity to insert arbitrary code for execution as the user running the resolver query, potentially root. No exploit script to take advantage of this vulnerability is known at time of writing. It is important to understand that this issue can be triggered in a manner unlike the more common buffer overflows in network daemons. Any outgoing DNS query made to a hostile server would expose the vulnerability. The exploit path includes email sent to Netscape users which automatically display HTML, and hostile web pages which carry embedded objects located on servers in domains with a hostile DNS server. Since client systems in many network environments are permitted to make DNS queries directly to root servers, through routed IPs, or NATs, realize that these systems are vulnerable even if behind a firewall, since they are initiating the outgoing query. This issue was brought to the attention of the NetBSD security-officer with short notice, and this advisory has since been updated with additional information. See also: http://www.pine.nl/advisories/pine-cert-20020601.html http://www.kb.cert.org/vuls/id/803539 http://www.cert.org/advisories/CA-2002-19.html (revised 2002/8/28) Solutions and Workarounds ========================= The recent NetBSD 1.5.3 release is not vulnerable to this issue, however very shortly after its release other vulnerabilities were found. Please ensure you check all relevant Security Advisories. The recent NetBSD 1.6 release is not vulnerable to this issue. A full upgrade to NetBSD 1.6 is the recommended resolution for all users able to do so. Many security-related improvements have been made, and indeed this release has been delayed several times in order to include fixes for a number of recent issues. Note that any statically-linked binary that makes any DNS query is vulnerable, and cannot be fixed by replacing a shared library. Therefore, updating the entire system is suggested. Note also that shared libraries from other operating systems installed for binary compatibility under /emul may also be vulnerable. Please consult the vendor of those libraries for further details. If you have NetBSD systems that have been upgraded from earlier releases from before 1997, you may have libc and/or libresolv shared libraries with older shared library major numbers. Check for the presence of /usr/lib/libc.so.X.Y where X < 12 (the current major number). These old libraries contain vulnerable resolver code, and will not be updated even if you rebuild the system. Therefore, we suggest you to remove those old shared libraries. * NetBSD-current: Systems running NetBSD-current dated from before 2002-06-25 should be upgraded to NetBSD-current dated 2002-06-26 or later. The following directories need to be updated from the netbsd-current CVS branch (aka HEAD): lib/libc/net usr.sbin/bind dist/bind Also note that the include files needs to be in sync with code in lib/libc/net. To update from CVS, re-build, and re-install libc and statically linked binaries: # cd src # cvs update -d -P lib/libc/net usr.sbin/bind dist/bind # cd lib/libc # make cleandir dependall # make install # cd ../../lib/libresolv # make cleandir dependall # make install # cd ../.. # make dependall # make install * NetBSD 1.6 betas: Systems running NetBSD 1.6 BETAs and Release Candidates should be upgraded to the NetBSD 1.6 release. If a source-based point upgrade is required, sources from the NetBSD 1.6 branch dated 2002-06-26 or later should be used. The following directories need to be updated from the netbsd-1-6 CVS branch: lib/libc/net usr.sbin/bind dist/bind Also note that the include files needs to be in sync with code in lib/libc/net. To update from CVS, re-build, and re-install libc and statically linked binaries: # cd src # cvs update -d -P -r netbsd-1-6 lib/libc/net \ usr.sbin/bind dist/bind # cd lib/libc # make cleandir dependall # make install # cd ../../lib/libresolv # make cleandir dependall # make install # cd ../.. # make dependall # make install * NetBSD 1.5.x: Systems running NetBSD 1.5.x dated from before 2002-06-25 should be upgraded to NetBSD 1.5 tree dated 2002-06-26 or later. The following directories need to be updated from the netbsd-1-5 CVS branch: lib/libc/net usr.sbin/bind dist/bind Also note that the include files needs to be in sync with code in lib/libc/net. To update from CVS, re-build, and re-install libc and statically linked binaries: # cd src # cvs update -d -P -r netbsd-1-5 lib/libc/net \ usr.sbin/bind dist/bind # cd lib/libc # make cleandir dependall # make install # cd ../../lib/libresolv # make cleandir dependall # make install # cd ../.. # make dependall # make install * NetBSD 1.4.x: Systems running NetBSD 1.4.x dated from before 2002-06-25 should be upgraded to NetBSD 1.4 tree dated 2002-06-26 or later. The following directories need to be updated from the netbsd-1-4 CVS branch: lib/libc/net usr.sbin/bind dist/bind To update from CVS, re-build, and re-install libc and statically linked binaries: # cd src # cvs update -d -P -r netbsd-1-4 lib/libc/net \ usr.sbin/bind dist/bind # cd lib/libc # make cleandir dependall # make install # cd ../../lib/libresolv # make cleandir dependall # make install # cd ../.. # make dependall # make install * pkgsrc: bind-4.9.8 (pkgsrc/net/bind4) and prior are vulnerable. Upgrade to bind-4.9.8nb1 or bind-4.9.9. Note that BIND4 nameserver is considered obsolete by the vendor (ISC), and it is recommended to use BIND9, or BIND8. pkgsrc prior to bind-8.3.3 are vulnerable. Upgrade to bind-8.3.3. bind-9.2.1 includes vulnerable code, however, the code will not be compiled by default. Shared libraries in compat1[234]-* (pkgsrc/emulators/compat1[234]) are vulnerable. There is no fix supplied at this moment. If you have statically linked binaries in pkgsrc, they have to be rebuilt. Statically linked binaries can be identified by the following command (note: be sure to include the directory you install pkgsrc binaries to, if you've changed LOCALBASE from the default of /usr/pkg) file /usr/pkg/{bin,sbin,libexec} | grep static Shared libraries for binary compatibility are available through pkgsrc for some operating systems, and may be vulnerable as noted above if installed. Thanks To ========= Jun-ichiro itojun Hagino for patches, and initial advisory text. Michael Graff for bind9 information The NetBSD Release Engineering teams, for great patience and assistance in dealing with repeated security issues discovered recently. Revision History ================ 2002-06-26 Initial release 2002-06-27 Updated with further information on pkgsrc, and affected BIND releases. 2002-06-28 Add note from Michael Graff regarding BIND9 2002-06-28 BIND8 resolver (dist/bind) was found to be vulnerable. Fixed date changed from Jun 26 to Jun 28. 2002-08-28 Remove note regarding BIND9, as it was found to be insufficient. 2002-09-05 Updated information regarding recent 1.5.3 release and emulation pkgsrc. 2002-09-16 Re-release with updated information More Information ================ An up-to-date PGP signed copy of this release will be maintained at ftp://ftp.netbsd.org/pub/NetBSD/security/advisories/NetBSD-SA2002-006.txt.asc Information about NetBSD and NetBSD security can be found at http://www.NetBSD.ORG/ and http://www.NetBSD.ORG/Security/. Copyright 2002, The NetBSD Foundation, Inc. All Rights Reserved. $NetBSD: NetBSD-SA2002-006.txt,v 1.40 2002/09/16 05:17:55 dan Exp $ -----BEGIN PGP SIGNATURE----- Version: 2.6.3ia Charset: noconv iQCVAwUBPYVpoD5Ru2/4N2IFAQGFOgP/UTJeXuOgFiB81myMTeTgeRc1H7u41W+q nW/TJGltzApfFQJjZYDDj3TC7AfTLBFWwfrJynC4jsLFUMIcs5NMZOvWE2eiCTgz S7QJi15B07nMfipYe3s9dJ3QQZB9YIZng1lNVa7V7Ee1fPrYt5oXHkrZfCZTOLKL zd3yMAAQRpg= =8/IS -----END PGP SIGNATURE-----
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