-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 ============================================================================= FreeBSD-SA-08:06.bind Security Advisory The FreeBSD Project Topic: DNS cache poisoning Category: contrib Module: bind Announced: 2008-07-13 Credits: Dan Kaminsky Affects: All supported FreeBSD versions. Corrected: 2008-07-12 10:07:33 UTC (RELENG_6, 6.3-STABLE) 2008-07-13 18:42:38 UTC (RELENG_6_3, 6.3-RELEASE-p3) 2008-07-13 18:42:38 UTC (RELENG_7, 7.0-STABLE) 2008-07-13 18:42:38 UTC (RELENG_7_0, 7.0-RELEASE-p3) CVE Name: CVE-2008-1447 For general information regarding FreeBSD Security Advisories, including descriptions of the fields above, security branches, and the following sections, please visit . I. Background BIND 9 is an implementation of the Domain Name System (DNS) protocols. The named(8) daemon is an Internet Domain Name Server. DNS requests contain a query id which is used to match a DNS request with the response and to make it harder for anybody but the DNS server which received the request to send a valid response. II. Problem Description The BIND DNS implementation does not randomize the UDP source port when doing remote queries, and the query id alone does not provide adequate randomization. III. Impact The lack of source port randomization reduces the amount of data the attacker needs to guess in order to successfully execute a DNS cache poisoning attack. This allows the attacker to influence or control the results of DNS queries being returned to users from target systems. IV. Workaround Limiting the group of machines that can do recursive queries on the DNS server will make it more difficult, but not impossible, for this vulnerability to be exploited. To limit the machines able to perform recursive queries, add an ACL in named.conf and limit recursion like the following: acl example-acl { 192.0.2.0/24; }; options { recursion yes; allow-recursion { example-acl; }; }; V. Solution Perform one of the following: 1) Upgrade your vulnerable system to 6-STABLE or 7-STABLE, or to the RELENG_7_0 or RELENG_6_3 security branch dated after the correction date. 2) To patch your present system: The following patches have been verified to apply to FreeBSD 6.3 and 7.0 systems. a) Download the relevant patch from the location below, and verify the detached PGP signature using your PGP utility. [FreeBSD 6.3] # fetch http://security.FreeBSD.org/patches/SA-08:06/bind63.patch # fetch http://security.FreeBSD.org/patches/SA-08:06/bind63.patch.asc [FreeBSD 7.0] # fetch http://security.FreeBSD.org/patches/SA-08:06/bind7.patch # fetch http://security.FreeBSD.org/patches/SA-08:06/bind7.patch.asc b) Execute the following commands as root: # cd /usr/src # patch < /path/to/patch # cd /usr/src/lib/bind # make obj && make depend && make && make install # cd /usr/src/usr.sbin/named # make obj && make depend && make && make install NOTE WELL: This update causes BIND to choose a new, random UDP port for each new query; this may cause problems for some network configurations, particularly if firewall(s) block incoming UDP packets on particular ports. The avoid-v4-udp-ports and avoid-v6-udp-ports options should be used to avoid selecting random port numbers within a blocked range. NOTE WELL: If a port number is specified via the query-source or query-source-v6 options to BIND, randomized port selection will not be used. Consequently it is strongly recommended that these options not be used to specify fixed port numbers. VI. Correction details The following list contains the revision numbers of each file that was corrected in FreeBSD. Branch Revision Path - ------------------------------------------------------------------------- RELENG_6 src/contrib/bind9/bin/named/client.c 1.1.1.2.2.5 src/contrib/bind9/bin/named/server.c 1.1.1.2.2.4 src/contrib/bind9/lib/dns/api 1.1.1.2.2.5 src/contrib/bind9/lib/dns/dispatch.c 1.1.1.1.4.4 src/contrib/bind9/lib/dns/include/dns/dispatch.h 1.1.1.1.4.3 src/contrib/bind9/lib/dns/resolver.c 1.1.1.2.2.8 RELENG_6_3 src/UPDATING 1.416.2.37.2.8 src/sys/conf/newvers.sh 1.69.2.15.2.7 src/contrib/bind9/bin/named/client.c 1.1.1.2.2.3.2.1 src/contrib/bind9/bin/named/server.c 1.1.1.2.2.2.2.1 src/contrib/bind9/lib/dns/api 1.1.1.2.2.3.2.1 src/contrib/bind9/lib/dns/dispatch.c 1.1.1.1.4.2.2.1 src/contrib/bind9/lib/dns/include/dns/dispatch.h 1.1.1.1.4.1.2.1 src/contrib/bind9/lib/dns/resolver.c 1.1.1.2.2.6.2.1 RELENG_7 src/contrib/bind9/bin/named/client.c 1.1.1.6.2.2 src/contrib/bind9/bin/named/server.c 1.1.1.6.2.2 src/contrib/bind9/lib/dns/api 1.1.1.6.2.2 src/contrib/bind9/lib/dns/dispatch.c 1.1.1.4.2.2 src/contrib/bind9/lib/dns/include/dns/dispatch.h 1.1.1.3.2.2 src/contrib/bind9/lib/dns/resolver.c 1.1.1.9.2.2 RELENG_7_0 src/UPDATING 1.507.2.3.2.7 src/sys/conf/newvers.sh 1.72.2.5.2.7 src/contrib/bind9/bin/named/client.c 1.1.1.6.2.1.2.1 src/contrib/bind9/bin/named/server.c 1.1.1.6.2.1.2.1 src/contrib/bind9/lib/dns/api 1.1.1.6.2.1.2.1 src/contrib/bind9/lib/dns/dispatch.c 1.1.1.4.2.1.2.1 src/contrib/bind9/lib/dns/include/dns/dispatch.h 1.1.1.3.2.1.2.1 src/contrib/bind9/lib/dns/resolver.c 1.1.1.9.2.1.2.1 - ------------------------------------------------------------------------- VII. References http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2008-1447 http://www.kb.cert.org/vuls/id/800113 The latest revision of this advisory is available at http://security.FreeBSD.org/advisories/FreeBSD-SA-08:06.bind.asc -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.9 (FreeBSD) iEYEARECAAYFAkh6UiMACgkQFdaIBMps37IE5ACfYzpWMhEXgWNdjwVlzd7JTwBS Eu0AnRIogMIJ3fjQF4hcymtdwR6buRNc =shnR -----END PGP SIGNATURE-----