Topic: BIND 9 DNSSEC remote denial of service vulnerability

Category: core
Module: bind9
Announced: 2005-06-09
Credits: Internet Systems Consortium
Affects: FreeBSD 5.3
Corrected: 2005-03-23 18:16:29 UTC (RELENG_5, 5.3-STABLE)
2005-06-08 21:29:15 UTC (RELENG_5_3, 5.3-RELEASE-p16)
CVE Name: CAN-2005-0034

For general information regarding FreeBSD Security Advisories,
including descriptions of the fields above, security branches, and the
following sections, please visit
http://www.freebsd.org/security/>.

I. Background

BIND 9 is an implementation of the Domain Name System (DNS) protocols.
The named(8) daemon is the Internet domain name server. DNS Security
Extensions (DNSSEC) are additional protocol options that add
authentication and integrity to the DNS protocols.

DNSSEC is not enabled by default in any FreeBSD release. A system
administrator must take special action to enable DNSSEC.

II. Problem Description

A DNSSEC-related validator function in BIND 9.3.0 contains an
inappropriate internal consistency test. When this test is triggered,
named(8) will exit.

III. Impact

On systems with DNSSEC enabled, a remote attacker may be able to inject
a specially crafted packet that will cause the internal consistency test
to trigger, and named(8) to terminate. As a result, the name server
will no longer be available to service requests.

IV. Workaround

DNSSEC is not enabled by default, and the "dnssec-enable" directive is
not normally present. If DNSSEC has been enabled, disable it by
changing the "dnssec-enable" directive to "dnssec-enable no;" in the
named.conf(5) configuration file.

V. Solution

Perform one of the following:

1) Upgrade your vulnerable system to 5-STABLE, or to the RELENG_5_3
security branch dated after the correction date.

2) To patch your present system:

The following patches have been verified to apply to FreeBSD 5.3
systems.

a) Download the relevant patch from the location below, and verify the
detached PGP signature using your PGP utility.

# fetch ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-05:12/bind9.patch
# fetch ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-05:12/bind9.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

VI. Correction details

The following list contains the revision numbers of each file that was
corrected in FreeBSD.

Branch Revision
Path
- -------------------------------------------------------------------------
RELENG_5
src/contrib/bind9/lib/dns/validator.c 1.1.1.1.2.2
RELENG_5_3
src/UPDATING 1.342.2.13.2.19
src/sys/conf/newvers.sh 1.62.2.15.2.21
src/contrib/bind9/lib/dns/validator.c 1.1.1.1.2.1.2.1
- -------------------------------------------------------------------------

VII. References

http://cve.mitre.org/cgi-bin/cvename.cgi?name=CAN-2005-0034
http://www.kb.cert.org/vuls/id/938617
http://www.isc.org/index.pl?/sw/bind/bind-security.php
http://www.isc.org/index.pl?/sw/bind/bind9.php

The latest revision of this advisory is available at
ftp://ftp.freebsd.org/pub/FreeBSD/CERT/advisories/FreeBSD-SA-05:12.bind9.asc