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FreeBSD Security Advisory - named Denial Of Service

FreeBSD Security Advisory - named Denial Of Service
Posted Aug 8, 2012
Authored by Einar Lonn | Site security.freebsd.org

FreeBSD Security Advisory - BIND 9 stores a cache of query names that are known to be failing due to misconfigured name servers or a broken chain of trust. Under high query loads, when DNSSEC validation is active, it is possible for a condition to arise in which data from this cache of failing queries could be used before it was fully initialized, triggering an assertion failure. A remote attacker that is able to generate high volume of DNSSEC validation enabled queries can trigger the assertion failure that causes it to crash, resulting in a denial of service.

tags | advisory, remote, denial of service
systems | freebsd
advisories | CVE-2012-3817
SHA-256 | 14ce0ceb3dfdd72660f83035bfda8974a44d0c866f0212093a308b810aac8df9

FreeBSD Security Advisory - named Denial Of Service

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Hash: SHA1

=============================================================================
FreeBSD-SA-12:05.bind Security Advisory
The FreeBSD Project

Topic: named(8) DNSSEC validation Denial of Service

Category: contrib
Module: bind
Announced: 2012-08-06
Credits: Einar Lonn of IIS.se
Affects: All supported versions of FreeBSD
Corrected: 2012-08-06 21:33:11 UTC (RELENG_7, 7.4-STABLE)
2012-08-06 21:33:11 UTC (RELENG_7_4, 7.4-RELEASE-p10)
2012-07-24 19:04:35 UTC (RELENG_8, 8.3-STABLE)
2012-08-06 21:33:11 UTC (RELENG_8_3, 8.3-RELEASE-p4)
2012-08-06 21:33:11 UTC (RELENG_8_2, 8.2-RELEASE-p10)
2012-08-06 21:33:11 UTC (RELENG_8_1, 8.1-RELEASE-p13)
2012-07-24 22:32:03 UTC (RELENG_9, 9.1-PRERELEASE)
2012-08-06 21:33:11 UTC (RELENG_9_0, 9.0-RELEASE-p4)
CVE Name: CVE-2012-3817

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

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 Security Extensions (DNSSEC) provides data integrity, origin
authentication and authenticated denial of existence to resolvers.

II. Problem Description

BIND 9 stores a cache of query names that are known to be failing due
to misconfigured name servers or a broken chain of trust. Under high
query loads, when DNSSEC validation is active, it is possible for a
condition to arise in which data from this cache of failing queries
could be used before it was fully initialized, triggering an assertion
failure.

III. Impact

A remote attacker that is able to generate high volume of DNSSEC
validation enabled queries can trigger the assertion failure that causes
it to crash, resulting in a denial of service.

IV. Workaround

No workaround is available, but systems not running the BIND resolving
name server with dnssec-validation enabled are not affected.

V. Solution

Perform one of the following:

1) Upgrade your vulnerable system to 7-STABLE, 8-STABLE, or 9-STABLE,
or to the RELENG_7_4, RELENG_8_3, RELENG_8_2, RELENG_8_1, or RELENG_9_0
security branch dated after the correction date.

2) To update your vulnerable system via a source code patch:

The following patches have been verified to apply to FreeBSD 7.4,
8.3, 8.2, 8.1 and 9.0 systems.

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

# fetch http://security.FreeBSD.org/patches/SA-12:05/bind.patch
# fetch http://security.FreeBSD.org/patches/SA-12:05/bind.patch.asc

b) Execute the following commands as root:

# cd /usr/src
# patch < /path/to/patch
# cd /usr/src/lib/bind/dns
# make obj && make depend && make && make install
# cd /usr/src/usr.sbin/named
# make obj && make depend && make && make install

3) To update your vulnerable system via a binary patch:

Systems running 7.4-RELEASE, 8.3-RELEASE, 8.2-RELEASE, 8.1-RELEASE,
or 9.0-RELEASE on the i386 or amd64 platforms can be updated via the
freebsd-update(8) utility:

# freebsd-update fetch
# freebsd-update install

4) Install and run BIND from the Ports Collection after the correction
date. The following versions and newer versions of BIND installed from
the Ports Collection are not affected by this vulnerability:

bind96-9.6.3.1.ESV.R7.2
bind97-9.7.6.2
bind98-9.8.3.2
bind99-9.9.1.2

VI. Correction details

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

CVS:

Branch Revision
Path
- -------------------------------------------------------------------------
RELENG_7
src/contrib/bind9/lib/dns/resolver.c 1.1.1.9.2.11
RELENG_7_4
src/UPDATING 1.507.2.36.2.12
src/sys/conf/newvers.sh 1.72.2.18.2.15
src/contrib/bind9/lib/dns/resolver.c 1.1.1.9.2.8.2.1
RELENG_8
src/contrib/bind9/CHANGES 1.9.2.15
src/contrib/bind9/lib/dns/resolver.c 1.3.2.6
src/contrib/bind9/lib/dns/zone.c 1.6.2.10
src/contrib/bind9/lib/isc/random.c 1.2.2.4
src/contrib/bind9/version 1.9.2.15
RELENG_8_3
src/UPDATING 1.632.2.26.2.6
src/sys/conf/newvers.sh 1.83.2.15.2.8
src/contrib/bind9/lib/dns/resolver.c 1.6.2.7.2.1
RELENG_8_2
src/UPDATING 1.632.2.19.2.12
src/sys/conf/newvers.sh 1.83.2.12.2.15
src/contrib/bind9/lib/dns/resolver.c 1.6.2.4.2.1
RELENG_8_1
src/UPDATING 1.632.2.14.2.16
src/sys/conf/newvers.sh 1.83.2.10.2.17
src/contrib/bind9/lib/dns/resolver.c 1.6.2.3.2.1
RELENG_9
src/contrib/bind9/CHANGES 1.21.2.5
src/contrib/bind9/lib/dns/resolver.c 1.15.2.3
src/contrib/bind9/lib/dns/zone.c 1.7.2.3
src/contrib/bind9/version 1.21.2.5
RELENG_9_0
src/UPDATING 1.702.2.4.2.6
src/sys/conf/newvers.sh 1.95.2.4.2.8
src/contrib/bind9/lib/dns/resolver.c 1.15.4.1
- -------------------------------------------------------------------------

Subversion:

Branch/path Revision
- -------------------------------------------------------------------------
stable/7/ r239108
releng/7.4/ r239108
stable/8/ r238749
releng/8.3/ r239108
releng/8.2/ r239108
releng/8.1/ r239108
stable/9/ r238756
releng/9.0/ r239108
- -------------------------------------------------------------------------

VII. References

https://kb.isc.org/article/AA-00729

http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2012-3817

The latest revision of this advisory is available at
http://security.FreeBSD.org/advisories/FreeBSD-SA-12:05.bind.asc
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