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		 NetBSD Security Advisory 2003-018
		 =================================

Topic:		DNS negative cache poisoning

Version:	NetBSD-current:	source prior to Nov 27, 2003
		NetBSD 1.6.2_RC3:	not affected
		NetBSD 1.6.2_RC2:	affected
		NetBSD 1.6.2_RC1:	affected
		NetBSD 1.6:		affected
		NetBSD-1.5.3:		affected
		NetBSD-1.5.2:		affected
		NetBSD-1.5.1:		affected
		NetBSD-1.5:		affected
		pkgsrc:			bind8 packages prior to 8.4.3
					bind9 packages unaffected

Severity:	Denial of service resolving DNS entries

Fixed:		NetBSD-current:		Nov 27, 2003
		NetBSD-1.6 branch:	Nov 28, 2003 (1.6.2 will include the fix)
						     (1.6.2_RC3 includes the fix)
		NetBSD-1.5 branch:	Nov 28, 2003
		pkgsrc bind8:		bind8-8.4.3 will correct this issue


Abstract
========

If an attacker can trigger your DNS server to do a lookup via a server
he controls, the malign server can inject authoritative negative
responses with long time to live values. Your DNS server will cache the
lie that the relevant resource records do not exist.


Technical Details
=================

- From CERT VU#734644:
http://www.kb.cert.org/vuls/id/734644

Several versions of the BIND 8 name server are vulnerable to cache
poisoning via negative responses. To exploit this vulnerability, an
attacker must configure a name server to return authoritative negative
responses for a given target domain. Then, the attacker must convince a
victim user to query the attacker's maliciously configured name server.
When the attacker's name server receives the query, it will reply with
an authoritative negative response containing a large TTL (time-to-live)
value. If the victim's site runs a vulnerable version of BIND 8, it will
cache the negative response and render the target domain unreachable
until the TTL expires.


NOTE: While ISC released two patch versions for this vulunerability
(8.3.7 and 8.4.3) a query-storm bug has been discovered in the 8.4.3
version. The 8.3.7 version which currently ships as part of NetBSD does
not have this bug. ISC recommends against moving production servers to
8.4.3


Solutions and Workarounds
=========================


If you are not running named(8), your system is not affected.

BIND 9 is not affected by these vulnerabilities.  Upgrading to BIND 9
is recommended.  BIND 9 is available in the NetBSD Pkgsrc Collection
(pkgsrc/net/bind9).  Configuration files differ between BIND 8 and
9.  Plan such a migration appropriately.

The following instructions describe how to upgrade your named
binaries by updating your source tree and rebuilding and
installing a new version of named.

Be sure to restart running instance of named(8) after installation.


* NetBSD-current:

        Systems running NetBSD-current dated from before 2002-11-27
        should be upgraded to NetBSD-current dated 2002-11-27 or later.

        The following directories need to be updated from the
        netbsd-current CVS branch (aka HEAD):
                dist/bind
                usr.sbin/bind

        To update from CVS, re-build, and re-install named:
                # cd src
                # cvs update -d -P dist/bind usr.sbin/bind

                # cd usr.sbin/bind
                # make USETOOLS=no cleandir dependall
                # make USETOOLS=no install


* NetBSD 1.6, 1.6.1:

        The binary distributions of NetBSD 1.6 and 1.6.1 are vulnerable.

	Systems running NetBSD 1.6 sources dated from before 2002-11-28
	should be upgraded from NetBSD 1.6 sources dated 2002-11-28 or
	later.

	NetBSD 1.6.2 will include the fix.

        * Binary patch:

        To apply the binary patch, perform the following steps,
        replacing ARCH with the NetBSD architecture you are running
        (i.e. i386):

        ftp://ftp.netbsd.org/pub/NetBSD/security/patches/SA2003-018-bind/netbsd-1-6/ARCH-bind.tgz
        cd / && tar xzvpf /path/to/ARCH-bind.tgz

        The tar file will extract a new copy of:
                /usr/sbin/named

        Then restart named.

	
	* Updating from sources:
	
        The following directories need to be updated from the
        netbsd-1-6 CVS branch:
                dist/bind
                usr.sbin/bind

        To update from CVS, re-build, and re-install named:
                # cd src
                # cvs update -d -P -r netbsd-1-6 dist/bind usr.sbin/bind

                # cd usr.sbin/bind
		# make USETOOLS=no cleandir dependall
		# make USETOOLS=no install


* NetBSD 1.5, 1.5.1, 1.5.2, 1.5.3:

	The binary distributions of NetBSD 1.5 to 1.5.3 are vulnerable.   

	Systems running NetBSD 1.5, 1.5.1, 1.5.2 or 1.5.3 sources dated
	from before 2002-11-28 should be upgraded to NetBSD 1.5 sources
	dated 2002-11-28 or later.

        The following directories need to be updated from the
        netbsd-1-5 CVS branch:
                dist/bind
                usr.sbin/bind

        To update from CVS, re-build, and re-install named:
                # cd src
                # cvs update -d -P -r netbsd-1-5 dist/bind usr.sbin/bind

                # cd usr.sbin/bind
		# make cleandir dependall
		# make install


* pkgsrc

	bind8 versions prior to 8.3.7 and 8.4.3 are vulnerable.  ISC has
	not released 8.4.4. Upgrade to bind-8.4.4 or later when
	available, or upgrade to bind9 (if appropriate for your
	requirements)



Thanks To
=========

CERT


Revision History
================

	2003-12-16	Initial release


More Information
================

Advisories may be updated as new information becomes available.
The most recent version of this advisory (PGP signed) can be found at 
  ftp://ftp.NetBSD.org/pub/NetBSD/security/advisories/NetBSD-SA2003-018.txt.asc

Information about NetBSD and NetBSD security can be found at
http://www.NetBSD.org/ and http://www.NetBSD.org/Security/.


Copyright 2003, The NetBSD Foundation, Inc.  All Rights Reserved.
Redistribution permitted only in full, unmodified form.

$NetBSD: NetBSD-SA2003-018.txt,v 1.10 2003/12/17 03:08:24 david Exp $

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