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NetBSD Security Advisory 2001-001


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Date: Sun, 11 Feb 2001 14:22:35 +1100
From: NetBSD Security Officer <security-officer@netbsd.org.>
To: [email protected]
Subject: NetBSD Security Advisory 2001-001

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                 NetBSD Security Advisory 2001-001

Topic: Multiple BIND vulnerabilities Version: All release versions of NetBSD, and NetBSD-current Severity: Remote root execution of commands is possible Fixed: NetBSD-current: January 27, 2001 NetBSD 1.5 branch: January 28, 2001 NetBSD 1.4 branch: January 28, 2001 Abstract ======== Several security problems were recently found in the ISC BIND software, used in NetBSD (and many other systems) to provide Domain Name System (DNS) services. At least one of these vulnerabilities included the possibility of a remote root exploit through execution of arbitrary code in an overflowed buffer. All systems running DNS servers should remove the vulnerabilities by updating to a current version of ISC bind by following one of several recommended procedures. Technical Details ================= Technical details of the vulnerabilities are publicised in CERT Advisory CA-2001-02, and by the ISC at: http://www.isc.org/products/BIND/bind-security.html This information is not duplicated here. The purpose of this advisory is to clarify the vulnerability and appropriate remedial action for users of affected versions of NetBSD. CERT identified four separate vulnerabilities present in various versions of BIND. The version of BIND included with different NetBSD releases varies, therefore the vulnerability of those NetBSD releases also varies, as summarised here: CERT# Descr. BIND NetBSD versions vulnerable 196945 Trans. Sig. buffer o/f 8 1.4.x, 1.5, current 572183 nslookupComplain buff. o/f 4 <1.4 only 868916 nslookupComplain input val. 4 <1.4 only 325431 Env. variable disclosure 4,8 <1.4, 1.4.x, 1.5, current Note that although not all vulnerabilities apply to all systems, the most serious vulnerability (196945) applies to all recent releases and NetBSD-current, and all versions have some vulnerability. Users of versions prior to NetBSD 1.4 should see the special note, below. Solutions and Workarounds
All systems with BIND in use should be fixed; this is all systems offering DNS services through named(8). Systems are vulnerable if the version reported by "/usr/sbin/named -v" is less than 8.2.3, and named is running. There are several ways that systems administrators may update their versions of BIND. Each of these mechanisms is described in more detail in the following subsections. * System upgrade via source * Replace the system BIND with one from the NetBSD Packages collection. Updating via source: Users may update their system source, from the appropriate release branch or NetBSD-current, and rebuild BIND (as well as other parts of the system). This method is recommended for users of NetBSD-current and technically literate users of the most recent releases on each branch (1.4.3 or 1.5). Note that the NetBSD release branches contain accumulated changes and bugfixes since the most recent release; these changes are intended to improve the system, but have not yet been through the complete release engineering cycle. Users who wish to remain at a formal release should use the pkgsrc method instead. System sources can be updated via anonymous CVS, SUP, or via download of source tarfiles from the appropriate branch, collection or directory: Release CVS branch SUP collection FTP directory ------------------------------------------------------------------- 1.4 netbsd-1-4 release-1-4 /pub/NetBSD/NetBSD-release-1-4 1.5 netbsd-1-5 release-1-5 /pub/NetBSD/NetBSD-release-1-4 current HEAD current /pub/NetBSD/NetBSD-current Systems running NetBSD-current dated from before 2001-01-28 should be upgraded to NetBSD-current dated 2001-01-28 or later. For NetBSD-current, see /usr/src/UPDATING for additional instructions, as additional dependencies may need to be rebuilt before BIND. Systems running either NetBSD-release* branch dated from before 2001-01-29 should be upgraded to 2001-01-29 or later. It is recommended that users tracking inter-release sources do a full system update. Once sources and dependencies have been taken care of, the following will rebuild *just* BIND: # cd /usr/src/usr.sbin/bin # make depend # make # make install Updating via pkgsrc: For many users looking for a quick and specific update, the NetBSD packages collection provides a simple mechanism to install a current version of BIND directly from the ISC distribution, to replace the system version. This technique is applicable to ALL systems, and is recommended for urgent fixes. It may be used as a temporary measure even by those intending to follow up with a full system upgrade. 1) First, make sure you have an up-to-date pkgsrc collection (at least as recent as 2001-01-28). This can be obtained via anonymous CVS, SUP or FTP from the project servers or mirrors. 2) Change to the appropriate subdirectory: # cd /usr/pkgsrc/net/bind8 3) Ensure that the pkgsrc version is 8.2.3 or newer: # grep PKGNAME Makefile PKGNAME= bind-8.2.3 4) Build and install the package. This will download the sources automatically. (If prompted to update the pkg tools first, do so according to the instructions presented, then return to the bind8 directory and resume here). # make install 5) Now you have an up-to-date version of BIND installed in /usr/pkg/. Next, it is necessary to disable the system named, and replace it with a link to the new one: # cd /usr/sbin # mv named named.OFF # ln -s /usr/pkg/sbin/named . # mv ndc ndc.OFF # ln -s /usr/pkg/sbin/ndc . 6) Next, place a link to the name server configuration file into /usr/pkg/etc/named.conf, where the pkgsrc named(8) expects to find it: # cd /usr/pkg/etc # ln -sf /etc/namedb/named.conf . (If you keep your named.conf file somewhere other than /etc/namedb, adjust the command above accordingly.) 7) Then kill the running named, and restart from the new one: # kill <pid> # /usr/pkg/sbin/ndc start Pre-compiled binary packages of net/bind8 have been prepared for some architectures and NetBSD versions. These can be found under ftp://ftp.netbsd.org/pub/NetBSD/packages You may wish to use one of these instead of having the pkgsrc system compile for you. Download the appropriate file for your system if available, and use: # pkg_add bind-8.2.3.tgz to install the pre-built package. Then follow the steps from 5 above to disable the system named and enable the new one. NOTE FOR SYSTEMS PRIOR TO NetBSD 1.4: Systems running releases older than NetBSD 1.4 should be upgraded to a supported NetBSD version. These releases shipped a version of BIND based on BIND4. Systems administrators need to be aware of several configuration mechanism changes between BIND4 and BIND8, details can be found at the ISC website. BIND8 ships with a script called named-bootconf which will assist part of the process. The pkgsrc method is expected to work for these systems. It has been done successfully in a number of instances, but it has not been tested in all cases. It may very well necessitate updating of the pkgtools/pkg_install package prior to updating bind, if these systems have not had active pkgsrc installations recently. The use of BIND4 is no longer encouraged by NetBSD or the ISC; nevertheless the current ISC version of BIND4 is available in pkgsrc/net/bind4, to provide system adminstrators the option of patching the vulnerability quickly and then planning an upgrade to BIND8. Thanks To ========= Thanks go to Jun-Ichiro Hagino for prompt attention to incorporating the BIND upgrade, and to Havard Eidnes for providing the pull-ups to the release branches. Revision History ================ 2001/02/10 - Initial Release More Information ================ Information about NetBSD and NetBSD security can be found at http://www.NetBSD.ORG/ and http://www.NetBSD.ORG/Security/. Copyright 2001, The NetBSD Foundation, Inc. All Rights Reserved. $NetBSD: NetBSD-SA2001-001.txt,v 1.5 2001/02/10 22:28:27 dan Exp $ -----BEGIN PGP SIGNATURE----- Version: 2.6.3ia Charset: noconv iQCVAwUBOoXAlD5Ru2/4N2IFAQHV+QP/S8iHeMlaKDw+Yue0cFnKpW9XhWoLZF/T 2pRqWt2jJhwqrf3T1MsMFbfsTXkthCyDyaTy5BmJEQl9dFoiuHXJPmIyRizibfoC dqfQ1AJceEWndfnyTzjgghZFy4gbBoj1FOAhQZsm9bWCkWqJM/ZWmUH2N82xtknz ZZwTvtSftXw= =yQnU -----END PGP SIGNATURE-----

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