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CERT* Advisory CA-97.22
Original issue date: August 13, 1997
Last Revised: May 26, 1998
Updated vendor information for Sun Microsystems
A complete revision history is at the end of this file.
Topic: BIND - the Berkeley Internet Name Daemon
- -----------------------------------------------------------------------------
*** This advisory supersedes CA-96.02. ***
Several vulnerabilities in the Berkeley Internet Name Daemon (BIND) have been
fixed in the current version of BIND. One of those vulnerabilities is now
being exploited, a vulnerability that results in cache poisoning (malicious or
misleading data from a remote name server is saved [cached] by another name
server).
The vulnerability has been fixed in BIND version 4.9.6; however, we recommend
upgrading according to our instructions in Section III.B or installing vendor
patches (see Appendix A). We also urge you to take the additional precautions
described in Section III.C.
We will update this advisory as we receive additional information. Please
check our advisory files regularly for updates that relate to your site.
- -----------------------------------------------------------------------------
I. Description
The Berkeley Internet Name Daemon (BIND) is an implementation of the
Domain Name Service (DNS) written primarily for UNIX Systems. BIND
consists of three parts:
* The client part. This part contains subroutine libraries used by
programs that require DNS services. Example clients of these libraries
are telnet, the X Windows System, and ssh (the secure shell). The
client part consists of subroutine libraries, header files, and manual
pages.
* The server part. This part contains the name server daemon (named) and
its support program (named-xfer). These programs provide one source of
the data used for mapping between host names and IP addresses. When
appropriately configured, these name server daemons can interoperate
across a network (the Internet for example) to provide the mapping
services for that network. The server part consists of the daemon, its
support programs and scripts, and manual pages.
* The tools part. This part contains various tools for interrogating
name servers in a network. They use the client part to extract
information from those servers. The tools part consists of these
interrogation tools and manual pages.
As BIND has matured, several vulnerabilities in the client, server,
and tools parts have been fixed. Among these is server cache poisoning.
Cache poisoning occurs when malicious or misleading data received from
a remote name server is saved (cached) by another name server. This
"bad" data is then made available to programs that request the cached
data through the client interface.
Analysis of recent incidents reported to the CERT Coordination Center
has shown that the cache poisoning technique is being used to adversely
affect the mapping between host names and IP addresses. Once this
mapping has been changed, any information sent between hosts on a
network may be subjected to inspection, capture, or corruption.
Although the new BIND distributions do address important security
problems, not all known problems are fixed. In particular, several
problems can be fixed only with the use of cryptographic authentication
techniques. Implementing and deploying this solution is non-trivial;
work on this task is currently underway within the Internet community.
II. Impact
The mapping between host names and IP addresses may be changed. As
a result, attackers can inspect, capture, or corrupt the information
exchanged between hosts on a network.
III. Solution
Install a patch from your vendor or implement the "best practice" workaround
we recommend in Section III.B. In either case, take the extra precautions
described in Section III.C.
A. Obtain and install a patch for this problem.
Information from vendors can be found in Appendix A of this advisory;
we will update the appendix as we receive more information.
B. Until you are able to install the appropriate patch, we recommend
the following workaround.
The "best practice" for operating the publicly available BIND
system can be either:
* a heterogeneous solution that involves first installing BIND
release 4.9.6 and then release 8.1.1, or
* a homogeneous solution that involves installing only BIND release
8.1.1.
In the paragraphs below, we describe how to determine which solution
you should use.
Note: Although the security posture in BIND version 8.1.1 is
identical to that of version 4.9.6, version 8.1.1 is the
version that will continue to undergo changes and improvements,
hence our selection of its use as the "best practice."
1. Shared Object Client Subroutine Library
If your system and its programs rely on the shared object client
subroutine library that comes with some releases of BIND, probably
named libresolv.so, then you need the shared object subroutine
library and other client software from release 4.9.6. (As of
this writing, BIND version 8 does not yet support the client
part as a shared object library.) This client software is
available at
ftp://ftp.isc.org/isc/bind/src/4.9.6/bind-4.9.6-REL.tar.gz
MD5 (bind-4.9.6-REL.tar.gz) = 76dd66e920ad0638c8a37545a6531594
Follow the instructions in the file named INSTALL in the top-level
directory.
After installing this client part, install the server and tool
parts from release 8.1.1. This software is available at
ftp://ftp.isc.org/isc/bind/src/8.1.1/bind-src.tar.gz
MD5 (bind-src.tar.gz) = 7487b8d647edba2053edc1cda0c6afd0
Follow the instructions in the src/INSTALL file. Note that
this version will install the client libraries and header files
in a non-standard place, /usr/local/lib and /usr/local/include.
The src/INSTALL file describes what is being installed and
where.
When you install release 4.9.6 first, its client, server, and
tools parts will be installed in the production locations. When
you then install release 8.1.1, the server and tools parts will be
overwritten by that release's versions, but the 4.9.6 client part
will not.
2. No Shared Object Client Subroutine Library
If you do not need the shared object client subroutine library,
then you need only upgrade to release 8.1.1. This software is
available at
ftp://ftp.isc.org/isc/bind/src/8.1.1/bind-src.tar.gz
MD5 (bind-src.tar.gz) = 7487b8d647edba2053edc1cda0c6afd0
Follow the instructions in src/INSTALL. Note that the client
subroutine library and header files are installed in
/usr/local/lib and /usr/local/include respectively. To use
these when building other systems, you will need to refer to
their installed locations.
Note: ftp://ftp.isc.org/isc/bind/src/ is mirrored in
Germany at ftp://ftp.cert.dfn.de/pub/tools/net/bind/src/
As new versions of BIND are released in the future, you will be able
to find them at these sites, as well as other mirrors. You can also
check ftp://info.cert.org/pub/latest_sw_versions/ for version
information.
C. Take additional precautions.
As good security practice in general, filter at a router all
name-based authentication services so that you do not rely on DNS
information for authentication. This includes the services rlogin, rsh
(rcp), xhost, NFS, and any other locally installed services that
provide trust based on domain name information.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Appendix A - Vendor Information
Below is a list of the vendors who have provided information for this
advisory. We will update this appendix as we receive additional information.
If you do not see your vendor's name, the CERT/CC did not hear from that
vendor. Please contact the vendor directly.
Berkeley Software Design, Inc. (BSDI)
=====================================
Patches from BSDI
ftp://ftp.bsdi.com/bsdi/patches/patches-2.1/U210-038
md5 checksum: 8ce46cd2d1aff3b294a84ae54e82a824
ftp://ftp.bsdi.com/bsdi/patches/patches-3.0/M300-025
md5 checksum: d7b5c6094089955cd1af207dab05bc0f
Cray Research - A Silicon Graphics Company
===========================================
Cray Research has determined that the version of BIND shipped with all
current releases of Unicos and Unicos/mk are susceptible to the problem
described in this advisory. We are currently working on upgrading our
version of BIND to the 4.9.6 release.
Digital Equipment Corporation
=============================
xref CASE ID: SSRT0494U
At the time of writing this document, patches(binary kits) are in
progress and final patch testing is expected to begin soon.
Digital will provide notice of the completion/availability of the
patches through AES services (DIA, DSNlink FLASH) and be
available from your normal Digital Support channel.
DIGITAL EQUIPMENT CORPORATION AUG/97
----------------------------- ------
Hewlett-Packard Company
=======================
HP is vulnerable. Patches in process.
IBM Corporation
===============
IBM is currently working on the following APARs which will be
available soon:
AIX 4.1: IX70236
AIX 4.2: IX70237
To Order
--------
APARs may be ordered using Electronic Fix Distribution (via FixDist)
or from the IBM Support Center. For more information on FixDist,
reference URL:
http://service.software.ibm.com/aixsupport/
or send e-mail to aixserv@austin.ibm.com with a subject of "FixDist".
IBM and AIX are registered trademarks of International Business Machines
Corporation.
NEC Corporation
===============
NEC is vulnerable. The systems affected by this problem
are as follows:
UX/4800
UX/4800(64)
EWS-UX/V(Rel4.2MP)
EWS-UX/V(Rel4.2)
UP-UX/V(Rel4.2MP)
Patches are in progress and will be made available from
ftp://ftp.meshnet.or.jp/pub/48pub/security.
Siemens-Nixdorf Informationssysteme AG
======================================
We are investigating this problem and will provide updated information
for this advisory when it becomes available.
The Santa Cruz Operation
========================
The following SCO operating systems are vulnerable:
- SCO Open Desktop/Open Server 3.0, SCO UNIX 3.2v4
- SCO OpenServer 5.0
- SCO UnixWare 2.1
SCO CMW+ 3.0 is not vulnerable as bind is not supported on CMW+ platforms.
SCO has made an interim fix available for anonymous ftp:
ftp://ftp.sco.com/SSE/sse008.ltr.Z - cover letter
ftp://ftp.sco.com/SSE/sse008.tar.Z - replacement binaries
The fix includes binaries for the following SCO operating systems:
- SCO Open Desktop/Open Server 3.0, SCO UNIX 3.2v4
- SCO OpenServer 5.0
- SCO UnixWare 2.1
Sun Microsystems
================
The following patches relate to the BIND vulnerability:
SunOS version Patch Id
------------- --------
5.6 105755-03
5.6_x86 105756-03
5.5.1 103663-11
5.5.1_x86 103664-11
5.5 103667-09
5.5_x86 103668-09
5.4 102479-11
5.4_x86 102480-09
5.3 101359-08
Sun recommended and security patches (including checksums) are available from:
http://sunsolve.sun.com/sunsolve/pubpatches/patches.html
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The CERT Coordination Center staff thanks Paul Vixie and Wolfgang Ley for
their contributions to this advisory.
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If you believe that your system has been compromised, contact the CERT
Coordination Center or your representative in the Forum of Incident Response
and Security Teams (see http://www.first.org/team-info/).
CERT/CC Contact Information
- ----------------------------
Email cert@cert.org
Phone +1 412-268-7090 (24-hour hotline)
CERT personnel answer 8:30-5:00 p.m. EST(GMT-5) / EDT(GMT-4)
and are on call for emergencies during other hours.
Fax +1 412-268-6989
Postal address
CERT Coordination Center
Software Engineering Institute
Carnegie Mellon University
Pittsburgh PA 15213-3890
USA
Using encryption
We strongly urge you to encrypt sensitive information sent by email. We can
support a shared DES key or PGP. Contact the CERT/CC for more information.
Location of CERT PGP key
ftp://info.cert.org/pub/CERT_PGP.key
Getting security information
CERT publications and other security information are available from
http://www.cert.org/
ftp://info.cert.org/pub/
CERT advisories and bulletins are also posted on the USENET newsgroup
comp.security.announce
To be added to our mailing list for advisories and bulletins, send
email to
cert-advisory-request@cert.org
In the subject line, type
SUBSCRIBE your-email-address
- ------------------------------------------------------------------------------
Copyright 1997 Carnegie Mellon University. Conditions for use, disclaimers,
and sponsorship information can be found in
http://www.cert.org/legal_stuff.html and ftp://ftp.cert.org/pub/legal_stuff .
If you do not have FTP or web access, send mail to cert@cert.org with
"copyright" in the subject line.
CERT is registered in the U.S. Patent and Trademark Office.
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This file: ftp://info.cert.org/pub/cert_advisories/CA-97.22.bind
http://www.cert.org
click on "CERT Advisories"
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Revision history
May 26, 1998 Updated vendor information for Sun Microsystems
Sept. 30, 1997 Updated copyright statement
Sept. 19, 1997 Appendix A - Added information for BSDI.
Aug. 20, 1997 Introduction - Clarified that 4.9.6 is not vulnerable.
Section III - Added a note why sites should upgrade to 8.1.1.
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