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[ For Public Release ]
__________________________________________________________
The U.S. Department of Energy
Computer Incident Advisory Capability
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__________________________________________________________
INFORMATION BULLETIN
Vulnerability in Bind
(Update to Bulletin G-14, Domain Name Service Vulnerabilities)
August 14, 1997 21:00 GMT Number H-96
______________________________________________________________________________
PROBLEM: Domain Name Service (DNS) servers being exploited, using BIND
and sendmail weaknesses.
PLATFORM: Systems running any version of BIND before release 8.1.1.
DAMAGE: Data becomes corrupted ("cache poisoning").
SOLUTION: Patches or workarounds are available for several platforms. See
below.
______________________________________________________________________________
VULNERABILITY Intruders have been able to exploit this vulnerability on DNS
ASSESSMENT: servers. This vulnerability may potentially extend to other
network services.
______________________________________________________________________________
[Start CERT Advisory]
=============================================================================
CERT* Advisory CA-97.22
Original issue date: August 13, 1997
Last revised: --
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). All versions of BIND before release 8.1.1 are vulnerable.
The CERT/CC team recommends installing a patch from your vendor (See Appendix
A). Until you can install a vendor patch, we recommend the workaround
described in Section III.B. 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
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.
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.
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, Inc.
======================
We are producing patches.
- -----------------------------------------------------------------------------
The CERT Coordination Center staff thanks Paul Vixie and Wolfgang Ley for
their contributions to this advisory.
- -----------------------------------------------------------------------------
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 apply; they can be found
in http://www.cert.org/legal_stuff.html and
ftp://info.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.
- ---------------------------------------------------------------------------
This file: ftp://info.cert.org/pub/cert_advisories/CA-97.22.bind
http://www.cert.org
click on "CERT Advisories"
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Revision history
[End CERT Advisory]
______________________________________________________________________________
CIAC wishes to acknowledge the contributions of CERT for the
information contained in this bulletin.
______________________________________________________________________________
CIAC, the Computer Incident Advisory Capability, is the computer
security incident response team for the U.S. Department of Energy
(DOE) and the emergency backup response team for the National
Institutes of Health (NIH). CIAC is located at the Lawrence Livermore
National Laboratory in Livermore, California. CIAC is also a founding
member of FIRST, the Forum of Incident Response and Security Teams, a
global organization established to foster cooperation and coordination
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CIAC services are available to DOE, DOE contractors, and the NIH. CIAC
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FAX: +1 510-423-8002
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E-mail: ciac@llnl.gov
For emergencies and off-hour assistance, DOE, DOE contractor sites,
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Previous CIAC notices, anti-virus software, and other information are
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LAST 10 CIAC BULLETINS ISSUED (Previous bulletins available from CIAC)
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H-87: HP-UX rlogin Vulnerability
H-88: SGI IRIX talkd Vulnerability
H-89: SunSO talkd Buffer Overrun Vulnerability
H-90: SunOS, Solaris NIS+ Vulnerability
H-91: HP-UX Large UID's and GID's Vulnerability
H-92: HP-UX X11/Motif Lib & Novell Netware Vulerabilities
H-93: SGI IRIX ordist Buffer Overrun Vulnerability
H-94: SunOS Vulnerability in ps
H-95: SunOS Vulnerability in x-lock
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