Date: Thu, 22 Feb 1996 17:52:30 -0800 (PST) From: invalid opcode <coredump@nervosa.com> To: freebsd-security@freebsd.org Subject: BoS: (fwd) CERT Advisory CA-96.04 - Corrupt Information from Network Servers (fwd) Message-ID: <Pine.BSF.3.91.960222175153.12342A-100000@nervosa.com>
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This is from Best of Security, as a result of this, sendmail has been upgraded to 8.7.4 == Chris Layne ============================================================== == coredump@nervosa.com ================= http://www.nervosa.com/~coredump == ---------- Forwarded message ---------- Date: Thu, 22 Feb 1996 15:58:36 -0600 (CST) From: Noam Freedman <noam@noam.com> To: best-of-security@suburbia.net Subject: BoS: (fwd) CERT Advisory CA-96.04 - Corrupt Information from Network Servers ============================================================================= CERT(sm) Advisory CA-96.04 February 22, 1996 Topic: Corrupt Information from Network Servers ----------------------------------------------------------------------------- The CERT Coordination Center has received reports of intruders exploiting systems by corrupting data provided by a Domain Name Service (DNS) server. Although these reports have focused only on DNS, this vulnerability could apply to any network service from which data is received and subsequently used. Section III.A contains a pointer to two subroutines that address the DNS problem. These subroutines, written in the C programming language, can be used to validate host names and IP addresses according to RFCs 952 and 1123, as well as names containing characters drawn from common practice, namely "_" and "/". In the specific case of sendmail, the problem has already been addressed by patches (see Section III.B). As we receive additional information relating to this advisory, we will place it in ftp://info.cert.org/pub/cert_advisories/CA-96.04.README We encourage you to check our README files regularly for updates on advisories that relate to your site. ----------------------------------------------------------------------------- I. Description Information provided by an information server may be of a form that could cause programs to operate in unexpected ways. The subroutines and programs transferring data from that information server could check the data for correctness of form; however, programs that *use* that data are ultimately responsible for ensuring adherence to the documents that define the correct form. For example, consider a program that uses the host name returned by gethostbyname() as part of the string given to the popen() or system() subroutines. Because gethostbyname() may use an information server beyond your control, the data returned could be of a form that causes the popen() or system() subroutines to execute other commands besides the command specified by that program. This advisory speaks to a specific instance of a problem caused by the information returned by DNS, but information from any server should be checked for validity. Examples of other information servers are YP, NIS, NIS+, and netinfo. II. Impact Programs that do not check data provided by information servers may operate in unpredictable ways and give unexpected results. In particular, exploitation of this vulnerability may allow remote access by unauthorized users. Exploitation can also lead to root access by both local and remote users. III. Solution For programs that you write or have written, consider integrating the general solution in Section A below. In the specific case of the sendmail mail delivery program, Eric Allman, the original author of sendmail, has produced patches that address the problem. Section B provides details about these, along with vendor information and additional steps you should take to protect sendmail. A. General solution for Internet host names Use the host name and IP address validation subroutines available at the locations listed below. Include them in all programs that use the result of the host name lookups in any way. ftp://info.cert.org/pub/tools/ValidateHostname/IsValid.c ftp://ftp.cert.dfn.de/pub/tools/net/ValidateHostname/IsValid.c Checksum: MD5 (IsValid.c) = 9456f2f5dcb226eaa19a72256c8d1922 The IsValid.c file contains code for the IsValidHostname and IsValidIPAddress subroutines. This code can be used to check host names and IP addresses for validity according to RFCs 952 and 1123, well as names containing characters drawn from common practice, namely "_" and "/". B. Specific solutions in the case of sendmail Install a patch from your vendor when it becomes available (see B.1) or install Eric Allman's patch (B.2). In both cases, install the sendmail restricted shell program (B.3). 1. Install a patch from your vendor. Below is a summary of the vendors who have reported status to us as of the date of this advisory. More complete information is provided in the appendix of this advisory and reproduced in the CA-96.04.README file. We will update the README file as we receive more information. If your vendor's name is not on this list, please contact the vendor directly. Vendor or Source Status ---------------- ------------ Eric Allman Patches available. Hewlett-Packard Co. Vulnerable, watch readme file for updates. IBM Corporation Working on fixes for sendmail. Silicon Graphics Inc. Patch planned. 2. Install a patch to sendmail. If you are presently running sendmail 8.6.12, there is a patch that makes version 8.6.13. Similarly, if you are presently running sendmail 8.7.3, there is a patch that makes version 8.7.4. The patches are available for anonymous FTP from ftp://info.cert.org/pub/tools/sendmail/ ftp://ftp.cs.berkeley.edu/ucb/src/sendmail/ ftp://ftp.auscert.org.au/pub/mirrors/ftp.cs.berkeley.edu/ucb/sendmail/ ftp://ftp.cert.dfn.de/pub/tools/net/sendmail/ Checksums for the 8.6.13 release: MD5 (sendmail.8.6.13.base.tar.Z) = e8cf3ea19876d9b9def5c0bcb793d241 MD5 (sendmail.8.6.13.cf.tar.Z) = 4492026fa9e750cd33974322cb5a6fb9 MD5 (sendmail.8.6.13.misc.tar.Z) = 7ec5d31656e93e08a3892f0ae542b674 MD5 (sendmail.8.6.13.xdoc.tar.Z) = e4d3caebcdc4912ed2ecce1a77e45712 Checksum for the 8.6.13 patch: MD5 (sendmail.8.6.13.patch) = 6390b792cb5513ff622da8791d6d2073 Checksum for the 8.7.4 release: MD5 (sendmail.8.7.4.tar.Z) = 4bf774a12752497527aae11e2bdbab36 Checksum for the 8.7.4 patch: MD5 (sendmail.8.7.4.patch) = ef828ad91fe56e4eb6b0cacced864cd5 3. Run smrsh as additional protection for sendmail. With all versions of sendmail, we recommend that you install and use the sendmail restricted shell program (smrsh). We urge you to do this whether you use the vendor's supplied sendmail, install sendmail yourself, or patch an earlier version of sendmail. Beginning with version 8.7.1, smrsh is included in the sendmail distribution, in the subdirectory smrsh. See the RELEASE_NOTES file for a description of how to integrate smrsh into your sendmail configuration file. --------------------------------------------------------------------------- The CERT Coordination Center thanks Eric Allman of Pangaea Reference Systems, Andrew Gross of San Diego Supercomputer Center, Eric Halil of AUSCERT, Wolfgang Ley of DFN-CERT, and Paul Vixie for their support in the development of 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 (FIRST). We strongly urge you to encrypt any sensitive information you send by email. The CERT Coordination Center can support a shared DES key and PGP. Contact the CERT staff for more information. Location of CERT PGP key ftp://info.cert.org/pub/CERT_PGP.key CERT 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 To be added to our mailing list for CERT advisories and bulletins, send your email address to cert-advisory-request@cert.org CERT publications, information about FIRST representatives, and other security-related information are available for anonymous FTP from ftp://info.cert.org/pub/ CERT advisories and bulletins are also posted on the USENET newsgroup comp.security.announce Copyright 1996 Carnegie Mellon University This material may be reproduced and distributed without permission provided it is used for noncommercial purposes and the copyright statement is included. CERT is a service mark of Carnegie Mellon University. ......................................................................... Appendix A: Vendor Information Current as of February 22, 1996 See CA-96.04.README for updated information. Below is information we have received from vendors concerning the vulnerability described in this advisory. If you do not see your vendor's name, please contact the vendor directly for information. ----------------------- Eric Allman (original author of sendmail) Install a patch to sendmail. If you are presently running sendmail 8.6.12, there is a patch that makes version 8.6.13. Similarly, if you are presently running sendmail 8.7.3, there is a patch that makes version 8.7.4. The patches are available for anonymous FTP from ftp://info.cert.org/pub/tools/sendmail/ ftp://ftp.cs.berkeley.edu/ucb/src/sendmail/ ftp://ftp.auscert.org.au/pub/mirrors/ftp.cs.berkeley.edu/ucb/sendmail/ ftp://ftp.cert.dfn.de/pub/tools/net/sendmail/ Checksums for the 8.6.13 release: MD5 (sendmail.8.6.13.base.tar.Z) = e8cf3ea19876d9b9def5c0bcb793d241 MD5 (sendmail.8.6.13.cf.tar.Z) = 4492026fa9e750cd33974322cb5a6fb9 MD5 (sendmail.8.6.13.misc.tar.Z) = 7ec5d31656e93e08a3892f0ae542b674 MD5 (sendmail.8.6.13.xdoc.tar.Z) = e4d3caebcdc4912ed2ecce1a77e45712 Checksum for the 8.6.13 patch: MD5 (sendmail.8.6.13.patch) = 6390b792cb5513ff622da8791d6d2073 Checksum for the 8.7.4 release: MD5 (sendmail.8.7.4.tar.Z) = 4bf774a12752497527aae11e2bdbab36 Checksum for the 8.7.4 patch: MD5 (sendmail.8.7.4.patch) = ef828ad91fe56e4eb6b0cacced864cd5 ---------------------- Hewlett-Packard Company Vulnerable, watch readme file for updates. ---------------------- IBM Corporation IBM is working on fixes for sendmail. ---------------------- Silicon Graphics Inc. At the time of writing of this document, a patch is planned for IRIX versions 5.2, 5.3, 6.0, 6.0.1 and 6.1 for this issue. This patch along with previous SGI Advisories and security patches can be obtained via anonymous FTP from sgigate.sgi.com or its mirror, ftp.sgi.com. SGI security patches and advisories are provided freely to all interested parties. The advisories and patches can be found in either the ~ftp/patches or ~ftp/security directories along with more current pertinent information. For assistance obtaining or working with security patches, please contact your SGI support provider.
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