|
 |
CERT® Advisory CA-1996-14 Vulnerability in rdistOriginal issue date: July 24, 1996Last revised: January 15, 1998 Updated information for NCR. A complete revision history is at the end of this file. This advisory supersedes CA-91.20 and CA-94.04. The CERT Coordination Center has received reports that a new vulnerability in rdist has been found and an exploitation script is widely available. Current reports indicate that the script works on x86-based versions of the UNIX Operating System; however, we believe that it would not be difficult to write variants that work on other instruction sets and configurations. The CERT/CC Staff recommends following the steps in Section III.A. to determine if your system is vulnerable and to disable vulnerable programs, then following your vendor's instructions (Section III.B and Appendix A). Until you can install a vendor patch, you may want to install a freely available version of rdist, noted in Section III.C. We will update this advisory as we receive additional information. Please check advisory files regularly for updates that relate to your site. I. DescriptionThe rdist program is a UNIX Operating System utility used to distribute files from one host to another. On most systems, rdist is installed as set-user-id root, a necessity due to its design. Unfortunately, this setting makes it a favorite target for vulnerability investigation.A new vulnerability in rdist has been discovered and reported. The vulnerability lies in the lookup() subroutine where the value of a command line argument is used to overflow the subroutine call stack. If that argument is specially crafted with native machine code, lookup() returns control to the code added to the call stack instead of the subroutine that called lookup(). If, for example, this added code uses a member of the exec system call family and names /bin/sh as the program to be executed, that shell is then run with set-user-id root privileges. No matter what code is added, the code runs with set-user-id root privileges. An exploitation program, which is circulating on the Internet, takes advantage of this vulnerability. While it purports to work only on x86-based versions of the UNIX Operating System, variants tuned to other instruction sets and configurations are straightforward to write. II. ImpactOn unpatched systems, anyone with access to a local account can gain root access.III. SolutionWe urge you to follow the steps in Section A to determine if your system is potentially vulnerable and, if it is, to turn off rdist while you decide how to proceed. If you need the functionality that rdist provides, install a vendor patch (Sec. B). Until you can do so, you may want to install a freely available version of rdist that does not need to be installed as set-user-id root and is, therefore, not susceptible to the exploitation described in this advisory (Sec. C).A. How to determine if your system is vulnerableTo determine if a system is vulnerable and to disable the programs that are believed to be vulnerable, use the following find command or a variant. Consult your local system documentation to determine how to tailor the find program on your system.You will need to run the find command on each system you maintain because the command examines files on the local disk only. Substitute the names of your local file systems for FILE_SYSTEM_NAMES in the example. Example local file system names are /, /usr, and /var. You must do this as root. Note that this is one long command, though we have separated it onto two lines using a back-slash.
find FILE_SYSTEM_NAMES -xdev -type f -user root \
-name rdist -perm -04000 -print -ok chmod u-s '{}' \;
This command will find all files on a system that are only in the file system you name (FILE_SYSTEM_NAMES -xdev) Once found, those files will have their names printed (-print) B. Obtain and install the appropriate patchBelow is a list of vendors who have provided information. Details are in Appendix A of this advisory. We will update the advisory as we receive more information.Berkeley Software Design, Inc. If your vendor's name is not on this list, please contact the vendor directly. C. If you need the functionality that rdist provides but a patched version is not yet available from your vendor:Consider installing rdist-6.1.3, which is freely available fromftp://usc.edu/pub/rdist/rdist-6.1.3.tar.gz MD5 (rdist-6.1.3.tar.gz) = 8a76b880b023c5e648b7cb77b9608b9f The README file in the distribution explains how to configure and install this version of rdist. We strongly recommend that you configure this version of rdist to use rsh instead of rcmd. Here is the relevant text from the README: By default rdist uses rsh(1c) to make connections to remote hosts. This has the advantage that rdist does not need to be setuid to "root". This eliminates most potential security holes. It has the disadvantage that it takes slightly more time for rdist to connect to a remote host due to the added overhead of doing a fork() and then running the rsh(1c) command.For versions of rdist V6 prior to 6.1.3: If you compile rdist with -DDIRECT_RCMD *and* you run rdist setuid to root, you are vulnerable to the problem described in this advisory. You need to update to rdist version 6.1.3. Note that by default, rdist V6 is distributed to compile without -DDIRECT_RCMD and not run setuid to root. If you have previously built version 6.X of rdist with the -DDIRECT_RCMD directive added to the $(DEFS_LOCAL) and set "RDIST_MODE = 4555" in "Makefile.local", we recommend that you first disable this version with the find command given in Section III.A above, then either rebuild rdist with its default settings or upgrade to 6.1.3. Appendix A: Vendor InformationBelow 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.Berkeley Software Design, Inc.BSD/OS is vulnerable to this problem.BSDI has released a patch for rdist in BSD/OS V2.1. Sites using the non-kerberized rdist should install patch U210-018, which is available from the mailback server and also from: ftp://ftp.bsdi.com/bsdi/patches/patches-2.1/U210-018 md5 checksum: 86005d8bbb67eb737120741bd254d26a U210-018 Domestic licensees that are using the Kerberos package should install patch D210-018 from: mailback server (this patch is available only to domestic licensees because of US export restrictions on crypto software). Be sure to install only the appropriate patch. md5 checksum: b2060ec4eb9b18ace4e76bcb9441353f D210-018 Data General CorporationData General does not provide a version of rdist as part of the standard release of DG/UX. Rdist is available as contributed software which is not supported by Data General. This problem will be fixed in the next release of the contributed software package.Digital Equipment Corporation#96.0329ASOURCE: Digital Equipment Corporation Copyright (c) Digital Equipment Corporation 1996. All rights reserved. SUMMARY PATCH-ID INFORMATION: *NOTE*
TITLES
OSF_V2_0 (Patch ID: OSFV20-244-1>
PATCH AVAILABILITY: Software service contract or warranty customers may obtain the patched rdist through normal Digital support channels, via AES (Advanced Electronic Services). These patch's are available from the remedial patch stream for the versions identified above and may be found in the applicable versions readme files. ftp://ftp.service.digital.com/public/osf Please refer to applicable Release Note information prior to upgrading your installation. Note: Non-contract/non-warranty customers should contact As always, Digital urges you to periodically review your system management and security procedures. Digital will continue to review and enhance the security features of its products and work with customers to maintain and improve the security and integrity of their systems. - DIGITAL EQUIPMENT CORPORATION
FreeBSD, Inc.Versions affected:
As root, execute the commands:
# chmod u-s,go-rx /usr/bin/rdist ftp://freebsd.org/pub/CERT/patches/SA-96:16/ For more information: ftp://freebsd.org/pub/CERT/advisories/SA-96:16/ Hewlett-Packard CompanyThe rdist vulnerability can be eliminated from releases 10.0, 10.01, 10.10, and 10.20 of HP-UX by applying the patches mentioned below. HP-UX releases prior to 10.X and after 10.20 (i.e., 10.30) are not vulnerable. HP/UX 9.X is not vulnerable.
All patches are available now, except PHNE_7920 which will be available after 8 August. See HEWLETT-PACKARD SECURITY BULLETIN: HPSBUX9608-036, 08 Aug 96 for more details. IBM CorporationAIX is vulnerable to this problem. Fixes are in process but are not yet available. The APAR numbers for the fixes are given below. In the meantime, we recommend removing the setuid bit from the /usr/bin/rdist program.To remove the setuid bit, follow these instructions. As the root user, type:
AIX 3.2Apply the following fix to your system:
AIX 4.1Apply the following fix to your system:
AIX 4.2Apply the following fix to your system:
To OrderAPARs may be ordered using 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 IBM and AIX are registered trademarks of International Business Machines Corporation. LinuxAlmost all Linux distributions ship with rdist non setuid. If you have changed your rdist to run setuid you are probably vulnerable.NEC Corporation
NCR CorporationNCR is delivering a set of operating system dependent patches which contain an update for this problem . Accompanying each patch is a README file which discusses the general purpose of the patch and describes how to apply it to your system.
Recommended solution: pkginfo -x inet For inet 5.01.xx.xx: - PINET501 (Version later than 05.01.01.59)
The Santa Cruz OperationThe following releases of SCO Software are known to contain a version of rdist that is vulnerable:SCO OpenServer 5.0.2, 5.0.0 SCO Open Server Enterprise/Network System 2.0, 3.0 SCO UnixWare 2.0, 2.1 SCO TCP/IP 1.2.0, 1.2.1 Patches are being developed for the following releases: SCO OpenServer 5.0.2, 5.0.0 Sequent Computer SystemsSequent systems do not ship with rdist.Silicon Graphics, Inc.All SGI IRIX versions of rdist are not vulnerable.No action is required. (When using the find command on SGI IRIX systems, use -mount instead of - -xdev. The latter is not supported on SGI IRIX systems.) Sun Microsystems, Inc.The following patches correct the rdist vulnerability (Sun bug id 1258139), described in this advisory, on systems running Solaris 1.x or 2.x.
Architecture SunOS Solaris Patch MD5 checksum for rdist binary
- ---------------------------------------------------------------------------
SPARC 4.1.3 1.1 100383-07 5F2C2B782881FE18D2737B5FA0AEC489
4.1.3_U1 1.1.1 103823-01 B330358F4E66CD544B9B60AF453C5F2B
4.1.4 1.1.2 103824-02 419369cc4b3514a9c12b4cdac207fde7
5.3 2.3 101494-02 1DD34E9E7C50B2C863E30D67DFD1A905
5.4 2.4 103813-01 90DD81A4C32F7D583737F171B821386B
5.5 2.5 103815-01 C3BBE3F6758B0BBA7D45CB05009ED80E
5.5.1 2.5.1 103817-01 89735351119896FEB7469DCA76788561
X86 5.4 2.4 103814-01 EE4509D9CF87DBD29ABB7A72C8330F89
5.5 2.5 103816-01 3363670F316A06803ECCDD9FFAE95126
5.5.1 2.5.1 103818-01 8C2E8CFDE7A2AE6D5EC89139D592E71C
PowerPC 5.5.1 2.5.1 103819-01 C3FC0E54B23E4209496A4735D09DFFEF
These patches will be available through your local SunService and SunSoft Support Services organizations by 9:00 PDT Wednesday, July 24. They will also be available at the same time from SunSolve Online, via the URL The CERT Coordination Center staff thanks Michael Cooper This document is available from: http://www.cert.org/advisories/CA-1996-14.html CERT/CC Contact Information
Phone: +1 412-268-7090 (24-hour hotline) Fax: +1 412-268-6989 Postal address: CERT/CC personnel answer the hotline 08:00-17:00 EST(GMT-5) / EDT(GMT-4) Monday through Friday; they are on call for emergencies during other hours, on U.S. holidays, and on weekends. Using encryptionWe strongly urge you to encrypt sensitive information sent by email. Our public PGP key is available from If you prefer to use DES, please call the CERT hotline for more information. Getting security informationCERT publications and other security information are available from our web site
* "CERT" and "CERT Coordination Center" are registered in the U.S. Patent and Trademark Office.
NO WARRANTY Conditions for use, disclaimers, and sponsorship information
Copyright 1996 Carnegie Mellon University. Revision History
Jan. 15, 1998 Updated vendor information for NCR.
Sep. 24, 1997 Updated copyright statement
Nov. 27, 1996 Appendix A, Sun - updated patch information for
Solaris 1.1.2, SunOS 4.1.4.
Aug. 30, 1996 Information previously in the README was inserted into the
advisory.
Aug. 22, 1996 Appendix A, SGI - added note about using the find command.
Aug. 12, 1996 Appendix A, Hewlett-Packard - modified the entry.
July 30, 1996 Solution Section III.A - corrected two misprints in the
results of the find command.
July 24, 1996 Appendix A, Digital - added information.
IBM - put a new URL in the "To Order" section.
|
