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CERT Advisory CA-96.14 - Vulnerability in rdist
From: cert-advisory () cert org (CERT Advisory)
Date: Wed, 24 Jul 1996 16:22:54 -0500
-----BEGIN PGP SIGNED MESSAGE----- ============================================================================= CERT(sm) Advisory CA-96.14 July 24, 1996 Topic: Vulnerability in rdist This advisory supersedes CA-91:20.rdist.vulnerability and CA-94:04.SunOS.rdist.vulnerability. - ----------------------------------------------------------------------------- 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. As we receive additional information relating to this advisory, we will place it in ftp://info.cert.org/pub/cert_advisories/CA-96.14.README We encourage you to check our README files regularly for updates on advisories that relate to your site. - ----------------------------------------------------------------------------- I. Description The 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. Impact On unpatched systems, anyone with access to a local account can gain root access. III. Solution We 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 vulnerable To 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) - regular files (-type f) - owned by root (-user root) - named rdist - setuid root (-perm -04000) Once found, those files will - have their names printed (-print) - have the setuid mode removed, but only if you type `y' in response to the prompt (-ok chown u-s '{}' \;) B. Obtain and install the appropriate patch Below is a list of the vendors who have reported to us as of the date of this advisory. Details are in Appendix A. Berkeley Software Design, Inc. Data General Corporation FreeBSD, Inc. Hewlett-Packard Company IBM Corporation Linux NEC Corporation The Santa Cruz Operation Sequent Computer Systems Silicon Graphics, Inc. Sun Microsystems, Inc. If your vendor's name is not on this list, please contact the vendor directly. Appendix A is reproduced in CA-96.14.README, which will be updated as we receive additional information. 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 from ftp://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. - --------------------------------------------------------------------------- The CERT Coordination Center staff thanks Michael Cooper (Michael.Cooper () Sun Com) for his work on resolving this problem. He is the maintainer of the publicly available version of rdist. - --------------------------------------------------------------------------- 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 CERT publications, information about FIRST representatives, and other security-related information are available for anonymous FTP 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 CERT advisories and bulletins, send your email address to cert-advisory-request () cert org 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. This file: ftp://info.cert.org/pub/cert_advisories/CA-96.14.rdist_vul http://www.cert.org click on "CERT Advisories" ......................................................................... Appendix A: Vendor Information Current as of July 24, 1996 See CA-96.14.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. 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 patches () bsdi com 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 the patches () bsdi com 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 Corporation ======================== Data 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. FreeBSD, Inc. ============= Versions affected: FreeBSD 2.0, 2.0.5, 2.1, 2.1-stable, and 2.2-current Versions corrected: 2.1-stable and 2.2-current as of 1996-07-11 Workaround: As root, execute the commands: # chflags noschg /usr/bin/rdist # chmod u-s,go-rx /usr/bin/rdist Patches: ftp://freebsd.org/pub/CERT/patches/SA-96:16/ For more information: ftp://freebsd.org/pub/CERT/advisories/SA-96:16/ Hewlett-Packard Company ======================= HP/UX 10.X is vulnerable, 9.X is not vulnerable. Patches are in process. IBM Corporation =============== AIX 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: chmod u-s /usr/bin/rdist AIX 3.2 ------- Apply the following fix to your system: APAR - IX59741 AIX 4.1 ------- Apply the following fix to your system: APAR - IX59742 To determine if you have this APAR on your system, run the following command: instfix -ik IX59742 AIX 4.2 ------- Apply the following fix to your system: APAR - IX59743 To determine if you have this APAR on your system, run the following command: instfix -ik IX59743 To Order -------- APARs may be ordered using FixDist or from the IBM Support Center. For more information on FixDist, reference URL: http://aix.boulder.ibm.com/pbin-usa/fixdist.pl/ 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. Linux ===== Almost all Linux distributions ship with rdist non setuid. If you have changed your rdist to run setuid you are probably vulnerable. NEC Corporation =============== EWS-UX/V(Rel4.2) not vulnerable EWS-UX/V(Rel4.2MP) not vulnerable UP-UX/V(Rel4.2MP) not vulnerable UX/4800 not vulnerable The Santa Cruz Operation ======================== The 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 Internet FastStart 1.0 SCO Open Server Enterprise/Network System 2.0, 3.0 SCO Open Desktop 2.0, 3.0 SCO Open Desktop Lite 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 SCO Internet FastStart 1.0 SCO UnixWare 2.1 Sequent Computer Systems ======================== Sequent systems do not ship with rdist. Silicon Graphics, Inc. ====================== All SGI IRIX versions of rdist are not vulnerable. No action is required. 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 103824-01 11BDEC384048CD42200BC1D0F25B61C9 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 http://sunsolve1.sun.com. -----BEGIN PGP SIGNATURE----- Version: 2.6.2 iQCVAwUBMfU59HVP+x0t4w7BAQFYwQQAwIfrbmurZeOQ+8APfXM3qI02G5UpUQfi 0Ynb4zldwGVkB97G+iE9mF9rfk3fmx3Ce3Nv27gEPbwjRmBqse//4XoQXn0JdfZN H3yisrDG9Dw822lHO3pdHddYBEejhmlvmpcDcui89uRE+VFGTajhqdi35JePGyRR NPwbJfRcUG0= =zidc -----END PGP SIGNATURE-----
Current thread:
- Re: vulnerability in vi under AIX 3.2 David A. Curry (Jul 23)
- Quota Trojan Jordy (Jul 24)
- <Possible follow-ups>
- Re: vulnerability in vi under AIX 3.2 Max Bloomfield (Jul 24)
- Re: vulnerability in vi under AIX 3.2 Bill Pemberton (Jul 24)
- CERT Advisory CA-96.14 - Vulnerability in rdist CERT Advisory (Jul 24)