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CERT* Advisory CA-97.23

Original issue date: September 16, 1997



Last Revised: December 9, 1998

              Updated vendor information for Sun Microsystems, Inc.



              A complete revision history is at the end of this file.





Topic: Buffer Overflow Problem in rdist

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The CERT Coordination Center has received reports of a vulnerability in rdist

that enables anyone with access to a local account to gain root privileges.

This is not the same vulnerability as the one discussed in CA-96.14.



Section III.A contains instructions on how to determine if your site is

vulnerable. If your implementation of rdist is vulnerable, the CERT/CC team

encourages you to follow your vendor's instructions (Sec. III.B and Appendix

A) or install a freely available version of the rdist program that is not

installed as set-user-id root and is, therefore, not susceptible to the

exploitation described in this advisory (Sec. III.C).



For information on the earlier problem with rdist, see

      http://info.cert.org/pub/cert_advisories/CA-96.14.rdist_vul



We will update this advisory as we receive additional information.

Please check our advisory files regularly for updates that relate to your

site.



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I.   Description



     The rdist program is a UNIX Operating System utility used to

     distribute files from one host to another. On some systems, rdist

     opens network connections using a privileged port as the source port.

     This requires root privileges, and to attain these privileges rdist on

     such systems is installed set-user-id root.



     A new vulnerability has been found in some set-user-id root

     implementations of rdist. The vulnerability lies in the function

     expstr(), where macros supplied as arguments are expanded using

     sprintf(). It is possible to overwrite stack frames and call specially

     pre-crafted native machine code. If the appropriate machine code is

     supplied, an attacker can execute arbitrary programs (such as the

     shell) with set-user-id root privileges.



     Note that this vulnerability is distinct from that discussed in CERT

     advisory CA-96.14.





II.  Impact



     On systems with a vulnerable copy of rdist, 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 vulnerable and, if it is, to turn off rdist while you decide

     how to proceed.



     If your system is vulnerable and you need the functionality that rdist

     provides, you should install a vendor patch (Section B). Until you can

     do so, you may want to use 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

     (Section C).



     A. How to check for set-user-id root versions of rdist



        To find set-user-id root versions of rdist and to disable the

        programs that are possibly 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 three lines using backslashes.



             find FILE_SYSTEM_NAMES -xdev -type f -user root \

                    -name '*rdist*' -perm -04000 -exec ls -l '{}' \; \

                    -ok chmod 0500 '{}' \;



        This command will find all files on a system that

            - are only in the file system you name (FILE_SYSTEM_NAMES -xdev)

            - are regular files (-type f)

            - are owned by root (-user root)

            - have "rdist" as a component of the name (-name '*rdist*')

            - are setuid (-perm -04000)



        Once found, those files will

            - have their names and details printed (-exec ls -l '{}')

            - have the setuid mode removed (making the file available

              only to root) but only if you type `y' in response to the

              prompt (-ok chmod 0500 '{}' \;)



     B. Obtain and install the appropriate patch



        Below is a list of vendors who have provided information for this

        advisory. Details are in Appendix A, and we will update the appendix

        as we receive more information.



               Berkeley Software Design, Inc. (BSDI)

               Caldera

               Digital Equipment Corp.

               FreeBSD, Inc.

               Hewlett-Packard Company

               IBM Corporation

               NEC Corporation

               NCR Corporation

               The Santa Cruz Operation, Inc. (SCO)

               Siemens-Nixdorf

               Silicon Graphics Inc. (SGI)

               Sun Microsystems, 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 from



              http://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 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.



        Some sites with sufficient expertise use the ssh program in

        conjunction with rdist, instead of using rcmd or rsh. If you have

        the expertise, you may want to implement this configuration.



        For further details on this option see "Ssh (Secure Shell) FAQ -

        Frequently asked questions," Section 4.4, "Can I use rdist with ssh?"

        It is available from



                http://www.uni-karlsruhe.de/~ig25/ssh-faq/ssh-faq-4.html



        For details on how to obtain ssh, see FAQ Section 3.4, "Where can I

        obtain ssh?" This section can be found in



            http://www.uni-karlsruhe.de/~ig25/ssh-faq/ssh-faq-3.html





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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)

=====================================

  BSDI shipped a patch for this for our 2.1 release (U210-018) when

  the original Bugtraq advisory was released.  The 3.0 version of

  rdist is not vulnerable and in fact is no longer even setuid.



Caldera

=======



  This message is to inform CERT that neither Caldera Network Desktop

  nor Caldera OpenLinux ship rdist SUID and are thus not vulnerable.

  See our advisory on this subject at:



        http://www.caldera.com/tech-ref/security/SA-1997.23.txt



Digital Equipment Corp.

=======================

  This reported problem is not present for Digital's ULTRIX or Digital UNIX

  Operating Systems Software.



                                DIGITAL EQUIPMENT CORPORATION

                                -----------------------------



FreeBSD, Inc.

=============

  2.1.0 is vulnerable.

  2.1.5, 2.1.6 and 2.1.7 are and 2.1-stable are not. In any case, upgrading

  to 2.1.7 or even better, 2.1-stable should be considered.

  If there is demand, we'll release a patch for 2.1.0



  All 2.2 releases, 2.2-stable and FreeBSD-current are not vulnerable.





Hewlett-Packard Company

=======================

  HP is -not- vulnerable; the problem didn't exist in 9.X, and has been fixed

  in 10.X with Security Bulletin #36 (HPSBUX9608-036) last year.  Patch

  numbers change frequently because of cumulative patching, so please check

  current patch ID information either by bulletin or by platform/release at

  our HP Electronic Support Center in the "Security Patch Matrix," which is

  updated every 24 hours.



 1)  From your Web browser, access the URL:



       http://us-support.external.hp.com (US,Canada,Asia-Pacific,

       and Latin-America)



       http://europe-support.external.hp.com  (Europe)



 2)  On the HP Electronic Support Center main screen, select the

     hyperlink "Support Information Digests".





 3)  On the "Welcome to HP's Support Information Digests" screen,

     under the heading "Register Now", select the appropriate hyperlink

     "Americas and Asia-Pacific", or "Europe".



 4)  On the "New User Registration" screen, fill in the fields

     for the User Information and Password and then select the button

     labeled "Submit New User".



 5)  On the "User ID Assigned" screen, select the hyperlink

     "Support Information Digests".



  **Note what your assigned user ID and password are for future

  reference.



 6)  You should now be on the "HP Support Information Digests Main"

     screen.  You might want to verify that your email address is

     correct as displayed on the screen.  From this screen, you may

     also view/subscribe to the digests, including the security

     bulletins digest.



     To get a patch matrix of current HP-UX and BLS security

     patches referenced by either Security Bulletin or Platform/OS,

     click on following screens in order:

        Technical Knowledge Database

        Browse the HP Security Bulletins Archive

        HP-UX Security Patch Matrix





IBM Corporation

===============

  All versions of AIX are vulnerable to this buffer overflow.  There is

  no 3.2 fix.  It is recommended that 3.2 customers upgrade to a higher

  level.  The following APARs will be available for AIX version 4

  soon.



  AIX 3.2:  upgrade to 4.1.5 or higher

  AIX 4.1:  IX70876

  AIX 4.2:  IX70875



   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

===============

  The following systems are NOT affected by this vulnerability:



        UX/4800

        UX/4800(64)

        EWS-UX/V(Rel4.2MP)

        EWS-UX/V(Rel4.2)

        UP-UX/V(Rel4.2MP)



  To report a new vulnerability, contact .



NCR Corporation

===============



NCR 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:



Apply one of the following patches depending on the revision of the

inet package installed on your system. To check its version execute:



        pkginfo -x inet



For inet 5.01.xx.xx: - PINET501 (Version later than 05.01.01.59)

For inet 6.01.xx.xx: - PINET601 (Version later than 06.01.00.19)

For inet 6.01.xx.xx: - PINET601 (Version later than 06.02.00.01)



OpenBSD

=======



  OpenBSD does not have this problem.  None of the versions of rdist

  distributed are setuid or setgid.





The Santa Cruz Operation, Inc. (SCO)

====================================

  SCO has determined that the following SCO operating systems are

  not vulnerable:



  - SCO CMW+ 3.0

  - SCO Open Desktop/Open Server 3.0

  - SCO OpenServer 5.0

  - SCO UnixWare 2.1





Siemens-Nixdorf Informationssysteme AG

======================================



 Rdist has not been shipped with ReliantUNIX versions prior to 5.43C.

 The latest ReliantUNIX-Y/N version 5.43C contains a vulnerable rdist.



 For this version we recommend to remove the set-user-id root bit from

 /usr/ucb/rdist following the instructions given in section III.A.



 ReliantUNIX-Y/N 5.44A will be shipped with rdist 6.1.3.

 Patches for ReliantUNIX-N/Y 5.43C are available on requirement.

 Please ask SNI's customers service for details."





Silicon Graphics Inc. (SGI)

===========================



Silicon Graphics Inc. issued Security Advisory, "IRIX ordist

Buffer Overrun Vulnerability," 19970509-02-PX, August 5, 1997.



Patches are available via anonymous FTP and your service/support provider.



The SGI anonymous FTP site is sgigate.sgi.com (204.94.209.1) or its

mirror, ftp.sgi.com.   Security information and patches can be found

in the ~ftp/security and ~ftp/patches directories, respectfully.



For subscribing to the wiretap mailing list and other SGI security related

information, please refer to the Silicon Graphics Security Headquarters

website located at:



             http://www.sgi.com/Support/security/security.html





Sun Microsystems, Inc.

======================



Please refer to Sun Microsystems, Inc. Security Bulletin, "rdist," Number:

#00179, distributed November 18, 1998 for additional information relating to

this vulnerability.



Patches and Checksums are available to all Sun customers via World Wide Web at:

        http://sunsolve.sun.com/sunsolve/pubpatches/patches.html>



Sun security bulletins are available via World Wide Web at:

        http://sunsolve.sun.com/pub-cgi/secbul.pl>





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The CERT Coordination Center thanks Hiroshi Nakano of Ryukoku University,

Japan for reporting this problem. We also thank Wolfgang Ley of DFN-CERT

for his assistance with the Solutions section of the 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

         http://info.cert.org/pub/CERT_PGP.key



Getting security information

   CERT publications and other security information are available from

        http://www.cert.org/

        http://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



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Copyright 1997, 1998 Carnegie Mellon University. Conditions for use,

disclaimers, and sponsorship information can be found in

http://www.cert.org/legal_stuff.html and

http://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: http://info.cert.org/pub/cert_advisories/CA-97.23.rdist

           http://www.cert.org

               click on "CERT Advisories"





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Revision history



Dec. 9, 1998  Updated vendor information for Sun Microsystems, Inc.

May 27, 1998   Updated vendor information for Sun Microsystems.

Jan. 15, 1998  Updated vendor information for NCR.

Nov. 14, 1997  Updated vendor information for Siemens-Nixdorf.

Oct. 3, 1997   Appendix A - added information for Caldera.

Sept. 30, 1997 Updated copyright statement

Sept. 15, 1997 Appendix A - added information for OpenBSD and



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