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Security Bulletin 9305                  DISA Defense Communications System
February 16, 1993           Published by: DDN Security Coordination Center
                                      (SCC@NIC.DDN.MIL)   1-(800) 365-3642

                        DEFENSE  DATA  NETWORK
                          SECURITY  BULLETIN

  The DDN SECURITY BULLETIN is distributed by the DDN SCC (Security
  Coordination Center) under DISA contract as a means of communicating
  information on network and host security exposures, fixes, and concerns
  to security and management personnel at DDN facilities.  Back issues may
  be obtained via FTP (or Kermit) from NIC.DDN.MIL [192.112.36.5]
  using login="anonymous" and password="guest".  The bulletin pathname is
  scc/ddn-security-yynn (where "yy" is the year the bulletin is issued
  and "nn" is a bulletin number, e.g. scc/ddn-security-9305).
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!                                                                       !
!     The following important  advisory was  issued by the Computer     !
!     Emergency Response Team (CERT)  and is being relayed unedited     !
!     via the Defense Information Systems Agency's Security             !
!     Coordination Center  distribution  system  as a  means  of        !
!     providing  DDN subscribers with useful security information.      !
!                                                                       !
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===========================================================================
CA-93:04                      CERT Advisory
                            February 12, 1993
               Commodore Amiga UNIX finger Vulnerability

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

The CERT Coordination Center has received information concerning a
vulnerability in the "finger" program of Commodore Business Machine's
Amiga UNIX product.  The vulnerability affects Commodore Amiga UNIX
versions 1.1, 2.03, 2.1, 2.1p1, 2.1p2, and 2.1p2a.  Commodore is aware
of the vulnerability, and both a workaround and a patch are available.
Affected sites should apply either the workaround or the patch. 
Directions are provided below. 

If you have any further questions, contact Commodore's David Miller
via e-mail.  David's e-mail address is davidm@cdmvax.commodore.com.

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I.    Description

      The "finger" command in Amiga UNIX contains a security
      vulnerability.


II.   Impact

      Non-privileged users can gain unauthorized access to files.


III.  Solution

      Commodore has suggested a workaround and a patch, as follows:

      A. Workaround

         As root, modify the permission of the existing /usr/bin/finger
         to prevent misuse.

                # /bin/chmod 0755 /usr/bin/finger

      B. Patch

         As root, install the "pubsrc" package from the distribution tape. 

         In the file, "/usr/src/pub/cmd/finger/src/finger.c", add the line:

                setuid(getuid());

         immediately before the line reading:

                display_finger(finger_list);

         (Optionally) save a copy of the existing /usr/bin/finger and modify
         its permission to prevent misuse.

                # /bin/mv /usr/bin/finger /usr/bin/finger.orig
                # /bin/chmod 0755 /usr/bin/finger.orig

         In the directory, "/usr/src/pub/cmd/finger", issue the command:

                # cd /usr/src/pub/cmd/finger
                # make install

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The CERT Coordination Center wishes to thank Commodore Business
Machines for their response to this problem.
------------------------------------------------------------------------------ 

If you believe that your system has been compromised, contact the CERT
Coordination Center or your representative in FIRST (Forum of Incident
Response and Security Teams).

Internet E-mail: cert@cert.org
Telephone: 412-268-7090 (24-hour hotline)
           CERT personnel answer 7:30 a.m.-6:00 p.m. EST(GMT-5)/EDT(GMT-4),
           on call for emergencies during other hours.

CERT Coordination Center
Software Engineering Institute
Carnegie Mellon University
Pittsburgh, PA 15213-3890

Past advisories, information about FIRST representatives, and other
information related to computer security are available for anonymous FTP
from cert.org (192.88.209.5).


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*                                                                          *
*    The point of contact for MILNET security-related incidents is the     *
*    Security Coordination Center (SCC).                                   *
*                                                                          *
*               E-mail address: SCC@NIC.DDN.MIL                            *
*                                                                          *
*               Telephone: 1-(800)-365-3642                                *
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*    NIC Help Desk personnel are available from 7:00 a.m.-7:00 p.m. EST,   *
*    Monday through Friday except on federal holidays.                     *
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