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CA-93:04a                     CERT Advisory
                            February 18, 1993
      REVISION NOTICE: Commodore Amiga UNIX finger Vulnerability
				   
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	       *** THIS IS A REVISED CERT ADVISORY ***
	       *** IT CONTAINS UPDATED INFORMATION ***

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, and
directions are provided below. 

The Commodore contact e-mail address given in CERT Advisory CA-93:04
was incorrect.  This revised advisory provides the correct e-mail
address.  If you have any further questions, contact David Miller of
Commodore via e-mail at davidm@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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