CERT Advisory - Commodore Amiga UNIX finger Vulnerability

Fri Feb 12 15:32:42 UTC 1993

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CA-93:04                      CERT Advisory
                            February 12, 1993
               Commodore Amiga UNIX finger Vulnerability

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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. 

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

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