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CA-93:13                         CERT Advisory
                               September 17, 1993
                        SCO Home Directory Vulnerability
- -----------------------------------------------------------------------------

The CERT Coordination Center has received information indicating that SCO
Operating Systems may be vulnerable to a potential compromise of system
security.  This vulnerability allows unauthorized access to the "dos" and
"asg" accounts, and, as a result of this access, unauthorized access to 
the "root" account may also occur.

The following releases of SCO products are affected by this vulnerability:

     SCO UNIX System V/386 Release 3.2 Operating System
     SCO UNIX System V/386 Release 3.2 Operating System Version 2.0
     SCO UNIX System V/386 Release 3.2 Operating System version 4.x
     SCO UNIX System V/386 Release 3.2 Operating System Version 4.0 with
         Maintenance Supplement Version 4.1 and/or Version 4.2
     SCO Network Bundle Release 4.x
     SCO Open Desktop Release 1.x
     SCO Open Desktop Release 2.0
     SCO Open Desktop Lite Release 3.0
     SCO Open Desktop Release 3.0
     SCO Open Server Network System Release 3.0
     SCO Open Server Enterprise System Release 3.0

CERT and The Santa Cruz Operation recommend that all sites using these SCO
products take action to eliminate the source of vulnerability from their
systems.  This problem will be corrected in upcoming releases of SCO
operating systems. 

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I.   Description

     The home directories of the users "dos" and "asg" are /tmp and
     /usr/tmp respectively. These directories are designed to have 
     global write permission. 

II.  Impact

     This vulnerability may allow unauthorized users to gain access to 
     these accounts. This vulnerability may also corrupt certain binaries 
     in the system and thus prevent regular users from running them, as well 
     as introduce a potential for unauthorized root access.

III. Solution

     All affected sites should follow these instructions:

     1. Log onto the system as "root"
     2. Choose the following sequence of menu selections from
        the System Administration Shell, which is invoked by
        typing "sysadmsh"

        a. Accounts-->User-->Examine-->
           [select the "dos" account] -->Identity
           -->Home directory-->Create-->Path-->
           [change it to /usr/dos instead of /tmp]--> confirm

        b. Accounts-->User-->Examine-->
           [select the "asg" account] -->Identity
           -->Home directory-->Create-->Path-->
           [change it to /usr/asg instead of /usr/tmp]--> confirm

     3. If DOS binaries have been modified, or sites are unable to 
        determine if modification has occurred, we strongly recommend 
        removing and reinstalling the DOS package of the Operating System 
        Extended Utilities.  This can be done using custom(ADM).

        Sites may also want to check their systems for signs of further
        compromise. This can be facilitated through the use of programs
        such as COPS. Other security advice and suggestions can be found
        in CERT's security checklist. This checklist may be obtained 
        through anonymous FTP from cert.org in pub/tech_tips/security_info.

        Note: COPS may be obtained from many sites, including via 
        anonymous FTP from cert.org in the pub/tools directory.

If you have further questions about this issue, please contact SCO Support 
and ask for more information concerning this CERT advisory, CA-93:13, "SCO 
Home Directory Vulnerability."

        Electronic mail: support@sco.COM

        USA/Canada: 6am-5pm Pacific Daylight Time (PDT)
        -----------
        1-800-347-4381  (voice)
        1-408-427-5443  (fax)

        Pacific Rim, Asia, and Latin American customers: 6am-5pm Pacific
        ------------------------------------------------ Daylight Time 
                                                         (PDT)
        1-408-425-4726  (voice)
        1-408-427-5443  (fax)

        Europe, Middle East, Africa: 9am-5:30pm British Standard Time (BST)
        ----------------------------
        +44 (0)923 816344 (voice)
        +44 (0)923 817781 (fax)

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The CERT Coordination Center wishes to thank Christopher Durham of the Santa
Cruz Operation for reporting this problem and his assistance in responding to
this problem.
- ---------------------------------------------------------------------------

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

Internet E-mail: cert@cert.org
Telephone: 412-268-7090 (24-hour hotline)
           CERT personnel answer 8:30 a.m.-5:00 p.m. EST(GMT-5)/EDT(GMT-4),
           and are 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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