_____________________________________________________
               The Computer Incident Advisory Capability
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                           INFORMATION BULLETIN

                     SCO Home Directory Vulnerability
 
September 17, 1993 1115 PDT                                    Number D-24
__________________________________________________________________________
PROBLEM:   Home directories for "dos" and "asg" accounts insecure.
PLATFORM:  Systems using SCO Operating Systems (see list below).
DAMAGE:    Unauthorized system access, including privileged access.
SOLUTION:  Apply workaround described below.
__________________________________________________________________________
	
       Critical Information about SCO Home Directory Vulnerability

CIAC has received information of a vulnerability in SCO Operating Systems
that may permit unauthorized access to the "dos" and "asg" accounts.  The
following 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

The vulnerability results from the fact that the default home directories
for the "dos" and "asg" accounts are /tmp and /usr/tmp respectively, both
of which are writeable by all system users.  This situation may allow
unauthorized users to gain access to these accounts and the files that
they own.  The access may also be used to gain privileged access to the
system.

CIAC recommends that sites apply the following workaround to all affected
systems:

     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

Sites should also take steps to verify that the "dos" and "asg" accounts
have not been compromised.  The following command will display recent
logins to either of the accounts:

     last | egrep "dos|asg"

Should any login sessions be displayed, it is likely that the system has
been compromised.  The modification times of the DOS binaries on the
system should also be examined for evidence of recent modifications. If
any evidence of compromise exists, CIAC strongly recommends that the DOS
package of Operating System Extended Utilities be removed and re-installed
using custom(ADM).

If you have further questions regarding this vulnerability, you may
contact SCO Support and ask for more information concerning the "Home
Directory Security Vulnerability."  SCO may be reached as follows:

     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)

For additional information or assistance, please contact CIAC at 
(510) 422-8193 or send E-mail to ciac@llnl.gov. FAX messages to
(510) 423-8002.

Previous CIAC Bulletins and other information are available via anonymous
FTP from irbis.llnl.gov (IP address 128.115.19.60).

CIAC would like to acknowledge the efforts of both Christopher Durham of
the Santa Cruz Operation and the CERT Coordination Center in the
resolution of this issue.

PLEASE NOTE: Many users outside of the DOE and ESnet computing communities
receive CIAC bulletins.  If you are not part of these communities, please
contact your agency's response team to report incidents.  Your agency's team
will coordinate with CIAC.  The Forum of Incident Response and Security Teams
(FIRST) is a world-wide organization.  A list of FIRST member organizations
and their constituencies can be obtained by sending email to
docserver@first.org with an empty subject line and a message body containing
the line: send first-contacts.

This document was prepared as an account of work sponsored by an agency of
the United States Government.  Neither the United States Government nor the
University of California nor any of their employees, makes any warranty,
expressed or implied, or assumes any legal liability or responsibility for
the accuracy, completeness, or usefulness of any information, product, or
process disclosed, or represents that its use would not infringe privately
owned rights.  Reference herein to any specific commercial products, process,
or service by trade name, trademark manufacturer, or otherwise, does not
necessarily constitute or imply its endorsement, recommendation, or favoring
by the United States Government or the University of California.  The views
and opinions of authors expressed herein do not necessarily state or reflect
those of the United States Government nor the University of California, and
shall not be used for advertising or product endorsement purposes.