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CA-93:19                         

Last revised:  September 19, 1997.  Updates - Added Sun patch information.



                                CERT Advisory

                               December 16, 1993

                      Solaris System Startup Vulnerability

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The CERT Coordination Center has received information concerning a 

vulnerability in the system startup scripts on Solaris 2.x and Solaris x86

systems.  The changes described below will be integrated into the upcoming

Solaris release.



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I.   Description



     If fsck(8) fails during system boot, a privileged shell is run

     on the system console. This behavior can represent a security

     vulnerability if users, who would normally not have root access,

     have physical access to the console at boot time.  An attacker

     can force the failure to occur.



II.  Impact



     This vulnerability allows anyone with physical access to the

     system console to gain root access.



III. Solution



     A simple change to each of two system scripts can be used to

     close this potential security hole. The new behavior will cause the

     system to run the privileged shell only if the user at the console

     enters the correct root password.



     If you wish to make the change on your own systems, edit both

     /sbin/rcS and /sbin/mountall, changing every occurrence of:



                /sbin/sh < /dev/console

     to:

                /sbin/sulogin < /dev/console



     As distributed by Sun, /sbin/rcS contains one occurrence of this

     string, at line 152; and /sbin/mountall contains two, one at line

     66 and one at line 250.



     Once these changes are made, sulogin will request the root

     password in the event fsck(8) fails, before starting a privileged shell.

     The success or failure of sulogin will be logged in /var/adm/sulog.



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The CERT Coordination Center wishes to thank Sun Microsystems, Inc.

for their support in responding 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 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 info.cert.org.



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UPDATES



September 19, 1997

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BUG 1124898 is fixed in Solaris 2.4



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Revision history



Sept. 19, 1997.  Updates - Added Sun patch information.

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