CERT Advisory - SunOS File/Directory Permissions

CERT Advisory cert-advisory-request at cert.org
Thu Feb 4 18:53:27 UTC 1993

CA-93:03                         CERT Advisory
                               February 3, 1993
                       SunOS File/Directory Permissions

The default permissions on a number of files and directories in SunOS
4.1, 4.1.1, 4.1.2, and 4.1.3 are set incorrectly.  These problems are
relevant for the sun3, sun3x, sun4, sun4c, and sun4m architectures.
They have been fixed in SunOS 5.0.  (Note that SunOS 5.0 is the operating
system included in the Solaris 2.0 software distribution.)

An updated patch to reset these permissions is available from Sun.
CERT has seen an increasing number of attackers exploit these problems
on systems and we encourage sites to consider installing this patch.


I.   Description

     File permissions on numerous files were set incorrectly in the
     distribution tape of 4.1.x.  A typical example is that a file which
     should have been owned by "root" was set to be owned by "bin".

     Not all sites will need or want to install the patch for this problem.
     The decision of what user id should own most system files and
     directories depends on the administrative practices of the site.
     It is quite reasonable to run a system where the majority
     of files are owned by "bin" as long as the entire system is run in
     a manner consistent with that practice.  As distributed, the SunOS
     configuration expects most system files to be owned by "root".
     The fact that some are not creates security problems.

     Therefore, sites that are running the SunOS versions listed above
     as distributed should install the patch described below.
     Sites that have made an informed choice to configure their system
     differently may instead want to review the patch script and
     consider which, if any, of the changes should be made on their system.

II.  Impact

     Depending on the specific configuration of the local site,
     the default permissions may allow local users to gain "root" access.

III. Solution

     1) Sun has provided a script to reset file and directory permissions
        to their correct values.  The script is available in Sun's
	Patch #100103 version 11.  This patch can be obtained via
	local Sun Answer Centers worldwide as well as through
	anonymous FTP from the ftp.uu.net ( system
	in the /systems/sun/sun-dist directory.

              Patch ID     Filename             Checksum
              100103-11    100103-11.tar.Z      19847   6

        Please note that Sun Microsystems sometimes updates patch files.
        If you find that the checksum is different please contact
        Sun Microsystems or CERT for verification.

     2) Uncompress the file, extract the contents of the tar archive,
        and review the README file.

             % uncompress 100103-11.tar.Z
             % tar xfv 100103-11.tar
             % cat README

     3) This patch will reset the group ownership of certain files to
        either "staff" or "bin".  Make sure you have entries in
        the "/etc/group" file for these accounts.

             % grep '^staff:' /etc/group
             % grep '^bin:' /etc/group
        If you do not have both of these you will need to either add the
        missing account(s) or modify the patch script (4.1secure.sh)
        to reflect group ownerships appropriate for your site.
        (Note that the security problems are fixed by the ownerships and
        mode bits specified in the patch - not by the group ownerships.
        Therefore, changing the group ownerships does not invalidate
        the patch.)

     4) As "root", run the patch script.

              # sh 4.1secure.sh

        This patch fixes Sun BugId's 1046817, 1047044, 1048142, 1054480,
	1037153, 1039292, and 1042662.

     5) The patch script will set "/usr/kvm/crash" to mode 02700 owned
        by "root".  While this is not insecure, since only "root" can run
	the program, CERT recommends that the setgid bit be removed to
	prevent abuse if world execute permission were to be added
	some time later.
	As "root", make "/usr/kvm/crash" not a set-group-id program.

             # chmod 755 /usr/kvm/crash


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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