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DDN Security Bulletin 9109       DCA DDN Defense Communications System
23 July 91              Published by: DDN Security Coordination Center
                                     (SCC@NIC.DDN.MIL)  (800) 235-3155

                        DEFENSE  DATA  NETWORK
                          SECURITY  BULLETIN

The DDN  SECURITY BULLETIN  is distributed  by the  DDN SCC  (Security
Coordination Center) under  DCA contract as  a means of  communicating
information on network and host security exposures, fixes, &  concerns
to security & management personnel at DDN facilities.  Back issues may
be  obtained  via  FTP  (or  Kermit)  from  NIC.DDN.MIL  [192.67.67.20]
using login="anonymous" and password="guest".  The bulletin pathname is
SCC:DDN-SECURITY-yynn (where "yy" is the year the bulletin is issued
and "nn" is a bulletin number, e.g. SCC:DDN-SECURITY-9001).
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                   Patch for SunOS /usr/etc/rpc.mountd

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!                                                                       !
!     The following important  advisory was  issued by the Computer     !
!     Emergency Response Team (CERT)  and is being relayed unedited     !
!     via the Defense Communications Agency's Security Coordination     !
!     Center  distribution  system  as a  means  of  providing  DDN     !
!     subscribers with useful security information.                     !
!                                                                       !
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CA-91:09                        CERT Advisory
                                July 15, 1991
                     Patch for SunOS /usr/etc/rpc.mountd

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The Computer Emergency Response Team/Coordination Center (CERT/CC) has
received information concerning the availability of a security patch 
for /usr/etc/rpc.mountd in Sun Microsystems, Inc. operating systems.  
This problem will be fixed in SunOS 5.0.  Patches are available for
SunOS 4.1, and SunOS 4.1.1 through your local Sun answer centers 
worldwide as well as through anonymous ftp to ftp.uu.net (in ~ftp/sun-dist).
Patch ID and file information are as follows:

Fix                     Patch ID       Filename            Checksum
/usr/etc/rpc.mountd	100296-01      100296-01.tar.Z     01501   233

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

     If an access list of hosts within /etc/exports is a string 
     over 256 characters then the filesystem can be mounted by 
     everyone.
      
II.  IMPACT:

     Unauthorized remote hosts will be able to mount the filesystem.

III. SOLUTION:

     As root:

     1.  Move the existing rpc.mountd aside

         # mv /usr/etc/rpc.mountd /usr/etc/rpc.mountd.OLD

     2.  Install the new version

         # cp sun{3,3x,4,4c}/{4.1,4.1.1,4.1_PSR_A}/rpc.mountd /usr/etc
         # chown root.staff /usr/etc/rpc.mountd
         # chmod 755 /usr/etc/rpc.mountd

     3.  Kill the currently running rpc.mountd and restart it, or,
         reboot the system.  Systems currently mounting filesystems
         from this host will have interruptions in service either
         way.  

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If you believe that your system has been compromised, contact CERT/CC via
telephone or e-mail.

Computer Emergency Response Team/Coordination Center (CERT/CC)
Software Engineering Institute
Carnegie Mellon University
Pittsburgh, PA 15213-3890

Internet E-mail: cert@cert.sei.cmu.edu
Telephone: 412-268-7090 24-hour hotline:
           CERT/CC personnel answer 7:30a.m.-6:00p.m. EST,
           on call for emergencies during other hours.

Past advisories and other computer security related information are available
for anonymous ftp from the cert.sei.cmu.edu (192.88.209.5) system.