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This message is an update of the October 2, 1990 CERT Advisory (CA-90:06).
There is one correction and an update that you need to know about.

For Problem #2 SOLUTION, the following line has been added:

 # /etc/chmod 440 /usr/lib/NextPrinter/npd.old

This will disable the old printer program.  An updated copy of the CERT
Advisory has been included with this message.

NeXT is also making the new printer program, npd, available electronically
via anonymous ftp for Internet sites.  The archives sites are:

       nova.cc.purdue.edu
       umd5.umd.edu
       cs.orst.edu

In addition, NeXT has asked the CERT to announce that if anyone cannot get
it from the archives, NeXT Technical Support can provide it. Requests should
go to:

       [email protected] [...!next!ask_next]

Thanks,
Computer Emergency Response Team

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CA-90:06a                      CERT Advisory
                             October 3, 1990
                         NeXT's System Software

- -----------------------------------------------------------------------------
This message is to alert administrators of NeXT Computers of four
potentially serious security problems.

The information contained in this message has been provided by David Besemer,
NeXT Computer, Inc.  The following describes the four security problems,
NeXT's recommended solutions and the known system impact.

- ------------------------------------------------------------------------------

 Problem #1 DESCRIPTION:  On Release 1.0 and 1.0a a script exists in
 /usr/etc/restore0.9 that is a setuid shell script.  The existence of
 this script is a potential security problem.

 Problem #1 IMPACT:  The script is only needed during the installation
 process and isn't needed for normal usage.  It is possible for any
 logged in user to gain root access.

 Problem #1 SOLUTION:  NeXT owners running Release 1.0 or 1.0a should
 remove /usr/etc/restore0.9 from all disks.  This file is installed by
 the "BuildDisk" application, so it should be removed from all systems
 built with the standard release disk, as well as from the standard
 release disk itself (which will prevent the file from being installed
 on system built with the standard release disk in the future).  You
 must be root to remove this script, and the command that will remove
 the script is the following:

 # /bin/rm /usr/etc/restore0.9

                                   ---

 Problem #2 DESCRIPTION:  On NeXT computers running Release 1.0 or
 1.0a that also have publicly accessible printers, users can gain
 extra permissions via a combination of bugs.

 Problem #2 IMPACT:  Computer intruders are able to exploit this security
 problem to gain access to the system.  Intruders, local users and remote
 users are able to gain root access.

 Problem #2 SOLUTION:  NeXT computer owners running Release 1.0 or
 1.0a should do two things to fix a potential security problem.
 First, the binary /usr/lib/NextPrinter/npd must be replaced with a
 more secure version.  This more secure version of npd is available
 through your NeXT support center.  Upon receiving a copy of the more
 secure npd, you must become root and install it in place of the old
 one in /usr/lib/NextPrinter/npd.  The new npd binary needs to be
 installed with the same permission bits (6755) and owner (root) as
 the old npd binary.  The commands to install the new npd binary are
 the following:

 # /bin/mv /usr/lib/NextPrinter/npd /usr/lib/NextPrinter/npd.old
 # /bin/mv newnpd /usr/lib/NextPrinter/npd
         (In the above command, "newnpd" is the npd binary
         that you obtained from your NeXT support center.)
 # /etc/chown root /usr/lib/NextPrinter/npd
 # /etc/chmod 6755 /usr/lib/NextPrinter/npd
 # /etc/chmod 440 /usr/lib/NextPrinter/npd.old

 The second half of the fix to this potential problem is to change the
 permissions of directories on the system that are currently owned and
 able to be written by group "wheel".  The command that will remove
 write permission for directories owned and writable by group "wheel"
 is below.  This command is all one line, and should be run as root.

 # find / -group wheel ! -type l -perm -20 ! -perm -2 -ls -exec chmod
 g-w {} \; -o -fstype nfs -prune

                                   ---

 Problem #3 DESCRIPTION:  On NeXT computers running any release of the
 system software,  public access to the window server may be a
 potential security problem.

 The default in Release 1.0 or 1.0a is correctly set so that public access
 to the window server is not available.  It is possible, when upgrading from
 a prior release, that the old configuration files will be reused.  These
 old configuration files could possibly enable public access to the window
 server.

 Problem #3 IMPACT:  This security problem will enable an intruder to gain
 access to the system.

 Problem #3 SOLUTION:  If public access isn't needed, it should be disabled.

 1. Launch the Preferences application, which is located in /NextApps
 2. Select the UNIX panel by pressing the button with the UNIX
    certificate on it.
 3. If the box next to Public Window Server contains a check, click on
    the box to remove the check.

                                   ---

 Problem #4 DESCRIPTION: On NeXT computers running any release of the
 system software, the "BuildDisk" application is executable by all users.

 Problem #4 IMPACT:  Allows a user to gain root access.

 Problem #4 SOLUTION: Change the permissions on the "BuildDisk" application
 allowing only root to execute it.  This can be accomplished with the
 command:

 # chmod 4700 /NextApps/BuildDisk

 To remove "BuildDisk" from the default icon dock for new users, do the
 following:

 1. Create a new user account using the UserManager application.
 2. Log into the machine as that new user.
 3. Remove the BuildDisk application from the Application Dock by dragging
    it out.
 4. Log out of the new account and log back in as root.
 5. Copy the file in ~newuser/.NeXT/.dock to /usr/template/user/.NeXT/.dock
       (where ~newuser is the home directory of the new user account)
 6. Set the protections appropriately using the following command:
       # chmod 555 /usr/template/user/.NeXT/.dock
 7. If you wish, with UserManager, remove the user account that you created
    in step 1.

 In release 2.0, the BuildDisk application will prompt for the root password
 if it is run by a normal user.

- -----------------------------------------------------------------------------
CONTACT INFORMATION

For further questions, please contact your NeXT support center.

NeXT has also reported that these potential problems have been fixed in
NeXT's Release 2.0, which will be available in November, 1990.

Thanks to Corey Satten and Scott Dickson for discovering, documenting, and
helping resolve these problems.

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

Internet E-mail: [email protected]
Telephone: 412-268-7090 24-hour hotline: CERT personnel answer
          7:30a.m.-6:00p.m. EST, on call for
          emergencies other hours.

Past advisories and other information are available for anonymous ftp
from cert.org (192.88.209.5).


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