CERT Advisory 013

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CERT Advisory

 · 4 years ago

  

 
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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: 

        ask_next@NeXT.COM [...!next!ask_next] 

Thanks, 
Computer Emergency Response Team 

- ------------------------------------------------------------------------------ 
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. 

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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: cert@cert.org 
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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