CA-89:02
                                 CERT Advisory
                                 July 26, 1989
                               Sun Restore Hole
-----------------------------------------------------------------------------

A security hole has been found in SunOS restore.  This problem affects
SunOS 4.0, 4.0.1, and 4.0.3 systems.  It does not appear in SunOS 3.5.
The problem occurs because restore is setuid to root.  Without going
into details, is sufficient to say that this is a serious hole.  All
SunOS 4.0 installations should install this workaround.  Note that a
user does need to have an existing account to exploit this hole.

There are two workarounds that will fix the problem.  The first is
slightly more secure but has some side-effects.  

1) Make restore non-setuid by becoming root and doing a 
chmod 750 /usr/etc/restore

This makes restore non-setuid and unreadable and unexecutable by
ordinary users.

Making restore non-setuid affects the restore command using a remote
tape drive.  You will no longer be able to run a restore from another
machine as an ordinary user; instead, you'll have be root to do so.
(The reason for this is that the remote tape drive daemon on the
machine with the tape drive expects a request on a TCP privileged
port.  Under SunOS, you can't get a privileged port unless you are
root.  By making restore non-setuid, when you run restore and request
a remote tape drive, restore won't be able to get a privileged port,
so the remote tape drive daemon won't talk to it.)

2) If you do need to have some users run restore from remote tape
drives without being root, you can use the following workaround.

cd /usr/etc
chgrp operator restore
chmod 4550 restore

This allows the use of restore by some trusted group.  In this case,
we used the group 'operator', but you may substitute any other group
that you trust with access to the tape drive.  Thus, restore is still
setuid and vulnerable, but only to the people in the trusted group.

The 4550 makes restore readable and executable by the group you
specified, and unreadable by everyone else.

Sun knows about this problem (Sun Bug 1019265) and will put in a more
permanent fix in a future release of SunOS. 

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

J. Paul Holbrook
Computer Emergency Response Team (CERT)
Software Engineering Institute
Carnegie Mellon University
Pittsburgh, PA 15213-3890

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