X Server crashes on my VAXstation II GPX

[Tim Bell]

There have been some postings to comp.windows.x recently
concerning security under X.  I have run into a problem
that, at least partly, falls into the security arena.

I am running Ultrix-32 V3.1 (Rev. 9) UWS V2.1 on a
VAXstation II GPX.

I have a short program that will crash the X window server
on my VAXstation if it is run as a client on some other
machine.  This is a security concern because a user on any
machine allowed to connect to mine could reach out and crash
my window server whenever they want to.  Of course, the user
is usually me, because I am working with software
incorporating the color map manipulations that cause the
crash.

If the client and the server are the same machine, no
problem.  If the server is a VAX running Ultrix and UWS, and
the client is not, this program may or may not crash the
Xqdsg display server.  The following table is a summary of
the results of my testing so far:

 CLIENT       (O/S)                      DISPLAY SERVER          CRASH?
 -----------------------------------------------------------------------
 DEC MicroVAX (Ultrix-32 V3.1         |  DEC MicroVAX (Ultrix) |  NO
               Same machine as server)|                        |
 DECstation 3100 (Ultrix Worksystem   |                        |  NO
                  V2.0 Rev. 7)        |                        |
 DEC MicroVAX (VMS V5.2)              |                        |  NO
 SUN 3/260    (Sun O/S 4.1)           |                        |  YES
 SUN 3/110    (Sun O/S 3.5)           |                        |  YES
 IBM RT       (AIX/RT version 2.2.1)  |                        |  YES

The program runs fine if the server and client are both DEC
machines.  Running the client on a Sun or IBM RT and
attempting to display the output on the VAXstation is fatal
to my entire login on the VAXstation... I end up at the
d|i|g|i|t|a|l login screen.

This problem is also present under Ultrix-32 V3.0 (Rev 64) UWS V2.0

I would appreciate hearing from anyone who could shed some
light on the problem.  My demo program is a bit long to
post, but I will mail you a copy.


 Tim Bell        UCAR,  P.O. Box 3000    INTERNET: bellt at unidata.ucar.EDU
 (303)497-8636   Boulder, CO 80307           SPAN: 9596::BELL

 Tim Bell        UCAR,  P.O. Box 3000    INTERNET: bellt at unidata.ucar.EDU
 (303)497-8636   Boulder, CO 80307           SPAN: 9596::BELL