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-
- Xwall version 2.0
-
- INTRODUCTION
-
- Are you tired of seeing wall messages splatting across every xterm
- on an X display? We decided to change the way the wall worked in
- the presence of X.
-
- We made an xwalld daemon that would attach to the X display and listen
- for messages from the xwall program. The xwalld daemon is hardy enough
- to survive server resets and X terminals disappearing for a while. The
- xwall program passes the message to the xwalld using selections. The
- message passing is done in accordance with the ICCCM.
-
- Later, we added the ability to capture console messages to walld.
-
- SECURITY
-
- We have patched R4 xdm to issue the server key to root. We feel that this
- is not a security problem. Root can always assume the identity of the
- user to gain access to the X display. Apply xdm.patch to enact this
- change. We run most displays with authorization turned on and server
- grabbing turned off. This allows wall messages to appear when nobody
- is logged in.
-
- Both xwalld and xwall are setuid root programs. We have carefully examined
- both programs for security loop holes. Xwalld needs to run as root to be
- able to connect to the X display when nobody is logged in. Xwall needs to
- run as root to be able to switch the uid when a user is using a remote
- X display.
-
- CHANGES FOR X11R5
-
- The xwalld daemon no longer respawn itself when the X server connection
- is lost. This was required for R4, because there was no way to have xdm
- start xwalld when nobody was logged in. This functionality is provided
- in R5 with the Xsetup script. Xwalld will automatically be configured to
- respawn for R4 and not respawn for R5.
-
- Since the xconsole client is provided with R5, the console support has
- been withdrawn from xwalld.
-
- INSTALLATION
-
- For X11R4:
-
- In addition to installing the programs, you should install xdm.patch.
- I have also included our modified copy of the 4.3 BSD /bin/wall program.
- It checks the utmp entries for X connections. It attempts to use xwall
- and falls back to the old method if xwall fails. Be sure to adjust the
- path used to call xwall to match your local installation.
-
- If you want xwall messages to appear when nobody is logged in,
- use something like the following in your xdm-config.
-
- DisplayManager._0.authorize: true
- DisplayManager._0.authFile: /usr/adm/xdm/auth-server
- DisplayManager._0.grabServer: false
-
- For X11R5:
-
- In addition to installing the programs. Look at the example Xsetup
- files and change your xdm Xsetup file to issue the keys to root and
- start xwalld. Also modify your Xreset file to revoke the keys.
-
-
- TESTED PLATFORMS
-
- Xwall and xwalld have been installed and tested on the following platforms:
-
- DecStation 3100, Ultrix 3.1 & 4.0 & 4.2 (Using X11R4/R5, not DecWindows)
- VaxStation 3200, Ultrix 3.1 (Using X11R4, not DecWindows)
- Sun 4/100, SunOS 4.1
- Sun 3/50, SunOS 4.1
- IBM RT, AOS 4.3
- Hp bobcat, BSD 4.3
- Convex C220 ConvexOS 9.0 (X11R4)
- Cray Y-MP8/864 UNICOS 5.1.11 (Using X11r4, not r3 as supplied by CRI)
-
- Xwall and xwalld have also been tested with NCD-16 X terminals.
-
- FEEDBACK
-
- I welcome any feedback that you care to give. Of course, I am interested
- in your success stories. I will also try to help you if you have problems.
- However, I cannot make any promise of support.
-
- Tim Theisen Department of Computer Sciences
- tim@cs.wisc.edu University of Wisconsin-Madison
- uwvax!tim 1210 West Dayton Street
- (608)262-0438 Madison, WI 53706
-