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SuSE Linux: Version 6.2
After the konfiguration of the graphical login kdm or xdm other (linux) computers are able to access the running login manager via the command X -query computername. This is no problem when using the xdm, but if you are using kdm it is possible that everybody can shutdown the computer using the `shutdown' dialog of the kdm login screen. Even if the attacker does not have an account on the affected computer he can shut it down.
Please edit the file /usr/X11R6/lib/X11/xdm/Xaccess. Search for the lines:
# In all cases, xdm uses the first entry which matches the terminal; # for IndirectQuery messages only entries with right hand sides can # match, for Direct and Broadcast Query messages, only entries without # right hand sides can match. # * #any host can get a login windowand near the end of the file
# The nicest way to run the chooser is to just ask it to broadcast # requests to the network - that way new hosts show up automatically. # Sometimes, however, the chooser can't figure out how to broadcast, # so this may not work in all environments. # * CHOOSER BROADCAST #any indirect host can get a chooserand replace them by the following lines. Only a `!' character is added before the `*' and the comment is changed.
# In all cases, xdm uses the first entry which matches the terminal; # for IndirectQuery messages only entries with right hand sides can # match, for Direct and Broadcast Query messages, only entries without # right hand sides can match. # !* #no host can get a login windowbzw.
# The nicest way to run the chooser is to just ask it to broadcast # requests to the network - that way new hosts show up automatically. # Sometimes, however, the chooser can't figure out how to broadcast, # so this may not work in all environments. # !* CHOOSER BROADCAST #no indirect host can get a chooser
After this changes and a restart of the xdm/kdm login manager the xdm/kdm can only be accessed by the X-Server started by xdm/kdm. Hosts trying to access it over the network are denied.
Keywords: KDM, XDM, KDE, SHUTDOWN
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