this is a patch for x11r6.1's xdm. 
it will prevent the root from logging on through xdm. 

why?
    "... the patient cracker can guess the root passwd by
trial and error without a risk because the xdm doesn't log 
those failed attempts ..."
                --steven flick, srf@aluxpo.micro.lucent.com


to install this patchs (i have tested the following on sunos/solaris machines) 

1.assume that you have built the x11r6.1 tree at /opt/X11/X11R6:
    use the verify.c.x11r6.1 to overwrite the 
       /opt/X11/X11R6/src/xc/programs/xdm/greeter/verify.c
    cd /opt/X11/X11R6/src/xc/programs/xdm/greeter
    /opt/X11/X11R6/bin/xmkmf
    make 
    make install    
    (you must do this under /opt/X11/X11R6/src/xc/programs/xdm/greeter, otherwise
     you may lose your configuration files)
or for secure
    cp /opt/X11/X11R6/src/xc/programs/xdm/greeter/libXdmGreet.so.1.0 \
       /opt/X11/X11R6/lib/X11/xdm/
    make clean
    ( on sunos4.1.x machines, you may need run ldconfig as root,
         # cd /opt/X11/X11R6/lib/X11/xdm
         # ldconfig /opt/X11/X11R6/lib/X11/xdm
    )
note: you don't have to restart xdm after you installed the patch.
(because libXdmGreet.so.1.0 is just like a dynamically linked module of xdm)

2. assume that you have built the x11r5 tree at /usr/local/X11R5:
    use the verify.c.x11r5 to overwrite the 
       /usr/local/X11R5/src/mit/clients/xdm/verify.c
    cd /usr/local/X11R5/src/mit/clients/xdm
    /usr/local/X11R5/bin/xmkmf
    make 
    cp /usr/local/X11R5/src/mit/clients/xdm/xdm /usr/local/X11R5/bin/xdm
    (don't use make install, it will overwrite your configuration files)
    make clean
    su as root
    kill -9 <xdm-daemon-pid>
    restart a new deamon, e.g.
          /usr/local/X11R5/bin/xdm -config /usr/local/X11R5/lib/X11/xdm/xdm-config


by tianhua han, than@lucent.com
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