COMMAND
	    DDB
SYSTEMS AFFECTED
	    FreeBSD, many other BSD stuff
PROBLEM
	    Brian Mitchell posted following.   DDB is the kernel debugger.  It
	    lets you debug the kernel upon  a panic or when you wish  to enter
	    it via a key sequence on the console. There appears to be a slight
	    problem though, you  can use DDB  to lower the  securelevel of the
	    system. The following shows one example:
	
	        # sysctl -w kern.securelevel=10
	        kern.securelevel: 0 -> 10
	        # Debugger("manual escape to debugger")
	        Stopped at      _Debugger+0x35: movb    $0,_in_Debugger.118
	        db> write securelevel 0
	        _securelevel                 0xa        =              0
	        db> cont
	        # sysctl kern.securelevel
	        kern.securelevel: 0
	        #
	
	    Also  you  can  a)  raise  your  privelege level (walk the process
	    list, find the cred stuff for the appropriate process, and  change
	    it, b)  make the  machine panic  c) remove  the code that prevents
	    you from doing any number of things while at a higher securelevel,
	    d) remove the code that  prevents you from removing the  code that
	    prevents you from doing things at a higher securelevel, etc.
SOLUTION
	    The most straightforward solution to  this is to simply not  allow
	    DDB to be  run when securelevel  > 0. Enclosed  is a simple  patch
	    against  2.2.1  to   do  this.   Note   that  FreeBSD  runs   with
	    securelevel -1, while  that's not case  with others so  apply this
	    solution only if  understund what's what  are you doing.   Anyway,
	    removing ddb would be also solution.
	
	    *** i386/i386/db_interface.c    Sat Aug 30 08:57:36 1997
	    --- i386/i386/db_interface.c.new        Sat Aug 30 09:00:43 1997
	    ***************
	    *** 241,246 ****
	    --- 241,256 ----
	            /*
	             * XXX
	    +        * Do nothing if the securelevel is > 0. The justification
	    +        * being that DDB can be used to lower the securelevel, so
	    +        * if we run > 0, we should not be able to run DDB at all.
	    +        * Modifying DDB to be securelevel friendly is not an option.
	    +        */
	    +       if(securelevel > 0)
	    +               return;
	    +
	    +       /*
	    +        * XXX
	             * Do nothing if the console is in graphics mode.  This is
	             * OK if the call is for the debugger hotkey but not if the call
	             * is a weak form of panicing.