Asking for root passwd when booting single user

[Karl Kleinpaste]

dieter at titan.nmt.edu writes:
   > How can I set the system to ask for the root passwd, when booting single
   > user ?

   % cat /.profile
   PATH=/usr/local:/etc:/usr/etc:/usr/ucb:/usr/bin:/bin:.
   export PATH TERM
   trap exit 2 3 15
   login root

There is a very small/short window of vulnerability, while sh is starting
up and evaluating the PATH= and export lines.  It is very, *very* small
and hence in practice is no problem.  But the hole is still there in this
example.  Give a determined abuser a few hours and he may succeed.

We accomplish approximately the same thing with a program /bin/singleuser
which protects itself from all `reasonable' signals and then demands the
root password, with an N-minute timeout (don't remember N just now).  It's
the 1st line in /.profile.

--Karl