Finding Passwords

[John Nagle]

      The "trusted path" approach, as in ULTRIX, is the way to go, but 
it does present problems in the presence of dial-up lines, port selectors,
and such.  We used it in KSOS (a late 70s vintage high-security UNIX-like
system), but that system was for environments where all terminals were 
hard-wired.  

      We had two paths to the terminal, switched in the kernel.  The main
path was used for all user programs.  The trusted path was used only by
the "secure initiator", which handled logins and other security-related
functions.  Pushing "break" switched the terminal to the trusted path,
and the terminal stayed on the trusted path until the secure initiator
(a privileged application program) made a system call to switch it back.
The user could push break at any time to force this switch, and there
was no way a user program could prevent it.

     You can't do it in "getty"; it has to be in the kernel.   There
must be something the user can (and must) do that can't be intercepted
by any user program.

					John Nagle