c2s startup
pipe init
 - create socketpair
 - fork
 - attach pair to stdio
 - exec prog

Commands return OK or NO, followed by return values

Init:

[auth process running]
<<< OK USER-EXISTS GET-PASSWORD CHECK-PASSWORD SET-PASSWORD CREATE-USER DESTROY-USER FREE

>>> USER-EXISTS user [realm]
<<< OK
<<< NO

>>> GET-PASSWORD user [realm]
<<< OK encoded_pass
<<< NO

>>> CHECK-PASSWORD user encoded_pass [realm]
<<< OK
<<< NO

>>> SET-PASSWORD user encoded_pass [realm]
<<< OK
<<< NO

>>> CREATE-USER user [realm]
<<< OK
<<< NO

>>> DELETE-USER user [realm]
<<< OK
<<< NO

>>> FREE
[auth process exits]
