OVERVIEW
When I was working with Kerberos, I did not find any good way for one process
to access the kerberos tickets of another.  All of the ways I found required
the accessing process to run as root.

I wrote this filesystem to expose the kerberos ticket caches of arbitrary
user ids as files.  So once you mount this, you will set one file per user id
that has kinit'ed.  Each file will contain the contents of the ticket cache.

EXAMPLE
$ ls /mnt/keymaster
0 1012 1040

$ cat /mnt/keymaster/1012
[kerberos cache contents]

ASSUMPTIONS
* This program assumes that you are using the FILE: type of ticket cache, and
that all of your ticket caches are in files of the form "/tmp/krb5cc_${PID}"

* This program assumes that root can access everyone's ticket files.

SECURITY CONSIDERATIONS
If you set KEYMASTER_PID to a process ID, only that process will be able to
open files in this filesystem.  This effectively allows you to restrict
access to a single process.

Of course, even after all is said and done, you still have a single process
which can access everyone's Kerberos tickets.  So this process has great power.

This program is not really useful for increasing security, but more useful for
preventing yourself from making accidental mistakes in the "chosen" process.
The chosen process no longer needs to run as root.

Colin Patrick McCabe
2012