Virtual User/Alternative Authorization Methods

[Jeff Breitner]

Hello Alain, hope the squirrel battle is going well.

Looked over both the IMAP and IPOP server sources to see what needs to be
done to support various authentication methods.  Here's the goals that I
think are important:

1.  Support normal passwd/shadow & PAM authentication methods
2.  Support alternative-location crypt'd/SHA passwd files for virtual
domains
3.  (Eventually) support LDAP/MySQL since this is gaining in popularity for
virtual user systems
4.  Provide measures for the daemon to run as a neutered user on the system
for virtual logins

With repsect to imap4d, the obvious place to build this is in login.c.  It
appears that the username/password is checked here regardless if cleartext
or cyphered passwords are used.  The issue to overcome is that the rest of
the sources use the struct passwd/struct shadow for the mailbox & user
information.  I don't know how difficult it would be to use your own
structure set upon authentication that contains path to the mailbox, mailbox
name, user:group to setuid, etc.