Alternative user authentication backend

Hello all!

As far as I can see, Seafile currently supports an internal user database and LDAP.

With software like Dovecot, it is possible to authenticate just by running a command with some auth credentials as arguments, and then checking the return code. Is an authentication method like this ever likely to be available?

(likely) Only if a (large) customer requests it or (possibly) if someone sends a tested and well working pull request.