The main module from the Media Server is its XMPP component, it has several responsibilities, including the authentication process.
The authentication process that will be used is based on the XEP-0070, to illustrate how it would work, here is a sequence diagram:
As described on XEP-0070, the Media Server will provide two types of HTTP authentication, Basic and Digest, both requests user's login and password as authentication mechanism, in this way, the Media Server has to have a mechanism where it will verify the passed password.
The authentication response and authorization request are already implemented, the next steps are implement the verify password mechanism and request confirmation process.
edit: changed the sequence diagram after discussed some points with Kev.