In the need of a WebDAV functionnality that could allow one to share users personal directories with automated authentification, i found an apache module, auth_user_dir, that looked fine to me on http://www.genos.org :

You can create private user folders using the WebDAV protocol. Users will have only permissions to access to their own directory. Without this module, a htaccess file must be created inside every user folder. This is completely unmanageable when the number of users is big.

We can build a file server accessible from Windows and Linux using the WebDAV protocol and a web server like Apache. Because the protocol is build upon HTTP, the server uses ports TCP 80 (HTTP) and TCP 443 (HTTPS). These ports are commonly open in firewalls without any other special requirement.

The module appears to have been developed in 2004 an  attached tutorial was referring to some patches that no longer exist. So here is explained the way I managed to build this module on debian in 2010. I also found some tricks to make the mysql authentication work. This is a little crap but it worked !