README: document authentication and authorization

README.adoc

@@ -15,6 +15,15 @@ https://blog.ipspace.net/2009/03/generating-layer-2-broadcast-from.html for
 this idea. To prevent misuse of this IP it can be restricted by firewall or
 ACL.
 
+Authentication is based on SAML and handled in `saml.go`. The current setup is
+suited for our local IdP implementation. Change the SAML-attributes for your
+installation if necessary.
+
+Authorization is based on user name (option `Users`) or UNIX group membership
+(option `UnixGroups`; groups on the system where wolass is running).
+Additional methods can be implemented easily. Have a look at `config.go` and
+`isNetworkUserAccesible()` in `main.go`.
+
 
 == Screenshot