Authentication of HTTP Requests is generally a two-step process: First the credentials must be extracted from the request and second the credentials must be validated. In the case of Sling this means acquiring a JCR Session.
HttpServletRequestCredentials and Workspace name)AuthenticationHandler servicesCredentials and Workspace nameSessionLoginModules; Sling's Embedded Jackrabbit Repository bundle provides extensibility with LoginModulePlugin services.Currently the credentials are always verified by trying to login to the JCR repository. Once an ResourceResolverFactory API has been added, the process of validating the credentials and logging in is actualy replaced by a process of requesting a ResourceResolver from the ResourceResolverFactory. Of course, the JCR Repository will still be the main underlying repository and as such be used to validate the credentials and get a JCR Session.