I plan to implement a common authentication and authorization system for several linux applications. Some examples to use that AA system is: xl2tpd, pptpd, openvpn, squid and some custom made web applications. Do you know any ready system for undertaking such a mission? I mean a system, with user and role management including. That system may have some authenticator system binary that results in grant or reject, and other tools may be configured for using thgat binary for checking authentication and authorization.