#1 IP-based authentication

[Julien Gouesse]

LibreKaraoke needs a very basic authentication mechanism that can be very quickly implemented and that would be suitable in most cases, i.e when the administrator can access the server physically or with remote control (SSH, etc) and when the server has a display server (X11, Wayland, etc, which doesn't imply a physical monitor).

Authentication and authorization must be checked and enforced server-side. The host inside the URL could be used client-side to avoid unnecessarily bloating the user interface, but all role-based features must be protected server-side anyway. Moreover, keeping authentication and authorization separated follows the principle of separation of concerns. As a consequence, the client must ask the server whether the current user is an administrator instead of doing this check locally and the web services on the server that treat role-based features must be protected (see jakarta.annotation.security.RolesAllowed). That way, a malicious client unable to modify the web services on the server couldn't access the features of the administrator.

The authentication layer must authenticate any user accessing through localhost as an administrator. Otherwise, the user remains unauthenticated. Authenticating any user accessing through the local access network as an administrator would allow more machines to be used to access LibreKaraoke as an administrator, but it would defeat the purpose of this RFE that should remain as simple as possible because it would become necessary to implement a whitelist and/or blacklist of IPs to prevent people using the Wifi to be seen as administrators too.