Diff

mod_http_oauth2: Advertise the currently supported id_token signing algorithm This field is REQUIRED. The algorithm RS256 MUST be included, but isn't because we don't implement it, as that would require implementing a pile of additional cryptography and JWT stuff. Instead the id_token is signed using the client secret, which allows verification by the client, since it's a shared secret per OpenID Connect Core 1.0 § 10.1 under Symmetric Signatures. OpenID Connect Discovery 1.0 has a lot of REQUIRED and MUST clauses that are not supported here, but that's okay because this is served from the RFC 8414 OAuth 2.0 Authorization Server Metadata .well-known endpoint!

--- a/mod_http_oauth2/mod_http_oauth2.lua	Sun Apr 30 15:20:05 2023 +0200
+++ b/mod_http_oauth2/mod_http_oauth2.lua	Sun Apr 30 16:13:40 2023 +0200
@@ -953,6 +953,7 @@
 
 				-- OpenID
 				userinfo_endpoint = handle_register_request and module:http_url() .. "/userinfo" or nil;
+				id_token_signing_alg_values_supported = { "HS256" };
 			};
 		};
 	};