mod_http_oauth2: Reject loopback URIs as client_uri This really should be a proper website with info, https://localhost is not good enough. Ideally we'd validate that it's got proper DNS and is actually reachable, but triggering HTTP or even DNS lookups seems like it would carry abuse potential that would best to avoid.

author: Kim Alvefur <zash@zash.se>
date: Tue, 02 May 2023 16:20:55 +0200
parent: 5400:71766a4a7322
child: 5402:fbf3ede7541b
--- a/mod_http_oauth2/mod_http_oauth2.lua	Tue May 02 16:14:22 2023 +0200
+++ b/mod_http_oauth2/mod_http_oauth2.lua	Tue May 02 16:20:55 2023 +0200
@@ -754,7 +754,7 @@
 	end
 
 	local client_uri = url.parse(client_metadata.client_uri);
-	if not client_uri or client_uri.scheme ~= "https" then
+	if not client_uri or client_uri.scheme ~= "https" or loopbacks:contains(client_uri.host) then
 		return nil, oauth_error("invalid_request", "Missing, invalid or insecure client_uri");
 	end