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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!

local base64_encode = require"util.encodings".base64.encode;
local random_bytes = require"util.random".bytes;

local b64url = { ["+"] = "-", ["/"] = "_", ["="] = "" };
local function random_resource()
	return base64_encode(random_bytes(8)):gsub("[+/=]", b64url);
end

module:hook("pre-resource-bind", function (event)
	event.resource = random_resource();
end);