mod_tokenauth: Switch to new token format (invalidates existing tokens!)

The new format has the following properties:

- 5 bytes longer than the previous format
- The token now has separate 'id' and 'secret' parts - the token itself is no
  longer stored in the DB, and the secret part is hashed
- The only variable length field (JID) has been moved to the end
- The 'secret-token:' prefix (RFC 8959) is now included

Compatibility with the old token format was not maintained, and all previously
issued tokens are invalid after this commit (they will be removed from the DB
if used).

plugins/mod_tokenauth.lua

@@ -1,6 +1,8 @@
+local base64 = require "util.encodings".base64;
+local hashes = require "util.hashes";
 local id = require "util.id";
 local jid = require "util.jid";
-local base64 = require "util.encodings".base64;
+local random = require "util.random";
 local usermanager = require "core.usermanager";
 local generate_identifier = require "util.id".short;
 
@@ -29,7 +31,11 @@ function create_jid_token(actor_jid, token_jid, token_role, token_ttl, token_dat
 		return nil, "bad-request";
 	end
 
+	local token_id = id.short();
+
 	local token_info = {
+		id = token_id;
+
 		owner = actor_jid;
 		created = os.time();
 		expires = token_ttl and (os.time() + token_ttl) or nil;
@@ -41,36 +47,51 @@ function create_jid_token(actor_jid, token_jid, token_role, token_ttl, token_dat
 		data = token_data;
 	};
 
-	local token_id = id.long();
+	local token_secret = random.bytes(18);
-	local token = base64.encode("1;"..jid.join(token_username, token_host)..";"..token_id);
+	local token = "secret-token:"..base64.encode("2;"..token_id..";"..token_secret..";"..jid.join(token_username, token_host));
-	token_store:set(token_username, token_id, token_info);
+	token_store:set(token_username, token_id, {
+		secret_sha256 = hashes.sha256(token_secret, true);
+		token_info = token_info
+	});
 
 	return token, token_info;
 end
 
 local function parse_token(encoded_token)
 	if not encoded_token then return nil; end
-	local token = base64.decode(encoded_token);
+	local encoded_data = encoded_token:match("^secret%-token:(.+)$");
+	if not encoded_data then return nil; end
+	local token = base64.decode(encoded_data);
 	if not token then return nil; end
-	local token_jid, token_id = token:match("^1;([^;]+);(.+)$");
+	local token_id, token_secret, token_jid = token:match("^2;([^;]+);([^;]+);(.+)$");
-	if not token_jid then return nil; end
+	if not token_id then return nil; end
 	local token_user, token_host = jid.split(token_jid);
-	return token_id, token_user, token_host;
+	return token_id, token_user, token_host, token_secret;
 end
 
-local function _get_parsed_token_info(token_id, token_user, token_host)
+local function _get_validated_token_info(token_id, token_user, token_host, token_secret)
 	if token_host ~= module.host then
 		return nil, "invalid-host";
 	end
 
-	local token_info, err = token_store:get(token_user, token_id);
+	local token, err = token_store:get(token_user, token_id);
-	if not token_info then
+	if not token then
 		if err then
 			return nil, "internal-error";
 		end
 		return nil, "not-authorized";
+	elseif not token.secret_sha256 then -- older token format
+		token_store:set(token_user, token_id, nil);
+		return nil, "not-authorized";
 	end
 
+	-- Check provided secret
+	if not hashes.equals(hashes.sha256(token_secret, true), token.secret_sha256) then
+		return nil, "not-authorized";
+	end
+
+	local token_info = token.token_info;
+
 	if token_info.expires and token_info.expires < os.time() then
 		token_store:set(token_user, token_id, nil);
 		return nil, "not-authorized";
@@ -87,12 +108,12 @@ local function _get_parsed_token_info(token_id, token_user, token_host)
 end
 
 function get_token_info(token)
-	local token_id, token_user, token_host = parse_token(token);
+	local token_id, token_user, token_host, token_secret = parse_token(token);
 	if not token_id then
 		module:log("warn", "Failed to verify access token: %s", token_user);
 		return nil, "invalid-token-format";
 	end
-	return _get_parsed_token_info(token_id, token_user, token_host);
+	return _get_validated_token_info(token_id, token_user, token_host, token_secret);
 end
 
 function get_token_session(token, resource)
@@ -102,7 +123,7 @@ function get_token_session(token, resource)
 		return nil, "invalid-token-format";
 	end
 
-	local token_info, err = _get_parsed_token_info(token_id, token_user, token_host);
+	local token_info, err = _get_validated_token_info(token_id, token_user, token_host);
 	if not token_info then return nil, err; end
 
 	return {