Issue macaroons as opaque auth tokens

This just replaces random bytes with macaroons. The macaroons are not
inspected by the client or server.

In particular, they claim to have an expiry time, but nothing verifies
that they have not expired.

Follow-up commits will actually enforce the expiration, and allow for
token refresh.

See https://bit.ly/matrix-auth for more information

synapse/config/registration.py

@@ -32,9 +32,11 @@ class RegistrationConfig(Config):
             )
 
         self.registration_shared_secret = config.get("registration_shared_secret")
+        self.macaroon_secret_key = config.get("macaroon_secret_key")
 
     def default_config(self, config_dir, server_name):
         registration_shared_secret = random_string_with_symbols(50)
+        macaroon_secret_key = random_string_with_symbols(50)
         return """\
         ## Registration ##
 
@@ -44,6 +46,8 @@ class RegistrationConfig(Config):
         # If set, allows registration by anyone who also has the shared
         # secret, even if registration is otherwise disabled.
         registration_shared_secret: "%(registration_shared_secret)s"
+
+        macaroon_secret_key: "%(macaroon_secret_key)s"
         """ % locals()
 
     def add_arguments(self, parser):

synapse/handlers/register.py

@@ -25,9 +25,9 @@ import synapse.util.stringutils as stringutils
 from synapse.util.async import run_on_reactor
 from synapse.http.client import CaptchaServerHttpClient
 
-import base64
 import bcrypt
 import logging
+import pymacaroons
 import urllib
 
 logger = logging.getLogger(__name__)
@@ -274,11 +274,18 @@ class RegistrationHandler(BaseHandler):
                 )
 
     def generate_token(self, user_id):
-        # urlsafe variant uses _ and - so use . as the separator and replace
-        # all =s with .s so http clients don't quote =s when it is used as
-        # query params.
-        return (base64.urlsafe_b64encode(user_id).replace('=', '.') + '.' +
-                stringutils.random_string(18))
+        macaroon = pymacaroons.Macaroon(
+            location = self.hs.config.server_name,
+            identifier = "key",
+            key = self.hs.config.macaroon_secret_key)
+        macaroon.add_first_party_caveat("gen = 1")
+        macaroon.add_first_party_caveat("user_id = %s" % user_id)
+        macaroon.add_first_party_caveat("type = access")
+        now = self.hs.get_clock().time()
+        expiry = now + 60 * 60
+        macaroon.add_first_party_caveat("time < %s" % expiry)
+
+        return macaroon.serialize()
 
     def _generate_user_id(self):
         return "-" + stringutils.random_string(18)

synapse/python_dependencies.py

@@ -33,6 +33,7 @@ REQUIREMENTS = {
     "ujson": ["ujson"],
     "blist": ["blist"],
     "pysaml2": ["saml2"],
+    "pymacaroons": ["pymacaroons"],
 }
 CONDITIONAL_REQUIREMENTS = {
     "web_client": {

tests/handlers/test_register.py

@@ -0,0 +1,70 @@
+# -*- coding: utf-8 -*-
+# Copyright 2015 OpenMarket Ltd
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import pymacaroons
+
+from mock import Mock, NonCallableMock
+from synapse.handlers.register import RegistrationHandler
+from tests import unittest
+from tests.utils import setup_test_homeserver
+from twisted.internet import defer
+
+
+class RegisterHandlers(object):
+    def __init__(self, hs):
+        self.registration_handler = RegistrationHandler(hs)
+
+
+class RegisterTestCase(unittest.TestCase):
+    @defer.inlineCallbacks
+    def setUp(self):
+        self.hs = yield setup_test_homeserver(handlers=None)
+        self.hs.handlers = RegisterHandlers(self.hs)
+
+    def test_token_is_a_macaroon(self):
+        self.hs.config.macaroon_secret_key = "this key is a huge secret"
+
+        token = self.hs.handlers.registration_handler.generate_token("some_user")
+        # Check that we can parse the thing with pymacaroons
+        macaroon = pymacaroons.Macaroon.deserialize(token)
+        # The most basic of sanity checks
+        if "some_user" not in macaroon.inspect():
+            self.fail("some_user was not in %s" % macaroon.inspect())
+
+    def test_macaroon_caveats(self):
+        self.hs.config.macaroon_secret_key = "this key is a massive secret"
+        self.hs.clock.now = 5000
+
+        token = self.hs.handlers.registration_handler.generate_token("a_user")
+        macaroon = pymacaroons.Macaroon.deserialize(token)
+
+        def verify_gen(caveat):
+            return caveat == "gen = 1"
+
+        def verify_user(caveat):
+            return caveat == "user_id = a_user"
+
+        def verify_type(caveat):
+            return caveat == "type = access"
+
+        def verify_expiry(caveat):
+            return caveat == "time < 8600"
+
+        v = pymacaroons.Verifier()
+        v.satisfy_general(verify_gen)
+        v.satisfy_general(verify_user)
+        v.satisfy_general(verify_type)
+        v.satisfy_general(verify_expiry)
+        v.verify(macaroon, self.hs.config.macaroon_secret_key)

tests/utils.py

@@ -44,6 +44,8 @@ def setup_test_homeserver(name="test", datastore=None, config=None, **kargs):
         config.signing_key = [MockKey()]
         config.event_cache_size = 1
         config.disable_registration = False
+        config.macaroon_secret_key = "not even a little secret"
+        config.server_name = "server.under.test"
 
     if "clock" not in kargs:
         kargs["clock"] = MockClock()