Attempt to validate macaroons

A couple of weird caveats:
 * If we can't validate your macaroon, we fall back to checking that
   your access token is in the DB, and ignoring the failure
 * Even if we can validate your macaroon, we still have to hit the DB to
   get the access token ID, which we pretend is a device ID all over the
   codebase.

This mostly adds the interesting code, and points out the two pieces we
need to delete (and necessary conditions) in order to fix the above
caveats.

tests/api/test_auth.py

@@ -14,22 +14,27 @@
 # limitations under the License.
 from tests import unittest
 from twisted.internet import defer
+from twisted.trial.unittest import FailTest
 
 from mock import Mock
 
 from synapse.api.auth import Auth
 from synapse.api.errors import AuthError
+from synapse.types import UserID
+from tests.utils import setup_test_homeserver
+
+import pymacaroons
 
 
 class AuthTestCase(unittest.TestCase):
 
+    @defer.inlineCallbacks
     def setUp(self):
         self.state_handler = Mock()
         self.store = Mock()
 
-        self.hs = Mock()
+        self.hs = yield setup_test_homeserver(handlers=None)
         self.hs.get_datastore = Mock(return_value=self.store)
-        self.hs.get_state_handler = Mock(return_value=self.state_handler)
         self.auth = Auth(self.hs)
 
         self.test_user = "@foo:bar"
@@ -133,3 +138,136 @@ class AuthTestCase(unittest.TestCase):
         request.requestHeaders.getRawHeaders = Mock(return_value=[""])
         d = self.auth.get_user_by_req(request)
         self.failureResultOf(d, AuthError)
+
+    @defer.inlineCallbacks
+    def test_get_user_from_macaroon(self):
+        # TODO(danielwh): Remove this mock when we remove the
+        # get_user_by_access_token fallback.
+        self.store.get_user_by_access_token = Mock(
+            return_value={"name": "@baldrick:matrix.org"}
+        )
+
+        user = "@baldrick:matrix.org"
+        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("type = access")
+        macaroon.add_first_party_caveat("user_id = %s" % (user,))
+        user_info = yield self.auth._get_user_from_macaroon(macaroon.serialize())
+        user_id = user_info["user_id"]
+        self.assertEqual(UserID.from_string(user), user_id)
+
+    @defer.inlineCallbacks
+    def test_get_user_from_macaroon_user_db_mismatch(self):
+        self.store.get_user_by_access_token = Mock(
+            return_value={"name": "@percy:matrix.org"}
+        )
+
+        user = "@baldrick:matrix.org"
+        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("type = access")
+        macaroon.add_first_party_caveat("user_id = %s" % (user,))
+        with self.assertRaises(AuthError) as cm:
+            yield self.auth._get_user_from_macaroon(macaroon.serialize())
+        self.assertEqual(401, cm.exception.code)
+        self.assertIn("User mismatch", cm.exception.msg)
+
+    @defer.inlineCallbacks
+    def test_get_user_from_macaroon_missing_caveat(self):
+        # TODO(danielwh): Remove this mock when we remove the
+        # get_user_by_access_token fallback.
+        self.store.get_user_by_access_token = Mock(
+            return_value={"name": "@baldrick:matrix.org"}
+        )
+
+        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("type = access")
+
+        with self.assertRaises(AuthError) as cm:
+            yield self.auth._get_user_from_macaroon(macaroon.serialize())
+        self.assertEqual(401, cm.exception.code)
+        self.assertIn("No user caveat", cm.exception.msg)
+
+    @defer.inlineCallbacks
+    def test_get_user_from_macaroon_wrong_key(self):
+        # TODO(danielwh): Remove this mock when we remove the
+        # get_user_by_access_token fallback.
+        self.store.get_user_by_access_token = Mock(
+            return_value={"name": "@baldrick:matrix.org"}
+        )
+
+        user = "@baldrick:matrix.org"
+        macaroon = pymacaroons.Macaroon(
+            location=self.hs.config.server_name,
+            identifier="key",
+            key=self.hs.config.macaroon_secret_key + "wrong")
+        macaroon.add_first_party_caveat("gen = 1")
+        macaroon.add_first_party_caveat("type = access")
+        macaroon.add_first_party_caveat("user_id = %s" % (user,))
+
+        with self.assertRaises(AuthError) as cm:
+            yield self.auth._get_user_from_macaroon(macaroon.serialize())
+        self.assertEqual(401, cm.exception.code)
+        self.assertIn("Invalid macaroon", cm.exception.msg)
+
+    @defer.inlineCallbacks
+    def test_get_user_from_macaroon_unknown_caveat(self):
+        # TODO(danielwh): Remove this mock when we remove the
+        # get_user_by_access_token fallback.
+        self.store.get_user_by_access_token = Mock(
+            return_value={"name": "@baldrick:matrix.org"}
+        )
+
+        user = "@baldrick:matrix.org"
+        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("type = access")
+        macaroon.add_first_party_caveat("user_id = %s" % (user,))
+        macaroon.add_first_party_caveat("cunning > fox")
+
+        with self.assertRaises(AuthError) as cm:
+            yield self.auth._get_user_from_macaroon(macaroon.serialize())
+        self.assertEqual(401, cm.exception.code)
+        self.assertIn("Invalid macaroon", cm.exception.msg)
+
+    @defer.inlineCallbacks
+    def test_get_user_from_macaroon_expired(self):
+        # TODO(danielwh): Remove this mock when we remove the
+        # get_user_by_access_token fallback.
+        self.store.get_user_by_access_token = Mock(
+            return_value={"name": "@baldrick:matrix.org"}
+        )
+
+        self.todo = (FailTest, "Token expiry isn't currently enabled",)
+        self.store.get_user_by_access_token = Mock(
+            return_value={"name": "@baldrick:matrix.org"}
+        )
+
+        user = "@baldrick:matrix.org"
+        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("type = access")
+        macaroon.add_first_party_caveat("user_id = %s" % (user,))
+        macaroon.add_first_party_caveat("time < 1") # ms
+
+        self.hs.clock.now = 5000 # seconds
+        with self.assertRaises(AuthError) as cm:
+            yield self.auth._get_user_from_macaroon(macaroon.serialize())
+        self.assertEqual(401, cm.exception.code)
+        self.assertIn("Invalid macaroon", cm.exception.msg)