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.

7 files changed, 257 insertions, 36 deletions

diff --git a/synapse/api/auth.py b/synapse/api/auth.py
index 65ee1452ce..f8ea1e2c69 100644
--- a/synapse/api/auth.py
+++ b/synapse/api/auth.py
@@ -23,6 +23,7 @@ from synapse.util.logutils import log_function
 from synapse.types import UserID
 
 import logging
+import pymacaroons
 
 logger = logging.getLogger(__name__)
 
@@ -40,6 +41,12 @@ class Auth(object):
         self.store = hs.get_datastore()
         self.state = hs.get_state_handler()
         self.TOKEN_NOT_FOUND_HTTP_STATUS = 401
+        self._KNOWN_CAVEAT_PREFIXES = set([
+            "gen = ",
+            "type = ",
+            "time < ",
+            "user_id = ",
+        ])
 
     def check(self, event, auth_events):
         """ Checks if this event is correctly authed.
@@ -359,8 +366,8 @@ class Auth(object):
             except KeyError:
                 pass  # normal users won't have the user_id query parameter set.
 
-            user_info = yield self.get_user_by_access_token(access_token)
-            user = user_info["user"]
+            user_info = yield self._get_user_by_access_token(access_token)
+            user_id = user_info["user_id"]
             token_id = user_info["token_id"]
 
             ip_addr = self.hs.get_ip_from_request(request)
@@ -368,17 +375,17 @@ class Auth(object):
                 "User-Agent",
                 default=[""]
             )[0]
-            if user and access_token and ip_addr:
+            if user_id and access_token and ip_addr:
                 self.store.insert_client_ip(
-                    user=user,
+                    user=user_id,
                     access_token=access_token,
                     ip=ip_addr,
                     user_agent=user_agent
                 )
 
-            request.authenticated_entity = user.to_string()
+            request.authenticated_entity = user_id.to_string()
 
-            defer.returnValue((user, token_id,))
+            defer.returnValue((user_id, token_id,))
         except KeyError:
             raise AuthError(
                 self.TOKEN_NOT_FOUND_HTTP_STATUS, "Missing access token.",
@@ -386,7 +393,7 @@ class Auth(object):
             )
 
     @defer.inlineCallbacks
-    def get_user_by_access_token(self, token):
+    def _get_user_by_access_token(self, token):
         """ Get a registered user's ID.
 
         Args:
@@ -396,6 +403,86 @@ class Auth(object):
         Raises:
             AuthError if no user by that token exists or the token is invalid.
         """
+        try:
+            ret = yield self._get_user_from_macaroon(token)
+        except AuthError:
+            # TODO(daniel): Remove this fallback when all existing access tokens
+            # have been re-issued as macaroons.
+            ret = yield self._look_up_user_by_access_token(token)
+        defer.returnValue(ret)
+
+    @defer.inlineCallbacks
+    def _get_user_from_macaroon(self, macaroon_str):
+        try:
+            macaroon = pymacaroons.Macaroon.deserialize(macaroon_str)
+            self._validate_macaroon(macaroon)
+
+            user_prefix = "user_id = "
+            for caveat in macaroon.caveats:
+                if caveat.caveat_id.startswith(user_prefix):
+                    user_id = UserID.from_string(caveat.caveat_id[len(user_prefix):])
+                    # This codepath exists so that we can actually return a
+                    # token ID, because we use token IDs in place of device
+                    # identifiers throughout the codebase.
+                    # TODO(daniel): Remove this fallback when device IDs are
+                    # properly implemented.
+                    ret = yield self._look_up_user_by_access_token(macaroon_str)
+                    if ret["user_id"] != user_id:
+                        logger.error(
+                            "Macaroon user (%s) != DB user (%s)",
+                            user_id,
+                            ret["user_id"]
+                        )
+                        raise AuthError(
+                            self.TOKEN_NOT_FOUND_HTTP_STATUS,
+                            "User mismatch in macaroon",
+                            errcode=Codes.UNKNOWN_TOKEN
+                        )
+                    defer.returnValue(ret)
+            raise AuthError(
+                self.TOKEN_NOT_FOUND_HTTP_STATUS, "No user caveat in macaroon",
+                errcode=Codes.UNKNOWN_TOKEN
+            )
+        except (pymacaroons.exceptions.MacaroonException, TypeError, ValueError):
+            raise AuthError(
+                self.TOKEN_NOT_FOUND_HTTP_STATUS, "Invalid macaroon passed.",
+                errcode=Codes.UNKNOWN_TOKEN
+            )
+
+    def _validate_macaroon(self, macaroon):
+        v = pymacaroons.Verifier()
+        v.satisfy_exact("gen = 1")
+        v.satisfy_exact("type = access")
+        v.satisfy_general(lambda c: c.startswith("user_id = "))
+        v.satisfy_general(self._verify_expiry)
+        v.verify(macaroon, self.hs.config.macaroon_secret_key)
+
+        v = pymacaroons.Verifier()
+        v.satisfy_general(self._verify_recognizes_caveats)
+        v.verify(macaroon, self.hs.config.macaroon_secret_key)
+
+    def _verify_expiry(self, caveat):
+        prefix = "time < "
+        if not caveat.startswith(prefix):
+            return False
+        # TODO(daniel): Enable expiry check when clients actually know how to
+        # refresh tokens. (And remember to enable the tests)
+        return True
+        expiry = int(caveat[len(prefix):])
+        now = self.hs.get_clock().time_msec()
+        return now < expiry
+
+    def _verify_recognizes_caveats(self, caveat):
+        first_space = caveat.find(" ")
+        if first_space < 0:
+            return False
+        second_space = caveat.find(" ", first_space + 1)
+        if second_space < 0:
+            return False
+        return caveat[:second_space + 1] in self._KNOWN_CAVEAT_PREFIXES
+
+    @defer.inlineCallbacks
+    def _look_up_user_by_access_token(self, token):
         ret = yield self.store.get_user_by_access_token(token)
         if not ret:
             raise AuthError(
@@ -403,10 +490,9 @@ class Auth(object):
                 errcode=Codes.UNKNOWN_TOKEN
             )
         user_info = {
-            "user": UserID.from_string(ret.get("name")),
+            "user_id": UserID.from_string(ret.get("name")),
             "token_id": ret.get("token_id", None),
         }
-
         defer.returnValue(user_info)
 
     @defer.inlineCallbacks
diff --git a/tests/api/test_auth.py b/tests/api/test_auth.py
index 22fc804331..1ba85d6f83 100644
--- a/tests/api/test_auth.py
+++ b/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)
diff --git a/tests/rest/client/v1/test_presence.py b/tests/rest/client/v1/test_presence.py
index 91547bdd06..d8d1416f59 100644
--- a/tests/rest/client/v1/test_presence.py
+++ b/tests/rest/client/v1/test_presence.py
@@ -72,11 +72,11 @@ class PresenceStateTestCase(unittest.TestCase):
 
         def _get_user_by_access_token(token=None):
             return {
-                "user": UserID.from_string(myid),
+                "user_id": UserID.from_string(myid),
                 "token_id": 1,
             }
 
-        hs.get_v1auth().get_user_by_access_token = _get_user_by_access_token
+        hs.get_v1auth()._get_user_by_access_token = _get_user_by_access_token
 
         room_member_handler = hs.handlers.room_member_handler = Mock(
             spec=[
@@ -159,7 +159,7 @@ class PresenceListTestCase(unittest.TestCase):
 
         def _get_user_by_access_token(token=None):
             return {
-                "user": UserID.from_string(myid),
+                "user_id": UserID.from_string(myid),
                 "token_id": 1,
             }
 
@@ -169,7 +169,7 @@ class PresenceListTestCase(unittest.TestCase):
             ]
         )
 
-        hs.get_v1auth().get_user_by_access_token = _get_user_by_access_token
+        hs.get_v1auth()._get_user_by_access_token = _get_user_by_access_token
 
         presence.register_servlets(hs, self.mock_resource)
 
diff --git a/tests/rest/client/v1/test_rooms.py b/tests/rest/client/v1/test_rooms.py
index 34ab47d02e..be1d52f720 100644
--- a/tests/rest/client/v1/test_rooms.py
+++ b/tests/rest/client/v1/test_rooms.py
@@ -56,10 +56,10 @@ class RoomPermissionsTestCase(RestTestCase):
 
         def _get_user_by_access_token(token=None):
             return {
-                "user": UserID.from_string(self.auth_user_id),
+                "user_id": UserID.from_string(self.auth_user_id),
                 "token_id": 1,
             }
-        hs.get_v1auth().get_user_by_access_token = _get_user_by_access_token
+        hs.get_v1auth()._get_user_by_access_token = _get_user_by_access_token
 
         def _insert_client_ip(*args, **kwargs):
             return defer.succeed(None)
@@ -441,10 +441,10 @@ class RoomsMemberListTestCase(RestTestCase):
 
         def _get_user_by_access_token(token=None):
             return {
-                "user": UserID.from_string(self.auth_user_id),
+                "user_id": UserID.from_string(self.auth_user_id),
                 "token_id": 1,
             }
-        hs.get_v1auth().get_user_by_access_token = _get_user_by_access_token
+        hs.get_v1auth()._get_user_by_access_token = _get_user_by_access_token
 
         def _insert_client_ip(*args, **kwargs):
             return defer.succeed(None)
@@ -519,10 +519,10 @@ class RoomsCreateTestCase(RestTestCase):
 
         def _get_user_by_access_token(token=None):
             return {
-                "user": UserID.from_string(self.auth_user_id),
+                "user_id": UserID.from_string(self.auth_user_id),
                 "token_id": 1,
             }
-        hs.get_v1auth().get_user_by_access_token = _get_user_by_access_token
+        hs.get_v1auth()._get_user_by_access_token = _get_user_by_access_token
 
         def _insert_client_ip(*args, **kwargs):
             return defer.succeed(None)
@@ -610,11 +610,11 @@ class RoomTopicTestCase(RestTestCase):
 
         def _get_user_by_access_token(token=None):
             return {
-                "user": UserID.from_string(self.auth_user_id),
+                "user_id": UserID.from_string(self.auth_user_id),
                 "token_id": 1,
             }
 
-        hs.get_v1auth().get_user_by_access_token = _get_user_by_access_token
+        hs.get_v1auth()._get_user_by_access_token = _get_user_by_access_token
 
         def _insert_client_ip(*args, **kwargs):
             return defer.succeed(None)
@@ -715,10 +715,10 @@ class RoomMemberStateTestCase(RestTestCase):
 
         def _get_user_by_access_token(token=None):
             return {
-                "user": UserID.from_string(self.auth_user_id),
+                "user_id": UserID.from_string(self.auth_user_id),
                 "token_id": 1,
             }
-        hs.get_v1auth().get_user_by_access_token = _get_user_by_access_token
+        hs.get_v1auth()._get_user_by_access_token = _get_user_by_access_token
 
         def _insert_client_ip(*args, **kwargs):
             return defer.succeed(None)
@@ -840,10 +840,10 @@ class RoomMessagesTestCase(RestTestCase):
 
         def _get_user_by_access_token(token=None):
             return {
-                "user": UserID.from_string(self.auth_user_id),
+                "user_id": UserID.from_string(self.auth_user_id),
                 "token_id": 1,
             }
-        hs.get_v1auth().get_user_by_access_token = _get_user_by_access_token
+        hs.get_v1auth()._get_user_by_access_token = _get_user_by_access_token
 
         def _insert_client_ip(*args, **kwargs):
             return defer.succeed(None)
@@ -935,10 +935,10 @@ class RoomInitialSyncTestCase(RestTestCase):
 
         def _get_user_by_access_token(token=None):
             return {
-                "user": UserID.from_string(self.auth_user_id),
+                "user_id": UserID.from_string(self.auth_user_id),
                 "token_id": 1,
             }
-        hs.get_v1auth().get_user_by_access_token = _get_user_by_access_token
+        hs.get_v1auth()._get_user_by_access_token = _get_user_by_access_token
 
         def _insert_client_ip(*args, **kwargs):
             return defer.succeed(None)
diff --git a/tests/rest/client/v1/test_typing.py b/tests/rest/client/v1/test_typing.py
index 1c4519406d..da6fc975f7 100644
--- a/tests/rest/client/v1/test_typing.py
+++ b/tests/rest/client/v1/test_typing.py
@@ -63,11 +63,11 @@ class RoomTypingTestCase(RestTestCase):
 
         def _get_user_by_access_token(token=None):
             return {
-                "user": UserID.from_string(self.auth_user_id),
+                "user_id": UserID.from_string(self.auth_user_id),
                 "token_id": 1,
             }
 
-        hs.get_v1auth().get_user_by_access_token = _get_user_by_access_token
+        hs.get_v1auth()._get_user_by_access_token = _get_user_by_access_token
 
         def _insert_client_ip(*args, **kwargs):
             return defer.succeed(None)
diff --git a/tests/rest/client/v1/utils.py b/tests/rest/client/v1/utils.py
index c472d53043..85096a0326 100644
--- a/tests/rest/client/v1/utils.py
+++ b/tests/rest/client/v1/utils.py
@@ -37,9 +37,6 @@ class RestTestCase(unittest.TestCase):
         self.mock_resource = None
         self.auth_user_id = None
 
-    def mock_get_user_by_access_token(self, token=None):
-        return self.auth_user_id
-
     @defer.inlineCallbacks
     def create_room_as(self, room_creator, is_public=True, tok=None):
         temp_id = self.auth_user_id
diff --git a/tests/rest/client/v2_alpha/__init__.py b/tests/rest/client/v2_alpha/__init__.py
index ef972a53aa..7d0f77a3ee 100644
--- a/tests/rest/client/v2_alpha/__init__.py
+++ b/tests/rest/client/v2_alpha/__init__.py
@@ -45,10 +45,10 @@ class V2AlphaRestTestCase(unittest.TestCase):
 
         def _get_user_by_access_token(token=None):
             return {
-                "user": UserID.from_string(self.USER_ID),
+                "user_id": UserID.from_string(self.USER_ID),
                 "token_id": 1,
             }
-        hs.get_auth().get_user_by_access_token = _get_user_by_access_token
+        hs.get_auth()._get_user_by_access_token = _get_user_by_access_token
 
         for r in self.TO_REGISTER:
             r.register_servlets(hs, self.mock_resource)