Record the SSO Auth Provider in the login token (#9510)

This great big stack of commits is a a whole load of hoop-jumping to make it easier to store additional values in login tokens, and then to actually store the SSO Identity Provider in the login token. (Making use of that data will follow in a subsequent PR.)

Author: richvdh

changelog.d/9510.feature

@@ -0,0 +1 @@
+Add prometheus metrics for number of users successfully registering and logging in.

mypy.ini

@@ -69,6 +69,7 @@ files =
   synapse/util/async_helpers.py,
   synapse/util/caches,
   synapse/util/metrics.py,
+  synapse/util/macaroons.py,
   synapse/util/stringutils.py,
   tests/replication,
   tests/test_utils,

synapse/api/auth.py

@@ -39,6 +39,7 @@
 from synapse.storage.databases.main.registration import TokenLookupResult
 from synapse.types import StateMap, UserID
 from synapse.util.caches.lrucache import LruCache
+from synapse.util.macaroons import get_value_from_macaroon, satisfy_expiry
 from synapse.util.metrics import Measure
 
 logger = logging.getLogger(__name__)
@@ -408,43 +409,27 @@ def _parse_and_validate_macaroon(self, token, rights="access"):
             raise _InvalidMacaroonException()
 
         try:
-            user_id = self.get_user_id_from_macaroon(macaroon)
+            user_id = get_value_from_macaroon(macaroon, "user_id")
 
             guest = False
             for caveat in macaroon.caveats:
                 if caveat.caveat_id == "guest = true":
                     guest = True
 
             self.validate_macaroon(macaroon, rights, user_id=user_id)
-        except (pymacaroons.exceptions.MacaroonException, TypeError, ValueError):
+        except (
+            pymacaroons.exceptions.MacaroonException,
+            KeyError,
+            TypeError,
+            ValueError,
+        ):
             raise InvalidClientTokenError("Invalid macaroon passed.")
 
         if rights == "access":
             self.token_cache[token] = (user_id, guest)
 
         return user_id, guest
 
-    def get_user_id_from_macaroon(self, macaroon):
-        """Retrieve the user_id given by the caveats on the macaroon.
-
-        Does *not* validate the macaroon.
-
-        Args:
-            macaroon (pymacaroons.Macaroon): The macaroon to validate
-
-        Returns:
-            (str) user id
-
-        Raises:
-            InvalidClientCredentialsError if there is no user_id caveat in the
-                macaroon
-        """
-        user_prefix = "user_id = "
-        for caveat in macaroon.caveats:
-            if caveat.caveat_id.startswith(user_prefix):
-                return caveat.caveat_id[len(user_prefix) :]
-        raise InvalidClientTokenError("No user caveat in macaroon")
-
     def validate_macaroon(self, macaroon, type_string, user_id):
         """
         validate that a Macaroon is understood by and was signed by this server.
@@ -465,21 +450,13 @@ def validate_macaroon(self, macaroon, type_string, user_id):
         v.satisfy_exact("type = " + type_string)
         v.satisfy_exact("user_id = %s" % user_id)
         v.satisfy_exact("guest = true")
-        v.satisfy_general(self._verify_expiry)
+        satisfy_expiry(v, self.clock.time_msec)
 
         # access_tokens include a nonce for uniqueness: any value is acceptable
         v.satisfy_general(lambda c: c.startswith("nonce = "))
 
         v.verify(macaroon, self._macaroon_secret_key)
 
-    def _verify_expiry(self, caveat):
-        prefix = "time < "
-        if not caveat.startswith(prefix):
-            return False
-        expiry = int(caveat[len(prefix) :])
-        now = self.hs.get_clock().time_msec()
-        return now < expiry
-
     def get_appservice_by_req(self, request: SynapseRequest) -> ApplicationService:
         token = self.get_access_token_from_request(request)
         service = self.store.get_app_service_by_token(token)

synapse/handlers/auth.py

@@ -65,6 +65,7 @@
 from synapse.types import JsonDict, Requester, UserID
 from synapse.util import stringutils as stringutils
 from synapse.util.async_helpers import maybe_awaitable
+from synapse.util.macaroons import get_value_from_macaroon, satisfy_expiry
 from synapse.util.msisdn import phone_number_to_msisdn
 from synapse.util.threepids import canonicalise_email
 
@@ -170,6 +171,16 @@ class SsoLoginExtraAttributes:
     extra_attributes = attr.ib(type=JsonDict)
 
 
+@attr.s(slots=True, frozen=True)
+class LoginTokenAttributes:
+    """Data we store in a short-term login token"""
+
+    user_id = attr.ib(type=str)
+
+    # the SSO Identity Provider that the user authenticated with, to get this token
+    auth_provider_id = attr.ib(type=str)
+
+
 class AuthHandler(BaseHandler):
     SESSION_EXPIRE_MS = 48 * 60 * 60 * 1000
 
@@ -1164,18 +1175,16 @@ async def _check_local_password(self, user_id: str, password: str) -> Optional[s
             return None
         return user_id
 
-    async def validate_short_term_login_token_and_get_user_id(self, login_token: str):
-        auth_api = self.hs.get_auth()
-        user_id = None
+    async def validate_short_term_login_token(
+        self, login_token: str
+    ) -> LoginTokenAttributes:
         try:
-            macaroon = pymacaroons.Macaroon.deserialize(login_token)
-            user_id = auth_api.get_user_id_from_macaroon(macaroon)
-            auth_api.validate_macaroon(macaroon, "login", user_id)
+            res = self.macaroon_gen.verify_short_term_login_token(login_token)
         except Exception:
             raise AuthError(403, "Invalid token", errcode=Codes.FORBIDDEN)
 
-        await self.auth.check_auth_blocking(user_id)
-        return user_id
+        await self.auth.check_auth_blocking(res.user_id)
+        return res
 
     async def delete_access_token(self, access_token: str):
         """Invalidate a single access token
@@ -1397,6 +1406,7 @@ async def start_sso_ui_auth(self, request: SynapseRequest, session_id: str) -> s
     async def complete_sso_login(
         self,
         registered_user_id: str,
+        auth_provider_id: str,
         request: Request,
         client_redirect_url: str,
         extra_attributes: Optional[JsonDict] = None,
@@ -1406,6 +1416,9 @@ async def complete_sso_login(
 
         Args:
             registered_user_id: The registered user ID to complete SSO login for.
+            auth_provider_id: The id of the SSO Identity provider that was used for
+                login. This will be stored in the login token for future tracking in
+                prometheus metrics.
             request: The request to complete.
             client_redirect_url: The URL to which to redirect the user at the end of the
                 process.
@@ -1427,6 +1440,7 @@ async def complete_sso_login(
 
         self._complete_sso_login(
             registered_user_id,
+            auth_provider_id,
             request,
             client_redirect_url,
             extra_attributes,
@@ -1437,6 +1451,7 @@ async def complete_sso_login(
     def _complete_sso_login(
         self,
         registered_user_id: str,
+        auth_provider_id: str,
         request: Request,
         client_redirect_url: str,
         extra_attributes: Optional[JsonDict] = None,
@@ -1463,7 +1478,7 @@ def _complete_sso_login(
 
         # Create a login token
         login_token = self.macaroon_gen.generate_short_term_login_token(
-            registered_user_id
+            registered_user_id, auth_provider_id=auth_provider_id
         )
 
         # Append the login token to the original redirect URL (i.e. with its query
@@ -1569,15 +1584,48 @@ def generate_access_token(
         return macaroon.serialize()
 
     def generate_short_term_login_token(
-        self, user_id: str, duration_in_ms: int = (2 * 60 * 1000)
+        self,
+        user_id: str,
+        auth_provider_id: str,
+        duration_in_ms: int = (2 * 60 * 1000),
     ) -> str:
         macaroon = self._generate_base_macaroon(user_id)
         macaroon.add_first_party_caveat("type = login")
         now = self.hs.get_clock().time_msec()
         expiry = now + duration_in_ms
         macaroon.add_first_party_caveat("time < %d" % (expiry,))
+        macaroon.add_first_party_caveat("auth_provider_id = %s" % (auth_provider_id,))
         return macaroon.serialize()
 
+    def verify_short_term_login_token(self, token: str) -> LoginTokenAttributes:
+        """Verify a short-term-login macaroon
+
+        Checks that the given token is a valid, unexpired short-term-login token
+        minted by this server.
+
+        Args:
+            token: the login token to verify
+
+        Returns:
+            the user_id that this token is valid for
+
+        Raises:
+            MacaroonVerificationFailedException if the verification failed
+        """
+        macaroon = pymacaroons.Macaroon.deserialize(token)
+        user_id = get_value_from_macaroon(macaroon, "user_id")
+        auth_provider_id = get_value_from_macaroon(macaroon, "auth_provider_id")
+
+        v = pymacaroons.Verifier()
+        v.satisfy_exact("gen = 1")
+        v.satisfy_exact("type = login")
+        v.satisfy_general(lambda c: c.startswith("user_id = "))
+        v.satisfy_general(lambda c: c.startswith("auth_provider_id = "))
+        satisfy_expiry(v, self.hs.get_clock().time_msec)
+        v.verify(macaroon, self.hs.config.key.macaroon_secret_key)
+
+        return LoginTokenAttributes(user_id=user_id, auth_provider_id=auth_provider_id)
+
     def generate_delete_pusher_token(self, user_id: str) -> str:
         macaroon = self._generate_base_macaroon(user_id)
         macaroon.add_first_party_caveat("type = delete_pusher")

synapse/handlers/oidc_handler.py

@@ -42,6 +42,7 @@
 from synapse.types import JsonDict, UserID, map_username_to_mxid_localpart
 from synapse.util import json_decoder
 from synapse.util.caches.cached_call import RetryOnExceptionCachedCall
+from synapse.util.macaroons import get_value_from_macaroon, satisfy_expiry
 
 if TYPE_CHECKING:
     from synapse.server import HomeServer
@@ -211,7 +212,7 @@ async def handle_oidc_callback(self, request: SynapseRequest) -> None:
             session_data = self._token_generator.verify_oidc_session_token(
                 session, state
             )
-        except (MacaroonDeserializationException, ValueError) as e:
+        except (MacaroonDeserializationException, KeyError) as e:
             logger.exception("Invalid session for OIDC callback")
             self._sso_handler.render_error(request, "invalid_session", str(e))
             return
@@ -745,7 +746,7 @@ async def handle_redirect_request(
                 idp_id=self.idp_id,
                 nonce=nonce,
                 client_redirect_url=client_redirect_url.decode(),
-                ui_auth_session_id=ui_auth_session_id,
+                ui_auth_session_id=ui_auth_session_id or "",
             ),
         )
 
@@ -1020,10 +1021,9 @@ def generate_oidc_session_token(
         macaroon.add_first_party_caveat(
             "client_redirect_url = %s" % (session_data.client_redirect_url,)
         )
-        if session_data.ui_auth_session_id:
-            macaroon.add_first_party_caveat(
-                "ui_auth_session_id = %s" % (session_data.ui_auth_session_id,)
-            )
+        macaroon.add_first_party_caveat(
+            "ui_auth_session_id = %s" % (session_data.ui_auth_session_id,)
+        )
         now = self._clock.time_msec()
         expiry = now + duration_in_ms
         macaroon.add_first_party_caveat("time < %d" % (expiry,))
@@ -1046,7 +1046,7 @@ def verify_oidc_session_token(
             The data extracted from the session cookie
 
         Raises:
-            ValueError if an expected caveat is missing from the macaroon.
+            KeyError if an expected caveat is missing from the macaroon.
         """
         macaroon = pymacaroons.Macaroon.deserialize(session)
 
@@ -1057,60 +1057,23 @@ def verify_oidc_session_token(
         v.satisfy_general(lambda c: c.startswith("nonce = "))
         v.satisfy_general(lambda c: c.startswith("idp_id = "))
         v.satisfy_general(lambda c: c.startswith("client_redirect_url = "))
-        # Sometimes there's a UI auth session ID, it seems to be OK to attempt
-        # to always satisfy this.
         v.satisfy_general(lambda c: c.startswith("ui_auth_session_id = "))
-        v.satisfy_general(self._verify_expiry)
+        satisfy_expiry(v, self._clock.time_msec)
 
         v.verify(macaroon, self._macaroon_secret_key)
 
         # Extract the session data from the token.
-        nonce = self._get_value_from_macaroon(macaroon, "nonce")
-        idp_id = self._get_value_from_macaroon(macaroon, "idp_id")
-        client_redirect_url = self._get_value_from_macaroon(
-            macaroon, "client_redirect_url"
-        )
-        try:
-            ui_auth_session_id = self._get_value_from_macaroon(
-                macaroon, "ui_auth_session_id"
-            )  # type: Optional[str]
-        except ValueError:
-            ui_auth_session_id = None
-
+        nonce = get_value_from_macaroon(macaroon, "nonce")
+        idp_id = get_value_from_macaroon(macaroon, "idp_id")
+        client_redirect_url = get_value_from_macaroon(macaroon, "client_redirect_url")
+        ui_auth_session_id = get_value_from_macaroon(macaroon, "ui_auth_session_id")
         return OidcSessionData(
             nonce=nonce,
             idp_id=idp_id,
             client_redirect_url=client_redirect_url,
             ui_auth_session_id=ui_auth_session_id,
         )
 
-    def _get_value_from_macaroon(self, macaroon: pymacaroons.Macaroon, key: str) -> str:
-        """Extracts a caveat value from a macaroon token.
-
-        Args:
-            macaroon: the token
-            key: the key of the caveat to extract
-
-        Returns:
-            The extracted value
-
-        Raises:
-            ValueError: if the caveat was not in the macaroon
-        """
-        prefix = key + " = "
-        for caveat in macaroon.caveats:
-            if caveat.caveat_id.startswith(prefix):
-                return caveat.caveat_id[len(prefix) :]
-        raise ValueError("No %s caveat in macaroon" % (key,))
-
-    def _verify_expiry(self, caveat: str) -> bool:
-        prefix = "time < "
-        if not caveat.startswith(prefix):
-            return False
-        expiry = int(caveat[len(prefix) :])
-        now = self._clock.time_msec()
-        return now < expiry
-
 
 @attr.s(frozen=True, slots=True)
 class OidcSessionData:
@@ -1125,8 +1088,8 @@ class OidcSessionData:
     # The URL the client gave when it initiated the flow. ("" if this is a UI Auth)
     client_redirect_url = attr.ib(type=str)
 
-    # The session ID of the ongoing UI Auth (None if this is a login)
-    ui_auth_session_id = attr.ib(type=Optional[str], default=None)
+    # The session ID of the ongoing UI Auth ("" if this is a login)
+    ui_auth_session_id = attr.ib(type=str)
 
 
 UserAttributeDict = TypedDict(

synapse/handlers/sso.py

@@ -456,6 +456,7 @@ async def complete_sso_login_request(
 
         await self._auth_handler.complete_sso_login(
             user_id,
+            auth_provider_id,
             request,
             client_redirect_url,
             extra_login_attributes,
@@ -886,6 +887,7 @@ async def register_sso_user(self, request: Request, session_id: str) -> None:
 
         await self._auth_handler.complete_sso_login(
             user_id,
+            session.auth_provider_id,
             request,
             session.client_redirect_url,
             session.extra_login_attributes,