Save the OIDC session ID (sid) with the device on login (#11482)

As a step towards allowing back-channel logout for OIDC.

Author: sandhose

changelog.d/11482.misc

@@ -0,0 +1 @@
+Save the OpenID Connect session ID on login.

synapse/handlers/auth.py

@@ -39,6 +39,7 @@
 import bcrypt
 import pymacaroons
 import unpaddedbase64
+from pymacaroons.exceptions import MacaroonVerificationFailedException
 
 from twisted.web.server import Request
 
@@ -182,8 +183,11 @@ class LoginTokenAttributes:
 
     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)
+    """The SSO Identity Provider that the user authenticated with, to get this token."""
+
+    auth_provider_session_id = attr.ib(type=Optional[str])
+    """The session ID advertised by the SSO Identity Provider."""
 
 
 class AuthHandler:
@@ -1650,6 +1654,7 @@ async def complete_sso_login(
         client_redirect_url: str,
         extra_attributes: Optional[JsonDict] = None,
         new_user: bool = False,
+        auth_provider_session_id: Optional[str] = None,
     ) -> None:
         """Having figured out a mxid for this user, complete the HTTP request
 
@@ -1665,6 +1670,7 @@ async def complete_sso_login(
                 during successful login. Must be JSON serializable.
             new_user: True if we should use wording appropriate to a user who has just
                 registered.
+            auth_provider_session_id: The session ID from the SSO IdP received during login.
         """
         # If the account has been deactivated, do not proceed with the login
         # flow.
@@ -1685,6 +1691,7 @@ async def complete_sso_login(
             extra_attributes,
             new_user=new_user,
             user_profile_data=profile,
+            auth_provider_session_id=auth_provider_session_id,
         )
 
     def _complete_sso_login(
@@ -1696,6 +1703,7 @@ def _complete_sso_login(
         extra_attributes: Optional[JsonDict] = None,
         new_user: bool = False,
         user_profile_data: Optional[ProfileInfo] = None,
+        auth_provider_session_id: Optional[str] = None,
     ) -> None:
         """
         The synchronous portion of complete_sso_login.
@@ -1717,7 +1725,9 @@ def _complete_sso_login(
 
         # Create a login token
         login_token = self.macaroon_gen.generate_short_term_login_token(
-            registered_user_id, auth_provider_id=auth_provider_id
+            registered_user_id,
+            auth_provider_id=auth_provider_id,
+            auth_provider_session_id=auth_provider_session_id,
         )
 
         # Append the login token to the original redirect URL (i.e. with its query
@@ -1822,6 +1832,7 @@ def generate_short_term_login_token(
         self,
         user_id: str,
         auth_provider_id: str,
+        auth_provider_session_id: Optional[str] = None,
         duration_in_ms: int = (2 * 60 * 1000),
     ) -> str:
         macaroon = self._generate_base_macaroon(user_id)
@@ -1830,6 +1841,10 @@ def generate_short_term_login_token(
         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,))
+        if auth_provider_session_id is not None:
+            macaroon.add_first_party_caveat(
+                "auth_provider_session_id = %s" % (auth_provider_session_id,)
+            )
         return macaroon.serialize()
 
     def verify_short_term_login_token(self, token: str) -> LoginTokenAttributes:
@@ -1851,15 +1866,28 @@ def verify_short_term_login_token(self, token: str) -> LoginTokenAttributes:
         user_id = get_value_from_macaroon(macaroon, "user_id")
         auth_provider_id = get_value_from_macaroon(macaroon, "auth_provider_id")
 
+        auth_provider_session_id: Optional[str] = None
+        try:
+            auth_provider_session_id = get_value_from_macaroon(
+                macaroon, "auth_provider_session_id"
+            )
+        except MacaroonVerificationFailedException:
+            pass
+
         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 = "))
+        v.satisfy_general(lambda c: c.startswith("auth_provider_session_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)
+        return LoginTokenAttributes(
+            user_id=user_id,
+            auth_provider_id=auth_provider_id,
+            auth_provider_session_id=auth_provider_session_id,
+        )
 
     def generate_delete_pusher_token(self, user_id: str) -> str:
         macaroon = self._generate_base_macaroon(user_id)

synapse/handlers/device.py

@@ -301,6 +301,8 @@ async def check_device_registered(
         user_id: str,
         device_id: Optional[str],
         initial_device_display_name: Optional[str] = None,
+        auth_provider_id: Optional[str] = None,
+        auth_provider_session_id: Optional[str] = None,
     ) -> str:
         """
         If the given device has not been registered, register it with the
@@ -312,6 +314,8 @@ async def check_device_registered(
             user_id:  @user:id
             device_id: device id supplied by client
             initial_device_display_name: device display name from client
+            auth_provider_id: The SSO IdP the user used, if any.
+            auth_provider_session_id: The session ID (sid) got from the SSO IdP.
         Returns:
             device id (generated if none was supplied)
         """
@@ -323,6 +327,8 @@ async def check_device_registered(
                 user_id=user_id,
                 device_id=device_id,
                 initial_device_display_name=initial_device_display_name,
+                auth_provider_id=auth_provider_id,
+                auth_provider_session_id=auth_provider_session_id,
             )
             if new_device:
                 await self.notify_device_update(user_id, [device_id])
@@ -337,6 +343,8 @@ async def check_device_registered(
                 user_id=user_id,
                 device_id=new_device_id,
                 initial_device_display_name=initial_device_display_name,
+                auth_provider_id=auth_provider_id,
+                auth_provider_session_id=auth_provider_session_id,
             )
             if new_device:
                 await self.notify_device_update(user_id, [new_device_id])

synapse/handlers/oidc.py

@@ -23,7 +23,7 @@
 from authlib.jose import JsonWebToken, jwt
 from authlib.oauth2.auth import ClientAuth
 from authlib.oauth2.rfc6749.parameters import prepare_grant_uri
-from authlib.oidc.core import CodeIDToken, ImplicitIDToken, UserInfo
+from authlib.oidc.core import CodeIDToken, UserInfo
 from authlib.oidc.discovery import OpenIDProviderMetadata, get_well_known_url
 from jinja2 import Environment, Template
 from pymacaroons.exceptions import (
@@ -117,7 +117,8 @@ async def load_metadata(self) -> None:
         for idp_id, p in self._providers.items():
             try:
                 await p.load_metadata()
-                await p.load_jwks()
+                if not p._uses_userinfo:
+                    await p.load_jwks()
             except Exception as e:
                 raise Exception(
                     "Error while initialising OIDC provider %r" % (idp_id,)
@@ -498,10 +499,6 @@ async def load_jwks(self, force: bool = False) -> JWKS:
         return await self._jwks.get()
 
     async def _load_jwks(self) -> JWKS:
-        if self._uses_userinfo:
-            # We're not using jwt signing, return an empty jwk set
-            return {"keys": []}
-
         metadata = await self.load_metadata()
 
         # Load the JWKS using the `jwks_uri` metadata.
@@ -663,7 +660,7 @@ async def _fetch_userinfo(self, token: Token) -> UserInfo:
 
         return UserInfo(resp)
 
-    async def _parse_id_token(self, token: Token, nonce: str) -> UserInfo:
+    async def _parse_id_token(self, token: Token, nonce: str) -> CodeIDToken:
         """Return an instance of UserInfo from token's ``id_token``.
 
         Args:
@@ -673,7 +670,7 @@ async def _parse_id_token(self, token: Token, nonce: str) -> UserInfo:
                 request. This value should match the one inside the token.
 
         Returns:
-            An object representing the user.
+            The decoded claims in the ID token.
         """
         metadata = await self.load_metadata()
         claims_params = {
@@ -684,9 +681,6 @@ async def _parse_id_token(self, token: Token, nonce: str) -> UserInfo:
             # If we got an `access_token`, there should be an `at_hash` claim
             # in the `id_token` that we can check against.
             claims_params["access_token"] = token["access_token"]
-            claims_cls = CodeIDToken
-        else:
-            claims_cls = ImplicitIDToken
 
         alg_values = metadata.get("id_token_signing_alg_values_supported", ["RS256"])
         jwt = JsonWebToken(alg_values)
@@ -703,7 +697,7 @@ async def _parse_id_token(self, token: Token, nonce: str) -> UserInfo:
             claims = jwt.decode(
                 id_token,
                 key=jwk_set,
-                claims_cls=claims_cls,
+                claims_cls=CodeIDToken,
                 claims_options=claim_options,
                 claims_params=claims_params,
             )
@@ -713,15 +707,16 @@ async def _parse_id_token(self, token: Token, nonce: str) -> UserInfo:
             claims = jwt.decode(
                 id_token,
                 key=jwk_set,
-                claims_cls=claims_cls,
+                claims_cls=CodeIDToken,
                 claims_options=claim_options,
                 claims_params=claims_params,
             )
 
         logger.debug("Decoded id_token JWT %r; validating", claims)
 
         claims.validate(leeway=120)  # allows 2 min of clock skew
-        return UserInfo(claims)
+
+        return claims
 
     async def handle_redirect_request(
         self,
@@ -837,22 +832,37 @@ async def handle_oidc_callback(
 
         logger.debug("Successfully obtained OAuth2 token data: %r", token)
 
-        # Now that we have a token, get the userinfo, either by decoding the
-        # `id_token` or by fetching the `userinfo_endpoint`.
+        # If there is an id_token, it should be validated, regardless of the
+        # userinfo endpoint is used or not.
+        if token.get("id_token") is not None:
+            try:
+                id_token = await self._parse_id_token(token, nonce=session_data.nonce)
+                sid = id_token.get("sid")
+            except Exception as e:
+                logger.exception("Invalid id_token")
+                self._sso_handler.render_error(request, "invalid_token", str(e))
+                return
+        else:
+            id_token = None
+            sid = None
+
+        # Now that we have a token, get the userinfo either from the `id_token`
+        # claims or by fetching the `userinfo_endpoint`.
         if self._uses_userinfo:
             try:
                 userinfo = await self._fetch_userinfo(token)
             except Exception as e:
                 logger.exception("Could not fetch userinfo")
                 self._sso_handler.render_error(request, "fetch_error", str(e))
                 return
+        elif id_token is not None:
+            userinfo = UserInfo(id_token)
         else:
-            try:
-                userinfo = await self._parse_id_token(token, nonce=session_data.nonce)
-            except Exception as e:
-                logger.exception("Invalid id_token")
-                self._sso_handler.render_error(request, "invalid_token", str(e))
-                return
+            logger.error("Missing id_token in token response")
+            self._sso_handler.render_error(
+                request, "invalid_token", "Missing id_token in token response"
+            )
+            return
 
         # first check if we're doing a UIA
         if session_data.ui_auth_session_id:
@@ -884,7 +894,7 @@ async def handle_oidc_callback(
         # Call the mapper to register/login the user
         try:
             await self._complete_oidc_login(
-                userinfo, token, request, session_data.client_redirect_url
+                userinfo, token, request, session_data.client_redirect_url, sid
             )
         except MappingException as e:
             logger.exception("Could not map user")
@@ -896,6 +906,7 @@ async def _complete_oidc_login(
         token: Token,
         request: SynapseRequest,
         client_redirect_url: str,
+        sid: Optional[str],
     ) -> None:
         """Given a UserInfo response, complete the login flow
 
@@ -1008,6 +1019,7 @@ async def grandfather_existing_users() -> Optional[str]:
             oidc_response_to_user_attributes,
             grandfather_existing_users,
             extra_attributes,
+            auth_provider_session_id=sid,
         )
 
     def _remote_id_from_userinfo(self, userinfo: UserInfo) -> str:

synapse/handlers/register.py

@@ -746,6 +746,7 @@ async def register_device(
         is_appservice_ghost: bool = False,
         auth_provider_id: Optional[str] = None,
         should_issue_refresh_token: bool = False,
+        auth_provider_session_id: Optional[str] = None,
     ) -> Tuple[str, str, Optional[int], Optional[str]]:
         """Register a device for a user and generate an access token.
 
@@ -756,9 +757,9 @@ async def register_device(
             device_id: The device ID to check, or None to generate a new one.
             initial_display_name: An optional display name for the device.
             is_guest: Whether this is a guest account
-            auth_provider_id: The SSO IdP the user used, if any (just used for the
-                prometheus metrics).
+            auth_provider_id: The SSO IdP the user used, if any.
             should_issue_refresh_token: Whether it should also issue a refresh token
+            auth_provider_session_id: The session ID received during login from the SSO IdP.
         Returns:
             Tuple of device ID, access token, access token expiration time and refresh token
         """
@@ -769,6 +770,8 @@ async def register_device(
             is_guest=is_guest,
             is_appservice_ghost=is_appservice_ghost,
             should_issue_refresh_token=should_issue_refresh_token,
+            auth_provider_id=auth_provider_id,
+            auth_provider_session_id=auth_provider_session_id,
         )
 
         login_counter.labels(
@@ -791,6 +794,8 @@ async def register_device_inner(
         is_guest: bool = False,
         is_appservice_ghost: bool = False,
         should_issue_refresh_token: bool = False,
+        auth_provider_id: Optional[str] = None,
+        auth_provider_session_id: Optional[str] = None,
     ) -> LoginDict:
         """Helper for register_device
 
@@ -822,7 +827,11 @@ class and RegisterDeviceReplicationServlet.
         refresh_token_id = None
 
         registered_device_id = await self.device_handler.check_device_registered(
-            user_id, device_id, initial_display_name
+            user_id,
+            device_id,
+            initial_display_name,
+            auth_provider_id=auth_provider_id,
+            auth_provider_session_id=auth_provider_session_id,
         )
         if is_guest:
             assert access_token_expiry is None

synapse/handlers/sso.py

@@ -365,6 +365,7 @@ async def complete_sso_login_request(
         sso_to_matrix_id_mapper: Callable[[int], Awaitable[UserAttributes]],
         grandfather_existing_users: Callable[[], Awaitable[Optional[str]]],
         extra_login_attributes: Optional[JsonDict] = None,
+        auth_provider_session_id: Optional[str] = None,
     ) -> None:
         """
         Given an SSO ID, retrieve the user ID for it and possibly register the user.
@@ -415,6 +416,8 @@ async def complete_sso_login_request(
             extra_login_attributes: An optional dictionary of extra
                 attributes to be provided to the client in the login response.
 
+            auth_provider_session_id: An optional session ID from the IdP.
+
         Raises:
             MappingException if there was a problem mapping the response to a user.
             RedirectException: if the mapping provider needs to redirect the user
@@ -490,6 +493,7 @@ async def complete_sso_login_request(
             client_redirect_url,
             extra_login_attributes,
             new_user=new_user,
+            auth_provider_session_id=auth_provider_session_id,
         )
 
     async def _call_attribute_mapper(

synapse/module_api/__init__.py

@@ -626,6 +626,7 @@ def generate_short_term_login_token(
         user_id: str,
         duration_in_ms: int = (2 * 60 * 1000),
         auth_provider_id: str = "",
+        auth_provider_session_id: Optional[str] = None,
     ) -> str:
         """Generate a login token suitable for m.login.token authentication
 
@@ -643,6 +644,7 @@ def generate_short_term_login_token(
         return self._hs.get_macaroon_generator().generate_short_term_login_token(
             user_id,
             auth_provider_id,
+            auth_provider_session_id,
             duration_in_ms,
         )