Allow additional SSO properties to be passed to the client

changelog.d/8413.feature

@@ -0,0 +1 @@
+Support passing additional single sign-on parameters to the client.

docs/sample_config.yaml

@@ -1735,6 +1735,14 @@ oidc_config:
       #
       #display_name_template: "{{ user.given_name }} {{ user.last_name }}"
 
+      # Jinja2 templates for extra attributes to send back to the client during
+      # login.
+      #
+      # Note that these are non-standard and clients will ignore them without modifications.
+      #
+      #extra_attributes:
+        #birthdate: "{ user.birthdate }"
+
 
 
 # Enable CAS for registration and login.

docs/sso_mapping_providers.md

@@ -57,7 +57,7 @@ A custom mapping provider must specify the following methods:
     - This method must return a string, which is the unique identifier for the
       user. Commonly the ``sub`` claim of the response.
 * `map_user_attributes(self, userinfo, token)`
-    - This method should be async.
+    - This method must be async.
     - Arguments:
       - `userinfo` - A `authlib.oidc.core.claims.UserInfo` object to extract user
                      information from.
@@ -66,6 +66,16 @@ A custom mapping provider must specify the following methods:
     - Returns a dictionary with two keys:
       - localpart: A required string, used to generate the Matrix ID.
       - displayname: An optional string, the display name for the user.
+* `get_extra_attributes(self, userinfo, token)`
+    - This method must be async.
+    - Arguments:
+      - `userinfo` - A `authlib.oidc.core.claims.UserInfo` object to extract user
+                     information from.
+      - `token` - A dictionary which includes information necessary to make
+                  further requests to the OpenID provider.
+    - Returns a dictionary that is suitable to be serialized to JSON. This
+      dictionary will be returned under the `extra_attributes` key in the
+      response during a successful login.
 
 ### Default OpenID Mapping Provider
 

synapse/config/oidc_config.py

@@ -204,6 +204,14 @@ def generate_config_section(self, config_dir_path, server_name, **kwargs):
               # If unset, no displayname will be set.
               #
               #display_name_template: "{{{{ user.given_name }}}} {{{{ user.last_name }}}}"
+
+              # Jinja2 templates for extra attributes to send back to the client during
+              # login.
+              #
+              # Note that these are non-standard and clients will ignore them without modifications.
+              #
+              #extra_attributes:
+                #birthdate: "{{ user.birthdate }}"
         """.format(
             mapping_provider=DEFAULT_USER_MAPPING_PROVIDER
         )

synapse/handlers/auth.py

@@ -137,6 +137,15 @@ def login_id_phone_to_thirdparty(identifier: JsonDict) -> Dict[str, str]:
     }
 
 
+@attr.s(slots=True)
+class SsoLoginExtraAttributes:
+    """Data we track about SAML2 sessions"""
+
+    # time the session was created, in milliseconds
+    creation_time = attr.ib(type=int)
+    extra_attributes = attr.ib(type=JsonDict)
+
+
 class AuthHandler(BaseHandler):
     SESSION_EXPIRE_MS = 48 * 60 * 60 * 1000
 
@@ -239,6 +248,10 @@ def __init__(self, hs):
         # cast to tuple for use with str.startswith
         self._whitelisted_sso_clients = tuple(hs.config.sso_client_whitelist)
 
+        # A mapping of user ID to extra attributes to include in the login
+        # response.
+        self._extra_attributes = {}  # type: Dict[str, SsoLoginExtraAttributes]
+
     async def validate_user_via_ui_auth(
         self,
         requester: Requester,
@@ -1165,6 +1178,7 @@ async def complete_sso_login(
         registered_user_id: str,
         request: SynapseRequest,
         client_redirect_url: str,
+        extra_attributes: Optional[JsonDict] = None,
     ):
         """Having figured out a mxid for this user, complete the HTTP request
 
@@ -1173,6 +1187,8 @@ async def complete_sso_login(
             request: The request to complete.
             client_redirect_url: The URL to which to redirect the user at the end of the
                 process.
+            extra_attributes: Extra attributes which will be passed to the client
+                during successful login. Must be JSON serializable.
         """
         # If the account has been deactivated, do not proceed with the login
         # flow.
@@ -1181,19 +1197,30 @@ async def complete_sso_login(
             respond_with_html(request, 403, self._sso_account_deactivated_template)
             return
 
-        self._complete_sso_login(registered_user_id, request, client_redirect_url)
+        self._complete_sso_login(
+            registered_user_id, request, client_redirect_url, extra_attributes
+        )
 
     def _complete_sso_login(
         self,
         registered_user_id: str,
         request: SynapseRequest,
         client_redirect_url: str,
+        extra_attributes: Optional[JsonDict] = None,
     ):
         """
         The synchronous portion of complete_sso_login.
 
         This exists purely for backwards compatibility of synapse.module_api.ModuleApi.
         """
+        # Store any extra attributes which will be passed in the login response.
+        # Note that this is per-user so it may overwrite a previous value, this
+        # is considered OK since the newest SSO attributes should be most valid.
+        if extra_attributes:
+            self._extra_attributes[registered_user_id] = SsoLoginExtraAttributes(
+                self._clock.time_msec(), extra_attributes,
+            )
+
         # Create a login token
         login_token = self.macaroon_gen.generate_short_term_login_token(
             registered_user_id
@@ -1226,6 +1253,39 @@ def _complete_sso_login(
         )
         respond_with_html(request, 200, html)
 
+    async def _sso_login_callback(self, login_result: JsonDict) -> None:
+        """
+        A login callback which might add additional attributes to the login response.
+
+        Args:
+            login_result: The data to be sent to the client. Includes the user
+                ID and access token.
+        """
+        # Expire attributes before processing. Note that there shouldn't be any
+        # valid logins that still have extra attributes.
+        self._expire_sso_extra_attributes()
+
+        extra_attributes = self._extra_attributes.get(login_result["user_id"])
+        if extra_attributes:
+            login_result.update(
+                (("extra_attributes", extra_attributes.extra_attributes),)
+            )
+
+    def _expire_sso_extra_attributes(self) -> None:
+        """
+        Iterate through the mapping of user IDs to extra attributes and remove any that are no longer valid.
+        """
+        # TODO This should match the amount of time the macaroon is valid for.
+        LOGIN_TOKEN_EXPIRATION_TIME = 2 * 60 * 1000
+        expire_before = self._clock.time_msec() - LOGIN_TOKEN_EXPIRATION_TIME
+        to_expire = set()
+        for user_id, data in self._extra_attributes.items():
+            if data.creation_time < expire_before:
+                to_expire.add(user_id)
+        for user_id in to_expire:
+            logger.debug("Expiring extra attributes for user %s", user_id)
+            del self._extra_attributes[user_id]
+
     @staticmethod
     def add_query_param_to_url(url: str, param_name: str, param: Any):
         url_parts = list(urllib.parse.urlparse(url))

synapse/handlers/oidc_handler.py

@@ -37,7 +37,7 @@
 from synapse.http.server import respond_with_html
 from synapse.http.site import SynapseRequest
 from synapse.logging.context import make_deferred_yieldable
-from synapse.types import UserID, map_username_to_mxid_localpart
+from synapse.types import JsonDict, UserID, map_username_to_mxid_localpart
 from synapse.util import json_decoder
 
 if TYPE_CHECKING:
@@ -707,14 +707,26 @@ async def handle_oidc_callback(self, request: SynapseRequest) -> None:
             self._render_error(request, "mapping_error", str(e))
             return
 
+        # Mapping providers might not have get_extra_attributes: only call this
+        # method if it exists. It might also raise NotImplementedError.
+        extra_attributes = None
+        get_extra_attributes = getattr(
+            self._user_mapping_provider, "get_extra_attributes"
+        )
+        if get_extra_attributes:
+            try:
+                extra_attributes = await get_extra_attributes(userinfo, token)
+            except NotImplementedError:
+                pass
+
         # and finally complete the login
         if ui_auth_session_id:
             await self._auth_handler.complete_sso_ui_auth(
                 user_id, ui_auth_session_id, request
             )
         else:
             await self._auth_handler.complete_sso_login(
-                user_id, request, client_redirect_url
+                user_id, request, client_redirect_url, extra_attributes
             )
 
     def _generate_oidc_session_token(
@@ -995,6 +1007,18 @@ async def map_user_attributes(
         """
         raise NotImplementedError()
 
+    async def get_extra_attributes(self, userinfo: UserInfo, token: Token) -> JsonDict:
+        """Map a ``UserInfo`` objects into additional attributes passed to the client during login.
+
+        Args:
+            userinfo: An object representing the user given by the OIDC provider
+            token: A dict with the tokens returned by the provider
+
+        Returns:
+            A dict containing additional attributes. Must be JSON serializable.
+        """
+        raise NotImplementedError()
+
 
 # Used to clear out "None" values in templates
 def jinja_finalize(thing):
@@ -1009,6 +1033,7 @@ class JinjaOidcMappingConfig:
     subject_claim = attr.ib()  # type: str
     localpart_template = attr.ib()  # type: Template
     display_name_template = attr.ib()  # type: Optional[Template]
+    extra_attributes = attr.ib()  # type: Dict[str, Template]
 
 
 class JinjaOidcMappingProvider(OidcMappingProvider[JinjaOidcMappingConfig]):
@@ -1047,10 +1072,22 @@ def parse_config(config: dict) -> JinjaOidcMappingConfig:
                     % (e,)
                 )
 
+        extra_attributes = {}  # type Dict[str, Template]
+        if "extra_attributes" in config:
+            for key, value in config["extra_attributes"].items():
+                try:
+                    extra_attributes[key] = env.from_string(value)
+                except Exception as e:
+                    raise ConfigError(
+                        "invalid jinja template for oidc_config.user_mapping_provider.config.extra_attributes.%s: %r"
+                        % (key, e,)
+                    )
+
         return JinjaOidcMappingConfig(
             subject_claim=subject_claim,
             localpart_template=localpart_template,
             display_name_template=display_name_template,
+            extra_attributes=extra_attributes,
         )
 
     def get_remote_user_id(self, userinfo: UserInfo) -> str:
@@ -1071,3 +1108,9 @@ async def map_user_attributes(
                 display_name = None
 
         return UserAttribute(localpart=localpart, display_name=display_name)
+
+    async def get_extra_attributes(self, userinfo: UserInfo, token: Token) -> JsonDict:
+        extras = {}  # type: Dict[str, str]
+        for key, template in self._config.extra_attributes.items():
+            extras[key] = template.render(user=userinfo).strip()
+        return extras

synapse/rest/client/v1/login.py

@@ -284,9 +284,7 @@ async def _complete_login(
         self,
         user_id: str,
         login_submission: JsonDict,
-        callback: Optional[
-            Callable[[Dict[str, str]], Awaitable[Dict[str, str]]]
-        ] = None,
+        callback: Optional[Callable[[Dict[str, str]], Awaitable[None]]] = None,
         create_non_existent_users: bool = False,
     ) -> Dict[str, str]:
         """Called when we've successfully authed the user and now need to
@@ -339,14 +337,24 @@ async def _complete_login(
         return result
 
     async def _do_token_login(self, login_submission: JsonDict) -> Dict[str, str]:
+        """
+        Handle the final stage of SSO login.
+
+        Args:
+             login_submission: The JSON request body.
+
+        Returns:
+            The body of the JSON response.
+        """
         token = login_submission["token"]
         auth_handler = self.auth_handler
         user_id = await auth_handler.validate_short_term_login_token_and_get_user_id(
             token
         )
 
-        result = await self._complete_login(user_id, login_submission)
-        return result
+        return await self._complete_login(
+            user_id, login_submission, self.auth_handler._sso_login_callback
+        )
 
     async def _do_jwt_login(self, login_submission: JsonDict) -> Dict[str, str]:
         token = login_submission.get("token", None)