Abstract shared SSO code. (#8765)

De-duplicates code between the SAML and OIDC implementations.

Author: clokep

changelog.d/8765.misc

@@ -0,0 +1 @@
+Consolidate logic between the OpenID Connect and SAML code.

synapse/handlers/oidc_handler.py

@@ -34,7 +34,8 @@
 from twisted.web.client import readBody
 
 from synapse.config import ConfigError
-from synapse.http.server import respond_with_html
+from synapse.handlers._base import BaseHandler
+from synapse.handlers.sso import MappingException
 from synapse.http.site import SynapseRequest
 from synapse.logging.context import make_deferred_yieldable
 from synapse.types import JsonDict, UserID, map_username_to_mxid_localpart
@@ -83,17 +84,12 @@ def __str__(self):
         return self.error
 
 
-class MappingException(Exception):
-    """Used to catch errors when mapping the UserInfo object
-    """
-
-
-class OidcHandler:
+class OidcHandler(BaseHandler):
     """Handles requests related to the OpenID Connect login flow.
     """
 
     def __init__(self, hs: "HomeServer"):
-        self.hs = hs
+        super().__init__(hs)
         self._callback_url = hs.config.oidc_callback_url  # type: str
         self._scopes = hs.config.oidc_scopes  # type: List[str]
         self._user_profile_method = hs.config.oidc_user_profile_method  # type: str
@@ -120,36 +116,13 @@ def __init__(self, hs: "HomeServer"):
         self._http_client = hs.get_proxied_http_client()
         self._auth_handler = hs.get_auth_handler()
         self._registration_handler = hs.get_registration_handler()
-        self._datastore = hs.get_datastore()
-        self._clock = hs.get_clock()
-        self._hostname = hs.hostname  # type: str
         self._server_name = hs.config.server_name  # type: str
         self._macaroon_secret_key = hs.config.macaroon_secret_key
-        self._error_template = hs.config.sso_error_template
 
         # identifier for the external_ids table
         self._auth_provider_id = "oidc"
 
-    def _render_error(
-        self, request, error: str, error_description: Optional[str] = None
-    ) -> None:
-        """Render the error template and respond to the request with it.
-
-        This is used to show errors to the user. The template of this page can
-        be found under `synapse/res/templates/sso_error.html`.
-
-        Args:
-            request: The incoming request from the browser.
-                We'll respond with an HTML page describing the error.
-            error: A technical identifier for this error. Those include
-                well-known OAuth2/OIDC error types like invalid_request or
-                access_denied.
-            error_description: A human-readable description of the error.
-        """
-        html = self._error_template.render(
-            error=error, error_description=error_description
-        )
-        respond_with_html(request, 400, html)
+        self._sso_handler = hs.get_sso_handler()
 
     def _validate_metadata(self):
         """Verifies the provider metadata.
@@ -571,7 +544,7 @@ async def handle_oidc_callback(self, request: SynapseRequest) -> None:
 
         Since we might want to display OIDC-related errors in a user-friendly
         way, we don't raise SynapseError from here. Instead, we call
-        ``self._render_error`` which displays an HTML page for the error.
+        ``self._sso_handler.render_error`` which displays an HTML page for the error.
 
         Most of the OpenID Connect logic happens here:
 
@@ -609,7 +582,7 @@ async def handle_oidc_callback(self, request: SynapseRequest) -> None:
             if error != "access_denied":
                 logger.error("Error from the OIDC provider: %s %s", error, description)
 
-            self._render_error(request, error, description)
+            self._sso_handler.render_error(request, error, description)
             return
 
         # otherwise, it is presumably a successful response. see:
@@ -619,7 +592,9 @@ async def handle_oidc_callback(self, request: SynapseRequest) -> None:
         session = request.getCookie(SESSION_COOKIE_NAME)  # type: Optional[bytes]
         if session is None:
             logger.info("No session cookie found")
-            self._render_error(request, "missing_session", "No session cookie found")
+            self._sso_handler.render_error(
+                request, "missing_session", "No session cookie found"
+            )
             return
 
         # Remove the cookie. There is a good chance that if the callback failed
@@ -637,7 +612,9 @@ async def handle_oidc_callback(self, request: SynapseRequest) -> None:
         # Check for the state query parameter
         if b"state" not in request.args:
             logger.info("State parameter is missing")
-            self._render_error(request, "invalid_request", "State parameter is missing")
+            self._sso_handler.render_error(
+                request, "invalid_request", "State parameter is missing"
+            )
             return
 
         state = request.args[b"state"][0].decode()
@@ -651,17 +628,19 @@ async def handle_oidc_callback(self, request: SynapseRequest) -> None:
             ) = self._verify_oidc_session_token(session, state)
         except MacaroonDeserializationException as e:
             logger.exception("Invalid session")
-            self._render_error(request, "invalid_session", str(e))
+            self._sso_handler.render_error(request, "invalid_session", str(e))
             return
         except MacaroonInvalidSignatureException as e:
             logger.exception("Could not verify session")
-            self._render_error(request, "mismatching_session", str(e))
+            self._sso_handler.render_error(request, "mismatching_session", str(e))
             return
 
         # Exchange the code with the provider
         if b"code" not in request.args:
             logger.info("Code parameter is missing")
-            self._render_error(request, "invalid_request", "Code parameter is missing")
+            self._sso_handler.render_error(
+                request, "invalid_request", "Code parameter is missing"
+            )
             return
 
         logger.debug("Exchanging code")
@@ -670,7 +649,7 @@ async def handle_oidc_callback(self, request: SynapseRequest) -> None:
             token = await self._exchange_code(code)
         except OidcError as e:
             logger.exception("Could not exchange code")
-            self._render_error(request, e.error, e.error_description)
+            self._sso_handler.render_error(request, e.error, e.error_description)
             return
 
         logger.debug("Successfully obtained OAuth2 access token")
@@ -683,15 +662,15 @@ async def handle_oidc_callback(self, request: SynapseRequest) -> None:
                 userinfo = await self._fetch_userinfo(token)
             except Exception as e:
                 logger.exception("Could not fetch userinfo")
-                self._render_error(request, "fetch_error", str(e))
+                self._sso_handler.render_error(request, "fetch_error", str(e))
                 return
         else:
             logger.debug("Extracting userinfo from id_token")
             try:
                 userinfo = await self._parse_id_token(token, nonce=nonce)
             except Exception as e:
                 logger.exception("Invalid id_token")
-                self._render_error(request, "invalid_token", str(e))
+                self._sso_handler.render_error(request, "invalid_token", str(e))
                 return
 
         # Pull out the user-agent and IP from the request.
@@ -705,7 +684,7 @@ async def handle_oidc_callback(self, request: SynapseRequest) -> None:
             )
         except MappingException as e:
             logger.exception("Could not map user")
-            self._render_error(request, "mapping_error", str(e))
+            self._sso_handler.render_error(request, "mapping_error", str(e))
             return
 
         # Mapping providers might not have get_extra_attributes: only call this
@@ -770,7 +749,7 @@ def _generate_oidc_session_token(
             macaroon.add_first_party_caveat(
                 "ui_auth_session_id = %s" % (ui_auth_session_id,)
             )
-        now = self._clock.time_msec()
+        now = self.clock.time_msec()
         expiry = now + duration_in_ms
         macaroon.add_first_party_caveat("time < %d" % (expiry,))
 
@@ -845,7 +824,7 @@ def _verify_expiry(self, caveat: str) -> bool:
         if not caveat.startswith(prefix):
             return False
         expiry = int(caveat[len(prefix) :])
-        now = self._clock.time_msec()
+        now = self.clock.time_msec()
         return now < expiry
 
     async def _map_userinfo_to_user(
@@ -885,20 +864,14 @@ async def _map_userinfo_to_user(
         # to be strings.
         remote_user_id = str(remote_user_id)
 
-        logger.info(
-            "Looking for existing mapping for user %s:%s",
-            self._auth_provider_id,
-            remote_user_id,
-        )
-
-        registered_user_id = await self._datastore.get_user_by_external_id(
+        # first of all, check if we already have a mapping for this user
+        previously_registered_user_id = await self._sso_handler.get_sso_user_by_remote_user_id(
             self._auth_provider_id, remote_user_id,
         )
+        if previously_registered_user_id:
+            return previously_registered_user_id
 
-        if registered_user_id is not None:
-            logger.info("Found existing mapping %s", registered_user_id)
-            return registered_user_id
-
+        # Otherwise, generate a new user.
         try:
             attributes = await self._user_mapping_provider.map_user_attributes(
                 userinfo, token
@@ -917,8 +890,8 @@ async def _map_userinfo_to_user(
 
         localpart = map_username_to_mxid_localpart(attributes["localpart"])
 
-        user_id = UserID(localpart, self._hostname).to_string()
-        users = await self._datastore.get_users_by_id_case_insensitive(user_id)
+        user_id = UserID(localpart, self.server_name).to_string()
+        users = await self.store.get_users_by_id_case_insensitive(user_id)
         if users:
             if self._allow_existing_users:
                 if len(users) == 1:
@@ -942,7 +915,8 @@ async def _map_userinfo_to_user(
                 default_display_name=attributes["display_name"],
                 user_agent_ips=(user_agent, ip_address),
             )
-        await self._datastore.record_user_external_id(
+
+        await self.store.record_user_external_id(
             self._auth_provider_id, remote_user_id, registered_user_id,
         )
         return registered_user_id