1 files changed, 90 insertions, 0 deletions
diff --git a/synapse/handlers/sso.py b/synapse/handlers/sso.py
new file mode 100644
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+++ b/synapse/handlers/sso.py
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+# -*- coding: utf-8 -*-
+# Copyright 2020 The Matrix.org Foundation C.I.C.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+import logging
+from typing import TYPE_CHECKING, Optional
+
+from synapse.handlers._base import BaseHandler
+from synapse.http.server import respond_with_html
+
+if TYPE_CHECKING:
+    from synapse.server import HomeServer
+
+logger = logging.getLogger(__name__)
+
+
+class MappingException(Exception):
+    """Used to catch errors when mapping the UserInfo object
+    """
+
+
+class SsoHandler(BaseHandler):
+    def __init__(self, hs: "HomeServer"):
+        super().__init__(hs)
+        self._error_template = hs.config.sso_error_template
+
+    def render_error(
+        self, request, error: str, error_description: Optional[str] = None
+    ) -> None:
+        """Renders the error template and responds 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.
+            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)
+
+    async def get_sso_user_by_remote_user_id(
+        self, auth_provider_id: str, remote_user_id: str
+    ) -> Optional[str]:
+        """
+        Maps the user ID of a remote IdP to a mxid for a previously seen user.
+
+        If the user has not been seen yet, this will return None.
+
+        Args:
+            auth_provider_id: A unique identifier for this SSO provider, e.g.
+                "oidc" or "saml".
+            remote_user_id: The user ID according to the remote IdP. This might
+                be an e-mail address, a GUID, or some other form. It must be
+                unique and immutable.
+
+        Returns:
+            The mxid of a previously seen user.
+        """
+        # Check if we already have a mapping for this user.
+        logger.info(
+            "Looking for existing mapping for user %s:%s",
+            auth_provider_id,
+            remote_user_id,
+        )
+        previously_registered_user_id = await self.store.get_user_by_external_id(
+            auth_provider_id, remote_user_id,
+        )
+
+        # A match was found, return the user ID.
+        if previously_registered_user_id is not None:
+            logger.info("Found existing mapping %s", previously_registered_user_id)
+            return previously_registered_user_id
+
+        # No match.
+        return None