Implement .well-known handling (#4262)

Sometimes it's useful for synapse to generate its own .well-known file.

synapse/rest/well_known.py

@@ -0,0 +1,70 @@
+# -*- coding: utf-8 -*-
+# Copyright 2018 New Vector Ltd.
+#
+# 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 json
+import logging
+
+from twisted.web.resource import Resource
+
+logger = logging.getLogger(__name__)
+
+
+class WellKnownBuilder(object):
+    """Utility to construct the well-known response
+
+    Args:
+        hs (synapse.server.HomeServer):
+    """
+    def __init__(self, hs):
+        self._config = hs.config
+
+    def get_well_known(self):
+        # if we don't have a public_base_url, we can't help much here.
+        if self._config.public_baseurl is None:
+            return None
+
+        result = {
+            "m.homeserver": {
+                "base_url": self._config.public_baseurl,
+            },
+        }
+
+        if self._config.default_identity_server:
+            result["m.identity_server"] = {
+                "base_url": self._config.default_identity_server,
+            }
+
+        return result
+
+
+class WellKnownResource(Resource):
+    """A Twisted web resource which renders the .well-known file"""
+
+    isLeaf = 1
+
+    def __init__(self, hs):
+        Resource.__init__(self)
+        self._well_known_builder = WellKnownBuilder(hs)
+
+    def render_GET(self, request):
+        r = self._well_known_builder.get_well_known()
+        if not r:
+            request.setResponseCode(404)
+            request.setHeader(b"Content-Type", b"text/plain")
+            return b'.well-known not available'
+
+        logger.error("returning: %s", r)
+        request.setHeader(b"Content-Type", b"application/json")
+        return json.dumps(r).encode("utf-8")