1 files changed, 150 insertions, 0 deletions
diff --git a/synapse/http/proxy.py b/synapse/http/proxy.py
new file mode 100644
index 0000000000..58a5f7f0c9
--- /dev/null
+++ b/synapse/http/proxy.py
@@ -0,0 +1,150 @@
+#  Copyright 2023 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
+import urllib.parse
+from typing import TYPE_CHECKING, Any, Optional, Tuple, cast
+
+from twisted.internet import protocol
+from twisted.internet.interfaces import ITCPTransport
+from twisted.internet.protocol import connectionDone
+from twisted.python import failure
+from twisted.python.failure import Failure
+from twisted.web.client import ResponseDone
+from twisted.web.http import PotentialDataLoss
+from twisted.web.http_headers import Headers
+from twisted.web.iweb import IAgent, IResponse
+from twisted.web.resource import IResource
+from twisted.web.server import Site
+
+from synapse.http import QuieterFileBodyProducer
+from synapse.http.server import _AsyncResource
+from synapse.logging.context import make_deferred_yieldable, run_in_background
+from synapse.types import ISynapseReactor
+from synapse.util.async_helpers import timeout_deferred
+
+if TYPE_CHECKING:
+    from synapse.http.site import SynapseRequest
+
+logger = logging.getLogger(__name__)
+
+
+class ProxyResource(_AsyncResource):
+    isLeaf = True
+
+    def __init__(self, reactor: ISynapseReactor, federation_agent: IAgent):
+        super().__init__(True)
+
+        self.reactor = reactor
+        self.agent = federation_agent
+
+    async def _async_render(self, request: "SynapseRequest") -> Tuple[int, Any]:
+        assert request.uri.startswith(b"matrix://")
+
+        logger.info("Got proxy request %s", request.uri)
+
+        headers = Headers()
+        for header_name in (b"User-Agent", b"Authorization", b"Content-Type"):
+            header_value = request.getHeader(header_name)
+            if header_value:
+                headers.addRawHeader(header_name, header_value)
+
+        request_deferred = run_in_background(
+            self.agent.request,
+            request.method,
+            request.uri,
+            headers=headers,
+            bodyProducer=QuieterFileBodyProducer(request.content),
+        )
+        request_deferred = timeout_deferred(
+            request_deferred,
+            timeout=90,
+            reactor=self.reactor,
+        )
+
+        response = await make_deferred_yieldable(request_deferred)
+
+        logger.info("Got proxy response %s", response.code)
+
+        return response.code, response
+
+    def _send_response(
+        self,
+        request: "SynapseRequest",
+        code: int,
+        response_object: Any,
+    ) -> None:
+        response = cast(IResponse, response_object)
+
+        request.setResponseCode(code)
+
+        # Copy headers.
+        for k, v in response.headers.getAllRawHeaders():
+            request.responseHeaders.setRawHeaders(k, v)
+
+        response.deliverBody(_ProxyResponseBody(request))
+
+    def _send_error_response(
+        self,
+        f: failure.Failure,
+        request: "SynapseRequest",
+    ) -> None:
+        request.setResponseCode(502)
+        request.finish()
+
+
+class _ProxyResponseBody(protocol.Protocol):
+    transport: Optional[ITCPTransport] = None
+
+    def __init__(self, request: "SynapseRequest") -> None:
+        self._request = request
+
+    def dataReceived(self, data: bytes) -> None:
+        if self._request._disconnected and self.transport is not None:
+            self.transport.abortConnection()
+            return
+
+        self._request.write(data)
+
+    def connectionLost(self, reason: Failure = connectionDone) -> None:
+        if self._request.finished:
+            return
+
+        if reason.check(ResponseDone):
+            self._request.finish()
+        elif reason.check(PotentialDataLoss):
+            # TODO: ARGH
+            self._request.finish()
+        else:
+            self._request.transport.abortConnection()
+
+
+class ProxySite(Site):
+    def __init__(
+        self,
+        resource: IResource,
+        reactor: ISynapseReactor,
+        federation_agent: IAgent,
+    ):
+        super().__init__(resource, reactor=reactor)
+
+        self._proxy_resource = ProxyResource(reactor, federation_agent)
+
+    def getResourceFor(self, request: "SynapseRequest") -> IResource:
+        uri = urllib.parse.urlparse(request.uri)
+        if uri.scheme == b"matrix":
+            return self._proxy_resource
+
+        return super().getResourceFor(request)