From 51a20914a863ac24387c424ccee14aa877e218f8 Mon Sep 17 00:00:00 2001
From: Richard van der Hoff <1389908+richvdh@users.noreply.github.com>
Date: Fri, 23 Apr 2021 11:08:41 +0100
Subject: Limit the size of HTTP responses read over federation. (#9833)

---
 tests/http/test_fedclient.py | 59 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 59 insertions(+)

(limited to 'tests/http/test_fedclient.py')

diff --git a/tests/http/test_fedclient.py b/tests/http/test_fedclient.py
index 9e97185507..ed9a884d76 100644
--- a/tests/http/test_fedclient.py
+++ b/tests/http/test_fedclient.py
@@ -26,6 +26,7 @@ from twisted.web.http import HTTPChannel
 
 from synapse.api.errors import RequestSendFailed
 from synapse.http.matrixfederationclient import (
+    MAX_RESPONSE_SIZE,
     MatrixFederationHttpClient,
     MatrixFederationRequest,
 )
@@ -560,3 +561,61 @@ class FederationClientTests(HomeserverTestCase):
 
         f = self.failureResultOf(test_d)
         self.assertIsInstance(f.value, RequestSendFailed)
+
+    def test_too_big(self):
+        """
+        Test what happens if a huge response is returned from the remote endpoint.
+        """
+
+        test_d = defer.ensureDeferred(self.cl.get_json("testserv:8008", "foo/bar"))
+
+        self.pump()
+
+        # Nothing happened yet
+        self.assertNoResult(test_d)
+
+        # Make sure treq is trying to connect
+        clients = self.reactor.tcpClients
+        self.assertEqual(len(clients), 1)
+        (host, port, factory, _timeout, _bindAddress) = clients[0]
+        self.assertEqual(host, "1.2.3.4")
+        self.assertEqual(port, 8008)
+
+        # complete the connection and wire it up to a fake transport
+        protocol = factory.buildProtocol(None)
+        transport = StringTransport()
+        protocol.makeConnection(transport)
+
+        # that should have made it send the request to the transport
+        self.assertRegex(transport.value(), b"^GET /foo/bar")
+        self.assertRegex(transport.value(), b"Host: testserv:8008")
+
+        # Deferred is still without a result
+        self.assertNoResult(test_d)
+
+        # Send it a huge HTTP response
+        protocol.dataReceived(
+            b"HTTP/1.1 200 OK\r\n"
+            b"Server: Fake\r\n"
+            b"Content-Type: application/json\r\n"
+            b"\r\n"
+        )
+
+        self.pump()
+
+        # should still be waiting
+        self.assertNoResult(test_d)
+
+        sent = 0
+        chunk_size = 1024 * 512
+        while not test_d.called:
+            protocol.dataReceived(b"a" * chunk_size)
+            sent += chunk_size
+            self.assertLessEqual(sent, MAX_RESPONSE_SIZE)
+
+        self.assertEqual(sent, MAX_RESPONSE_SIZE)
+
+        f = self.failureResultOf(test_d)
+        self.assertIsInstance(f.value, RequestSendFailed)
+
+        self.assertTrue(transport.disconnecting)
-- 
cgit 1.4.1