diff --git a/changelog.d/9108.bugfix b/changelog.d/9108.bugfix
new file mode 100644
index 0000000000..465ef63508
--- /dev/null
+++ b/changelog.d/9108.bugfix
@@ -0,0 +1 @@
+Fix "Unhandled error in Deferred: BodyExceededMaxSize" errors when .well-known files that are too large.
diff --git a/synapse/http/client.py b/synapse/http/client.py
index dc4b81ca60..df498c8645 100644
--- a/synapse/http/client.py
+++ b/synapse/http/client.py
@@ -766,14 +766,24 @@ class _ReadBodyWithMaxSizeProtocol(protocol.Protocol):
self.max_size = max_size
def dataReceived(self, data: bytes) -> None:
+ # If the deferred was called, bail early.
+ if self.deferred.called:
+ return
+
self.stream.write(data)
self.length += len(data)
+ # The first time the maximum size is exceeded, error and cancel the
+ # connection. dataReceived might be called again if data was received
+ # in the meantime.
if self.max_size is not None and self.length >= self.max_size:
self.deferred.errback(BodyExceededMaxSize())
- self.deferred = defer.Deferred()
self.transport.loseConnection()
def connectionLost(self, reason: Failure) -> None:
+ # If the maximum size was already exceeded, there's nothing to do.
+ if self.deferred.called:
+ return
+
if reason.check(ResponseDone):
self.deferred.callback(self.length)
elif reason.check(PotentialDataLoss):
diff --git a/tests/http/federation/test_matrix_federation_agent.py b/tests/http/federation/test_matrix_federation_agent.py
index 4e51839d0f..686012dd25 100644
--- a/tests/http/federation/test_matrix_federation_agent.py
+++ b/tests/http/federation/test_matrix_federation_agent.py
@@ -1095,7 +1095,7 @@ class MatrixFederationAgentTests(unittest.TestCase):
# Expire both caches and repeat the request
self.reactor.pump((10000.0,))
- # Repated the request, this time it should fail if the lookup fails.
+ # Repeat the request, this time it should fail if the lookup fails.
fetch_d = defer.ensureDeferred(
self.well_known_resolver.get_well_known(b"testserv")
)
@@ -1130,7 +1130,7 @@ class MatrixFederationAgentTests(unittest.TestCase):
content=b'{ "m.server": "' + (b"a" * WELL_KNOWN_MAX_SIZE) + b'" }',
)
- # The result is sucessful, but disabled delegation.
+ # The result is successful, but disabled delegation.
r = self.successResultOf(fetch_d)
self.assertIsNone(r.delegated_server)
diff --git a/tests/http/test_client.py b/tests/http/test_client.py
new file mode 100644
index 0000000000..f17c122e93
--- /dev/null
+++ b/tests/http/test_client.py
@@ -0,0 +1,101 @@
+# Copyright 2021 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.
+
+from io import BytesIO
+
+from mock import Mock
+
+from twisted.python.failure import Failure
+from twisted.web.client import ResponseDone
+
+from synapse.http.client import BodyExceededMaxSize, read_body_with_max_size
+
+from tests.unittest import TestCase
+
+
+class ReadBodyWithMaxSizeTests(TestCase):
+ def setUp(self):
+ """Start reading the body, returns the response, result and proto"""
+ self.response = Mock()
+ self.result = BytesIO()
+ self.deferred = read_body_with_max_size(self.response, self.result, 6)
+
+ # Fish the protocol out of the response.
+ self.protocol = self.response.deliverBody.call_args[0][0]
+ self.protocol.transport = Mock()
+
+ def _cleanup_error(self):
+ """Ensure that the error in the Deferred is handled gracefully."""
+ called = [False]
+
+ def errback(f):
+ called[0] = True
+
+ self.deferred.addErrback(errback)
+ self.assertTrue(called[0])
+
+ def test_no_error(self):
+ """A response that is NOT too large."""
+
+ # Start sending data.
+ self.protocol.dataReceived(b"12345")
+ # Close the connection.
+ self.protocol.connectionLost(Failure(ResponseDone()))
+
+ self.assertEqual(self.result.getvalue(), b"12345")
+ self.assertEqual(self.deferred.result, 5)
+
+ def test_too_large(self):
+ """A response which is too large raises an exception."""
+
+ # Start sending data.
+ self.protocol.dataReceived(b"1234567890")
+ # Close the connection.
+ self.protocol.connectionLost(Failure(ResponseDone()))
+
+ self.assertEqual(self.result.getvalue(), b"1234567890")
+ self.assertIsInstance(self.deferred.result, Failure)
+ self.assertIsInstance(self.deferred.result.value, BodyExceededMaxSize)
+ self._cleanup_error()
+
+ def test_multiple_packets(self):
+ """Data should be accummulated through mutliple packets."""
+
+ # Start sending data.
+ self.protocol.dataReceived(b"12")
+ self.protocol.dataReceived(b"34")
+ # Close the connection.
+ self.protocol.connectionLost(Failure(ResponseDone()))
+
+ self.assertEqual(self.result.getvalue(), b"1234")
+ self.assertEqual(self.deferred.result, 4)
+
+ def test_additional_data(self):
+ """A connection can receive data after being closed."""
+
+ # Start sending data.
+ self.protocol.dataReceived(b"1234567890")
+ self.assertIsInstance(self.deferred.result, Failure)
+ self.assertIsInstance(self.deferred.result.value, BodyExceededMaxSize)
+ self.protocol.transport.loseConnection.assert_called_once()
+
+ # More data might have come in.
+ self.protocol.dataReceived(b"1234567890")
+ # Close the connection.
+ self.protocol.connectionLost(Failure(ResponseDone()))
+
+ self.assertEqual(self.result.getvalue(), b"1234567890")
+ self.assertIsInstance(self.deferred.result, Failure)
+ self.assertIsInstance(self.deferred.result.value, BodyExceededMaxSize)
+ self._cleanup_error()
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