Unverified Commit 51a20914 authored by Richard van der Hoff's avatar Richard van der Hoff Committed by GitHub
Browse files

Limit the size of HTTP responses read over federation. (#9833)

parent c1ddbbde
Limit the size of HTTP responses read over federation.
......@@ -33,6 +33,7 @@ import treq
from canonicaljson import encode_canonical_json
from netaddr import AddrFormatError, IPAddress, IPSet
from prometheus_client import Counter
from typing_extensions import Protocol
from zope.interface import implementer, provider
from OpenSSL import SSL
......@@ -754,6 +755,16 @@ def _timeout_to_request_timed_out_error(f: Failure):
return f
class ByteWriteable(Protocol):
"""The type of object which must be passed into read_body_with_max_size.
Typically this is a file object.
"""
def write(self, data: bytes) -> int:
pass
class BodyExceededMaxSize(Exception):
"""The maximum allowed size of the HTTP body was exceeded."""
......@@ -790,7 +801,7 @@ class _ReadBodyWithMaxSizeProtocol(protocol.Protocol):
transport = None # type: Optional[ITCPTransport]
def __init__(
self, stream: BinaryIO, deferred: defer.Deferred, max_size: Optional[int]
self, stream: ByteWriteable, deferred: defer.Deferred, max_size: Optional[int]
):
self.stream = stream
self.deferred = deferred
......@@ -830,7 +841,7 @@ class _ReadBodyWithMaxSizeProtocol(protocol.Protocol):
def read_body_with_max_size(
response: IResponse, stream: BinaryIO, max_size: Optional[int]
response: IResponse, stream: ByteWriteable, max_size: Optional[int]
) -> defer.Deferred:
"""
Read a HTTP response body to a file-object. Optionally enforcing a maximum file size.
......
# Copyright 2014-2016 OpenMarket Ltd
# Copyright 2018 New Vector Ltd
# Copyright 2014-2021 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.
......@@ -13,11 +12,13 @@
# See the License for the specific language governing permissions and
# limitations under the License.
import cgi
import codecs
import logging
import random
import sys
import typing
import urllib.parse
from io import BytesIO
from io import BytesIO, StringIO
from typing import Callable, Dict, List, Optional, Tuple, Union
import attr
......@@ -72,6 +73,9 @@ incoming_responses_counter = Counter(
"synapse_http_matrixfederationclient_responses", "", ["method", "code"]
)
# a federation response can be rather large (eg a big state_ids is 50M or so), so we
# need a generous limit here.
MAX_RESPONSE_SIZE = 100 * 1024 * 1024
MAX_LONG_RETRIES = 10
MAX_SHORT_RETRIES = 3
......@@ -167,12 +171,27 @@ async def _handle_json_response(
try:
check_content_type_is_json(response.headers)
# Use the custom JSON decoder (partially re-implements treq.json_content).
d = treq.text_content(response, encoding="utf-8")
d.addCallback(json_decoder.decode)
buf = StringIO()
d = read_body_with_max_size(response, BinaryIOWrapper(buf), MAX_RESPONSE_SIZE)
d = timeout_deferred(d, timeout=timeout_sec, reactor=reactor)
def parse(_len: int):
return json_decoder.decode(buf.getvalue())
d.addCallback(parse)
body = await make_deferred_yieldable(d)
except BodyExceededMaxSize as e:
# The response was too big.
logger.warning(
"{%s} [%s] JSON response exceeded max size %i - %s %s",
request.txn_id,
request.destination,
MAX_RESPONSE_SIZE,
request.method,
request.uri.decode("ascii"),
)
raise RequestSendFailed(e, can_retry=False) from e
except ValueError as e:
# The JSON content was invalid.
logger.warning(
......@@ -218,6 +237,18 @@ async def _handle_json_response(
return body
class BinaryIOWrapper:
"""A wrapper for a TextIO which converts from bytes on the fly."""
def __init__(self, file: typing.TextIO, encoding="utf-8", errors="strict"):
self.decoder = codecs.getincrementaldecoder(encoding)(errors)
self.file = file
def write(self, b: Union[bytes, bytearray]) -> int:
self.file.write(self.decoder.decode(b))
return len(b)
class MatrixFederationHttpClient:
"""HTTP client used to talk to other homeservers over the federation
protocol. Send client certificates and signs requests.
......
......@@ -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)
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