diff --git a/synapse/http/federation/well_known_resolver.py b/synapse/http/federation/well_known_resolver.py
index 5e08ef1664..b3b6dbcab0 100644
--- a/synapse/http/federation/well_known_resolver.py
+++ b/synapse/http/federation/well_known_resolver.py
@@ -15,17 +15,19 @@
import logging
import random
import time
+from io import BytesIO
from typing import Callable, Dict, Optional, Tuple
import attr
from twisted.internet import defer
from twisted.internet.interfaces import IReactorTime
-from twisted.web.client import RedirectAgent, readBody
+from twisted.web.client import RedirectAgent
from twisted.web.http import stringToDatetime
from twisted.web.http_headers import Headers
from twisted.web.iweb import IAgent, IResponse
+from synapse.http.client import BodyExceededMaxSize, read_body_with_max_size
from synapse.logging.context import make_deferred_yieldable
from synapse.util import Clock, json_decoder
from synapse.util.caches.ttlcache import TTLCache
@@ -53,6 +55,9 @@ WELL_KNOWN_MAX_CACHE_PERIOD = 48 * 3600
# lower bound for .well-known cache period
WELL_KNOWN_MIN_CACHE_PERIOD = 5 * 60
+# The maximum size (in bytes) to allow a well-known file to be.
+WELL_KNOWN_MAX_SIZE = 50 * 1024 # 50 KiB
+
# Attempt to refetch a cached well-known N% of the TTL before it expires.
# e.g. if set to 0.2 and we have a cached entry with a TTL of 5mins, then
# we'll start trying to refetch 1 minute before it expires.
@@ -229,6 +234,9 @@ class WellKnownResolver:
server_name: name of the server, from the requested url
retry: Whether to retry the request if it fails.
+ Raises:
+ _FetchWellKnownFailure if we fail to lookup a result
+
Returns:
Returns the response object and body. Response may be a non-200 response.
"""
@@ -250,7 +258,11 @@ class WellKnownResolver:
b"GET", uri, headers=Headers(headers)
)
)
- body = await make_deferred_yieldable(readBody(response))
+ body_stream = BytesIO()
+ await make_deferred_yieldable(
+ read_body_with_max_size(response, body_stream, WELL_KNOWN_MAX_SIZE)
+ )
+ body = body_stream.getvalue()
if 500 <= response.code < 600:
raise Exception("Non-200 response %s" % (response.code,))
@@ -259,6 +271,15 @@ class WellKnownResolver:
except defer.CancelledError:
# Bail if we've been cancelled
raise
+ except BodyExceededMaxSize:
+ # If the well-known file was too large, do not keep attempting
+ # to download it, but consider it a temporary error.
+ logger.warning(
+ "Requested .well-known file for %s is too large > %r bytes",
+ server_name.decode("ascii"),
+ WELL_KNOWN_MAX_SIZE,
+ )
+ raise _FetchWellKnownFailure(temporary=True)
except Exception as e:
if not retry or i >= WELL_KNOWN_RETRY_ATTEMPTS:
logger.info("Error fetching %s: %s", uri_str, e)
|
