diff --git a/synapse/http/client.py b/synapse/http/client.py
index e5b13593f2..df7730078f 100644
--- a/synapse/http/client.py
+++ b/synapse/http/client.py
@@ -125,7 +125,7 @@ def _make_scheduler(reactor):
return _scheduler
-class IPBlacklistingResolver:
+class _IPBlacklistingResolver:
"""
A proxy for reactor.nameResolver which only produces non-blacklisted IP
addresses, preventing DNS rebinding attacks on URL preview.
@@ -199,6 +199,35 @@ class IPBlacklistingResolver:
return r
+@implementer(IReactorPluggableNameResolver)
+class BlacklistingReactorWrapper:
+ """
+ A Reactor wrapper which will prevent DNS resolution to blacklisted IP
+ addresses, to prevent DNS rebinding.
+ """
+
+ def __init__(
+ self,
+ reactor: IReactorPluggableNameResolver,
+ ip_whitelist: Optional[IPSet],
+ ip_blacklist: IPSet,
+ ):
+ self._reactor = reactor
+
+ # We need to use a DNS resolver which filters out blacklisted IP
+ # addresses, to prevent DNS rebinding.
+ self._nameResolver = _IPBlacklistingResolver(
+ self._reactor, ip_whitelist, ip_blacklist
+ )
+
+ def __getattr__(self, attr: str) -> Any:
+ # Passthrough to the real reactor except for the DNS resolver.
+ if attr == "nameResolver":
+ return self._nameResolver
+ else:
+ return getattr(self._reactor, attr)
+
+
class BlacklistingAgentWrapper(Agent):
"""
An Agent wrapper which will prevent access to IP addresses being accessed
@@ -292,22 +321,11 @@ class SimpleHttpClient:
self.user_agent = self.user_agent.encode("ascii")
if self._ip_blacklist:
- real_reactor = hs.get_reactor()
# If we have an IP blacklist, we need to use a DNS resolver which
# filters out blacklisted IP addresses, to prevent DNS rebinding.
- nameResolver = IPBlacklistingResolver(
- real_reactor, self._ip_whitelist, self._ip_blacklist
+ self.reactor = BlacklistingReactorWrapper(
+ hs.get_reactor(), self._ip_whitelist, self._ip_blacklist
)
-
- @implementer(IReactorPluggableNameResolver)
- class Reactor:
- def __getattr__(_self, attr):
- if attr == "nameResolver":
- return nameResolver
- else:
- return getattr(real_reactor, attr)
-
- self.reactor = Reactor()
else:
self.reactor = hs.get_reactor()
|
