diff --git a/synapse/federation/federation_base.py b/synapse/federation/federation_base.py
index 5be8e66fb8..61782ae1c0 100644
--- a/synapse/federation/federation_base.py
+++ b/synapse/federation/federation_base.py
@@ -143,11 +143,31 @@ class FederationBase(object):
def callback(_, pdu):
with logcontext.PreserveLoggingContext(ctx):
if not check_event_content_hash(pdu):
- logger.warn(
- "Event content has been tampered, redacting %s: %s",
- pdu.event_id, pdu.get_pdu_json()
- )
- return prune_event(pdu)
+ # let's try to distinguish between failures because the event was
+ # redacted (which are somewhat expected) vs actual ball-tampering
+ # incidents.
+ #
+ # This is just a heuristic, so we just assume that if the keys are
+ # about the same between the redacted and received events, then the
+ # received event was probably a redacted copy (but we then use our
+ # *actual* redacted copy to be on the safe side.)
+ redacted_event = prune_event(pdu)
+ if (
+ set(six.iterkeys(redacted_event)) == set(six.iterkeys(pdu)) and
+ set(six.iterkeys(redacted_event.content))
+ == set(six.iterkeys(pdu.content))
+ ):
+ logger.info(
+ "Event %s seems to have been redacted; using our redacted "
+ "copy",
+ pdu.event_id,
+ )
+ else:
+ logger.warning(
+ "Event %s content has been tampered, redacting",
+ pdu.event_id, pdu.get_pdu_json(),
+ )
+ return redacted_event
if self.spam_checker.check_event_for_spam(pdu):
logger.warn(
@@ -162,8 +182,8 @@ class FederationBase(object):
failure.trap(SynapseError)
with logcontext.PreserveLoggingContext(ctx):
logger.warn(
- "Signature check failed for %s",
- pdu.event_id,
+ "Signature check failed for %s: %s",
+ pdu.event_id, failure.getErrorMessage(),
)
return failure
diff --git a/synapse/storage/keys.py b/synapse/storage/keys.py
index f547977600..a1331c1a61 100644
--- a/synapse/storage/keys.py
+++ b/synapse/storage/keys.py
@@ -134,6 +134,7 @@ class KeyStore(SQLBaseStore):
"""
key_id = "%s:%s" % (verify_key.alg, verify_key.version)
+ # XXX fix this to not need a lock (#3819)
def _txn(txn):
self._simple_upsert_txn(
txn,
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