From 33f469ba19586bbafa0cf2c7d7c35463bdab87eb Mon Sep 17 00:00:00 2001
From: Richard van der Hoff <richard@matrix.org>
Date: Tue, 1 May 2018 16:19:39 +0100
Subject: [PATCH] Apply some limits to depth to counter abuse
* When creating a new event, cap its depth to 2^63 - 1
* When receiving events, reject any without a sensible depth
As per https://docs.google.com/document/d/1I3fi2S-XnpO45qrpCsowZv8P8dHcNZ4fsBsbOW7KABI
---
synapse/api/constants.py | 3 +++
synapse/federation/federation_base.py | 21 ++++++++++++++++++---
synapse/handlers/message.py | 6 +++++-
3 files changed, 26 insertions(+), 4 deletions(-)
diff --git a/synapse/api/constants.py b/synapse/api/constants.py
index 489efb7f86..5baba43966 100644
--- a/synapse/api/constants.py
+++ b/synapse/api/constants.py
@@ -16,6 +16,9 @@
"""Contains constants from the specification."""
+# the "depth" field on events is limited to 2**63 - 1
+MAX_DEPTH = 2**63 - 1
+
class Membership(object):
diff --git a/synapse/federation/federation_base.py b/synapse/federation/federation_base.py
index 79eaa31031..4cc98a3fe8 100644
--- a/synapse/federation/federation_base.py
+++ b/synapse/federation/federation_base.py
@@ -14,7 +14,10 @@
# limitations under the License.
import logging
-from synapse.api.errors import SynapseError
+import six
+
+from synapse.api.constants import MAX_DEPTH
+from synapse.api.errors import SynapseError, Codes
from synapse.crypto.event_signing import check_event_content_hash
from synapse.events import FrozenEvent
from synapse.events.utils import prune_event
@@ -190,11 +193,23 @@ def event_from_pdu_json(pdu_json, outlier=False):
FrozenEvent
Raises:
- SynapseError: if the pdu is missing required fields
+ SynapseError: if the pdu is missing required fields or is otherwise
+ not a valid matrix event
"""
# we could probably enforce a bunch of other fields here (room_id, sender,
# origin, etc etc)
- assert_params_in_request(pdu_json, ('event_id', 'type'))
+ assert_params_in_request(pdu_json, ('event_id', 'type', 'depth'))
+
+ depth = pdu_json['depth']
+ if not isinstance(depth, six.integer_types):
+ raise SynapseError(400, "Depth %r not an intger" % (depth, ),
+ Codes.BAD_JSON)
+
+ if depth < 0:
+ raise SynapseError(400, "Depth too small", Codes.BAD_JSON)
+ elif depth > MAX_DEPTH:
+ raise SynapseError(400, "Depth too large", Codes.BAD_JSON)
+
event = FrozenEvent(
pdu_json
)
diff --git a/synapse/handlers/message.py b/synapse/handlers/message.py
index 21628a8540..53beb2b9ab 100644
--- a/synapse/handlers/message.py
+++ b/synapse/handlers/message.py
@@ -16,7 +16,7 @@
from twisted.internet import defer, reactor
from twisted.python.failure import Failure
-from synapse.api.constants import EventTypes, Membership
+from synapse.api.constants import EventTypes, Membership, MAX_DEPTH
from synapse.api.errors import AuthError, Codes, SynapseError
from synapse.crypto.event_signing import add_hashes_and_signatures
from synapse.events.utils import serialize_event
@@ -624,6 +624,10 @@ class EventCreationHandler(object):
if prev_events_and_hashes:
depth = max([d for _, _, d in prev_events_and_hashes]) + 1
+ # we cap depth of generated events, to ensure that they are not
+ # rejected by other servers (and so that they can be persisted in
+ # the db)
+ depth = min(depth, MAX_DEPTH)
else:
depth = 1
--
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