Cannot send new events into rooms with floating-point (and stringy?) power levels

[DMRobertson]

Internal users: https://sentry.tools.element.io/organizations/element/issues/34032/?project=2&query=is%3Aunresolved&sort=freq&statsPeriod=14d

Sentry's report is terse here: it does not include local vars from the call stack.

Failed handle request via "RoomSendEventRestServlet": "<XForwardedForRequest at 0x7f8348f30f40 method='PUT' uri='/_matrix/client/r0/rooms/<room ID>/send/m.room.encrypted/<txn ID>' clientproto='HTTP/1.1' site='12101'>"

TypeError: argument 'notification_power_levels': 'float' object cannot be interpreted as an integer
  File "/home/synapse/src/synapse/http/server.py", line 306, in _async_render_wrapper
  File "/home/synapse/src/synapse/http/server.py", line 512, in _async_render
  File "/home/synapse/src/synapse/rest/client/room.py", line 353, in on_POST
  File "/home/synapse/src/synapse/handlers/message.py", line 1020, in create_and_send_nonmember_event
  File "/home/synapse/src/synapse/util/metrics.py", line 113, in measured_func
  File "/home/synapse/src/synapse/handlers/message.py", line 1382, in handle_new_client_event
  File "/home/synapse/env-pyston-poetry/lib/python3.8-pyston2.3/site-packages/twisted/internet/defer.py", line 1660, in _inlineCallbacks
  File "/home/synapse/src/synapse/handlers/message.py", line 1436, in _persist_events
  File "/home/synapse/src/synapse/util/metrics.py", line 113, in measured_func
  File "/home/synapse/src/synapse/push/bulk_push_rule_evaluator.py", line 292, in action_for_event_by_user

The deepest call is

synapse/synapse/push/bulk_push_rule_evaluator.py

Lines 292 to 299 in b4ec4f5

	evaluator = PushRuleEvaluator(
	_flatten_dict(event),
	room_member_count,
	sender_power_level,
	power_levels.get("notifications", {}),
	relations,
	self._relations_match_enabled,
	)

which invokes the new Rust mechanism for push stuff:

synapse/rust/src/push/evaluator.rs

Lines 64 to 90 in ebd9e2d

	#[pymethods]
	impl PushRuleEvaluator {
	/// Create a new `PushRuleEvaluator`. See struct docstring for details.
	#[new]
	pub fn py_new(
	flattened_keys: BTreeMap<String, String>,
	room_member_count: u64,
	sender_power_level: Option<i64>,
	notification_power_levels: BTreeMap<String, i64>,
	relations: BTreeMap<String, BTreeSet<(String, String)>>,
	relation_match_enabled: bool,
	) -> Result<Self, Error> {
	let body = flattened_keys
	.get("content.body")
	.cloned()
	.unwrap_or_default();
	Ok(PushRuleEvaluator {
	flattened_keys,
	body,
	room_member_count,
	notification_power_levels,
	relations,
	relation_match_enabled,
	sender_power_level,
	})
	}

I am guessing that

• the error message 'float' object cannot be interpreted as an integer comes from Py03's translation layer. (Implement push rule evaluation in Rust. #13838)
• the power levels event used in that room has floating power levels (and therefore is bogus, but not prohibited until room v10)
• people are unable to send messages in that room from Synapse if they believe that power levels event to be in the current state

Will investigate a little more.

[DMRobertson]

matrix=> select json::json->'content'->'notifications' from current_state_events AS cse join event_json using(event_id) where cse.room_id = '<ROOM ID>' and cse.type = 'm.room.power_levels';
    ?column?    
════════════════
 {"room":100.0}
(1 row)

Right. Well that's not good.

[DMRobertson]

The event in question was created at 2020-12-29 08:52:34+00 according to its origin_server_ts so MSC3667 doesn't apply.

We now check that the power level values are integers in sufficiently new rooms.

synapse/synapse/event_auth.py

Lines 783 to 807 in c2fe48a

	# Reject events with stringy power levels if required by room version
	if (
	event.type == EventTypes.PowerLevels
	and room_version_obj.msc3667_int_only_power_levels
	):
	for k, v in event.content.items():
	if k in {
	"users_default",
	"events_default",
	"state_default",
	"ban",
	"redact",
	"kick",
	"invite",
	}:
	if not isinstance(v, int):
	raise SynapseError(400, f"{v!r} must be an integer.")
	if k in {"events", "notifications", "users"}:
	if not isinstance(v, dict) or not all(
	isinstance(v, int) for v in v.values()
	):
	raise SynapseError(
	400,
	f"{v!r} must be a dict wherein all the values are integers.",
	)

[DMRobertson]

No idea how we even got floats in the power levels content in the first place, given that

synapse/synapse/events/utils.py

Lines 662 to 664 in 06df5d4

	elif isinstance(value, float):
	# Note that Infinity, -Infinity, and NaN are also considered floats.
	raise SynapseError(400, "Bad JSON value: float", Codes.BAD_JSON)

exists. But maybe it didn't at the time.

[richvdh]

No idea how we even got floats in the power levels content in the first place, given that

synapse/synapse/events/utils.py

Lines 662 to 664 in 06df5d4

	elif isinstance(value, float):
	# Note that Infinity, -Infinity, and NaN are also considered floats.
	raise SynapseError(400, "Bad JSON value: float", Codes.BAD_JSON)

exists. But maybe it didn't at the time.

Note that this is only enforced (at least over federation) for newer room versions.

[DMRobertson]

Merged into develop in 44741aa.