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Correctly ratelimit invites when creating a room (#9968)

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* Correctly ratelimit invites when creating a room

Also allow ratelimiting for more than one action at a time.
This commit is contained in:
Brendan Abolivier 2021-05-12 16:05:28 +02:00 committed by GitHub
parent 7562d887e1
commit a683028d81
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6 changed files with 157 additions and 12 deletions
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1
changelog.d/9968.bugfix Normal file
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@ -0,0 +1 @@
Fix a bug introduced in v1.27.0 preventing users and appservices exempt from ratelimiting from creating rooms with many invitees.

22
synapse/api/ratelimiting.py
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@ -57,6 +57,7 @@ class Ratelimiter:
rate_hz: Optional[float] = None,
burst_count: Optional[int] = None,
update: bool = True,
n_actions: int = 1,
_time_now_s: Optional[int] = None,
) -> Tuple[bool, float]:
"""Can the entity (e.g. user or IP address) perform the action?
@ -76,6 +77,9 @@ class Ratelimiter:
burst_count: How many actions that can be performed before being limited.
Overrides the value set during instantiation if set.
update: Whether to count this check as performing the action
n_actions: The number of times the user wants to do this action. If the user
cannot do all of the actions, the user's action count is not incremented
at all.
_time_now_s: The current time. Optional, defaults to the current time according
to self.clock. Only used by tests.
@ -124,17 +128,20 @@ class Ratelimiter:
time_delta = time_now_s - time_start
performed_count = action_count - time_delta * rate_hz
if performed_count < 0:
# Allow, reset back to count 1
allowed = True
performed_count = 0
time_start = time_now_s
action_count = 1.0
elif performed_count > burst_count - 1.0:
# This check would be easier read as performed_count + n_actions > burst_count,
# but performed_count might be a very precise float (with lots of numbers
# following the point) in which case Python might round it up when adding it to
# n_actions. Writing it this way ensures it doesn't happen.
if performed_count > burst_count - n_actions:
# Deny, we have exceeded our burst count
allowed = False
else:
# We haven't reached our limit yet
allowed = True
action_count += 1.0
action_count = performed_count + n_actions
if update:
self.actions[key] = (action_count, time_start, rate_hz)
@ -182,6 +189,7 @@ class Ratelimiter:
rate_hz: Optional[float] = None,
burst_count: Optional[int] = None,
update: bool = True,
n_actions: int = 1,
_time_now_s: Optional[int] = None,
):
"""Checks if an action can be performed. If not, raises a LimitExceededError
@ -201,6 +209,9 @@ class Ratelimiter:
burst_count: How many actions that can be performed before being limited.
Overrides the value set during instantiation if set.
update: Whether to count this check as performing the action
n_actions: The number of times the user wants to do this action. If the user
cannot do all of the actions, the user's action count is not incremented
at all.
_time_now_s: The current time. Optional, defaults to the current time according
to self.clock. Only used by tests.
@ -216,6 +227,7 @@ class Ratelimiter:
rate_hz=rate_hz,
burst_count=burst_count,
update=update,
n_actions=n_actions,
_time_now_s=time_now_s,
)

25
synapse/handlers/room.py
View file

@ -32,7 +32,14 @@ from synapse.api.constants import (
RoomCreationPreset,
RoomEncryptionAlgorithms,
)
from synapse.api.errors import AuthError, Codes, NotFoundError, StoreError, SynapseError
from synapse.api.errors import (
AuthError,
Codes,
LimitExceededError,
NotFoundError,
StoreError,
SynapseError,
)
from synapse.api.filtering import Filter
from synapse.api.room_versions import KNOWN_ROOM_VERSIONS, RoomVersion
from synapse.events import EventBase
@ -126,10 +133,6 @@ class RoomCreationHandler(BaseHandler):
self.third_party_event_rules = hs.get_third_party_event_rules()
self._invite_burst_count = (
hs.config.ratelimiting.rc_invites_per_room.burst_count
)
async def upgrade_room(
self, requester: Requester, old_room_id: str, new_version: RoomVersion
) -> str:
@ -676,7 +679,17 @@ class RoomCreationHandler(BaseHandler):
invite_3pid_list = []
invite_list = []
if len(invite_list) + len(invite_3pid_list) > self._invite_burst_count:
if invite_list or invite_3pid_list:
try:
# If there are invites in the request, see if the ratelimiting settings
# allow that number of invites to be sent from the current user.
await self.room_member_handler.ratelimit_multiple_invites(
requester,
room_id=None,
n_invites=len(invite_list) + len(invite_3pid_list),
update=False,
)
except LimitExceededError:
raise SynapseError(400, "Cannot invite so many users at once")
await self.event_creation_handler.assert_accepted_privacy_policy(requester)

25
synapse/handlers/room_member.py
View file

@ -163,6 +163,31 @@ class RoomMemberHandler(metaclass=abc.ABCMeta):
async def forget(self, user: UserID, room_id: str) -> None:
raise NotImplementedError()
async def ratelimit_multiple_invites(
self,
requester: Optional[Requester],
room_id: Optional[str],
n_invites: int,
update: bool = True,
):
"""Ratelimit more than one invite sent by the given requester in the given room.
Args:
requester: The requester sending the invites.
room_id: The room the invites are being sent in.
n_invites: The amount of invites to ratelimit for.
update: Whether to update the ratelimiter's cache.
Raises:
LimitExceededError: The requester can't send that many invites in the room.
"""
await self._invites_per_room_limiter.ratelimit(
requester,
room_id,
update=update,
n_actions=n_invites,
)
async def ratelimit_invite(
self,
requester: Optional[Requester],

57
tests/api/test_ratelimiting.py
View file

@ -230,3 +230,60 @@ class TestRatelimiter(unittest.HomeserverTestCase):
# Shouldn't raise
for _ in range(20):
self.get_success_or_raise(limiter.ratelimit(requester, _time_now_s=0))
def test_multiple_actions(self):
limiter = Ratelimiter(
store=self.hs.get_datastore(), clock=None, rate_hz=0.1, burst_count=3
)
# Test that 4 actions aren't allowed with a maximum burst of 3.
allowed, time_allowed = self.get_success_or_raise(
limiter.can_do_action(None, key="test_id", n_actions=4, _time_now_s=0)
)
self.assertFalse(allowed)
# Test that 3 actions are allowed with a maximum burst of 3.
allowed, time_allowed = self.get_success_or_raise(
limiter.can_do_action(None, key="test_id", n_actions=3, _time_now_s=0)
)
self.assertTrue(allowed)
self.assertEquals(10.0, time_allowed)
# Test that, after doing these 3 actions, we can't do any more action without
# waiting.
allowed, time_allowed = self.get_success_or_raise(
limiter.can_do_action(None, key="test_id", n_actions=1, _time_now_s=0)
)
self.assertFalse(allowed)
self.assertEquals(10.0, time_allowed)
# Test that after waiting we can do only 1 action.
allowed, time_allowed = self.get_success_or_raise(
limiter.can_do_action(
None,
key="test_id",
update=False,
n_actions=1,
_time_now_s=10,
)
)
self.assertTrue(allowed)
# The time allowed is the current time because we could still repeat the action
# once.
self.assertEquals(10.0, time_allowed)
allowed, time_allowed = self.get_success_or_raise(
limiter.can_do_action(None, key="test_id", n_actions=2, _time_now_s=10)
)
self.assertFalse(allowed)
# The time allowed doesn't change despite allowed being False because, while we
# don't allow 2 actions, we could still do 1.
self.assertEquals(10.0, time_allowed)
# Test that after waiting a bit more we can do 2 actions.
allowed, time_allowed = self.get_success_or_raise(
limiter.can_do_action(None, key="test_id", n_actions=2, _time_now_s=20)
)
self.assertTrue(allowed)
# The time allowed is the current time because we could still repeat the action
# once.
self.assertEquals(20.0, time_allowed)

37
tests/rest/client/v1/test_rooms.py
View file

@ -463,6 +463,43 @@ class RoomsCreateTestCase(RoomBase):
)
self.assertEquals(400, channel.code)
@unittest.override_config({"rc_invites": {"per_room": {"burst_count": 3}}})
def test_post_room_invitees_ratelimit(self):
"""Test that invites sent when creating a room are ratelimited by a RateLimiter,
which ratelimits them correctly, including by not limiting when the requester is
exempt from ratelimiting.
"""
# Build the request's content. We use local MXIDs because invites over federation
# are more difficult to mock.
content = json.dumps(
{
"invite": [
"@alice1:red",
"@alice2:red",
"@alice3:red",
"@alice4:red",
]
}
).encode("utf8")
# Test that the invites are correctly ratelimited.
channel = self.make_request("POST", "/createRoom", content)
self.assertEqual(400, channel.code)
self.assertEqual(
"Cannot invite so many users at once",
channel.json_body["error"],
)
# Add the current user to the ratelimit overrides, allowing them no ratelimiting.
self.get_success(
self.hs.get_datastore().set_ratelimit_for_user(self.user_id, 0, 0)
)
# Test that the invites aren't ratelimited anymore.
channel = self.make_request("POST", "/createRoom", content)
self.assertEqual(200, channel.code)
class RoomTopicTestCase(RoomBase):
""" Tests /rooms/$room_id/topic REST events. """