341 lines
13 KiB
Python
341 lines
13 KiB
Python
# Copyright 2019 The Matrix.org Foundation C.I.C.
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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import logging
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from typing import TYPE_CHECKING, Any, Awaitable, Callable, List, Optional, Tuple
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from synapse.api.errors import SynapseError
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from synapse.events import EventBase
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from synapse.events.snapshot import EventContext
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from synapse.types import Requester, StateMap
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from synapse.util.async_helpers import maybe_awaitable
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if TYPE_CHECKING:
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from synapse.server import HomeServer
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logger = logging.getLogger(__name__)
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CHECK_EVENT_ALLOWED_CALLBACK = Callable[
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[EventBase, StateMap[EventBase]], Awaitable[Tuple[bool, Optional[dict]]]
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]
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ON_CREATE_ROOM_CALLBACK = Callable[[Requester, dict, bool], Awaitable]
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CHECK_THREEPID_CAN_BE_INVITED_CALLBACK = Callable[
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[str, str, StateMap[EventBase]], Awaitable[bool]
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]
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CHECK_VISIBILITY_CAN_BE_MODIFIED_CALLBACK = Callable[
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[str, StateMap[EventBase], str], Awaitable[bool]
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]
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def load_legacy_third_party_event_rules(hs: "HomeServer") -> None:
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"""Wrapper that loads a third party event rules module configured using the old
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configuration, and registers the hooks they implement.
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"""
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if hs.config.thirdpartyrules.third_party_event_rules is None:
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return
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module, config = hs.config.thirdpartyrules.third_party_event_rules
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api = hs.get_module_api()
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third_party_rules = module(config=config, module_api=api)
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# The known hooks. If a module implements a method which name appears in this set,
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# we'll want to register it.
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third_party_event_rules_methods = {
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"check_event_allowed",
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"on_create_room",
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"check_threepid_can_be_invited",
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"check_visibility_can_be_modified",
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}
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def async_wrapper(f: Optional[Callable]) -> Optional[Callable[..., Awaitable]]:
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# f might be None if the callback isn't implemented by the module. In this
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# case we don't want to register a callback at all so we return None.
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if f is None:
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return None
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# We return a separate wrapper for these methods because, in order to wrap them
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# correctly, we need to await its result. Therefore it doesn't make a lot of
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# sense to make it go through the run() wrapper.
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if f.__name__ == "check_event_allowed":
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# We need to wrap check_event_allowed because its old form would return either
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# a boolean or a dict, but now we want to return the dict separately from the
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# boolean.
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async def wrap_check_event_allowed(
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event: EventBase,
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state_events: StateMap[EventBase],
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) -> Tuple[bool, Optional[dict]]:
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# Assertion required because mypy can't prove we won't change
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# `f` back to `None`. See
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# https://mypy.readthedocs.io/en/latest/common_issues.html#narrowing-and-inner-functions
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assert f is not None
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res = await f(event, state_events)
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if isinstance(res, dict):
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return True, res
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else:
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return res, None
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return wrap_check_event_allowed
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if f.__name__ == "on_create_room":
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# We need to wrap on_create_room because its old form would return a boolean
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# if the room creation is denied, but now we just want it to raise an
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# exception.
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async def wrap_on_create_room(
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requester: Requester, config: dict, is_requester_admin: bool
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) -> None:
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# Assertion required because mypy can't prove we won't change
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# `f` back to `None`. See
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# https://mypy.readthedocs.io/en/latest/common_issues.html#narrowing-and-inner-functions
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assert f is not None
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res = await f(requester, config, is_requester_admin)
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if res is False:
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raise SynapseError(
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403,
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"Room creation forbidden with these parameters",
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)
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return wrap_on_create_room
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def run(*args: Any, **kwargs: Any) -> Awaitable:
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# Assertion required because mypy can't prove we won't change `f`
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# back to `None`. See
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# https://mypy.readthedocs.io/en/latest/common_issues.html#narrowing-and-inner-functions
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assert f is not None
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return maybe_awaitable(f(*args, **kwargs))
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return run
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# Register the hooks through the module API.
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hooks = {
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hook: async_wrapper(getattr(third_party_rules, hook, None))
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for hook in third_party_event_rules_methods
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}
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api.register_third_party_rules_callbacks(**hooks)
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class ThirdPartyEventRules:
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"""Allows server admins to provide a Python module implementing an extra
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set of rules to apply when processing events.
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This is designed to help admins of closed federations with enforcing custom
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behaviours.
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"""
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def __init__(self, hs: "HomeServer"):
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self.third_party_rules = None
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self.store = hs.get_datastore()
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self._check_event_allowed_callbacks: List[CHECK_EVENT_ALLOWED_CALLBACK] = []
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self._on_create_room_callbacks: List[ON_CREATE_ROOM_CALLBACK] = []
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self._check_threepid_can_be_invited_callbacks: List[
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CHECK_THREEPID_CAN_BE_INVITED_CALLBACK
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] = []
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self._check_visibility_can_be_modified_callbacks: List[
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CHECK_VISIBILITY_CAN_BE_MODIFIED_CALLBACK
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] = []
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def register_third_party_rules_callbacks(
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self,
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check_event_allowed: Optional[CHECK_EVENT_ALLOWED_CALLBACK] = None,
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on_create_room: Optional[ON_CREATE_ROOM_CALLBACK] = None,
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check_threepid_can_be_invited: Optional[
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CHECK_THREEPID_CAN_BE_INVITED_CALLBACK
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] = None,
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check_visibility_can_be_modified: Optional[
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CHECK_VISIBILITY_CAN_BE_MODIFIED_CALLBACK
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] = None,
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) -> None:
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"""Register callbacks from modules for each hook."""
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if check_event_allowed is not None:
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self._check_event_allowed_callbacks.append(check_event_allowed)
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if on_create_room is not None:
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self._on_create_room_callbacks.append(on_create_room)
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if check_threepid_can_be_invited is not None:
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self._check_threepid_can_be_invited_callbacks.append(
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check_threepid_can_be_invited,
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)
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if check_visibility_can_be_modified is not None:
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self._check_visibility_can_be_modified_callbacks.append(
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check_visibility_can_be_modified,
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)
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async def check_event_allowed(
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self, event: EventBase, context: EventContext
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) -> Tuple[bool, Optional[dict]]:
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"""Check if a provided event should be allowed in the given context.
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The module can return:
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* True: the event is allowed.
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* False: the event is not allowed, and should be rejected with M_FORBIDDEN.
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If the event is allowed, the module can also return a dictionary to use as a
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replacement for the event.
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Args:
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event: The event to be checked.
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context: The context of the event.
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Returns:
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The result from the ThirdPartyRules module, as above.
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"""
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# Bail out early without hitting the store if we don't have any callbacks to run.
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if len(self._check_event_allowed_callbacks) == 0:
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return True, None
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prev_state_ids = await context.get_prev_state_ids()
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# Retrieve the state events from the database.
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events = await self.store.get_events(prev_state_ids.values())
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state_events = {(ev.type, ev.state_key): ev for ev in events.values()}
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# Ensure that the event is frozen, to make sure that the module is not tempted
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# to try to modify it. Any attempt to modify it at this point will invalidate
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# the hashes and signatures.
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event.freeze()
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for callback in self._check_event_allowed_callbacks:
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try:
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res, replacement_data = await callback(event, state_events)
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except SynapseError as e:
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# FIXME: Being able to throw SynapseErrors is relied upon by
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# some modules. PR #10386 accidentally broke this ability.
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# That said, we aren't keen on exposing this implementation detail
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# to modules and we should one day have a proper way to do what
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# is wanted.
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# This module callback needs a rework so that hacks such as
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# this one are not necessary.
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raise e
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except Exception as e:
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logger.warning("Failed to run module API callback %s: %s", callback, e)
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continue
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# Return if the event shouldn't be allowed or if the module came up with a
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# replacement dict for the event.
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if res is False:
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return res, None
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elif isinstance(replacement_data, dict):
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return True, replacement_data
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return True, None
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async def on_create_room(
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self, requester: Requester, config: dict, is_requester_admin: bool
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) -> None:
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"""Intercept requests to create room to maybe deny it (via an exception) or
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update the request config.
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Args:
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requester
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config: The creation config from the client.
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is_requester_admin: If the requester is an admin
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"""
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for callback in self._on_create_room_callbacks:
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try:
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await callback(requester, config, is_requester_admin)
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except Exception as e:
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# Don't silence the errors raised by this callback since we expect it to
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# raise an exception to deny the creation of the room; instead make sure
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# it's a SynapseError we can send to clients.
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if not isinstance(e, SynapseError):
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e = SynapseError(
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403, "Room creation forbidden with these parameters"
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)
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raise e
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async def check_threepid_can_be_invited(
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self, medium: str, address: str, room_id: str
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) -> bool:
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"""Check if a provided 3PID can be invited in the given room.
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Args:
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medium: The 3PID's medium.
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address: The 3PID's address.
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room_id: The room we want to invite the threepid to.
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Returns:
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True if the 3PID can be invited, False if not.
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"""
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# Bail out early without hitting the store if we don't have any callbacks to run.
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if len(self._check_threepid_can_be_invited_callbacks) == 0:
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return True
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state_events = await self._get_state_map_for_room(room_id)
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for callback in self._check_threepid_can_be_invited_callbacks:
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try:
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if await callback(medium, address, state_events) is False:
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return False
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except Exception as e:
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logger.warning("Failed to run module API callback %s: %s", callback, e)
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return True
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async def check_visibility_can_be_modified(
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self, room_id: str, new_visibility: str
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) -> bool:
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"""Check if a room is allowed to be published to, or removed from, the public room
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list.
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Args:
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room_id: The ID of the room.
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new_visibility: The new visibility state. Either "public" or "private".
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Returns:
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True if the room's visibility can be modified, False if not.
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"""
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# Bail out early without hitting the store if we don't have any callback
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if len(self._check_visibility_can_be_modified_callbacks) == 0:
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return True
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state_events = await self._get_state_map_for_room(room_id)
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for callback in self._check_visibility_can_be_modified_callbacks:
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try:
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if await callback(room_id, state_events, new_visibility) is False:
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return False
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except Exception as e:
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logger.warning("Failed to run module API callback %s: %s", callback, e)
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return True
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async def _get_state_map_for_room(self, room_id: str) -> StateMap[EventBase]:
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"""Given a room ID, return the state events of that room.
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Args:
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room_id: The ID of the room.
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Returns:
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A dict mapping (event type, state key) to state event.
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"""
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state_ids = await self.store.get_filtered_current_state_ids(room_id)
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room_state_events = await self.store.get_events(state_ids.values())
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state_events = {}
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for key, event_id in state_ids.items():
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state_events[key] = room_state_events[event_id]
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return state_events
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