diff --git a/synapse/third_party_rules/access_rules.py b/synapse/third_party_rules/access_rules.py
new file mode 100644
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--- /dev/null
+++ b/synapse/third_party_rules/access_rules.py
@@ -0,0 +1,947 @@
+# -*- coding: utf-8 -*-
+# Copyright 2019 New Vector Ltd
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+import email.utils
+import logging
+from typing import Dict, List, Optional, Tuple
+
+from twisted.internet import defer
+
+from synapse.api.constants import EventTypes, JoinRules, Membership, RoomCreationPreset
+from synapse.api.errors import SynapseError
+from synapse.config._base import ConfigError
+from synapse.events import EventBase
+from synapse.module_api import ModuleApi
+from synapse.types import Requester, StateMap, UserID, get_domain_from_id
+
+logger = logging.getLogger(__name__)
+
+ACCESS_RULES_TYPE = "im.vector.room.access_rules"
+
+
+class AccessRules:
+ DIRECT = "direct"
+ RESTRICTED = "restricted"
+ UNRESTRICTED = "unrestricted"
+
+
+VALID_ACCESS_RULES = (
+ AccessRules.DIRECT,
+ AccessRules.RESTRICTED,
+ AccessRules.UNRESTRICTED,
+)
+
+# Rules to which we need to apply the power levels restrictions.
+#
+# These are all of the rules that neither:
+# * forbid users from joining based on a server blacklist (which means that there
+# is no need to apply power level restrictions), nor
+# * target direct chats (since we allow both users to be room admins in this case).
+#
+# The power-level restrictions, when they are applied, prevent the following:
+# * the default power level for users (users_default) being set to anything other than 0.
+# * a non-default power level being assigned to any user which would be forbidden from
+# joining a restricted room.
+RULES_WITH_RESTRICTED_POWER_LEVELS = (AccessRules.UNRESTRICTED,)
+
+
+class RoomAccessRules(object):
+ """Implementation of the ThirdPartyEventRules module API that allows federation admins
+ to define custom rules for specific events and actions.
+ Implements the custom behaviour for the "im.vector.room.access_rules" state event.
+
+ Takes a config in the format:
+
+ third_party_event_rules:
+ module: third_party_rules.RoomAccessRules
+ config:
+ # List of domains (server names) that can't be invited to rooms if the
+ # "restricted" rule is set. Defaults to an empty list.
+ domains_forbidden_when_restricted: []
+
+ # Identity server to use when checking the HS an email address belongs to
+ # using the /info endpoint. Required.
+ id_server: "vector.im"
+
+ Don't forget to consider if you can invite users from your own domain.
+ """
+
+ def __init__(
+ self, config: Dict, module_api: ModuleApi,
+ ):
+ self.id_server = config["id_server"]
+ self.module_api = module_api
+
+ self.domains_forbidden_when_restricted = config.get(
+ "domains_forbidden_when_restricted", []
+ )
+
+ @staticmethod
+ def parse_config(config: Dict) -> Dict:
+ """Parses and validates the options specified in the homeserver config.
+
+ Args:
+ config: The config dict.
+
+ Returns:
+ The config dict.
+
+ Raises:
+ ConfigError: If there was an issue with the provided module configuration.
+ """
+ if "id_server" not in config:
+ raise ConfigError("No IS for event rules TchapEventRules")
+
+ return config
+
+ async def on_create_room(
+ self, requester: Requester, config: Dict, is_requester_admin: bool,
+ ) -> bool:
+ """Implements synapse.events.ThirdPartyEventRules.on_create_room.
+
+ Checks if a im.vector.room.access_rules event is being set during room creation.
+ If yes, make sure the event is correct. Otherwise, append an event with the
+ default rule to the initial state.
+
+ Checks if a m.rooms.power_levels event is being set during room creation.
+ If yes, make sure the event is allowed. Otherwise, set power_level_content_override
+ in the config dict to our modified version of the default room power levels.
+
+ Args:
+ requester: The user who is making the createRoom request.
+ config: The createRoom config dict provided by the user.
+ is_requester_admin: Whether the requester is a Synapse admin.
+
+ Returns:
+ Whether the request is allowed.
+
+ Raises:
+ SynapseError: If the createRoom config dict is invalid or its contents blocked.
+ """
+ is_direct = config.get("is_direct")
+ preset = config.get("preset")
+ access_rule = None
+ join_rule = None
+
+ # If there's a rules event in the initial state, check if it complies with the
+ # spec for im.vector.room.access_rules and deny the request if not.
+ for event in config.get("initial_state", []):
+ if event["type"] == ACCESS_RULES_TYPE:
+ access_rule = event["content"].get("rule")
+
+ # Make sure the event has a valid content.
+ if access_rule is None:
+ raise SynapseError(400, "Invalid access rule")
+
+ # Make sure the rule name is valid.
+ if access_rule not in VALID_ACCESS_RULES:
+ raise SynapseError(400, "Invalid access rule")
+
+ if (is_direct and access_rule != AccessRules.DIRECT) or (
+ access_rule == AccessRules.DIRECT and not is_direct
+ ):
+ raise SynapseError(400, "Invalid access rule")
+
+ if event["type"] == EventTypes.JoinRules:
+ join_rule = event["content"].get("join_rule")
+
+ if access_rule is None:
+ # If there's no access rules event in the initial state, create one with the
+ # default setting.
+ if is_direct:
+ default_rule = AccessRules.DIRECT
+ else:
+ # If the default value for non-direct chat changes, we should make another
+ # case here for rooms created with either a "public" join_rule or the
+ # "public_chat" preset to make sure those keep defaulting to "restricted"
+ default_rule = AccessRules.RESTRICTED
+
+ if not config.get("initial_state"):
+ config["initial_state"] = []
+
+ config["initial_state"].append(
+ {
+ "type": ACCESS_RULES_TYPE,
+ "state_key": "",
+ "content": {"rule": default_rule},
+ }
+ )
+
+ access_rule = default_rule
+
+ # Check that the preset in use is compatible with the access rule, whether it's
+ # user-defined or the default.
+ #
+ # Direct rooms may not have their join_rules set to JoinRules.PUBLIC.
+ if (
+ join_rule == JoinRules.PUBLIC or preset == RoomCreationPreset.PUBLIC_CHAT
+ ) and access_rule == AccessRules.DIRECT:
+ raise SynapseError(400, "Invalid access rule")
+
+ # Check if the creator can override values for the power levels.
+ allowed = self._is_power_level_content_allowed(
+ config.get("power_level_content_override", {}), access_rule
+ )
+ if not allowed:
+ raise SynapseError(400, "Invalid power levels content override")
+
+ use_default_power_levels = True
+ if config.get("power_level_content_override"):
+ use_default_power_levels = False
+
+ # Second loop for events we need to know the current rule to process.
+ for event in config.get("initial_state", []):
+ if event["type"] == EventTypes.PowerLevels:
+ allowed = self._is_power_level_content_allowed(
+ event["content"], access_rule
+ )
+ if not allowed:
+ raise SynapseError(400, "Invalid power levels content")
+
+ use_default_power_levels = False
+
+ # If power levels were not overridden by the user, override with DINUM's preferred
+ # defaults instead
+ if use_default_power_levels:
+ config["power_level_content_override"] = self._get_default_power_levels(
+ requester.user.to_string()
+ )
+
+ return True
+
+ # If power levels are not overridden by the user during room creation, the following
+ # rules are used instead. Changes from Synapse's default power levels are noted.
+ #
+ # The same power levels are currently applied regardless of room preset.
+ @staticmethod
+ def _get_default_power_levels(user_id: str) -> Dict:
+ return {
+ "users": {user_id: 100},
+ "users_default": 0,
+ "events": {
+ EventTypes.Name: 50,
+ EventTypes.PowerLevels: 100,
+ EventTypes.RoomHistoryVisibility: 100,
+ EventTypes.CanonicalAlias: 50,
+ EventTypes.RoomAvatar: 50,
+ EventTypes.Tombstone: 100,
+ EventTypes.ServerACL: 100,
+ EventTypes.RoomEncryption: 100,
+ },
+ "events_default": 0,
+ "state_default": 100, # Admins should be the only ones to perform other tasks
+ "ban": 50,
+ "kick": 50,
+ "redact": 50,
+ "invite": 50, # All rooms should require mod to invite, even private
+ }
+
+ @defer.inlineCallbacks
+ def check_threepid_can_be_invited(
+ self, medium: str, address: str, state_events: StateMap[EventBase],
+ ) -> bool:
+ """Implements synapse.events.ThirdPartyEventRules.check_threepid_can_be_invited.
+
+ Check if a threepid can be invited to the room via a 3PID invite given the current
+ rules and the threepid's address, by retrieving the HS it's mapped to from the
+ configured identity server, and checking if we can invite users from it.
+
+ Args:
+ medium: The medium of the threepid.
+ address: The address of the threepid.
+ state_events: A dict mapping (event type, state key) to state event.
+ State events in the room the threepid is being invited to.
+
+ Returns:
+ Whether the threepid invite is allowed.
+ """
+ rule = self._get_rule_from_state(state_events)
+
+ if medium != "email":
+ return False
+
+ if rule != AccessRules.RESTRICTED:
+ # Only "restricted" requires filtering 3PID invites. We don't need to do
+ # anything for "direct" here, because only "restricted" requires filtering
+ # based on the HS the address is mapped to.
+ return True
+
+ parsed_address = email.utils.parseaddr(address)[1]
+ if parsed_address != address:
+ # Avoid reproducing the security issue described here:
+ # https://matrix.org/blog/2019/04/18/security-update-sydent-1-0-2
+ # It's probably not worth it but let's just be overly safe here.
+ return False
+
+ # Get the HS this address belongs to from the identity server.
+ res = yield self.module_api.http_client.get_json(
+ "https://%s/_matrix/identity/api/v1/info" % (self.id_server,),
+ {"medium": medium, "address": address},
+ )
+
+ # Look for a domain that's not forbidden from being invited.
+ if not res.get("hs"):
+ return False
+ if res.get("hs") in self.domains_forbidden_when_restricted:
+ return False
+
+ return True
+
+ async def check_event_allowed(
+ self, event: EventBase, state_events: StateMap[EventBase],
+ ) -> bool:
+ """Implements synapse.events.ThirdPartyEventRules.check_event_allowed.
+
+ Checks the event's type and the current rule and calls the right function to
+ determine whether the event can be allowed.
+
+ Args:
+ event: The event to check.
+ state_events: A dict mapping (event type, state key) to state event.
+ State events in the room the event originated from.
+
+ Returns:
+ True if the event can be allowed, False otherwise.
+ """
+ if event.type == ACCESS_RULES_TYPE:
+ return await self._on_rules_change(event, state_events)
+
+ # We need to know the rule to apply when processing the event types below.
+ rule = self._get_rule_from_state(state_events)
+
+ if event.type == EventTypes.PowerLevels:
+ return self._is_power_level_content_allowed(
+ event.content, rule, on_room_creation=False
+ )
+
+ if event.type == EventTypes.Member or event.type == EventTypes.ThirdPartyInvite:
+ return await self._on_membership_or_invite(event, rule, state_events)
+
+ if event.type == EventTypes.JoinRules:
+ return self._on_join_rule_change(event, rule)
+
+ if event.type == EventTypes.RoomAvatar:
+ return self._on_room_avatar_change(event, rule)
+
+ if event.type == EventTypes.Name:
+ return self._on_room_name_change(event, rule)
+
+ if event.type == EventTypes.Topic:
+ return self._on_room_topic_change(event, rule)
+
+ return True
+
+ async def check_visibility_can_be_modified(
+ self, room_id: str, state_events: StateMap[EventBase], new_visibility: str
+ ) -> bool:
+ """Implements
+ synapse.events.ThirdPartyEventRules.check_visibility_can_be_modified
+
+ Determines whether a room can be published, or removed from, the public room
+ list. A room is published if its visibility is set to "public". Otherwise,
+ its visibility is "private". A room with access rule other than "restricted"
+ may not be published.
+
+ Args:
+ room_id: The ID of the room.
+ state_events: A dict mapping (event type, state key) to state event.
+ State events in the room.
+ new_visibility: The new visibility state. Either "public" or "private".
+
+ Returns:
+ Whether the room is allowed to be published to, or removed from, the public
+ rooms directory.
+ """
+ # We need to know the rule to apply when processing the event types below.
+ rule = self._get_rule_from_state(state_events)
+
+ # Allow adding a room to the public rooms list only if it is restricted
+ if new_visibility == "public":
+ return rule == AccessRules.RESTRICTED
+
+ # By default a room is created as "restricted", meaning it is allowed to be
+ # published to the public rooms directory.
+ return True
+
+ async def _on_rules_change(
+ self, event: EventBase, state_events: StateMap[EventBase]
+ ):
+ """Checks whether an im.vector.room.access_rules event is forbidden or allowed.
+
+ Args:
+ event: The im.vector.room.access_rules event.
+ state_events: A dict mapping (event type, state key) to state event.
+ State events in the room before the event was sent.
+ Returns:
+ True if the event can be allowed, False otherwise.
+ """
+ new_rule = event.content.get("rule")
+
+ # Check for invalid values.
+ if new_rule not in VALID_ACCESS_RULES:
+ return False
+
+ # Make sure we don't apply "direct" if the room has more than two members.
+ if new_rule == AccessRules.DIRECT:
+ existing_members, threepid_tokens = self._get_members_and_tokens_from_state(
+ state_events
+ )
+
+ if len(existing_members) > 2 or len(threepid_tokens) > 1:
+ return False
+
+ if new_rule != AccessRules.RESTRICTED:
+ # Block this change if this room is currently listed in the public rooms
+ # directory
+ if await self.module_api.public_room_list_manager.room_is_in_public_room_list(
+ event.room_id
+ ):
+ return False
+
+ prev_rules_event = state_events.get((ACCESS_RULES_TYPE, ""))
+
+ # Now that we know the new rule doesn't break the "direct" case, we can allow any
+ # new rule in rooms that had none before.
+ if prev_rules_event is None:
+ return True
+
+ prev_rule = prev_rules_event.content.get("rule")
+
+ # Currently, we can only go from "restricted" to "unrestricted".
+ return (
+ prev_rule == AccessRules.RESTRICTED and new_rule == AccessRules.UNRESTRICTED
+ )
+
+ async def _on_membership_or_invite(
+ self, event: EventBase, rule: str, state_events: StateMap[EventBase],
+ ) -> bool:
+ """Applies the correct rule for incoming m.room.member and
+ m.room.third_party_invite events.
+
+ Args:
+ event: The event to check.
+ rule: The name of the rule to apply.
+ state_events: A dict mapping (event type, state key) to state event.
+ The state of the room before the event was sent.
+
+ Returns:
+ True if the event can be allowed, False otherwise.
+ """
+ if rule == AccessRules.RESTRICTED:
+ ret = self._on_membership_or_invite_restricted(event)
+ elif rule == AccessRules.UNRESTRICTED:
+ ret = self._on_membership_or_invite_unrestricted(event, state_events)
+ elif rule == AccessRules.DIRECT:
+ ret = self._on_membership_or_invite_direct(event, state_events)
+ else:
+ # We currently apply the default (restricted) if we don't know the rule, we
+ # might want to change that in the future.
+ ret = self._on_membership_or_invite_restricted(event)
+
+ if event.type == "m.room.member":
+ # If this is an admin leaving, and they are the last admin in the room,
+ # raise the power levels of the room so that the room is 'frozen'.
+ #
+ # We have to freeze the room by puppeting an admin user, which we can
+ # only do for local users
+ if (
+ self._is_local_user(event.sender)
+ and event.membership == Membership.LEAVE
+ ):
+ await self._freeze_room_if_last_admin_is_leaving(event, state_events)
+
+ return ret
+
+ async def _freeze_room_if_last_admin_is_leaving(
+ self, event: EventBase, state_events: StateMap[EventBase]
+ ):
+ power_level_state_event = state_events.get(
+ (EventTypes.PowerLevels, "")
+ ) # type: EventBase
+ if not power_level_state_event:
+ return
+ power_level_content = power_level_state_event.content
+
+ # Do some validation checks on the power level state event
+ if (
+ not isinstance(power_level_content, dict)
+ or "users" not in power_level_content
+ or not isinstance(power_level_content["users"], dict)
+ ):
+ # We can't use this power level event to determine whether the room should be
+ # frozen. Bail out.
+ return
+
+ user_id = event.get("sender")
+ if not user_id:
+ return
+
+ # Get every admin user defined in the room's state
+ admin_users = {
+ user
+ for user, power_level in power_level_content["users"].items()
+ if power_level >= 100
+ }
+
+ if user_id not in admin_users:
+ # This user is not an admin, ignore them
+ return
+
+ if any(
+ event_type == EventTypes.Member
+ and event.membership in [Membership.JOIN, Membership.INVITE]
+ and state_key in admin_users
+ and state_key != user_id
+ for (event_type, state_key), event in state_events.items()
+ ):
+ # There's another admin user in, or invited to, the room
+ return
+
+ # Freeze the room by raising the required power level to send events to 100
+ logger.info("Freezing room '%s'", event.room_id)
+
+ # Modify the existing power levels to raise all required types to 100
+ #
+ # This changes a power level state event's content from something like:
+ # {
+ # "redact": 50,
+ # "state_default": 50,
+ # "ban": 50,
+ # "notifications": {
+ # "room": 50
+ # },
+ # "events": {
+ # "m.room.avatar": 50,
+ # "m.room.encryption": 50,
+ # "m.room.canonical_alias": 50,
+ # "m.room.name": 50,
+ # "im.vector.modular.widgets": 50,
+ # "m.room.topic": 50,
+ # "m.room.tombstone": 50,
+ # "m.room.history_visibility": 100,
+ # "m.room.power_levels": 100
+ # },
+ # "users_default": 0,
+ # "events_default": 0,
+ # "users": {
+ # "@admin:example.com": 100,
+ # },
+ # "kick": 50,
+ # "invite": 0
+ # }
+ #
+ # to
+ #
+ # {
+ # "redact": 100,
+ # "state_default": 100,
+ # "ban": 100,
+ # "notifications": {
+ # "room": 50
+ # },
+ # "events": {}
+ # "users_default": 0,
+ # "events_default": 100,
+ # "users": {
+ # "@admin:example.com": 100,
+ # },
+ # "kick": 100,
+ # "invite": 100
+ # }
+ new_content = {}
+ for key, value in power_level_content.items():
+ # Do not change "users_default", as that key specifies the default power
+ # level of new users
+ if isinstance(value, int) and key != "users_default":
+ value = 100
+ new_content[key] = value
+
+ # Set some values in case they are missing from the original
+ # power levels event content
+ new_content.update(
+ {
+ # Clear out any special-cased event keys
+ "events": {},
+ # Ensure state_default and events_default keys exist and are 100.
+ # Otherwise a lower PL user could potentially send state events that
+ # aren't explicitly mentioned elsewhere in the power level dict
+ "state_default": 100,
+ "events_default": 100,
+ # Membership events default to 50 if they aren't present. Set them
+ # to 100 here, as they would be set to 100 if they were present anyways
+ "ban": 100,
+ "kick": 100,
+ "invite": 100,
+ "redact": 100,
+ }
+ )
+
+ await self.module_api.create_and_send_event_into_room(
+ {
+ "room_id": event.room_id,
+ "sender": user_id,
+ "type": EventTypes.PowerLevels,
+ "content": new_content,
+ "state_key": "",
+ }
+ )
+
+ def _on_membership_or_invite_restricted(self, event: EventBase) -> bool:
+ """Implements the checks and behaviour specified for the "restricted" rule.
+
+ "restricted" currently means that users can only invite users if their server is
+ included in a limited list of domains.
+
+ Args:
+ event: The event to check.
+
+ Returns:
+ True if the event can be allowed, False otherwise.
+ """
+ # We're not applying the rules on m.room.third_party_member events here because
+ # the filtering on threepids is done in check_threepid_can_be_invited, which is
+ # called before check_event_allowed.
+ if event.type == EventTypes.ThirdPartyInvite:
+ return True
+
+ # We only need to process "join" and "invite" memberships, in order to be backward
+ # compatible, e.g. if a user from a blacklisted server joined a restricted room
+ # before the rules started being enforced on the server, that user must be able to
+ # leave it.
+ if event.membership not in [Membership.JOIN, Membership.INVITE]:
+ return True
+
+ invitee_domain = get_domain_from_id(event.state_key)
+ return invitee_domain not in self.domains_forbidden_when_restricted
+
+ def _on_membership_or_invite_unrestricted(
+ self, event: EventBase, state_events: StateMap[EventBase]
+ ) -> bool:
+ """Implements the checks and behaviour specified for the "unrestricted" rule.
+
+ "unrestricted" currently means that forbidden users cannot join without an invite.
+
+ Returns:
+ True if the event can be allowed, False otherwise.
+ """
+ # If this is a join from a forbidden user and they don't have an invite to the
+ # room, then deny it
+ if event.type == EventTypes.Member and event.membership == Membership.JOIN:
+ # Check if this user is from a forbidden server
+ target_domain = get_domain_from_id(event.state_key)
+ if target_domain in self.domains_forbidden_when_restricted:
+ # If so, they'll need an invite to join this room. Check if one exists
+ if not self._user_is_invited_to_room(event.state_key, state_events):
+ return False
+
+ return True
+
+ def _on_membership_or_invite_direct(
+ self, event: EventBase, state_events: StateMap[EventBase],
+ ) -> bool:
+ """Implements the checks and behaviour specified for the "direct" rule.
+
+ "direct" currently means that no member is allowed apart from the two initial
+ members the room was created for (i.e. the room's creator and their first invitee).
+
+ Args:
+ event: The event to check.
+ state_events: A dict mapping (event type, state key) to state event.
+ The state of the room before the event was sent.
+
+ Returns:
+ True if the event can be allowed, False otherwise.
+ """
+ # Get the room memberships and 3PID invite tokens from the room's state.
+ existing_members, threepid_tokens = self._get_members_and_tokens_from_state(
+ state_events
+ )
+
+ # There should never be more than one 3PID invite in the room state: if the second
+ # original user came and left, and we're inviting them using their email address,
+ # given we know they have a Matrix account binded to the address (so they could
+ # join the first time), Synapse will successfully look it up before attempting to
+ # store an invite on the IS.
+ if len(threepid_tokens) == 1 and event.type == EventTypes.ThirdPartyInvite:
+ # If we already have a 3PID invite in flight, don't accept another one, unless
+ # the new one has the same invite token as its state key. This is because 3PID
+ # invite revocations must be allowed, and a revocation is basically a new 3PID
+ # invite event with an empty content and the same token as the invite it
+ # revokes.
+ return event.state_key in threepid_tokens
+
+ if len(existing_members) == 2:
+ # If the user was within the two initial user of the room, Synapse would have
+ # looked it up successfully and thus sent a m.room.member here instead of
+ # m.room.third_party_invite.
+ if event.type == EventTypes.ThirdPartyInvite:
+ return False
+
+ # We can only have m.room.member events here. The rule in this case is to only
+ # allow the event if its target is one of the initial two members in the room,
+ # i.e. the state key of one of the two m.room.member states in the room.
+ return event.state_key in existing_members
+
+ # We're alone in the room (and always have been) and there's one 3PID invite in
+ # flight.
+ if len(existing_members) == 1 and len(threepid_tokens) == 1:
+ # We can only have m.room.member events here. In this case, we can only allow
+ # the event if it's either a m.room.member from the joined user (we can assume
+ # that the only m.room.member event is a join otherwise we wouldn't be able to
+ # send an event to the room) or an an invite event which target is the invited
+ # user.
+ target = event.state_key
+ is_from_threepid_invite = self._is_invite_from_threepid(
+ event, threepid_tokens[0]
+ )
+ return is_from_threepid_invite or target == existing_members[0]
+
+ return True
+
+ def _is_power_level_content_allowed(
+ self, content: Dict, access_rule: str, on_room_creation: bool = True
+ ) -> bool:
+ """Check if a given power levels event is permitted under the given access rule.
+
+ It shouldn't be allowed if it either changes the default PL to a non-0 value or
+ gives a non-0 PL to a user that would have been forbidden from joining the room
+ under a more restrictive access rule.
+
+ Args:
+ content: The content of the m.room.power_levels event to check.
+ access_rule: The access rule in place in this room.
+ on_room_creation: True if this call is happening during a room's
+ creation, False otherwise.
+
+ Returns:
+ Whether the content of the power levels event is valid.
+ """
+ # Only enforce these rules during room creation
+ #
+ # We want to allow admins to modify or fix the power levels in a room if they
+ # have a special circumstance, but still want to encourage a certain pattern during
+ # room creation.
+ if on_room_creation:
+ # If invite requirements are <PL50
+ if content.get("invite", 50) < 50:
+ return False
+
+ # If "other" state requirements are <PL100
+ if content.get("state_default", 100) < 100:
+ return False
+
+ # Check if we need to apply the restrictions with the current rule.
+ if access_rule not in RULES_WITH_RESTRICTED_POWER_LEVELS:
+ return True
+
+ # If users_default is explicitly set to a non-0 value, deny the event.
+ users_default = content.get("users_default", 0)
+ if users_default:
+ return False
+
+ users = content.get("users", {})
+ for user_id, power_level in users.items():
+ server_name = get_domain_from_id(user_id)
+ # Check the domain against the blacklist. If found, and the PL isn't 0, deny
+ # the event.
+ if (
+ server_name in self.domains_forbidden_when_restricted
+ and power_level != 0
+ ):
+ return False
+
+ return True
+
+ def _on_join_rule_change(self, event: EventBase, rule: str) -> bool:
+ """Check whether a join rule change is allowed.
+
+ A join rule change is always allowed unless the new join rule is "public" and
+ the current access rule is "direct".
+
+ Args:
+ event: The event to check.
+ rule: The name of the rule to apply.
+
+ Returns:
+ Whether the change is allowed.
+ """
+ if event.content.get("join_rule") == JoinRules.PUBLIC:
+ return rule != AccessRules.DIRECT
+
+ return True
+
+ def _on_room_avatar_change(self, event: EventBase, rule: str) -> bool:
+ """Check whether a change of room avatar is allowed.
+ The current rule is to forbid such a change in direct chats but allow it
+ everywhere else.
+
+ Args:
+ event: The event to check.
+ rule: The name of the rule to apply.
+
+ Returns:
+ True if the event can be allowed, False otherwise.
+ """
+ return rule != AccessRules.DIRECT
+
+ def _on_room_name_change(self, event: EventBase, rule: str) -> bool:
+ """Check whether a change of room name is allowed.
+ The current rule is to forbid such a change in direct chats but allow it
+ everywhere else.
+
+ Args:
+ event: The event to check.
+ rule: The name of the rule to apply.
+
+ Returns:
+ True if the event can be allowed, False otherwise.
+ """
+ return rule != AccessRules.DIRECT
+
+ def _on_room_topic_change(self, event: EventBase, rule: str) -> bool:
+ """Check whether a change of room topic is allowed.
+ The current rule is to forbid such a change in direct chats but allow it
+ everywhere else.
+
+ Args:
+ event: The event to check.
+ rule: The name of the rule to apply.
+
+ Returns:
+ True if the event can be allowed, False otherwise.
+ """
+ return rule != AccessRules.DIRECT
+
+ @staticmethod
+ def _get_rule_from_state(state_events: StateMap[EventBase]) -> Optional[str]:
+ """Extract the rule to be applied from the given set of state events.
+
+ Args:
+ state_events: A dict mapping (event type, state key) to state event.
+
+ Returns:
+ The name of the rule (either "direct", "restricted" or "unrestricted") if found,
+ else None.
+ """
+ access_rules = state_events.get((ACCESS_RULES_TYPE, ""))
+ if access_rules is None:
+ return AccessRules.RESTRICTED
+
+ return access_rules.content.get("rule")
+
+ @staticmethod
+ def _get_join_rule_from_state(state_events: StateMap[EventBase]) -> Optional[str]:
+ """Extract the room's join rule from the given set of state events.
+
+ Args:
+ state_events (dict[tuple[event type, state key], EventBase]): The set of state
+ events.
+
+ Returns:
+ The name of the join rule (either "public", or "invite") if found, else None.
+ """
+ join_rule_event = state_events.get((EventTypes.JoinRules, ""))
+ if join_rule_event is None:
+ return None
+
+ return join_rule_event.content.get("join_rule")
+
+ @staticmethod
+ def _get_members_and_tokens_from_state(
+ state_events: StateMap[EventBase],
+ ) -> Tuple[List[str], List[str]]:
+ """Retrieves the list of users that have a m.room.member event in the room,
+ as well as 3PID invites tokens in the room.
+
+ Args:
+ state_events: A dict mapping (event type, state key) to state event.
+
+ Returns:
+ A tuple containing the:
+ * targets of the m.room.member events in the state.
+ * 3PID invite tokens in the state.
+ """
+ existing_members = []
+ threepid_invite_tokens = []
+ for key, state_event in state_events.items():
+ if key[0] == EventTypes.Member and state_event.content:
+ existing_members.append(state_event.state_key)
+ if key[0] == EventTypes.ThirdPartyInvite and state_event.content:
+ # Don't include revoked invites.
+ threepid_invite_tokens.append(state_event.state_key)
+
+ return existing_members, threepid_invite_tokens
+
+ @staticmethod
+ def _is_invite_from_threepid(invite: EventBase, threepid_invite_token: str) -> bool:
+ """Checks whether the given invite follows the given 3PID invite.
+
+ Args:
+ invite: The m.room.member event with "invite" membership.
+ threepid_invite_token: The state key from the 3PID invite.
+
+ Returns:
+ Whether the invite is due to the given 3PID invite.
+ """
+ token = (
+ invite.content.get("third_party_invite", {})
+ .get("signed", {})
+ .get("token", "")
+ )
+
+ return token == threepid_invite_token
+
+ def _is_local_user(self, user_id: str) -> bool:
+ """Checks whether a given user ID belongs to this homeserver, or a remote
+
+ Args:
+ user_id: A user ID to check.
+
+ Returns:
+ True if the user belongs to this homeserver, False otherwise.
+ """
+ user = UserID.from_string(user_id)
+
+ # Extract the localpart and ask the module API for a user ID from the localpart
+ # The module API will append the local homeserver's server_name
+ local_user_id = self.module_api.get_qualified_user_id(user.localpart)
+
+ # If the user ID we get based on the localpart is the same as the original user ID,
+ # then they were a local user
+ return user_id == local_user_id
+
+ def _user_is_invited_to_room(
+ self, user_id: str, state_events: StateMap[EventBase]
+ ) -> bool:
+ """Checks whether a given user has been invited to a room
+
+ A user has an invite for a room if its state contains a `m.room.member`
+ event with membership "invite" and their user ID as the state key.
+
+ Args:
+ user_id: The user to check.
+ state_events: The state events from the room.
+
+ Returns:
+ True if the user has been invited to the room, or False if they haven't.
+ """
+ for (event_type, state_key), state_event in state_events.items():
+ if (
+ event_type == EventTypes.Member
+ and state_key == user_id
+ and state_event.membership == Membership.INVITE
+ ):
+ return True
+
+ return False
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