# Copyright 2017 New Vector Ltd # Copyright 2019 The Matrix.org Foundation C.I.C. # # 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 inspect import logging from typing import ( TYPE_CHECKING, Any, Awaitable, Callable, Collection, Dict, List, Optional, Tuple, Union, ) from synapse.rest.media.v1._base import FileInfo from synapse.rest.media.v1.media_storage import ReadableFileWrapper from synapse.spam_checker_api import RegistrationBehaviour from synapse.types import RoomAlias from synapse.util.async_helpers import maybe_awaitable if TYPE_CHECKING: import synapse.events import synapse.server logger = logging.getLogger(__name__) CHECK_EVENT_FOR_SPAM_CALLBACK = Callable[ ["synapse.events.EventBase"], Awaitable[Union[bool, str]], ] USER_MAY_INVITE_CALLBACK = Callable[[str, str, str], Awaitable[bool]] USER_MAY_CREATE_ROOM_CALLBACK = Callable[[str], Awaitable[bool]] USER_MAY_CREATE_ROOM_ALIAS_CALLBACK = Callable[[str, RoomAlias], Awaitable[bool]] USER_MAY_PUBLISH_ROOM_CALLBACK = Callable[[str, str], Awaitable[bool]] CHECK_USERNAME_FOR_SPAM_CALLBACK = Callable[[Dict[str, str]], Awaitable[bool]] LEGACY_CHECK_REGISTRATION_FOR_SPAM_CALLBACK = Callable[ [ Optional[dict], Optional[str], Collection[Tuple[str, str]], ], Awaitable[RegistrationBehaviour], ] CHECK_REGISTRATION_FOR_SPAM_CALLBACK = Callable[ [ Optional[dict], Optional[str], Collection[Tuple[str, str]], Optional[str], ], Awaitable[RegistrationBehaviour], ] CHECK_MEDIA_FILE_FOR_SPAM_CALLBACK = Callable[ [ReadableFileWrapper, FileInfo], Awaitable[bool], ] def load_legacy_spam_checkers(hs: "synapse.server.HomeServer"): """Wrapper that loads spam checkers configured using the old configuration, and registers the spam checker hooks they implement. """ spam_checkers = [] # type: List[Any] api = hs.get_module_api() for module, config in hs.config.spam_checkers: # Older spam checkers don't accept the `api` argument, so we # try and detect support. spam_args = inspect.getfullargspec(module) if "api" in spam_args.args: spam_checkers.append(module(config=config, api=api)) else: spam_checkers.append(module(config=config)) # The known spam checker hooks. If a spam checker module implements a method # which name appears in this set, we'll want to register it. spam_checker_methods = { "check_event_for_spam", "user_may_invite", "user_may_create_room", "user_may_create_room_alias", "user_may_publish_room", "check_username_for_spam", "check_registration_for_spam", "check_media_file_for_spam", } for spam_checker in spam_checkers: # Methods on legacy spam checkers might not be async, so we wrap them around a # wrapper that will call maybe_awaitable on the result. def async_wrapper(f: Optional[Callable]) -> Optional[Callable[..., Awaitable]]: # f might be None if the callback isn't implemented by the module. In this # case we don't want to register a callback at all so we return None. if f is None: return None if f.__name__ == "check_registration_for_spam": checker_args = inspect.signature(f) if len(checker_args.parameters) == 3: # Backwards compatibility; some modules might implement a hook that # doesn't expect a 4th argument. In this case, wrap it in a function # that gives it only 3 arguments and drops the auth_provider_id on # the floor. def wrapper( email_threepid: Optional[dict], username: Optional[str], request_info: Collection[Tuple[str, str]], auth_provider_id: Optional[str], ) -> Union[Awaitable[RegistrationBehaviour], RegistrationBehaviour]: # We've already made sure f is not None above, but mypy doesn't # do well across function boundaries so we need to tell it f is # definitely not None. assert f is not None return f( email_threepid, username, request_info, ) f = wrapper elif len(checker_args.parameters) != 4: raise RuntimeError( "Bad signature for callback check_registration_for_spam", ) def run(*args, **kwargs): # We've already made sure f is not None above, but mypy doesn't do well # across function boundaries so we need to tell it f is definitely not # None. assert f is not None return maybe_awaitable(f(*args, **kwargs)) return run # Register the hooks through the module API. hooks = { hook: async_wrapper(getattr(spam_checker, hook, None)) for hook in spam_checker_methods } api.register_spam_checker_callbacks(**hooks) class SpamChecker: def __init__(self): self._check_event_for_spam_callbacks: List[CHECK_EVENT_FOR_SPAM_CALLBACK] = [] self._user_may_invite_callbacks: List[USER_MAY_INVITE_CALLBACK] = [] self._user_may_create_room_callbacks: List[USER_MAY_CREATE_ROOM_CALLBACK] = [] self._user_may_create_room_alias_callbacks: List[ USER_MAY_CREATE_ROOM_ALIAS_CALLBACK ] = [] self._user_may_publish_room_callbacks: List[USER_MAY_PUBLISH_ROOM_CALLBACK] = [] self._check_username_for_spam_callbacks: List[ CHECK_USERNAME_FOR_SPAM_CALLBACK ] = [] self._check_registration_for_spam_callbacks: List[ CHECK_REGISTRATION_FOR_SPAM_CALLBACK ] = [] self._check_media_file_for_spam_callbacks: List[ CHECK_MEDIA_FILE_FOR_SPAM_CALLBACK ] = [] def register_callbacks( self, check_event_for_spam: Optional[CHECK_EVENT_FOR_SPAM_CALLBACK] = None, user_may_invite: Optional[USER_MAY_INVITE_CALLBACK] = None, user_may_create_room: Optional[USER_MAY_CREATE_ROOM_CALLBACK] = None, user_may_create_room_alias: Optional[ USER_MAY_CREATE_ROOM_ALIAS_CALLBACK ] = None, user_may_publish_room: Optional[USER_MAY_PUBLISH_ROOM_CALLBACK] = None, check_username_for_spam: Optional[CHECK_USERNAME_FOR_SPAM_CALLBACK] = None, check_registration_for_spam: Optional[ CHECK_REGISTRATION_FOR_SPAM_CALLBACK ] = None, check_media_file_for_spam: Optional[CHECK_MEDIA_FILE_FOR_SPAM_CALLBACK] = None, ): """Register callbacks from module for each hook.""" if check_event_for_spam is not None: self._check_event_for_spam_callbacks.append(check_event_for_spam) if user_may_invite is not None: self._user_may_invite_callbacks.append(user_may_invite) if user_may_create_room is not None: self._user_may_create_room_callbacks.append(user_may_create_room) if user_may_create_room_alias is not None: self._user_may_create_room_alias_callbacks.append( user_may_create_room_alias, ) if user_may_publish_room is not None: self._user_may_publish_room_callbacks.append(user_may_publish_room) if check_username_for_spam is not None: self._check_username_for_spam_callbacks.append(check_username_for_spam) if check_registration_for_spam is not None: self._check_registration_for_spam_callbacks.append( check_registration_for_spam, ) if check_media_file_for_spam is not None: self._check_media_file_for_spam_callbacks.append(check_media_file_for_spam) async def check_event_for_spam( self, event: "synapse.events.EventBase" ) -> Union[bool, str]: """Checks if a given event is considered "spammy" by this server. If the server considers an event spammy, then it will be rejected if sent by a local user. If it is sent by a user on another server, then users receive a blank event. Args: event: the event to be checked Returns: True or a string if the event is spammy. If a string is returned it will be used as the error message returned to the user. """ for callback in self._check_event_for_spam_callbacks: res = await callback(event) # type: Union[bool, str] if res: return res return False async def user_may_invite( self, inviter_userid: str, invitee_userid: str, room_id: str ) -> bool: """Checks if a given user may send an invite If this method returns false, the invite will be rejected. Args: inviter_userid: The user ID of the sender of the invitation invitee_userid: The user ID targeted in the invitation room_id: The room ID Returns: True if the user may send an invite, otherwise False """ for callback in self._user_may_invite_callbacks: if await callback(inviter_userid, invitee_userid, room_id) is False: return False return True async def user_may_create_room(self, userid: str) -> bool: """Checks if a given user may create a room If this method returns false, the creation request will be rejected. Args: userid: The ID of the user attempting to create a room Returns: True if the user may create a room, otherwise False """ for callback in self._user_may_create_room_callbacks: if await callback(userid) is False: return False return True async def user_may_create_room_alias( self, userid: str, room_alias: RoomAlias ) -> bool: """Checks if a given user may create a room alias If this method returns false, the association request will be rejected. Args: userid: The ID of the user attempting to create a room alias room_alias: The alias to be created Returns: True if the user may create a room alias, otherwise False """ for callback in self._user_may_create_room_alias_callbacks: if await callback(userid, room_alias) is False: return False return True async def user_may_publish_room(self, userid: str, room_id: str) -> bool: """Checks if a given user may publish a room to the directory If this method returns false, the publish request will be rejected. Args: userid: The user ID attempting to publish the room room_id: The ID of the room that would be published Returns: True if the user may publish the room, otherwise False """ for callback in self._user_may_publish_room_callbacks: if await callback(userid, room_id) is False: return False return True async def check_username_for_spam(self, user_profile: Dict[str, str]) -> bool: """Checks if a user ID or display name are considered "spammy" by this server. If the server considers a username spammy, then it will not be included in user directory results. Args: user_profile: The user information to check, it contains the keys: * user_id * display_name * avatar_url Returns: True if the user is spammy. """ for callback in self._check_username_for_spam_callbacks: # Make a copy of the user profile object to ensure the spam checker cannot # modify it. if await callback(user_profile.copy()): return True return False async def check_registration_for_spam( self, email_threepid: Optional[dict], username: Optional[str], request_info: Collection[Tuple[str, str]], auth_provider_id: Optional[str] = None, ) -> RegistrationBehaviour: """Checks if we should allow the given registration request. Args: email_threepid: The email threepid used for registering, if any username: The request user name, if any request_info: List of tuples of user agent and IP that were used during the registration process. auth_provider_id: The SSO IdP the user used, e.g "oidc", "saml", "cas". If any. Note this does not include users registered via a password provider. Returns: Enum for how the request should be handled """ for callback in self._check_registration_for_spam_callbacks: behaviour = await ( callback(email_threepid, username, request_info, auth_provider_id) ) assert isinstance(behaviour, RegistrationBehaviour) if behaviour != RegistrationBehaviour.ALLOW: return behaviour return RegistrationBehaviour.ALLOW async def check_media_file_for_spam( self, file_wrapper: ReadableFileWrapper, file_info: FileInfo ) -> bool: """Checks if a piece of newly uploaded media should be blocked. This will be called for local uploads, downloads of remote media, each thumbnail generated for those, and web pages/images used for URL previews. Note that care should be taken to not do blocking IO operations in the main thread. For example, to get the contents of a file a module should do:: async def check_media_file_for_spam( self, file: ReadableFileWrapper, file_info: FileInfo ) -> bool: buffer = BytesIO() await file.write_chunks_to(buffer.write) if buffer.getvalue() == b"Hello World": return True return False Args: file: An object that allows reading the contents of the media. file_info: Metadata about the file. Returns: True if the media should be blocked or False if it should be allowed. """ for callback in self._check_media_file_for_spam_callbacks: spam = await callback(file_wrapper, file_info) if spam: return True return False