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synapse-old/synapse/events/spamcheck.py

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# 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,
List,
Optional,
Tuple,
Union,
)
from synapse.api.errors import Codes
from synapse.rest.media.v1._base import FileInfo
from synapse.rest.media.v1.media_storage import ReadableFileWrapper
from synapse.spam_checker_api import Allow, Decision, RegistrationBehaviour
from synapse.types import RoomAlias, UserProfile
from synapse.util.async_helpers import delay_cancellation, maybe_awaitable
from synapse.util.metrics import Measure
if TYPE_CHECKING:
import synapse.events
import synapse.server
logger = logging.getLogger(__name__)
CHECK_EVENT_FOR_SPAM_CALLBACK = Callable[
["synapse.events.EventBase"],
Awaitable[
Union[
Allow,
Codes,
# Deprecated
bool,
# Deprecated
str,
]
],
]
SHOULD_DROP_FEDERATED_EVENT_CALLBACK = Callable[
["synapse.events.EventBase"],
Awaitable[Union[bool, str]],
]
USER_MAY_JOIN_ROOM_CALLBACK = Callable[[str, str, bool], Awaitable[bool]]
USER_MAY_INVITE_CALLBACK = Callable[[str, str, str], Awaitable[bool]]
USER_MAY_SEND_3PID_INVITE_CALLBACK = Callable[[str, 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[[UserProfile], 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") -> None:
"""Wrapper that loads spam checkers configured using the old configuration, and
registers the spam checker hooks they implement.
"""
spam_checkers: List[Any] = []
api = hs.get_module_api()
for module, config in hs.config.spamchecker.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
wrapped_func = f
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]:
# Assertion required because mypy can't prove we won't
# change `f` back to `None`. See
# https://mypy.readthedocs.io/en/latest/common_issues.html#narrowing-and-inner-functions
assert f is not None
return f(
email_threepid,
username,
request_info,
)
wrapped_func = wrapper
elif len(checker_args.parameters) != 4:
raise RuntimeError(
"Bad signature for callback check_registration_for_spam",
)
def run(*args: Any, **kwargs: Any) -> Awaitable:
# Assertion required because mypy can't prove we won't change `f`
# back to `None`. See
# https://mypy.readthedocs.io/en/latest/common_issues.html#narrowing-and-inner-functions
assert wrapped_func is not None
return maybe_awaitable(wrapped_func(*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, hs: "synapse.server.HomeServer") -> None:
self.hs = hs
self.clock = hs.get_clock()
self._check_event_for_spam_callbacks: List[CHECK_EVENT_FOR_SPAM_CALLBACK] = []
self._should_drop_federated_event_callbacks: List[
SHOULD_DROP_FEDERATED_EVENT_CALLBACK
] = []
self._user_may_join_room_callbacks: List[USER_MAY_JOIN_ROOM_CALLBACK] = []
self._user_may_invite_callbacks: List[USER_MAY_INVITE_CALLBACK] = []
self._user_may_send_3pid_invite_callbacks: List[
USER_MAY_SEND_3PID_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,
should_drop_federated_event: Optional[
SHOULD_DROP_FEDERATED_EVENT_CALLBACK
] = None,
user_may_join_room: Optional[USER_MAY_JOIN_ROOM_CALLBACK] = None,
user_may_invite: Optional[USER_MAY_INVITE_CALLBACK] = None,
user_may_send_3pid_invite: Optional[USER_MAY_SEND_3PID_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,
) -> 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 should_drop_federated_event is not None:
self._should_drop_federated_event_callbacks.append(
should_drop_federated_event
)
if user_may_join_room is not None:
self._user_may_join_room_callbacks.append(user_may_join_room)
if user_may_invite is not None:
self._user_may_invite_callbacks.append(user_may_invite)
if user_may_send_3pid_invite is not None:
self._user_may_send_3pid_invite_callbacks.append(
user_may_send_3pid_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[Decision, 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, the
event is soft-failed.
Args:
event: the event to be checked
Returns:
- on `ALLOW`, the event is considered good (non-spammy) and should
be let through. Other spamcheck filters may still reject it.
- on `Code`, the event is considered spammy and is rejected with a specific
error message/code.
- on `str`, the event is considered spammy and the string is used as error
message. This usage is generally discouraged as it doesn't support
internationalization.
"""
for callback in self._check_event_for_spam_callbacks:
with Measure(
self.clock, "{}.{}".format(callback.__module__, callback.__qualname__)
):
res: Union[Decision, str, bool] = await delay_cancellation(
callback(event)
)
if res is False or res is Allow.ALLOW:
# This spam-checker accepts the event.
# Other spam-checkers may reject it, though.
continue
elif res is True:
# This spam-checker rejects the event with deprecated
# return value `True`
return Codes.FORBIDDEN
else:
# This spam-checker rejects the event either with a `str`
# or with a `Codes`. In either case, we stop here.
return res
# No spam-checker has rejected the event, let it pass.
return Allow.ALLOW
async def should_drop_federated_event(
self, event: "synapse.events.EventBase"
) -> Union[bool, str]:
"""Checks if a given federated event is considered "spammy" by this
server.
If the server considers an event spammy, it will be silently dropped,
and in doing so will split-brain our view of the room's DAG.
Args:
event: the event to be checked
Returns:
True if the event should be silently dropped
"""
for callback in self._should_drop_federated_event_callbacks:
with Measure(
self.clock, "{}.{}".format(callback.__module__, callback.__qualname__)
):
res: Union[bool, str] = await delay_cancellation(callback(event))
if res:
return res
return False
async def user_may_join_room(
self, user_id: str, room_id: str, is_invited: bool
) -> bool:
"""Checks if a given users is allowed to join a room.
Not called when a user creates a room.
Args:
userid: The ID of the user wanting to join the room
room_id: The ID of the room the user wants to join
is_invited: Whether the user is invited into the room
Returns:
Whether the user may join the room
"""
for callback in self._user_may_join_room_callbacks:
with Measure(
self.clock, "{}.{}".format(callback.__module__, callback.__qualname__)
):
may_join_room = await delay_cancellation(
callback(user_id, room_id, is_invited)
)
if may_join_room is False:
return False
return True
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:
with Measure(
self.clock, "{}.{}".format(callback.__module__, callback.__qualname__)
):
may_invite = await delay_cancellation(
callback(inviter_userid, invitee_userid, room_id)
)
if may_invite is False:
return False
return True
async def user_may_send_3pid_invite(
self, inviter_userid: str, medium: str, address: str, room_id: str
) -> bool:
"""Checks if a given user may invite a given threepid into the room
If this method returns false, the threepid invite will be rejected.
Note that if the threepid is already associated with a Matrix user ID, Synapse
will call user_may_invite with said user ID instead.
Args:
inviter_userid: The user ID of the sender of the invitation
medium: The 3PID's medium (e.g. "email")
address: The 3PID's address (e.g. "alice@example.com")
room_id: The room ID
Returns:
True if the user may send the invite, otherwise False
"""
for callback in self._user_may_send_3pid_invite_callbacks:
with Measure(
self.clock, "{}.{}".format(callback.__module__, callback.__qualname__)
):
may_send_3pid_invite = await delay_cancellation(
callback(inviter_userid, medium, address, room_id)
)
if may_send_3pid_invite 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:
with Measure(
self.clock, "{}.{}".format(callback.__module__, callback.__qualname__)
):
may_create_room = await delay_cancellation(callback(userid))
if may_create_room 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:
with Measure(
self.clock, "{}.{}".format(callback.__module__, callback.__qualname__)
):
may_create_room_alias = await delay_cancellation(
callback(userid, room_alias)
)
if may_create_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:
with Measure(
self.clock, "{}.{}".format(callback.__module__, callback.__qualname__)
):
may_publish_room = await delay_cancellation(callback(userid, room_id))
if may_publish_room is False:
return False
return True
async def check_username_for_spam(self, user_profile: UserProfile) -> 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:
with Measure(
self.clock, "{}.{}".format(callback.__module__, callback.__qualname__)
):
# Make a copy of the user profile object to ensure the spam checker cannot
# modify it.
res = await delay_cancellation(callback(user_profile.copy()))
if res:
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:
with Measure(
self.clock, "{}.{}".format(callback.__module__, callback.__qualname__)
):
behaviour = await delay_cancellation(
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:
with Measure(
self.clock, "{}.{}".format(callback.__module__, callback.__qualname__)
):
spam = await delay_cancellation(callback(file_wrapper, file_info))
if spam:
return True
return False
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