MatrixSynapse/synapse/api/filtering.py

# Copyright 2015, 2016 OpenMarket Ltd
# Copyright 2017 Vector Creations Ltd
# Copyright 2018-2019 New Vector Ltd
# Copyright 2019-2021 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 json
from typing import (
    TYPE_CHECKING,
    Awaitable,
    Callable,
    Dict,
    Iterable,
    List,
    Optional,
    Set,
    TypeVar,
    Union,
)

import jsonschema
from jsonschema import FormatChecker

from synapse.api.constants import EventContentFields
from synapse.api.errors import SynapseError
from synapse.api.presence import UserPresenceState
from synapse.events import EventBase
from synapse.types import JsonDict, RoomID, UserID

if TYPE_CHECKING:
    from synapse.server import HomeServer

FILTER_SCHEMA = {
    "additionalProperties": False,
    "type": "object",
    "properties": {
        "limit": {"type": "number"},
        "senders": {"$ref": "#/definitions/user_id_array"},
        "not_senders": {"$ref": "#/definitions/user_id_array"},
        # TODO: We don't limit event type values but we probably should...
        # check types are valid event types
        "types": {"type": "array", "items": {"type": "string"}},
        "not_types": {"type": "array", "items": {"type": "string"}},
    },
}

ROOM_FILTER_SCHEMA = {
    "additionalProperties": False,
    "type": "object",
    "properties": {
        "not_rooms": {"$ref": "#/definitions/room_id_array"},
        "rooms": {"$ref": "#/definitions/room_id_array"},
        "ephemeral": {"$ref": "#/definitions/room_event_filter"},
        "include_leave": {"type": "boolean"},
        "state": {"$ref": "#/definitions/room_event_filter"},
        "timeline": {"$ref": "#/definitions/room_event_filter"},
        "account_data": {"$ref": "#/definitions/room_event_filter"},
    },
}

ROOM_EVENT_FILTER_SCHEMA = {
    "additionalProperties": False,
    "type": "object",
    "properties": {
        "limit": {"type": "number"},
        "senders": {"$ref": "#/definitions/user_id_array"},
        "not_senders": {"$ref": "#/definitions/user_id_array"},
        "types": {"type": "array", "items": {"type": "string"}},
        "not_types": {"type": "array", "items": {"type": "string"}},
        "rooms": {"$ref": "#/definitions/room_id_array"},
        "not_rooms": {"$ref": "#/definitions/room_id_array"},
        "contains_url": {"type": "boolean"},
        "lazy_load_members": {"type": "boolean"},
        "include_redundant_members": {"type": "boolean"},
        # Include or exclude events with the provided labels.
        # cf https://github.com/matrix-org/matrix-doc/pull/2326
        "org.matrix.labels": {"type": "array", "items": {"type": "string"}},
        "org.matrix.not_labels": {"type": "array", "items": {"type": "string"}},
        # MSC3440, filtering by event relations.
        "io.element.relation_senders": {"type": "array", "items": {"type": "string"}},
        "io.element.relation_types": {"type": "array", "items": {"type": "string"}},
    },
}

USER_ID_ARRAY_SCHEMA = {
    "type": "array",
    "items": {"type": "string", "format": "matrix_user_id"},
}

ROOM_ID_ARRAY_SCHEMA = {
    "type": "array",
    "items": {"type": "string", "format": "matrix_room_id"},
}

USER_FILTER_SCHEMA = {
    "$schema": "http://json-schema.org/draft-04/schema#",
    "description": "schema for a Sync filter",
    "type": "object",
    "definitions": {
        "room_id_array": ROOM_ID_ARRAY_SCHEMA,
        "user_id_array": USER_ID_ARRAY_SCHEMA,
        "filter": FILTER_SCHEMA,
        "room_filter": ROOM_FILTER_SCHEMA,
        "room_event_filter": ROOM_EVENT_FILTER_SCHEMA,
    },
    "properties": {
        "presence": {"$ref": "#/definitions/filter"},
        "account_data": {"$ref": "#/definitions/filter"},
        "room": {"$ref": "#/definitions/room_filter"},
        "event_format": {"type": "string", "enum": ["client", "federation"]},
        "event_fields": {
            "type": "array",
            "items": {
                "type": "string",
                # Don't allow '\\' in event field filters. This makes matching
                # events a lot easier as we can then use a negative lookbehind
                # assertion to split '\.' If we allowed \\ then it would
                # incorrectly split '\\.' See synapse.events.utils.serialize_event
                #
                # Note that because this is a regular expression, we have to escape
                # each backslash in the pattern.
                "pattern": r"^((?!\\\\).)*$",
            },
        },
    },
    "additionalProperties": False,
}


@FormatChecker.cls_checks("matrix_room_id")
def matrix_room_id_validator(room_id_str: str) -> RoomID:
    return RoomID.from_string(room_id_str)


@FormatChecker.cls_checks("matrix_user_id")
def matrix_user_id_validator(user_id_str: str) -> UserID:
    return UserID.from_string(user_id_str)


class Filtering:
    def __init__(self, hs: "HomeServer"):
        self._hs = hs
        self.store = hs.get_datastore()

        self.DEFAULT_FILTER_COLLECTION = FilterCollection(hs, {})

    async def get_user_filter(
        self, user_localpart: str, filter_id: Union[int, str]
    ) -> "FilterCollection":
        result = await self.store.get_user_filter(user_localpart, filter_id)
        return FilterCollection(self._hs, result)

    def add_user_filter(
        self, user_localpart: str, user_filter: JsonDict
    ) -> Awaitable[int]:
        self.check_valid_filter(user_filter)
        return self.store.add_user_filter(user_localpart, user_filter)

    # TODO(paul): surely we should probably add a delete_user_filter or
    #   replace_user_filter at some point? There's no REST API specified for
    #   them however

    def check_valid_filter(self, user_filter_json: JsonDict) -> None:
        """Check if the provided filter is valid.

        This inspects all definitions contained within the filter.

        Args:
            user_filter_json: The filter
        Raises:
            SynapseError: If the filter is not valid.
        """
        # NB: Filters are the complete json blobs. "Definitions" are an
        # individual top-level key e.g. public_user_data. Filters are made of
        # many definitions.
        try:
            jsonschema.validate(
                user_filter_json, USER_FILTER_SCHEMA, format_checker=FormatChecker()
            )
        except jsonschema.ValidationError as e:
            raise SynapseError(400, str(e))


# Filters work across events, presence EDUs, and account data.
FilterEvent = TypeVar("FilterEvent", EventBase, UserPresenceState, JsonDict)


class FilterCollection:
    def __init__(self, hs: "HomeServer", filter_json: JsonDict):
        self._filter_json = filter_json

        room_filter_json = self._filter_json.get("room", {})

        self._room_filter = Filter(
            hs,
            {k: v for k, v in room_filter_json.items() if k in ("rooms", "not_rooms")},
        )

        self._room_timeline_filter = Filter(hs, room_filter_json.get("timeline", {}))
        self._room_state_filter = Filter(hs, room_filter_json.get("state", {}))
        self._room_ephemeral_filter = Filter(hs, room_filter_json.get("ephemeral", {}))
        self._room_account_data = Filter(hs, room_filter_json.get("account_data", {}))
        self._presence_filter = Filter(hs, filter_json.get("presence", {}))
        self._account_data = Filter(hs, filter_json.get("account_data", {}))

        self.include_leave = filter_json.get("room", {}).get("include_leave", False)
        self.event_fields = filter_json.get("event_fields", [])
        self.event_format = filter_json.get("event_format", "client")

    def __repr__(self) -> str:
        return "<FilterCollection %s>" % (json.dumps(self._filter_json),)

    def get_filter_json(self) -> JsonDict:
        return self._filter_json

    def timeline_limit(self) -> int:
        return self._room_timeline_filter.limit

    def presence_limit(self) -> int:
        return self._presence_filter.limit

    def ephemeral_limit(self) -> int:
        return self._room_ephemeral_filter.limit

    def lazy_load_members(self) -> bool:
        return self._room_state_filter.lazy_load_members

    def include_redundant_members(self) -> bool:
        return self._room_state_filter.include_redundant_members

    async def filter_presence(
        self, events: Iterable[UserPresenceState]
    ) -> List[UserPresenceState]:
        return await self._presence_filter.filter(events)

    async def filter_account_data(self, events: Iterable[JsonDict]) -> List[JsonDict]:
        return await self._account_data.filter(events)

    async def filter_room_state(self, events: Iterable[EventBase]) -> List[EventBase]:
        return await self._room_state_filter.filter(
            await self._room_filter.filter(events)
        )

    async def filter_room_timeline(
        self, events: Iterable[EventBase]
    ) -> List[EventBase]:
        return await self._room_timeline_filter.filter(
            await self._room_filter.filter(events)
        )

    async def filter_room_ephemeral(self, events: Iterable[JsonDict]) -> List[JsonDict]:
        return await self._room_ephemeral_filter.filter(
            await self._room_filter.filter(events)
        )

    async def filter_room_account_data(
        self, events: Iterable[JsonDict]
    ) -> List[JsonDict]:
        return await self._room_account_data.filter(
            await self._room_filter.filter(events)
        )

    def blocks_all_presence(self) -> bool:
        return (
            self._presence_filter.filters_all_types()
            or self._presence_filter.filters_all_senders()
        )

    def blocks_all_room_ephemeral(self) -> bool:
        return (
            self._room_ephemeral_filter.filters_all_types()
            or self._room_ephemeral_filter.filters_all_senders()
            or self._room_ephemeral_filter.filters_all_rooms()
        )

    def blocks_all_room_timeline(self) -> bool:
        return (
            self._room_timeline_filter.filters_all_types()
            or self._room_timeline_filter.filters_all_senders()
            or self._room_timeline_filter.filters_all_rooms()
        )


class Filter:
    def __init__(self, hs: "HomeServer", filter_json: JsonDict):
        self._hs = hs
        self._store = hs.get_datastore()
        self.filter_json = filter_json

        self.limit = filter_json.get("limit", 10)
        self.lazy_load_members = filter_json.get("lazy_load_members", False)
        self.include_redundant_members = filter_json.get(
            "include_redundant_members", False
        )

        self.types = filter_json.get("types", None)
        self.not_types = filter_json.get("not_types", [])

        self.rooms = filter_json.get("rooms", None)
        self.not_rooms = filter_json.get("not_rooms", [])

        self.senders = filter_json.get("senders", None)
        self.not_senders = filter_json.get("not_senders", [])

        self.contains_url = filter_json.get("contains_url", None)

        self.labels = filter_json.get("org.matrix.labels", None)
        self.not_labels = filter_json.get("org.matrix.not_labels", [])

        # Ideally these would be rejected at the endpoint if they were provided
        # and not supported, but that would involve modifying the JSON schema
        # based on the homeserver configuration.
        if hs.config.experimental.msc3440_enabled:
            self.relation_senders = self.filter_json.get(
                "io.element.relation_senders", None
            )
            self.relation_types = self.filter_json.get(
                "io.element.relation_types", None
            )
        else:
            self.relation_senders = None
            self.relation_types = None

    def filters_all_types(self) -> bool:
        return "*" in self.not_types

    def filters_all_senders(self) -> bool:
        return "*" in self.not_senders

    def filters_all_rooms(self) -> bool:
        return "*" in self.not_rooms

    def _check(self, event: FilterEvent) -> bool:
        """Checks whether the filter matches the given event.

        Args:
            event: The event, account data, or presence to check against this
                filter.

        Returns:
            True if the event matches the filter.
        """
        # We usually get the full "events" as dictionaries coming through,
        # except for presence which actually gets passed around as its own
        # namedtuple type.
        if isinstance(event, UserPresenceState):
            user_id = event.user_id
            field_matchers = {
                "senders": lambda v: user_id == v,
                "types": lambda v: "m.presence" == v,
            }
            return self._check_fields(field_matchers)
        else:
            content = event.get("content")
            # Content is assumed to be a dict below, so ensure it is. This should
            # always be true for events, but account_data has been allowed to
            # have non-dict content.
            if not isinstance(content, dict):
                content = {}

            sender = event.get("sender", None)
            if not sender:
                # Presence events had their 'sender' in content.user_id, but are
                # now handled above. We don't know if anything else uses this
                # form. TODO: Check this and probably remove it.
                sender = content.get("user_id")

            room_id = event.get("room_id", None)
            ev_type = event.get("type", None)

            # check if there is a string url field in the content for filtering purposes
            labels = content.get(EventContentFields.LABELS, [])

            field_matchers = {
                "rooms": lambda v: room_id == v,
                "senders": lambda v: sender == v,
                "types": lambda v: _matches_wildcard(ev_type, v),
                "labels": lambda v: v in labels,
            }

            result = self._check_fields(field_matchers)
            if not result:
                return result

            contains_url_filter = self.contains_url
            if contains_url_filter is not None:
                contains_url = isinstance(content.get("url"), str)
                if contains_url_filter != contains_url:
                    return False

            return True

    def _check_fields(self, field_matchers: Dict[str, Callable[[str], bool]]) -> bool:
        """Checks whether the filter matches the given event fields.

        Args:
            field_matchers: A map of attribute name to callable to use for checking
                particular fields.

                The attribute name and an inverse (not_<attribute name>) must
                exist on the Filter.

                The callable should return true if the event's value matches the
                filter's value.

        Returns:
            True if the event fields match
        """

        for name, match_func in field_matchers.items():
            # If the event matches one of the disallowed values, reject it.
            not_name = "not_%s" % (name,)
            disallowed_values = getattr(self, not_name)
            if any(map(match_func, disallowed_values)):
                return False

            # Other the event does not match at least one of the allowed values,
            # reject it.
            allowed_values = getattr(self, name)
            if allowed_values is not None:
                if not any(map(match_func, allowed_values)):
                    return False

        # Otherwise, accept it.
        return True

    def filter_rooms(self, room_ids: Iterable[str]) -> Set[str]:
        """Apply the 'rooms' filter to a given list of rooms.

        Args:
            room_ids: A list of room_ids.

        Returns:
            A list of room_ids that match the filter
        """
        room_ids = set(room_ids)

        disallowed_rooms = set(self.not_rooms)
        room_ids -= disallowed_rooms

        allowed_rooms = self.rooms
        if allowed_rooms is not None:
            room_ids &= set(allowed_rooms)

        return room_ids

    async def _check_event_relations(
        self, events: Iterable[FilterEvent]
    ) -> List[FilterEvent]:
        # The event IDs to check, mypy doesn't understand the ifinstance check.
        event_ids = [event.event_id for event in events if isinstance(event, EventBase)]  # type: ignore[attr-defined]
        event_ids_to_keep = set(
            await self._store.events_have_relations(
                event_ids, self.relation_senders, self.relation_types
            )
        )

        return [
            event
            for event in events
            if not isinstance(event, EventBase) or event.event_id in event_ids_to_keep
        ]

    async def filter(self, events: Iterable[FilterEvent]) -> List[FilterEvent]:
        result = [event for event in events if self._check(event)]

        if self.relation_senders or self.relation_types:
            return await self._check_event_relations(result)

        return result

    def with_room_ids(self, room_ids: Iterable[str]) -> "Filter":
        """Returns a new filter with the given room IDs appended.

        Args:
            room_ids: The room_ids to add

        Returns:
            filter: A new filter including the given rooms and the old
                    filter's rooms.
        """
        newFilter = Filter(self._hs, self.filter_json)
        newFilter.rooms += room_ids
        return newFilter


def _matches_wildcard(actual_value: Optional[str], filter_value: str) -> bool:
    if filter_value.endswith("*") and isinstance(actual_value, str):
        type_prefix = filter_value[:-1]
        return actual_value.startswith(type_prefix)
    else:
        return actual_value == filter_value