forked-synapse/synapse/events/builder.py
2020-08-06 08:30:06 -04:00

282 lines
8.7 KiB
Python

# -*- coding: utf-8 -*-
# Copyright 2014-2016 OpenMarket 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.
from typing import Optional
import attr
from nacl.signing import SigningKey
from synapse.api.constants import MAX_DEPTH
from synapse.api.errors import UnsupportedRoomVersionError
from synapse.api.room_versions import (
KNOWN_EVENT_FORMAT_VERSIONS,
KNOWN_ROOM_VERSIONS,
EventFormatVersions,
RoomVersion,
)
from synapse.crypto.event_signing import add_hashes_and_signatures
from synapse.events import EventBase, _EventInternalMetadata, make_event_from_dict
from synapse.types import EventID, JsonDict
from synapse.util import Clock
from synapse.util.stringutils import random_string
@attr.s(slots=True, cmp=False, frozen=True)
class EventBuilder(object):
"""A format independent event builder used to build up the event content
before signing the event.
(Note that while objects of this class are frozen, the
content/unsigned/internal_metadata fields are still mutable)
Attributes:
room_version: Version of the target room
room_id (str)
type (str)
sender (str)
content (dict)
unsigned (dict)
internal_metadata (_EventInternalMetadata)
_state (StateHandler)
_auth (synapse.api.Auth)
_store (DataStore)
_clock (Clock)
_hostname (str): The hostname of the server creating the event
_signing_key: The signing key to use to sign the event as the server
"""
_state = attr.ib()
_auth = attr.ib()
_store = attr.ib()
_clock = attr.ib()
_hostname = attr.ib()
_signing_key = attr.ib()
room_version = attr.ib(type=RoomVersion)
room_id = attr.ib()
type = attr.ib()
sender = attr.ib()
content = attr.ib(default=attr.Factory(dict))
unsigned = attr.ib(default=attr.Factory(dict))
# These only exist on a subset of events, so they raise AttributeError if
# someone tries to get them when they don't exist.
_state_key = attr.ib(default=None)
_redacts = attr.ib(default=None)
_origin_server_ts = attr.ib(default=None)
internal_metadata = attr.ib(
default=attr.Factory(lambda: _EventInternalMetadata({}))
)
@property
def state_key(self):
if self._state_key is not None:
return self._state_key
raise AttributeError("state_key")
def is_state(self):
return self._state_key is not None
async def build(self, prev_event_ids):
"""Transform into a fully signed and hashed event
Args:
prev_event_ids (list[str]): The event IDs to use as the prev events
Returns:
FrozenEvent
"""
state_ids = await self._state.get_current_state_ids(
self.room_id, prev_event_ids
)
auth_ids = self._auth.compute_auth_events(self, state_ids)
format_version = self.room_version.event_format
if format_version == EventFormatVersions.V1:
auth_events = await self._store.add_event_hashes(auth_ids)
prev_events = await self._store.add_event_hashes(prev_event_ids)
else:
auth_events = auth_ids
prev_events = prev_event_ids
old_depth = await self._store.get_max_depth_of(prev_event_ids)
depth = old_depth + 1
# we cap depth of generated events, to ensure that they are not
# rejected by other servers (and so that they can be persisted in
# the db)
depth = min(depth, MAX_DEPTH)
event_dict = {
"auth_events": auth_events,
"prev_events": prev_events,
"type": self.type,
"room_id": self.room_id,
"sender": self.sender,
"content": self.content,
"unsigned": self.unsigned,
"depth": depth,
"prev_state": [],
}
if self.is_state():
event_dict["state_key"] = self._state_key
if self._redacts is not None:
event_dict["redacts"] = self._redacts
if self._origin_server_ts is not None:
event_dict["origin_server_ts"] = self._origin_server_ts
return create_local_event_from_event_dict(
clock=self._clock,
hostname=self._hostname,
signing_key=self._signing_key,
room_version=self.room_version,
event_dict=event_dict,
internal_metadata_dict=self.internal_metadata.get_dict(),
)
class EventBuilderFactory(object):
def __init__(self, hs):
self.clock = hs.get_clock()
self.hostname = hs.hostname
self.signing_key = hs.signing_key
self.store = hs.get_datastore()
self.state = hs.get_state_handler()
self.auth = hs.get_auth()
def new(self, room_version, key_values):
"""Generate an event builder appropriate for the given room version
Deprecated: use for_room_version with a RoomVersion object instead
Args:
room_version (str): Version of the room that we're creating an event builder
for
key_values (dict): Fields used as the basis of the new event
Returns:
EventBuilder
"""
v = KNOWN_ROOM_VERSIONS.get(room_version)
if not v:
# this can happen if support is withdrawn for a room version
raise UnsupportedRoomVersionError()
return self.for_room_version(v, key_values)
def for_room_version(self, room_version, key_values):
"""Generate an event builder appropriate for the given room version
Args:
room_version (synapse.api.room_versions.RoomVersion):
Version of the room that we're creating an event builder for
key_values (dict): Fields used as the basis of the new event
Returns:
EventBuilder
"""
return EventBuilder(
store=self.store,
state=self.state,
auth=self.auth,
clock=self.clock,
hostname=self.hostname,
signing_key=self.signing_key,
room_version=room_version,
type=key_values["type"],
state_key=key_values.get("state_key"),
room_id=key_values["room_id"],
sender=key_values["sender"],
content=key_values.get("content", {}),
unsigned=key_values.get("unsigned", {}),
redacts=key_values.get("redacts", None),
origin_server_ts=key_values.get("origin_server_ts", None),
)
def create_local_event_from_event_dict(
clock: Clock,
hostname: str,
signing_key: SigningKey,
room_version: RoomVersion,
event_dict: JsonDict,
internal_metadata_dict: Optional[JsonDict] = None,
) -> EventBase:
"""Takes a fully formed event dict, ensuring that fields like `origin`
and `origin_server_ts` have correct values for a locally produced event,
then signs and hashes it.
"""
format_version = room_version.event_format
if format_version not in KNOWN_EVENT_FORMAT_VERSIONS:
raise Exception("No event format defined for version %r" % (format_version,))
if internal_metadata_dict is None:
internal_metadata_dict = {}
time_now = int(clock.time_msec())
if format_version == EventFormatVersions.V1:
event_dict["event_id"] = _create_event_id(clock, hostname)
event_dict["origin"] = hostname
event_dict.setdefault("origin_server_ts", time_now)
event_dict.setdefault("unsigned", {})
age = event_dict["unsigned"].pop("age", 0)
event_dict["unsigned"].setdefault("age_ts", time_now - age)
event_dict.setdefault("signatures", {})
add_hashes_and_signatures(room_version, event_dict, hostname, signing_key)
return make_event_from_dict(
event_dict, room_version, internal_metadata_dict=internal_metadata_dict
)
# A counter used when generating new event IDs
_event_id_counter = 0
def _create_event_id(clock, hostname):
"""Create a new event ID
Args:
clock (Clock)
hostname (str): The server name for the event ID
Returns:
str
"""
global _event_id_counter
i = str(_event_id_counter)
_event_id_counter += 1
local_part = str(int(clock.time())) + i + random_string(5)
e_id = EventID(local_part, hostname)
return e_id.to_string()