synapse-product/synapse/events/builder.py
Erik Johnston be47cfa9c9 Refactor event building into EventBuilder
This is so that everything is done in one place, making it easier to
change the event format based on room version
2019-01-29 11:13:00 +00:00

279 lines
8.0 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.
import attr
from twisted.internet import defer
from synapse.api.constants import (
KNOWN_EVENT_FORMAT_VERSIONS,
KNOWN_ROOM_VERSIONS,
MAX_DEPTH,
)
from synapse.crypto.event_signing import add_hashes_and_signatures
from synapse.types import EventID
from synapse.util.stringutils import random_string
from . import (
_EventInternalMetadata,
event_type_from_format_version,
room_version_to_event_format,
)
@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:
format_version (int): Event format version
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()
format_version = attr.ib()
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)
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
@defer.inlineCallbacks
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:
Deferred[FrozenEvent]
"""
state_ids = yield self._state.get_current_state_ids(
self.room_id, prev_event_ids,
)
auth_ids = yield self._auth.compute_auth_events(
self, state_ids,
)
auth_events = yield self._store.add_event_hashes(auth_ids)
prev_events = yield self._store.add_event_hashes(prev_event_ids)
old_depth = yield 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
defer.returnValue(
create_local_event_from_event_dict(
clock=self._clock,
hostname=self._hostname,
signing_key=self._signing_key,
format_version=self.format_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.config.signing_key[0]
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
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
"""
# There's currently only the one event version defined
if room_version not in KNOWN_ROOM_VERSIONS:
raise Exception(
"No event format defined for version %r" % (room_version,)
)
key_values["event_id"] = _create_event_id(self.clock, self.hostname)
return EventBuilder(
store=self.store,
state=self.state,
auth=self.auth,
clock=self.clock,
hostname=self.hostname,
signing_key=self.signing_key,
format_version=room_version_to_event_format(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),
)
def create_local_event_from_event_dict(clock, hostname, signing_key,
format_version, event_dict,
internal_metadata_dict=None):
"""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.
Args:
clock (Clock)
hostname (str)
signing_key
format_version (int)
event_dict (dict)
internal_metadata_dict (dict|None)
Returns:
FrozenEvent
"""
# There's currently only the one event version defined
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())
event_dict["event_id"] = _create_event_id(clock, hostname)
event_dict["origin"] = hostname
event_dict["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(
event_dict,
hostname,
signing_key,
)
return event_type_from_format_version(format_version)(
event_dict, 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()