synapse-product/synapse/events/builder.py

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# Copyright 2014-2016 OpenMarket Ltd
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#
# 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 logging
from typing import TYPE_CHECKING, Any, Dict, List, Optional, Tuple, Union
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import attr
from signedjson.types import SigningKey
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from synapse.api.constants import MAX_DEPTH
from synapse.api.room_versions import (
KNOWN_EVENT_FORMAT_VERSIONS,
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EventFormatVersions,
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RoomVersion,
)
from synapse.crypto.event_signing import add_hashes_and_signatures
from synapse.event_auth import auth_types_for_event
from synapse.events import EventBase, _EventInternalMetadata, make_event_from_dict
from synapse.state import StateHandler
from synapse.storage.databases.main import DataStore
from synapse.storage.state import StateFilter
from synapse.types import EventID, JsonDict
from synapse.util import Clock
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from synapse.util.stringutils import random_string
if TYPE_CHECKING:
from synapse.handlers.event_auth import EventAuthHandler
from synapse.server import HomeServer
logger = logging.getLogger(__name__)
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@attr.s(slots=True, cmp=False, frozen=True, auto_attribs=True)
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class EventBuilder:
"""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:
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room_version: Version of the target room
room_id
type
sender
content
unsigned
internal_metadata
_state
_auth
_store
_clock
_hostname: The hostname of the server creating the event
_signing_key: The signing key to use to sign the event as the server
"""
_state: StateHandler
_event_auth_handler: "EventAuthHandler"
_store: DataStore
_clock: Clock
_hostname: str
_signing_key: SigningKey
room_version: RoomVersion
room_id: str
type: str
sender: str
content: JsonDict = attr.Factory(dict)
unsigned: JsonDict = 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: Optional[str] = None
_redacts: Optional[str] = None
_origin_server_ts: Optional[int] = None
internal_metadata: _EventInternalMetadata = attr.Factory(
lambda: _EventInternalMetadata({})
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)
@property
def state_key(self) -> str:
if self._state_key is not None:
return self._state_key
raise AttributeError("state_key")
def is_state(self) -> bool:
return self._state_key is not None
async def build(
self,
prev_event_ids: List[str],
auth_event_ids: Optional[List[str]],
depth: Optional[int] = None,
) -> EventBase:
"""Transform into a fully signed and hashed event
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Args:
prev_event_ids: The event IDs to use as the prev events
auth_event_ids: The event IDs to use as the auth events.
Should normally be set to None, which will cause them to be calculated
based on the room state at the prev_events.
depth: Override the depth used to order the event in the DAG.
Should normally be set to None, which will cause the depth to be calculated
based on the prev_events.
Returns:
The signed and hashed event.
"""
if auth_event_ids is None:
state_ids = await self._state.compute_state_after_events(
self.room_id,
prev_event_ids,
state_filter=StateFilter.from_types(
auth_types_for_event(self.room_version, self)
),
)
auth_event_ids = self._event_auth_handler.compute_auth_events(
self, state_ids
)
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format_version = self.room_version.event_format
# The types of auth/prev events changes between event versions.
prev_events: Union[List[str], List[Tuple[str, Dict[str, str]]]]
auth_events: Union[List[str], List[Tuple[str, Dict[str, str]]]]
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if format_version == EventFormatVersions.V1:
auth_events = await self._store.add_event_hashes(auth_event_ids)
prev_events = await self._store.add_event_hashes(prev_event_ids)
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else:
auth_events = auth_event_ids
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prev_events = prev_event_ids
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# Otherwise, progress the depth as normal
if depth is None:
(
_,
most_recent_prev_event_depth,
) = await self._store.get_max_depth_of(prev_event_ids)
depth = most_recent_prev_event_depth + 1
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# 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)
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event_dict: Dict[str, Any] = {
"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
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if self._redacts is not None:
event_dict["redacts"] = self._redacts
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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(),
)
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class EventBuilderFactory:
def __init__(self, hs: "HomeServer"):
self.clock = hs.get_clock()
self.hostname = hs.hostname
self.signing_key = hs.signing_key
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self.store = hs.get_datastores().main
self.state = hs.get_state_handler()
self._event_auth_handler = hs.get_event_auth_handler()
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def for_room_version(
self, room_version: RoomVersion, key_values: dict
) -> EventBuilder:
"""Generate an event builder appropriate for the given room version
Args:
room_version:
Version of the room that we're creating an event builder for
key_values: Fields used as the basis of the new event
Returns:
EventBuilder
"""
return EventBuilder(
store=self.store,
state=self.state,
event_auth_handler=self._event_auth_handler,
clock=self.clock,
hostname=self.hostname,
signing_key=self.signing_key,
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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),
)
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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:
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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())
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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: Clock, hostname: str) -> str:
"""Create a new event ID
Args:
clock
hostname: The server name for the event ID
Returns:
The new event ID
"""
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global _event_id_counter
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i = str(_event_id_counter)
_event_id_counter += 1
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local_part = str(int(clock.time())) + i + random_string(5)
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e_id = EventID(local_part, hostname)
return e_id.to_string()