MatrixSynapse/synapse/handlers/e2e_room_keys.py

430 lines
16 KiB
Python

# -*- coding: utf-8 -*-
# Copyright 2017, 2018 New Vector Ltd
# Copyright 2019 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 logging
from typing import TYPE_CHECKING, List, Optional
from synapse.api.errors import (
Codes,
NotFoundError,
RoomKeysVersionError,
StoreError,
SynapseError,
)
from synapse.logging.opentracing import log_kv, trace
from synapse.types import JsonDict
from synapse.util.async_helpers import Linearizer
if TYPE_CHECKING:
from synapse.server import HomeServer
logger = logging.getLogger(__name__)
class E2eRoomKeysHandler:
"""
Implements an optional realtime backup mechanism for encrypted E2E megolm room keys.
This gives a way for users to store and recover their megolm keys if they lose all
their clients. It should also extend easily to future room key mechanisms.
The actual payload of the encrypted keys is completely opaque to the handler.
"""
def __init__(self, hs: "HomeServer"):
self.store = hs.get_datastore()
# Used to lock whenever a client is uploading key data. This prevents collisions
# between clients trying to upload the details of a new session, given all
# clients belonging to a user will receive and try to upload a new session at
# roughly the same time. Also used to lock out uploads when the key is being
# changed.
self._upload_linearizer = Linearizer("upload_room_keys_lock")
@trace
async def get_room_keys(
self,
user_id: str,
version: str,
room_id: Optional[str] = None,
session_id: Optional[str] = None,
) -> List[JsonDict]:
"""Bulk get the E2E room keys for a given backup, optionally filtered to a given
room, or a given session.
See EndToEndRoomKeyStore.get_e2e_room_keys for full details.
Args:
user_id: the user whose keys we're getting
version: the version ID of the backup we're getting keys from
room_id: room ID to get keys for, for None to get keys for all rooms
session_id: session ID to get keys for, for None to get keys for all
sessions
Raises:
NotFoundError: if the backup version does not exist
Returns:
A list of dicts giving the session_data and message metadata for
these room keys.
"""
# we deliberately take the lock to get keys so that changing the version
# works atomically
with (await self._upload_linearizer.queue(user_id)):
# make sure the backup version exists
try:
await self.store.get_e2e_room_keys_version_info(user_id, version)
except StoreError as e:
if e.code == 404:
raise NotFoundError("Unknown backup version")
else:
raise
results = await self.store.get_e2e_room_keys(
user_id, version, room_id, session_id
)
log_kv(results)
return results
@trace
async def delete_room_keys(
self,
user_id: str,
version: str,
room_id: Optional[str] = None,
session_id: Optional[str] = None,
) -> JsonDict:
"""Bulk delete the E2E room keys for a given backup, optionally filtered to a given
room or a given session.
See EndToEndRoomKeyStore.delete_e2e_room_keys for full details.
Args:
user_id: the user whose backup we're deleting
version: the version ID of the backup we're deleting
room_id: room ID to delete keys for, for None to delete keys for all
rooms
session_id: session ID to delete keys for, for None to delete keys
for all sessions
Raises:
NotFoundError: if the backup version does not exist
Returns:
A dict containing the count and etag for the backup version
"""
# lock for consistency with uploading
with (await self._upload_linearizer.queue(user_id)):
# make sure the backup version exists
try:
version_info = await self.store.get_e2e_room_keys_version_info(
user_id, version
)
except StoreError as e:
if e.code == 404:
raise NotFoundError("Unknown backup version")
else:
raise
await self.store.delete_e2e_room_keys(user_id, version, room_id, session_id)
version_etag = version_info["etag"] + 1
await self.store.update_e2e_room_keys_version(
user_id, version, None, version_etag
)
count = await self.store.count_e2e_room_keys(user_id, version)
return {"etag": str(version_etag), "count": count}
@trace
async def upload_room_keys(
self, user_id: str, version: str, room_keys: JsonDict
) -> JsonDict:
"""Bulk upload a list of room keys into a given backup version, asserting
that the given version is the current backup version. room_keys are merged
into the current backup as described in RoomKeysServlet.on_PUT().
Args:
user_id: the user whose backup we're setting
version: the version ID of the backup we're updating
room_keys: a nested dict describing the room_keys we're setting:
{
"rooms": {
"!abc:matrix.org": {
"sessions": {
"c0ff33": {
"first_message_index": 1,
"forwarded_count": 1,
"is_verified": false,
"session_data": "SSBBTSBBIEZJU0gK"
}
}
}
}
}
Returns:
A dict containing the count and etag for the backup version
Raises:
NotFoundError: if there are no versions defined
RoomKeysVersionError: if the uploaded version is not the current version
"""
# TODO: Validate the JSON to make sure it has the right keys.
# XXX: perhaps we should use a finer grained lock here?
with (await self._upload_linearizer.queue(user_id)):
# Check that the version we're trying to upload is the current version
try:
version_info = await self.store.get_e2e_room_keys_version_info(user_id)
except StoreError as e:
if e.code == 404:
raise NotFoundError("Version '%s' not found" % (version,))
else:
raise
if version_info["version"] != version:
# Check that the version we're trying to upload actually exists
try:
version_info = await self.store.get_e2e_room_keys_version_info(
user_id, version
)
# if we get this far, the version must exist
raise RoomKeysVersionError(current_version=version_info["version"])
except StoreError as e:
if e.code == 404:
raise NotFoundError("Version '%s' not found" % (version,))
else:
raise
# Fetch any existing room keys for the sessions that have been
# submitted. Then compare them with the submitted keys. If the
# key is new, insert it; if the key should be updated, then update
# it; otherwise, drop it.
existing_keys = await self.store.get_e2e_room_keys_multi(
user_id, version, room_keys["rooms"]
)
to_insert = [] # batch the inserts together
changed = False # if anything has changed, we need to update the etag
for room_id, room in room_keys["rooms"].items():
for session_id, room_key in room["sessions"].items():
if not isinstance(room_key["is_verified"], bool):
msg = (
"is_verified must be a boolean in keys for session %s in"
"room %s" % (session_id, room_id)
)
raise SynapseError(400, msg, Codes.INVALID_PARAM)
log_kv(
{
"message": "Trying to upload room key",
"room_id": room_id,
"session_id": session_id,
"user_id": user_id,
}
)
current_room_key = existing_keys.get(room_id, {}).get(session_id)
if current_room_key:
if self._should_replace_room_key(current_room_key, room_key):
log_kv({"message": "Replacing room key."})
# updates are done one at a time in the DB, so send
# updates right away rather than batching them up,
# like we do with the inserts
await self.store.update_e2e_room_key(
user_id, version, room_id, session_id, room_key
)
changed = True
else:
log_kv({"message": "Not replacing room_key."})
else:
log_kv(
{
"message": "Room key not found.",
"room_id": room_id,
"user_id": user_id,
}
)
log_kv({"message": "Replacing room key."})
to_insert.append((room_id, session_id, room_key))
changed = True
if len(to_insert):
await self.store.add_e2e_room_keys(user_id, version, to_insert)
version_etag = version_info["etag"]
if changed:
version_etag = version_etag + 1
await self.store.update_e2e_room_keys_version(
user_id, version, None, version_etag
)
count = await self.store.count_e2e_room_keys(user_id, version)
return {"etag": str(version_etag), "count": count}
@staticmethod
def _should_replace_room_key(
current_room_key: Optional[JsonDict], room_key: JsonDict
) -> bool:
"""
Determine whether to replace a given current_room_key (if any)
with a newly uploaded room_key backup
Args:
current_room_key: Optional, the current room_key dict if any
room_key : The new room_key dict which may or may not be fit to
replace the current_room_key
Returns:
True if current_room_key should be replaced by room_key in the backup
"""
if current_room_key:
# spelt out with if/elifs rather than nested boolean expressions
# purely for legibility.
if room_key["is_verified"] and not current_room_key["is_verified"]:
return True
elif (
room_key["first_message_index"]
< current_room_key["first_message_index"]
):
return True
elif room_key["forwarded_count"] < current_room_key["forwarded_count"]:
return True
else:
return False
return True
@trace
async def create_version(self, user_id: str, version_info: JsonDict) -> str:
"""Create a new backup version. This automatically becomes the new
backup version for the user's keys; previous backups will no longer be
writeable to.
Args:
user_id: the user whose backup version we're creating
version_info: metadata about the new version being created
{
"algorithm": "m.megolm_backup.v1",
"auth_data": "dGhpcyBzaG91bGQgYWN0dWFsbHkgYmUgZW5jcnlwdGVkIGpzb24K"
}
Returns:
The new version number.
"""
# TODO: Validate the JSON to make sure it has the right keys.
# lock everyone out until we've switched version
with (await self._upload_linearizer.queue(user_id)):
new_version = await self.store.create_e2e_room_keys_version(
user_id, version_info
)
return new_version
async def get_version_info(
self, user_id: str, version: Optional[str] = None
) -> JsonDict:
"""Get the info about a given version of the user's backup
Args:
user_id: the user whose current backup version we're querying
version: Optional; if None gives the most recent version
otherwise a historical one.
Raises:
NotFoundError: if the requested backup version doesn't exist
Returns:
A info dict that gives the info about the new version.
{
"version": "1234",
"algorithm": "m.megolm_backup.v1",
"auth_data": "dGhpcyBzaG91bGQgYWN0dWFsbHkgYmUgZW5jcnlwdGVkIGpzb24K"
}
"""
with (await self._upload_linearizer.queue(user_id)):
try:
res = await self.store.get_e2e_room_keys_version_info(user_id, version)
except StoreError as e:
if e.code == 404:
raise NotFoundError("Unknown backup version")
else:
raise
res["count"] = await self.store.count_e2e_room_keys(user_id, res["version"])
res["etag"] = str(res["etag"])
return res
@trace
async def delete_version(self, user_id: str, version: Optional[str] = None) -> None:
"""Deletes a given version of the user's e2e_room_keys backup
Args:
user_id(str): the user whose current backup version we're deleting
version(str): the version id of the backup being deleted
Raises:
NotFoundError: if this backup version doesn't exist
"""
with (await self._upload_linearizer.queue(user_id)):
try:
await self.store.delete_e2e_room_keys_version(user_id, version)
except StoreError as e:
if e.code == 404:
raise NotFoundError("Unknown backup version")
else:
raise
@trace
async def update_version(
self, user_id: str, version: str, version_info: JsonDict
) -> JsonDict:
"""Update the info about a given version of the user's backup
Args:
user_id: the user whose current backup version we're updating
version: the backup version we're updating
version_info: the new information about the backup
Raises:
NotFoundError: if the requested backup version doesn't exist
Returns:
An empty dict.
"""
if "version" not in version_info:
version_info["version"] = version
elif version_info["version"] != version:
raise SynapseError(
400, "Version in body does not match", Codes.INVALID_PARAM
)
with (await self._upload_linearizer.queue(user_id)):
try:
old_info = await self.store.get_e2e_room_keys_version_info(
user_id, version
)
except StoreError as e:
if e.code == 404:
raise NotFoundError("Unknown backup version")
else:
raise
if old_info["algorithm"] != version_info["algorithm"]:
raise SynapseError(400, "Algorithm does not match", Codes.INVALID_PARAM)
await self.store.update_e2e_room_keys_version(
user_id, version, version_info
)
return {}