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# -*- coding: utf-8 -*-
# Copyright 2017 New Vector 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 logging
from twisted.internet import defer
from synapse.api.errors import StoreError, SynapseError, RoomKeysVersionError
from synapse.util.async import Linearizer
logger = logging.getLogger(__name__)
class E2eRoomKeysHandler(object):
"""
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):
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")
@defer.inlineCallbacks
def get_room_keys(self, user_id, version, room_id=None, session_id=None):
"""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.
Returns:
A deferred 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 (yield self._upload_linearizer.queue(user_id)):
results = yield self.store.get_e2e_room_keys(
user_id, version, room_id, session_id
)
defer.returnValue(results)
@defer.inlineCallbacks
def delete_room_keys(self, user_id, version, room_id=None, session_id=None):
"""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.
Returns:
A deferred of the deletion transaction
"""
# lock for consistency with uploading
with (yield self._upload_linearizer.queue(user_id)):
yield self.store.delete_e2e_room_keys(user_id, version, room_id, session_id)
@defer.inlineCallbacks
def upload_room_keys(self, user_id, version, room_keys):
"""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(str): the user whose backup we're setting
version(str): the version ID of the backup we're updating
room_keys(dict): 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"
}
}
}
}
}
Raises:
SynapseError: with code 404 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 (yield self._upload_linearizer.queue(user_id)):
# Check that the version we're trying to upload is the current version
version_info = yield self.get_current_version_info(user_id)
except StoreError as e:
if e.code == 404:
raise SynapseError(404, "Version '%s' not found" % (version,))
else:
raise e
if version_info['version'] != version:
raise RoomKeysVersionError(current_version=version_info.version)
# go through the room_keys.
# XXX: this should/could be done concurrently, given we're in a lock.
for room_id, room in room_keys['rooms'].iteritems():
for session_id, session in room['sessions'].iteritems():
room_key = session[session_id]
yield self._upload_room_key(
user_id, version, room_id, session_id, room_key
)
@defer.inlineCallbacks
def _upload_room_key(self, user_id, version, room_id, session_id, room_key):
"""Upload a given room_key for a given room and session into a given
version of the backup. Merges the key with any which might already exist.
Args:
user_id(str): the user whose backup we're setting
version(str): the version ID of the backup we're updating
room_id(str): the ID of the room whose keys we're setting
session_id(str): the session whose room_key we're setting
room_key(dict): the room_key being set
"""
# get the room_key for this particular row
current_room_key = None
try:
current_room_key = yield self.store.get_e2e_room_key(
user_id, version, room_id, session_id
)
except StoreError as e:
if e.code == 404:
pass
else:
raise e
if E2eRoomKeysHandler._should_replace_room_key(current_room_key, room_key):
yield self.store.set_e2e_room_key(
user_id, version, room_id, session_id, room_key
)
@staticmethod
def _should_replace_room_key(current_room_key, room_key):
"""
Determine whether to replace a given current_room_key (if any)
with a newly uploaded room_key backup
Args:
current_room_key (dict): Optional, the current room_key dict if any
room_key (dict): 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']:
pass
elif (
room_key['first_message_index'] <
current_room_key['first_message_index']
):
pass
elif room_key['forwarded_count'] < current_room_key['forwarded_count']:
pass
else:
return False
return True
@defer.inlineCallbacks
def create_version(self, user_id, version_info):
"""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(str): the user whose backup version we're creating
version_info(dict): metadata about the new version being created
{
"algorithm": "m.megolm_backup.v1",
"auth_data": "dGhpcyBzaG91bGQgYWN0dWFsbHkgYmUgZW5jcnlwdGVkIGpzb24K"
}
Returns:
A deferred of a string that gives 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 (yield self._upload_linearizer.queue(user_id)):
new_version = yield self.store.create_e2e_room_keys_version(
user_id, version_info
)
defer.returnValue(new_version)
@defer.inlineCallbacks
def get_current_version_info(self, user_id):
"""Get the user's current backup version.
Args:
user_id(str): the user whose current backup version we're querying
Raises:
StoreError: code 404 if there is no current backup version
Returns:
A deferred of a info dict that gives the info about the new version.
{
"algorithm": "m.megolm_backup.v1",
"auth_data": "dGhpcyBzaG91bGQgYWN0dWFsbHkgYmUgZW5jcnlwdGVkIGpzb24K"
}
"""
with (yield self._upload_linearizer.queue(user_id)):
results = yield self.store.get_e2e_room_keys_version_info(user_id)
defer.returnValue(results)
@defer.inlineCallbacks
def delete_version(self, user_id, version):
"""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:
StoreError: code 404 if this backup version doesn't exist
"""
with (yield self._upload_linearizer.queue(user_id)):
yield self.store.delete_e2e_room_keys_version(user_id, version)
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