290 lines
11 KiB
Python
290 lines
11 KiB
Python
# -*- coding: utf-8 -*-
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# Copyright 2017, 2018 New Vector Ltd
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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import logging
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from six import iteritems
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from twisted.internet import defer
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from synapse.api.errors import RoomKeysVersionError, StoreError, SynapseError
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from synapse.util.async_helpers import Linearizer
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logger = logging.getLogger(__name__)
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class E2eRoomKeysHandler(object):
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"""
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Implements an optional realtime backup mechanism for encrypted E2E megolm room keys.
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This gives a way for users to store and recover their megolm keys if they lose all
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their clients. It should also extend easily to future room key mechanisms.
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The actual payload of the encrypted keys is completely opaque to the handler.
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"""
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def __init__(self, hs):
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self.store = hs.get_datastore()
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# Used to lock whenever a client is uploading key data. This prevents collisions
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# between clients trying to upload the details of a new session, given all
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# clients belonging to a user will receive and try to upload a new session at
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# roughly the same time. Also used to lock out uploads when the key is being
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# changed.
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self._upload_linearizer = Linearizer("upload_room_keys_lock")
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@defer.inlineCallbacks
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def get_room_keys(self, user_id, version, room_id=None, session_id=None):
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"""Bulk get the E2E room keys for a given backup, optionally filtered to a given
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room, or a given session.
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See EndToEndRoomKeyStore.get_e2e_room_keys for full details.
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Args:
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user_id(str): the user whose keys we're getting
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version(str): the version ID of the backup we're getting keys from
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room_id(string): room ID to get keys for, for None to get keys for all rooms
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session_id(string): session ID to get keys for, for None to get keys for all
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sessions
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Returns:
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A deferred list of dicts giving the session_data and message metadata for
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these room keys.
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"""
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# we deliberately take the lock to get keys so that changing the version
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# works atomically
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with (yield self._upload_linearizer.queue(user_id)):
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results = yield self.store.get_e2e_room_keys(
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user_id, version, room_id, session_id
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)
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if results['rooms'] == {}:
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raise SynapseError(404, "No room_keys found")
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defer.returnValue(results)
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@defer.inlineCallbacks
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def delete_room_keys(self, user_id, version, room_id=None, session_id=None):
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"""Bulk delete the E2E room keys for a given backup, optionally filtered to a given
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room or a given session.
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See EndToEndRoomKeyStore.delete_e2e_room_keys for full details.
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Args:
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user_id(str): the user whose backup we're deleting
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version(str): the version ID of the backup we're deleting
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room_id(string): room ID to delete keys for, for None to delete keys for all
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rooms
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session_id(string): session ID to delete keys for, for None to delete keys
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for all sessions
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Returns:
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A deferred of the deletion transaction
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"""
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# lock for consistency with uploading
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with (yield self._upload_linearizer.queue(user_id)):
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yield self.store.delete_e2e_room_keys(user_id, version, room_id, session_id)
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@defer.inlineCallbacks
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def upload_room_keys(self, user_id, version, room_keys):
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"""Bulk upload a list of room keys into a given backup version, asserting
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that the given version is the current backup version. room_keys are merged
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into the current backup as described in RoomKeysServlet.on_PUT().
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Args:
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user_id(str): the user whose backup we're setting
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version(str): the version ID of the backup we're updating
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room_keys(dict): a nested dict describing the room_keys we're setting:
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{
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"rooms": {
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"!abc:matrix.org": {
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"sessions": {
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"c0ff33": {
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"first_message_index": 1,
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"forwarded_count": 1,
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"is_verified": false,
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"session_data": "SSBBTSBBIEZJU0gK"
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}
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}
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}
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}
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}
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Raises:
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SynapseError: with code 404 if there are no versions defined
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RoomKeysVersionError: if the uploaded version is not the current version
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"""
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# TODO: Validate the JSON to make sure it has the right keys.
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# XXX: perhaps we should use a finer grained lock here?
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with (yield self._upload_linearizer.queue(user_id)):
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# Check that the version we're trying to upload is the current version
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try:
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version_info = yield self.store.get_e2e_room_keys_version_info(user_id)
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except StoreError as e:
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if e.code == 404:
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raise SynapseError(404, "Version '%s' not found" % (version,))
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else:
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raise
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if version_info['version'] != version:
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# Check that the version we're trying to upload actually exists
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try:
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version_info = yield self.store.get_e2e_room_keys_version_info(
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user_id, version,
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)
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# if we get this far, the version must exist
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raise RoomKeysVersionError(current_version=version_info['version'])
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except StoreError as e:
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if e.code == 404:
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raise SynapseError(404, "Version '%s' not found" % (version,))
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else:
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raise
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# go through the room_keys.
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# XXX: this should/could be done concurrently, given we're in a lock.
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for room_id, room in iteritems(room_keys['rooms']):
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for session_id, session in iteritems(room['sessions']):
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yield self._upload_room_key(
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user_id, version, room_id, session_id, session
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)
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@defer.inlineCallbacks
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def _upload_room_key(self, user_id, version, room_id, session_id, room_key):
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"""Upload a given room_key for a given room and session into a given
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version of the backup. Merges the key with any which might already exist.
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Args:
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user_id(str): the user whose backup we're setting
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version(str): the version ID of the backup we're updating
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room_id(str): the ID of the room whose keys we're setting
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session_id(str): the session whose room_key we're setting
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room_key(dict): the room_key being set
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"""
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# get the room_key for this particular row
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current_room_key = None
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try:
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current_room_key = yield self.store.get_e2e_room_key(
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user_id, version, room_id, session_id
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)
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except StoreError as e:
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if e.code == 404:
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pass
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else:
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raise
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if self._should_replace_room_key(current_room_key, room_key):
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yield self.store.set_e2e_room_key(
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user_id, version, room_id, session_id, room_key
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)
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@staticmethod
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def _should_replace_room_key(current_room_key, room_key):
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"""
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Determine whether to replace a given current_room_key (if any)
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with a newly uploaded room_key backup
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Args:
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current_room_key (dict): Optional, the current room_key dict if any
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room_key (dict): The new room_key dict which may or may not be fit to
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replace the current_room_key
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Returns:
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True if current_room_key should be replaced by room_key in the backup
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"""
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if current_room_key:
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# spelt out with if/elifs rather than nested boolean expressions
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# purely for legibility.
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if room_key['is_verified'] and not current_room_key['is_verified']:
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return True
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elif (
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room_key['first_message_index'] <
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current_room_key['first_message_index']
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):
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return True
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elif room_key['forwarded_count'] < current_room_key['forwarded_count']:
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return True
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else:
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return False
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return True
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@defer.inlineCallbacks
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def create_version(self, user_id, version_info):
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"""Create a new backup version. This automatically becomes the new
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backup version for the user's keys; previous backups will no longer be
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writeable to.
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Args:
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user_id(str): the user whose backup version we're creating
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version_info(dict): metadata about the new version being created
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{
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"algorithm": "m.megolm_backup.v1",
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"auth_data": "dGhpcyBzaG91bGQgYWN0dWFsbHkgYmUgZW5jcnlwdGVkIGpzb24K"
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}
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Returns:
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A deferred of a string that gives the new version number.
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"""
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# TODO: Validate the JSON to make sure it has the right keys.
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# lock everyone out until we've switched version
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with (yield self._upload_linearizer.queue(user_id)):
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new_version = yield self.store.create_e2e_room_keys_version(
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user_id, version_info
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)
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defer.returnValue(new_version)
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@defer.inlineCallbacks
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def get_version_info(self, user_id, version=None):
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"""Get the info about a given version of the user's backup
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Args:
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user_id(str): the user whose current backup version we're querying
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version(str): Optional; if None gives the most recent version
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otherwise a historical one.
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Raises:
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StoreError: code 404 if the requested backup version doesn't exist
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Returns:
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A deferred of a info dict that gives the info about the new version.
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{
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"version": "1234",
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"algorithm": "m.megolm_backup.v1",
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"auth_data": "dGhpcyBzaG91bGQgYWN0dWFsbHkgYmUgZW5jcnlwdGVkIGpzb24K"
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}
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"""
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with (yield self._upload_linearizer.queue(user_id)):
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res = yield self.store.get_e2e_room_keys_version_info(user_id, version)
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defer.returnValue(res)
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@defer.inlineCallbacks
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def delete_version(self, user_id, version=None):
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"""Deletes a given version of the user's e2e_room_keys backup
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Args:
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user_id(str): the user whose current backup version we're deleting
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version(str): the version id of the backup being deleted
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Raises:
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StoreError: code 404 if this backup version doesn't exist
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"""
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with (yield self._upload_linearizer.queue(user_id)):
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yield self.store.delete_e2e_room_keys_version(user_id, version)
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