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Diffstat (limited to 'synapse/handlers/e2e_room_keys.py')
| -rw-r--r-- | synapse/handlers/e2e_room_keys.py | 289 |
1 files changed, 289 insertions, 0 deletions
diff --git a/synapse/handlers/e2e_room_keys.py b/synapse/handlers/e2e_room_keys.py new file mode 100644 index 0000000000..5edb3cfe04 --- /dev/null +++ b/synapse/handlers/e2e_room_keys.py @@ -0,0 +1,289 @@ +# -*- coding: utf-8 -*- +# Copyright 2017, 2018 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 six import iteritems + +from twisted.internet import defer + +from synapse.api.errors import RoomKeysVersionError, StoreError, SynapseError +from synapse.util.async_helpers 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. + + Args: + user_id(str): the user whose keys we're getting + version(str): the version ID of the backup we're getting keys from + room_id(string): room ID to get keys for, for None to get keys for all rooms + session_id(string): session ID to get keys for, for None to get keys for all + sessions + 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 + ) + + if results['rooms'] == {}: + raise SynapseError(404, "No room_keys found") + + 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. + + Args: + user_id(str): the user whose backup we're deleting + version(str): the version ID of the backup we're deleting + room_id(string): room ID to delete keys for, for None to delete keys for all + rooms + session_id(string): session ID to delete keys for, for None to delete keys + for all sessions + 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 + try: + version_info = yield self.store.get_e2e_room_keys_version_info(user_id) + except StoreError as e: + if e.code == 404: + raise SynapseError(404, "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 = yield 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 SynapseError(404, "Version '%s' not found" % (version,)) + else: + raise + + # go through the room_keys. + # XXX: this should/could be done concurrently, given we're in a lock. + for room_id, room in iteritems(room_keys['rooms']): + for session_id, session in iteritems(room['sessions']): + yield self._upload_room_key( + user_id, version, room_id, session_id, session + ) + + @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 + + if self._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']: + 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 + + @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_version_info(self, user_id, version=None): + """Get the info about a given version of the user's backup + + Args: + user_id(str): the user whose current backup version we're querying + version(str): Optional; if None gives the most recent version + otherwise a historical one. + Raises: + StoreError: code 404 if the requested backup version doesn't exist + Returns: + A deferred of a info dict that gives the info about the new version. + + { + "version": "1234", + "algorithm": "m.megolm_backup.v1", + "auth_data": "dGhpcyBzaG91bGQgYWN0dWFsbHkgYmUgZW5jcnlwdGVkIGpzb24K" + } + """ + + with (yield self._upload_linearizer.queue(user_id)): + res = yield self.store.get_e2e_room_keys_version_info(user_id, version) + defer.returnValue(res) + + @defer.inlineCallbacks + def delete_version(self, user_id, version=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: + 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) |