# -*- coding: utf-8 -*- # Copyright 2016 OpenMarket Ltd # Copyright 2018-2019 New Vector Ltd # Copyright 2019 The 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 Dict, List, Optional, Tuple import attr from canonicaljson import encode_canonical_json, json from signedjson.key import VerifyKey, decode_verify_key_bytes from signedjson.sign import SignatureVerifyException, verify_signed_json from unpaddedbase64 import decode_base64 from twisted.internet import defer from synapse.api.errors import CodeMessageException, Codes, NotFoundError, SynapseError from synapse.logging.context import make_deferred_yieldable, run_in_background from synapse.logging.opentracing import log_kv, set_tag, tag_args, trace from synapse.replication.http.devices import ReplicationUserDevicesResyncRestServlet from synapse.types import ( UserID, get_domain_from_id, get_verify_key_from_cross_signing_key, ) from synapse.util import unwrapFirstError from synapse.util.async_helpers import Linearizer from synapse.util.caches.expiringcache import ExpiringCache from synapse.util.retryutils import NotRetryingDestination logger = logging.getLogger(__name__) class E2eKeysHandler(object): def __init__(self, hs): self.store = hs.get_datastore() self.federation = hs.get_federation_client() self.device_handler = hs.get_device_handler() self.is_mine = hs.is_mine self.clock = hs.get_clock() self._edu_updater = SigningKeyEduUpdater(hs, self) federation_registry = hs.get_federation_registry() self._is_master = hs.config.worker_app is None if not self._is_master: self._user_device_resync_client = ReplicationUserDevicesResyncRestServlet.make_client( hs ) else: # Only register this edu handler on master as it requires writing # device updates to the db # # FIXME: switch to m.signing_key_update when MSC1756 is merged into the spec federation_registry.register_edu_handler( "org.matrix.signing_key_update", self._edu_updater.incoming_signing_key_update, ) # doesn't really work as part of the generic query API, because the # query request requires an object POST, but we abuse the # "query handler" interface. federation_registry.register_query_handler( "client_keys", self.on_federation_query_client_keys ) @trace async def query_devices(self, query_body, timeout, from_user_id): """ Handle a device key query from a client { "device_keys": { "<user_id>": ["<device_id>"] } } -> { "device_keys": { "<user_id>": { "<device_id>": { ... } } } } Args: from_user_id (str): the user making the query. This is used when adding cross-signing signatures to limit what signatures users can see. """ device_keys_query = query_body.get("device_keys", {}) # separate users by domain. # make a map from domain to user_id to device_ids local_query = {} remote_queries = {} for user_id, device_ids in device_keys_query.items(): # we use UserID.from_string to catch invalid user ids if self.is_mine(UserID.from_string(user_id)): local_query[user_id] = device_ids else: remote_queries[user_id] = device_ids set_tag("local_key_query", local_query) set_tag("remote_key_query", remote_queries) # First get local devices. failures = {} results = {} if local_query: local_result = await self.query_local_devices(local_query) for user_id, keys in local_result.items(): if user_id in local_query: results[user_id] = keys # Now attempt to get any remote devices from our local cache. remote_queries_not_in_cache = {} if remote_queries: query_list = [] for user_id, device_ids in remote_queries.items(): if device_ids: query_list.extend((user_id, device_id) for device_id in device_ids) else: query_list.append((user_id, None)) ( user_ids_not_in_cache, remote_results, ) = await self.store.get_user_devices_from_cache(query_list) for user_id, devices in remote_results.items(): user_devices = results.setdefault(user_id, {}) for device_id, device in devices.items(): keys = device.get("keys", None) device_display_name = device.get("device_display_name", None) if keys: result = dict(keys) unsigned = result.setdefault("unsigned", {}) if device_display_name: unsigned["device_display_name"] = device_display_name user_devices[device_id] = result for user_id in user_ids_not_in_cache: domain = get_domain_from_id(user_id) r = remote_queries_not_in_cache.setdefault(domain, {}) r[user_id] = remote_queries[user_id] # Get cached cross-signing keys cross_signing_keys = await self.get_cross_signing_keys_from_cache( device_keys_query, from_user_id ) # Now fetch any devices that we don't have in our cache @trace async def do_remote_query(destination): """This is called when we are querying the device list of a user on a remote homeserver and their device list is not in the device list cache. If we share a room with this user and we're not querying for specific user we will update the cache with their device list. """ destination_query = remote_queries_not_in_cache[destination] # We first consider whether we wish to update the device list cache with # the users device list. We want to track a user's devices when the # authenticated user shares a room with the queried user and the query # has not specified a particular device. # If we update the cache for the queried user we remove them from further # queries. We use the more efficient batched query_client_keys for all # remaining users user_ids_updated = [] for (user_id, device_list) in destination_query.items(): if user_id in user_ids_updated: continue if device_list: continue room_ids = await self.store.get_rooms_for_user(user_id) if not room_ids: continue # We've decided we're sharing a room with this user and should # probably be tracking their device lists. However, we haven't # done an initial sync on the device list so we do it now. try: if self._is_master: user_devices = await self.device_handler.device_list_updater.user_device_resync( user_id ) else: user_devices = await self._user_device_resync_client( user_id=user_id ) user_devices = user_devices["devices"] user_results = results.setdefault(user_id, {}) for device in user_devices: user_results[device["device_id"]] = device["keys"] user_ids_updated.append(user_id) except Exception as e: failures[destination] = _exception_to_failure(e) if len(destination_query) == len(user_ids_updated): # We've updated all the users in the query and we do not need to # make any further remote calls. return # Remove all the users from the query which we have updated for user_id in user_ids_updated: destination_query.pop(user_id) try: remote_result = await self.federation.query_client_keys( destination, {"device_keys": destination_query}, timeout=timeout ) for user_id, keys in remote_result["device_keys"].items(): if user_id in destination_query: results[user_id] = keys if "master_keys" in remote_result: for user_id, key in remote_result["master_keys"].items(): if user_id in destination_query: cross_signing_keys["master_keys"][user_id] = key if "self_signing_keys" in remote_result: for user_id, key in remote_result["self_signing_keys"].items(): if user_id in destination_query: cross_signing_keys["self_signing_keys"][user_id] = key except Exception as e: failure = _exception_to_failure(e) failures[destination] = failure set_tag("error", True) set_tag("reason", failure) await make_deferred_yieldable( defer.gatherResults( [ run_in_background(do_remote_query, destination) for destination in remote_queries_not_in_cache ], consumeErrors=True, ).addErrback(unwrapFirstError) ) ret = {"device_keys": results, "failures": failures} ret.update(cross_signing_keys) return ret async def get_cross_signing_keys_from_cache( self, query, from_user_id ) -> Dict[str, Dict[str, dict]]: """Get cross-signing keys for users from the database Args: query (Iterable[string]) an iterable of user IDs. A dict whose keys are user IDs satisfies this, so the query format used for query_devices can be used here. from_user_id (str): the user making the query. This is used when adding cross-signing signatures to limit what signatures users can see. Returns: A map from (master_keys|self_signing_keys|user_signing_keys) -> user_id -> key """ master_keys = {} self_signing_keys = {} user_signing_keys = {} user_ids = list(query) keys = await self.store.get_e2e_cross_signing_keys_bulk(user_ids, from_user_id) for user_id, user_info in keys.items(): if user_info is None: continue if "master" in user_info: master_keys[user_id] = user_info["master"] if "self_signing" in user_info: self_signing_keys[user_id] = user_info["self_signing"] if ( from_user_id in keys and keys[from_user_id] is not None and "user_signing" in keys[from_user_id] ): # users can see other users' master and self-signing keys, but can # only see their own user-signing keys user_signing_keys[from_user_id] = keys[from_user_id]["user_signing"] return { "master_keys": master_keys, "self_signing_keys": self_signing_keys, "user_signing_keys": user_signing_keys, } @trace async def query_local_devices( self, query: Dict[str, Optional[List[str]]] ) -> Dict[str, Dict[str, dict]]: """Get E2E device keys for local users Args: query: map from user_id to a list of devices to query (None for all devices) Returns: A map from user_id -> device_id -> device details """ set_tag("local_query", query) local_query = [] result_dict = {} for user_id, device_ids in query.items(): # we use UserID.from_string to catch invalid user ids if not self.is_mine(UserID.from_string(user_id)): logger.warning("Request for keys for non-local user %s", user_id) log_kv( { "message": "Requested a local key for a user which" " was not local to the homeserver", "user_id": user_id, } ) set_tag("error", True) raise SynapseError(400, "Not a user here") if not device_ids: local_query.append((user_id, None)) else: for device_id in device_ids: local_query.append((user_id, device_id)) # make sure that each queried user appears in the result dict result_dict[user_id] = {} results = await self.store.get_e2e_device_keys(local_query) # Build the result structure for user_id, device_keys in results.items(): for device_id, device_info in device_keys.items(): result_dict[user_id][device_id] = device_info log_kv(results) return result_dict async def on_federation_query_client_keys(self, query_body): """ Handle a device key query from a federated server """ device_keys_query = query_body.get("device_keys", {}) res = await self.query_local_devices(device_keys_query) ret = {"device_keys": res} # add in the cross-signing keys cross_signing_keys = await self.get_cross_signing_keys_from_cache( device_keys_query, None ) ret.update(cross_signing_keys) return ret @trace async def claim_one_time_keys(self, query, timeout): local_query = [] remote_queries = {} for user_id, device_keys in query.get("one_time_keys", {}).items(): # we use UserID.from_string to catch invalid user ids if self.is_mine(UserID.from_string(user_id)): for device_id, algorithm in device_keys.items(): local_query.append((user_id, device_id, algorithm)) else: domain = get_domain_from_id(user_id) remote_queries.setdefault(domain, {})[user_id] = device_keys set_tag("local_key_query", local_query) set_tag("remote_key_query", remote_queries) results = await self.store.claim_e2e_one_time_keys(local_query) json_result = {} failures = {} for user_id, device_keys in results.items(): for device_id, keys in device_keys.items(): for key_id, json_bytes in keys.items(): json_result.setdefault(user_id, {})[device_id] = { key_id: json.loads(json_bytes) } @trace async def claim_client_keys(destination): set_tag("destination", destination) device_keys = remote_queries[destination] try: remote_result = await self.federation.claim_client_keys( destination, {"one_time_keys": device_keys}, timeout=timeout ) for user_id, keys in remote_result["one_time_keys"].items(): if user_id in device_keys: json_result[user_id] = keys except Exception as e: failure = _exception_to_failure(e) failures[destination] = failure set_tag("error", True) set_tag("reason", failure) await make_deferred_yieldable( defer.gatherResults( [ run_in_background(claim_client_keys, destination) for destination in remote_queries ], consumeErrors=True, ) ) logger.info( "Claimed one-time-keys: %s", ",".join( ( "%s for %s:%s" % (key_id, user_id, device_id) for user_id, user_keys in json_result.items() for device_id, device_keys in user_keys.items() for key_id, _ in device_keys.items() ) ), ) log_kv({"one_time_keys": json_result, "failures": failures}) return {"one_time_keys": json_result, "failures": failures} @tag_args async def upload_keys_for_user(self, user_id, device_id, keys): time_now = self.clock.time_msec() # TODO: Validate the JSON to make sure it has the right keys. device_keys = keys.get("device_keys", None) if device_keys: logger.info( "Updating device_keys for device %r for user %s at %d", device_id, user_id, time_now, ) log_kv( { "message": "Updating device_keys for user.", "user_id": user_id, "device_id": device_id, } ) # TODO: Sign the JSON with the server key changed = await self.store.set_e2e_device_keys( user_id, device_id, time_now, device_keys ) if changed: # Only notify about device updates *if* the keys actually changed await self.device_handler.notify_device_update(user_id, [device_id]) else: log_kv({"message": "Not updating device_keys for user", "user_id": user_id}) one_time_keys = keys.get("one_time_keys", None) if one_time_keys: log_kv( { "message": "Updating one_time_keys for device.", "user_id": user_id, "device_id": device_id, } ) await self._upload_one_time_keys_for_user( user_id, device_id, time_now, one_time_keys ) else: log_kv( {"message": "Did not update one_time_keys", "reason": "no keys given"} ) # the device should have been registered already, but it may have been # deleted due to a race with a DELETE request. Or we may be using an # old access_token without an associated device_id. Either way, we # need to double-check the device is registered to avoid ending up with # keys without a corresponding device. await self.device_handler.check_device_registered(user_id, device_id) result = await self.store.count_e2e_one_time_keys(user_id, device_id) set_tag("one_time_key_counts", result) return {"one_time_key_counts": result} async def _upload_one_time_keys_for_user( self, user_id, device_id, time_now, one_time_keys ): logger.info( "Adding one_time_keys %r for device %r for user %r at %d", one_time_keys.keys(), device_id, user_id, time_now, ) # make a list of (alg, id, key) tuples key_list = [] for key_id, key_obj in one_time_keys.items(): algorithm, key_id = key_id.split(":") key_list.append((algorithm, key_id, key_obj)) # First we check if we have already persisted any of the keys. existing_key_map = await self.store.get_e2e_one_time_keys( user_id, device_id, [k_id for _, k_id, _ in key_list] ) new_keys = [] # Keys that we need to insert. (alg, id, json) tuples. for algorithm, key_id, key in key_list: ex_json = existing_key_map.get((algorithm, key_id), None) if ex_json: if not _one_time_keys_match(ex_json, key): raise SynapseError( 400, ( "One time key %s:%s already exists. " "Old key: %s; new key: %r" ) % (algorithm, key_id, ex_json, key), ) else: new_keys.append( (algorithm, key_id, encode_canonical_json(key).decode("ascii")) ) log_kv({"message": "Inserting new one_time_keys.", "keys": new_keys}) await self.store.add_e2e_one_time_keys(user_id, device_id, time_now, new_keys) async def upload_signing_keys_for_user(self, user_id, keys): """Upload signing keys for cross-signing Args: user_id (string): the user uploading the keys keys (dict[string, dict]): the signing keys """ # if a master key is uploaded, then check it. Otherwise, load the # stored master key, to check signatures on other keys if "master_key" in keys: master_key = keys["master_key"] _check_cross_signing_key(master_key, user_id, "master") else: master_key = await self.store.get_e2e_cross_signing_key(user_id, "master") # if there is no master key, then we can't do anything, because all the # other cross-signing keys need to be signed by the master key if not master_key: raise SynapseError(400, "No master key available", Codes.MISSING_PARAM) try: master_key_id, master_verify_key = get_verify_key_from_cross_signing_key( master_key ) except ValueError: if "master_key" in keys: # the invalid key came from the request raise SynapseError(400, "Invalid master key", Codes.INVALID_PARAM) else: # the invalid key came from the database logger.error("Invalid master key found for user %s", user_id) raise SynapseError(500, "Invalid master key") # for the other cross-signing keys, make sure that they have valid # signatures from the master key if "self_signing_key" in keys: self_signing_key = keys["self_signing_key"] _check_cross_signing_key( self_signing_key, user_id, "self_signing", master_verify_key ) if "user_signing_key" in keys: user_signing_key = keys["user_signing_key"] _check_cross_signing_key( user_signing_key, user_id, "user_signing", master_verify_key ) # if everything checks out, then store the keys and send notifications deviceids = [] if "master_key" in keys: await self.store.set_e2e_cross_signing_key(user_id, "master", master_key) deviceids.append(master_verify_key.version) if "self_signing_key" in keys: await self.store.set_e2e_cross_signing_key( user_id, "self_signing", self_signing_key ) try: deviceids.append( get_verify_key_from_cross_signing_key(self_signing_key)[1].version ) except ValueError: raise SynapseError(400, "Invalid self-signing key", Codes.INVALID_PARAM) if "user_signing_key" in keys: await self.store.set_e2e_cross_signing_key( user_id, "user_signing", user_signing_key ) # the signature stream matches the semantics that we want for # user-signing key updates: only the user themselves is notified of # their own user-signing key updates await self.device_handler.notify_user_signature_update(user_id, [user_id]) # master key and self-signing key updates match the semantics of device # list updates: all users who share an encrypted room are notified if len(deviceids): await self.device_handler.notify_device_update(user_id, deviceids) return {} async def upload_signatures_for_device_keys(self, user_id, signatures): """Upload device signatures for cross-signing Args: user_id (string): the user uploading the signatures signatures (dict[string, dict[string, dict]]): map of users to devices to signed keys. This is the submission from the user; an exception will be raised if it is malformed. Returns: dict: response to be sent back to the client. The response will have a "failures" key, which will be a dict mapping users to devices to errors for the signatures that failed. Raises: SynapseError: if the signatures dict is not valid. """ failures = {} # signatures to be stored. Each item will be a SignatureListItem signature_list = [] # split between checking signatures for own user and signatures for # other users, since we verify them with different keys self_signatures = signatures.get(user_id, {}) other_signatures = {k: v for k, v in signatures.items() if k != user_id} self_signature_list, self_failures = await self._process_self_signatures( user_id, self_signatures ) signature_list.extend(self_signature_list) failures.update(self_failures) other_signature_list, other_failures = await self._process_other_signatures( user_id, other_signatures ) signature_list.extend(other_signature_list) failures.update(other_failures) # store the signature, and send the appropriate notifications for sync logger.debug("upload signature failures: %r", failures) await self.store.store_e2e_cross_signing_signatures(user_id, signature_list) self_device_ids = [item.target_device_id for item in self_signature_list] if self_device_ids: await self.device_handler.notify_device_update(user_id, self_device_ids) signed_users = [item.target_user_id for item in other_signature_list] if signed_users: await self.device_handler.notify_user_signature_update( user_id, signed_users ) return {"failures": failures} async def _process_self_signatures(self, user_id, signatures): """Process uploaded signatures of the user's own keys. Signatures of the user's own keys from this API come in two forms: - signatures of the user's devices by the user's self-signing key, - signatures of the user's master key by the user's devices. Args: user_id (string): the user uploading the keys signatures (dict[string, dict]): map of devices to signed keys Returns: (list[SignatureListItem], dict[string, dict[string, dict]]): a list of signatures to store, and a map of users to devices to failure reasons Raises: SynapseError: if the input is malformed """ signature_list = [] failures = {} if not signatures: return signature_list, failures if not isinstance(signatures, dict): raise SynapseError(400, "Invalid parameter", Codes.INVALID_PARAM) try: # get our self-signing key to verify the signatures ( _, self_signing_key_id, self_signing_verify_key, ) = await self._get_e2e_cross_signing_verify_key(user_id, "self_signing") # get our master key, since we may have received a signature of it. # We need to fetch it here so that we know what its key ID is, so # that we can check if a signature that was sent is a signature of # the master key or of a device ( master_key, _, master_verify_key, ) = await self._get_e2e_cross_signing_verify_key(user_id, "master") # fetch our stored devices. This is used to 1. verify # signatures on the master key, and 2. to compare with what # was sent if the device was signed devices = await self.store.get_e2e_device_keys([(user_id, None)]) if user_id not in devices: raise NotFoundError("No device keys found") devices = devices[user_id] except SynapseError as e: failure = _exception_to_failure(e) failures[user_id] = {device: failure for device in signatures.keys()} return signature_list, failures for device_id, device in signatures.items(): # make sure submitted data is in the right form if not isinstance(device, dict): raise SynapseError(400, "Invalid parameter", Codes.INVALID_PARAM) try: if "signatures" not in device or user_id not in device["signatures"]: # no signature was sent raise SynapseError( 400, "Invalid signature", Codes.INVALID_SIGNATURE ) if device_id == master_verify_key.version: # The signature is of the master key. This needs to be # handled differently from signatures of normal devices. master_key_signature_list = self._check_master_key_signature( user_id, device_id, device, master_key, devices ) signature_list.extend(master_key_signature_list) continue # at this point, we have a device that should be signed # by the self-signing key if self_signing_key_id not in device["signatures"][user_id]: # no signature was sent raise SynapseError( 400, "Invalid signature", Codes.INVALID_SIGNATURE ) try: stored_device = devices[device_id] except KeyError: raise NotFoundError("Unknown device") if self_signing_key_id in stored_device.get("signatures", {}).get( user_id, {} ): # we already have a signature on this device, so we # can skip it, since it should be exactly the same continue _check_device_signature( user_id, self_signing_verify_key, device, stored_device ) signature = device["signatures"][user_id][self_signing_key_id] signature_list.append( SignatureListItem( self_signing_key_id, user_id, device_id, signature ) ) except SynapseError as e: failures.setdefault(user_id, {})[device_id] = _exception_to_failure(e) return signature_list, failures def _check_master_key_signature( self, user_id, master_key_id, signed_master_key, stored_master_key, devices ): """Check signatures of a user's master key made by their devices. Args: user_id (string): the user whose master key is being checked master_key_id (string): the ID of the user's master key signed_master_key (dict): the user's signed master key that was uploaded stored_master_key (dict): our previously-stored copy of the user's master key devices (iterable(dict)): the user's devices Returns: list[SignatureListItem]: a list of signatures to store Raises: SynapseError: if a signature is invalid """ # for each device that signed the master key, check the signature. master_key_signature_list = [] sigs = signed_master_key["signatures"] for signing_key_id, signature in sigs[user_id].items(): _, signing_device_id = signing_key_id.split(":", 1) if ( signing_device_id not in devices or signing_key_id not in devices[signing_device_id]["keys"] ): # signed by an unknown device, or the # device does not have the key raise SynapseError(400, "Invalid signature", Codes.INVALID_SIGNATURE) # get the key and check the signature pubkey = devices[signing_device_id]["keys"][signing_key_id] verify_key = decode_verify_key_bytes(signing_key_id, decode_base64(pubkey)) _check_device_signature( user_id, verify_key, signed_master_key, stored_master_key ) master_key_signature_list.append( SignatureListItem(signing_key_id, user_id, master_key_id, signature) ) return master_key_signature_list async def _process_other_signatures(self, user_id, signatures): """Process uploaded signatures of other users' keys. These will be the target user's master keys, signed by the uploading user's user-signing key. Args: user_id (string): the user uploading the keys signatures (dict[string, dict]): map of users to devices to signed keys Returns: (list[SignatureListItem], dict[string, dict[string, dict]]): a list of signatures to store, and a map of users to devices to failure reasons Raises: SynapseError: if the input is malformed """ signature_list = [] failures = {} if not signatures: return signature_list, failures try: # get our user-signing key to verify the signatures ( user_signing_key, user_signing_key_id, user_signing_verify_key, ) = await self._get_e2e_cross_signing_verify_key(user_id, "user_signing") except SynapseError as e: failure = _exception_to_failure(e) for user, devicemap in signatures.items(): failures[user] = {device_id: failure for device_id in devicemap.keys()} return signature_list, failures for target_user, devicemap in signatures.items(): # make sure submitted data is in the right form if not isinstance(devicemap, dict): raise SynapseError(400, "Invalid parameter", Codes.INVALID_PARAM) for device in devicemap.values(): if not isinstance(device, dict): raise SynapseError(400, "Invalid parameter", Codes.INVALID_PARAM) device_id = None try: # get the target user's master key, to make sure it matches # what was sent ( master_key, master_key_id, _, ) = await self._get_e2e_cross_signing_verify_key( target_user, "master", user_id ) # make sure that the target user's master key is the one that # was signed (and no others) device_id = master_key_id.split(":", 1)[1] if device_id not in devicemap: logger.debug( "upload signature: could not find signature for device %s", device_id, ) # set device to None so that the failure gets # marked on all the signatures device_id = None raise NotFoundError("Unknown device") key = devicemap[device_id] other_devices = [k for k in devicemap.keys() if k != device_id] if other_devices: # other devices were signed -- mark those as failures logger.debug("upload signature: too many devices specified") failure = _exception_to_failure(NotFoundError("Unknown device")) failures[target_user] = { device: failure for device in other_devices } if user_signing_key_id in master_key.get("signatures", {}).get( user_id, {} ): # we already have the signature, so we can skip it continue _check_device_signature( user_id, user_signing_verify_key, key, master_key ) signature = key["signatures"][user_id][user_signing_key_id] signature_list.append( SignatureListItem( user_signing_key_id, target_user, device_id, signature ) ) except SynapseError as e: failure = _exception_to_failure(e) if device_id is None: failures[target_user] = { device_id: failure for device_id in devicemap.keys() } else: failures.setdefault(target_user, {})[device_id] = failure return signature_list, failures async def _get_e2e_cross_signing_verify_key( self, user_id: str, key_type: str, from_user_id: str = None ): """Fetch locally or remotely query for a cross-signing public key. First, attempt to fetch the cross-signing public key from storage. If that fails, query the keys from the homeserver they belong to and update our local copy. Args: user_id: the user whose key should be fetched key_type: the type of key to fetch from_user_id: the user that we are fetching the keys for. This affects what signatures are fetched. Returns: dict, str, VerifyKey: the raw key data, the key ID, and the signedjson verify key Raises: NotFoundError: if the key is not found SynapseError: if `user_id` is invalid """ user = UserID.from_string(user_id) key = await self.store.get_e2e_cross_signing_key( user_id, key_type, from_user_id ) if key: # We found a copy of this key in our database. Decode and return it key_id, verify_key = get_verify_key_from_cross_signing_key(key) return key, key_id, verify_key # If we couldn't find the key locally, and we're looking for keys of # another user then attempt to fetch the missing key from the remote # user's server. # # We may run into this in possible edge cases where a user tries to # cross-sign a remote user, but does not share any rooms with them yet. # Thus, we would not have their key list yet. We instead fetch the key, # store it and notify clients of new, associated device IDs. if self.is_mine(user) or key_type not in ["master", "self_signing"]: # Note that master and self_signing keys are the only cross-signing keys we # can request over federation raise NotFoundError("No %s key found for %s" % (key_type, user_id)) ( key, key_id, verify_key, ) = await self._retrieve_cross_signing_keys_for_remote_user(user, key_type) if key is None: raise NotFoundError("No %s key found for %s" % (key_type, user_id)) return key, key_id, verify_key async def _retrieve_cross_signing_keys_for_remote_user( self, user: UserID, desired_key_type: str, ) -> Tuple[Optional[dict], Optional[str], Optional[VerifyKey]]: """Queries cross-signing keys for a remote user and saves them to the database Only the key specified by `key_type` will be returned, while all retrieved keys will be saved regardless Args: user: The user to query remote keys for desired_key_type: The type of key to receive. One of "master", "self_signing" Returns: A tuple of the retrieved key content, the key's ID and the matching VerifyKey. If the key cannot be retrieved, all values in the tuple will instead be None. """ try: remote_result = await self.federation.query_user_devices( user.domain, user.to_string() ) except Exception as e: logger.warning( "Unable to query %s for cross-signing keys of user %s: %s %s", user.domain, user.to_string(), type(e), e, ) return None, None, None # Process each of the retrieved cross-signing keys desired_key = None desired_key_id = None desired_verify_key = None retrieved_device_ids = [] for key_type in ["master", "self_signing"]: key_content = remote_result.get(key_type + "_key") if not key_content: continue # Ensure these keys belong to the correct user if "user_id" not in key_content: logger.warning( "Invalid %s key retrieved, missing user_id field: %s", key_type, key_content, ) continue if user.to_string() != key_content["user_id"]: logger.warning( "Found %s key of user %s when querying for keys of user %s", key_type, key_content["user_id"], user.to_string(), ) continue # Validate the key contents try: # verify_key is a VerifyKey from signedjson, which uses # .version to denote the portion of the key ID after the # algorithm and colon, which is the device ID key_id, verify_key = get_verify_key_from_cross_signing_key(key_content) except ValueError as e: logger.warning( "Invalid %s key retrieved: %s - %s %s", key_type, key_content, type(e), e, ) continue # Note down the device ID attached to this key retrieved_device_ids.append(verify_key.version) # If this is the desired key type, save it and its ID/VerifyKey if key_type == desired_key_type: desired_key = key_content desired_verify_key = verify_key desired_key_id = key_id # At the same time, store this key in the db for subsequent queries await self.store.set_e2e_cross_signing_key( user.to_string(), key_type, key_content ) # Notify clients that new devices for this user have been discovered if retrieved_device_ids: # XXX is this necessary? await self.device_handler.notify_device_update( user.to_string(), retrieved_device_ids ) return desired_key, desired_key_id, desired_verify_key def _check_cross_signing_key(key, user_id, key_type, signing_key=None): """Check a cross-signing key uploaded by a user. Performs some basic sanity checking, and ensures that it is signed, if a signature is required. Args: key (dict): the key data to verify user_id (str): the user whose key is being checked key_type (str): the type of key that the key should be signing_key (VerifyKey): (optional) the signing key that the key should be signed with. If omitted, signatures will not be checked. """ if ( key.get("user_id") != user_id or key_type not in key.get("usage", []) or len(key.get("keys", {})) != 1 ): raise SynapseError(400, ("Invalid %s key" % (key_type,)), Codes.INVALID_PARAM) if signing_key: try: verify_signed_json(key, user_id, signing_key) except SignatureVerifyException: raise SynapseError( 400, ("Invalid signature on %s key" % key_type), Codes.INVALID_SIGNATURE ) def _check_device_signature(user_id, verify_key, signed_device, stored_device): """Check that a signature on a device or cross-signing key is correct and matches the copy of the device/key that we have stored. Throws an exception if an error is detected. Args: user_id (str): the user ID whose signature is being checked verify_key (VerifyKey): the key to verify the device with signed_device (dict): the uploaded signed device data stored_device (dict): our previously stored copy of the device Raises: SynapseError: if the signature was invalid or the sent device is not the same as the stored device """ # make sure that the device submitted matches what we have stored stripped_signed_device = { k: v for k, v in signed_device.items() if k not in ["signatures", "unsigned"] } stripped_stored_device = { k: v for k, v in stored_device.items() if k not in ["signatures", "unsigned"] } if stripped_signed_device != stripped_stored_device: logger.debug( "upload signatures: key does not match %s vs %s", signed_device, stored_device, ) raise SynapseError(400, "Key does not match") try: verify_signed_json(signed_device, user_id, verify_key) except SignatureVerifyException: logger.debug("invalid signature on key") raise SynapseError(400, "Invalid signature", Codes.INVALID_SIGNATURE) def _exception_to_failure(e): if isinstance(e, SynapseError): return {"status": e.code, "errcode": e.errcode, "message": str(e)} if isinstance(e, CodeMessageException): return {"status": e.code, "message": str(e)} if isinstance(e, NotRetryingDestination): return {"status": 503, "message": "Not ready for retry"} # include ConnectionRefused and other errors # # Note that some Exceptions (notably twisted's ResponseFailed etc) don't # give a string for e.message, which json then fails to serialize. return {"status": 503, "message": str(e)} def _one_time_keys_match(old_key_json, new_key): old_key = json.loads(old_key_json) # if either is a string rather than an object, they must match exactly if not isinstance(old_key, dict) or not isinstance(new_key, dict): return old_key == new_key # otherwise, we strip off the 'signatures' if any, because it's legitimate # for different upload attempts to have different signatures. old_key.pop("signatures", None) new_key_copy = dict(new_key) new_key_copy.pop("signatures", None) return old_key == new_key_copy @attr.s class SignatureListItem: """An item in the signature list as used by upload_signatures_for_device_keys. """ signing_key_id = attr.ib() target_user_id = attr.ib() target_device_id = attr.ib() signature = attr.ib() class SigningKeyEduUpdater(object): """Handles incoming signing key updates from federation and updates the DB""" def __init__(self, hs, e2e_keys_handler): self.store = hs.get_datastore() self.federation = hs.get_federation_client() self.clock = hs.get_clock() self.e2e_keys_handler = e2e_keys_handler self._remote_edu_linearizer = Linearizer(name="remote_signing_key") # user_id -> list of updates waiting to be handled. self._pending_updates = {} # Recently seen stream ids. We don't bother keeping these in the DB, # but they're useful to have them about to reduce the number of spurious # resyncs. self._seen_updates = ExpiringCache( cache_name="signing_key_update_edu", clock=self.clock, max_len=10000, expiry_ms=30 * 60 * 1000, iterable=True, ) async def incoming_signing_key_update(self, origin, edu_content): """Called on incoming signing key update from federation. Responsible for parsing the EDU and adding to pending updates list. Args: origin (string): the server that sent the EDU edu_content (dict): the contents of the EDU """ user_id = edu_content.pop("user_id") master_key = edu_content.pop("master_key", None) self_signing_key = edu_content.pop("self_signing_key", None) if get_domain_from_id(user_id) != origin: logger.warning("Got signing key update edu for %r from %r", user_id, origin) return room_ids = await self.store.get_rooms_for_user(user_id) if not room_ids: # We don't share any rooms with this user. Ignore update, as we # probably won't get any further updates. return self._pending_updates.setdefault(user_id, []).append( (master_key, self_signing_key) ) await self._handle_signing_key_updates(user_id) async def _handle_signing_key_updates(self, user_id): """Actually handle pending updates. Args: user_id (string): the user whose updates we are processing """ device_handler = self.e2e_keys_handler.device_handler device_list_updater = device_handler.device_list_updater with (await self._remote_edu_linearizer.queue(user_id)): pending_updates = self._pending_updates.pop(user_id, []) if not pending_updates: # This can happen since we batch updates return device_ids = [] logger.info("pending updates: %r", pending_updates) for master_key, self_signing_key in pending_updates: new_device_ids = await device_list_updater.process_cross_signing_key_update( user_id, master_key, self_signing_key, ) device_ids = device_ids + new_device_ids await device_handler.notify_device_update(user_id, device_ids)