diff options
Diffstat (limited to 'synapse/handlers/e2e_keys.py')
| -rw-r--r-- | synapse/handlers/e2e_keys.py | 138 |
1 files changed, 129 insertions, 9 deletions
diff --git a/synapse/handlers/e2e_keys.py b/synapse/handlers/e2e_keys.py index 8d7075f2eb..afc173ab2f 100644 --- a/synapse/handlers/e2e_keys.py +++ b/synapse/handlers/e2e_keys.py @@ -16,6 +16,7 @@ # limitations under the License. import logging +from typing import Dict, Optional, Tuple from six import iteritems @@ -23,6 +24,7 @@ import attr from canonicaljson import encode_canonical_json, json from signedjson.key import decode_verify_key_bytes from signedjson.sign import SignatureVerifyException, verify_signed_json +from signedjson.types import VerifyKey from unpaddedbase64 import decode_base64 from twisted.internet import defer @@ -174,8 +176,8 @@ class E2eKeysHandler(object): """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.""" + specific user we will update the cache with their device list. + """ destination_query = remote_queries_not_in_cache[destination] @@ -961,13 +963,19 @@ class E2eKeysHandler(object): return signature_list, failures @defer.inlineCallbacks - def _get_e2e_cross_signing_verify_key(self, user_id, key_type, from_user_id=None): - """Fetch the cross-signing public key from storage and interpret it. + 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 (str): the user whose key should be fetched - key_type (str): the type of key to fetch - from_user_id (str): the user that we are fetching the keys for. + 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: @@ -976,16 +984,128 @@ class E2eKeysHandler(object): Raises: NotFoundError: if the key is not found + SynapseError: if `user_id` is invalid """ + user = UserID.from_string(user_id) + key_id = None + verify_key = None + key = yield self.store.get_e2e_cross_signing_key( user_id, key_type, from_user_id ) + + # 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 fetch the key here, + # store it and notify clients of new, associated device IDs. + if ( + key is None + and not self.is_mine(user) + # We only get "master" and "self_signing" keys from remote servers + and key_type in ["master", "self_signing"] + ): + key = yield self._retrieve_cross_signing_keys_for_remote_user( + user, key_type + ) + if key is None: - logger.debug("no %s key found for %s", key_type, user_id) + logger.debug("No %s key found for %s", key_type, user_id) raise NotFoundError("No %s key found for %s" % (key_type, user_id)) - key_id, verify_key = get_verify_key_from_cross_signing_key(key) + + # If we retrieved the keys remotely, these values will already be set + if key_id is None or verify_key is None: + try: + key_id, verify_key = get_verify_key_from_cross_signing_key(key) + except ValueError as e: + logger.debug( + "Invalid %s key retrieved: %s - %s %s", key_type, key, type(e), e, + ) + raise SynapseError( + 502, "Invalid %s key retrieved from remote server", key_type + ) + return key, key_id, verify_key + @defer.inlineCallbacks + 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 = yield 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 + + # Process each of the retrieved cross-signing keys + final_key = None + final_key_id = None + final_verify_key = None + device_ids = [] + for key_type in ["master", "self_signing"]: + key_content = remote_result.get(key_type + "_key") + if not key_content: + continue + + # At the same time, store this key in the db for + # subsequent queries + yield self.store.set_e2e_cross_signing_key( + user.to_string(), key_type, key_content + ) + + # Note down the device ID attached to this key + 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.debug( + "Invalid %s key retrieved: %s - %s %s", + key_type, + key_content, + type(e), + e, + ) + continue + device_ids.append(verify_key.version) + + # If this is the desired key type, save it and it's ID/VerifyKey + if key_type == desired_key_type: + final_key = key_content + final_verify_key = verify_key + final_key_id = key_id + + # Notify clients that new devices for this user have been discovered + if device_ids: + yield self.device_handler.notify_device_update(user.to_string(), device_ids) + + return final_key, final_key_id, final_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 |