diff --git a/synapse/handlers/e2e_keys.py b/synapse/handlers/e2e_keys.py
index 8d7075f2eb..8f1bc0323c 100644
--- a/synapse/handlers/e2e_keys.py
+++ b/synapse/handlers/e2e_keys.py
@@ -174,8 +174,8 @@ 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 +961,19 @@ 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 +982,140 @@ class E2eKeysHandler(object):
Raises:
NotFoundError: if the key is not found
+ SynapseError: if `user_id` is invalid
"""
+ user = UserID.from_string(user_id)
key = yield 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,
+ ) = 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)
raise NotFoundError("No %s key found for %s" % (key_type, user_id))
- key_id, verify_key = get_verify_key_from_cross_signing_key(key)
+
return key, key_id, verify_key
+ @defer.inlineCallbacks
+ def _retrieve_cross_signing_keys_for_remote_user(
+ self, user: UserID, desired_key_type: str,
+ ):
+ """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:
+ Deferred[Tuple[Optional[Dict], Optional[str], Optional[VerifyKey]]]: 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, 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
+ yield 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?
+ yield 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
|
