From 3a125625e70634075cc4d965a01309af56748eb2 Mon Sep 17 00:00:00 2001 From: Andrew Morgan <1342360+anoadragon453@users.noreply.github.com> Date: Fri, 13 Jan 2023 12:37:28 +0000 Subject: [PATCH] Add some clarifying comments and refactor a portion of the `Keyring` class for readability (#14804) --- changelog.d/14804.misc | 1 + synapse/crypto/keyring.py | 65 +++++++++++++++++++++++++++------------ 2 files changed, 46 insertions(+), 20 deletions(-) create mode 100644 changelog.d/14804.misc diff --git a/changelog.d/14804.misc b/changelog.d/14804.misc new file mode 100644 index 000000000..24302332b --- /dev/null +++ b/changelog.d/14804.misc @@ -0,0 +1 @@ +Add some clarifying comments and refactor a portion of the `Keyring` class for readability. \ No newline at end of file diff --git a/synapse/crypto/keyring.py b/synapse/crypto/keyring.py index 69310d903..86cd4af9b 100644 --- a/synapse/crypto/keyring.py +++ b/synapse/crypto/keyring.py @@ -154,17 +154,21 @@ class Keyring: if key_fetchers is None: key_fetchers = ( + # Fetch keys from the database. StoreKeyFetcher(hs), + # Fetch keys from a configured Perspectives server. PerspectivesKeyFetcher(hs), + # Fetch keys from the origin server directly. ServerKeyFetcher(hs), ) self._key_fetchers = key_fetchers - self._server_queue: BatchingQueue[ + self._fetch_keys_queue: BatchingQueue[ _FetchKeyRequest, Dict[str, Dict[str, FetchKeyResult]] ] = BatchingQueue( "keyring_server", clock=hs.get_clock(), + # The method called to fetch each key process_batch_callback=self._inner_fetch_key_requests, ) @@ -287,7 +291,7 @@ class Keyring: minimum_valid_until_ts=verify_request.minimum_valid_until_ts, key_ids=list(key_ids_to_find), ) - found_keys_by_server = await self._server_queue.add_to_queue( + found_keys_by_server = await self._fetch_keys_queue.add_to_queue( key_request, key=verify_request.server_name ) @@ -352,7 +356,17 @@ class Keyring: async def _inner_fetch_key_requests( self, requests: List[_FetchKeyRequest] ) -> Dict[str, Dict[str, FetchKeyResult]]: - """Processing function for the queue of `_FetchKeyRequest`.""" + """Processing function for the queue of `_FetchKeyRequest`. + + Takes a list of key fetch requests, de-duplicates them and then carries out + each request by invoking self._inner_fetch_key_request. + + Args: + requests: A list of requests for homeserver verify keys. + + Returns: + {server name: {key id: fetch key result}} + """ logger.debug("Starting fetch for %s", requests) @@ -397,8 +411,23 @@ class Keyring: async def _inner_fetch_key_request( self, verify_request: _FetchKeyRequest ) -> Dict[str, FetchKeyResult]: - """Attempt to fetch the given key by calling each key fetcher one by - one. + """Attempt to fetch the given key by calling each key fetcher one by one. + + If a key is found, check whether its `valid_until_ts` attribute satisfies the + `minimum_valid_until_ts` attribute of the `verify_request`. If it does, we + refrain from asking subsequent fetchers for that key. + + Even if the above check fails, we still return the found key - the caller may + still find the invalid key result useful. In this case, we continue to ask + subsequent fetchers for the invalid key, in case they return a valid result + for it. This can happen when fetching a stale key result from the database, + before querying the origin server for an up-to-date result. + + Args: + verify_request: The request for a verify key. Can include multiple key IDs. + + Returns: + A map of {key_id: the key fetch result}. """ logger.debug("Starting fetch for %s", verify_request) @@ -420,25 +449,21 @@ class Keyring: if not key: continue - # If we already have a result for the given key ID we keep the + # If we already have a result for the given key ID, we keep the # one with the highest `valid_until_ts`. existing_key = found_keys.get(key_id) - if existing_key: - if key.valid_until_ts <= existing_key.valid_until_ts: - continue - - # We always store the returned key even if it doesn't the - # `minimum_valid_until_ts` requirement, as some verification - # requests may still be able to be satisfied by it. - # - # We still keep looking for the key from other fetchers in that - # case though. - found_keys[key_id] = key - - if key.valid_until_ts < verify_request.minimum_valid_until_ts: + if existing_key and existing_key.valid_until_ts > key.valid_until_ts: continue - missing_key_ids.discard(key_id) + # Check if this key's expiry timestamp is valid for the verify request. + if key.valid_until_ts >= verify_request.minimum_valid_until_ts: + # Stop looking for this key from subsequent fetchers. + missing_key_ids.discard(key_id) + + # We always store the returned key even if it doesn't meet the + # `minimum_valid_until_ts` requirement, as some verification + # requests may still be able to be satisfied by it. + found_keys[key_id] = key return found_keys