Add some clarifying comments and refactor a portion of the `Keyring` class for readability (#14804)
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772e8c2385
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Add some clarifying comments and refactor a portion of the `Keyring` class for readability.
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@ -154,17 +154,21 @@ class Keyring:
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if key_fetchers is None:
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if key_fetchers is None:
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key_fetchers = (
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key_fetchers = (
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# Fetch keys from the database.
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StoreKeyFetcher(hs),
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StoreKeyFetcher(hs),
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# Fetch keys from a configured Perspectives server.
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PerspectivesKeyFetcher(hs),
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PerspectivesKeyFetcher(hs),
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# Fetch keys from the origin server directly.
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ServerKeyFetcher(hs),
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ServerKeyFetcher(hs),
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)
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)
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self._key_fetchers = key_fetchers
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self._key_fetchers = key_fetchers
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self._server_queue: BatchingQueue[
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self._fetch_keys_queue: BatchingQueue[
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_FetchKeyRequest, Dict[str, Dict[str, FetchKeyResult]]
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_FetchKeyRequest, Dict[str, Dict[str, FetchKeyResult]]
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] = BatchingQueue(
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] = BatchingQueue(
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"keyring_server",
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"keyring_server",
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clock=hs.get_clock(),
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clock=hs.get_clock(),
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# The method called to fetch each key
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process_batch_callback=self._inner_fetch_key_requests,
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process_batch_callback=self._inner_fetch_key_requests,
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)
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)
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@ -287,7 +291,7 @@ class Keyring:
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minimum_valid_until_ts=verify_request.minimum_valid_until_ts,
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minimum_valid_until_ts=verify_request.minimum_valid_until_ts,
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key_ids=list(key_ids_to_find),
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key_ids=list(key_ids_to_find),
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)
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)
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found_keys_by_server = await self._server_queue.add_to_queue(
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found_keys_by_server = await self._fetch_keys_queue.add_to_queue(
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key_request, key=verify_request.server_name
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key_request, key=verify_request.server_name
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)
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)
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@ -352,7 +356,17 @@ class Keyring:
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async def _inner_fetch_key_requests(
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async def _inner_fetch_key_requests(
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self, requests: List[_FetchKeyRequest]
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self, requests: List[_FetchKeyRequest]
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) -> Dict[str, Dict[str, FetchKeyResult]]:
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) -> Dict[str, Dict[str, FetchKeyResult]]:
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"""Processing function for the queue of `_FetchKeyRequest`."""
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"""Processing function for the queue of `_FetchKeyRequest`.
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Takes a list of key fetch requests, de-duplicates them and then carries out
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each request by invoking self._inner_fetch_key_request.
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Args:
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requests: A list of requests for homeserver verify keys.
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Returns:
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{server name: {key id: fetch key result}}
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"""
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logger.debug("Starting fetch for %s", requests)
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logger.debug("Starting fetch for %s", requests)
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@ -397,8 +411,23 @@ class Keyring:
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async def _inner_fetch_key_request(
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async def _inner_fetch_key_request(
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self, verify_request: _FetchKeyRequest
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self, verify_request: _FetchKeyRequest
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) -> Dict[str, FetchKeyResult]:
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) -> Dict[str, FetchKeyResult]:
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"""Attempt to fetch the given key by calling each key fetcher one by
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"""Attempt to fetch the given key by calling each key fetcher one by one.
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one.
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If a key is found, check whether its `valid_until_ts` attribute satisfies the
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`minimum_valid_until_ts` attribute of the `verify_request`. If it does, we
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refrain from asking subsequent fetchers for that key.
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Even if the above check fails, we still return the found key - the caller may
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still find the invalid key result useful. In this case, we continue to ask
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subsequent fetchers for the invalid key, in case they return a valid result
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for it. This can happen when fetching a stale key result from the database,
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before querying the origin server for an up-to-date result.
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Args:
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verify_request: The request for a verify key. Can include multiple key IDs.
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Returns:
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A map of {key_id: the key fetch result}.
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"""
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"""
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logger.debug("Starting fetch for %s", verify_request)
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logger.debug("Starting fetch for %s", verify_request)
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@ -420,25 +449,21 @@ class Keyring:
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if not key:
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if not key:
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continue
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continue
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# If we already have a result for the given key ID we keep the
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# If we already have a result for the given key ID, we keep the
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# one with the highest `valid_until_ts`.
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# one with the highest `valid_until_ts`.
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existing_key = found_keys.get(key_id)
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existing_key = found_keys.get(key_id)
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if existing_key:
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if existing_key and existing_key.valid_until_ts > key.valid_until_ts:
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if key.valid_until_ts <= existing_key.valid_until_ts:
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continue
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# We always store the returned key even if it doesn't the
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# `minimum_valid_until_ts` requirement, as some verification
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# requests may still be able to be satisfied by it.
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#
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# We still keep looking for the key from other fetchers in that
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# case though.
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found_keys[key_id] = key
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if key.valid_until_ts < verify_request.minimum_valid_until_ts:
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continue
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continue
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missing_key_ids.discard(key_id)
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# Check if this key's expiry timestamp is valid for the verify request.
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if key.valid_until_ts >= verify_request.minimum_valid_until_ts:
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# Stop looking for this key from subsequent fetchers.
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missing_key_ids.discard(key_id)
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# We always store the returned key even if it doesn't meet the
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# `minimum_valid_until_ts` requirement, as some verification
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# requests may still be able to be satisfied by it.
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found_keys[key_id] = key
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return found_keys
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return found_keys
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