single-source logic for decrypting a list of items used in both decrypt_multi_get and EncryptedPaginator

Author: mattsb42-aws

src/dynamodb_encryption_sdk/encrypted/client.py

@@ -22,6 +22,7 @@
     crypto_config_from_kwargs,
     decrypt_batch_get_item,
     decrypt_get_item,
+    decrypt_list_of_items,
     decrypt_multi_get,
     encrypt_batch_write_item,
     encrypt_put_item,
@@ -104,8 +105,11 @@ def paginate(self, **kwargs):
         crypto_config, ddb_kwargs = self._crypto_config_method(**kwargs)
 
         for page in self._paginator.paginate(**ddb_kwargs):
-            for pos, value in enumerate(page["Items"]):
-                page["Items"][pos] = self._decrypt_method(item=value, crypto_config=crypto_config)
+            page["Items"] = list(
+                decrypt_list_of_items(
+                    crypto_config=crypto_config, decrypt_method=self._decrypt_method, items=page["Items"]
+                )
+            )
             yield page
 
 

src/dynamodb_encryption_sdk/internal/utils.py

@@ -29,7 +29,7 @@
 from dynamodb_encryption_sdk.transform import dict_to_ddb
 
 try:  # Python 3.5.0 and 3.5.1 have incompatible typing modules
-    from typing import Any, Bool, Callable, Dict, Text  # noqa pylint: disable=unused-import
+    from typing import Any, Bool, Callable, Dict, Iterable, Text  # noqa pylint: disable=unused-import
 except ImportError:  # pragma: no cover
     # We only actually need these imports when running the mypy checks
     pass
@@ -41,6 +41,7 @@
     "crypto_config_from_cache",
     "decrypt_get_item",
     "decrypt_multi_get",
+    "decrypt_list_of_items",
     "decrypt_batch_get_item",
     "encrypt_put_item",
     "encrypt_batch_write_item",
@@ -171,6 +172,22 @@ def _item_transformer(crypto_transformer):
     return lambda x: x
 
 
+def decrypt_list_of_items(crypto_config, decrypt_method, items):
+    # type: (CryptoConfig, Callable, Iterable[Any]) -> Iterable[Any]
+    # TODO: narrow this down
+    """Iterate through a list of encrypted items, decrypting each item and yielding the plaintext item.
+
+    :param CryptoConfig crypto_config: :class:`CryptoConfig` to use
+    :param callable decrypt_method: Method to use to decrypt items
+    :param items: Iterable of encrypted items
+    :return: Iterable of plaintext items
+    """
+    for value in items:
+        yield decrypt_method(
+            item=value, crypto_config=crypto_config.with_item(_item_transformer(decrypt_method)(value))
+        )
+
+
 def decrypt_multi_get(decrypt_method, crypto_config_method, read_method, **kwargs):
     # type: (Callable, Callable, Callable, **Any) -> Dict
     # TODO: narrow this down
@@ -186,11 +203,9 @@ def decrypt_multi_get(decrypt_method, crypto_config_method, read_method, **kwarg
     validate_get_arguments(kwargs)
     crypto_config, ddb_kwargs = crypto_config_method(**kwargs)
     response = read_method(**ddb_kwargs)
-    for pos in range(len(response["Items"])):
-        response["Items"][pos] = decrypt_method(
-            item=response["Items"][pos],
-            crypto_config=crypto_config.with_item(_item_transformer(decrypt_method)(response["Items"][pos])),
-        )
+    response["Items"] = list(
+        decrypt_list_of_items(crypto_config=crypto_config, decrypt_method=decrypt_method, items=response["Items"])
+    )
     return response