fix KMSMasterKeyProvider to determine the default region before trying to create the requested master keys

Author: mattsb42-aws

src/aws_encryption_sdk/key_providers/kms.py

@@ -116,8 +116,7 @@ def __init__(self, **kwargs):  # pylint: disable=unused-argument
     def _process_config(self):
         """Traverses the config and adds master keys and regional clients as needed."""
         self._user_agent_adding_config = botocore.config.Config(user_agent_extra=USER_AGENT_SUFFIX)
-        if self.config.key_ids:
-            self.add_master_keys_from_list(self.config.key_ids)
+
         if self.config.region_names:
             self.add_regional_clients_from_list(self.config.region_names)
             self.default_region = self.config.region_names[0]
@@ -126,6 +125,9 @@ def _process_config(self):
             if self.default_region is not None:
                 self.add_regional_client(self.default_region)
 
+        if self.config.key_ids:
+            self.add_master_keys_from_list(self.config.key_ids)
+
     def add_regional_client(self, region_name):
         """Adds a regional client for the specified region if it does not already exist.
 

test/unit/test_providers_kms_master_key_provider.py

@@ -25,6 +25,13 @@
 pytestmark = [pytest.mark.unit, pytest.mark.local]
 
 
+def test_init_with_regionless_key_ids_and_region_names():
+    key_ids = ("alias/key_1",)
+    region_names = ("test-reqion-1",)
+    provider = KMSMasterKeyProvider(region_names=region_names, key_ids=key_ids)
+    assert provider.master_key("alias/key_1").config.client.meta.region_name == region_names[0]
+
+
 class TestKMSMasterKeyProvider(unittest.TestCase):
     def setUp(self):
         self.mock_botocore_session_patcher = patch("aws_encryption_sdk.key_providers.kms.botocore.session.Session")