KMS: Return proper metadata when replicating a key (#6788)

moto/kms/models.py

@@ -322,14 +322,16 @@ class KmsBackend(BaseBackend):
     #
     # In our implementation with just create a copy of all the properties once without any protection from change,
     # as the exact implementation is currently infeasible.
-    def replicate_key(self, key_id: str, replica_region: str) -> None:
+    def replicate_key(self, key_id: str, replica_region: str) -> Key:
         # Using copy() instead of deepcopy(), as the latter results in exception:
         #    TypeError: cannot pickle '_cffi_backend.FFI' object
         # Since we only update top level properties, copy() should suffice.
         replica_key = copy(self.keys[key_id])
         replica_key.region = replica_region
+        replica_key.arn = replica_key.arn.replace(self.region_name, replica_region)
         to_region_backend = kms_backends[self.account_id][replica_region]
         to_region_backend.keys[replica_key.id] = replica_key
+        return replica_key
 
     def update_key_description(self, key_id: str, description: str) -> None:
         key = self.keys[self.get_key_id(key_id)]

moto/kms/responses.py

@@ -128,11 +128,17 @@ class KmsResponse(BaseResponse):
         )
         return json.dumps(key.to_dict())
 
-    def replicate_key(self) -> None:
+    def replicate_key(self) -> str:
         key_id = self._get_param("KeyId")
         self._validate_key_id(key_id)
         replica_region = self._get_param("ReplicaRegion")
-        self.kms_backend.replicate_key(key_id, replica_region)
+        replica_key = self.kms_backend.replicate_key(key_id, replica_region)
+        return json.dumps(
+            {
+                "ReplicaKeyMetadata": replica_key.to_dict()["KeyMetadata"],
+                "ReplicaPolicy": replica_key.generate_default_policy(),
+            }
+        )
 
     def update_key_description(self) -> str:
         """https://docs.aws.amazon.com/kms/latest/APIReference/API_UpdateKeyDescription.html"""

tests/test_kms/test_kms_boto3.py

@@ -171,12 +171,16 @@ def test_replicate_key():
         to_region_client.describe_key(KeyId=key_id)
 
     with mock.patch.object(rsa, "generate_private_key", return_value=""):
-        from_region_client.replicate_key(
+        replica_response = from_region_client.replicate_key(
             KeyId=key_id, ReplicaRegion=region_to_replicate_to
         )
     to_region_client.describe_key(KeyId=key_id)
     from_region_client.describe_key(KeyId=key_id)
 
+    assert "ReplicaKeyMetadata" in replica_response
+    assert region_to_replicate_to in replica_response["ReplicaKeyMetadata"]["Arn"]
+    assert "ReplicaPolicy" in replica_response
+
 
 @mock_kms
 def test_create_key_deprecated_master_custom_key_spec():