fix: validate REST Proxy subscription param types

src/karapace/kafka_rest_apis/consumer_manager.py

@@ -150,6 +150,16 @@ def _illegal_state_fail(message: str, content_type: str) -> None:
             message=message,
         )
 
+    @staticmethod
+    def _unprocessable_entity(*, message: str, content_type: str) -> None:
+        ConsumerManager._assert(
+            cond=False,
+            code=HTTPStatus.UNPROCESSABLE_ENTITY,
+            sub_code=RESTErrorCodes.HTTP_UNPROCESSABLE_ENTITY.value,
+            content_type=content_type,
+            message=message,
+        )
+
     # external api below
     # CONSUMER
     async def create_consumer(self, group_name: str, request_data: dict, content_type: str):
@@ -318,7 +328,11 @@ async def set_subscription(self, internal_name: tuple[str, str], content_type: s
         LOG.info("Updating subscription for %s", internal_name)
         self._assert_consumer_exists(internal_name, content_type)
         topics = request_data.get("topics", [])
+        if topics and not isinstance(topics, list):
+            self._unprocessable_entity(message="Topics is expected to be list of strings", content_type=content_type)
         topics_pattern = request_data.get("topic_pattern")
+        if topics_pattern and not isinstance(topics_pattern, str):
+            self._unprocessable_entity(message="Topic patterns is expected to be a string", content_type=content_type)
         if not (topics or topics_pattern):
             self._illegal_state_fail(
                 message="Neither topic_pattern nor topics are present in request", content_type=content_type

tests/integration/test_rest_consumer.py

@@ -167,6 +167,16 @@ async def test_subscription(rest_async_client, admin_client, producer, trail):
     res = await rest_async_client.post(assign_path, headers=REST_HEADERS["json"], json=assign_payload)
     assert res.status_code == 409, "Expecting status code 409 on assign after subscribe on the same consumer instance"
 
+    # topics parameter is expected to be array, 4xx error returned
+    res = await rest_async_client.post(sub_path, json={"topics": topic_name}, headers=REST_HEADERS["json"])
+    assert res.status_code == 422, "Expecting status code 422 on subscription update with invalid topics param"
+
+    # topic pattern parameter is expected to be array, 4xx error returned
+    res = await rest_async_client.post(
+        sub_path, json={"topic_pattern": ["not", "a", "string"]}, headers=REST_HEADERS["json"]
+    )
+    assert res.status_code == 422, "Expecting status code 422 on subscription update with invalid topics param"
+
 
 @pytest.mark.parametrize("trail", ["", "/"])
 async def test_seek(rest_async_client, admin_client, trail):