fix: add more input validation

Author: Michael Brewer

Diff for: aws_lambda_powertools/event_handler/api_gateway.py

@@ -542,13 +542,23 @@ def _resolve(self) -> ResponseBuilder:
 
     def _remove_prefix(self, path: str) -> str:
         """Remove the configured prefix from the path"""
-        if self._strip_prefixes:
-            for prefix in self._strip_prefixes:
-                if path.startswith(prefix + "/"):
-                    return path[len(prefix) :]
+        if not isinstance(self._strip_prefixes, list):
+            return path
+
+        for prefix in self._strip_prefixes:
+            if self._path_starts_with(path, prefix):
+                return path[len(prefix) :]
 
         return path
 
+    @staticmethod
+    def _path_starts_with(path: str, prefix: str):
+        """Returns true if the `path` starts with a prefix plus a `/`"""
+        if not isinstance(prefix, str) or len(prefix) == 0:
+            return False
+
+        return path.startswith(prefix + "/")
+
     def _not_found(self, method: str) -> ResponseBuilder:
         """Called when no matching route was found and includes support for the cors preflight response"""
         headers = {}

Diff for: tests/functional/event_handler/test_api_gateway.py

@@ -797,3 +797,29 @@ def foo():
 
     # THEN a route for `/foo` should be found
     assert response["statusCode"] == 200
+
+
+@pytest.mark.parametrize(
+    "prefix",
+    [
+        pytest.param("/foo", id="String are not supported"),
+        pytest.param({"/foo"}, id="Sets are not supported"),
+        pytest.param({"foo": "/foo"}, id="Dicts are not supported"),
+        pytest.param(tuple("/foo"), id="Tuples are not supported"),
+        pytest.param([None, 1, "", False], id="List of invalid values"),
+    ],
+)
+def test_ignore_invalid(prefix):
+    # GIVEN an invalid prefix
+    app = ApiGatewayResolver(strip_prefixes=prefix)
+
+    @app.get("/foo/status")
+    def foo():
+        ...
+
+    # WHEN calling handler
+    response = app({"httpMethod": "GET", "path": "/foo/status"}, None)
+
+    # THEN a route for `/foo/status` should be found
+    # so no prefix was stripped from the request path
+    assert response["statusCode"] == 200