Add a timeout for PyJWKClient requests

By default, the timeout for urlopen is socket._GLOBAL_DEFAULT_TIMEOUT
which is None (meaning that the request never times out):

https://docs.python.org/3/library/socket.html#socket.getdefaulttimeout

This change sets the timeout to 30 but also adds a timeout variable
users can set.

jwt/jwks_client.py

@@ -19,12 +19,14 @@ def __init__(
         cache_jwk_set: bool = True,
         lifespan: int = 300,
         headers: Optional[Dict[str, Any]] = None,
+        timeout: int = 30,
     ):
         if headers is None:
             headers = {}
         self.uri = uri
         self.jwk_set_cache: Optional[JWKSetCache] = None
         self.headers = headers
+        self.timeout = timeout
 
         if cache_jwk_set:
             # Init jwt set cache with default or given lifespan.
@@ -46,9 +48,9 @@ def fetch_data(self) -> Any:
         jwk_set: Any = None
         try:
             r = urllib.request.Request(url=self.uri, headers=self.headers)
-            with urllib.request.urlopen(r) as response:
+            with urllib.request.urlopen(r, timeout=self.timeout) as response:
                 jwk_set = json.load(response)
-        except URLError as e:
+        except (URLError, TimeoutError) as e:
             raise PyJWKClientError(f'Fail to fetch data from the url, err: "{e}"')
         else:
             return jwk_set

tests/test_jwks_client.py

@@ -78,6 +78,13 @@ def mocked_first_call_wrong_kid_second_call_correct_kid(
         yield urlopen_mock
 
 
+@contextlib.contextmanager
+def mocked_timeout():
+    with mock.patch("urllib.request.urlopen") as urlopen_mock:
+        urlopen_mock.side_effect = TimeoutError("timed out")
+        yield urlopen_mock
+
+
 @crypto_required
 class TestPyJWKClient:
     def test_fetch_data_forwards_headers_to_correct_url(self):
@@ -309,3 +316,13 @@ def test_get_jwt_set_invalid_lifespan(self):
         with pytest.raises(PyJWKClientError):
             jwks_client = PyJWKClient(url, lifespan=-1)
             assert jwks_client is None
+
+    def test_get_jwt_set_timeout(self):
+        url = "https://dev-87evx9ru.auth0.com/.well-known/jwks.json"
+        jwks_client = PyJWKClient(url, timeout=5)
+
+        with pytest.raises(PyJWKClientError) as exc:
+            with mocked_timeout():
+                jwks_client.get_jwk_set()
+
+        assert 'Fail to fetch data from the url, err: "timed out"' in str(exc.value)