Catch unhandled ValueError from future timestamp

CHANGES.rst

@@ -3,6 +3,8 @@ Version 2.1.1
 
 Unreleased
 
+-   Handle date overflow in timed unsign. :pr:`296`
+
 
 Version 2.1.0
 -------------

src/itsdangerous/timed.py

@@ -124,7 +124,13 @@ def unsign(
         # split the value and the timestamp.
         if sig_error is not None:
             if ts_int is not None:
-                ts_dt = self.timestamp_to_datetime(ts_int)
+                try:
+                    ts_dt = self.timestamp_to_datetime(ts_int)
+                except (ValueError, OSError) as exc:
+                    # Windows raises OSError
+                    raise BadTimeSignature(
+                        "Malformed timestamp", payload=value
+                    ) from exc
 
             raise BadTimeSignature(str(sig_error), payload=value, date_signed=ts_dt)
 

tests/test_itsdangerous/test_timed.py

@@ -66,6 +66,15 @@ def test_malformed_timestamp(self, signer):
         assert "Malformed" in str(exc_info.value)
         assert exc_info.value.date_signed is None
 
+    def test_malformed_future_timestamp(self, signer):
+        signed = b"value.TgPVoaGhoQ.AGBfQ6G6cr07byTRt0zAdPljHOY"
+
+        with pytest.raises(BadTimeSignature) as exc_info:
+            signer.unsign(signed)
+
+        assert "Malformed" in str(exc_info.value)
+        assert exc_info.value.date_signed is None
+
     def test_future_age(self, signer):
         signed = signer.sign("value")