Prevent undetected modifications via HMAC integrity checks

Author: Susmita-Chakrabarty

pydatastructs/graphs/graph.py

@@ -139,7 +139,9 @@ def get_snapshot(self, timestamp: int):
             stored_signature = snapshot_info["signature"]
             snapshot_data = serialize_graph(snapshot_graph)
             computed_signature = generate_hmac(snapshot_data)
-
+            if computed_signature != stored_signature:
+                raise ValueError("Snapshot integrity check failed! The snapshot may have been modified.")
+            return snapshot_graph
         def list_snapshots(self):
             """Returns all stored timestamps in sorted order."""
             return sorted(self.snapshots.keys())