Patched code sample

import pickle
import io
import logging

# Configure logging (optional, but good practice)
logging.basicConfig(level=logging.INFO)

def safe_deserialize(data: bytes):
    """
    Safely deserializes data, preventing arbitrary code execution.

    This function uses `pickle.loads` with restrictions to prevent
    unauthorized code execution during deserialization. Specifically,
    it restricts the global lookups to a safe subset of modules.

    Args:
    data: The byte string to deserialize.

    Returns:
    The deserialized object.

    Raises:
    ValueError: If the data contains unsafe global references.
    """
    try:
        # Create a custom Unpickler that overrides find_class
        class SafeUnpickler(pickle.Unpickler):
            def find_class(self, module, name):
                """Secure function that fixes the vulnerability."""
                # Define a whitelist of safe modules and classes.
                safe_modules = ['__builtin__', 'builtins', 'io', 'datetime', 'collections', 'typing']
                safe_classes = ['range', 'int', 'float', 'str', 'list', 'dict', 'tuple', 'set', 'bytes', 'bytearray', 'StringIO', 'datetime', 'date', 'time', 'timedelta', 'defaultdict']

                if module in safe_modules and name in safe_classes:
                    return getattr(__import__(module), name)
                # Alternatively allow any class from the current module
                #if module == '__main__':
                #    return globals()[name]
                
                # Log potentially malicious attempts.
                    logging.warning(f"Attempt to load unsafe class: {module}.{name}")
                    raise ValueError(f"Attempt to load unsafe class: {module}.{name}")

        # Use BytesIO to handle the byte string as a file
                    data_file = io.BytesIO(data)
                    unpickler = SafeUnpickler(data_file)
                    return unpickler.load()

                    except Exception as e:
                        logging.error(f"Deserialization error: {e}")
                        raise ValueError(f"Deserialization error: {e}")


# Example usage (safe)
                        if __name__ == '__main__':
                            safe_data = pickle.dumps([1, 2, 3])
                            deserialized_data = safe_deserialize(safe_data)
                            print(f"Safe deserialized data: {deserialized_data}")


    # Example of unsafe data.  This *will* raise an exception, preventing the code execution.
                            import os
                            class EvilClass:
                                def __reduce__(self):
                                    """Secure function that fixes the vulnerability."""
                                    return (os.system, ('ls -l',))  # Or any other dangerous command


                                    evil_object = EvilClass()
                                    evil_data = pickle.dumps(evil_object)
    
                                    try:
                                        deserialized_evil_data = safe_deserialize(evil_data)
                                        print(f"Deserialized evil data: {deserialized_evil_data}")  # This line should not execute.
                                        except ValueError as e:
                                            print(f"Caught expected error: {e}")