Patched code sample

import os

# Mock functions that would interact with a PowerPoint library
def add_slide(title, content):
    """A safe function to add a slide."""
    print(f"[ACTION] Adding slide with title: '{title}' and content: '{content}'")
    return {"status": "success", "slide_id": 1}

def set_background_color(slide_id, color):
    """A safe function to set a slide's background color."""
    print(f"[ACTION] Setting background of slide {slide_id} to {color}")
    return {"status": "success"}

def safe_execute_llm_code(code_string: str):
    """
    This function represents the fix for the vulnerability.
    It executes LLM-generated code by providing a restricted scope to eval(),
    preventing access to dangerous built-in functions.
    """
    # 1. Define an "allowlist" of safe functions the LLM can call.
    safe_api = {
        "add_slide": add_slide,
        "set_background_color": set_background_color,
    }

    # 2. Create the restricted globals dictionary for eval().
    # The crucial part of the fix is replacing '__builtins__' with a
    # dictionary containing only functions considered safe (or an empty one).
    # This prevents the LLM code from accessing dangerous builtins
    # like `__import__`, `open()`, or `exec()`.
    safe_globals = {
        "__builtins__": {
            "print": print, # Example of allowing a single, safe builtin
            "dict": dict,
            "list": list
        },
        **safe_api
    }

    try:
        # 3. Execute the code using eval() with the restricted scope.
        # Any attempt to call a function not in `safe_globals` will fail.
        print(f"Executing code: {code_string}")
        eval(code_string, safe_globals, {})
        print("Execution successful and safe.\n")
    except Exception as e:
        print(f"Execution blocked. Reason: {e}\n")


if __name__ == '__main__':
    # --- VULNERABLE APPROACH (for demonstration) ---
    # This is what an attacker might try. The LLM could be prompted
    # to generate a malicious string like this.
    malicious_code = "__import__('os').system('echo VULNERABILITY EXPLOITED!')"

    print("--- Simulating VULNERABLE execution (unsafe eval) ---")
    try:
        # In the vulnerable version, eval() has access to all builtins.
        eval(malicious_code)
    except Exception as e:
        print(f"An error occurred: {e}")
    print("-" * 50)


    # --- FIXED APPROACH ---
    print("--- Simulating FIXED execution (safe_execute_llm_code) ---")

    # Example 1: Benign code generated by the LLM. This will work.
    benign_code = "add_slide(title='Introduction', content='Hello World')"
    safe_execute_llm_code(benign_code)

    # Example 2: Malicious code generated by the LLM. This will be blocked.
    safe_execute_llm_code(malicious_code)