Patched code sample

import docker
import os
import io

# This code demonstrates a hypothetical fix for the described vulnerability.
# The vulnerability was a dangerous fallback to a less secure execution
# environment when a primary, secure one (Docker) was unavailable.
#
# The fix is to REMOVE the insecure fallback entirely. If the secure
# environment cannot be initialized, the tool should fail explicitly
# and refuse to execute any code, rather than silently switching to
# a vulnerable mode.

class CodeInterpreterTool:
    """
    A tool for executing Python code in a secure, isolated Docker environment.

    This version has been fixed to prevent a fallback to an insecure
    execution method. It will now raise an exception during initialization if
    a connection to Docker cannot be established, ensuring that code is never
    run outside of the intended sandboxed container.
    """
    _docker_client = None
    _image_name: str = "python:3.11-slim"

    def __init__(self):
        try:
            self._docker_client = docker.from_env()
            # The ping() method confirms that the Docker daemon is running and accessible.
            if not self._docker_client.ping():
                raise docker.errors.DockerException
            
            # Ensure the required Docker image is available locally
            try:
                self._docker_client.images.get(self._image_name)
            except docker.errors.ImageNotFound:
                print(f"Pulling required Docker image: {self._image_name}...")
                self._docker_client.images.pull(self._image_name)

        except docker.errors.DockerException as e:
            # FIX: Instead of falling back to a different sandbox, we raise an error.
            # This ensures that the tool cannot be used in an insecure state.
            raise EnvironmentError(
                "Docker is not running or is not accessible. "
                "The CodeInterpreterTool requires a running Docker daemon "
                "to execute code securely. Insecure fallbacks have been removed."
            ) from e

    def execute(self, code: str) -> str:
        """
        Executes the given Python code inside a Docker container and returns the output.

        Args:
            code: A string containing the Python code to be executed.

        Returns:
            A string containing the stdout and stderr from the code execution.
        """
        if self._docker_client is None:
            # This check is redundant if __init__ is always called, but serves as a safeguard.
            raise RuntimeError("Docker client not initialized. Cannot execute code.")

        try:
            container = self._docker_client.containers.run(
                image=self._image_name,
                command=["python", "-c", code],
                detach=False,
                remove=True, # Automatically remove the container when it exits
                stderr=True,
                stdout=True
            )
            # The output from the container is bytes, so we decode it to a string.
            return container.decode('utf-8')
        except docker.errors.ContainerError as e:
            # This error occurs if the code inside the container returns a non-zero exit code.
            return f"Error executing code in container: {e.stderr.decode('utf-8')}"
        except Exception as e:
            return f"An unexpected error occurred with Docker: {str(e)}"

# --- Demonstration of the fix ---
if __name__ == "__main__":
    print("Attempting to initialize the fixed CodeInterpreterTool...")
    
    # This block will only succeed if you have Docker installed and running.
    # If Docker is not available, it will raise the EnvironmentError from __init__.
    try:
        code_interpreter = CodeInterpreterTool()
        print("✅ Tool initialized successfully (Docker is running).")

        # Example 1: Benign code execution
        print("\n--- Running benign code ---")
        benign_code = "print('Hello from the secure container!')"
        output = code_interpreter.execute(benign_code)
        print(f"Output:\n{output}")

        # Example 2: Code that would have been dangerous in the vulnerable version.
        # This code attempts to use ctypes, which could lead to RCE on the host
        # in a weak sandbox. Here, it will be safely contained within Docker.
        # It will likely fail because system commands like 'touch' may not
        # be available or have permissions, but it won't affect the host machine.
        print("\n--- Running potentially malicious code (safely) ---")
        malicious_code_attempt = """
import ctypes
import os
try:
    # This command will only run inside the isolated container.
    # It cannot affect the host system.
    os.system('echo "This is running inside the container" > /tmp/test.txt && cat /tmp/test.txt')
except Exception as e:
    print(f"Could not execute system command: {e}")
"""
        output = code_interpreter.execute(malicious_code_attempt)
        print(f"Output:\n{output}")
        
    except EnvironmentError as e:
        print("\n--- Test Result: FAILED TO INITIALIZE ---")
        print(f"❌ ERROR: {e}")
        print("\nThis is the expected and correct behavior when Docker is not available.")
        print("The tool has safely prevented execution instead of using an insecure fallback.")