Patched code sample

import subprocess

def secure_download_and_deploy_image(image_url, registry, username, password):
    """
    Represents a fix for a credential exposure vulnerability.

    The vulnerable approach would involve passing credentials as command-line
    arguments or environment variables, which could be inspected by other
    processes, including the container being deployed.

    This corrected function demonstrates a secure pattern by:
    1. Using the container runtime's login command with a feature that accepts
       the password via standard input (`--password-stdin`). This prevents the
       password from appearing in the system's process list.
    2. Performing the image pull command separately, which will then use the
       securely cached credentials from the login step.
    """
    # Step 1: Securely log in to the registry. The password is passed via stdin
    # and is not exposed as a command-line argument.
    login_command = [
        'podman', 'login', registry,
        '--username', username,
        '--password-stdin'
    ]
    try:
        login_proc = subprocess.Popen(
            login_command,
            stdin=subprocess.PIPE,
            stdout=subprocess.PIPE,
            stderr=subprocess.PIPE,
            text=True
        )
        # The password string is written directly to the process's standard input.
        stdout, stderr = login_proc.communicate(input=password)

        if login_proc.returncode != 0:
            # Error handling should be careful not to log the stderr indiscriminately,
            # as it could contain sensitive information.
            raise RuntimeError(f"Failed to log in to registry '{registry}'.")

    except FileNotFoundError:
        raise RuntimeError("'podman' command not found. Is a container runtime installed?")
    except Exception as e:
        # Broad exception to catch other potential issues during login.
        raise RuntimeError(f"An error occurred during registry login: {e}")

    # Step 2: Pull and deploy the image. The command no longer contains any
    # credentials; the container runtime uses the authenticated session.
    deploy_command = ['podman', 'run', '--rm', image_url]
    try:
        subprocess.run(
            deploy_command,
            check=True,
            capture_output=True,
            text=True
        )
    except subprocess.CalledProcessError as e:
        # Handle errors from the deployment step.
        raise RuntimeError(f"Failed to deploy image '{image_url}'. Error: {e.stderr}")