Patched code sample

import subprocess
import os

def export_configuration_fixed(user_provided_filename):
    """
    Securely exports system configuration to a compressed archive.
    This function fixes a command injection vulnerability by not using a shell
    and by treating user input as data, not part of a command string.
    """
    # 1. Sanitize input to prevent path traversal attacks (e.g., "../../../etc/passwd").
    # os.path.basename() ensures we only get the filename component.
    safe_filename = os.path.basename(user_provided_filename)

    # Further validation to prevent empty or dot-only filenames.
    if not safe_filename or safe_filename in ('.', '..'):
        raise ValueError("A valid filename is required.")

    destination_path = f"/tmp/{safe_filename}"
    source_directory = "/etc/inhand/config" # Example source directory

    # 2. Construct the command as a list of arguments, not a single string.
    # This ensures that user input is treated as a single, literal argument
    # to the 'tar' command, rather than being interpreted by the shell.
    command_args = [
        "/bin/tar",
        "-czf",
        destination_path,
        source_directory
    ]

    try:
        # 3. Execute the command without a shell (shell=False is the default and safest).
        # The 'check=True' argument will raise an exception if the command fails.
        subprocess.run(
            command_args,
            check=True,
            capture_output=True,
            text=True
        )
        print(f"Successfully created archive at {destination_path}")
    except FileNotFoundError:
        # This error occurs if the '/bin/tar' executable doesn't exist.
        print("Error: The 'tar' command could not be found.")
        raise
    except subprocess.CalledProcessError as e:
        # This error occurs if 'tar' returns a non-zero exit code.
        print(f"Error executing tar command: {e.stderr}")
        raise
    except ValueError as e:
        # Catches the invalid filename error from our validation.
        print(f"Error: {e}")
        raise