Patched code sample

import os
from werkzeug.utils import secure_filename


def fixed_edit_package_logic(pack_folder: str) -> str:
    """
    This function demonstrates the patched logic that fixes the path traversal
    vulnerability (CVE-2023-29778) in pyLoad's `edit_package` function.

    The vulnerability was caused by insufficient sanitization which relied on
    a single-pass string replacement of `../`. This could be bypassed using
    crafted inputs like `....//`.

    The fix, demonstrated below, replaces the weak sanitization method with a
    call to a robust utility, `werkzeug.utils.secure_filename`, to properly
    sanitize the user-provided path fragment.

    Args:
        pack_folder: The user-provided folder name, which may be malicious.

    Returns:
        A sanitized, safe folder name that cannot be used for path traversal.
    """
    # The previous vulnerable code was approximately:
    # return pack_folder.replace("../", "")

    # --- The Fix ---
    # The user-provided `pack_folder` is processed by `secure_filename`.
    # This function is designed to produce a flat, ASCII-safe filename by
    # removing directory traversal components (`/`, `../`) and any other
    # characters that are not alphanumeric, underscores, hyphens, or dots.
    #
    # For a malicious input like "....//", which bypassed the original filter:
    # `secure_filename("....//")` would result in an empty string `""`.
    #
    # For a malicious input like "../../etc/passwd":
    # `secure_filename("../../etc/passwd")` would result in `"etc_passwd"`.
    sanitized_folder = secure_filename(pack_folder)

    # The sanitized name can now be safely used in path operations. For example:
    # download_dir = "/opt/pyload/downloads"
    # final_path = os.path.join(download_dir, sanitized_folder)
    # The `final_path` is guaranteed to be inside `download_dir`.

    return sanitized_folder