# -*- coding: utf-8 -*-
# Copyright © Cloud Linux GmbH & Cloud Linux Software, Inc 2010-2022 All Rights Reserved
#
# Licensed under CLOUD LINUX LICENSE AGREEMENT
# http://cloudlinux.com/docs/LICENSE.TXT
#

import glob
import importlib.util
import logging
import os
import stat
import sys

from .helpers import LISTENERS_DIRECTORY

logger = logging.getLogger(__name__)

from .modify_domain_hook import ModifyDomainHook
from .modify_admin_hook import ModifyAdminHook
from .modify_user_hook import ModifyUserHook
from .modify_package_hook import ModifyPackageHook


def _is_root_owned_unwritable(filepath):
    """
    Return True only if `filepath` is a regular file owned by root (uid 0) and
    not group- or world-writable. Used to gate a listener before its top-level
    code is exec_module()'d as root: a *.py (or a symlink whose real target) a
    non-root principal can write is refused rather than executed. os.stat
    follows symlinks, so it stats the real inode whose code would run.
    """
    try:
        st = os.stat(filepath)
    except OSError:
        return False
    return (stat.S_ISREG(st.st_mode) and
            st.st_uid == 0 and
            not (st.st_mode & (stat.S_IWGRP | stat.S_IWOTH)))


def import_file(filepath):
    # Fast path: see if the module has already been imported.
    name = os.path.basename(filepath)[:-3]
    if name in sys.modules:
        return sys.modules[name]

    # Defense-in-depth: exec_module() below runs the listener's top-level code
    # in this root process. Refuse a listener that is not root-owned or is
    # group/world-writable, so an attacker-influenceable file is not executed.
    if not _is_root_owned_unwritable(filepath):
        logger.warning('refusing to load listener %s: not root-owned or '
                       'group/world-writable', filepath)
        return None

    # If any of the following calls raises an exception,
    # there's a problem we can't handle -- let the caller handle it.
    module_spec = importlib.util.spec_from_file_location(name, filepath)
    if module_spec is None:
        raise ImportError(f"Can't find module {name} at {filepath}")

    # Load the module, potentially raising ImportError if the module cannot be loaded
    module = importlib.util.module_from_spec(module_spec)
    module_spec.loader.exec_module(module)

    # Add the module to sys.modules
    sys.modules[name] = module
    return module


# automatically scan directory for universal hooks
for hook_py in glob.glob(os.path.join(LISTENERS_DIRECTORY, '*.py')):
    import_file(hook_py)


__all__ = (
    'ModifyDomainHook',
    'ModifyAdminHook',
    'ModifyUserHook',
    'ModifyPackageHook',
)