Mini Shell

# -*- coding: utf-8 -*-

# Copyright © Cloud Linux GmbH & Cloud Linux Software, Inc 2010-2018 All Rights Reserved
#
# Licensed under CLOUD LINUX LICENSE AGREEMENT
# http://cloudlinux.com/docs/LICENSE.TXT
#

import os
import pwd
import grp

from contextlib import contextmanager

from .clexception import FormattedException


class ClPwd:

    LOGIN_DEF_FILE = '/etc/login.defs'

    class NoSuchUserException(FormattedException):
        def __init__(self, user, *args, **kwargs):
            super(ClPwd.NoSuchUserException, self).__init__({
                'message': "No such user (%(user)s)",
                'context': {'user': user}
            }, *args, **kwargs)

    def __init__(self, min_uid=None):
        self._user_key_map = {}
        self._uid_key_map = {}
        self._user_full_map = {}
        self._uid_full_map = {}
        if min_uid is None:
            self._min_uid = self.get_sys_min_uid(500)
        else:
            self._min_uid = min_uid

    def get_user_dict(self):
        self._load_passwd_database()
        return self._user_key_map

    def get_uid_dict(self):
        self._load_passwd_database()
        return self._uid_key_map

    def get_user_full_dict(self):
        self._load_passwd_database()
        return self._user_full_map

    def get_uid_full_dict(self):
        self._load_passwd_database()
        return self._uid_full_map

    def get_pw_by_name(self, user):
        """
        Return pw_entry for user
        """
        try:
            return self.get_user_full_dict()[user]
        except KeyError as e:
            raise ClPwd.NoSuchUserException(user) from e

    def get_pw_by_uid(self, uid):
        """
        Return list of passwd entries for uid
        """
        try:
            return self.get_uid_full_dict()[uid]
        except KeyError as e:
            raise ClPwd.NoSuchUserException(uid) from e

    def get_uid(self, user):
        """
        Returns uid for user
        """
        try:
            return self.get_user_full_dict()[user].pw_uid
        except KeyError as e:
            raise ClPwd.NoSuchUserException(user) from e

    def get_homedir(self, user):
        """
        Returns homedir for a user
        @param user: string
        @return: string
        """
        try:
            return self.get_user_full_dict()[user].pw_dir
        except KeyError as e:
            raise ClPwd.NoSuchUserException(user) from e

    def _load_passwd_database(self):
        """
        Loads the passwd database and fills user_to_uid and user_to_homedir maps
        """
        if not self._uid_full_map:
            for entry in pwd.getpwall():
                self._user_full_map[entry.pw_name] = entry
                if entry.pw_uid not in self._uid_full_map:
                    self._uid_full_map[entry.pw_uid] = []
                self._uid_full_map[entry.pw_uid].append(entry)
                if entry.pw_uid >= self._min_uid:
                    self._user_key_map[entry.pw_name] = entry
                    if entry.pw_uid not in self._uid_key_map:
                        self._uid_key_map[entry.pw_uid] = []
                    self._uid_key_map[entry.pw_uid].append(entry)

    def get_names(self, uid):
        """
        Return names of users with uid specified
        @param uid: int
        @return: list of strings
        """
        try:
            entries = self.get_uid_full_dict()[uid]
        except KeyError as e:
            raise ClPwd.NoSuchUserException(uid) from e

        return [entry.pw_name for entry in entries]

    def get_sys_min_uid(self, def_min_uid=500):
        """
        Return system defined MIN_UID from /etc/login.def or def_min_uid
        @param def_min_uid: int
        @return: MIN_UID: int
        """

        if os.path.exists(self.LOGIN_DEF_FILE):
            with open(self.LOGIN_DEF_FILE, 'r', encoding='utf-8') as f:
                lines = f.readlines()
            for line in lines:
                if line.startswith('UID_MIN'):
                    try:
                        return int(line.split('UID_MIN')[1].strip())
                    except ValueError:
                        pass

        return def_min_uid


def drop_user_privileges(user=None, effective_or_real=True, set_env=True):
    """
    Drop current root privileges to user
    :param effective_or_real: if True - drop euid, else - drop ruid
    :param user: name of unix user
    :param set_env: bool -> if true set $HOME and $USER env variables
    :return: None
    """
    current_euid = os.geteuid()
    if current_euid == 0 and user:
        user_pwd = pwd.getpwnam(user)
        # set user's groups
        user_groups = [group.gr_gid for group in grp.getgrall() if user in group.gr_mem]
        main_user_group = user_pwd.pw_gid
        if main_user_group not in user_groups:
            user_groups.append(main_user_group)
        os.setgroups(user_groups)
        # set effective uid and gid
        if effective_or_real:
            os.setegid(user_pwd.pw_gid)
            os.seteuid(user_pwd.pw_uid)
        else:
            os.setgid(user_pwd.pw_gid)
            os.setuid(user_pwd.pw_uid)
        if set_env:
            # set user's env vars
            os.environ['USER'] = user
            os.environ['HOME'] = user_pwd.pw_dir


@contextmanager
def drop_privileges(user):
    """
    Temporary drop privileges to some user
    :type user: str
    :raises: ClPwd.NoSuchUserException
    """
    old_uid, old_gid, old_groups = os.getuid(), os.getgid(), os.getgroups()
    try:
        drop_user_privileges(user, effective_or_real=True, set_env=False)
    except KeyError as e:
        raise ClPwd.NoSuchUserException(user) from e
    try:
        yield
    finally:
        os.seteuid(old_uid)
        os.setegid(old_gid)
        os.setgroups(old_groups)


def _resolve_doc_root_by_user(user):
    """
    Resolve document root by username
    :param user: str -> name of unix user
    :return: str -> document root
    """

    if user is None:
        raise FormattedException('Cannot resolve docroot without specified user')

    # to avoid circular imports
    from .cpapi import userdomains  # pylint: disable=cyclic-import,import-outside-toplevel
    from .cpapi.cpapiexceptions import NoDomain  # pylint: disable=cyclic-import,import-outside-toplevel

    domains_list = userdomains(user)
    # get document root for main domain
    try:
        _, result = domains_list[0]
    except IndexError as e:
        raise NoDomain({
            'message': 'No domain for user %(user)s found',
            'context': {'user': user},
        }) from e
    return result


def resolve_username_and_doc_root(user=None, domain=None):
    """
    Resolve username and doc_root by domain,
    or resolve document root by username,
    or resolve document root and username by effective uid
    :param user: str -> name of unix user
    :param domain: str -> domain of panel user
    :return: tuple -> user, doc_root
    """

    # to avoid circular imports
    from .cpapi import docroot  # pylint: disable=cyclic-import,import-outside-toplevel
    from .cpapi.cpapiexceptions import IncorrectData  # pylint: disable=cyclic-import,import-outside-toplevel

    result_user = user
    result_doc_root = None
    current_euid = os.geteuid()

    if domain is not None:
        doc_root, domain_user = docroot(domain)
        if user is None:
            result_user = domain_user
        elif user != domain_user:
            raise IncorrectData("User and domain are in conflict")
        result_doc_root = doc_root
    elif user is not None:  # we can obtain user name for domain
        result_doc_root = _resolve_doc_root_by_user(user=user)
    elif current_euid != 0:  # get doc_root and username by current euid
        result_user = pwd.getpwuid(current_euid).pw_name
        result_doc_root = _resolve_doc_root_by_user(user=result_user)

    return result_user, result_doc_root