unattended-upgrade

#!/usr/bin/python3
# Copyright (c) 2005-2018 Canonical Ltd
#
# AUTHOR:
# Michael Vogt <mvo@ubuntu.com>
# Balint Reczey <rbalint@ubuntu.com>

# This file is part of unattended-upgrades
#
# unattended-upgrades is free software; you can redistribute it and/or
# modify it under the terms of the GNU General Public License as published
# by the Free Software Foundation; either version 2 of the License, or (at
# your option) any later version.
#
# unattended-upgrades is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
# General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with unattended-upgrades; if not, write to the Free Software
# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
#

import atexit
import contextlib
import copy
import datetime
import errno
import email.charset
# workaround LP:2080940, email.errors changes as part of a security
# update in python itself but is lazy loaded so import early to ensure
import email.generator
import fcntl
import fnmatch
import gettext
import glob
try:
    from gi.repository.Gio import NetworkMonitor
except ImportError:
    pass
import grp
import inspect
import io
from importlib.abc import Loader
import importlib.util
import locale
import logging
import logging.handlers
import re
import os
import select
import signal
import socket
import string
import subprocess
import sys
import syslog

try:
    from typing import AbstractSet, cast, DefaultDict, Dict, Iterable, List
    AbstractSet  # pyflakes
    DefaultDict  # pyflakes
    Dict  # pyflakes
    Iterable  # pyflakes
    List  # pyflakes
    from typing import Optional, Set, Tuple, Union
    Optional  # pyflakes
    Set  # pyflakes
    Tuple  # pyflakes
    Union  # pyflakes
except ImportError:
    pass

from collections import defaultdict, namedtuple
from datetime import date
from email.message import Message
from gettext import gettext as _
from io import StringIO
from optparse import (
    OptionParser,
    SUPPRESS_HELP,
)

from subprocess import (
    Popen,
    PIPE,
)
from textwrap import wrap

import apt
import apt_inst
import apt_pkg

import distro_info

# workaround debian #1076097, it's unclear why we get the warning:
# "DeprecationWarning: This process (pid=3710789) is multi-threaded,
#  use of fork() may lead to deadlocks in the child."
# because nothing u-u/pyhton-apt/apt are not using threading but
# this is not useful to our users so supress it.
if not sys.warnoptions:
    import warnings
    warnings.filterwarnings("ignore", category=DeprecationWarning)


# the reboot required flag file used by packages
REBOOT_REQUIRED_FILE = "/var/run/reboot-required"
KEPT_PACKAGES_FILE = "var/lib/unattended-upgrades/kept-back"
MAIL_BINARY = "/usr/bin/mail"
SENDMAIL_BINARY = "/usr/sbin/sendmail"
USERS = "/usr/bin/users"


# no py3 lsb_release in debian :/
DISTRO_CODENAME = ""  # type: str
DISTRO_DESC = ""  # type: str
DISTRO_ID = ""  # type: str


def init_distro_info():
    global DISTRO_CODENAME, DISTRO_DESC, DISTRO_ID
    DISTRO_CODENAME = subprocess.check_output(
        ["lsb_release", "-c", "-s"], universal_newlines=True).strip()
    DISTRO_DESC = subprocess.check_output(
        ["lsb_release", "-d", "-s"], universal_newlines=True).strip()
    DISTRO_ID = subprocess.check_output(
        ["lsb_release", "-i", "-s"], universal_newlines=True).strip()


# init global distro info
init_distro_info()


# Number of days before release of devel where we enable unattended
# upgrades.
DEVEL_UNTIL_RELEASE = datetime.timedelta(days=21)

# progress information is written here
PROGRESS_LOG = "/var/run/unattended-upgrades.progress"
PID_FILE = "/var/run/unattended-upgrades.pid"
LOCK_FILE = "/var/run/unattended-upgrades.lock"

# set from the sigint signal handler
SIGNAL_STOP_REQUEST = False

# messages to be logged only once
logged_msgs = set()  # type: AbstractSet[str]

NEVER_PIN = -32768


class LoggingDateTime:
    """The date/time representation for the dpkg log file timestamps"""
    LOG_DATE_TIME_FMT = "%Y-%m-%d  %H:%M:%S"

    @classmethod
    def as_string(cls):
        # type: () -> str
        """Return the current date and time as LOG_DATE_TIME_FMT string"""
        return datetime.datetime.now().strftime(cls.LOG_DATE_TIME_FMT)

    @classmethod
    def from_string(cls, logstr):
        # type: (str) -> datetime.datetime
        """Take a LOG_DATE_TIME_FMT string and return datetime object"""
        return datetime.datetime.strptime(logstr, cls.LOG_DATE_TIME_FMT)


class UnknownMatcherError(ValueError):
    pass


class NoAllowedOriginError(ValueError):
    pass


PkgPin = namedtuple('PkgPin', ['pkg', 'priority'])
PkgFilePin = namedtuple('PkgFilePin', ['id', 'priority'])


class PluginDataPostrun(dict):
    """PluginResultData represents the result of the unattended upgrade
    operation for a plugin.

    It can be used as a dict or as a dataclass like object.
    """

    def __init__(self, dict):
        # type: (dict) -> None
        self.update(dict)

    @property
    def plugin_api(self):
        # type: () -> str
        """The API for the plugin interface.

        Major versions break compatiblity, minor versions only add fields.
        """
        return self["plugin_api"]

    @property
    def hostname(self):
        # type: () -> Optional[str]
        """The hostname of the system that u-u ran on"""
        return self["hostname"]

    @property
    def success(self):
        # type: () -> bool
        """Boolean state if u-u ran successfully"""
        return self["success"]

    @property
    def result(self):
        # type: () -> str
        """The result of the operation as a human readable string"""
        return self["result"]

    @property
    def packages_upgraded(self):
        # type () -> List[str]
        """List of strings with the package names that got upgraded"""
        return self.get("packages_upgraded")

    @property
    def packages_kept_back(self):
        # type () -> List[str]
        """List of strings with the package names that were held back"""
        return self.get("packages_kept_back")

    @property
    def packages_removed(self):
        # type () -> List[str]
        """List of strings with the package names that got removed"""
        return self.get("packages_removed")

    @property
    def packages_kept_installed(self):
        # type () -> List[str]
        """List of strings with the package names that are kept on hold"""
        return self.get("packages_kept_installed")

    @property
    def reboot_required(self):
        # type () -> boolean
        """Boolean value if a reboot is required"""
        return self.get("reboot_required")

    @property
    def log_dpkg(self):
        # type () -> str
        """The full dpkg output as a string"""
        return self.get("log_dpkg")

    @property
    def log_unattended_upgrades(self):
        # type () -> Optional[str]
        """The full unattended-upgrades log output as a string"""
        return self.get("log_unattended_upgrades")


class PluginManager:
    def __init__(self):
        # type: () -> None
        _plugin_dirs = [
            "/etc/unattended-upgrades/plugins/",
            "/usr/share/unattended-upgrades/plugins",
        ]
        cfg_plugin_paths = apt_pkg.config.value_list(
            "Unattended-Upgrade::Dirs::Plugins")
        if cfg_plugin_paths:
            _plugin_dirs.extend(cfg_plugin_paths)
        env_plugin_path = os.getenv("UNATTENDED_UPGRADES_PLUGIN_PATH")
        if env_plugin_path:
            _plugin_dirs.extend(env_plugin_path.split(":"))
        self._plugins = self._load_plugins(_plugin_dirs)

    def _load_plugins(self, paths):
        # type: (List[str]) -> AbstractSet[object]
        logging.debug("loading plugins from {}".format(paths))
        plugins = set()
        for path in paths:
            for p in glob.glob(path + "/*.py"):
                module_name = os.path.splitext(os.path.basename(p))[0]
                try:
                    plugin_spec = importlib.util.spec_from_file_location(module_name, p)
                    if plugin_spec is None:
                        raise ValueError(
                            "plugin_spec for %s returned None" % module_name)
                    mod = importlib.util.module_from_spec(plugin_spec)
                    assert isinstance(plugin_spec.loader, Loader)
                    plugin_spec.loader.exec_module(mod)
                except Exception as e:
                    logging.warn("cannot load plugin %s", e)
                    continue
                for __, member in inspect.getmembers(mod):
                    # required class name prefix
                    prefix = "UnattendedUpgradesPlugin"
                    if inspect.isclass(member) and member.__name__.startswith(prefix):
                        logging.debug("adding plugin %s %s", mod, member)
                        plugins.add(member())
        return plugins

    def _call_plugin_func(self, func_name, *args):
        # FIXME: add type annotations
        for plugin in self._plugins:
            plugin_func = getattr(plugin, func_name, None)
            if plugin_func is not None:
                try:
                    plugin_func(*args)
                except Exception as e:
                    logging.warning('cannot run "%s" in plugin %s: %s' % (
                        func_name, plugin, e))

    def postrun(self, res, uu_log, dpkg_log):
        # type: (UnattendedUpgradesResult, Optional[StringIO], str) -> None

        # this gets the current function name (e.g. "postrun")
        func_name = sys._getframe().f_code.co_name
        kept_back = set()
        # XXX: add "package-kept-back-details" only if someone asks (YAGNI)
        kept_back_details = []
        for origin, origin_pkgs in res.pkgs_kept_back.items():
            for pkg in origin_pkgs:
                kept_back.add(pkg)
                kept_back_details.append({"package": pkg, "origin": origin})
        # This is a custom dict because the expected main-use case for
        # this is webhook support so json serialization should be
        # trivial.  straightforward. The properties are there mostly
        # for documentation purposes.
        #
        # Keep in sync with the PluginResult properties
        result = PluginDataPostrun({
            # increment minor version very time something is added
            "plugin_api": "1.0",
            "hostname": host(),
            "success": res.success,
            "result": res.result_str,
            "packages_upgraded": res.pkgs,
            "packages_kept_back": sorted(list(kept_back)),
            "packages_removed": sorted(res.pkgs_removed),
            "packages_kept_installed": sorted(res.pkgs_kept_installed),
            "reboot_required": reboot_required(),
            "log_dpkg": dpkg_log,
        })
        if uu_log is not None:
            result["log_unattended_upgrades"] = uu_log.getvalue()
        self._call_plugin_func(func_name, result)


class UnattendedUpgradesCache(apt.Cache):

    def __init__(self, rootdir):
        # type: (str) -> None
        self._cached_candidate_pkgnames = set()  # type: Set[str]

        self.allowed_origins = get_allowed_origins()
        logging.info(_("Allowed origins are: %s"),
                     ", ".join(self.allowed_origins))

        self.blacklist = apt_pkg.config.value_list(
            "Unattended-Upgrade::Package-Blacklist")
        logging.info(_("Initial blacklist: %s"), " ".join(self.blacklist))

        self.whitelist = apt_pkg.config.value_list(
            "Unattended-Upgrade::Package-Whitelist")
        self.strict_whitelist = apt_pkg.config.find_b(
            "Unattended-Upgrade::Package-Whitelist-Strict", False)
        logging.info(_("Initial whitelist (%s): %s"),
                     "strict" if self.strict_whitelist else "not strict",
                     " ".join(self.whitelist))
        apt.Cache.__init__(self, rootdir=rootdir)

        # pre-heat lazy-loaded modules to avoid crash on python upgrade
        datetime.datetime.strptime("", "")

        # generate versioned_kernel_pkgs_regexp for later use
        self.versioned_kernel_pkgs_regexp = versioned_kernel_pkgs_regexp()
        self.running_kernel_pkgs_regexp = running_kernel_pkgs_regexp()
        if self.versioned_kernel_pkgs_regexp:
            logging.debug("Using %s regexp to find kernel packages",
                          self.versioned_kernel_pkgs_regexp.pattern)
        else:
            logging.debug("APT::VersionedKernelPackages is not set")
        if self.running_kernel_pkgs_regexp:
            logging.debug("Using %s regexp to find running kernel packages",
                          self.running_kernel_pkgs_regexp.pattern)

    def find_better_version(self, pkg):
        # type (apt.Package) -> apt.package.Version
        if pkg.is_installed and pkg.versions[0] > pkg.installed:
            logging.debug(
                "Package %s has a higher version available, checking if it is "
                "from an allowed origin and is not pinned down.", pkg.name)
            for v in pkg.versions:
                if pkg.installed < v \
                   and pkg.installed.policy_priority <= v.policy_priority \
                   and is_in_allowed_origin(v, self.allowed_origins):
                    return v
        return None

    def find_kept_packages(self, dry_run):
        # type: (bool) -> KeptPkgs
        """ Find kept packages not collected already """

        kept_packages = KeptPkgs(set)
        if dry_run:
            logging.info(_("The list of kept packages can't be calculated in "
                           "dry-run mode."))
            return kept_packages
        for pkg in self:
            better_version = self.find_better_version(pkg)
            if better_version:
                logging.info(self.kept_package_excuse(pkg._pkg,
                                                      self.blacklist,
                                                      self.whitelist,
                                                      self.strict_whitelist,
                                                      better_version))
                kept_packages.add(pkg, better_version, self)
        return kept_packages

    def kept_package_excuse(self, pkg,          # apt.Package
                            blacklist,          # type: List[str]
                            whitelist,          # type: List[str]
                            strict_whitelist,   # type: bool
                            better_version      # type: apt.package.Version
                            ):
        # type: (...) -> str
        """ Log the excuse the package is kept back for """
        if pkg.selected_state == apt_pkg.SELSTATE_HOLD:
            return _("Package %s is marked to be held back.") % pkg.name
        elif is_pkgname_in_blacklist(pkg.name, blacklist):
            return _("Package %s is blacklisted.") % pkg.name
        elif whitelist:
            if strict_whitelist:
                if not is_pkgname_in_whitelist(pkg.name, whitelist):
                    return (_(
                        "Package %s is not on the strict whitelist.")
                        % pkg.name)
                else:
                    if not is_pkgname_in_whitelist(pkg.name, whitelist):
                        return (_(
                            "Package %s is not whitelisted and it is not a"
                            " dependency of a whitelisted package.")
                            % pkg.name)
        elif not any([o.trusted for o in better_version.origins]):
            return _("Package %s's origin is not trusted.") % pkg.name
        return (_("Package %s is kept back because a related package"
                  " is kept back or due to local apt_preferences(5).")
                % pkg.name)

    def pinning_from_regex_list(self, regexps, priority):
        # type: (List[str], int) -> List[PkgPin]
        """ Represent blacklist as Python regexps as list of pkg pinnings"""

        pins = []  # type: List[PkgPin]
        for regex in regexps:
            if python_regex_is_posix(regex):
                pins.append(PkgPin('/^' + regex + '/', priority))
            else:
                # Python regex is not also an equivalent POSIX regexp.
                # This is expected to be rare. Go through all the package names
                # and pin all the matching ones.
                for pkg in self._cache.packages:
                    if re.match(regex, pkg.name):
                        pins.append(PkgPin(pkg.name, priority))
        return pins

    def pinning_from_config(self):
        # type: () -> List[Union[PkgPin, PkgFilePin]]
        """ Represent configuration as list of pinnings

            Assumes self.allowed_origins to be already set.
        """

        pins = []  # type: List[Union[PkgPin, PkgFilePin]]

        # mark not allowed origins with 'never' pin
        for pkg_file in self._cache.file_list:  # type: ignore
            if not is_allowed_origin(pkg_file, self.allowed_origins):
                # Set the magic 'never' pin on not allowed origins
                logging.debug("Marking not allowed %s with %s pin", pkg_file,
                              NEVER_PIN)
                pins.append(PkgFilePin(pkg_file.id, NEVER_PIN))
            # TODO(rbalint) pin not trusted origins with NEVER_PIN
            elif self.strict_whitelist:
                # set even allowed origins to -1 and set individual package
                # priorities up later
                pins.append(PkgFilePin(pkg_file.id, -1))

        # mark blacklisted packages with 'never' pin
        pins.extend(self.pinning_from_regex_list(  # type: ignore
            self.blacklist, NEVER_PIN))
        # set priority of whitelisted packages to high
        pins.extend(self.pinning_from_regex_list(  # type: ignore
            self.whitelist, 900))
        if self.strict_whitelist:
            policy = self._depcache.policy
            # pin down already pinned packages which are not on the whitelist
            # to not install locally pinned up packages accidentally
            for pkg in self._cache.packages:
                if pkg.has_versions:
                    pkg_ver = policy.get_candidate_ver(pkg)  # type: ignore
                    if pkg_ver is not None \
                       and policy.get_priority(pkg_ver) > -1:
                        # the pin is higher than set for allowed origins, thus
                        # there is extra pinning configuration
                        if not is_pkgname_in_whitelist(pkg.name,
                                                       self.whitelist):
                            pins.append(PkgPin(pkg.name, NEVER_PIN))

        return pins

    def apply_pinning(self, pins):
        # type: (List[Union[PkgPin, PkgFilePin]]) -> None
        """ Apply the list of pins """

        policy = self._depcache.policy
        pkg_files = {f.id: f for f in self._cache.file_list}  # type: ignore
        for pin in pins:
            logging.debug("Applying pinning: %s" % str(pin))
            if isinstance(pin, PkgPin):
                policy.create_pin('Version', pin.pkg, '*',  # type: ignore
                                  pin.priority)
            elif isinstance(pin, PkgFilePin):
                logging.debug("Applying pin %s to package_file: %s"
                              % (pin.priority, str(pkg_files[pin.id])))
                policy.set_priority(pkg_files[pin.id],  # type: ignore
                                    pin.priority)

    def open(self, progress=None):
        # type: (Optional[apt.progress.base.OpProgress]) -> None
        apt.Cache.open(self, progress)
        # apply pinning generated from unattended-upgrades configuration
        self.apply_pinning(self.pinning_from_config())

    def adjust_candidate(self, pkg):
        # type: (apt.Package) -> bool
        """ Adjust origin and return True if adjustment took place

            This is needed when e.g. a package is available in
            the security pocket but there is also a package in the
            updates pocket with a higher version number
        """
        try:
            new_cand = ver_in_allowed_origin(pkg, self.allowed_origins)
            # Only adjust to lower versions to avoid flipping back and forth
            # and to avoid picking a newer version, not selected by apt.
            # This helps avoiding upgrades to experimental's packages.
            if pkg.candidate is not None and new_cand < pkg.candidate:
                logging.debug(
                    "adjusting candidate to version %s in allowed "
                    "origin %s" % (new_cand, new_cand.origins))
                pkg.candidate = new_cand
                return True
            else:
                return False
        except NoAllowedOriginError:
            return False

    def call_checked(self, function, pkg, **kwargs):
        """ Call function and check if package is in the wanted state
        """
        try:
            function(pkg, **kwargs)
        except SystemError as e:
            logging.warning(
                _("package %s upgradable but fails to "
                  "be marked for upgrade (%s)"), pkg.name, e)
            self.clear()
            return False

        return ((function == apt.package.Package.mark_upgrade
                 or function == apt.package.Package.mark_install)
                and (pkg.marked_upgrade or pkg.marked_install))

    def call_adjusted(self, function, pkg, **kwargs):
        """Call function, but with adjusting
           packages in changes to come from allowed origins

           Note that as a side effect more package's candidate can be
           adjusted than only the one's in the final changes set.
        """
        new_pkgs_to_adjust = []  # List[str]

        if not is_pkg_change_allowed(pkg, self.blacklist, self.whitelist,
                                     self.strict_whitelist):
            return

        if function == apt.package.Package.mark_upgrade \
                and not pkg.is_upgradable:
            if not apt_pkg.config.find_b("Unattended-Upgrade::Allow-downgrade",
                                         False):
                return
            else:
                function = apt.package.Package.mark_install
        marking_succeeded = self.call_checked(function, pkg, **kwargs)

        if (not marking_succeeded
            or not check_changes_for_sanity(self, desired_pkg=pkg)) \
                and allow_marking_fallback():
            logging.debug("falling back to adjusting %s's dependencies"
                          % pkg.name)
            self.clear()
            # adjust candidates in advance if needed
            for pkg_name in self._cached_candidate_pkgnames:
                self.adjust_candidate(self[pkg_name])

            self.adjust_candidate(pkg)
            for dep in transitive_dependencies(pkg, self, level=1):
                try:
                    self.adjust_candidate(self[dep])
                except KeyError:
                    pass

            self.call_checked(function, pkg, **kwargs)

        for marked_pkg in self.get_changes():
            if marked_pkg.name in self._cached_candidate_pkgnames:
                continue
            if not is_in_allowed_origin(marked_pkg.candidate,
                                        self.allowed_origins):
                try:
                    ver_in_allowed_origin(marked_pkg,
                                          self.allowed_origins)
                    # important! this avoids downgrades below
                    if pkg.is_installed and not pkg.is_upgradable and \
                            apt_pkg.config.find_b("Unattended-Upgrade::Allow-"
                                                  "downgrade", False):
                        continue
                    new_pkgs_to_adjust.append(marked_pkg)
                except NoAllowedOriginError:
                    pass

        if new_pkgs_to_adjust:
            new_pkg_adjusted = False
            for pkg_to_adjust in new_pkgs_to_adjust:
                if self.adjust_candidate(pkg_to_adjust):
                    self._cached_candidate_pkgnames.add(pkg_to_adjust.name)
                    new_pkg_adjusted = True
            if new_pkg_adjusted:
                self.call_adjusted(function, pkg, **kwargs)

    def mark_upgrade_adjusted(self, pkg, **kwargs):
        self.call_adjusted(apt.package.Package.mark_upgrade, pkg, **kwargs)

    def mark_install_adjusted(self, pkg, **kwargs):
        self.call_adjusted(apt.package.Package.mark_install, pkg, **kwargs)


class LogInstallProgress(apt.progress.base.InstallProgress):
    """ Install progress that writes to self.progress_log
        (/var/run/unattended-upgrades.progress by default)
    """

    def __init__(self, logfile_dpkg, verbose=False,
                 progress_log="var/run/unattended-upgrades.progress"):
        # type: (str, bool, str) -> None
        apt.progress.base.InstallProgress.__init__(self)
        self.logfile_dpkg = logfile_dpkg
        self.progress_log = os.path.join(apt_pkg.config.find_dir("Dir"),
                                         progress_log)
        self.verbose = verbose
        self.output_logfd = None  # type: Optional[int]

    def status_change(self, pkg, percent, status):
        # type: (str, float, str) -> None
        with open(self.progress_log, "w") as f:
            f.write(_("Progress: %s %% (%s)") % (percent, pkg))

    def _fixup_fds(self):
        # () -> None
        required_fds = [0, 1, 2,  # stdin, stdout, stderr
                        self.writefd,
                        self.write_stream.fileno(),
                        self.statusfd,
                        self.status_stream.fileno()
                        ]
        # ensure that our required fds close on exec
        for fd in required_fds[3:]:
            old_flags = fcntl.fcntl(fd, fcntl.F_GETFD)
            fcntl.fcntl(fd, fcntl.F_SETFD, old_flags | fcntl.FD_CLOEXEC)
        # close all fds
        proc_fd = "/proc/self/fd"
        if os.path.exists(proc_fd):
            error_count = 0
            for fdname in os.listdir(proc_fd):
                try:
                    fd = int(fdname)
                except Exception:
                    print("ERROR: can not get fd for %s" % fdname)
                if fd in required_fds:
                    continue
                try:
                    os.close(fd)
                    # print("closed: ", fd)
                except OSError as e:
                    # there will be one fd that can not be closed
                    # as its the fd from pythons internal diropen()
                    # so its ok to ignore one close error
                    error_count += 1
                    if error_count > 1:
                        print("ERROR: os.close(%s): %s" % (fd, e))

    def _redirect_stdin(self):
        # type: () -> None
        REDIRECT_INPUT = os.devnull
        fd = os.open(REDIRECT_INPUT, os.O_RDWR)
        os.dup2(fd, 0)

    def _redirect_output(self):
        # type: () -> None
        # do not create log in dry-run mode, just output to stdout/stderr
        if not apt_pkg.config.find_b("Debug::pkgDPkgPM", False):
            logfd = self._get_logfile_dpkg_fd()
            os.dup2(logfd, 1)
            os.dup2(logfd, 2)

    def _get_logfile_dpkg_fd(self):
        # type: () -> int
        logfd = os.open(
            self.logfile_dpkg, os.O_RDWR | os.O_APPEND | os.O_CREAT, 0o640)
        try:
            adm_gid = grp.getgrnam("adm").gr_gid
            os.fchown(logfd, 0, adm_gid)
        except (KeyError, OSError):
            pass
        return logfd

    def update_interface(self):
        # type: () -> None
        # call super class first
        apt.progress.base.InstallProgress.update_interface(self)
        self._do_verbose_output_if_needed()

    def _do_verbose_output_if_needed(self):
        # type: () -> None
        # if we are in debug mode, nothing to be more verbose about
        if apt_pkg.config.find_b("Debug::pkgDPkgPM", False):
            return
        # handle verbose
        if self.verbose:
            if self.output_logfd is None:
                self.output_logfd = os.open(self.logfile_dpkg, os.O_RDONLY)
                os.lseek(self.output_logfd, 0, os.SEEK_END)
            try:
                select.select([self.output_logfd], [], [], 0)
                # FIXME: this should be OSError, but in py2.7 it is still
                #        select.error
            except select.error as e:
                if e.errno != errno.EINTR:  # type: ignore
                    logging.exception("select failed")
            # output to stdout in verbose mode only
            os.write(1, os.read(self.output_logfd, 1024))

    def _log_in_dpkg_log(self, msg):
        # type: (str) -> None
        logfd = self._get_logfile_dpkg_fd()
        os.write(logfd, msg.encode("utf-8"))
        os.close(logfd)

    def finish_update(self):
        # type: () -> None
        self._log_in_dpkg_log("Log ended: %s\n\n"
                              % LoggingDateTime.as_string())

    def __del__(self):
        # this can be removed once
        #   https://salsa.debian.org/apt-team/python-apt/-/merge_requests/64
        # is merged everywhere
        if hasattr(self, "status_stream"):
            self.status_stream.close()
        if hasattr(self, "write_stream"):
            self.write_stream.close()

    def fork(self):
        # type: () -> int
        self._log_in_dpkg_log("Log started: %s\n"
                              % LoggingDateTime.as_string())
        pid = os.fork()
        if pid == 0:
            self._fixup_fds()
            self._redirect_stdin()
            self._redirect_output()
        return pid


class Unlocked:
    """
    Context manager for unlocking the apt lock while cache.commit() is run
    """

    def __enter__(self):
        # type: () -> None
        try:
            apt_pkg.pkgsystem_unlock_inner()
        except Exception:
            # earlier python-apt used to leak lock
            logging.warning("apt_pkg.pkgsystem_unlock() failed due to not "
                            "holding the lock but trying to continue")
            pass

    def __exit__(self, exc_type, exc_value, exc_tb):
        # type: (object, object, object) -> None
        apt_pkg.pkgsystem_lock_inner()


class KeptPkgs(defaultdict):
    """
    Packages to keep by highest allowed pretty-printed origin

    """
    def add(self, pkg,  # type: apt.Package
            version,    # type: apt.package.Version
            cache       # type: UnattendedUpgradesCache
            ):
        # type: (...) -> None
        for origin in version.origins:
            if is_allowed_origin(origin, cache.allowed_origins):
                self[origin.origin + " " + origin.archive].add(pkg.name)
                return


class UnattendedUpgradesResult:
    """
    Represent the (potentially partial) results of an unattended-upgrades
    run
    """
    def __init__(self,
                 success,                 # type: bool
                 result_str="",           # type: str
                 pkgs=[],                 # type: List[str]
                 pkgs_kept_back=KeptPkgs(set),     # type: KeptPkgs
                 pkgs_removed=[],         # type: List[str]
                 pkgs_kept_installed=[],  # type: List[str]
                 update_stamp=False       # type: bool
                 ):
        # type: (...) -> None
        self.success = success
        self.result_str = result_str
        self.pkgs = pkgs
        self.pkgs_kept_back = pkgs_kept_back
        self.pkgs_removed = pkgs_removed
        self.pkgs_kept_installed = pkgs_kept_installed
        self.update_stamp = update_stamp


def is_dpkg_journal_dirty():
    # type: () -> bool
    """
    Return True if the dpkg journal is dirty
    (similar to debSystem::CheckUpdates)
    """
    d = os.path.join(
        os.path.dirname(apt_pkg.config.find_file("Dir::State::status")),
        "updates")
    for f in os.listdir(d):
        if re.match("[0-9]+", f):
            return True
    return False


def reboot_required():
    # type: () -> bool
    return os.path.isfile(REBOOT_REQUIRED_FILE)


def signal_handler(signal, frame):
    # type: (int, object) -> None
    logging.warning("SIGTERM received, will stop")
    global SIGNAL_STOP_REQUEST
    SIGNAL_STOP_REQUEST = True


def log_once(msg):
    # type: (str) -> None
    global logged_msgs
    if msg not in logged_msgs:
        logging.info(msg)
        logged_msgs.add(msg)  # type: ignore


def should_stop():
    # type: () -> bool
    """
    Return True if u-u needs to stop due to signal received or due to the
    system started to run on battery.
    """
    if SIGNAL_STOP_REQUEST:
        logging.warning("SIGNAL received, stopping")
        return True
    try:
        if apt_pkg.config.find_b("Unattended-Upgrade::OnlyOnACPower", True) \
           and subprocess.call("on_ac_power") == 1:
            logging.warning("System is on battery power, stopping")
            return True
    except FileNotFoundError:
        log_once(
            _("Checking if system is running on battery is skipped. Please "
              "install powermgmt-base package to check power status and skip "
              "installing updates when the system is running on battery."))
    if apt_pkg.config.find_b(
            "Unattended-Upgrade::Skip-Updates-On-Metered-Connections", True):
        try:
            if NetworkMonitor.get_network_metered(
                    NetworkMonitor.get_default()):
                logging.warning(_("System is on metered connection, stopping"))
                return True
        except NameError:
            log_once(_("Checking if connection is metered is skipped. Please "
                       "install python3-gi package to detect metered "
                       "connections and skip downloading updates."))
    return False


def substitute(line):
    # type: (str) -> str
    """ substitude known mappings and return a new string

    Currently supported ${distro-release}
    """
    mapping = {"distro_codename": get_distro_codename(),
               "distro_id": get_distro_id()}
    return string.Template(line).substitute(mapping)


def get_distro_codename():
    # type: () -> str
    return DISTRO_CODENAME


def get_distro_id():
    # type: () -> str
    return DISTRO_ID


def allow_marking_fallback():
    # type: () -> bool
    return apt_pkg.config.find_b(
        "Unattended-Upgrade::Allow-APT-Mark-Fallback",
        get_distro_codename() != "sid")


def versioned_kernel_pkgs_regexp():
    apt_versioned_kernel_pkgs = apt_pkg.config.value_list(
        "APT::VersionedKernelPackages")
    if apt_versioned_kernel_pkgs:
        return re.compile("(" + "|".join(
            ["^" + p + "-[1-9][0-9]*\\.[0-9]+\\.[0-9]+-[0-9]+(-.+)?$"
             for p in apt_versioned_kernel_pkgs]) + ")")
    else:
        return None


def running_kernel_pkgs_regexp():
    apt_versioned_kernel_pkgs = apt_pkg.config.value_list(
        "APT::VersionedKernelPackages")
    if apt_versioned_kernel_pkgs:
        running_kernel_version = subprocess.check_output(
            ["uname", "-r"], universal_newlines=True).rstrip()
        kernel_escaped = re.escape(running_kernel_version)
        try:
            kernel_noflavor_escaped = re.escape(
                re.match("[1-9][0-9]*\\.[0-9]+\\.[0-9]+-[0-9]+",
                         running_kernel_version)[0])
            return re.compile("(" + "|".join(
                [("^" + p + "-" + kernel_escaped + "$|^"
                  + p + "-" + kernel_noflavor_escaped + "$")
                 for p in apt_versioned_kernel_pkgs]) + ")")
        except TypeError:
            # flavor could not be cut from version
            return re.compile("(" + "|".join(
                [("^" + p + "-" + kernel_escaped + "$")
                 for p in apt_versioned_kernel_pkgs]) + ")")
    else:
        return None


def get_allowed_origins_legacy():
    # type: () -> List[str]
    """ legacy support for old Allowed-Origins var """
    allowed_origins = []  # type: List[str]
    key = "Unattended-Upgrade::Allowed-Origins"
    try:
        for s in apt_pkg.config.value_list(key):
            # if there is a ":" use that as seperator, else use spaces
            if re.findall(r'(?<!\\):', s):
                (distro_id, distro_codename) = re.split(r'(?<!\\):', s)
            else:
                (distro_id, distro_codename) = s.split()
            # unescape "\:" back to ":"
            distro_id = re.sub(r'\\:', ':', distro_id)
            # escape "," (see LP: #824856) - can this be simpler?
            distro_id = re.sub(r'([^\\]),', r'\1\\,', distro_id)
            distro_codename = re.sub(r'([^\\]),', r'\1\\,', distro_codename)
            # convert to new format
            allowed_origins.append("o=%s,a=%s" % (substitute(distro_id),
                                   substitute(distro_codename)))
    except ValueError:
        logging.error(_("Unable to parse %s." % key))
        raise
    return allowed_origins


def get_allowed_origins():
    # type: () -> List[str]
    """ return a list of allowed origins from apt.conf

    This will take substitutions (like distro_id) into account.
    """
    allowed_origins = get_allowed_origins_legacy()
    key = "Unattended-Upgrade::Origins-Pattern"
    try:
        for s in apt_pkg.config.value_list(key):
            allowed_origins.append(substitute(s))
    except ValueError:
        logging.error(_("Unable to parse %s." % key))
        raise
    return allowed_origins


def match_whitelist_string(whitelist, origin):
    # type: (str, Union[apt.package.Origin, apt_pkg.PackageFile]) -> bool
    """
    take a whitelist string in the form "origin=Debian,label=Debian-Security"
    and match against the given python-apt origin. A empty whitelist string
    never matches anything.
    """
    whitelist = whitelist.strip()
    if whitelist == "":
        logging.warning("empty match string matches nothing")
        return False
    res = True
    # make "\," the html quote equivalent
    whitelist = whitelist.replace("\\,", "%2C")
    for token in whitelist.split(","):
        # strip and unquote the "," back
        (what, value) = [s.strip().replace("%2C", ",")
                         for s in token.split("=")]
        # logging.debug("matching %s=%s against %s" % (
        #              what, value, origin))
        # support substitution here as well
        value = substitute(value)
        # first char is apt-cache policy output, send is the name
        # in the Release file
        if what in ("o", "origin"):
            match = fnmatch.fnmatch(origin.origin, value)
        elif what in ("l", "label"):
            match = fnmatch.fnmatch(origin.label, value)
        elif what in ("a", "suite", "archive"):
            match = fnmatch.fnmatch(origin.archive, value)
        elif what in ("c", "component"):
            match = fnmatch.fnmatch(origin.component, value)
        elif what in ("site",):
            match = fnmatch.fnmatch(origin.site, value)
        elif what in ("n", "codename",):
            match = fnmatch.fnmatch(origin.codename, value)
        else:
            raise UnknownMatcherError(
                "Unknown whitelist entry for matcher %s (token %s)" % (
                    what, token))
        # update res
        res = res and match
        # logging.debug("matching %s=%s against %s" % (
        #              what, value, origin))
    return res


def python_regex_is_posix(expression):
    # type: (str) -> bool
    """ Returns if the Python regex is also an equivalent POSIX regex """
    return re.match("^[-a-zA-Z0-9\\^\\$\\+\\.:]*$", expression) is not None


def cache_commit(cache,           # type: apt.Cache
                 logfile_dpkg,    # type: str
                 verbose,         # type: bool
                 iprogress=None,  # type: Optional[apt.progress.base.InstallProgress]
                 ):
    # type: (...) -> Tuple[bool, Optional[Exception]]
    """Commit the changes from the given cache to the system"""

    error = None
    res = False
    if iprogress is None:
        iprogress = LogInstallProgress(logfile_dpkg, verbose)

    try:
        res = cache.commit(install_progress=iprogress)
        cache.open()
    except SystemError as e:
        error = e
        if verbose:
            logging.exception("Exception happened during upgrade.")
        cache.clear()
    return res, error


def upgrade_normal(cache, logfile_dpkg, verbose):
    # type: (apt.Cache, str, bool) -> bool
    res, error = cache_commit(cache, logfile_dpkg, verbose)
    if res:
        logging.info(_("All upgrades installed"))
    else:
        logging.error(_("Installing the upgrades failed!"))
        logging.error(_("error message: %s"), error)
        logging.error(_("dpkg returned a error! See %s for details"),
                      logfile_dpkg)
    return res


def upgrade_in_minimal_steps(cache,            # type: UnattendedUpgradesCache
                             pkgs_to_upgrade,  # type: List[str]
                             logfile_dpkg="",  # type: str
                             verbose=False,    # type: bool
                             ):
    # type: (...) -> bool
    install_log = LogInstallProgress(logfile_dpkg, verbose)

    res = True

    # to upgrade contains the package names
    to_upgrade = set(pkgs_to_upgrade)
    for pkgname in upgrade_order(to_upgrade, cache):
        # upgrade packages and dependencies in increasing expected size of
        # package sets to upgrade/install together
        if pkgname not in to_upgrade:
            # pkg is upgraded in a previous set
            continue
        if should_stop():
            return False
        pkg = cache[pkgname]
        try:
            if pkg.is_upgradable \
               or candidate_version_changed(pkg):
                cache.mark_upgrade_adjusted(
                    pkg, from_user=not pkg.is_auto_installed)
            elif not pkg.is_installed:
                cache.mark_install_adjusted(pkg, from_user=False)
            else:
                continue
        except Exception as e:
            logging.warning(
                _("package %s upgradable but fails to "
                  "be marked for upgrade (%s)"), pkgname, e)
            cache.clear()
            res = False
            continue

        # double check that we are not running into side effects like
        # what could have been caused LP: #1020680
        if not check_changes_for_sanity(cache):
            logging.info("While building minimal partition: "
                         "cache has not allowed changes")
            cache.clear()
            continue
        changes = [p.name for p in cache.get_changes()]
        if not changes:
            continue

        # write progress log information
        if len(pkgs_to_upgrade) > 0:
            all_count = len(pkgs_to_upgrade)
            remaining_count = all_count - len(to_upgrade)
            percent = remaining_count / float(all_count * 100.0)
        else:
            percent = 100.0
        install_log.status_change(pkg=",".join(changes),
                                  percent=percent,
                                  status="")
        # apply changes
        logging.debug("applying set %s" % changes)

        res, error = cache_commit(cache, logfile_dpkg, verbose, install_log)
        if error:
            if verbose:
                logging.exception("Exception happened during upgrade.")
            logging.error(_("Installing the upgrades failed!"))
            logging.error(_("error message: %s"), error)
            logging.error(_("dpkg returned a error! See %s for details"),
                          logfile_dpkg)
            return False
        to_upgrade = to_upgrade - set(changes)
        logging.debug("left to upgrade %s" % to_upgrade)
        if len(to_upgrade) == 0:
            logging.info(_("All upgrades installed"))
            break
    return res


def is_allowed_origin(origin, allowed_origins):
    # type: (Union[apt.package.Origin, apt_pkg.PackageFile], List[str]) -> bool

    # local origin is allowed by default
    if origin.component == 'now' and origin.archive == 'now' and \
       not origin.label and not origin.site:
        return True
    for allowed in allowed_origins:
        if match_whitelist_string(allowed, origin):
            return True
    return False


def is_in_allowed_origin(ver, allowed_origins):
    # type: (apt.package.Version, List[str]) -> bool
    if not ver:
        return False
    for origin in ver.origins:
        if is_allowed_origin(origin, allowed_origins):
            return True
    return False


def ver_in_allowed_origin(pkg, allowed_origins):
    # type: (apt.Package, List[str]) -> apt.package.Version
    for ver in pkg.versions:
        if is_in_allowed_origin(ver, allowed_origins):
            # leave as soon as we have the highest new candidate
            return ver
    raise NoAllowedOriginError()


def is_pkgname_in_blacklist(pkgname, blacklist):
    # type: (str, List[str]) -> bool
    for blacklist_regexp in blacklist:
        if re.match(blacklist_regexp, pkgname):
            logging.debug("skipping blacklisted package %s" % pkgname)
            return True
    return False


def is_pkgname_in_whitelist(pkgname, whitelist):
    # type: (str, List[str]) -> bool
    # a empty whitelist means the user does not want to use this feature
    if not whitelist:
        return True
    for whitelist_regexp in whitelist:
        if re.match(whitelist_regexp, pkgname):
            logging.debug("only upgrading the following package %s" %
                          pkgname)
            return True
    return False


def is_pkg_change_allowed(pkg, blacklist, whitelist, strict_whitelist):
    # type: (apt.Package, List[str], List[str], bool) -> bool
    if is_pkgname_in_blacklist(pkg.name, blacklist):
        logging.debug("pkg %s package has been blacklisted" % pkg.name)
        return False
    # a strict whitelist will not allow any changes not in the
    # whitelist, most people will want the relaxed whitelist
    # that whitelists a package but pulls in the package
    # dependencies
    if strict_whitelist and \
       not is_pkgname_in_whitelist(pkg.name, whitelist):

        logging.debug("pkg %s package is not whitelisted" %
                      pkg.name)
        return False
    if pkg._pkg.selected_state == apt_pkg.SELSTATE_HOLD:
        logging.debug("pkg %s is on hold" % pkg.name)
        return False
    return True


def transitive_dependencies(pkg,               # type: apt.Package
                            cache,             # type: apt.Cache
                            acc=set(),         # type AbstractSet[str]
                            valid_types=None,  # type: Optional[AbstractSet[str]]
                            level=None         # type: Optional[int]
                            ):
    # type (...) -> AbstractSet[str]
    """ All (transitive) dependencies of the package

        Note that alternative (|) dependencies are collected, too
    """
    if not pkg.candidate or level is not None and level < 1:
        return acc

    for dep in pkg.candidate.dependencies:
        for base_dep in dep:
            if base_dep.name not in acc:
                if not valid_types or base_dep.rawtype in valid_types:
                    acc.add(base_dep.name)
                    try:
                        transitive_dependencies(
                            cache[base_dep.name], cache, acc, valid_types,
                            level=(level - 1 if level is not None else None))
                    except KeyError:
                        pass
    return acc


def upgrade_order(to_upgrade, cache):
    # type: (AbstractSet[str], apt.Cache) -> List[str]
    """  Sort pkg names by the expected number of other packages to be upgraded
         with it. The calculation is not 100% accurate, it is an approximation.
    """

    upgrade_set_sizes = {}
    # calculate upgrade sets
    follow_deps = {'Depends', 'PreDepends', 'Recommends'}
    for pkgname in to_upgrade:
        pkg = cache[pkgname]
        upgrade_set_sizes[pkgname] = len(transitive_dependencies(
            pkg, cache, valid_types=follow_deps).intersection(to_upgrade))
    return sorted(upgrade_set_sizes, key=upgrade_set_sizes.get)  # type: ignore


def check_changes_for_sanity(cache, desired_pkg=None):
    # type: (UnattendedUpgradesCache, Optional[apt.Package]) -> bool
    sanity_check_result = sanity_problem(cache, desired_pkg)
    if sanity_check_result is None:
        return True
    else:
        logging.debug("sanity check failed for: %s : %s"
                      % (str({str(p.candidate) for p in cache.get_changes()}),
                         sanity_check_result))
        return False


def sanity_problem(cache, desired_pkg):
    # type: (UnattendedUpgradesCache, Optional[apt.Package]) -> Optional[str]
    if cache._depcache.broken_count != 0:
        return ("there are broken packages in the cache")
    # If there are no packages to be installed they were kept back
    if cache.install_count == 0:
        return ("no package is selected to be upgraded or installed")
    changes = cache.get_changes()
    for pkg in changes:
        if pkg.marked_delete:
            return ("pkg %s is marked to be deleted" % pkg.name)
        if not pkg.candidate:
            return ("internal error: pkg %s has no candidate" % pkg.candidate)
        if pkg.marked_install or pkg.marked_upgrade:
            # apt will never fallback from a trusted to a untrusted
            # origin so its good enough if we have a single trusted one
            if not any([o.trusted for o in pkg.candidate.origins]):
                return ("pkg %s is not from a trusted origin" % pkg.name)
            if not is_in_allowed_origin(pkg.candidate, cache.allowed_origins):
                return ("pkg %s is not in an allowed origin" % pkg.name)
            if not is_pkg_change_allowed(pkg,
                                         cache.blacklist,
                                         cache.whitelist,
                                         cache.strict_whitelist):
                return ("pkg %s is blacklisted or is not whitelisted"
                        % pkg.name)
            # check if the package is unsafe to upgrade unattended
            ignore_require_restart = apt_pkg.config.find_b(
                "Unattended-Upgrade::IgnoreAppsRequireRestart", False)
            upgrade_requires = pkg.candidate.record.get("Upgrade-Requires")
            if pkg.marked_upgrade and ignore_require_restart is False \
               and upgrade_requires == "app-restart":
                return ("pkg %s requires app-restart, it is not safe to "
                        "upgrade it unattended")
    # check that the package we want to upgrade is in the change set
    if desired_pkg and desired_pkg not in changes:
        return ("pkg %s to be marked for upgrade/install is not marked "
                "accordingly" % desired_pkg.name)
    return None


def is_deb(file):
    # type: (str) -> bool
    if file.endswith(".deb"):
        return True
    else:
        return False


def pkgname_from_deb(debfile):
    # type: (str) -> str
    # FIXME: add error checking here
    try:
        control = apt_inst.DebFile(debfile).control.extractdata("control")
        sections = apt_pkg.TagSection(control)
        return sections["Package"]
    except (IOError, SystemError) as e:
        logging.error("failed to read deb file %s (%s)" % (debfile, e))
        # dumb fallback
        return debfile.split("_")[0]


def get_md5sum_for_file_in_deb(deb_file, conf_file):
    # type: (str, str) -> str
    dpkg_cmd = ["dpkg-deb", "--fsys-tarfile", deb_file]
    tar_cmd = ["tar", "-x", "-O", "-f", "-", "." + conf_file]
    md5_cmd = ["md5sum"]
    dpkg_p = Popen(dpkg_cmd, stdout=PIPE)
    tar_p = Popen(tar_cmd, stdin=dpkg_p.stdout, stdout=PIPE,
                  universal_newlines=True)
    md5_p = Popen(md5_cmd, stdin=tar_p.stdout, stdout=PIPE,
                  universal_newlines=True)
    pkg_md5sum = md5_p.communicate()[0].split()[0]
    for __p in [dpkg_p, tar_p, md5_p]:
        p = cast(Popen, __p)
        if p.stdout:
            p.stdout.close()
        p.wait()
    return pkg_md5sum


def get_md5sum_for_file_installed(conf_file, prefix):
    # type: (str, str) -> str
    try:
        with open(prefix + conf_file, 'rb') as fb:
            for hash_string in apt_pkg.Hashes(fb).hashes:  # type: ignore
                if hash_string.hashtype == 'MD5Sum':
                    return hash_string.hashvalue
            raise Exception("no MD5Sum hashtype found in apt_pkg.Hashes")
    except IsADirectoryError:
        # the package replaces a directory wih a configuration file
        #
        # if the package changed this way it is safe to assume that
        # the transition happens without showing a prompt but if the admin
        # created the directory the admin will need to resolve it after
        # being notified about the unexpected prompt
        logging.debug("found conffile %s is a directory on the system "
                      % conf_file)
        return "dir"
    except FileNotFoundError:
        # if the local file got deleted by the admin thats ok but it may still
        # trigger a conffile promp (see debian #788049)
        logging.debug("conffile %s in missing on the system" % conf_file)
        return ""


def map_conf_file(conf_file, conffiles):
    # type: (str, Union[AbstractSet[str], Dict[str, str]]) -> Optional[str]
    """Find respective conffile in a set of conffiles with some heuristics
    """
    if conf_file in conffiles:
        return conf_file
    elif os.path.join(conf_file, os.path.basename(conf_file)) in conffiles:
        # new /etc/foo may be old /etc/foo/foo, like in LP: #1822745
        return os.path.join(conf_file, os.path.basename(conf_file))
    elif os.path.dirname(conf_file) in conffiles:
        # new /etc/foo/foo may be old /etc/foo, probably by accident
        return os.path.dirname(conf_file)
    # TODO: peek into package's dpkg-maintscript-helper mv_conffile usage
    else:
        return None


# prefix is *only* needed for the build-in tests
def conffile_prompt(destFile, prefix=""):
    # type: (str, str) -> bool
    logging.debug("check_conffile_prompt(%s)" % destFile)
    pkgname = pkgname_from_deb(destFile)

    # get the conffiles for the /var/lib/dpkg/status file
    status_file = apt_pkg.config.find("Dir::State::status")
    with open(status_file, "r") as f:
        tagfile = apt_pkg.TagFile(f)
        conffiles = ""
        for section in tagfile:
            if section.get("Package") == pkgname:
                logging.debug("found pkg: %s" % pkgname)
                if "Conffiles" in section:
                    conffiles = section.get("Conffiles")
                    break

    # get conffile value from pkg, its ok if the new version
    # does not have conffiles anymore
    pkg_conffiles = set()  # type: AbstractSet[str]
    try:
        deb = apt_inst.DebFile(destFile)
        pkg_conffiles = set(deb.control.extractdata(
            "conffiles").strip().decode("utf-8").split("\n"))
    except SystemError as e:
        print(_("Apt returned an error, exiting"))
        print(_("error message: %s") % e)
        logging.error(_("Apt returned an error, exiting"))
        logging.error(_("error message: %s"), e)
        raise
    except LookupError as e:
        logging.debug("No conffiles in deb %s (%s)" % (destFile, e))
    if not pkg_conffiles:
        return False

    # Conffiles:
    #  /etc/bash_completion.d/m-a c7780fab6b14d75ca54e11e992a6c11c
    dpkg_status_conffiles = {}
    for line in conffiles.splitlines():
        # ignore empty lines
        line = line.strip()
        if not line:
            continue
        # show what we do
        logging.debug("conffile line: %s", line)
        li = line.split()
        conf_file = li[0]
        md5 = li[1]
        obs = None  # type: Optional[str]
        if len(li) > 2:
            obs = li[2]
        # ignore if conffile is obsolete
        if obs == "obsolete":
            continue
        # ignore state "newconffile" until its clearer if there
        # might be a dpkg prompt (LP: #936870)
        if md5 == "newconffile":
            continue
        new_conf_file = map_conf_file(conf_file, pkg_conffiles)
        if not new_conf_file:
            logging.debug("%s not in package conffiles %s" % (
                conf_file, pkg_conffiles))
            continue
        # record for later
        dpkg_status_conffiles[conf_file] = md5

        # test against the installed file, if the local file got deleted
        # by the admin thats ok but it may still trigger a conffile prompt
        # (see debian #788049)
        current_md5 = get_md5sum_for_file_installed(conf_file, prefix)
        logging.debug("current md5: %s" % current_md5)

        # hashes are the same, no conffile prompt
        if current_md5 == md5:
            continue
        # calculate md5sum from the deb (may take a bit)
        pkg_md5sum = get_md5sum_for_file_in_deb(destFile, new_conf_file)
        logging.debug("pkg_md5sum: %s" % pkg_md5sum)
        # the md5sum in the deb is unchanged, this will not
        # trigger a conffile prompt
        if pkg_md5sum == md5:
            continue
        # if we made it to this point:
        #  current_md5 != pkg_md5sum != md5
        # and that will trigger a conffile prompt, we can
        # stop processing at this point and just return True
        logging.debug("conffile prompt found for %s (%s)" % (conf_file, pkgname))
        return True

    # now check if there are conffiles in the pkg that where not there
    # in the previous version in the dpkg status file
    if pkg_conffiles:
        for conf_file in pkg_conffiles:
            old_conf_file = map_conf_file(conf_file, dpkg_status_conffiles)
            if not old_conf_file:
                pkg_md5sum = get_md5sum_for_file_in_deb(destFile, conf_file)
                current_md5 = get_md5sum_for_file_installed(conf_file, prefix)
                logging.debug("no old_conf_file, pkg_md5sum: %s, current_md5: %s" % (
                    pkg_md5sum, current_md5))
                if current_md5 != "" and pkg_md5sum != current_md5:
                    logging.debug("(old) conffile prompt found for %s (%s)" % (
                        conf_file, pkgname))
                    return True
    return False


def dpkg_conffile_prompt():
    # type: () -> bool
    if "DPkg::Options" not in apt_pkg.config:
        return True
    options = apt_pkg.config.value_list("DPkg::Options")
    for option in options:
        option = option.strip()
        if option in ["--force-confold", "--force-confnew"]:
            return False
    return True


def rewind_cache(cache, pkgs_to_upgrade):
    # type: (UnattendedUpgradesCache, List[apt.Package]) -> None
    """ set the cache back to the state with packages_to_upgrade """
    cache.clear()
    for pkg2 in pkgs_to_upgrade:
        cache.mark_install_adjusted(pkg2, from_user=not pkg2.is_auto_installed)
    if cache.broken_count > 0:
        raise AssertionError("rewind_cache created a broken cache")


def host():
    # type: () -> str
    return socket.getfqdn()


def wrap_indent(t, subsequent_indent=" "):
    # type: (str, str) -> str
    return "\n".join(wrap(t, break_on_hyphens=False,
                          subsequent_indent=subsequent_indent))


def setup_apt_listchanges(conf="/etc/apt/listchanges.conf"):
    # type: (str) -> None
    """ deal with apt-listchanges """
    # apt-listchanges will always send a mail if there is a mail address
    # set in the config regardless of the frontend used, so set it to
    # mail if we have a sendmail and to none if not (as it appears to
    # not check if sendmail is there or not), debian bug #579733
    if os.path.exists(SENDMAIL_BINARY):
        os.environ["APT_LISTCHANGES_FRONTEND"] = "mail"
    else:
        os.environ["APT_LISTCHANGES_FRONTEND"] = "none"


def _send_mail_using_mailx(from_address, to_address, subject, body):
    # type: (str, str, str, str) -> int
    # ensure that the body is a byte stream and that we do not
    # break on encoding errors (the default error mode is "strict")
    encoded_body = body.encode(
        locale.getpreferredencoding(False), errors="replace")
    # we use a binary pipe to stdin to ensure we do not break on
    # unicode encoding errors (e.g. because the user is running a
    # ascii only system like the buildds)
    mail = subprocess.Popen(
        [MAIL_BINARY, "-r", from_address, "-s", subject, to_address],
        stdin=subprocess.PIPE, universal_newlines=False)
    assert mail.stdin  # mypy
    mail.stdin.write(encoded_body)
    mail.stdin.close()
    ret = mail.wait()
    return ret


def _send_mail_using_sendmail(from_address, to_address, subject, body):
    # type: (str, str, str, str) -> int
    # format as a proper mail
    msg = Message()
    msg['Subject'] = subject
    msg['From'] = from_address
    msg['To'] = to_address
    msg['Auto-Submitted'] = "auto-generated"
    # order is important here, Message() first, then Charset()
    #  then msg.set_charset()
    charset = email.charset.Charset("utf-8")
    charset.body_encoding = email.charset.QP  # type: ignore
    msg.set_payload(body, charset)
    # and send it away
    sendmail = subprocess.Popen(
        [SENDMAIL_BINARY, "-oi", "-t"],
        stdin=subprocess.PIPE, universal_newlines=True)
    assert sendmail.stdin  # mypy
    sendmail.stdin.write(msg.as_string())
    sendmail.stdin.close()
    ret = sendmail.wait()
    return ret


def send_summary_mail(pkgs,                 # type: List[str]
                      res,                  # type: bool
                      result_str,           # type: str
                      pkgs_kept_back,       # type: Optional[KeptPkgs]
                      pkgs_removed,         # type: List[str]
                      pkgs_kept_installed,  # type: List[str]
                      mem_log,              # type: Optional[StringIO]
                      dpkg_log_content,     # type: str
                      ):
    # type: (...) -> None
    """ send mail (if configured in Unattended-Upgrade::Mail) """
    to_email = apt_pkg.config.find("Unattended-Upgrade::Mail", "")
    if not to_email:
        return
    if not os.path.exists(MAIL_BINARY) and not os.path.exists(SENDMAIL_BINARY):
        logging.error(_("No /usr/bin/mail or /usr/sbin/sendmail, "
                        "can not send mail. "
                        "You probably want to install the mailx package."))
        return

    # The admin may well wish to get a mail report regardless of what was done.
    # This is now set by Unattended-Upgrade::MailReport values of:
    #       "always", "only-on-error" or "on-change"
    # (you can achieve "never" by not setting Unattended-Upgrade::Mail).
    # If this is not set, then set it using any legacy MailOnlyOnError
    # setting (default True)
    #
    mail_opt = apt_pkg.config.find("Unattended-Upgrade::MailReport")
    if (mail_opt == ""):    # None set - map from legacy value
        if apt_pkg.config.find_b("Unattended-Upgrade::MailOnlyOnError", False):
            mail_opt = "only-on-error"
        else:
            mail_opt = "on-change"

    # if the operation was successful and the user has requested to get
    # mails only on errors, just exit here
    if (res and (mail_opt == "only-on-error")):
        return

    # if the run was successful but nothing had to be done skip sending email
    # unless the admin wants it anyway
    if (((mail_opt != "always") and res and not pkgs and not pkgs_kept_back
         and not pkgs_removed)):
        return

    # Check if reboot-required flag is present
    reboot_flag_str = _(
        "[reboot required]") if reboot_required() else ""
    # Check if packages are kept on hold
    hold_flag_str = (_("[package on hold]") if pkgs_kept_back
                     or pkgs_kept_installed else "")
    logging.debug("Sending mail to %s" % to_email)
    subject = _(
        "{hold_flag}{reboot_flag} unattended-upgrades result for "
        "{machine}: {result}").format(
            hold_flag=hold_flag_str, reboot_flag=reboot_flag_str,
            machine=host(), result="SUCCESS" if res else "FAILURE").strip()
    body = wrap_indent(_("Unattended upgrade result: %s") % result_str)
    body += "\n\n"
    if reboot_required():
        body += _(
            "Warning: A reboot is required to complete this upgrade, "
            "or a previous one.\n\n")
    if pkgs:
        if res:
            body += _("Packages that were upgraded:\n")
        else:
            body += _("Packages that attempted to upgrade:\n")
        body += " " + wrap_indent(" ".join(pkgs))
        body += "\n\n"
    if pkgs_kept_back:
        body += _("Packages with upgradable origin but kept back:\n")
        for origin, origin_pkgs in pkgs_kept_back.items():
            body += " " + origin + ":\n"
            body += "  " + wrap_indent(" ".join(origin_pkgs),
                                       subsequent_indent="  ") + "\n"
        body += "\n"
    if pkgs_removed:
        body += _("Packages that were auto-removed:\n")
        body += " " + wrap_indent(" ".join(pkgs_removed))
        body += "\n\n"
    if pkgs_kept_installed:
        body += _("Packages that were kept from being auto-removed:\n")
        body += " " + wrap_indent(" ".join(pkgs_kept_installed))
        body += "\n\n"
    if dpkg_log_content:
        body += _("Package installation log:") + "\n"
        body += dpkg_log_content
        body += "\n\n"
    body += _("Unattended-upgrades log:\n")
    if mem_log:
        body += mem_log.getvalue()
    else:
        body += "no log available"

    from_email = apt_pkg.config.find("Unattended-Upgrade::Sender", "root")

    if os.path.exists(SENDMAIL_BINARY):
        ret = _send_mail_using_sendmail(from_email, to_email, subject, body)
    elif os.path.exists(MAIL_BINARY):
        ret = _send_mail_using_mailx(from_email, to_email, subject, body)
    else:
        raise AssertionError(
            "This should never be reached as we previously validated that we "
            "either have sendmail or mailx. Maybe they've been removed in "
            "this right moment?")
    logging.debug("mail returned: %s", ret)


def do_install(cache,             # type: UnattendedUpgradesCache
               pkgs_to_upgrade,   # type: List[str]
               options,           # type: Options
               logfile_dpkg,      # type: str
               ):
    # type: (...) -> bool

    setup_apt_listchanges()

    logging.info(_("Writing dpkg log to %s"), logfile_dpkg)

    if cache.get_changes():
        cache.clear()

    pkg_install_success = False
    try:
        if options.minimal_upgrade_steps:
            # try upgrade all "pkgs" in minimal steps
            pkg_install_success = upgrade_in_minimal_steps(
                cache, pkgs_to_upgrade,
                logfile_dpkg,
                options.verbose or options.debug)
        else:
            mark_pkgs_to_upgrade(cache, pkgs_to_upgrade)
            pkg_install_success = upgrade_normal(
                cache, logfile_dpkg, options.verbose or options.debug)
    except Exception as e:
        # print unhandled exceptions here this way, while stderr is redirected
        os.write(2, ("Exception: %s\n" % e).encode('utf-8'))
        pkg_install_success = False

    return pkg_install_success


def _setup_alternative_rootdir(rootdir):
    # type: (str) -> None
    # clear system unattended-upgrade stuff
    apt_pkg.config.clear("Unattended-Upgrade")
    # read rootdir (taken from apt.Cache, but we need to run it
    # here before the cache gets initialized
    if os.path.exists(rootdir + "/etc/apt/apt.conf"):
        apt_pkg.read_config_file(apt_pkg.config,
                                 rootdir + "/etc/apt/apt.conf")
    if os.path.isdir(rootdir + "/etc/apt/apt.conf.d"):
        apt_pkg.read_config_dir(apt_pkg.config,
                                rootdir + "/etc/apt/apt.conf.d")
    logdir = os.path.join(rootdir, "var", "log", "unattended-upgrades")
    if not os.path.exists(logdir):
        os.makedirs(logdir)
    apt.apt_pkg.config.set("Unattended-Upgrade::LogDir", logdir)


def _get_logdir():
    # type: () -> str
    logdir = apt_pkg.config.find_dir(
        "Unattended-Upgrade::LogDir",
        # COMPAT only
        apt_pkg.config.find_dir("APT::UnattendedUpgrades::LogDir",
                                "/var/log/unattended-upgrades/"))
    return logdir


def _setup_logging(options):
    # type: (Options) -> Optional[StringIO]

    # ensure this is run only once
    if len(logging.root.handlers) > 0:
        return None

    # init the logging
    logdir = _get_logdir()
    logfile = os.path.join(
        logdir,
        apt_pkg.config.find(
            "Unattended-Upgrade::LogFile",
            # COMPAT only
            apt_pkg.config.find("APT::UnattendedUpgrades::LogFile",
                                "unattended-upgrades.log")))
    if not options.dry_run and not os.path.exists(logdir):
        os.makedirs(logdir)

    logging.basicConfig(level=logging.INFO,
                        format='%(asctime)s %(levelname)s %(message)s',
                        filename=logfile)
    # additional logging
    logger = logging.getLogger()
    mem_log = StringIO()
    if options.apt_debug:
        apt_pkg.config.set("Debug::pkgProblemResolver", "1")
        apt_pkg.config.set("Debug::pkgDepCache::AutoInstall", "1")
    if options.debug:
        logger.setLevel(logging.DEBUG)
        stdout_handler = logging.StreamHandler(sys.stdout)
        logger.addHandler(stdout_handler)
    elif options.verbose:
        logger.setLevel(logging.INFO)
        stdout_handler = logging.StreamHandler(sys.stdout)
        logger.addHandler(stdout_handler)
    # XXX: we always need memory logging if we use plugins
    # if apt_pkg.config.find("Unattended-Upgrade::Mail", ""):
    if True:
        mem_log_handler = logging.StreamHandler(mem_log)
        logger.addHandler(mem_log_handler)
    # Configure syslog if necessary
    syslogEnable = apt_pkg.config.find_b("Unattended-Upgrade::SyslogEnable",
                                         False)
    if syslogEnable:
        syslogFacility = apt_pkg.config.find(
            "Unattended-Upgrade::SyslogFacility",
            "daemon")
        syslogHandler = logging.handlers.SysLogHandler(
            address='/dev/log',
            facility=syslogFacility)  # type: ignore
        syslogHandler.setFormatter(
            logging.Formatter("unattended-upgrade: %(message)s"))
        known = syslogHandler.facility_names.keys()  # type: ignore
        if syslogFacility.lower() in known:
            logger.addHandler(syslogHandler)
            logging.info("Enabled logging to syslog via %s facility "
                         % syslogFacility)
        else:
            logging.warning("Syslog facility %s was not found"
                            % syslogFacility)
    return mem_log


def logged_in_users():
    # type: () -> AbstractSet[str]
    """Return a list of logged in users"""
    # the "users" command always returns a single line with:
    # "user1, user1, user2"
    users = subprocess.check_output(
        USERS, universal_newlines=True).rstrip('\n')
    return set(users.split())


def reboot_if_requested_and_needed():
    # type: () -> None
    """auto-reboot (if required and the config for this is set)"""
    if not os.path.exists(REBOOT_REQUIRED_FILE):
        return
    if not apt_pkg.config.find_b(
            "Unattended-Upgrade::Automatic-Reboot", False):
        return
    # see if we need to check for logged in users
    if not apt_pkg.config.find_b(
            "Unattended-Upgrade::Automatic-Reboot-WithUsers", True):
        users = logged_in_users()
        if users:
            msg = gettext.ngettext(
                "Found %s, but not rebooting because %s is logged in." % (
                    REBOOT_REQUIRED_FILE, users),
                "Found %s, but not rebooting because %s are logged in." % (
                    REBOOT_REQUIRED_FILE, users),
                len(users))
            logging.warning(msg)
            return
    # reboot at the specified time
    when = apt_pkg.config.find(
        "Unattended-Upgrade::Automatic-Reboot-Time", "now")
    logging.warning("Found %s, rebooting" % REBOOT_REQUIRED_FILE)
    cmd = ["/sbin/shutdown", "-r", when]
    try:
        shutdown_msg = subprocess.check_output(cmd, stderr=subprocess.STDOUT)
        if shutdown_msg.strip():
            logging.warning("Shutdown msg: %s", shutdown_msg.strip())
    except Exception as e:
        logging.error("Failed to issue shutdown: %s", e)


def write_stamp_file():
    # type: () -> None
    statedir = os.path.join(apt_pkg.config.find_dir("Dir::State"), "periodic")
    if not os.path.exists(statedir):
        os.makedirs(statedir)
    with open(os.path.join(statedir, "unattended-upgrades-stamp"), "w"):
        pass


def try_to_upgrade(pkg,               # type: apt.Package
                   pkgs_to_upgrade,   # type: List[apt.Package]
                   cache,             # type: UnattendedUpgradesCache
                   ):
    # type: (...) -> None
    try:
        try:
            # try to adjust pkg itself first, if that throws an exception it
            # can't be upgraded on its own
            cache.adjust_candidate(pkg)
            if not pkg.is_upgradable and not apt_pkg.config.find_b(
                    "Unattended-Upgrade::Allow-downgrade", False):
                return
        except NoAllowedOriginError:
            return
        cache._cached_candidate_pkgnames.add(pkg.name)
        cache.mark_upgrade_adjusted(pkg, from_user=not pkg.is_auto_installed)
        if check_changes_for_sanity(cache, pkg):
            # add to packages to upgrade
            pkgs_to_upgrade.append(pkg)
        else:
            rewind_cache(cache, pkgs_to_upgrade)
    except (SystemError, NoAllowedOriginError) as e:
        # can't upgrade
        logging.warning(
            _("package %s upgradable but fails to "
                "be marked for upgrade (%s)"), pkg.name, e)
        rewind_cache(cache, pkgs_to_upgrade)


def candidate_version_changed(pkg,               # type: apt.Package
                              ):
    return (pkg.is_installed and pkg.candidate and pkg.installed
            and pkg.candidate.version != pkg.installed.version
            and apt_pkg.config.find_b(
                'Unattended-Upgrade::Allow-downgrade', False))


def calculate_upgradable_pkgs(cache,            # type: UnattendedUpgradesCache
                              options,          # type: Options
                              ):
    # type: (...) -> List[apt.Package]
    pkgs_to_upgrade = []  # type: List[apt.Package]

    # now do the actual upgrade
    for pkg in cache:
        if options.debug and pkg.is_upgradable \
           or candidate_version_changed(pkg):
            logging.debug("Checking: %s (%s)" % (
                getattr(pkg, "candidate", pkg.name),
                getattr(pkg.candidate, "origins", [])))

        if (pkg.is_upgradable or candidate_version_changed(pkg)
           and is_pkgname_in_whitelist(pkg.name, cache.whitelist)):
            try:
                ver_in_allowed_origin(pkg, cache.allowed_origins)
            except NoAllowedOriginError:
                continue
            try_to_upgrade(pkg,
                           pkgs_to_upgrade,
                           cache)

    if cache.get_changes():
        cache.clear()

    return pkgs_to_upgrade


def get_dpkg_log_content(logfile_dpkg, install_start_time):
    # type: (str, datetime.datetime) -> str
    logging.debug("Extracting content from %s since %s" % (
        logfile_dpkg, install_start_time))
    content = []
    found_start = False
    try:
        with io.open(logfile_dpkg, encoding='utf-8', errors='replace') as fp:
            # read until we find the last "Log started: "
            for line in fp.readlines():
                # scan for the first entry we need (minimal-step mode
                # creates a new stanza for each individual install)
                if not found_start and line.startswith("Log started: "):
                    stanza_start = LoggingDateTime.from_string(
                        line[len("Log started: "):-1])
                    if stanza_start >= install_start_time:
                        found_start = True
                if found_start:
                    # skip progress indicator until #860931 is fixed in apt
                    # and dpkg
                    if re.match(
                            "^\\(Reading database \\.\\.\\. ()|([0-9]+%)$",
                            line):
                        continue
                    content.append(line)
        return "".join(content)
    except FileNotFoundError:
        return ""


def get_auto_removable(cache):
    # type: (apt.Cache) -> AbstractSet[str]
    return {pkg.name for pkg in cache
            if pkg.is_auto_removable}


def is_autoremove_valid(cache,           # type: UnattendedUpgradesCache
                        pkgname,         # type: str
                        auto_removable,  # type: AbstractSet[str]
                        ):
    # type: (...) -> bool
    changes = cache.get_changes()
    if not changes:
        # package is already removed
        return True
    pkgnames = {pkg.name for pkg in changes}
    for pkg in changes:
        if not is_pkg_change_allowed(pkg, cache.blacklist, cache.whitelist,
                                     cache.strict_whitelist):
            logging.warning(
                _("Keeping the following auto-removable package(s) because "
                  "they include %s which is set to be kept unmodified: %s"),
                pkg.name, " ".join(sorted(pkgnames)))
            return False
    if not pkgnames.issubset(auto_removable):
        if pkgname != "":
            logging.warning(
                _("Keeping auto-removable %s package(s) because it would"
                  " also remove the following packages which should "
                  "be kept in this step: %s"), pkgname,
                " ".join(sorted(pkgnames - auto_removable)))
        else:
            logging.warning(
                _("Keeping %s auto-removable package(s) because it would"
                  " also remove the following packages which should "
                  "be kept in this step: %s"), len(auto_removable),
                " ".join(sorted(pkgnames - auto_removable)))

        return False
    for packagename in pkgnames:
        if cache.running_kernel_pkgs_regexp and \
           cache.running_kernel_pkgs_regexp.match(packagename):
            logging.warning(
                _("Keeping the following auto-removable package(s) because "
                  "they include %s which package is related to the running "
                  "kernel: %s"), packagename, " ".join(sorted(pkgnames)))
            return False
    if cache.install_count > 0:
        logging.error(
            "The following packages are marked for installation or upgrade "
            "which is not allowed when performing autoremovals: %s",
            " ".join([pkg.name for pkg in changes if not pkg.marked_delete]))
        return False
    return True


def do_auto_remove(cache,             # type: UnattendedUpgradesCache
                   auto_removable,    # type: AbstractSet[str]
                   logfile_dpkg,      # type: str
                   minimal_steps,     # type: bool
                   verbose=False,     # type: bool
                   dry_run=False      # type: bool
                   ):
    # type: (...) -> Tuple[bool, List[str], List[str]]
    res = True
    if not auto_removable:
        return (res, [], [])

    pkgs_removed = []         # type: List[str]
    pkgs_kept_installed = []  # type: List[str]
    if minimal_steps:
        for pkgname in auto_removable:
            if should_stop():
                pkgs_kept_installed = list(auto_removable - set(pkgs_removed))
                return (False, pkgs_removed, pkgs_kept_installed)
            logging.debug("marking %s for removal" % pkgname)
            if pkgname in pkgs_removed:
                continue
            cache[pkgname].mark_delete()
            if not is_autoremove_valid(cache, pkgname, auto_removable):
                # this situation can occur when removing newly unused packages
                # would also remove old unused packages which are not set
                # for removal, thus getting there is not handled as an error
                pkgs_kept_installed.append(pkgname)
                cache.clear()
                continue
            if not dry_run:
                changes = cache.get_changes()
                pkgnames = {pkg.name for pkg in changes}
                res, error = cache_commit(cache, logfile_dpkg, verbose)
                if not res:
                    break
                pkgs_removed.extend(pkgnames)
            else:
                cache.clear()
    else:
        for pkgname in auto_removable:
            cache[pkgname].mark_delete()
        if is_autoremove_valid(cache, "", auto_removable):
            # do it in one step
            if not dry_run:
                res, error = cache_commit(cache, logfile_dpkg, verbose)
            else:
                cache.clear()
        else:
            cache.clear()

    if res:
        logging.info(_("Packages that were successfully auto-removed: %s"),
                     " ".join(sorted(pkgs_removed)))
        logging.info(_("Packages that are kept back: %s"),
                     " ".join(sorted(pkgs_kept_installed)))
    if not res:
        cache.clear()
        logging.error(_("Auto-removing the packages failed!"))
        logging.error(_("Error message: %s"), error)
        logging.error(_("dpkg returned an error! See %s for details"),
                      logfile_dpkg)
    return (res, pkgs_removed, pkgs_kept_installed)


def clean_downloaded_packages(fetcher):
    # type: (apt_pkg.Acquire) -> None
    archivedir = os.path.dirname(
        apt_pkg.config.find_dir("Dir::Cache::archives"))
    for item in fetcher.items:
        if os.path.dirname(os.path.abspath(item.destfile)) == archivedir:
            try:
                os.unlink(item.destfile)
            except OSError:
                pass


def is_update_day():
    # type: () -> bool
    # check if patch days are configured
    patch_days = apt_pkg.config.value_list("Unattended-Upgrade::Update-Days")
    if not patch_days:
        return True
    # validate patch days
    today = date.today()
    # abbreviated localized dayname
    if today.strftime("%a") in patch_days:
        return True
    # full localized dayname
    if today.strftime("%A") in patch_days:
        return True
    # by number (Sun: 0, Mon: 1, ...)
    if today.strftime("%w") in patch_days:
        return True
    # today is not a patch day
    logging.info(
        "Skipping update check: today is %s,%s,%s but patch days are %s",
        today.strftime("%w"), today.strftime("%a"), today.strftime("%A"),
        ", ".join(patch_days))
    return False


def update_kept_pkgs_file(kept_pkgs, kept_file):
    # type: (DefaultDict[str, List[str]], str) -> None
    if kept_pkgs:
        pkgs_all_origins = set()
        for origin_pkgs in kept_pkgs.values():
            pkgs_all_origins.update(origin_pkgs)
        try:
            with open(kept_file, "w") as kf:
                kf.write(" ".join(sorted(pkgs_all_origins)))
        except FileNotFoundError:
            logging.error(_("Could not open %s for saving list of packages "
                            "kept back." % kept_file))
    else:
        if os.path.exists(kept_file):
            os.remove(kept_file)


@contextlib.contextmanager
def try_nice(increment):
    old_priority = os.nice(0)
    try:
        try:
            # Check that we will be able to restore the priority
            os.nice(-1)
            os.nice(increment)
        except PermissionError:
            # So bad, we couldn't be nicier
            pass
        yield
    finally:
        os.nice(old_priority - os.nice(0))


def main(options, rootdir="/"):
    # type: (Options, str) -> int
    # useful for testing
    if not rootdir == "/":
        _setup_alternative_rootdir(rootdir)

    # see debian #776752
    install_start_time = datetime.datetime.now().replace(microsecond=0)

    # setup logging
    mem_log = _setup_logging(options)
    # get log
    logfile_dpkg = os.path.join(_get_logdir(), 'unattended-upgrades-dpkg.log')
    if not os.path.exists(logfile_dpkg):
        with open(logfile_dpkg, 'w'):
            pass

    # lock for the shutdown check
    shutdown_lock = apt_pkg.get_lock(LOCK_FILE)
    if shutdown_lock < 0:
        logging.error("Lock file is already taken, exiting")
        return 1

    plugin_manager = PluginManager()

    try:
        res = run(options, rootdir, mem_log, logfile_dpkg,
                  install_start_time)
        logging.debug("upgrade result: %s %s" % (res.success, res.result_str))

        if res.success and res.result_str:
            # complete, successful run
            update_kept_pkgs_file(res.pkgs_kept_back,
                                  os.path.join(rootdir, KEPT_PACKAGES_FILE))

        if res.result_str and not options.dry_run:
            # there is some meaningful result which is worth an email
            log_content = get_dpkg_log_content(logfile_dpkg,
                                               install_start_time)
            send_summary_mail(res.pkgs, res.success, res.result_str,
                              res.pkgs_kept_back, res.pkgs_removed,
                              res.pkgs_kept_installed, mem_log,
                              log_content)
            # report results to any plugin
            plugin_manager.postrun(res, mem_log, log_content)

        if res.update_stamp:
            # write timestamp file
            write_stamp_file()
            if not options.dry_run:
                # check if the user wants a reboot
                reboot_if_requested_and_needed()
        os.close(shutdown_lock)
        if res.success:
            return 0
        else:
            return 1

    except Exception as e:
        logger = logging.getLogger()
        logger.exception(_("An error occurred: %s"), e)
        log_content = get_dpkg_log_content(logfile_dpkg,
                                           install_start_time)
        if not options.dry_run:
            send_summary_mail(["<unknown>"], False, _("An error occurred"),
                              None, [], [], mem_log, log_content)
        # Re-raise exceptions for apport
        raise


def mark_pkgs_to_upgrade(cache, pkgs_to_upgrade):
    # type (apt.Cache, List[str]) -> None
    for pkg_name in pkgs_to_upgrade:
        pkg = cache[pkg_name]
        if pkg.is_upgradable \
           or (pkg.is_installed
               and pkg.candidate.version != pkg.installed.version) \
            and apt_pkg.config.find_b("Unattended-Upgrade::Allow-downgrade",
                                      False):
            cache.mark_upgrade_adjusted(pkg,
                                        from_user=not pkg.is_auto_installed)
        elif not pkg.is_installed:
            cache.mark_install_adjusted(pkg, from_user=False)


def run(options,             # type: Options
        rootdir,             # type: str
        mem_log,             # type: Optional[StringIO]
        logfile_dpkg,        # type: str
        install_start_time,  # type: datetime.datetime
        ):
    # type: (...) -> UnattendedUpgradesResult

    # check if today is a patch day
    if not is_update_day():
        return UnattendedUpgradesResult(True)

    # check if u-u should be stopped already
    if should_stop():
        return UnattendedUpgradesResult(False)

    # check to see if want to auto-upgrade the devel release
    if apt_pkg.config.find("Unattended-Upgrade::DevRelease") == "auto":
        try:
            if DISTRO_ID.lower() == 'ubuntu':
                devel = (distro_info.UbuntuDistroInfo() .
                         devel(result="object"))
            elif DISTRO_ID.lower() == 'debian':
                devel = (distro_info.DebianDistroInfo() .
                         devel(result="object"))
            else:
                devel = (distro_info.DistroInfo(DISTRO_ID) .
                         devel(result="object"))
        except Exception as e:
            logging.warning("Could not figure out development release: %s" % e)
        else:
            if ((isinstance(devel, distro_info.DistroRelease)
                 and devel.series == DISTRO_CODENAME
                 and devel.release is not None
                 and devel.release - date.today() > DEVEL_UNTIL_RELEASE)):
                syslog.syslog((_("Not running on this development "
                                 "release before %s") %
                              (devel.release - DEVEL_UNTIL_RELEASE
                               - datetime.timedelta(days=1))))
                logging.warning(_("Not running on this development "
                                  "release before %s") %
                                (devel.release - DEVEL_UNTIL_RELEASE
                                 - datetime.timedelta(days=1)))
                return UnattendedUpgradesResult(True)

            logging.debug("Running on the development release")
    elif "(development branch)" in DISTRO_DESC and not\
            apt_pkg.config.find_b("Unattended-Upgrade::DevRelease", True):
        syslog.syslog(_("Not running on the development release."))
        logging.info(_("Not running on the development release."))
        return UnattendedUpgradesResult(True)

    logging.info(_("Starting unattended upgrades script"))

    # check and get lock
    try:
        apt_pkg.pkgsystem_lock()
    except SystemError:
        logging.error(_("Lock could not be acquired (another package "
                        "manager running?)"))
        print(_("Cache lock can not be acquired, exiting"))
        return UnattendedUpgradesResult(
            False, _("Lock could not be acquired"))

    # check if the journal is dirty and if so, take emergceny action
    # the alternative is to leave the system potentially unsecure until
    # the user comes in and fixes
    if is_dpkg_journal_dirty() and \
       apt_pkg.config.find_b("Unattended-Upgrade::AutoFixInterruptedDpkg",
                             True):
        logging.warning(
            _("Unclean dpkg state detected, trying to correct"))
        print(_("Unclean dpkg state detected, trying to correct"))
        env = copy.copy(os.environ)
        env["DPKG_FRONTEND_LOCKED"] = "1"
        try:
            with Unlocked():
                output = subprocess.check_output(
                    ["dpkg", "--force-confold", "--configure", "-a"],
                    env=env,
                    universal_newlines=True)
        except subprocess.CalledProcessError as e:
            output = e.output
        logging.warning(_("dpkg --configure -a output:\n%s"), output)

    # get a cache
    try:
        cache = UnattendedUpgradesCache(rootdir=rootdir)
    except SystemError as error:
        print(_("Apt returned an error, exiting"))
        print(_("error message: %s") % error)
        logging.error(_("Apt returned an error, exiting"))
        logging.error(_("error message: %s"), error)
        return UnattendedUpgradesResult(
            False, _("Apt returned an error, exiting"))

    if cache._depcache.broken_count > 0:
        print(_("Cache has broken packages, exiting"))
        logging.error(_("Cache has broken packages, exiting"))
        return UnattendedUpgradesResult(
            False, _("Cache has broken packages, exiting"))

    with try_nice(20):
        auto_removable = get_auto_removable(cache)

        # find out about the packages that are upgradable (in an
        # allowed_origin)
        pkgs_to_upgrade = calculate_upgradable_pkgs(cache, options)
        pkgs_to_upgrade.sort(key=lambda p: p.name)
        pkgs = [pkg.name for pkg in pkgs_to_upgrade]
        logging.debug("pkgs that look like they should be upgraded: %s"
                      % "\n".join(pkgs))

    # download what looks good
    mark_pkgs_to_upgrade(cache, pkgs)

    if options.debug:
        fetcher = apt_pkg.Acquire(apt.progress.text.AcquireProgress())
    else:
        fetcher = apt_pkg.Acquire()
    list = apt_pkg.SourceList()
    list.read_main_list()
    recs = cache._records
    pm = apt_pkg.PackageManager(cache._depcache)
    # don't start downloading during shutdown
    # TODO: download files one by one and check for stop request after each of
    # them
    if should_stop():
        return UnattendedUpgradesResult(False, _("Upgrade was interrupted"))
    try:
        pm.get_archives(fetcher, list, recs)
    except SystemError as e:
        logging.error(_("GetArchives() failed: %s"), e)
    try:
        res = fetcher.run()
        logging.debug("fetch.run() result: %s", res)
    except SystemError as e:
        logging.error("fetch.run() result: %s", e)

    if options.download_only:
        return UnattendedUpgradesResult(True)

    if cache.get_changes():
        cache.clear()

    pkg_conffile_prompt = False
    if dpkg_conffile_prompt():
        # now check the downloaded debs for conffile conflicts and build
        # a blacklist
        conffile_blacklist = []  # type: List[str]
        for item in fetcher.items:
            logging.debug("%s" % item)
            if item.status == item.STAT_ERROR:
                print(_("An error occurred: %s") % item.error_text)
                logging.error(_("An error occurred: %s"), item.error_text)
            if not item.complete:
                print(_("The URI %s failed to download, aborting") %
                      item.desc_uri)
                logging.error(_("The URI %s failed to download, aborting"),
                              item.desc_uri)
                return UnattendedUpgradesResult(
                    False, (_("The URI %s failed to download, aborting") %
                            item.desc_uri))
            if not os.path.exists(item.destfile):
                print(_("Download finished, but file %s not there?!?") %
                      item.destfile)
                logging.error("Download finished, but file %s not "
                              "there?!?", item.destfile)
                return UnattendedUpgradesResult(
                    False, (_("Download finished, but file %s not there?!?") %
                            item.destfile))
            if not item.is_trusted and not apt_pkg.config.find_b(
                    "APT::Get::AllowUnauthenticated", False):
                logging.debug("%s is blacklisted because it is not trusted")
                pkg_name = pkgname_from_deb(item.destfile)
                if not is_pkgname_in_blacklist(pkg_name, cache.blacklist):
                    conffile_blacklist.append("%s$" % re.escape(pkg_name))
            if not is_deb(item.destfile):
                logging.debug("%s is not a .deb file" % item)
                continue
            if conffile_prompt(item.destfile):
                # skip package (means to re-run the whole marking again
                # and making sure that the package will not be pulled in by
                # some other package again!)
                #
                # print to stdout to ensure that this message is part of
                # the cron mail (only if no summary mail is requested)
                email = apt_pkg.config.find("Unattended-Upgrade::Mail", "")
                if not email:
                    print(_("Package %s has conffile prompt and needs "
                            "to be upgraded manually") %
                          pkgname_from_deb(item.destfile))
                # log to the logfile
                logging.warning(_("Package %s has conffile prompt and "
                                  "needs to be upgraded manually"),
                                pkgname_from_deb(item.destfile))
                pkg_name = pkgname_from_deb(item.destfile)
                if not is_pkgname_in_blacklist(pkg_name, cache.blacklist):
                    conffile_blacklist.append("%s$" % re.escape(pkg_name))
                pkg_conffile_prompt = True

        # redo the selection about the packages to upgrade based on the new
        # blacklist
        logging.debug("Packages blacklist due to conffile prompts: %s"
                      % conffile_blacklist)
        # find out about the packages that are upgradable (in a allowed_origin)
        if len(conffile_blacklist) > 0:
            for regex in conffile_blacklist:
                cache.blacklist.append(regex)
            cache.apply_pinning(cache.pinning_from_regex_list(
                conffile_blacklist, NEVER_PIN))  # type: ignore
            old_pkgs_to_upgrade = pkgs_to_upgrade[:]
            pkgs_to_upgrade = []
            for pkg in old_pkgs_to_upgrade:
                logging.debug("Checking the black and whitelist: %s" %
                              (pkg.name))
                cache.mark_upgrade_adjusted(
                    pkg, from_user=not pkg.is_auto_installed)
                if check_changes_for_sanity(cache):
                    pkgs_to_upgrade.append(pkg)
                else:
                    logging.info(_("package %s not upgraded"), pkg.name)
                    cache.clear()
                    for pkg2 in pkgs_to_upgrade:
                        cache.call_adjusted(
                            apt.package.Package.mark_upgrade, pkg2,
                            from_user=not pkg2.is_auto_installed)
            if cache.get_changes():
                cache.clear()

    else:
        logging.debug("dpkg is configured not to cause conffile prompts")

    # auto-removals
    kernel_pkgs_remove_success = True  # type: bool
    kernel_pkgs_removed = []           # type: List[str]
    kernel_pkgs_kept_installed = []    # type: List[str]
    if (auto_removable and apt_pkg.config.find_b(
            "Unattended-Upgrade::Remove-Unused-Kernel-Packages", True)):
        # remove unused kernels before installing new ones because the newly
        # installed ones may fill up /boot and break the system right before
        # removing old ones could take place
        #
        # this step may also remove _auto-removable_ reverse dependencies
        # of kernel packages
        auto_removable_kernel_pkgs = {
            p for p in auto_removable
            if (cache.versioned_kernel_pkgs_regexp
                and cache.versioned_kernel_pkgs_regexp.match(p)
                and not cache.running_kernel_pkgs_regexp.match(p))}
        if auto_removable_kernel_pkgs:
            logging.info(_("Removing unused kernel packages: %s"),
                         " ".join(auto_removable_kernel_pkgs))
            (kernel_pkgs_remove_success,
             kernel_pkgs_removed,
             kernel_pkgs_kept_installed) = do_auto_remove(
                cache, auto_removable_kernel_pkgs, logfile_dpkg,
                options.minimal_upgrade_steps,
                options.verbose or options.debug, options.dry_run)
            auto_removable = get_auto_removable(cache)

    previous_autoremovals = auto_removable
    if apt_pkg.config.find_b(
            "Unattended-Upgrade::Remove-Unused-Dependencies", False):
        pending_autoremovals = previous_autoremovals
    else:
        pending_autoremovals = set()

    # exit if there is nothing to do and nothing to report
    if (len(pending_autoremovals) == 0
            and len(pkgs_to_upgrade) == 0):
        logging.info(_("No packages found that can be upgraded unattended "
                       "and no pending auto-removals"))

        pkgs_kept_back = cache.find_kept_packages(options.dry_run)
        return UnattendedUpgradesResult(
            kernel_pkgs_remove_success,
            _("No packages found that can be upgraded unattended and no "
              "pending auto-removals"),
            pkgs_removed=kernel_pkgs_removed,
            pkgs_kept_back=pkgs_kept_back,
            pkgs_kept_installed=kernel_pkgs_kept_installed,
            update_stamp=True)

    # check if its configured for install on shutdown, if so, the
    # environment UNATTENDED_UPGRADES_FORCE_INSTALL_ON_SHUTDOWN will
    # be set by the unatteded-upgrades-shutdown script
    if ("UNATTENDED_UPGRADES_FORCE_INSTALL_ON_SHUTDOWN" not in os.environ
        and apt_pkg.config.find_b(
            "Unattended-Upgrade::InstallOnShutdown", False)):
        logger = logging.getLogger()
        logger.debug("Configured to install on shutdown, so exiting now")
        return UnattendedUpgradesResult(True)

    # check if we are in dry-run mode
    if options.dry_run:
        logging.info("Option --dry-run given, *not* performing real actions")
        apt_pkg.config.set("Debug::pkgDPkgPM", "1")

    # do the install based on the new list of pkgs
    pkgs = [pkg.name for pkg in pkgs_to_upgrade]
    logging.info(_("Packages that will be upgraded: %s"), " ".join(pkgs))

    # only perform install step if we actually have packages to install
    pkg_install_success = True
    if len(pkgs_to_upgrade) > 0:
        # do install
        pkg_install_success = do_install(cache,
                                         pkgs,
                                         options,
                                         logfile_dpkg)
    # Was the overall run succesful: only if everything installed
    # fine and nothing was held back because of a conffile prompt.
    logging.debug("kernel_pkgs_remove_success: %s" % kernel_pkgs_remove_success)
    logging.debug("pkg_install_success: %s", pkg_install_success)
    logging.debug("pkg_conffile_prompt: %s" % pkg_conffile_prompt)
    successful_run = (kernel_pkgs_remove_success and pkg_install_success
                      and not pkg_conffile_prompt)

    # now check if any auto-removing needs to be done
    if cache._depcache.broken_count > 0:
        print(_("Cache has broken packages, exiting"))
        logging.error(_("Cache has broken packages, exiting"))
        return UnattendedUpgradesResult(
            False, _("Cache has broken packages, exiting"), pkgs=pkgs)

    # make sure we start autoremovals with a clear cache
    if cache.get_changes():
        cache.clear()

    # the user wants *all* auto-removals to be removed
    # (unless u-u got signalled to stop gracefully quickly)
    pkgs_removed = []         # type: List[str]
    pkgs_kept_installed = []  # type: List[str]
    if ((apt_pkg.config.find_b(
            "Unattended-Upgrade::Remove-Unused-Dependencies", False)
         and not SIGNAL_STOP_REQUEST)):
        auto_removals = get_auto_removable(cache)
        (pkg_remove_success,
         pkgs_removed,
         pkgs_kept_installed) = do_auto_remove(
            cache, auto_removals, logfile_dpkg, options.minimal_upgrade_steps,
            options.verbose or options.debug,
            options.dry_run)
        logging.debug("pkg_remove_success: %s" % pkg_remove_success)
        successful_run = successful_run and pkg_remove_success
    # the user wants *only new* auto-removals to be removed
    elif apt_pkg.config.find_b(
            "Unattended-Upgrade::Remove-New-Unused-Dependencies", True):
        # calculate the new auto-removals
        new_pending_autoremovals = get_auto_removable(cache)
        auto_removals = new_pending_autoremovals - previous_autoremovals
        (pkg_remove_success,
         pkgs_removed,
         pkgs_kept_installed) = do_auto_remove(
            cache, auto_removals, logfile_dpkg, options.minimal_upgrade_steps,
            options.verbose or options.debug,
            options.dry_run)
        logging.debug("pkg_remove_success: %s" % pkg_remove_success)
        successful_run = successful_run and pkg_remove_success

    logging.debug("InstCount=%i DelCount=%i BrokenCount=%i"
                  % (cache._depcache.inst_count,
                     cache._depcache.del_count,
                     cache._depcache.broken_count))

    # clean after success install (if needed)
    keep_key = "Unattended-Upgrade::Keep-Debs-After-Install"
    if (not apt_pkg.config.find_b(keep_key, False)
            and not options.dry_run
            and pkg_install_success):
        clean_downloaded_packages(fetcher)

    pkgs_kept_back = cache.find_kept_packages(options.dry_run)
    return UnattendedUpgradesResult(
        successful_run, _("All upgrades installed"), pkgs,
        pkgs_kept_back,
        kernel_pkgs_removed + pkgs_removed,
        kernel_pkgs_kept_installed + pkgs_kept_installed,
        update_stamp=True)


class Options:
    def __init__(self):
        self.download_only = False
        self.dry_run = False
        self.debug = False
        self.apt_debug = False
        self.verbose = False
        self.minimal_upgrade_steps = False


if __name__ == "__main__":
    localesApp = "unattended-upgrades"
    localesDir = "/usr/share/locale"
    gettext.bindtextdomain(localesApp, localesDir)
    gettext.textdomain(localesApp)

    # set debconf to NON_INTERACTIVE
    os.environ["DEBIAN_FRONTEND"] = "noninteractive"

    # this ensures the commandline is logged in /var/log/apt/history.log
    apt_pkg.config.set("Commandline::AsString", " ".join(sys.argv))

    # COMPAT with the mispelling
    minimal_steps_default = (
        apt_pkg.config.find_b("Unattended-Upgrades::MinimalSteps", True)
        and apt_pkg.config.find_b("Unattended-Upgrade::MinimalSteps", True))

    # init the options
    parser = OptionParser()
    parser.add_option("-d", "--debug",
                      action="store_true",
                      default=apt_pkg.config.find_b(
                          "Unattended-Upgrade::Debug", False),
                      help=_("print debug messages"))
    parser.add_option("", "--apt-debug",
                      action="store_true", default=False,
                      help=_("make apt/libapt print verbose debug messages"))
    parser.add_option("-v", "--verbose",
                      action="store_true",
                      default=apt_pkg.config.find_b(
                          "Unattended-Upgrade::Verbose", False),
                      help=_("print info messages"))
    parser.add_option("", "--dry-run",
                      action="store_true", default=False,
                      help=_("Simulation, download but do not install"))
    parser.add_option("", "--download-only",
                      action="store_true", default=False,
                      help=_("Only download, do not even try to install."))
    parser.add_option("", "--minimal-upgrade-steps",
                      action="store_true", default=minimal_steps_default,
                      help=_("Upgrade in minimal steps (and allow "
                             "interrupting with SIGTERM) (default)"))
    parser.add_option("", "--no-minimal-upgrade-steps",
                      action="store_false", default=minimal_steps_default,
                      dest="minimal_upgrade_steps",
                      help=_("Upgrade all packages together instead of in "
                             "smaller sets"))
    parser.add_option("", "--minimal_upgrade_steps",
                      action="store_true",
                      help=SUPPRESS_HELP,
                      default=minimal_steps_default)
    options = cast(Options, (parser.parse_args())[0])

    if os.getuid() != 0:
        print(_("You need to be root to run this application"))
        sys.exit(1)

    # ensure that we are not killed when the terminal goes away e.g. on
    # shutdown
    signal.signal(signal.SIGHUP, signal.SIG_IGN)

    # setup signal handler for graceful stopping
    signal.signal(signal.SIGTERM, signal_handler)

    # write pid to let other processes find this one
    pidf = os.path.join(apt_pkg.config.find_dir("Dir"),
                        "var", "run", "unattended-upgrades.pid")
    # clean up pid file on exit
    with open(pidf, "w") as fp:
        fp.write("%s" % os.getpid())
    atexit.register(os.remove, pidf)

    # run the main code
    sys.exit(main(options))