unattended-upgrade

#!/usr/bin/python3
# Copyright (c) 2005-2015 Canonical Ltd
#
# AUTHOR:
# Michael Vogt <mvo@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 copy
import datetime
import errno
import email.charset
import fcntl
import fnmatch
import gettext
import grp
import io
import locale
import logging
import logging.handlers
import re
import os
import select
import signal
import string
import subprocess
import sys

try:
    from typing import AbstractSet, Dict, Iterable, List, Tuple
    AbstractSet  # pyflakes
    Dict  # pyflakes
    Iterable  # pyflakes
    List  # pyflakes
    Tuple  # pyflakes
except ImportError:
    pass

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,
)
import apt
import apt_inst
import apt_pkg


# the reboot required flag file used by packages
REBOOT_REQUIRED_FILE = "/var/run/reboot-required"
MAIL_BINARY = "/usr/bin/mail"
SENDMAIL_BINARY = "/usr/sbin/sendmail"
USERS = "/usr/bin/users"
# no py3 lsb_release in debian :/
DISTRO_CODENAME = subprocess.check_output(
    ["lsb_release", "-c", "-s"], universal_newlines=True).strip()  # type: str
DISTRO_ID = subprocess.check_output(
    ["lsb_release", "-i", "-s"], universal_newlines=True).strip()  # type: str

# 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


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 UnattendedUpgradesCache(apt.Cache):

    def __init__(self, rootdir, allowed_origins):
        # type: (str, List[str]) -> None
        self._cached_candidate_pkgnames = None  # type: AbstractSet[str]
        self.allowed_origins = allowed_origins
        apt.Cache.__init__(self, rootdir=rootdir)

        # generate versioned_kernel_pkgs_regexp for later use
        apt_versioned_kernel_pkgs = apt_pkg.config.value_list(
            "APT::VersionedKernelPackages")
        if apt_versioned_kernel_pkgs:
            self.versioned_kernel_pkgs_regexp = re.compile("(" + "|".join(
                ["^" + p for p in apt_versioned_kernel_pkgs]) + ")")
            logging.debug("Using %s regexp to find kernel packages",
                          self.versioned_kernel_pkgs_regexp.pattern)
            running_kernel_version = subprocess.check_output(
                ["uname", "-r"], universal_newlines=True).rstrip()
            self.running_kernel_pkgs_regexp = re.compile("(" + "|".join(
                [("^" + p + ".*" + running_kernel_version)
                 if not p.startswith(".*") else (running_kernel_version + p)
                 for p in apt_versioned_kernel_pkgs]) + ")")
            logging.debug("Using %s regexp to find running kernel packages",
                          self.running_kernel_pkgs_regexp.pattern)
        else:
            logging.debug("APT::VersionedKernelPackages is not set")
            self.versioned_kernel_pkgs_regexp = None
            self.running_kernel_pkgs_regexp = None

        # ensure we update the candidate versions
        self.adjust_candidates()

    def open(self, progress=None):
        # type: (apt.progress.base.Progress) -> None
        apt.Cache.open(self, progress)
        # ensure we update the candidate versions
        self.adjust_candidates()

    def clear(self):
        # type: () -> None
        apt.Cache.clear(self)
        # ensure we update the candidate versions
        self.adjust_candidates()

    def adjust_candidates(self):
        for pkgname, candidate in self._get_candidates_to_adjust():
            self[pkgname].candidate = candidate

    def _get_candidates_to_adjust(self):
        # type: () -> Dict[str, apt.Version]
        """ Get candidate versions needed to be adjusted to match highest
            allowed origin

            This lets adjusting the origin even if the candidate has a higher
            version. 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
        """
        candidates = {}
        if self._cached_candidate_pkgnames is None:
            pkg_iter = iter(self.keys())
        else:
            pkg_iter = iter(
                [self[name] for name in self._cached_candidate_pkgnames])
        for pkgname in pkg_iter:
            pkg = self[pkgname]
            # important! this avoids downgrades below
            if pkg.is_installed and not pkg.is_upgradable:
                continue
            # check if the candidate is already pointing to a allowed
            # origin and if so, do not mess with it
            if is_allowed_origin(pkg.candidate, self.allowed_origins):
                continue
            # check if we have a version in a allowed origin that is
            # not the candidate
            new_cand = None
            for ver in pkg.versions:
                # ignore versions that the user marked with priority < 100
                # (and ensure we have a python-apt that supports this)
                if (hasattr(ver, "policy_priority") and
                        ver.policy_priority < 100):
                    logging.debug("ignoring ver %s with priority < 0" % ver)
                    continue
                if is_allowed_origin(ver, self.allowed_origins):
                    # leave as soon as we have the highest new candidate
                    new_cand = ver
                    break
            if new_cand and new_cand != pkg.candidate:
                logging.debug("adjusting candidate version: %s" % new_cand)
                candidates[pkg.name] = new_cand
        self._cached_candidate_pkgnames = set(
            [name for name in candidates.keys()])
        return candidates


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: 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 as e:
                    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 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()
        except Exception:
            pass

    def __exit__(self, exc_type, exc_value, exc_tb):
        # type: (object, object, object) -> None
        try:
            apt_pkg.pkgsystem_lock()
        except Exception:
            pass


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


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 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, apt.package.Origin) -> 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 cache_commit(cache,           # type: apt.Cache
                 logfile_dpkg,    # type: str
                 verbose,         # type: bool
                 iprogress=None,  # type: apt.progress.base.InstallProgress
                 ):
    # type: (...) -> Tuple[bool, Exception]
    """Commit the changes from the given cache to the system"""
    # set debconf to NON_INTERACTIVE, redirect output
    os.putenv("DEBIAN_FRONTEND", "noninteractive")

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

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

    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 use_minimal_steps(options):
    # type: (Options) -> bool
    return (options.minimal_upgrade_steps or
            # COMPAT with the mispelling
            (apt_pkg.config.find_b("Unattended-Upgrades::MinimalSteps",
                                   True) and
             apt_pkg.config.find_b("Unattended-Upgrade::MinimalSteps",
                                   True)))


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

    # double check any changes we do
    allowed_origins = get_allowed_origins()

    # pre-calculate set sizes to process sets which are expected to be smaller
    # earlier
    upgrade_set_sizes = {}
    # calculate upgrade sets
    for pkgname in pkgs_to_upgrade:
        cache.clear()
        pkg = cache[pkgname]
        if pkg.is_upgradable:
            pkg.mark_upgrade()
        elif not pkg.is_installed:
            pkg.mark_install()
        else:
            continue
        upgrade_set_sizes[pkgname] = cache.install_count
    cache.clear()

    # to upgrade contains the package names
    to_upgrade = set(pkgs_to_upgrade)
    for pkgname in sorted(upgrade_set_sizes, key=upgrade_set_sizes.get):
        # 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 SIGNAL_STOP_REQUEST:
            logging.warning("SIGNAL received, stopping")
            return False
        pkg = cache[pkgname]
        if pkg.is_upgradable:
            pkg.mark_upgrade(from_user=not pkg.is_auto_installed)
        elif not pkg.is_installed:
            pkg.mark_install(from_user=False)
        else:
            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, allowed_origins, blacklist,
                                        whitelist):
            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:
            percent = ((len(pkgs_to_upgrade) - len(to_upgrade)) /
                       float(len(pkgs_to_upgrade)) * 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 True


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


def is_pkgname_in_blacklist(pkgname, blacklist, pkgs_kept_back):
    # type: (str, List[str], List[str]) -> bool
    for blacklist_regexp in blacklist:
        if re.match(blacklist_regexp, pkgname):
            logging.debug("skipping blacklisted package %s" % pkgname)
            pkgs_kept_back.append(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):
    # type: (apt.Package, List[str], List[str]) -> 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
    strict_whitelist = apt_pkg.config.find_b(
        "Unattended-Upgrade::Package-Whitelist-Strict", False)
    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 check_changes_for_sanity(cache, allowed_origins, blacklist, whitelist,
                             desired_pkg=None):
    # type: (apt.Cache, List[str], List[str], List[str], apt.Package) -> bool
    if cache._depcache.broken_count != 0:
        return False
    # If there are no packages to be installed they were kept back
    if cache.install_count == 0:
        return False
    changes = cache.get_changes()
    for pkg in changes:
        if pkg.marked_delete:
            logging.debug("pkg %s now marked delete" % pkg.name)
            return False
        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]):
                logging.debug("pkg %s is untrusted" % pkg.name)
                return False
            if not is_allowed_origin(pkg.candidate, allowed_origins):
                logging.debug("pkg %s not in allowed origin" % pkg.name)
                return False
            if not is_pkg_change_allowed(pkg, blacklist, whitelist):
                return False
            # 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"):
                logging.debug("pkg %s requires app-restart, not safe to "
                              "upgrade unattended")
                return False
    # check that the package we want to upgrade is in the change set
    if desired_pkg and desired_pkg not in changes:
        return False
    return True


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.stdout.close()
        p.wait()
    return pkg_md5sum


# 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 = ""
    try:
        deb = apt_inst.DebFile(destFile)
        pkg_conffiles = deb.control.extractdata("conffiles").strip().decode(
            "utf-8")
    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)
        sys.exit(1)
    except LookupError as e:
        logging.debug("No conffiles in deb %s (%s)" % (destFile, e))

    # 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]
        if len(li) > 2:
            obs = li[2]
        else:
            obs = None
        # 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
        if not pkg_conffiles or conf_file not in pkg_conffiles.split("\n"):
            logging.debug("%s not in package conffiles %s" % (
                conf_file, pkg_conffiles))
            continue
        # record for later
        dpkg_status_conffiles[conf_file] = md5

        # 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
        if os.path.isdir(prefix + conf_file):
            continue

        # 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 = ""
        if os.path.exists(prefix + conf_file):
            with open(prefix + conf_file, 'rb') as fb:
                current_md5 = apt_pkg.md5sum(fb)
        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, 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
        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.split("\n"):
            if (conf_file not in dpkg_status_conffiles and
                    os.path.exists(prefix + conf_file)):
                logging.debug("found conffile %s in new pkg but on dpkg "
                              "status" % conf_file)
                pkg_md5sum = get_md5sum_for_file_in_deb(destFile, conf_file)
                with open(prefix + conf_file, 'rb') as fp:
                    if pkg_md5sum != apt_pkg.md5sum(fp):
                        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: (apt.Cache, List[apt.Package]) -> None
    """ set the cache back to the state with packages_to_upgrade """
    cache.clear()
    for pkg2 in pkgs_to_upgrade:
        pkg2.mark_install(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 os.uname()[1]


# *sigh* textwrap is nice, but it breaks "linux-image" into two
# seperate lines
def wrap(t, width=70, subsequent_indent=""):
    # type: (str, int, str) -> str
    out = ""
    for s in t.split():
        if (len(out) - out.rfind("\n")) + len(s) > width:
            out += "\n" + subsequent_indent
        out += s + " "
    return out


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)
    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)
    sendmail.stdin.write(msg.as_string())
    sendmail.stdin.close()
    ret = sendmail.wait()
    return ret


def send_summary_mail(pkgs, res, pkgs_kept_back, pkgs_removed,
                      pkgs_kept_installed, mem_log, dpkg_log_content):
    # type: (str, bool, List[str], List[str], List[str], StringIO, str) -> 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
    # if the operation was successful and the user has requested to get
    # mails on on errors, just exit here
    if (res and apt_pkg.config.find_b(
            "Unattended-Upgrade::MailOnlyOnError", False)):
        return
    # Check if reboot-required flag is present
    reboot_flag_str = _(
        "[reboot required]") if os.path.isfile(REBOOT_REQUIRED_FILE) 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=res).strip()
    body = _("Unattended upgrade returned: %s\n\n") % res
    if os.path.isfile(REBOOT_REQUIRED_FILE):
        body += _(
            "Warning: A reboot is required to complete this upgrade.\n\n")
    if res:
        body += _("Packages that were upgraded:\n")
    else:
        body += _("Packages that attempted to upgrade:\n")
    body += " " + wrap(pkgs, 70, " ")
    body += "\n"
    if pkgs_kept_back:
        body += _("Packages with upgradable origin but kept back:\n")
        body += " " + wrap(" ".join(pkgs_kept_back), 70, " ")
        body += "\n"
    body += "\n"
    if pkgs_removed:
        body += _("Packages that were auto-removed:\n")
        body += " " + wrap(" ".join(pkgs_removed), 70, " ")
        body += "\n"
    body += "\n"
    if pkgs_kept_installed:
        body += _("Packages that were kept from being auto-removed:\n")
        body += " " + wrap(" ".join(pkgs_kept_installed), 70, " ")
        body += "\n"
    body += "\n"
    if dpkg_log_content:
        body += _("Package installation log:") + "\n"
        body += dpkg_log_content
        body += "\n\n"
    body += _("Unattended-upgrades log:\n")
    body += mem_log.getvalue()

    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, if we are here we either "
            "have sendmail or mailx. Please report this as a bug.")
    logging.debug("mail returned: %s", ret)


def do_install(cache,             # type: apt.Cache
               pkgs_to_upgrade,   # type: List[apt.Package]
               blacklisted_pkgs,  # type: List[str]
               whitelisted_pkgs,  # type: List[str]
               options,           # type: Options
               logfile_dpkg,      # type: str
               ):
    # type: (...) -> bool
    # set debconf to NON_INTERACTIVE, redirect output
    os.putenv("DEBIAN_FRONTEND", "noninteractive")
    setup_apt_listchanges()

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

    marked_delete = [pkg for pkg in cache.get_changes() if pkg.marked_delete]
    if marked_delete:
        raise AssertionError(
            "Internal error. The following packages are marked for "
            "removal:%s" % "".join([pkg.name for pkg in marked_delete]))

    pkg_install_success = False
    try:
        if use_minimal_steps(options):
            # try upgrade all "pkgs" in minimal steps
            pkg_install_success = upgrade_in_minimal_steps(
                cache, [pkg.name for pkg in pkgs_to_upgrade],
                blacklisted_pkgs, whitelisted_pkgs, logfile_dpkg,
                options.verbose or options.debug)
        else:
            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) -> 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)
    if apt_pkg.config.find("Unattended-Upgrade::Mail", ""):
        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)
        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 get_blacklisted_pkgs():
    # type: () -> List[str]
    return apt_pkg.config.value_list("Unattended-Upgrade::Package-Blacklist")


def get_whitelisted_pkgs():
    # type: () -> List[str]
    return apt_pkg.config.value_list("Unattended-Upgrade::Package-Whitelist")


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)
    subprocess.call(["/sbin/shutdown", "-r", when])


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]
                   pkgs_kept_back,    # type: List[str]
                   cache,             # type: apt.Cache
                   allowed_origins,   # type: List[str]
                   blacklisted_pkgs,  # type: List[str]
                   whitelisted_pkgs,  # type: List[str]
                   ):
    # type: (...) -> None
    try:
        pkg.mark_upgrade(from_user=not pkg.is_auto_installed)
        if check_changes_for_sanity(cache, allowed_origins,
                                    blacklisted_pkgs, whitelisted_pkgs,
                                    pkg):
            # add to packages to upgrade
            pkgs_to_upgrade.append(pkg)
            # re-eval pkgs_kept_back as the resolver may fail to
            # directly upgrade a pkg, but that may work during
            # a subsequent operation, see debian bug #639840
            for pkgname in pkgs_kept_back:
                if (cache[pkgname].marked_install or
                        cache[pkgname].marked_upgrade):
                    pkgs_kept_back.remove(pkgname)
                    pkgs_to_upgrade.append(cache[pkgname])
        else:
            logging.debug("sanity check failed")
            rewind_cache(cache, pkgs_to_upgrade)
            pkgs_kept_back.append(pkg.name)
    except SystemError 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)
        pkgs_kept_back.append(pkg.name)


def calculate_upgradable_pkgs(cache,             # type: apt.Cache
                              options,           # type: Options
                              allowed_origins,   # type: List[str]
                              blacklisted_pkgs,  # type: List[str]
                              whitelisted_pkgs,  # type: List[str]
                              ):
    # type: (...) -> Tuple[List[apt.Package], List[str]]
    pkgs_to_upgrade = []  # type: List[apt.Package]
    pkgs_kept_back = []   # type: List[str]

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

        if (pkg.is_upgradable and
                not is_pkgname_in_blacklist(pkg.name, blacklisted_pkgs,
                                            pkgs_kept_back) and
                is_pkgname_in_whitelist(pkg.name, whitelisted_pkgs) and
                is_allowed_origin(pkg.candidate, allowed_origins)):

            try_to_upgrade(pkg,
                           pkgs_to_upgrade,
                           pkgs_kept_back,
                           cache,
                           allowed_origins,
                           blacklisted_pkgs,
                           whitelisted_pkgs)
    return pkgs_to_upgrade, pkgs_kept_back


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
    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:
                content.append(line)
    return "".join(content)


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, pkgname, auto_removable, blacklisted_pkgs,
                        whitelisted_pkgs):
    # type: (apt.Cache, str, AbstractSet[str], List[str], List[str]) -> 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, blacklisted_pkgs, whitelisted_pkgs):
            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
    return True


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

    pkgs_removed = []         # type: List[str]
    pkgs_kept_installed = []  # type: List[str]
    if minimal_steps:
        for pkgname in auto_removable:
            if SIGNAL_STOP_REQUEST:
                logging.warning("SIGNAL received, stopping")
                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,
                                       blacklisted_pkgs, whitelisted_pkgs):
                # 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)
                res = True
                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:
                res = True
                cache.clear()
    else:
        for pkgname in auto_removable:
            cache[pkgname].mark_delete()
        if is_autoremove_valid(cache, "", auto_removable, blacklisted_pkgs,
                               whitelisted_pkgs):
            # do it in one step
            if not dry_run:
                res, error = cache_commit(cache, logfile_dpkg, verbose)
            else:
                res = True
                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:
        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 main(options, rootdir=""):
    # type: (Options, str) -> int
    # useful for testing
    if rootdir:
        _setup_alternative_rootdir(rootdir)

    # setup logging
    mem_log = _setup_logging(options)

    # check if today is a patch day
    if not is_update_day():
        return 0

    # format (origin, archive), e.g. ("Ubuntu","dapper-security")
    allowed_origins = get_allowed_origins()

    # pkgs that are (for some reason) not safe to install
    blacklisted_pkgs = get_blacklisted_pkgs()
    logging.info(_("Initial blacklisted packages: %s"),
                 " ".join(blacklisted_pkgs))

    # install only these packages regardless of other upgrades available
    whitelisted_pkgs = get_whitelisted_pkgs()
    logging.info(_("Initial whitelisted packages: %s"),
                 " ".join(whitelisted_pkgs))

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

    # 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")
        sys.exit(1)

    # display available origin
    logging.info(_("Allowed origins are: %s"), ", ".join(allowed_origins))

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

    # 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)):
        # ensure the dpkg database is not already locked (LP: #754330)
        admindir = os.path.dirname(apt_pkg.config.find("Dir::State::Status"))
        lockfd = apt_pkg.get_lock(os.path.join(admindir, "lock"), False)
        if lockfd > 0:
            logging.warning(
                _("Unclean dpkg state detected, trying to correct"))
            print(_("Unclean dpkg state detected, trying to correct"))
            env = copy.copy(os.environ)
            env["DEBIAN_FRONTEND"] = "noninteractive"
            try:
                os.close(lockfd)
                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)
        else:
            logging.debug("Unclean dpkg state, but locked, another package "
                          "manager working?")

    # check and get lock
    try:
        apt_pkg.pkgsystem_lock()
    except SystemError as e:
        logging.error(_("Lock could not be acquired (another package "
                        "manager running?)"))
        print(_("Cache lock can not be acquired, exiting"))
        sys.exit(1)

    # get a cache
    try:
        cache = UnattendedUpgradesCache(rootdir=rootdir,
                                        allowed_origins=allowed_origins)
    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)
        sys.exit(1)

    if cache._depcache.broken_count > 0:
        print(_("Cache has broken packages, exiting"))
        logging.error(_("Cache has broken packages, exiting"))
        sys.exit(1)

    # FIXME: make this into a ContextManager
    # be nice when calculating the upgrade as its pretty CPU intensive
    old_priority = os.nice(0)
    try:
        # Check that we will be able to restore the priority
        os.nice(-1)
        os.nice(20)
    except OSError as e:
        if e.errno in (errno.EPERM, errno.EACCES):
            pass
        else:
            raise

    # speed things up with latest apt
    actiongroup = apt_pkg.ActionGroup(cache._depcache)
    actiongroup  # pyflakes

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

    # FIXME: make this into a ContextManager
    # stop being nice
    os.nice(old_priority - os.nice(0))

    # download what looks good
    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 SIGNAL_STOP_REQUEST:
        logging.warning("SIGNAL received, stopping")
        return 1
    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 0

    pkg_conffile_prompt = False
    if dpkg_conffile_prompt():
        # now check the downloaded debs for conffile conflicts and build
        # a blacklist
        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)
                sys.exit(1)
            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)
                sys.exit(1)
            if not item.is_trusted:
                blacklisted_pkgs.append(pkgname_from_deb(item.destfile))
            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))
                blacklisted_pkgs.append(pkgname_from_deb(item.destfile))
                pkgs_kept_back.append(pkgname_from_deb(item.destfile))
                pkg_conffile_prompt = True

        # redo the selection about the packages to upgrade based on the new
        # blacklist
        logging.debug("blacklist: %s" % blacklisted_pkgs)
        # whitelist
        logging.debug("whitelist: %s" % whitelisted_pkgs)
        # find out about the packages that are upgradable (in a allowed_origin)
        if len(blacklisted_pkgs) > 0 or len(whitelisted_pkgs) > 0:
            cache.clear()
            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))
                pkg.mark_upgrade(from_user=not pkg.is_auto_installed)
                if check_changes_for_sanity(cache,
                                            allowed_origins,
                                            blacklisted_pkgs,
                                            whitelisted_pkgs):
                    pkgs_to_upgrade.append(pkg)
                else:
                    if not (pkg.name in pkgs_kept_back):
                        pkgs_kept_back.append(pkg.name)
                    logging.info(_("package %s not upgraded"), pkg.name)
                    cache.clear()
                    for pkg2 in pkgs_to_upgrade:
                        pkg2.mark_upgrade(from_user=not pkg2.is_auto_installed)
    else:
        logging.debug("dpkg is configured not to cause conffile prompts")

    # 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

    # auto-removals
    auto_removable = get_auto_removable(cache)
    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, use_minimal_steps(options),
                blacklisted_pkgs, whitelisted_pkgs,
                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 and
            len(pkgs_kept_back) == 0):
        logging.info(_("No packages found that can be upgraded unattended "
                       "and no pending auto-removals"))
        # FIXME: DRY violation, write_stamp_file() is used below as well
        write_stamp_file()
        # check if we couldn't reboot on previous run because
        # a user was logged-in at this time
        os.close(shutdown_lock)
        # never reboot during a dry run
        if not options.dry_run:
            reboot_if_requested_and_needed()
        return 0

    # 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")
        os.close(shutdown_lock)
        return 0

    # 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 = " ".join([pkg.name for pkg in pkgs_to_upgrade])
    logging.info(_("Packages that will be upgraded: %s"), 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_to_upgrade,
                                         blacklisted_pkgs,
                                         whitelisted_pkgs,
                                         options,
                                         logfile_dpkg)
    # Was the overall run succesful: only if everything installed
    # fine and nothing was held back because of a 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"))
        sys.exit(1)

    # 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, use_minimal_steps(options),
            blacklisted_pkgs, whitelisted_pkgs,
            options.verbose or options.debug,
            options.dry_run)
        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, use_minimal_steps(options),
            blacklisted_pkgs, whitelisted_pkgs,
            options.verbose or options.debug,
            options.dry_run)
        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))

    # send a mail (if needed)
    if not options.dry_run:
        log_content = get_dpkg_log_content(logfile_dpkg, install_start_time)
        send_summary_mail(
            pkgs, successful_run,
            pkgs_kept_back,
            kernel_pkgs_removed + pkgs_removed,
            kernel_pkgs_kept_installed + pkgs_kept_installed,
            mem_log, log_content)

    # 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)

    # FIXME: DRY violation, write_stamp_file() is used above as well
    # write timestamp file
    write_stamp_file()

    os.close(shutdown_lock)
    # check if the user wants a reboot
    if not options.dry_run:
        reboot_if_requested_and_needed()
    if successful_run:
        return 0
    else:
        return 1


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)

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

    # init the options
    parser = OptionParser()
    parser.add_option("-d", "--debug",
                      action="store_true", default=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=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=False,
                      help=_("Upgrade in minimal steps (and allow "
                             "interrupting with SIGTERM"))
    parser.add_option("", "--minimal_upgrade_steps",
                      action="store_true",
                      help=SUPPRESS_HELP,
                      default=False)
    (options, args) = parser.parse_args()  # type: ignore

    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))