/mandos/release

#!/usr/bin/python
# -*- mode: python; coding: utf-8 -*-
# 
# Mandos server - give out binary blobs to connecting clients.
# 
# This program is partly derived from an example program for an Avahi
# service publisher, downloaded from
# <http://avahi.org/wiki/PythonPublishExample>.  This includes the
# methods "add", "remove", "server_state_changed",
# "entry_group_state_changed", "cleanup", and "activate" in the
# "AvahiService" class, and some lines in "main".
# 
# Everything else is
# Copyright © 2008-2016 Teddy Hogeborn
# Copyright © 2008-2016 Björn Påhlsson
# 
# This program 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 3 of the License, or
# (at your option) any later version.
#
#     This program 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 this program.  If not, see
# <http://www.gnu.org/licenses/>.
# 
# Contact the authors at <mandos@recompile.se>.
# 

from __future__ import (division, absolute_import, print_function,
                        unicode_literals)

try:
    from future_builtins import *
except ImportError:
    pass

try:
    import SocketServer as socketserver
except ImportError:
    import socketserver
import socket
import argparse
import datetime
import errno
try:
    import ConfigParser as configparser
except ImportError:
    import configparser
import sys
import re
import os
import signal
import subprocess
import atexit
import stat
import logging
import logging.handlers
import pwd
import contextlib
import struct
import fcntl
import functools
try:
    import cPickle as pickle
except ImportError:
    import pickle
import multiprocessing
import types
import binascii
import tempfile
import itertools
import collections
import codecs

import dbus
import dbus.service
from gi.repository import GLib
from dbus.mainloop.glib import DBusGMainLoop
import ctypes
import ctypes.util
import xml.dom.minidom
import inspect

try:
    SO_BINDTODEVICE = socket.SO_BINDTODEVICE
except AttributeError:
    try:
        from IN import SO_BINDTODEVICE
    except ImportError:
        SO_BINDTODEVICE = None

if sys.version_info.major == 2:
    str = unicode

version = "1.7.7"
stored_state_file = "clients.pickle"

logger = logging.getLogger()
syslogger = None

try:
    if_nametoindex = ctypes.cdll.LoadLibrary(
        ctypes.util.find_library("c")).if_nametoindex
except (OSError, AttributeError):
    
    def if_nametoindex(interface):
        "Get an interface index the hard way, i.e. using fcntl()"
        SIOCGIFINDEX = 0x8933  # From /usr/include/linux/sockios.h
        with contextlib.closing(socket.socket()) as s:
            ifreq = fcntl.ioctl(s, SIOCGIFINDEX,
                                struct.pack(b"16s16x", interface))
        interface_index = struct.unpack("I", ifreq[16:20])[0]
        return interface_index


def copy_function(func):
    """Make a copy of a function"""
    if sys.version_info.major == 2:
        return types.FunctionType(func.func_code,
                                  func.func_globals,
                                  func.func_name,
                                  func.func_defaults,
                                  func.func_closure)
    else:
        return types.FunctionType(func.__code__,
                                  func.__globals__,
                                  func.__name__,
                                  func.__defaults__,
                                  func.__closure__)


def initlogger(debug, level=logging.WARNING):
    """init logger and add loglevel"""
    
    global syslogger
    syslogger = (logging.handlers.SysLogHandler(
        facility = logging.handlers.SysLogHandler.LOG_DAEMON,
        address = "/dev/log"))
    syslogger.setFormatter(logging.Formatter
                           ('Mandos [%(process)d]: %(levelname)s:'
                            ' %(message)s'))
    logger.addHandler(syslogger)
    
    if debug:
        console = logging.StreamHandler()
        console.setFormatter(logging.Formatter('%(asctime)s %(name)s'
                                               ' [%(process)d]:'
                                               ' %(levelname)s:'
                                               ' %(message)s'))
        logger.addHandler(console)
    logger.setLevel(level)


class PGPError(Exception):
    """Exception if encryption/decryption fails"""
    pass


class PGPEngine(object):
    """A simple class for OpenPGP symmetric encryption & decryption"""
    
    def __init__(self):
        self.tempdir = tempfile.mkdtemp(prefix="mandos-")
        self.gpg = "gpg"
        try:
            output = subprocess.check_output(["gpgconf"])
            for line in output.splitlines():
                name, text, path = line.split(b":")
                if name == "gpg":
                    self.gpg = path
                    break
        except OSError as e:
            if e.errno != errno.ENOENT:
                raise
        self.gnupgargs = ['--batch',
                          '--homedir', self.tempdir,
                          '--force-mdc',
                          '--quiet',
                          '--no-use-agent']
    
    def __enter__(self):
        return self
    
    def __exit__(self, exc_type, exc_value, traceback):
        self._cleanup()
        return False
    
    def __del__(self):
        self._cleanup()
    
    def _cleanup(self):
        if self.tempdir is not None:
            # Delete contents of tempdir
            for root, dirs, files in os.walk(self.tempdir,
                                             topdown = False):
                for filename in files:
                    os.remove(os.path.join(root, filename))
                for dirname in dirs:
                    os.rmdir(os.path.join(root, dirname))
            # Remove tempdir
            os.rmdir(self.tempdir)
            self.tempdir = None
    
    def password_encode(self, password):
        # Passphrase can not be empty and can not contain newlines or
        # NUL bytes.  So we prefix it and hex encode it.
        encoded = b"mandos" + binascii.hexlify(password)
        if len(encoded) > 2048:
            # GnuPG can't handle long passwords, so encode differently
            encoded = (b"mandos" + password.replace(b"\\", b"\\\\")
                       .replace(b"\n", b"\\n")
                       .replace(b"\0", b"\\x00"))
        return encoded
    
    def encrypt(self, data, password):
        passphrase = self.password_encode(password)
        with tempfile.NamedTemporaryFile(
                dir=self.tempdir) as passfile:
            passfile.write(passphrase)
            passfile.flush()
            proc = subprocess.Popen([self.gpg, '--symmetric',
                                     '--passphrase-file',
                                     passfile.name]
                                    + self.gnupgargs,
                                    stdin = subprocess.PIPE,
                                    stdout = subprocess.PIPE,
                                    stderr = subprocess.PIPE)
            ciphertext, err = proc.communicate(input = data)
        if proc.returncode != 0:
            raise PGPError(err)
        return ciphertext
    
    def decrypt(self, data, password):
        passphrase = self.password_encode(password)
        with tempfile.NamedTemporaryFile(
                dir = self.tempdir) as passfile:
            passfile.write(passphrase)
            passfile.flush()
            proc = subprocess.Popen([self.gpg, '--decrypt',
                                     '--passphrase-file',
                                     passfile.name]
                                    + self.gnupgargs,
                                    stdin = subprocess.PIPE,
                                    stdout = subprocess.PIPE,
                                    stderr = subprocess.PIPE)
            decrypted_plaintext, err = proc.communicate(input = data)
        if proc.returncode != 0:
            raise PGPError(err)
        return decrypted_plaintext

# Pretend that we have an Avahi module
class Avahi(object):
    """This isn't so much a class as it is a module-like namespace.
    It is instantiated once, and simulates having an Avahi module."""
    IF_UNSPEC = -1              # avahi-common/address.h
    PROTO_UNSPEC = -1           # avahi-common/address.h
    PROTO_INET = 0              # avahi-common/address.h
    PROTO_INET6 = 1             # avahi-common/address.h
    DBUS_NAME = "org.freedesktop.Avahi"
    DBUS_INTERFACE_ENTRY_GROUP = DBUS_NAME + ".EntryGroup"
    DBUS_INTERFACE_SERVER = DBUS_NAME + ".Server"
    DBUS_PATH_SERVER = "/"
    def string_array_to_txt_array(self, t):
        return dbus.Array((dbus.ByteArray(s.encode("utf-8"))
                           for s in t), signature="ay")
    ENTRY_GROUP_ESTABLISHED = 2 # avahi-common/defs.h
    ENTRY_GROUP_COLLISION = 3   # avahi-common/defs.h
    ENTRY_GROUP_FAILURE = 4     # avahi-common/defs.h
    SERVER_INVALID = 0          # avahi-common/defs.h
    SERVER_REGISTERING = 1      # avahi-common/defs.h
    SERVER_RUNNING = 2          # avahi-common/defs.h
    SERVER_COLLISION = 3        # avahi-common/defs.h
    SERVER_FAILURE = 4          # avahi-common/defs.h
avahi = Avahi()

class AvahiError(Exception):
    def __init__(self, value, *args, **kwargs):
        self.value = value
        return super(AvahiError, self).__init__(value, *args,
                                                **kwargs)


class AvahiServiceError(AvahiError):
    pass


class AvahiGroupError(AvahiError):
    pass


class AvahiService(object):
    """An Avahi (Zeroconf) service.
    
    Attributes:
    interface: integer; avahi.IF_UNSPEC or an interface index.
               Used to optionally bind to the specified interface.
    name: string; Example: 'Mandos'
    type: string; Example: '_mandos._tcp'.
     See <https://www.iana.org/assignments/service-names-port-numbers>
    port: integer; what port to announce
    TXT: list of strings; TXT record for the service
    domain: string; Domain to publish on, default to .local if empty.
    host: string; Host to publish records for, default is localhost
    max_renames: integer; maximum number of renames
    rename_count: integer; counter so we only rename after collisions
                  a sensible number of times
    group: D-Bus Entry Group
    server: D-Bus Server
    bus: dbus.SystemBus()
    """
    
    def __init__(self,
                 interface = avahi.IF_UNSPEC,
                 name = None,
                 servicetype = None,
                 port = None,
                 TXT = None,
                 domain = "",
                 host = "",
                 max_renames = 32768,
                 protocol = avahi.PROTO_UNSPEC,
                 bus = None):
        self.interface = interface
        self.name = name
        self.type = servicetype
        self.port = port
        self.TXT = TXT if TXT is not None else []
        self.domain = domain
        self.host = host
        self.rename_count = 0
        self.max_renames = max_renames
        self.protocol = protocol
        self.group = None       # our entry group
        self.server = None
        self.bus = bus
        self.entry_group_state_changed_match = None
    
    def rename(self, remove=True):
        """Derived from the Avahi example code"""
        if self.rename_count >= self.max_renames:
            logger.critical("No suitable Zeroconf service name found"
                            " after %i retries, exiting.",
                            self.rename_count)
            raise AvahiServiceError("Too many renames")
        self.name = str(
            self.server.GetAlternativeServiceName(self.name))
        self.rename_count += 1
        logger.info("Changing Zeroconf service name to %r ...",
                    self.name)
        if remove:
            self.remove()
        try:
            self.add()
        except dbus.exceptions.DBusException as error:
            if (error.get_dbus_name()
                == "org.freedesktop.Avahi.CollisionError"):
                logger.info("Local Zeroconf service name collision.")
                return self.rename(remove=False)
            else:
                logger.critical("D-Bus Exception", exc_info=error)
                self.cleanup()
                os._exit(1)
    
    def remove(self):
        """Derived from the Avahi example code"""
        if self.entry_group_state_changed_match is not None:
            self.entry_group_state_changed_match.remove()
            self.entry_group_state_changed_match = None
        if self.group is not None:
            self.group.Reset()
    
    def add(self):
        """Derived from the Avahi example code"""
        self.remove()
        if self.group is None:
            self.group = dbus.Interface(
                self.bus.get_object(avahi.DBUS_NAME,
                                    self.server.EntryGroupNew()),
                avahi.DBUS_INTERFACE_ENTRY_GROUP)
        self.entry_group_state_changed_match = (
            self.group.connect_to_signal(
                'StateChanged', self.entry_group_state_changed))
        logger.debug("Adding Zeroconf service '%s' of type '%s' ...",
                     self.name, self.type)
        self.group.AddService(
            self.interface,
            self.protocol,
            dbus.UInt32(0),     # flags
            self.name, self.type,
            self.domain, self.host,
            dbus.UInt16(self.port),
            avahi.string_array_to_txt_array(self.TXT))
        self.group.Commit()
    
    def entry_group_state_changed(self, state, error):
        """Derived from the Avahi example code"""
        logger.debug("Avahi entry group state change: %i", state)
        
        if state == avahi.ENTRY_GROUP_ESTABLISHED:
            logger.debug("Zeroconf service established.")
        elif state == avahi.ENTRY_GROUP_COLLISION:
            logger.info("Zeroconf service name collision.")
            self.rename()
        elif state == avahi.ENTRY_GROUP_FAILURE:
            logger.critical("Avahi: Error in group state changed %s",
                            str(error))
            raise AvahiGroupError("State changed: {!s}".format(error))
    
    def cleanup(self):
        """Derived from the Avahi example code"""
        if self.group is not None:
            try:
                self.group.Free()
            except (dbus.exceptions.UnknownMethodException,
                    dbus.exceptions.DBusException):
                pass
            self.group = None
        self.remove()
    
    def server_state_changed(self, state, error=None):
        """Derived from the Avahi example code"""
        logger.debug("Avahi server state change: %i", state)
        bad_states = {
            avahi.SERVER_INVALID: "Zeroconf server invalid",
            avahi.SERVER_REGISTERING: None,
            avahi.SERVER_COLLISION: "Zeroconf server name collision",
            avahi.SERVER_FAILURE: "Zeroconf server failure",
        }
        if state in bad_states:
            if bad_states[state] is not None:
                if error is None:
                    logger.error(bad_states[state])
                else:
                    logger.error(bad_states[state] + ": %r", error)
            self.cleanup()
        elif state == avahi.SERVER_RUNNING:
            try:
                self.add()
            except dbus.exceptions.DBusException as error:
                if (error.get_dbus_name()
                    == "org.freedesktop.Avahi.CollisionError"):
                    logger.info("Local Zeroconf service name"
                                " collision.")
                    return self.rename(remove=False)
                else:
                    logger.critical("D-Bus Exception", exc_info=error)
                    self.cleanup()
                    os._exit(1)
        else:
            if error is None:
                logger.debug("Unknown state: %r", state)
            else:
                logger.debug("Unknown state: %r: %r", state, error)
    
    def activate(self):
        """Derived from the Avahi example code"""
        if self.server is None:
            self.server = dbus.Interface(
                self.bus.get_object(avahi.DBUS_NAME,
                                    avahi.DBUS_PATH_SERVER,
                                    follow_name_owner_changes=True),
                avahi.DBUS_INTERFACE_SERVER)
        self.server.connect_to_signal("StateChanged",
                                      self.server_state_changed)
        self.server_state_changed(self.server.GetState())


class AvahiServiceToSyslog(AvahiService):
    def rename(self, *args, **kwargs):
        """Add the new name to the syslog messages"""
        ret = AvahiService.rename(self, *args, **kwargs)
        syslogger.setFormatter(logging.Formatter(
            'Mandos ({}) [%(process)d]: %(levelname)s: %(message)s'
            .format(self.name)))
        return ret

# Pretend that we have a GnuTLS module
class GnuTLS(object):
    """This isn't so much a class as it is a module-like namespace.
    It is instantiated once, and simulates having a GnuTLS module."""
    
    _library = ctypes.cdll.LoadLibrary(
        ctypes.util.find_library("gnutls"))
    _need_version = b"3.3.0"
    def __init__(self):
        # Need to use class name "GnuTLS" here, since this method is
        # called before the assignment to the "gnutls" global variable
        # happens.
        if GnuTLS.check_version(self._need_version) is None:
            raise GnuTLS.Error("Needs GnuTLS {} or later"
                               .format(self._need_version))
    
    # Unless otherwise indicated, the constants and types below are
    # all from the gnutls/gnutls.h C header file.
    
    # Constants
    E_SUCCESS = 0
    E_INTERRUPTED = -52
    E_AGAIN = -28
    CRT_OPENPGP = 2
    CLIENT = 2
    SHUT_RDWR = 0
    CRD_CERTIFICATE = 1
    E_NO_CERTIFICATE_FOUND = -49
    OPENPGP_FMT_RAW = 0         # gnutls/openpgp.h
    
    # Types
    class session_int(ctypes.Structure):
        _fields_ = []
    session_t = ctypes.POINTER(session_int)
    class certificate_credentials_st(ctypes.Structure):
        _fields_ = []
    certificate_credentials_t = ctypes.POINTER(
        certificate_credentials_st)
    certificate_type_t = ctypes.c_int
    class datum_t(ctypes.Structure):
        _fields_ = [('data', ctypes.POINTER(ctypes.c_ubyte)),
                    ('size', ctypes.c_uint)]
    class openpgp_crt_int(ctypes.Structure):
        _fields_ = []
    openpgp_crt_t = ctypes.POINTER(openpgp_crt_int)
    openpgp_crt_fmt_t = ctypes.c_int # gnutls/openpgp.h
    log_func = ctypes.CFUNCTYPE(None, ctypes.c_int, ctypes.c_char_p)
    credentials_type_t = ctypes.c_int
    transport_ptr_t = ctypes.c_void_p
    close_request_t = ctypes.c_int
    
    # Exceptions
    class Error(Exception):
        # We need to use the class name "GnuTLS" here, since this
        # exception might be raised from within GnuTLS.__init__,
        # which is called before the assignment to the "gnutls"
        # global variable has happened.
        def __init__(self, message = None, code = None, args=()):
            # Default usage is by a message string, but if a return
            # code is passed, convert it to a string with
            # gnutls.strerror()
            self.code = code
            if message is None and code is not None:
                message = GnuTLS.strerror(code)
            return super(GnuTLS.Error, self).__init__(
                message, *args)
    
    class CertificateSecurityError(Error):
        pass
    
    # Classes
    class Credentials(object):
        def __init__(self):
            self._c_object = gnutls.certificate_credentials_t()
            gnutls.certificate_allocate_credentials(
                ctypes.byref(self._c_object))
            self.type = gnutls.CRD_CERTIFICATE
        
        def __del__(self):
            gnutls.certificate_free_credentials(self._c_object)
    
    class ClientSession(object):
        def __init__(self, socket, credentials = None):
            self._c_object = gnutls.session_t()
            gnutls.init(ctypes.byref(self._c_object), gnutls.CLIENT)
            gnutls.set_default_priority(self._c_object)
            gnutls.transport_set_ptr(self._c_object, socket.fileno())
            gnutls.handshake_set_private_extensions(self._c_object,
                                                    True)
            self.socket = socket
            if credentials is None:
                credentials = gnutls.Credentials()
            gnutls.credentials_set(self._c_object, credentials.type,
                                   ctypes.cast(credentials._c_object,
                                               ctypes.c_void_p))
            self.credentials = credentials
        
        def __del__(self):
            gnutls.deinit(self._c_object)
        
        def handshake(self):
            return gnutls.handshake(self._c_object)
        
        def send(self, data):
            data = bytes(data)
            data_len = len(data)
            while data_len > 0:
                data_len -= gnutls.record_send(self._c_object,
                                               data[-data_len:],
                                               data_len)
        
        def bye(self):
            return gnutls.bye(self._c_object, gnutls.SHUT_RDWR)
    
    # Error handling functions
    def _error_code(result):
        """A function to raise exceptions on errors, suitable
        for the 'restype' attribute on ctypes functions"""
        if result >= 0:
            return result
        if result == gnutls.E_NO_CERTIFICATE_FOUND:
            raise gnutls.CertificateSecurityError(code = result)
        raise gnutls.Error(code = result)
    
    def _retry_on_error(result, func, arguments):
        """A function to retry on some errors, suitable
        for the 'errcheck' attribute on ctypes functions"""
        while result < 0:
            if result not in (gnutls.E_INTERRUPTED, gnutls.E_AGAIN):
                return _error_code(result)
            result = func(*arguments)
        return result
    
    # Unless otherwise indicated, the function declarations below are
    # all from the gnutls/gnutls.h C header file.
    
    # Functions
    priority_set_direct = _library.gnutls_priority_set_direct
    priority_set_direct.argtypes = [session_t, ctypes.c_char_p,
                                    ctypes.POINTER(ctypes.c_char_p)]
    priority_set_direct.restype = _error_code
    
    init = _library.gnutls_init
    init.argtypes = [ctypes.POINTER(session_t), ctypes.c_int]
    init.restype = _error_code
    
    set_default_priority = _library.gnutls_set_default_priority
    set_default_priority.argtypes = [session_t]
    set_default_priority.restype = _error_code
    
    record_send = _library.gnutls_record_send
    record_send.argtypes = [session_t, ctypes.c_void_p,
                            ctypes.c_size_t]
    record_send.restype = ctypes.c_ssize_t
    record_send.errcheck = _retry_on_error
    
    certificate_allocate_credentials = (
        _library.gnutls_certificate_allocate_credentials)
    certificate_allocate_credentials.argtypes = [
        ctypes.POINTER(certificate_credentials_t)]
    certificate_allocate_credentials.restype = _error_code
    
    certificate_free_credentials = (
        _library.gnutls_certificate_free_credentials)
    certificate_free_credentials.argtypes = [certificate_credentials_t]
    certificate_free_credentials.restype = None
    
    handshake_set_private_extensions = (
        _library.gnutls_handshake_set_private_extensions)
    handshake_set_private_extensions.argtypes = [session_t,
                                                 ctypes.c_int]
    handshake_set_private_extensions.restype = None
    
    credentials_set = _library.gnutls_credentials_set
    credentials_set.argtypes = [session_t, credentials_type_t,
                                ctypes.c_void_p]
    credentials_set.restype = _error_code
    
    strerror = _library.gnutls_strerror
    strerror.argtypes = [ctypes.c_int]
    strerror.restype = ctypes.c_char_p
    
    certificate_type_get = _library.gnutls_certificate_type_get
    certificate_type_get.argtypes = [session_t]
    certificate_type_get.restype = _error_code
    
    certificate_get_peers = _library.gnutls_certificate_get_peers
    certificate_get_peers.argtypes = [session_t,
                                      ctypes.POINTER(ctypes.c_uint)]
    certificate_get_peers.restype = ctypes.POINTER(datum_t)
    
    global_set_log_level = _library.gnutls_global_set_log_level
    global_set_log_level.argtypes = [ctypes.c_int]
    global_set_log_level.restype = None
    
    global_set_log_function = _library.gnutls_global_set_log_function
    global_set_log_function.argtypes = [log_func]
    global_set_log_function.restype = None
    
    deinit = _library.gnutls_deinit
    deinit.argtypes = [session_t]
    deinit.restype = None
    
    handshake = _library.gnutls_handshake
    handshake.argtypes = [session_t]
    handshake.restype = _error_code
    handshake.errcheck = _retry_on_error
    
    transport_set_ptr = _library.gnutls_transport_set_ptr
    transport_set_ptr.argtypes = [session_t, transport_ptr_t]
    transport_set_ptr.restype = None
    
    bye = _library.gnutls_bye
    bye.argtypes = [session_t, close_request_t]
    bye.restype = _error_code
    bye.errcheck = _retry_on_error
    
    check_version = _library.gnutls_check_version
    check_version.argtypes = [ctypes.c_char_p]
    check_version.restype = ctypes.c_char_p
    
    # All the function declarations below are from gnutls/openpgp.h
    
    openpgp_crt_init = _library.gnutls_openpgp_crt_init
    openpgp_crt_init.argtypes = [ctypes.POINTER(openpgp_crt_t)]
    openpgp_crt_init.restype = _error_code
    
    openpgp_crt_import = _library.gnutls_openpgp_crt_import
    openpgp_crt_import.argtypes = [openpgp_crt_t,
                                   ctypes.POINTER(datum_t),
                                   openpgp_crt_fmt_t]
    openpgp_crt_import.restype = _error_code
    
    openpgp_crt_verify_self = _library.gnutls_openpgp_crt_verify_self
    openpgp_crt_verify_self.argtypes = [openpgp_crt_t, ctypes.c_uint,
                                        ctypes.POINTER(ctypes.c_uint)]
    openpgp_crt_verify_self.restype = _error_code
    
    openpgp_crt_deinit = _library.gnutls_openpgp_crt_deinit
    openpgp_crt_deinit.argtypes = [openpgp_crt_t]
    openpgp_crt_deinit.restype = None
    
    openpgp_crt_get_fingerprint = (
        _library.gnutls_openpgp_crt_get_fingerprint)
    openpgp_crt_get_fingerprint.argtypes = [openpgp_crt_t,
                                            ctypes.c_void_p,
                                            ctypes.POINTER(
                                                ctypes.c_size_t)]
    openpgp_crt_get_fingerprint.restype = _error_code
    
    # Remove non-public functions
    del _error_code, _retry_on_error
# Create the global "gnutls" object, simulating a module
gnutls = GnuTLS()

def call_pipe(connection,       # : multiprocessing.Connection
              func, *args, **kwargs):
    """This function is meant to be called by multiprocessing.Process
    
    This function runs func(*args, **kwargs), and writes the resulting
    return value on the provided multiprocessing.Connection.
    """
    connection.send(func(*args, **kwargs))
    connection.close()

class Client(object):
    """A representation of a client host served by this server.
    
    Attributes:
    approved:   bool(); 'None' if not yet approved/disapproved
    approval_delay: datetime.timedelta(); Time to wait for approval
    approval_duration: datetime.timedelta(); Duration of one approval
    checker:    subprocess.Popen(); a running checker process used
                                    to see if the client lives.
                                    'None' if no process is running.
    checker_callback_tag: a GLib event source tag, or None
    checker_command: string; External command which is run to check
                     if client lives.  %() expansions are done at
                     runtime with vars(self) as dict, so that for
                     instance %(name)s can be used in the command.
    checker_initiator_tag: a GLib event source tag, or None
    created:    datetime.datetime(); (UTC) object creation
    client_structure: Object describing what attributes a client has
                      and is used for storing the client at exit
    current_checker_command: string; current running checker_command
    disable_initiator_tag: a GLib event source tag, or None
    enabled:    bool()
    fingerprint: string (40 or 32 hexadecimal digits); used to
                 uniquely identify the client
    host:       string; available for use by the checker command
    interval:   datetime.timedelta(); How often to start a new checker
    last_approval_request: datetime.datetime(); (UTC) or None
    last_checked_ok: datetime.datetime(); (UTC) or None
    last_checker_status: integer between 0 and 255 reflecting exit
                         status of last checker. -1 reflects crashed
                         checker, -2 means no checker completed yet.
    last_checker_signal: The signal which killed the last checker, if
                         last_checker_status is -1
    last_enabled: datetime.datetime(); (UTC) or None
    name:       string; from the config file, used in log messages and
                        D-Bus identifiers
    secret:     bytestring; sent verbatim (over TLS) to client
    timeout:    datetime.timedelta(); How long from last_checked_ok
                                      until this client is disabled
    extended_timeout:   extra long timeout when secret has been sent
    runtime_expansions: Allowed attributes for runtime expansion.
    expires:    datetime.datetime(); time (UTC) when a client will be
                disabled, or None
    server_settings: The server_settings dict from main()
    """
    
    runtime_expansions = ("approval_delay", "approval_duration",
                          "created", "enabled", "expires",
                          "fingerprint", "host", "interval",
                          "last_approval_request", "last_checked_ok",
                          "last_enabled", "name", "timeout")
    client_defaults = {
        "timeout": "PT5M",
        "extended_timeout": "PT15M",
        "interval": "PT2M",
        "checker": "fping -q -- %%(host)s",
        "host": "",
        "approval_delay": "PT0S",
        "approval_duration": "PT1S",
        "approved_by_default": "True",
        "enabled": "True",
    }
    
    @staticmethod
    def config_parser(config):
        """Construct a new dict of client settings of this form:
        { client_name: {setting_name: value, ...}, ...}
        with exceptions for any special settings as defined above.
        NOTE: Must be a pure function. Must return the same result
        value given the same arguments.
        """
        settings = {}
        for client_name in config.sections():
            section = dict(config.items(client_name))
            client = settings[client_name] = {}
            
            client["host"] = section["host"]
            # Reformat values from string types to Python types
            client["approved_by_default"] = config.getboolean(
                client_name, "approved_by_default")
            client["enabled"] = config.getboolean(client_name,
                                                  "enabled")
            
            # Uppercase and remove spaces from fingerprint for later
            # comparison purposes with return value from the
            # fingerprint() function
            client["fingerprint"] = (section["fingerprint"].upper()
                                     .replace(" ", ""))
            if "secret" in section:
                client["secret"] = codecs.decode(section["secret"]
                                                 .encode("utf-8"),
                                                 "base64")
            elif "secfile" in section:
                with open(os.path.expanduser(os.path.expandvars
                                             (section["secfile"])),
                          "rb") as secfile:
                    client["secret"] = secfile.read()
            else:
                raise TypeError("No secret or secfile for section {}"
                                .format(section))
            client["timeout"] = string_to_delta(section["timeout"])
            client["extended_timeout"] = string_to_delta(
                section["extended_timeout"])
            client["interval"] = string_to_delta(section["interval"])
            client["approval_delay"] = string_to_delta(
                section["approval_delay"])
            client["approval_duration"] = string_to_delta(
                section["approval_duration"])
            client["checker_command"] = section["checker"]
            client["last_approval_request"] = None
            client["last_checked_ok"] = None
            client["last_checker_status"] = -2
        
        return settings
    
    def __init__(self, settings, name = None, server_settings=None):
        self.name = name
        if server_settings is None:
            server_settings = {}
        self.server_settings = server_settings
        # adding all client settings
        for setting, value in settings.items():
            setattr(self, setting, value)
        
        if self.enabled:
            if not hasattr(self, "last_enabled"):
                self.last_enabled = datetime.datetime.utcnow()
            if not hasattr(self, "expires"):
                self.expires = (datetime.datetime.utcnow()
                                + self.timeout)
        else:
            self.last_enabled = None
            self.expires = None
        
        logger.debug("Creating client %r", self.name)
        logger.debug("  Fingerprint: %s", self.fingerprint)
        self.created = settings.get("created",
                                    datetime.datetime.utcnow())
        
        # attributes specific for this server instance
        self.checker = None
        self.checker_initiator_tag = None
        self.disable_initiator_tag = None
        self.checker_callback_tag = None
        self.current_checker_command = None
        self.approved = None
        self.approvals_pending = 0
        self.changedstate = multiprocessing_manager.Condition(
            multiprocessing_manager.Lock())
        self.client_structure = [attr
                                 for attr in self.__dict__.keys()
                                 if not attr.startswith("_")]
        self.client_structure.append("client_structure")
        
        for name, t in inspect.getmembers(
                type(self), lambda obj: isinstance(obj, property)):
            if not name.startswith("_"):
                self.client_structure.append(name)
    
    # Send notice to process children that client state has changed
    def send_changedstate(self):
        with self.changedstate:
            self.changedstate.notify_all()
    
    def enable(self):
        """Start this client's checker and timeout hooks"""
        if getattr(self, "enabled", False):
            # Already enabled
            return
        self.expires = datetime.datetime.utcnow() + self.timeout
        self.enabled = True
        self.last_enabled = datetime.datetime.utcnow()
        self.init_checker()
        self.send_changedstate()
    
    def disable(self, quiet=True):
        """Disable this client."""
        if not getattr(self, "enabled", False):
            return False
        if not quiet:
            logger.info("Disabling client %s", self.name)
        if getattr(self, "disable_initiator_tag", None) is not None:
            GLib.source_remove(self.disable_initiator_tag)
            self.disable_initiator_tag = None
        self.expires = None
        if getattr(self, "checker_initiator_tag", None) is not None:
            GLib.source_remove(self.checker_initiator_tag)
            self.checker_initiator_tag = None
        self.stop_checker()
        self.enabled = False
        if not quiet:
            self.send_changedstate()
        # Do not run this again if called by a GLib.timeout_add
        return False
    
    def __del__(self):
        self.disable()
    
    def init_checker(self):
        # Schedule a new checker to be started an 'interval' from now,
        # and every interval from then on.
        if self.checker_initiator_tag is not None:
            GLib.source_remove(self.checker_initiator_tag)
        self.checker_initiator_tag = GLib.timeout_add(
            int(self.interval.total_seconds() * 1000),
            self.start_checker)
        # Schedule a disable() when 'timeout' has passed
        if self.disable_initiator_tag is not None:
            GLib.source_remove(self.disable_initiator_tag)
        self.disable_initiator_tag = GLib.timeout_add(
            int(self.timeout.total_seconds() * 1000), self.disable)
        # Also start a new checker *right now*.
        self.start_checker()
    
    def checker_callback(self, source, condition, connection,
                         command):
        """The checker has completed, so take appropriate actions."""
        self.checker_callback_tag = None
        self.checker = None
        # Read return code from connection (see call_pipe)
        returncode = connection.recv()
        connection.close()
        
        if returncode >= 0:
            self.last_checker_status = returncode
            self.last_checker_signal = None
            if self.last_checker_status == 0:
                logger.info("Checker for %(name)s succeeded",
                            vars(self))
                self.checked_ok()
            else:
                logger.info("Checker for %(name)s failed", vars(self))
        else:
            self.last_checker_status = -1
            self.last_checker_signal = -returncode
            logger.warning("Checker for %(name)s crashed?",
                           vars(self))
        return False
    
    def checked_ok(self):
        """Assert that the client has been seen, alive and well."""
        self.last_checked_ok = datetime.datetime.utcnow()
        self.last_checker_status = 0
        self.last_checker_signal = None
        self.bump_timeout()
    
    def bump_timeout(self, timeout=None):
        """Bump up the timeout for this client."""
        if timeout is None:
            timeout = self.timeout
        if self.disable_initiator_tag is not None:
            GLib.source_remove(self.disable_initiator_tag)
            self.disable_initiator_tag = None
        if getattr(self, "enabled", False):
            self.disable_initiator_tag = GLib.timeout_add(
                int(timeout.total_seconds() * 1000), self.disable)
            self.expires = datetime.datetime.utcnow() + timeout
    
    def need_approval(self):
        self.last_approval_request = datetime.datetime.utcnow()
    
    def start_checker(self):
        """Start a new checker subprocess if one is not running.
        
        If a checker already exists, leave it running and do
        nothing."""
        # The reason for not killing a running checker is that if we
        # did that, and if a checker (for some reason) started running
        # slowly and taking more than 'interval' time, then the client
        # would inevitably timeout, since no checker would get a
        # chance to run to completion.  If we instead leave running
        # checkers alone, the checker would have to take more time
        # than 'timeout' for the client to be disabled, which is as it
        # should be.
        
        if self.checker is not None and not self.checker.is_alive():
            logger.warning("Checker was not alive; joining")
            self.checker.join()
            self.checker = None
        # Start a new checker if needed
        if self.checker is None:
            # Escape attributes for the shell
            escaped_attrs = {
                attr: re.escape(str(getattr(self, attr)))
                for attr in self.runtime_expansions }
            try:
                command = self.checker_command % escaped_attrs
            except TypeError as error:
                logger.error('Could not format string "%s"',
                             self.checker_command,
                             exc_info=error)
                return True     # Try again later
            self.current_checker_command = command
            logger.info("Starting checker %r for %s", command,
                        self.name)
            # We don't need to redirect stdout and stderr, since
            # in normal mode, that is already done by daemon(),
            # and in debug mode we don't want to.  (Stdin is
            # always replaced by /dev/null.)
            # The exception is when not debugging but nevertheless
            # running in the foreground; use the previously
            # created wnull.
            popen_args = { "close_fds": True,
                           "shell": True,
                           "cwd": "/" }
            if (not self.server_settings["debug"]
                and self.server_settings["foreground"]):
                popen_args.update({"stdout": wnull,
                                   "stderr": wnull })
            pipe = multiprocessing.Pipe(duplex = False)
            self.checker = multiprocessing.Process(
                target = call_pipe,
                args = (pipe[1], subprocess.call, command),
                kwargs = popen_args)
            self.checker.start()
            self.checker_callback_tag = GLib.io_add_watch(
                pipe[0].fileno(), GLib.IO_IN,
                self.checker_callback, pipe[0], command)
        # Re-run this periodically if run by GLib.timeout_add
        return True
    
    def stop_checker(self):
        """Force the checker process, if any, to stop."""
        if self.checker_callback_tag:
            GLib.source_remove(self.checker_callback_tag)
            self.checker_callback_tag = None
        if getattr(self, "checker", None) is None:
            return
        logger.debug("Stopping checker for %(name)s", vars(self))
        self.checker.terminate()
        self.checker = None


def dbus_service_property(dbus_interface,
                          signature="v",
                          access="readwrite",
                          byte_arrays=False):
    """Decorators for marking methods of a DBusObjectWithProperties to
    become properties on the D-Bus.
    
    The decorated method will be called with no arguments by "Get"
    and with one argument by "Set".
    
    The parameters, where they are supported, are the same as
    dbus.service.method, except there is only "signature", since the
    type from Get() and the type sent to Set() is the same.
    """
    # Encoding deeply encoded byte arrays is not supported yet by the
    # "Set" method, so we fail early here:
    if byte_arrays and signature != "ay":
        raise ValueError("Byte arrays not supported for non-'ay'"
                         " signature {!r}".format(signature))
    
    def decorator(func):
        func._dbus_is_property = True
        func._dbus_interface = dbus_interface
        func._dbus_signature = signature
        func._dbus_access = access
        func._dbus_name = func.__name__
        if func._dbus_name.endswith("_dbus_property"):
            func._dbus_name = func._dbus_name[:-14]
        func._dbus_get_args_options = {'byte_arrays': byte_arrays }
        return func
    
    return decorator


def dbus_interface_annotations(dbus_interface):
    """Decorator for marking functions returning interface annotations
    
    Usage:
    
    @dbus_interface_annotations("org.example.Interface")
    def _foo(self):  # Function name does not matter
        return {"org.freedesktop.DBus.Deprecated": "true",
                "org.freedesktop.DBus.Property.EmitsChangedSignal":
                    "false"}
    """
    
    def decorator(func):
        func._dbus_is_interface = True
        func._dbus_interface = dbus_interface
        func._dbus_name = dbus_interface
        return func
    
    return decorator


def dbus_annotations(annotations):
    """Decorator to annotate D-Bus methods, signals or properties
    Usage:
    
    @dbus_annotations({"org.freedesktop.DBus.Deprecated": "true",
                       "org.freedesktop.DBus.Property."
                       "EmitsChangedSignal": "false"})
    @dbus_service_property("org.example.Interface", signature="b",
                           access="r")
    def Property_dbus_property(self):
        return dbus.Boolean(False)
    
    See also the DBusObjectWithAnnotations class.
    """
    
    def decorator(func):
        func._dbus_annotations = annotations
        return func
    
    return decorator


class DBusPropertyException(dbus.exceptions.DBusException):
    """A base class for D-Bus property-related exceptions
    """
    pass


class DBusPropertyAccessException(DBusPropertyException):
    """A property's access permissions disallows an operation.
    """
    pass


class DBusPropertyNotFound(DBusPropertyException):
    """An attempt was made to access a non-existing property.
    """
    pass


class DBusObjectWithAnnotations(dbus.service.Object):
    """A D-Bus object with annotations.
    
    Classes inheriting from this can use the dbus_annotations
    decorator to add annotations to methods or signals.
    """
    
    @staticmethod
    def _is_dbus_thing(thing):
        """Returns a function testing if an attribute is a D-Bus thing
        
        If called like _is_dbus_thing("method") it returns a function
        suitable for use as predicate to inspect.getmembers().
        """
        return lambda obj: getattr(obj, "_dbus_is_{}".format(thing),
                                   False)
    
    def _get_all_dbus_things(self, thing):
        """Returns a generator of (name, attribute) pairs
        """
        return ((getattr(athing.__get__(self), "_dbus_name", name),
                 athing.__get__(self))
                for cls in self.__class__.__mro__
                for name, athing in
                inspect.getmembers(cls, self._is_dbus_thing(thing)))
    
    @dbus.service.method(dbus.INTROSPECTABLE_IFACE,
                         out_signature = "s",
                         path_keyword = 'object_path',
                         connection_keyword = 'connection')
    def Introspect(self, object_path, connection):
        """Overloading of standard D-Bus method.
        
        Inserts annotation tags on methods and signals.
        """
        xmlstring = dbus.service.Object.Introspect(self, object_path,
                                                   connection)
        try:
            document = xml.dom.minidom.parseString(xmlstring)
            
            for if_tag in document.getElementsByTagName("interface"):
                # Add annotation tags
                for typ in ("method", "signal"):
                    for tag in if_tag.getElementsByTagName(typ):
                        annots = dict()
                        for name, prop in (self.
                                           _get_all_dbus_things(typ)):
                            if (name == tag.getAttribute("name")
                                and prop._dbus_interface
                                == if_tag.getAttribute("name")):
                                annots.update(getattr(
                                    prop, "_dbus_annotations", {}))
                        for name, value in annots.items():
                            ann_tag = document.createElement(
                                "annotation")
                            ann_tag.setAttribute("name", name)
                            ann_tag.setAttribute("value", value)
                            tag.appendChild(ann_tag)
                # Add interface annotation tags
                for annotation, value in dict(
                    itertools.chain.from_iterable(
                        annotations().items()
                        for name, annotations
                        in self._get_all_dbus_things("interface")
                        if name == if_tag.getAttribute("name")
                        )).items():
                    ann_tag = document.createElement("annotation")
                    ann_tag.setAttribute("name", annotation)
                    ann_tag.setAttribute("value", value)
                    if_tag.appendChild(ann_tag)
                # Fix argument name for the Introspect method itself
                if (if_tag.getAttribute("name")
                                == dbus.INTROSPECTABLE_IFACE):
                    for cn in if_tag.getElementsByTagName("method"):
                        if cn.getAttribute("name") == "Introspect":
                            for arg in cn.getElementsByTagName("arg"):
                                if (arg.getAttribute("direction")
                                    == "out"):
                                    arg.setAttribute("name",
                                                     "xml_data")
            xmlstring = document.toxml("utf-8")
            document.unlink()
        except (AttributeError, xml.dom.DOMException,
                xml.parsers.expat.ExpatError) as error:
            logger.error("Failed to override Introspection method",
                         exc_info=error)
        return xmlstring


class DBusObjectWithProperties(DBusObjectWithAnnotations):
    """A D-Bus object with properties.
    
    Classes inheriting from this can use the dbus_service_property
    decorator to expose methods as D-Bus properties.  It exposes the
    standard Get(), Set(), and GetAll() methods on the D-Bus.
    """
    
    def _get_dbus_property(self, interface_name, property_name):
        """Returns a bound method if one exists which is a D-Bus
        property with the specified name and interface.
        """
        for cls in self.__class__.__mro__:
            for name, value in inspect.getmembers(
                    cls, self._is_dbus_thing("property")):
                if (value._dbus_name == property_name
                    and value._dbus_interface == interface_name):
                    return value.__get__(self)
        
        # No such property
        raise DBusPropertyNotFound("{}:{}.{}".format(
            self.dbus_object_path, interface_name, property_name))
    
    @classmethod
    def _get_all_interface_names(cls):
        """Get a sequence of all interfaces supported by an object"""
        return (name for name in set(getattr(getattr(x, attr),
                                             "_dbus_interface", None)
                                     for x in (inspect.getmro(cls))
                                     for attr in dir(x))
                if name is not None)
    
    @dbus.service.method(dbus.PROPERTIES_IFACE,
                         in_signature="ss",
                         out_signature="v")
    def Get(self, interface_name, property_name):
        """Standard D-Bus property Get() method, see D-Bus standard.
        """
        prop = self._get_dbus_property(interface_name, property_name)
        if prop._dbus_access == "write":
            raise DBusPropertyAccessException(property_name)
        value = prop()
        if not hasattr(value, "variant_level"):
            return value
        return type(value)(value, variant_level=value.variant_level+1)
    
    @dbus.service.method(dbus.PROPERTIES_IFACE, in_signature="ssv")
    def Set(self, interface_name, property_name, value):
        """Standard D-Bus property Set() method, see D-Bus standard.
        """
        prop = self._get_dbus_property(interface_name, property_name)
        if prop._dbus_access == "read":
            raise DBusPropertyAccessException(property_name)
        if prop._dbus_get_args_options["byte_arrays"]:
            # The byte_arrays option is not supported yet on
            # signatures other than "ay".
            if prop._dbus_signature != "ay":
                raise ValueError("Byte arrays not supported for non-"
                                 "'ay' signature {!r}"
                                 .format(prop._dbus_signature))
            value = dbus.ByteArray(b''.join(chr(byte)
                                            for byte in value))
        prop(value)
    
    @dbus.service.method(dbus.PROPERTIES_IFACE,
                         in_signature="s",
                         out_signature="a{sv}")
    def GetAll(self, interface_name):
        """Standard D-Bus property GetAll() method, see D-Bus
        standard.
        
        Note: Will not include properties with access="write".
        """
        properties = {}
        for name, prop in self._get_all_dbus_things("property"):
            if (interface_name
                and interface_name != prop._dbus_interface):
                # Interface non-empty but did not match
                continue
            # Ignore write-only properties
            if prop._dbus_access == "write":
                continue
            value = prop()
            if not hasattr(value, "variant_level"):
                properties[name] = value
                continue
            properties[name] = type(value)(
                value, variant_level = value.variant_level + 1)
        return dbus.Dictionary(properties, signature="sv")
    
    @dbus.service.signal(dbus.PROPERTIES_IFACE, signature="sa{sv}as")
    def PropertiesChanged(self, interface_name, changed_properties,
                          invalidated_properties):
        """Standard D-Bus PropertiesChanged() signal, see D-Bus
        standard.
        """
        pass
    
    @dbus.service.method(dbus.INTROSPECTABLE_IFACE,
                         out_signature="s",
                         path_keyword='object_path',
                         connection_keyword='connection')
    def Introspect(self, object_path, connection):
        """Overloading of standard D-Bus method.
        
        Inserts property tags and interface annotation tags.
        """
        xmlstring = DBusObjectWithAnnotations.Introspect(self,
                                                         object_path,
                                                         connection)
        try:
            document = xml.dom.minidom.parseString(xmlstring)
            
            def make_tag(document, name, prop):
                e = document.createElement("property")
                e.setAttribute("name", name)
                e.setAttribute("type", prop._dbus_signature)
                e.setAttribute("access", prop._dbus_access)
                return e
            
            for if_tag in document.getElementsByTagName("interface"):
                # Add property tags
                for tag in (make_tag(document, name, prop)
                            for name, prop
                            in self._get_all_dbus_things("property")
                            if prop._dbus_interface
                            == if_tag.getAttribute("name")):
                    if_tag.appendChild(tag)
                # Add annotation tags for properties
                for tag in if_tag.getElementsByTagName("property"):
                    annots = dict()
                    for name, prop in self._get_all_dbus_things(
                            "property"):
                        if (name == tag.getAttribute("name")
                            and prop._dbus_interface
                            == if_tag.getAttribute("name")):
                            annots.update(getattr(
                                prop, "_dbus_annotations", {}))
                    for name, value in annots.items():
                        ann_tag = document.createElement(
                            "annotation")
                        ann_tag.setAttribute("name", name)
                        ann_tag.setAttribute("value", value)
                        tag.appendChild(ann_tag)
                # Add the names to the return values for the
                # "org.freedesktop.DBus.Properties" methods
                if (if_tag.getAttribute("name")
                    == "org.freedesktop.DBus.Properties"):
                    for cn in if_tag.getElementsByTagName("method"):
                        if cn.getAttribute("name") == "Get":
                            for arg in cn.getElementsByTagName("arg"):
                                if (arg.getAttribute("direction")
                                    == "out"):
                                    arg.setAttribute("name", "value")
                        elif cn.getAttribute("name") == "GetAll":
                            for arg in cn.getElementsByTagName("arg"):
                                if (arg.getAttribute("direction")
                                    == "out"):
                                    arg.setAttribute("name", "props")
            xmlstring = document.toxml("utf-8")
            document.unlink()
        except (AttributeError, xml.dom.DOMException,
                xml.parsers.expat.ExpatError) as error:
            logger.error("Failed to override Introspection method",
                         exc_info=error)
        return xmlstring

try:
    dbus.OBJECT_MANAGER_IFACE
except AttributeError:
    dbus.OBJECT_MANAGER_IFACE = "org.freedesktop.DBus.ObjectManager"

class DBusObjectWithObjectManager(DBusObjectWithAnnotations):
    """A D-Bus object with an ObjectManager.
    
    Classes inheriting from this exposes the standard
    GetManagedObjects call and the InterfacesAdded and
    InterfacesRemoved signals on the standard
    "org.freedesktop.DBus.ObjectManager" interface.
    
    Note: No signals are sent automatically; they must be sent
    manually.
    """
    @dbus.service.method(dbus.OBJECT_MANAGER_IFACE,
                         out_signature = "a{oa{sa{sv}}}")
    def GetManagedObjects(self):
        """This function must be overridden"""
        raise NotImplementedError()
    
    @dbus.service.signal(dbus.OBJECT_MANAGER_IFACE,
                         signature = "oa{sa{sv}}")
    def InterfacesAdded(self, object_path, interfaces_and_properties):
        pass
    
    @dbus.service.signal(dbus.OBJECT_MANAGER_IFACE, signature = "oas")
    def InterfacesRemoved(self, object_path, interfaces):
        pass
    
    @dbus.service.method(dbus.INTROSPECTABLE_IFACE,
                         out_signature = "s",
                         path_keyword = 'object_path',
                         connection_keyword = 'connection')
    def Introspect(self, object_path, connection):
        """Overloading of standard D-Bus method.
        
        Override return argument name of GetManagedObjects to be
        "objpath_interfaces_and_properties"
        """
        xmlstring = DBusObjectWithAnnotations.Introspect(self,
                                                         object_path,
                                                         connection)
        try:
            document = xml.dom.minidom.parseString(xmlstring)
            
            for if_tag in document.getElementsByTagName("interface"):
                # Fix argument name for the GetManagedObjects method
                if (if_tag.getAttribute("name")
                                == dbus.OBJECT_MANAGER_IFACE):
                    for cn in if_tag.getElementsByTagName("method"):
                        if (cn.getAttribute("name")
                            == "GetManagedObjects"):
                            for arg in cn.getElementsByTagName("arg"):
                                if (arg.getAttribute("direction")
                                    == "out"):
                                    arg.setAttribute(
                                        "name",
                                        "objpath_interfaces"
                                        "_and_properties")
            xmlstring = document.toxml("utf-8")
            document.unlink()
        except (AttributeError, xml.dom.DOMException,
                xml.parsers.expat.ExpatError) as error:
            logger.error("Failed to override Introspection method",
                         exc_info = error)
        return xmlstring

def datetime_to_dbus(dt, variant_level=0):
    """Convert a UTC datetime.datetime() to a D-Bus type."""
    if dt is None:
        return dbus.String("", variant_level = variant_level)
    return dbus.String(dt.isoformat(), variant_level=variant_level)


def alternate_dbus_interfaces(alt_interface_names, deprecate=True):
    """A class decorator; applied to a subclass of
    dbus.service.Object, it will add alternate D-Bus attributes with
    interface names according to the "alt_interface_names" mapping.
    Usage:
    
    @alternate_dbus_interfaces({"org.example.Interface":
                                    "net.example.AlternateInterface"})
    class SampleDBusObject(dbus.service.Object):
        @dbus.service.method("org.example.Interface")
        def SampleDBusMethod():
            pass
    
    The above "SampleDBusMethod" on "SampleDBusObject" will be
    reachable via two interfaces: "org.example.Interface" and
    "net.example.AlternateInterface", the latter of which will have
    its D-Bus annotation "org.freedesktop.DBus.Deprecated" set to
    "true", unless "deprecate" is passed with a False value.
    
    This works for methods and signals, and also for D-Bus properties
    (from DBusObjectWithProperties) and interfaces (from the
    dbus_interface_annotations decorator).
    """
    
    def wrapper(cls):
        for orig_interface_name, alt_interface_name in (
                alt_interface_names.items()):
            attr = {}
            interface_names = set()
            # Go though all attributes of the class
            for attrname, attribute in inspect.getmembers(cls):
                # Ignore non-D-Bus attributes, and D-Bus attributes
                # with the wrong interface name
                if (not hasattr(attribute, "_dbus_interface")
                    or not attribute._dbus_interface.startswith(
                        orig_interface_name)):
                    continue
                # Create an alternate D-Bus interface name based on
                # the current name
                alt_interface = attribute._dbus_interface.replace(
                    orig_interface_name, alt_interface_name)
                interface_names.add(alt_interface)
                # Is this a D-Bus signal?
                if getattr(attribute, "_dbus_is_signal", False):
                    # Extract the original non-method undecorated
                    # function by black magic
                    if sys.version_info.major == 2:
                        nonmethod_func = (dict(
                            zip(attribute.func_code.co_freevars,
                                attribute.__closure__))
                                          ["func"].cell_contents)
                    else:
                        nonmethod_func = (dict(
                            zip(attribute.__code__.co_freevars,
                                attribute.__closure__))
                                          ["func"].cell_contents)
                    # Create a new, but exactly alike, function
                    # object, and decorate it to be a new D-Bus signal
                    # with the alternate D-Bus interface name
                    new_function = copy_function(nonmethod_func)
                    new_function = (dbus.service.signal(
                        alt_interface,
                        attribute._dbus_signature)(new_function))
                    # Copy annotations, if any
                    try:
                        new_function._dbus_annotations = dict(
                            attribute._dbus_annotations)
                    except AttributeError:
                        pass
                    # Define a creator of a function to call both the
                    # original and alternate functions, so both the
                    # original and alternate signals gets sent when
                    # the function is called
                    def fixscope(func1, func2):
                        """This function is a scope container to pass
                        func1 and func2 to the "call_both" function
                        outside of its arguments"""
                        
                        @functools.wraps(func2)
                        def call_both(*args, **kwargs):
                            """This function will emit two D-Bus
                            signals by calling func1 and func2"""
                            func1(*args, **kwargs)
                            func2(*args, **kwargs)
                        # Make wrapper function look like a D-Bus signal
                        for name, attr in inspect.getmembers(func2):
                            if name.startswith("_dbus_"):
                                setattr(call_both, name, attr)
                        
                        return call_both
                    # Create the "call_both" function and add it to
                    # the class
                    attr[attrname] = fixscope(attribute, new_function)
                # Is this a D-Bus method?
                elif getattr(attribute, "_dbus_is_method", False):
                    # Create a new, but exactly alike, function
                    # object.  Decorate it to be a new D-Bus method
                    # with the alternate D-Bus interface name.  Add it
                    # to the class.
                    attr[attrname] = (
                        dbus.service.method(
                            alt_interface,
                            attribute._dbus_in_signature,
                            attribute._dbus_out_signature)
                        (copy_function(attribute)))
                    # Copy annotations, if any
                    try:
                        attr[attrname]._dbus_annotations = dict(
                            attribute._dbus_annotations)
                    except AttributeError:
                        pass
                # Is this a D-Bus property?
                elif getattr(attribute, "_dbus_is_property", False):
                    # Create a new, but exactly alike, function
                    # object, and decorate it to be a new D-Bus
                    # property with the alternate D-Bus interface
                    # name.  Add it to the class.
                    attr[attrname] = (dbus_service_property(
                        alt_interface, attribute._dbus_signature,
                        attribute._dbus_access,
                        attribute._dbus_get_args_options
                        ["byte_arrays"])
                                      (copy_function(attribute)))
                    # Copy annotations, if any
                    try:
                        attr[attrname]._dbus_annotations = dict(
                            attribute._dbus_annotations)
                    except AttributeError:
                        pass
                # Is this a D-Bus interface?
                elif getattr(attribute, "_dbus_is_interface", False):
                    # Create a new, but exactly alike, function
                    # object.  Decorate it to be a new D-Bus interface
                    # with the alternate D-Bus interface name.  Add it
                    # to the class.
                    attr[attrname] = (
                        dbus_interface_annotations(alt_interface)
                        (copy_function(attribute)))
            if deprecate:
                # Deprecate all alternate interfaces
                iname="_AlternateDBusNames_interface_annotation{}"
                for interface_name in interface_names:
                    
                    @dbus_interface_annotations(interface_name)
                    def func(self):
                        return { "org.freedesktop.DBus.Deprecated":
                                 "true" }
                    # Find an unused name
                    for aname in (iname.format(i)
                                  for i in itertools.count()):
                        if aname not in attr:
                            attr[aname] = func
                            break
            if interface_names:
                # Replace the class with a new subclass of it with
                # methods, signals, etc. as created above.
                if sys.version_info.major == 2:
                    cls = type(b"{}Alternate".format(cls.__name__),
                               (cls, ), attr)
                else:
                    cls = type("{}Alternate".format(cls.__name__),
                               (cls, ), attr)
        return cls
    
    return wrapper


@alternate_dbus_interfaces({"se.recompile.Mandos":
                            "se.bsnet.fukt.Mandos"})
class ClientDBus(Client, DBusObjectWithProperties):
    """A Client class using D-Bus
    
    Attributes:
    dbus_object_path: dbus.ObjectPath
    bus: dbus.SystemBus()
    """
    
    runtime_expansions = (Client.runtime_expansions
                          + ("dbus_object_path", ))
    
    _interface = "se.recompile.Mandos.Client"
    
    # dbus.service.Object doesn't use super(), so we can't either.
    
    def __init__(self, bus = None, *args, **kwargs):
        self.bus = bus
        Client.__init__(self, *args, **kwargs)
        # Only now, when this client is initialized, can it show up on
        # the D-Bus
        client_object_name = str(self.name).translate(
            {ord("."): ord("_"),
             ord("-"): ord("_")})
        self.dbus_object_path = dbus.ObjectPath(
            "/clients/" + client_object_name)
        DBusObjectWithProperties.__init__(self, self.bus,
                                          self.dbus_object_path)
    
    def notifychangeproperty(transform_func, dbus_name,
                             type_func=lambda x: x,
                             variant_level=1,
                             invalidate_only=False,
                             _interface=_interface):
        """ Modify a variable so that it's a property which announces
        its changes to DBus.
        
        transform_fun: Function that takes a value and a variant_level
                       and transforms it to a D-Bus type.
        dbus_name: D-Bus name of the variable
        type_func: Function that transform the value before sending it
                   to the D-Bus.  Default: no transform
        variant_level: D-Bus variant level.  Default: 1
        """
        attrname = "_{}".format(dbus_name)
        
        def setter(self, value):
            if hasattr(self, "dbus_object_path"):
                if (not hasattr(self, attrname) or
                    type_func(getattr(self, attrname, None))
                    != type_func(value)):
                    if invalidate_only:
                        self.PropertiesChanged(
                            _interface, dbus.Dictionary(),
                            dbus.Array((dbus_name, )))
                    else:
                        dbus_value = transform_func(
                            type_func(value),
                            variant_level = variant_level)
                        self.PropertyChanged(dbus.String(dbus_name),
                                             dbus_value)
                        self.PropertiesChanged(
                            _interface,
                            dbus.Dictionary({ dbus.String(dbus_name):
                                              dbus_value }),
                            dbus.Array())
            setattr(self, attrname, value)
        
        return property(lambda self: getattr(self, attrname), setter)
    
    expires = notifychangeproperty(datetime_to_dbus, "Expires")
    approvals_pending = notifychangeproperty(dbus.Boolean,
                                             "ApprovalPending",
                                             type_func = bool)
    enabled = notifychangeproperty(dbus.Boolean, "Enabled")
    last_enabled = notifychangeproperty(datetime_to_dbus,
                                        "LastEnabled")
    checker = notifychangeproperty(
        dbus.Boolean, "CheckerRunning",
        type_func = lambda checker: checker is not None)
    last_checked_ok = notifychangeproperty(datetime_to_dbus,
                                           "LastCheckedOK")
    last_checker_status = notifychangeproperty(dbus.Int16,
                                               "LastCheckerStatus")
    last_approval_request = notifychangeproperty(
        datetime_to_dbus, "LastApprovalRequest")
    approved_by_default = notifychangeproperty(dbus.Boolean,
                                               "ApprovedByDefault")
    approval_delay = notifychangeproperty(
        dbus.UInt64, "ApprovalDelay",
        type_func = lambda td: td.total_seconds() * 1000)
    approval_duration = notifychangeproperty(
        dbus.UInt64, "ApprovalDuration",
        type_func = lambda td: td.total_seconds() * 1000)
    host = notifychangeproperty(dbus.String, "Host")
    timeout = notifychangeproperty(
        dbus.UInt64, "Timeout",
        type_func = lambda td: td.total_seconds() * 1000)
    extended_timeout = notifychangeproperty(
        dbus.UInt64, "ExtendedTimeout",
        type_func = lambda td: td.total_seconds() * 1000)
    interval = notifychangeproperty(
        dbus.UInt64, "Interval",
        type_func = lambda td: td.total_seconds() * 1000)
    checker_command = notifychangeproperty(dbus.String, "Checker")
    secret = notifychangeproperty(dbus.ByteArray, "Secret",
                                  invalidate_only=True)
    
    del notifychangeproperty
    
    def __del__(self, *args, **kwargs):
        try:
            self.remove_from_connection()
        except LookupError:
            pass
        if hasattr(DBusObjectWithProperties, "__del__"):
            DBusObjectWithProperties.__del__(self, *args, **kwargs)
        Client.__del__(self, *args, **kwargs)
    
    def checker_callback(self, source, condition,
                         connection, command, *args, **kwargs):
        ret = Client.checker_callback(self, source, condition,
                                      connection, command, *args,
                                      **kwargs)
        exitstatus = self.last_checker_status
        if exitstatus >= 0:
            # Emit D-Bus signal
            self.CheckerCompleted(dbus.Int16(exitstatus),
                                  # This is specific to GNU libC
                                  dbus.Int64(exitstatus << 8),
                                  dbus.String(command))
        else:
            # Emit D-Bus signal
            self.CheckerCompleted(dbus.Int16(-1),
                                  dbus.Int64(
                                      # This is specific to GNU libC
                                      (exitstatus << 8)
                                      | self.last_checker_signal),
                                  dbus.String(command))
        return ret
    
    def start_checker(self, *args, **kwargs):
        old_checker_pid = getattr(self.checker, "pid", None)
        r = Client.start_checker(self, *args, **kwargs)
        # Only if new checker process was started
        if (self.checker is not None
            and old_checker_pid != self.checker.pid):
            # Emit D-Bus signal
            self.CheckerStarted(self.current_checker_command)
        return r
    
    def _reset_approved(self):
        self.approved = None
        return False
    
    def approve(self, value=True):
        self.approved = value
        GLib.timeout_add(int(self.approval_duration.total_seconds()
                             * 1000), self._reset_approved)
        self.send_changedstate()
    
    ## D-Bus methods, signals & properties
    
    ## Interfaces
    
    ## Signals
    
    # CheckerCompleted - signal
    @dbus.service.signal(_interface, signature="nxs")
    def CheckerCompleted(self, exitcode, waitstatus, command):
        "D-Bus signal"
        pass
    
    # CheckerStarted - signal
    @dbus.service.signal(_interface, signature="s")
    def CheckerStarted(self, command):
        "D-Bus signal"
        pass
    
    # PropertyChanged - signal
    @dbus_annotations({"org.freedesktop.DBus.Deprecated": "true"})
    @dbus.service.signal(_interface, signature="sv")
    def PropertyChanged(self, property, value):
        "D-Bus signal"
        pass
    
    # GotSecret - signal
    @dbus.service.signal(_interface)
    def GotSecret(self):
        """D-Bus signal
        Is sent after a successful transfer of secret from the Mandos
        server to mandos-client
        """
        pass
    
    # Rejected - signal
    @dbus.service.signal(_interface, signature="s")
    def Rejected(self, reason):
        "D-Bus signal"
        pass
    
    # NeedApproval - signal
    @dbus.service.signal(_interface, signature="tb")
    def NeedApproval(self, timeout, default):
        "D-Bus signal"
        return self.need_approval()
    
    ## Methods
    
    # Approve - method
    @dbus.service.method(_interface, in_signature="b")
    def Approve(self, value):
        self.approve(value)
    
    # CheckedOK - method
    @dbus.service.method(_interface)
    def CheckedOK(self):
        self.checked_ok()
    
    # Enable - method
    @dbus_annotations({"org.freedesktop.DBus.Deprecated": "true"})
    @dbus.service.method(_interface)
    def Enable(self):
        "D-Bus method"
        self.enable()
    
    # StartChecker - method
    @dbus_annotations({"org.freedesktop.DBus.Deprecated": "true"})
    @dbus.service.method(_interface)
    def StartChecker(self):
        "D-Bus method"
        self.start_checker()
    
    # Disable - method
    @dbus_annotations({"org.freedesktop.DBus.Deprecated": "true"})
    @dbus.service.method(_interface)
    def Disable(self):
        "D-Bus method"
        self.disable()
    
    # StopChecker - method
    @dbus_annotations({"org.freedesktop.DBus.Deprecated": "true"})
    @dbus.service.method(_interface)
    def StopChecker(self):
        self.stop_checker()
    
    ## Properties
    
    # ApprovalPending - property
    @dbus_service_property(_interface, signature="b", access="read")
    def ApprovalPending_dbus_property(self):
        return dbus.Boolean(bool(self.approvals_pending))
    
    # ApprovedByDefault - property
    @dbus_service_property(_interface,
                           signature="b",
                           access="readwrite")
    def ApprovedByDefault_dbus_property(self, value=None):
        if value is None:       # get
            return dbus.Boolean(self.approved_by_default)
        self.approved_by_default = bool(value)
    
    # ApprovalDelay - property
    @dbus_service_property(_interface,
                           signature="t",
                           access="readwrite")
    def ApprovalDelay_dbus_property(self, value=None):
        if value is None:       # get
            return dbus.UInt64(self.approval_delay.total_seconds()
                               * 1000)
        self.approval_delay = datetime.timedelta(0, 0, 0, value)
    
    # ApprovalDuration - property
    @dbus_service_property(_interface,
                           signature="t",
                           access="readwrite")
    def ApprovalDuration_dbus_property(self, value=None):
        if value is None:       # get
            return dbus.UInt64(self.approval_duration.total_seconds()
                               * 1000)
        self.approval_duration = datetime.timedelta(0, 0, 0, value)
    
    # Name - property
    @dbus_annotations(
        {"org.freedesktop.DBus.Property.EmitsChangedSignal": "const"})
    @dbus_service_property(_interface, signature="s", access="read")
    def Name_dbus_property(self):
        return dbus.String(self.name)
    
    # Fingerprint - property
    @dbus_annotations(
        {"org.freedesktop.DBus.Property.EmitsChangedSignal": "const"})
    @dbus_service_property(_interface, signature="s", access="read")
    def Fingerprint_dbus_property(self):
        return dbus.String(self.fingerprint)
    
    # Host - property
    @dbus_service_property(_interface,
                           signature="s",
                           access="readwrite")
    def Host_dbus_property(self, value=None):
        if value is None:       # get
            return dbus.String(self.host)
        self.host = str(value)
    
    # Created - property
    @dbus_annotations(
        {"org.freedesktop.DBus.Property.EmitsChangedSignal": "const"})
    @dbus_service_property(_interface, signature="s", access="read")
    def Created_dbus_property(self):
        return datetime_to_dbus(self.created)
    
    # LastEnabled - property
    @dbus_service_property(_interface, signature="s", access="read")
    def LastEnabled_dbus_property(self):
        return datetime_to_dbus(self.last_enabled)
    
    # Enabled - property
    @dbus_service_property(_interface,
                           signature="b",
                           access="readwrite")
    def Enabled_dbus_property(self, value=None):
        if value is None:       # get
            return dbus.Boolean(self.enabled)
        if value:
            self.enable()
        else:
            self.disable()
    
    # LastCheckedOK - property
    @dbus_service_property(_interface,
                           signature="s",
                           access="readwrite")
    def LastCheckedOK_dbus_property(self, value=None):
        if value is not None:
            self.checked_ok()
            return
        return datetime_to_dbus(self.last_checked_ok)
    
    # LastCheckerStatus - property
    @dbus_service_property(_interface, signature="n", access="read")
    def LastCheckerStatus_dbus_property(self):
        return dbus.Int16(self.last_checker_status)
    
    # Expires - property
    @dbus_service_property(_interface, signature="s", access="read")
    def Expires_dbus_property(self):
        return datetime_to_dbus(self.expires)
    
    # LastApprovalRequest - property
    @dbus_service_property(_interface, signature="s", access="read")
    def LastApprovalRequest_dbus_property(self):
        return datetime_to_dbus(self.last_approval_request)
    
    # Timeout - property
    @dbus_service_property(_interface,
                           signature="t",
                           access="readwrite")
    def Timeout_dbus_property(self, value=None):
        if value is None:       # get
            return dbus.UInt64(self.timeout.total_seconds() * 1000)
        old_timeout = self.timeout
        self.timeout = datetime.timedelta(0, 0, 0, value)
        # Reschedule disabling
        if self.enabled:
            now = datetime.datetime.utcnow()
            self.expires += self.timeout - old_timeout
            if self.expires <= now:
                # The timeout has passed
                self.disable()
            else:
                if (getattr(self, "disable_initiator_tag", None)
                    is None):
                    return
                GLib.source_remove(self.disable_initiator_tag)
                self.disable_initiator_tag = GLib.timeout_add(
                    int((self.expires - now).total_seconds() * 1000),
                    self.disable)
    
    # ExtendedTimeout - property
    @dbus_service_property(_interface,
                           signature="t",
                           access="readwrite")
    def ExtendedTimeout_dbus_property(self, value=None):
        if value is None:       # get
            return dbus.UInt64(self.extended_timeout.total_seconds()
                               * 1000)
        self.extended_timeout = datetime.timedelta(0, 0, 0, value)
    
    # Interval - property
    @dbus_service_property(_interface,
                           signature="t",
                           access="readwrite")
    def Interval_dbus_property(self, value=None):
        if value is None:       # get
            return dbus.UInt64(self.interval.total_seconds() * 1000)
        self.interval = datetime.timedelta(0, 0, 0, value)
        if getattr(self, "checker_initiator_tag", None) is None:
            return
        if self.enabled:
            # Reschedule checker run
            GLib.source_remove(self.checker_initiator_tag)
            self.checker_initiator_tag = GLib.timeout_add(
                value, self.start_checker)
            self.start_checker() # Start one now, too
    
    # Checker - property
    @dbus_service_property(_interface,
                           signature="s",
                           access="readwrite")
    def Checker_dbus_property(self, value=None):
        if value is None:       # get
            return dbus.String(self.checker_command)
        self.checker_command = str(value)
    
    # CheckerRunning - property
    @dbus_service_property(_interface,
                           signature="b",
                           access="readwrite")
    def CheckerRunning_dbus_property(self, value=None):
        if value is None:       # get
            return dbus.Boolean(self.checker is not None)
        if value:
            self.start_checker()
        else:
            self.stop_checker()
    
    # ObjectPath - property
    @dbus_annotations(
        {"org.freedesktop.DBus.Property.EmitsChangedSignal": "const",
         "org.freedesktop.DBus.Deprecated": "true"})
    @dbus_service_property(_interface, signature="o", access="read")
    def ObjectPath_dbus_property(self):
        return self.dbus_object_path # is already a dbus.ObjectPath
    
    # Secret = property
    @dbus_annotations(
        {"org.freedesktop.DBus.Property.EmitsChangedSignal":
         "invalidates"})
    @dbus_service_property(_interface,
                           signature="ay",
                           access="write",
                           byte_arrays=True)
    def Secret_dbus_property(self, value):
        self.secret = bytes(value)
    
    del _interface


class ProxyClient(object):
    def __init__(self, child_pipe, fpr, address):
        self._pipe = child_pipe
        self._pipe.send(('init', fpr, address))
        if not self._pipe.recv():
            raise KeyError(fpr)
    
    def __getattribute__(self, name):
        if name == '_pipe':
            return super(ProxyClient, self).__getattribute__(name)
        self._pipe.send(('getattr', name))
        data = self._pipe.recv()
        if data[0] == 'data':
            return data[1]
        if data[0] == 'function':
            
            def func(*args, **kwargs):
                self._pipe.send(('funcall', name, args, kwargs))
                return self._pipe.recv()[1]
            
            return func
    
    def __setattr__(self, name, value):
        if name == '_pipe':
            return super(ProxyClient, self).__setattr__(name, value)
        self._pipe.send(('setattr', name, value))


class ClientHandler(socketserver.BaseRequestHandler, object):
    """A class to handle client connections.
    
    Instantiated once for each connection to handle it.
    Note: This will run in its own forked process."""
    
    def handle(self):
        with contextlib.closing(self.server.child_pipe) as child_pipe:
            logger.info("TCP connection from: %s",
                        str(self.client_address))
            logger.debug("Pipe FD: %d",
                         self.server.child_pipe.fileno())
            
            session = gnutls.ClientSession(self.request)
            
            #priority = ':'.join(("NONE", "+VERS-TLS1.1",
            #                      "+AES-256-CBC", "+SHA1",
            #                      "+COMP-NULL", "+CTYPE-OPENPGP",
            #                      "+DHE-DSS"))
            # Use a fallback default, since this MUST be set.
            priority = self.server.gnutls_priority
            if priority is None:
                priority = "NORMAL"
            gnutls.priority_set_direct(session._c_object, priority,
                                       None)
            
            # Start communication using the Mandos protocol
            # Get protocol number
            line = self.request.makefile().readline()
            logger.debug("Protocol version: %r", line)
            try:
                if int(line.strip().split()[0]) > 1:
                    raise RuntimeError(line)
            except (ValueError, IndexError, RuntimeError) as error:
                logger.error("Unknown protocol version: %s", error)
                return
            
            # Start GnuTLS connection
            try:
                session.handshake()
            except gnutls.Error as error:
                logger.warning("Handshake failed: %s", error)
                # Do not run session.bye() here: the session is not
                # established.  Just abandon the request.
                return
            logger.debug("Handshake succeeded")
            
            approval_required = False
            try:
                try:
                    fpr = self.fingerprint(
                        self.peer_certificate(session))
                except (TypeError, gnutls.Error) as error:
                    logger.warning("Bad certificate: %s", error)
                    return
                logger.debug("Fingerprint: %s", fpr)
                
                try:
                    client = ProxyClient(child_pipe, fpr,
                                         self.client_address)
                except KeyError:
                    return
                
                if client.approval_delay:
                    delay = client.approval_delay
                    client.approvals_pending += 1
                    approval_required = True
                
                while True:
                    if not client.enabled:
                        logger.info("Client %s is disabled",
                                    client.name)
                        if self.server.use_dbus:
                            # Emit D-Bus signal
                            client.Rejected("Disabled")
                        return
                    
                    if client.approved or not client.approval_delay:
                        #We are approved or approval is disabled
                        break
                    elif client.approved is None:
                        logger.info("Client %s needs approval",
                                    client.name)
                        if self.server.use_dbus:
                            # Emit D-Bus signal
                            client.NeedApproval(
                                client.approval_delay.total_seconds()
                                * 1000, client.approved_by_default)
                    else:
                        logger.warning("Client %s was not approved",
                                       client.name)
                        if self.server.use_dbus:
                            # Emit D-Bus signal
                            client.Rejected("Denied")
                        return
                    
                    #wait until timeout or approved
                    time = datetime.datetime.now()
                    client.changedstate.acquire()
                    client.changedstate.wait(delay.total_seconds())
                    client.changedstate.release()
                    time2 = datetime.datetime.now()
                    if (time2 - time) >= delay:
                        if not client.approved_by_default:
                            logger.warning("Client %s timed out while"
                                           " waiting for approval",
                                           client.name)
                            if self.server.use_dbus:
                                # Emit D-Bus signal
                                client.Rejected("Approval timed out")
                            return
                        else:
                            break
                    else:
                        delay -= time2 - time
                
                try:
                    session.send(client.secret)
                except gnutls.Error as error:
                    logger.warning("gnutls send failed",
                                   exc_info = error)
                    return
                
                logger.info("Sending secret to %s", client.name)
                # bump the timeout using extended_timeout
                client.bump_timeout(client.extended_timeout)
                if self.server.use_dbus:
                    # Emit D-Bus signal
                    client.GotSecret()
            
            finally:
                if approval_required:
                    client.approvals_pending -= 1
                try:
                    session.bye()
                except gnutls.Error as error:
                    logger.warning("GnuTLS bye failed",
                                   exc_info=error)
    
    @staticmethod
    def peer_certificate(session):
        "Return the peer's OpenPGP certificate as a bytestring"
        # If not an OpenPGP certificate...
        if (gnutls.certificate_type_get(session._c_object)
            != gnutls.CRT_OPENPGP):
            # ...return invalid data
            return b""
        list_size = ctypes.c_uint(1)
        cert_list = (gnutls.certificate_get_peers
                     (session._c_object, ctypes.byref(list_size)))
        if not bool(cert_list) and list_size.value != 0:
            raise gnutls.Error("error getting peer certificate")
        if list_size.value == 0:
            return None
        cert = cert_list[0]
        return ctypes.string_at(cert.data, cert.size)
    
    @staticmethod
    def fingerprint(openpgp):
        "Convert an OpenPGP bytestring to a hexdigit fingerprint"
        # New GnuTLS "datum" with the OpenPGP public key
        datum = gnutls.datum_t(
            ctypes.cast(ctypes.c_char_p(openpgp),
                        ctypes.POINTER(ctypes.c_ubyte)),
            ctypes.c_uint(len(openpgp)))
        # New empty GnuTLS certificate
        crt = gnutls.openpgp_crt_t()
        gnutls.openpgp_crt_init(ctypes.byref(crt))
        # Import the OpenPGP public key into the certificate
        gnutls.openpgp_crt_import(crt, ctypes.byref(datum),
                                  gnutls.OPENPGP_FMT_RAW)
        # Verify the self signature in the key
        crtverify = ctypes.c_uint()
        gnutls.openpgp_crt_verify_self(crt, 0,
                                       ctypes.byref(crtverify))
        if crtverify.value != 0:
            gnutls.openpgp_crt_deinit(crt)
            raise gnutls.CertificateSecurityError("Verify failed")
        # New buffer for the fingerprint
        buf = ctypes.create_string_buffer(20)
        buf_len = ctypes.c_size_t()
        # Get the fingerprint from the certificate into the buffer
        gnutls.openpgp_crt_get_fingerprint(crt, ctypes.byref(buf),
                                           ctypes.byref(buf_len))
        # Deinit the certificate
        gnutls.openpgp_crt_deinit(crt)
        # Convert the buffer to a Python bytestring
        fpr = ctypes.string_at(buf, buf_len.value)
        # Convert the bytestring to hexadecimal notation
        hex_fpr = binascii.hexlify(fpr).upper()
        return hex_fpr


class MultiprocessingMixIn(object):
    """Like socketserver.ThreadingMixIn, but with multiprocessing"""
    
    def sub_process_main(self, request, address):
        try:
            self.finish_request(request, address)
        except Exception:
            self.handle_error(request, address)
        self.close_request(request)
    
    def process_request(self, request, address):
        """Start a new process to process the request."""
        proc = multiprocessing.Process(target = self.sub_process_main,
                                       args = (request, address))
        proc.start()
        return proc


class MultiprocessingMixInWithPipe(MultiprocessingMixIn, object):
    """ adds a pipe to the MixIn """
    
    def process_request(self, request, client_address):
        """Overrides and wraps the original process_request().
        
        This function creates a new pipe in self.pipe
        """
        parent_pipe, self.child_pipe = multiprocessing.Pipe()
        
        proc = MultiprocessingMixIn.process_request(self, request,
                                                    client_address)
        self.child_pipe.close()
        self.add_pipe(parent_pipe, proc)
    
    def add_pipe(self, parent_pipe, proc):
        """Dummy function; override as necessary"""
        raise NotImplementedError()


class IPv6_TCPServer(MultiprocessingMixInWithPipe,
                     socketserver.TCPServer, object):
    """IPv6-capable TCP server.  Accepts 'None' as address and/or port
    
    Attributes:
        enabled:        Boolean; whether this server is activated yet
        interface:      None or a network interface name (string)
        use_ipv6:       Boolean; to use IPv6 or not
    """
    
    def __init__(self, server_address, RequestHandlerClass,
                 interface=None,
                 use_ipv6=True,
                 socketfd=None):
        """If socketfd is set, use that file descriptor instead of
        creating a new one with socket.socket().
        """
        self.interface = interface
        if use_ipv6:
            self.address_family = socket.AF_INET6
        if socketfd is not None:
            # Save the file descriptor
            self.socketfd = socketfd
            # Save the original socket.socket() function
            self.socket_socket = socket.socket
            # To implement --socket, we monkey patch socket.socket.
            # 
            # (When socketserver.TCPServer is a new-style class, we
            # could make self.socket into a property instead of monkey
            # patching socket.socket.)
            # 
            # Create a one-time-only replacement for socket.socket()
            @functools.wraps(socket.socket)
            def socket_wrapper(*args, **kwargs):
                # Restore original function so subsequent calls are
                # not affected.
                socket.socket = self.socket_socket
                del self.socket_socket
                # This time only, return a new socket object from the
                # saved file descriptor.
                return socket.fromfd(self.socketfd, *args, **kwargs)
            # Replace socket.socket() function with wrapper
            socket.socket = socket_wrapper
        # The socketserver.TCPServer.__init__ will call
        # socket.socket(), which might be our replacement,
        # socket_wrapper(), if socketfd was set.
        socketserver.TCPServer.__init__(self, server_address,
                                        RequestHandlerClass)
    
    def server_bind(self):
        """This overrides the normal server_bind() function
        to bind to an interface if one was specified, and also NOT to
        bind to an address or port if they were not specified."""
        if self.interface is not None:
            if SO_BINDTODEVICE is None:
                logger.error("SO_BINDTODEVICE does not exist;"
                             " cannot bind to interface %s",
                             self.interface)
            else:
                try:
                    self.socket.setsockopt(
                        socket.SOL_SOCKET, SO_BINDTODEVICE,
                        (self.interface + "\0").encode("utf-8"))
                except socket.error as error:
                    if error.errno == errno.EPERM:
                        logger.error("No permission to bind to"
                                     " interface %s", self.interface)
                    elif error.errno == errno.ENOPROTOOPT:
                        logger.error("SO_BINDTODEVICE not available;"
                                     " cannot bind to interface %s",
                                     self.interface)
                    elif error.errno == errno.ENODEV:
                        logger.error("Interface %s does not exist,"
                                     " cannot bind", self.interface)
                    else:
                        raise
        # Only bind(2) the socket if we really need to.
        if self.server_address[0] or self.server_address[1]:
            if not self.server_address[0]:
                if self.address_family == socket.AF_INET6:
                    any_address = "::" # in6addr_any
                else:
                    any_address = "0.0.0.0" # INADDR_ANY
                self.server_address = (any_address,
                                       self.server_address[1])
            elif not self.server_address[1]:
                self.server_address = (self.server_address[0], 0)
#                 if self.interface:
#                     self.server_address = (self.server_address[0],
#                                            0, # port
#                                            0, # flowinfo
#                                            if_nametoindex
#                                            (self.interface))
            return socketserver.TCPServer.server_bind(self)


class MandosServer(IPv6_TCPServer):
    """Mandos server.
    
    Attributes:
        clients:        set of Client objects
        gnutls_priority GnuTLS priority string
        use_dbus:       Boolean; to emit D-Bus signals or not
    
    Assumes a GLib.MainLoop event loop.
    """
    
    def __init__(self, server_address, RequestHandlerClass,
                 interface=None,
                 use_ipv6=True,
                 clients=None,
                 gnutls_priority=None,
                 use_dbus=True,
                 socketfd=None):
        self.enabled = False
        self.clients = clients
        if self.clients is None:
            self.clients = {}
        self.use_dbus = use_dbus
        self.gnutls_priority = gnutls_priority
        IPv6_TCPServer.__init__(self, server_address,
                                RequestHandlerClass,
                                interface = interface,
                                use_ipv6 = use_ipv6,
                                socketfd = socketfd)
    
    def server_activate(self):
        if self.enabled:
            return socketserver.TCPServer.server_activate(self)
    
    def enable(self):
        self.enabled = True
    
    def add_pipe(self, parent_pipe, proc):
        # Call "handle_ipc" for both data and EOF events
        GLib.io_add_watch(
            parent_pipe.fileno(),
            GLib.IO_IN | GLib.IO_HUP,
            functools.partial(self.handle_ipc,
                              parent_pipe = parent_pipe,
                              proc = proc))
    
    def handle_ipc(self, source, condition,
                   parent_pipe=None,
                   proc = None,
                   client_object=None):
        # error, or the other end of multiprocessing.Pipe has closed
        if condition & (GLib.IO_ERR | GLib.IO_HUP):
            # Wait for other process to exit
            proc.join()
            return False
        
        # Read a request from the child
        request = parent_pipe.recv()
        command = request[0]
        
        if command == 'init':
            fpr = request[1]
            address = request[2]
            
            for c in self.clients.values():
                if c.fingerprint == fpr:
                    client = c
                    break
            else:
                logger.info("Client not found for fingerprint: %s, ad"
                            "dress: %s", fpr, address)
                if self.use_dbus:
                    # Emit D-Bus signal
                    mandos_dbus_service.ClientNotFound(fpr,
                                                       address[0])
                parent_pipe.send(False)
                return False
            
            GLib.io_add_watch(
                parent_pipe.fileno(),
                GLib.IO_IN | GLib.IO_HUP,
                functools.partial(self.handle_ipc,
                                  parent_pipe = parent_pipe,
                                  proc = proc,
                                  client_object = client))
            parent_pipe.send(True)
            # remove the old hook in favor of the new above hook on
            # same fileno
            return False
        if command == 'funcall':
            funcname = request[1]
            args = request[2]
            kwargs = request[3]
            
            parent_pipe.send(('data', getattr(client_object,
                                              funcname)(*args,
                                                        **kwargs)))
        
        if command == 'getattr':
            attrname = request[1]
            if isinstance(client_object.__getattribute__(attrname),
                          collections.Callable):
                parent_pipe.send(('function', ))
            else:
                parent_pipe.send((
                    'data', client_object.__getattribute__(attrname)))
        
        if command == 'setattr':
            attrname = request[1]
            value = request[2]
            setattr(client_object, attrname, value)
        
        return True


def rfc3339_duration_to_delta(duration):
    """Parse an RFC 3339 "duration" and return a datetime.timedelta
    
    >>> rfc3339_duration_to_delta("P7D")
    datetime.timedelta(7)
    >>> rfc3339_duration_to_delta("PT60S")
    datetime.timedelta(0, 60)
    >>> rfc3339_duration_to_delta("PT60M")
    datetime.timedelta(0, 3600)
    >>> rfc3339_duration_to_delta("PT24H")
    datetime.timedelta(1)
    >>> rfc3339_duration_to_delta("P1W")
    datetime.timedelta(7)
    >>> rfc3339_duration_to_delta("PT5M30S")
    datetime.timedelta(0, 330)
    >>> rfc3339_duration_to_delta("P1DT3M20S")
    datetime.timedelta(1, 200)
    """
    
    # Parsing an RFC 3339 duration with regular expressions is not
    # possible - there would have to be multiple places for the same
    # values, like seconds.  The current code, while more esoteric, is
    # cleaner without depending on a parsing library.  If Python had a
    # built-in library for parsing we would use it, but we'd like to
    # avoid excessive use of external libraries.
    
    # New type for defining tokens, syntax, and semantics all-in-one
    Token = collections.namedtuple("Token", (
        "regexp",  # To match token; if "value" is not None, must have
                   # a "group" containing digits
        "value",   # datetime.timedelta or None
        "followers"))           # Tokens valid after this token
    # RFC 3339 "duration" tokens, syntax, and semantics; taken from
    # the "duration" ABNF definition in RFC 3339, Appendix A.
    token_end = Token(re.compile(r"$"), None, frozenset())
    token_second = Token(re.compile(r"(\d+)S"),
                         datetime.timedelta(seconds=1),
                         frozenset((token_end, )))
    token_minute = Token(re.compile(r"(\d+)M"),
                         datetime.timedelta(minutes=1),
                         frozenset((token_second, token_end)))
    token_hour = Token(re.compile(r"(\d+)H"),
                       datetime.timedelta(hours=1),
                       frozenset((token_minute, token_end)))
    token_time = Token(re.compile(r"T"),
                       None,
                       frozenset((token_hour, token_minute,
                                  token_second)))
    token_day = Token(re.compile(r"(\d+)D"),
                      datetime.timedelta(days=1),
                      frozenset((token_time, token_end)))
    token_month = Token(re.compile(r"(\d+)M"),
                        datetime.timedelta(weeks=4),
                        frozenset((token_day, token_end)))
    token_year = Token(re.compile(r"(\d+)Y"),
                       datetime.timedelta(weeks=52),
                       frozenset((token_month, token_end)))
    token_week = Token(re.compile(r"(\d+)W"),
                       datetime.timedelta(weeks=1),
                       frozenset((token_end, )))
    token_duration = Token(re.compile(r"P"), None,
                           frozenset((token_year, token_month,
                                      token_day, token_time,
                                      token_week)))
    # Define starting values
    value = datetime.timedelta() # Value so far
    found_token = None
    followers = frozenset((token_duration, )) # Following valid tokens
    s = duration                # String left to parse
    # Loop until end token is found
    while found_token is not token_end:
        # Search for any currently valid tokens
        for token in followers:
            match = token.regexp.match(s)
            if match is not None:
                # Token found
                if token.value is not None:
                    # Value found, parse digits
                    factor = int(match.group(1), 10)
                    # Add to value so far
                    value += factor * token.value
                # Strip token from string
                s = token.regexp.sub("", s, 1)
                # Go to found token
                found_token = token
                # Set valid next tokens
                followers = found_token.followers
                break
        else:
            # No currently valid tokens were found
            raise ValueError("Invalid RFC 3339 duration: {!r}"
                             .format(duration))
    # End token found
    return value


def string_to_delta(interval):
    """Parse a string and return a datetime.timedelta
    
    >>> string_to_delta('7d')
    datetime.timedelta(7)
    >>> string_to_delta('60s')
    datetime.timedelta(0, 60)
    >>> string_to_delta('60m')
    datetime.timedelta(0, 3600)
    >>> string_to_delta('24h')
    datetime.timedelta(1)
    >>> string_to_delta('1w')
    datetime.timedelta(7)
    >>> string_to_delta('5m 30s')
    datetime.timedelta(0, 330)
    """
    
    try:
        return rfc3339_duration_to_delta(interval)
    except ValueError:
        pass
    
    timevalue = datetime.timedelta(0)
    for s in interval.split():
        try:
            suffix = s[-1]
            value = int(s[:-1])
            if suffix == "d":
                delta = datetime.timedelta(value)
            elif suffix == "s":
                delta = datetime.timedelta(0, value)
            elif suffix == "m":
                delta = datetime.timedelta(0, 0, 0, 0, value)
            elif suffix == "h":
                delta = datetime.timedelta(0, 0, 0, 0, 0, value)
            elif suffix == "w":
                delta = datetime.timedelta(0, 0, 0, 0, 0, 0, value)
            else:
                raise ValueError("Unknown suffix {!r}".format(suffix))
        except IndexError as e:
            raise ValueError(*(e.args))
        timevalue += delta
    return timevalue


def daemon(nochdir = False, noclose = False):
    """See daemon(3).  Standard BSD Unix function.
    
    This should really exist as os.daemon, but it doesn't (yet)."""
    if os.fork():
        sys.exit()
    os.setsid()
    if not nochdir:
        os.chdir("/")
    if os.fork():
        sys.exit()
    if not noclose:
        # Close all standard open file descriptors
        null = os.open(os.devnull, os.O_NOCTTY | os.O_RDWR)
        if not stat.S_ISCHR(os.fstat(null).st_mode):
            raise OSError(errno.ENODEV,
                          "{} not a character device"
                          .format(os.devnull))
        os.dup2(null, sys.stdin.fileno())
        os.dup2(null, sys.stdout.fileno())
        os.dup2(null, sys.stderr.fileno())
        if null > 2:
            os.close(null)


def main():
    
    ##################################################################
    # Parsing of options, both command line and config file
    
    parser = argparse.ArgumentParser()
    parser.add_argument("-v", "--version", action="version",
                        version = "%(prog)s {}".format(version),
                        help="show version number and exit")
    parser.add_argument("-i", "--interface", metavar="IF",
                        help="Bind to interface IF")
    parser.add_argument("-a", "--address",
                        help="Address to listen for requests on")
    parser.add_argument("-p", "--port", type=int,
                        help="Port number to receive requests on")
    parser.add_argument("--check", action="store_true",
                        help="Run self-test")
    parser.add_argument("--debug", action="store_true",
                        help="Debug mode; run in foreground and log"
                        " to terminal", default=None)
    parser.add_argument("--debuglevel", metavar="LEVEL",
                        help="Debug level for stdout output")
    parser.add_argument("--priority", help="GnuTLS"
                        " priority string (see GnuTLS documentation)")
    parser.add_argument("--servicename",
                        metavar="NAME", help="Zeroconf service name")
    parser.add_argument("--configdir",
                        default="/etc/mandos", metavar="DIR",
                        help="Directory to search for configuration"
                        " files")
    parser.add_argument("--no-dbus", action="store_false",
                        dest="use_dbus", help="Do not provide D-Bus"
                        " system bus interface", default=None)
    parser.add_argument("--no-ipv6", action="store_false",
                        dest="use_ipv6", help="Do not use IPv6",
                        default=None)
    parser.add_argument("--no-restore", action="store_false",
                        dest="restore", help="Do not restore stored"
                        " state", default=None)
    parser.add_argument("--socket", type=int,
                        help="Specify a file descriptor to a network"
                        " socket to use instead of creating one")
    parser.add_argument("--statedir", metavar="DIR",
                        help="Directory to save/restore state in")
    parser.add_argument("--foreground", action="store_true",
                        help="Run in foreground", default=None)
    parser.add_argument("--no-zeroconf", action="store_false",
                        dest="zeroconf", help="Do not use Zeroconf",
                        default=None)
    
    options = parser.parse_args()
    
    if options.check:
        import doctest
        fail_count, test_count = doctest.testmod()
        sys.exit(os.EX_OK if fail_count == 0 else 1)
    
    # Default values for config file for server-global settings
    server_defaults = { "interface": "",
                        "address": "",
                        "port": "",
                        "debug": "False",
                        "priority":
                        "SECURE256:!CTYPE-X.509:+CTYPE-OPENPGP:!RSA"
                        ":+SIGN-DSA-SHA256",
                        "servicename": "Mandos",
                        "use_dbus": "True",
                        "use_ipv6": "True",
                        "debuglevel": "",
                        "restore": "True",
                        "socket": "",
                        "statedir": "/var/lib/mandos",
                        "foreground": "False",
                        "zeroconf": "True",
                    }
    
    # Parse config file for server-global settings
    server_config = configparser.SafeConfigParser(server_defaults)
    del server_defaults
    server_config.read(os.path.join(options.configdir, "mandos.conf"))
    # Convert the SafeConfigParser object to a dict
    server_settings = server_config.defaults()
    # Use the appropriate methods on the non-string config options
    for option in ("debug", "use_dbus", "use_ipv6", "foreground"):
        server_settings[option] = server_config.getboolean("DEFAULT",
                                                           option)
    if server_settings["port"]:
        server_settings["port"] = server_config.getint("DEFAULT",
                                                       "port")
    if server_settings["socket"]:
        server_settings["socket"] = server_config.getint("DEFAULT",
                                                         "socket")
        # Later, stdin will, and stdout and stderr might, be dup'ed
        # over with an opened os.devnull.  But we don't want this to
        # happen with a supplied network socket.
        if 0 <= server_settings["socket"] <= 2:
            server_settings["socket"] = os.dup(server_settings
                                               ["socket"])
    del server_config
    
    # Override the settings from the config file with command line
    # options, if set.
    for option in ("interface", "address", "port", "debug",
                   "priority", "servicename", "configdir", "use_dbus",
                   "use_ipv6", "debuglevel", "restore", "statedir",
                   "socket", "foreground", "zeroconf"):
        value = getattr(options, option)
        if value is not None:
            server_settings[option] = value
    del options
    # Force all strings to be unicode
    for option in server_settings.keys():
        if isinstance(server_settings[option], bytes):
            server_settings[option] = (server_settings[option]
                                       .decode("utf-8"))
    # Force all boolean options to be boolean
    for option in ("debug", "use_dbus", "use_ipv6", "restore",
                   "foreground", "zeroconf"):
        server_settings[option] = bool(server_settings[option])
    # Debug implies foreground
    if server_settings["debug"]:
        server_settings["foreground"] = True
    # Now we have our good server settings in "server_settings"
    
    ##################################################################
    
    if (not server_settings["zeroconf"]
        and not (server_settings["port"]
                 or server_settings["socket"] != "")):
        parser.error("Needs port or socket to work without Zeroconf")
    
    # For convenience
    debug = server_settings["debug"]
    debuglevel = server_settings["debuglevel"]
    use_dbus = server_settings["use_dbus"]
    use_ipv6 = server_settings["use_ipv6"]
    stored_state_path = os.path.join(server_settings["statedir"],
                                     stored_state_file)
    foreground = server_settings["foreground"]
    zeroconf = server_settings["zeroconf"]
    
    if debug:
        initlogger(debug, logging.DEBUG)
    else:
        if not debuglevel:
            initlogger(debug)
        else:
            level = getattr(logging, debuglevel.upper())
            initlogger(debug, level)
    
    if server_settings["servicename"] != "Mandos":
        syslogger.setFormatter(
            logging.Formatter('Mandos ({}) [%(process)d]:'
                              ' %(levelname)s: %(message)s'.format(
                                  server_settings["servicename"])))
    
    # Parse config file with clients
    client_config = configparser.SafeConfigParser(Client
                                                  .client_defaults)
    client_config.read(os.path.join(server_settings["configdir"],
                                    "clients.conf"))
    
    global mandos_dbus_service
    mandos_dbus_service = None
    
    socketfd = None
    if server_settings["socket"] != "":
        socketfd = server_settings["socket"]
    tcp_server = MandosServer(
        (server_settings["address"], server_settings["port"]),
        ClientHandler,
        interface=(server_settings["interface"] or None),
        use_ipv6=use_ipv6,
        gnutls_priority=server_settings["priority"],
        use_dbus=use_dbus,
        socketfd=socketfd)
    if not foreground:
        pidfilename = "/run/mandos.pid"
        if not os.path.isdir("/run/."):
            pidfilename = "/var/run/mandos.pid"
        pidfile = None
        try:
            pidfile = codecs.open(pidfilename, "w", encoding="utf-8")
        except IOError as e:
            logger.error("Could not open file %r", pidfilename,
                         exc_info=e)
    
    for name, group in (("_mandos", "_mandos"),
                        ("mandos", "mandos"),
                        ("nobody", "nogroup")):
        try:
            uid = pwd.getpwnam(name).pw_uid
            gid = pwd.getpwnam(group).pw_gid
            break
        except KeyError:
            continue
    else:
        uid = 65534
        gid = 65534
    try:
        os.setgid(gid)
        os.setuid(uid)
        if debug:
            logger.debug("Did setuid/setgid to {}:{}".format(uid,
                                                             gid))
    except OSError as error:
        logger.warning("Failed to setuid/setgid to {}:{}: {}"
                       .format(uid, gid, os.strerror(error.errno)))
        if error.errno != errno.EPERM:
            raise
    
    if debug:
        # Enable all possible GnuTLS debugging
        
        # "Use a log level over 10 to enable all debugging options."
        # - GnuTLS manual
        gnutls.global_set_log_level(11)
        
        @gnutls.log_func
        def debug_gnutls(level, string):
            logger.debug("GnuTLS: %s", string[:-1])
        
        gnutls.global_set_log_function(debug_gnutls)
        
        # Redirect stdin so all checkers get /dev/null
        null = os.open(os.devnull, os.O_NOCTTY | os.O_RDWR)
        os.dup2(null, sys.stdin.fileno())
        if null > 2:
            os.close(null)
    
    # Need to fork before connecting to D-Bus
    if not foreground:
        # Close all input and output, do double fork, etc.
        daemon()
    
    # multiprocessing will use threads, so before we use GLib we need
    # to inform GLib that threads will be used.
    GLib.threads_init()
    
    global main_loop
    # From the Avahi example code
    DBusGMainLoop(set_as_default=True)
    main_loop = GLib.MainLoop()
    bus = dbus.SystemBus()
    # End of Avahi example code
    if use_dbus:
        try:
            bus_name = dbus.service.BusName("se.recompile.Mandos",
                                            bus,
                                            do_not_queue=True)
            old_bus_name = dbus.service.BusName(
                "se.bsnet.fukt.Mandos", bus,
                do_not_queue=True)
        except dbus.exceptions.DBusException as e:
            logger.error("Disabling D-Bus:", exc_info=e)
            use_dbus = False
            server_settings["use_dbus"] = False
            tcp_server.use_dbus = False
    if zeroconf:
        protocol = avahi.PROTO_INET6 if use_ipv6 else avahi.PROTO_INET
        service = AvahiServiceToSyslog(
            name = server_settings["servicename"],
            servicetype = "_mandos._tcp",
            protocol = protocol,
            bus = bus)
        if server_settings["interface"]:
            service.interface = if_nametoindex(
                server_settings["interface"].encode("utf-8"))
    
    global multiprocessing_manager
    multiprocessing_manager = multiprocessing.Manager()
    
    client_class = Client
    if use_dbus:
        client_class = functools.partial(ClientDBus, bus = bus)
    
    client_settings = Client.config_parser(client_config)
    old_client_settings = {}
    clients_data = {}
    
    # This is used to redirect stdout and stderr for checker processes
    global wnull
    wnull = open(os.devnull, "w") # A writable /dev/null
    # Only used if server is running in foreground but not in debug
    # mode
    if debug or not foreground:
        wnull.close()
    
    # Get client data and settings from last running state.
    if server_settings["restore"]:
        try:
            with open(stored_state_path, "rb") as stored_state:
                if sys.version_info.major == 2:                
                    clients_data, old_client_settings = pickle.load(
                        stored_state)
                else:
                    bytes_clients_data, bytes_old_client_settings = (
                        pickle.load(stored_state, encoding = "bytes"))
                    ### Fix bytes to strings
                    ## clients_data
                    # .keys()
                    clients_data = { (key.decode("utf-8")
                                      if isinstance(key, bytes)
                                      else key): value
                                     for key, value in
                                     bytes_clients_data.items() }
                    del bytes_clients_data
                    for key in clients_data:
                        value = { (k.decode("utf-8")
                                   if isinstance(k, bytes) else k): v
                                  for k, v in
                                  clients_data[key].items() }
                        clients_data[key] = value
                        # .client_structure
                        value["client_structure"] = [
                            (s.decode("utf-8")
                             if isinstance(s, bytes)
                             else s) for s in
                            value["client_structure"] ]
                        # .name & .host
                        for k in ("name", "host"):
                            if isinstance(value[k], bytes):
                                value[k] = value[k].decode("utf-8")
                    ## old_client_settings
                    # .keys()
                    old_client_settings = {
                        (key.decode("utf-8")
                         if isinstance(key, bytes)
                         else key): value
                        for key, value in
                        bytes_old_client_settings.items() }
                    del bytes_old_client_settings
                    # .host
                    for value in old_client_settings.values():
                        if isinstance(value["host"], bytes):
                            value["host"] = (value["host"]
                                             .decode("utf-8"))
            os.remove(stored_state_path)
        except IOError as e:
            if e.errno == errno.ENOENT:
                logger.warning("Could not load persistent state:"
                               " {}".format(os.strerror(e.errno)))
            else:
                logger.critical("Could not load persistent state:",
                                exc_info=e)
                raise
        except EOFError as e:
            logger.warning("Could not load persistent state: "
                           "EOFError:",
                           exc_info=e)
    
    with PGPEngine() as pgp:
        for client_name, client in clients_data.items():
            # Skip removed clients
            if client_name not in client_settings:
                continue
            
            # Decide which value to use after restoring saved state.
            # We have three different values: Old config file,
            # new config file, and saved state.
            # New config value takes precedence if it differs from old
            # config value, otherwise use saved state.
            for name, value in client_settings[client_name].items():
                try:
                    # For each value in new config, check if it
                    # differs from the old config value (Except for
                    # the "secret" attribute)
                    if (name != "secret"
                        and (value !=
                             old_client_settings[client_name][name])):
                        client[name] = value
                except KeyError:
                    pass
            
            # Clients who has passed its expire date can still be
            # enabled if its last checker was successful.  A Client
            # whose checker succeeded before we stored its state is
            # assumed to have successfully run all checkers during
            # downtime.
            if client["enabled"]:
                if datetime.datetime.utcnow() >= client["expires"]:
                    if not client["last_checked_ok"]:
                        logger.warning(
                            "disabling client {} - Client never "
                            "performed a successful checker".format(
                                client_name))
                        client["enabled"] = False
                    elif client["last_checker_status"] != 0:
                        logger.warning(
                            "disabling client {} - Client last"
                            " checker failed with error code"
                            " {}".format(
                                client_name,
                                client["last_checker_status"]))
                        client["enabled"] = False
                    else:
                        client["expires"] = (
                            datetime.datetime.utcnow()
                            + client["timeout"])
                        logger.debug("Last checker succeeded,"
                                     " keeping {} enabled".format(
                                         client_name))
            try:
                client["secret"] = pgp.decrypt(
                    client["encrypted_secret"],
                    client_settings[client_name]["secret"])
            except PGPError:
                # If decryption fails, we use secret from new settings
                logger.debug("Failed to decrypt {} old secret".format(
                    client_name))
                client["secret"] = (client_settings[client_name]
                                    ["secret"])
    
    # Add/remove clients based on new changes made to config
    for client_name in (set(old_client_settings)
                        - set(client_settings)):
        del clients_data[client_name]
    for client_name in (set(client_settings)
                        - set(old_client_settings)):
        clients_data[client_name] = client_settings[client_name]
    
    # Create all client objects
    for client_name, client in clients_data.items():
        tcp_server.clients[client_name] = client_class(
            name = client_name,
            settings = client,
            server_settings = server_settings)
    
    if not tcp_server.clients:
        logger.warning("No clients defined")
    
    if not foreground:
        if pidfile is not None:
            pid = os.getpid()
            try:
                with pidfile:
                    print(pid, file=pidfile)
            except IOError:
                logger.error("Could not write to file %r with PID %d",
                             pidfilename, pid)
        del pidfile
        del pidfilename
    
    for termsig in (signal.SIGHUP, signal.SIGTERM):
        GLib.unix_signal_add(GLib.PRIORITY_HIGH, termsig,
                             lambda: main_loop.quit() and False)
    
    if use_dbus:
        
        @alternate_dbus_interfaces(
            { "se.recompile.Mandos": "se.bsnet.fukt.Mandos" })
        class MandosDBusService(DBusObjectWithObjectManager):
            """A D-Bus proxy object"""
            
            def __init__(self):
                dbus.service.Object.__init__(self, bus, "/")
            
            _interface = "se.recompile.Mandos"
            
            @dbus.service.signal(_interface, signature="o")
            def ClientAdded(self, objpath):
                "D-Bus signal"
                pass
            
            @dbus.service.signal(_interface, signature="ss")
            def ClientNotFound(self, fingerprint, address):
                "D-Bus signal"
                pass
            
            @dbus_annotations({"org.freedesktop.DBus.Deprecated":
                               "true"})
            @dbus.service.signal(_interface, signature="os")
            def ClientRemoved(self, objpath, name):
                "D-Bus signal"
                pass
            
            @dbus_annotations({"org.freedesktop.DBus.Deprecated":
                               "true"})
            @dbus.service.method(_interface, out_signature="ao")
            def GetAllClients(self):
                "D-Bus method"
                return dbus.Array(c.dbus_object_path for c in
                                  tcp_server.clients.values())
            
            @dbus_annotations({"org.freedesktop.DBus.Deprecated":
                               "true"})
            @dbus.service.method(_interface,
                                 out_signature="a{oa{sv}}")
            def GetAllClientsWithProperties(self):
                "D-Bus method"
                return dbus.Dictionary(
                    { c.dbus_object_path: c.GetAll(
                        "se.recompile.Mandos.Client")
                      for c in tcp_server.clients.values() },
                    signature="oa{sv}")
            
            @dbus.service.method(_interface, in_signature="o")
            def RemoveClient(self, object_path):
                "D-Bus method"
                for c in tcp_server.clients.values():
                    if c.dbus_object_path == object_path:
                        del tcp_server.clients[c.name]
                        c.remove_from_connection()
                        # Don't signal the disabling
                        c.disable(quiet=True)
                        # Emit D-Bus signal for removal
                        self.client_removed_signal(c)
                        return
                raise KeyError(object_path)
            
            del _interface
            
            @dbus.service.method(dbus.OBJECT_MANAGER_IFACE,
                                 out_signature = "a{oa{sa{sv}}}")
            def GetManagedObjects(self):
                """D-Bus method"""
                return dbus.Dictionary(
                    { client.dbus_object_path:
                      dbus.Dictionary(
                          { interface: client.GetAll(interface)
                            for interface in
                                 client._get_all_interface_names()})
                      for client in tcp_server.clients.values()})
            
            def client_added_signal(self, client):
                """Send the new standard signal and the old signal"""
                if use_dbus:
                    # New standard signal
                    self.InterfacesAdded(
                        client.dbus_object_path,
                        dbus.Dictionary(
                            { interface: client.GetAll(interface)
                              for interface in
                              client._get_all_interface_names()}))
                    # Old signal
                    self.ClientAdded(client.dbus_object_path)
            
            def client_removed_signal(self, client):
                """Send the new standard signal and the old signal"""
                if use_dbus:
                    # New standard signal
                    self.InterfacesRemoved(
                        client.dbus_object_path,
                        client._get_all_interface_names())
                    # Old signal
                    self.ClientRemoved(client.dbus_object_path,
                                       client.name)
        
        mandos_dbus_service = MandosDBusService()
    
    def cleanup():
        "Cleanup function; run on exit"
        if zeroconf:
            service.cleanup()
        
        multiprocessing.active_children()
        wnull.close()
        if not (tcp_server.clients or client_settings):
            return
        
        # Store client before exiting. Secrets are encrypted with key
        # based on what config file has. If config file is
        # removed/edited, old secret will thus be unrecovable.
        clients = {}
        with PGPEngine() as pgp:
            for client in tcp_server.clients.values():
                key = client_settings[client.name]["secret"]
                client.encrypted_secret = pgp.encrypt(client.secret,
                                                      key)
                client_dict = {}
                
                # A list of attributes that can not be pickled
                # + secret.
                exclude = { "bus", "changedstate", "secret",
                            "checker", "server_settings" }
                for name, typ in inspect.getmembers(dbus.service
                                                    .Object):
                    exclude.add(name)
                
                client_dict["encrypted_secret"] = (client
                                                   .encrypted_secret)
                for attr in client.client_structure:
                    if attr not in exclude:
                        client_dict[attr] = getattr(client, attr)
                
                clients[client.name] = client_dict
                del client_settings[client.name]["secret"]
        
        try:
            with tempfile.NamedTemporaryFile(
                    mode='wb',
                    suffix=".pickle",
                    prefix='clients-',
                    dir=os.path.dirname(stored_state_path),
                    delete=False) as stored_state:
                pickle.dump((clients, client_settings), stored_state,
                            protocol = 2)
                tempname = stored_state.name
            os.rename(tempname, stored_state_path)
        except (IOError, OSError) as e:
            if not debug:
                try:
                    os.remove(tempname)
                except NameError:
                    pass
            if e.errno in (errno.ENOENT, errno.EACCES, errno.EEXIST):
                logger.warning("Could not save persistent state: {}"
                               .format(os.strerror(e.errno)))
            else:
                logger.warning("Could not save persistent state:",
                               exc_info=e)
                raise
        
        # Delete all clients, and settings from config
        while tcp_server.clients:
            name, client = tcp_server.clients.popitem()
            if use_dbus:
                client.remove_from_connection()
            # Don't signal the disabling
            client.disable(quiet=True)
            # Emit D-Bus signal for removal
            if use_dbus:
                mandos_dbus_service.client_removed_signal(client)
        client_settings.clear()
    
    atexit.register(cleanup)
    
    for client in tcp_server.clients.values():
        if use_dbus:
            # Emit D-Bus signal for adding
            mandos_dbus_service.client_added_signal(client)
        # Need to initiate checking of clients
        if client.enabled:
            client.init_checker()
    
    tcp_server.enable()
    tcp_server.server_activate()
    
    # Find out what port we got
    if zeroconf:
        service.port = tcp_server.socket.getsockname()[1]
    if use_ipv6:
        logger.info("Now listening on address %r, port %d,"
                    " flowinfo %d, scope_id %d",
                    *tcp_server.socket.getsockname())
    else:                       # IPv4
        logger.info("Now listening on address %r, port %d",
                    *tcp_server.socket.getsockname())
    
    #service.interface = tcp_server.socket.getsockname()[3]
    
    try:
        if zeroconf:
            # From the Avahi example code
            try:
                service.activate()
            except dbus.exceptions.DBusException as error:
                logger.critical("D-Bus Exception", exc_info=error)
                cleanup()
                sys.exit(1)
            # End of Avahi example code
        
        GLib.io_add_watch(tcp_server.fileno(), GLib.IO_IN,
                          lambda *args, **kwargs:
                          (tcp_server.handle_request
                           (*args[2:], **kwargs) or True))
        
        logger.debug("Starting main loop")
        main_loop.run()
    except AvahiError as error:
        logger.critical("Avahi Error", exc_info=error)
        cleanup()
        sys.exit(1)
    except KeyboardInterrupt:
        if debug:
            print("", file=sys.stderr)
        logger.debug("Server received KeyboardInterrupt")
    logger.debug("Server exiting")
    # Must run before the D-Bus bus name gets deregistered
    cleanup()


if __name__ == '__main__':
    main()