/mandos/trunk

#!/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 © 2008-2011 Teddy Hogeborn

# Copyright © 2008-2011 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@fukt.bsnet.se>.

# 

from __future__ import (division, absolute_import, print_function,

                        unicode_literals)

import SocketServer as socketserver

import socket

import argparse

import datetime

import errno

import gnutls.crypto

import gnutls.connection

import gnutls.errors

import gnutls.library.functions

import gnutls.library.constants

import gnutls.library.types

import ConfigParser as 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

import cPickle as pickle

import multiprocessing

import dbus

import dbus.service

import gobject

import avahi

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

version = "1.3.0"

#logger = logging.getLogger('mandos')

logger = logging.Logger('mandos')

syslogger = (logging.handlers.SysLogHandler

             (facility = logging.handlers.SysLogHandler.LOG_DAEMON,

              address = str("/dev/log")))

syslogger.setFormatter(logging.Formatter

                       ('Mandos [%(process)d]: %(levelname)s:'

                        ' %(message)s'))

logger.addHandler(syslogger)

console = logging.StreamHandler()

console.setFormatter(logging.Formatter('%(name)s [%(process)d]:'

                                       ' %(levelname)s:'

                                       ' %(message)s'))

logger.addHandler(console)

class AvahiError(Exception):

    def __init__(self, value, *args, **kwargs):

        self.value = value

        super(AvahiError, self).__init__(value, *args, **kwargs)

    def __unicode__(self):

        return unicode(repr(self.value))

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 <http://www.dns-sd.org/ServiceTypes.html>

    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):

        """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 = unicode(self.server.GetAlternativeServiceName(self.name))

        logger.info("Changing Zeroconf service name to %r ...",

                    self.name)

        syslogger.setFormatter(logging.Formatter

                               ('Mandos (%s) [%%(process)d]:'

                                ' %%(levelname)s: %%(message)s'

                                % self.name))

        self.remove()

        try:

            self.add()

        except dbus.exceptions.DBusException as error:

            logger.critical("DBusException: %s", error)

            self.cleanup()

            os._exit(1)

        self.rename_count += 1

    def remove(self):

        """Derived from the Avahi example code"""

        if self.group is not None:

            try:

                self.group.Free()

            except (dbus.exceptions.UnknownMethodException,

                    dbus.exceptions.DBusException) as e:

                pass

            self.group = None

        if self.entry_group_state_changed_match is not None:

            self.entry_group_state_changed_match.remove()

            self.entry_group_state_changed_match = None

    def add(self):

        """Derived from the Avahi example code"""

        self.remove()

        self.group = dbus.Interface(

            self.bus.get_object(avahi.DBUS_NAME,

                                self.server.EntryGroupNew(),

                                follow_name_owner_changes=True),

            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",

                            unicode(error))

            raise AvahiGroupError("State changed: %s"

                                  % unicode(error))

    def cleanup(self):

        """Derived from the Avahi example code"""

        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]:

                logger.error(bad_states[state])

            self.remove()

        elif state == avahi.SERVER_RUNNING:

            self.add()

        else:

            logger.debug("Unknown state: %r", state)

    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 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 gobject 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 gobject event source tag, or None

    created:    datetime.datetime(); (UTC) object creation

    current_checker_command: string; current running checker_command

    disable_hook:  If set, called by disable() as disable_hook(self)

    disable_initiator_tag: a gobject 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_enabled: datetime.datetime(); (UTC)

    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

    runtime_expansions: Allowed attributes for runtime expansion.

    """

    runtime_expansions = ("approval_delay", "approval_duration",

                          "created", "enabled", "fingerprint",

                          "host", "interval", "last_checked_ok",

                          "last_enabled", "name", "timeout")

    @staticmethod

    def _timedelta_to_milliseconds(td):

        "Convert a datetime.timedelta() to milliseconds"

        return ((td.days * 24 * 60 * 60 * 1000)

                + (td.seconds * 1000)

                + (td.microseconds // 1000))

    def timeout_milliseconds(self):

        "Return the 'timeout' attribute in milliseconds"

        return self._timedelta_to_milliseconds(self.timeout)

    def interval_milliseconds(self):

        "Return the 'interval' attribute in milliseconds"

        return self._timedelta_to_milliseconds(self.interval)

    def approval_delay_milliseconds(self):

        return self._timedelta_to_milliseconds(self.approval_delay)

    def __init__(self, name = None, disable_hook=None, config=None):

        """Note: the 'checker' key in 'config' sets the

        'checker_command' attribute and *not* the 'checker'

        attribute."""

        self.name = name

        if config is None:

            config = {}

        logger.debug("Creating client %r", self.name)

        # Uppercase and remove spaces from fingerprint for later

        # comparison purposes with return value from the fingerprint()

        # function

        self.fingerprint = (config["fingerprint"].upper()

                            .replace(" ", ""))

        logger.debug("  Fingerprint: %s", self.fingerprint)

        if "secret" in config:

            self.secret = config["secret"].decode("base64")

        elif "secfile" in config:

            with open(os.path.expanduser(os.path.expandvars

                                         (config["secfile"])),

                      "rb") as secfile:

                self.secret = secfile.read()

        else:

            raise TypeError("No secret or secfile for client %s"

                            % self.name)

        self.host = config.get("host", "")

        self.created = datetime.datetime.utcnow()

        self.enabled = False

        self.last_approval_request = None

        self.last_enabled = None

        self.last_checked_ok = None

        self.timeout = string_to_delta(config["timeout"])

        self.interval = string_to_delta(config["interval"])

        self.disable_hook = disable_hook

        self.checker = None

        self.checker_initiator_tag = None

        self.disable_initiator_tag = None

        self.checker_callback_tag = None

        self.checker_command = config["checker"]

        self.current_checker_command = None

        self.last_connect = None

        self._approved = None

        self.approved_by_default = config.get("approved_by_default",

                                              True)

        self.approvals_pending = 0

        self.approval_delay = string_to_delta(

            config["approval_delay"])

        self.approval_duration = string_to_delta(

            config["approval_duration"])

        self.changedstate = multiprocessing_manager.Condition(multiprocessing_manager.Lock())

    def send_changedstate(self):

        self.changedstate.acquire()

        self.changedstate.notify_all()

        self.changedstate.release()

    def enable(self):

        """Start this client's checker and timeout hooks"""

        if getattr(self, "enabled", False):

            # Already enabled

            return

        self.send_changedstate()

        self.last_enabled = datetime.datetime.utcnow()

        # Schedule a new checker to be started an 'interval' from now,

        # and every interval from then on.

        self.checker_initiator_tag = (gobject.timeout_add

                                      (self.interval_milliseconds(),

                                       self.start_checker))

        # Schedule a disable() when 'timeout' has passed

        self.disable_initiator_tag = (gobject.timeout_add

                                   (self.timeout_milliseconds(),

                                    self.disable))

        self.enabled = True

        # Also start a new checker *right now*.

        self.start_checker()

    def disable(self, quiet=True):

        """Disable this client."""

        if not getattr(self, "enabled", False):

            return False

        if not quiet:

            self.send_changedstate()

        if not quiet:

            logger.info("Disabling client %s", self.name)

        if getattr(self, "disable_initiator_tag", False):

            gobject.source_remove(self.disable_initiator_tag)

            self.disable_initiator_tag = None

        if getattr(self, "checker_initiator_tag", False):

            gobject.source_remove(self.checker_initiator_tag)

            self.checker_initiator_tag = None

        self.stop_checker()

        if self.disable_hook:

            self.disable_hook(self)

        self.enabled = False

        # Do not run this again if called by a gobject.timeout_add

        return False

    def __del__(self):

        self.disable_hook = None

        self.disable()

    def checker_callback(self, pid, condition, command):

        """The checker has completed, so take appropriate actions."""

        self.checker_callback_tag = None

        self.checker = None

        if os.WIFEXITED(condition):

            exitstatus = os.WEXITSTATUS(condition)

            if exitstatus == 0:

                logger.info("Checker for %(name)s succeeded",

                            vars(self))

                self.checked_ok()

            else:

                logger.info("Checker for %(name)s failed",

                            vars(self))

        else:

            logger.warning("Checker for %(name)s crashed?",

                           vars(self))

    def checked_ok(self):

        """Bump up the timeout for this client.

        This should only be called when the client has been seen,

        alive and well.

        """

        self.last_checked_ok = datetime.datetime.utcnow()

        gobject.source_remove(self.disable_initiator_tag)

        self.disable_initiator_tag = (gobject.timeout_add

                                      (self.timeout_milliseconds(),

                                       self.disable))

    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, then if a checker (for some reason) started

        # running slowly and taking more than 'interval' time, 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 a checker exists, make sure it is not a zombie

        try:

            pid, status = os.waitpid(self.checker.pid, os.WNOHANG)

        except (AttributeError, OSError) as error:

            if (isinstance(error, OSError)

                and error.errno != errno.ECHILD):

                raise error

        else:

            if pid:

                logger.warning("Checker was a zombie")

                gobject.source_remove(self.checker_callback_tag)

                self.checker_callback(pid, status,

                                      self.current_checker_command)

        # Start a new checker if needed

        if self.checker is None:

            try:

                # In case checker_command has exactly one % operator

                command = self.checker_command % self.host

            except TypeError:

                # Escape attributes for the shell

                escaped_attrs = dict(

                    (attr,

                     re.escape(unicode(str(getattr(self, attr, "")),

                                       errors=

                                       'replace')))

                    for attr in

                    self.runtime_expansions)

                try:

                    command = self.checker_command % escaped_attrs

                except TypeError as error:

                    logger.error('Could not format string "%s":'

                                 ' %s', self.checker_command, error)

                    return True # Try again later

            self.current_checker_command = command

            try:

                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.)

                self.checker = subprocess.Popen(command,

                                                close_fds=True,

                                                shell=True, cwd="/")

                self.checker_callback_tag = (gobject.child_watch_add

                                             (self.checker.pid,

                                              self.checker_callback,

                                              data=command))

                # The checker may have completed before the gobject

                # watch was added.  Check for this.

                pid, status = os.waitpid(self.checker.pid, os.WNOHANG)

                if pid:

                    gobject.source_remove(self.checker_callback_tag)

                    self.checker_callback(pid, status, command)

            except OSError as error:

                logger.error("Failed to start subprocess: %s",

                             error)

        # Re-run this periodically if run by gobject.timeout_add

        return True

    def stop_checker(self):

        """Force the checker process, if any, to stop."""

        if self.checker_callback_tag:

            gobject.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))

        try:

            os.kill(self.checker.pid, signal.SIGTERM)

            #time.sleep(0.5)

            #if self.checker.poll() is None:

            #    os.kill(self.checker.pid, signal.SIGKILL)

        except OSError as error:

            if error.errno != errno.ESRCH: # No such process

                raise

        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" % 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

class DBusPropertyException(dbus.exceptions.DBusException):

    """A base class for D-Bus property-related exceptions

    """

    def __unicode__(self):

        return unicode(str(self))

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 DBusObjectWithProperties(dbus.service.Object):

    """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.

    """

    @staticmethod

    def _is_dbus_property(obj):

        return getattr(obj, "_dbus_is_property", False)

    def _get_all_dbus_properties(self):

        """Returns a generator of (name, attribute) pairs

        """

        return ((prop._dbus_name, prop)

                for name, prop in

                inspect.getmembers(self, self._is_dbus_property))

    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 name in (property_name,

                     property_name + "_dbus_property"):

            prop = getattr(self, name, None)

            if (prop is None

                or not self._is_dbus_property(prop)

                or prop._dbus_name != property_name

                or (interface_name and prop._dbus_interface

                    and interface_name != prop._dbus_interface)):

                continue

            return prop

        # No such property

        raise DBusPropertyNotFound(self.dbus_object_path + ":"

                                   + interface_name + "."

                                   + property_name)