2
2
# -*- mode: python; coding: utf-8 -*-
4
# Mandos server - give out binary blobs to connecting clients.
6
# This program is partly derived from an example program for an Avahi
7
# service publisher, downloaded from
8
# <http://avahi.org/wiki/PythonPublishExample>. This includes the
9
# following functions: "AvahiService.add", "AvahiService.remove",
10
# "server_state_changed", "entry_group_state_changed", and some lines
14
# Copyright © 2007-2008 Teddy Hogeborn & Björn Påhlsson
16
# This program is free software: you can redistribute it and/or modify
17
# it under the terms of the GNU General Public License as published by
18
# the Free Software Foundation, either version 3 of the License, or
19
# (at your option) any later version.
21
# This program is distributed in the hope that it will be useful,
22
# but WITHOUT ANY WARRANTY; without even the implied warranty of
23
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
24
# GNU General Public License for more details.
26
# You should have received a copy of the GNU General Public License
27
# along with this program. If not, see <http://www.gnu.org/licenses/>.
29
# Contact the authors at <mandos@fukt.bsnet.se>.
32
4
from __future__ import division
61
31
from dbus.mainloop.glib import DBusGMainLoop
64
# Brief description of the operation of this program:
66
# This server announces itself as a Zeroconf service. Connecting
67
# clients use the TLS protocol, with the unusual quirk that this
68
# server program acts as a TLS "client" while a connecting client acts
69
# as a TLS "server". The client (acting as a TLS "server") must
70
# supply an OpenPGP certificate, and the fingerprint of this
71
# certificate is used by this server to look up (in a list read from a
72
# file at start time) which binary blob to give the client. No other
73
# authentication or authorization is done by this server.
35
import logging.handlers
76
37
logger = logging.Logger('mandos')
77
38
syslogger = logging.handlers.SysLogHandler\
81
42
logger.addHandler(syslogger)
85
class AvahiError(Exception):
86
def __init__(self, value):
89
return repr(self.value)
91
class AvahiServiceError(AvahiError):
94
class AvahiGroupError(AvahiError):
98
class AvahiService(object):
100
interface: integer; avahi.IF_UNSPEC or an interface index.
101
Used to optionally bind to the specified interface.
102
name = string; Example: "Mandos"
103
type = string; Example: "_mandos._tcp".
104
See <http://www.dns-sd.org/ServiceTypes.html>
105
port = integer; what port to announce
106
TXT = list of strings; TXT record for the service
107
domain = string; Domain to publish on, default to .local if empty.
108
host = string; Host to publish records for, default to localhost
110
max_renames = integer; maximum number of renames
111
rename_count = integer; counter so we only rename after collisions
112
a sensible number of times
114
def __init__(self, interface = avahi.IF_UNSPEC, name = None,
115
type = None, port = None, TXT = None, domain = "",
116
host = "", max_renames = 12):
117
"""An Avahi (Zeroconf) service. """
118
self.interface = interface
128
self.rename_count = 0
130
"""Derived from the Avahi example code"""
131
if self.rename_count >= self.max_renames:
132
logger.critical(u"No suitable service name found after %i"
133
u" retries, exiting.", rename_count)
134
raise AvahiServiceError("Too many renames")
135
name = server.GetAlternativeServiceName(name)
136
logger.notice(u"Changing name to %r ...", name)
139
self.rename_count += 1
141
"""Derived from the Avahi example code"""
142
if group is not None:
145
"""Derived from the Avahi example code"""
148
group = dbus.Interface\
149
(bus.get_object(avahi.DBUS_NAME,
150
server.EntryGroupNew()),
151
avahi.DBUS_INTERFACE_ENTRY_GROUP)
152
group.connect_to_signal('StateChanged',
153
entry_group_state_changed)
154
logger.debug(u"Adding service '%s' of type '%s' ...",
155
service.name, service.type)
157
self.interface, # interface
158
avahi.PROTO_INET6, # protocol
159
dbus.UInt32(0), # flags
160
self.name, self.type,
161
self.domain, self.host,
162
dbus.UInt16(self.port),
163
avahi.string_array_to_txt_array(self.TXT))
166
# From the Avahi example code:
167
group = None # our entry group
45
# This variable is used to optionally bind to a specified interface.
46
# It is a global variable to fit in with the other variables from the
47
# Avahi server example code.
48
serviceInterface = avahi.IF_UNSPEC
49
# From the Avahi server example code:
50
serviceName = "Mandos"
51
serviceType = "_mandos._tcp" # http://www.dns-sd.org/ServiceTypes.html
52
servicePort = None # Not known at startup
53
serviceTXT = [] # TXT record for the service
54
domain = "" # Domain to publish on, default to .local
55
host = "" # Host to publish records for, default to localhost
56
group = None #our entry group
57
rename_count = 12 # Counter so we only rename after collisions a
58
# sensible number of times
168
59
# End of Avahi example code
176
67
uniquely identify the client
177
68
secret: bytestring; sent verbatim (over TLS) to client
178
69
fqdn: string (FQDN); available for use by the checker command
179
created: datetime.datetime(); object creation, not client host
180
last_checked_ok: datetime.datetime() or None if not yet checked OK
181
timeout: datetime.timedelta(); How long from last_checked_ok
182
until this client is invalid
70
created: datetime.datetime()
71
last_seen: datetime.datetime() or None if not yet seen
72
timeout: datetime.timedelta(); How long from last_seen until
73
this client is invalid
183
74
interval: datetime.timedelta(); How often to start a new checker
184
75
stop_hook: If set, called by stop() as stop_hook(self)
185
76
checker: subprocess.Popen(); a running checker process used
186
77
to see if the client lives.
187
'None' if no process is running.
78
Is None if no process is running.
188
79
checker_initiator_tag: a gobject event source tag, or None
189
80
stop_initiator_tag: - '' -
190
81
checker_callback_tag: - '' -
191
82
checker_command: string; External command which is run to check if
192
client lives. %() expansions are done at
83
client lives. %()s expansions are done at
193
84
runtime with vars(self) as dict, so that for
194
85
instance %(name)s can be used in the command.
195
86
Private attibutes:
196
87
_timeout: Real variable for 'timeout'
197
88
_interval: Real variable for 'interval'
198
_timeout_milliseconds: Used when calling gobject.timeout_add()
89
_timeout_milliseconds: Used by gobject.timeout_add()
199
90
_interval_milliseconds: - '' -
201
92
def _set_timeout(self, timeout):
221
112
interval = property(lambda self: self._interval,
223
114
del _set_interval
224
def __init__(self, name=None, stop_hook=None, fingerprint=None,
225
secret=None, secfile=None, fqdn=None, timeout=None,
226
interval=-1, checker=None):
227
"""Note: the 'checker' argument sets the 'checker_command'
228
attribute and not the 'checker' attribute.."""
115
def __init__(self, name=None, options=None, stop_hook=None,
116
fingerprint=None, secret=None, secfile=None,
117
fqdn=None, timeout=None, interval=-1, checker=None):
230
logger.debug(u"Creating client %r", self.name)
231
119
# Uppercase and remove spaces from fingerprint
232
120
# for later comparison purposes with return value of
233
121
# the fingerprint() function
234
122
self.fingerprint = fingerprint.upper().replace(u" ", u"")
235
logger.debug(u" Fingerprint: %s", self.fingerprint)
237
124
self.secret = secret.decode(u"base64")
240
127
self.secret = sf.read()
243
raise TypeError(u"No secret or secfile for client %s"
130
raise RuntimeError(u"No secret or secfile for client %s"
132
self.fqdn = fqdn # string
246
133
self.created = datetime.datetime.now()
247
self.last_checked_ok = None
248
self.timeout = string_to_delta(timeout)
249
self.interval = string_to_delta(interval)
134
self.last_seen = None
136
self.timeout = options.timeout
138
self.timeout = string_to_delta(timeout)
140
self.interval = options.interval
142
self.interval = string_to_delta(interval)
250
143
self.stop_hook = stop_hook
251
144
self.checker = None
252
145
self.checker_initiator_tag = None
270
163
"""Stop this client.
271
The possibility that a client might be restarted is left open,
272
but not currently used."""
273
# If this client doesn't have a secret, it is already stopped.
275
logger.debug(u"Stopping client %s", self.name)
279
if getattr(self, "stop_initiator_tag", False):
164
The possibility that this client might be restarted is left
165
open, but not currently used."""
166
logger.debug(u"Stopping client %s", self.name)
168
if self.stop_initiator_tag:
280
169
gobject.source_remove(self.stop_initiator_tag)
281
170
self.stop_initiator_tag = None
282
if getattr(self, "checker_initiator_tag", False):
171
if self.checker_initiator_tag:
283
172
gobject.source_remove(self.checker_initiator_tag)
284
173
self.checker_initiator_tag = None
285
174
self.stop_checker()
288
177
# Do not run this again if called by a gobject.timeout_add
290
179
def __del__(self):
291
self.stop_hook = None
180
# Some code duplication here and in stop()
181
if hasattr(self, "stop_initiator_tag") \
182
and self.stop_initiator_tag:
183
gobject.source_remove(self.stop_initiator_tag)
184
self.stop_initiator_tag = None
185
if hasattr(self, "checker_initiator_tag") \
186
and self.checker_initiator_tag:
187
gobject.source_remove(self.checker_initiator_tag)
188
self.checker_initiator_tag = None
293
190
def checker_callback(self, pid, condition):
294
191
"""The checker has completed, so take appropriate actions."""
295
192
now = datetime.datetime.now()
296
self.checker_callback_tag = None
298
193
if os.WIFEXITED(condition) \
299
194
and (os.WEXITSTATUS(condition) == 0):
300
195
logger.debug(u"Checker for %(name)s succeeded",
302
self.last_checked_ok = now
303
198
gobject.source_remove(self.stop_initiator_tag)
304
199
self.stop_initiator_tag = gobject.timeout_add\
305
200
(self._timeout_milliseconds,
311
206
logger.debug(u"Checker for %(name)s failed",
209
self.checker_callback_tag = None
313
210
def start_checker(self):
314
211
"""Start a new checker subprocess if one is not running.
315
212
If a checker already exists, leave it running and do
317
# The reason for not killing a running checker is that if we
318
# did that, then if a checker (for some reason) started
319
# running slowly and taking more than 'interval' time, the
320
# client would inevitably timeout, since no checker would get
321
# a chance to run to completion. If we instead leave running
322
# checkers alone, the checker would have to take more time
323
# than 'timeout' for the client to be declared invalid, which
324
# is as it should be.
325
214
if self.checker is None:
327
# In case check_command has exactly one % operator
328
216
command = self.check_command % self.fqdn
329
217
except TypeError:
330
# Escape attributes for the shell
331
218
escaped_attrs = dict((key, re.escape(str(val)))
333
220
vars(self).iteritems())
335
222
command = self.check_command % escaped_attrs
336
223
except TypeError, error:
337
logger.error(u'Could not format string "%s":'
338
u' %s', self.check_command, error)
224
logger.critical(u'Could not format string "%s":'
225
u' %s', self.check_command, error)
339
226
return True # Try again later
341
228
logger.debug(u"Starting checker %r for %s",
342
229
command, self.name)
343
self.checker = subprocess.Popen(command,
230
self.checker = subprocess.\
232
close_fds=True, shell=True,
346
234
self.checker_callback_tag = gobject.child_watch_add\
347
235
(self.checker.pid,
348
236
self.checker_callback)
354
242
def stop_checker(self):
355
243
"""Force the checker process, if any, to stop."""
356
if self.checker_callback_tag:
357
gobject.source_remove(self.checker_callback_tag)
358
self.checker_callback_tag = None
359
if getattr(self, "checker", None) is None:
244
if not hasattr(self, "checker") or self.checker is None:
361
logger.debug("Stopping checker for %(name)s", vars(self))
363
os.kill(self.checker.pid, signal.SIGTERM)
365
#if self.checker.poll() is None:
366
# os.kill(self.checker.pid, signal.SIGKILL)
367
except OSError, error:
368
if error.errno != errno.ESRCH: # No such process
246
gobject.source_remove(self.checker_callback_tag)
247
self.checker_callback_tag = None
248
os.kill(self.checker.pid, signal.SIGTERM)
249
if self.checker.poll() is None:
250
os.kill(self.checker.pid, signal.SIGKILL)
370
251
self.checker = None
371
def still_valid(self):
252
def still_valid(self, now=None):
372
253
"""Has the timeout not yet passed for this client?"""
373
now = datetime.datetime.now()
374
if self.last_checked_ok is None:
255
now = datetime.datetime.now()
256
if self.last_seen is None:
375
257
return now < (self.created + self.timeout)
377
return now < (self.last_checked_ok + self.timeout)
259
return now < (self.last_seen + self.timeout)
380
262
def peer_certificate(session):
381
"Return the peer's OpenPGP certificate as a bytestring"
263
"Return an OpenPGP data packet string for the peer's certificate"
382
264
# If not an OpenPGP certificate...
383
265
if gnutls.library.functions.gnutls_certificate_type_get\
384
266
(session._c_object) \
433
315
def handle(self):
434
316
logger.debug(u"TCP connection from: %s",
435
317
unicode(self.client_address))
436
session = gnutls.connection.ClientSession\
437
(self.request, gnutls.connection.X509Credentials())
439
line = self.request.makefile().readline()
440
logger.debug(u"Protocol version: %r", line)
442
if int(line.strip().split()[0]) > 1:
444
except (ValueError, IndexError, RuntimeError), error:
445
logger.error(u"Unknown protocol version: %s", error)
448
# Note: gnutls.connection.X509Credentials is really a generic
449
# GnuTLS certificate credentials object so long as no X.509
450
# keys are added to it. Therefore, we can use it here despite
451
# using OpenPGP certificates.
318
session = gnutls.connection.ClientSession(self.request,
453
322
#priority = ':'.join(("NONE", "+VERS-TLS1.1", "+AES-256-CBC",
454
323
# "+SHA1", "+COMP-NULL", "+CTYPE-OPENPGP",
456
priority = "NORMAL" # Fallback default, since this
458
if self.server.settings["priority"]:
459
priority = self.server.settings["priority"]
325
priority = "SECURE256"
460
327
gnutls.library.functions.gnutls_priority_set_direct\
461
328
(session._c_object, priority, None);
476
343
logger.debug(u"Fingerprint: %s", fpr)
478
for c in self.server.clients:
479
346
if c.fingerprint == fpr:
483
logger.debug(u"Client not found for fingerprint: %s", fpr)
486
349
# Have to check if client.still_valid(), since it is possible
487
350
# that the client timed out while establishing the GnuTLS
489
if not client.still_valid():
490
logger.debug(u"Client %(name)s is invalid", vars(client))
352
if (not client) or (not client.still_valid()):
354
logger.debug(u"Client %(name)s is invalid",
357
logger.debug(u"Client not found for fingerprint: %s",
519
387
"""This overrides the normal server_bind() function
520
388
to bind to an interface if one was specified, and also NOT to
521
389
bind to an address or port if they were not specified."""
522
if self.settings["interface"]:
523
# 25 is from /usr/include/asm-i486/socket.h
524
SO_BINDTODEVICE = getattr(socket, "SO_BINDTODEVICE", 25)
390
if self.options.interface:
391
if not hasattr(socket, "SO_BINDTODEVICE"):
392
# From /usr/include/asm-i486/socket.h
393
socket.SO_BINDTODEVICE = 25
526
395
self.socket.setsockopt(socket.SOL_SOCKET,
528
self.settings["interface"])
396
socket.SO_BINDTODEVICE,
397
self.options.interface)
529
398
except socket.error, error:
530
399
if error[0] == errno.EPERM:
531
400
logger.warning(u"No permission to"
532
401
u" bind to interface %s",
533
self.settings["interface"])
402
self.options.interface)
536
405
# Only bind(2) the socket if we really need to.
452
"""From the Avahi server example code"""
453
global group, serviceName, serviceType, servicePort, serviceTXT, \
456
group = dbus.Interface(
457
bus.get_object( avahi.DBUS_NAME,
458
server.EntryGroupNew()),
459
avahi.DBUS_INTERFACE_ENTRY_GROUP)
460
group.connect_to_signal('StateChanged',
461
entry_group_state_changed)
462
logger.debug(u"Adding service '%s' of type '%s' ...",
463
serviceName, serviceType)
466
serviceInterface, # interface
467
avahi.PROTO_INET6, # protocol
468
dbus.UInt32(0), # flags
469
serviceName, serviceType,
471
dbus.UInt16(servicePort),
472
avahi.string_array_to_txt_array(serviceTXT))
476
def remove_service():
477
"""From the Avahi server example code"""
480
if not group is None:
582
484
def server_state_changed(state):
583
"""Derived from the Avahi example code"""
485
"""From the Avahi server example code"""
584
486
if state == avahi.SERVER_COLLISION:
585
487
logger.warning(u"Server name collision")
587
489
elif state == avahi.SERVER_RUNNING:
591
493
def entry_group_state_changed(state, error):
592
"""Derived from the Avahi example code"""
494
"""From the Avahi server example code"""
495
global serviceName, server, rename_count
593
497
logger.debug(u"state change: %i", state)
595
499
if state == avahi.ENTRY_GROUP_ESTABLISHED:
596
500
logger.debug(u"Service established.")
597
501
elif state == avahi.ENTRY_GROUP_COLLISION:
598
logger.warning(u"Service name collision.")
503
rename_count = rename_count - 1
505
name = server.GetAlternativeServiceName(name)
506
logger.warning(u"Service name collision, "
507
u"changing name to '%s' ...", name)
512
logger.error(u"No suitable service name found after %i"
513
u" retries, exiting.", n_rename)
600
515
elif state == avahi.ENTRY_GROUP_FAILURE:
601
logger.critical(u"Error in group state changed %s",
603
raise AvahiGroupError("State changed: %s", str(error))
516
logger.error(u"Error in group state changed %s",
605
521
def if_nametoindex(interface):
606
"""Call the C function if_nametoindex(), or equivalent"""
607
global if_nametoindex
522
"""Call the C function if_nametoindex()"""
609
if "ctypes.util" not in sys.modules:
611
if_nametoindex = ctypes.cdll.LoadLibrary\
612
(ctypes.util.find_library("c")).if_nametoindex
524
libc = ctypes.cdll.LoadLibrary("libc.so.6")
525
return libc.if_nametoindex(interface)
613
526
except (OSError, AttributeError):
614
527
if "struct" not in sys.modules:
616
529
if "fcntl" not in sys.modules:
618
def if_nametoindex(interface):
619
"Get an interface index the hard way, i.e. using fcntl()"
620
SIOCGIFINDEX = 0x8933 # From /usr/include/linux/sockios.h
622
ifreq = fcntl.ioctl(s, SIOCGIFINDEX,
623
struct.pack("16s16x", interface))
625
interface_index = struct.unpack("I", ifreq[16:20])[0]
626
return interface_index
627
return if_nametoindex(interface)
531
SIOCGIFINDEX = 0x8933 # From /usr/include/linux/sockios.h
533
ifreq = fcntl.ioctl(s, SIOCGIFINDEX,
534
struct.pack("16s16x", interface))
536
interface_index = struct.unpack("I", ifreq[16:20])[0]
537
return interface_index
630
540
def daemon(nochdir, noclose):
652
global main_loop_started
561
def killme(status = 0):
562
logger.debug("Stopping server with exit status %d", status)
564
if main_loop_started:
570
if __name__ == '__main__':
653
572
main_loop_started = False
655
573
parser = OptionParser()
656
574
parser.add_option("-i", "--interface", type="string",
657
metavar="IF", help="Bind to interface IF")
658
parser.add_option("-a", "--address", type="string",
659
help="Address to listen for requests on")
660
parser.add_option("-p", "--port", type="int",
575
default=None, metavar="IF",
576
help="Bind to interface IF")
577
parser.add_option("-p", "--port", type="int", default=None,
661
578
help="Port number to receive requests on")
579
parser.add_option("--timeout", type="string", # Parsed later
581
help="Amount of downtime allowed for clients")
582
parser.add_option("--interval", type="string", # Parsed later
584
help="How often to check that a client is up")
662
585
parser.add_option("--check", action="store_true", default=False,
663
586
help="Run self-test")
664
587
parser.add_option("--debug", action="store_true", default=False,
665
help="Debug mode; run in foreground and log to"
667
parser.add_option("--priority", type="string", help="GnuTLS"
668
" priority string (see GnuTLS documentation)")
669
parser.add_option("--servicename", type="string", metavar="NAME",
670
help="Zeroconf service name")
671
parser.add_option("--configdir", type="string",
672
default="/etc/mandos", metavar="DIR",
673
help="Directory to search for configuration"
675
589
(options, args) = parser.parse_args()
677
591
if options.check:
679
593
doctest.testmod()
682
# Default values for config file for server-global settings
683
server_defaults = { "interface": "",
688
"SECURE256:!CTYPE-X.509:+CTYPE-OPENPGP",
689
"servicename": "Mandos",
692
# Parse config file for server-global settings
693
server_config = ConfigParser.SafeConfigParser(server_defaults)
695
server_config.read(os.path.join(options.configdir, "server.conf"))
696
server_section = "server"
697
# Convert the SafeConfigParser object to a dict
698
server_settings = dict(server_config.items(server_section))
699
# Use getboolean on the boolean config option
700
server_settings["debug"] = server_config.getboolean\
701
(server_section, "debug")
704
# Override the settings from the config file with command line
706
for option in ("interface", "address", "port", "debug",
707
"priority", "servicename", "configdir"):
708
value = getattr(options, option)
709
if value is not None:
710
server_settings[option] = value
712
# Now we have our good server settings in "server_settings"
714
# Parse config file with clients
715
client_defaults = { "timeout": "1h",
717
"checker": "fping -q -- %%(fqdn)s",
719
client_config = ConfigParser.SafeConfigParser(client_defaults)
720
client_config.read(os.path.join(server_settings["configdir"],
724
service = AvahiService(name = server_settings["servicename"],
725
type = "_mandos._tcp", );
726
if server_settings["interface"]:
727
service.interface = if_nametoindex(server_settings["interface"])
732
# From the Avahi example code
596
# Parse the time arguments
598
options.timeout = string_to_delta(options.timeout)
600
parser.error("option --timeout: Unparseable time")
602
options.interval = string_to_delta(options.interval)
604
parser.error("option --interval: Unparseable time")
607
defaults = { "checker": "fping -q -- %%(fqdn)s" }
608
client_config = ConfigParser.SafeConfigParser(defaults)
609
#client_config.readfp(open("secrets.conf"), "secrets.conf")
610
client_config.read("mandos-clients.conf")
612
# From the Avahi server example code
733
613
DBusGMainLoop(set_as_default=True )
734
614
main_loop = gobject.MainLoop()
735
615
bus = dbus.SystemBus()
784
663
signal.signal(signal.SIGINT, signal.SIG_IGN)
785
signal.signal(signal.SIGHUP, lambda signum, frame: sys.exit())
786
signal.signal(signal.SIGTERM, lambda signum, frame: sys.exit())
664
signal.signal(signal.SIGHUP, lambda signum, frame: killme())
665
signal.signal(signal.SIGTERM, lambda signum, frame: killme())
788
667
for client in clients:
791
tcp_server = IPv6_TCPServer((server_settings["address"],
792
server_settings["port"]),
670
tcp_server = IPv6_TCPServer((None, options.port),
794
settings=server_settings,
796
# Find out what port we got
797
service.port = tcp_server.socket.getsockname()[1]
798
logger.debug(u"Now listening on address %r, port %d, flowinfo %d,"
799
u" scope_id %d" % tcp_server.socket.getsockname())
801
#service.interface = tcp_server.socket.getsockname()[3]
804
# From the Avahi example code
805
server.connect_to_signal("StateChanged", server_state_changed)
807
server_state_changed(server.GetState())
808
except dbus.exceptions.DBusException, error:
809
logger.critical(u"DBusException: %s", error)
811
# End of Avahi example code
813
gobject.io_add_watch(tcp_server.fileno(), gobject.IO_IN,
814
lambda *args, **kwargs:
815
tcp_server.handle_request\
816
(*args[2:], **kwargs) or True)
818
logger.debug("Starting main loop")
674
# Find out what random port we got
675
servicePort = tcp_server.socket.getsockname()[1]
676
logger.debug(u"Now listening on port %d", servicePort)
678
if options.interface is not None:
679
serviceInterface = if_nametoindex(options.interface)
681
# From the Avahi server example code
682
server.connect_to_signal("StateChanged", server_state_changed)
684
server_state_changed(server.GetState())
685
except dbus.exceptions.DBusException, error:
686
logger.critical(u"DBusException: %s", error)
688
# End of Avahi example code
690
gobject.io_add_watch(tcp_server.fileno(), gobject.IO_IN,
691
lambda *args, **kwargs:
692
tcp_server.handle_request(*args[2:],
819
695
main_loop_started = True
821
except AvahiError, error:
822
logger.critical(u"AvahiError: %s" + unicode(error))
824
697
except KeyboardInterrupt:
828
if __name__ == '__main__':