summaryrefslogtreecommitdiff
path: root/helpers/bitmask-root
blob: 3376ce7c041c762cd9bd951c03fa2e2ba9287633 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
#!/usr/bin/env python3
# -*- coding: utf-8 -*-
#
# Copyright (C) 2014-2019 LEAP
#
# 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/>.
#
"""
This is a privileged helper script for safely running certain commands as root.
It should only be called by the Bitmask application.

Expected paths:

  When installed by distro path:
    /usr/sbin/bitmask-root

  When installed by bundle or from git:
    /usr/local/sbin/bitmask-root

  When installed by snap:
    /snap/bin/riseup-vpn.bitmask-root

USAGE:
  bitmask-root firewall stop
  bitmask-root firewall start [restart] GATEWAY1 GATEWAY2 ...
  bitmask-root openvpn stop
  bitmask-root openvpn start CONFIG1 CONFIG1 ...
  bitmask-root fw-email stop
  bitmask-root fw-email start uid

All actions return exit code 0 for success, non-zero otherwise.

The `openvpn start` action is special: it calls exec on openvpn and replaces
the current process. If the `restart` parameter is passed, the firewall will
not be teared down in the case of an error during launch.
"""
import os
import re
import signal
import socket
import syslog
import subprocess
import sys
import stat
import traceback

cmdcheck = subprocess.check_output

#
# CONSTANTS


def get_no_group_name():
    """
    Return the right group name to use for the current OS.
    Examples:
        - Ubuntu: nogroup
        - Arch: nobody

    :rtype: str or None
    """
    import grp
    try:
        grp.getgrnam('nobody')
        return 'nobody'
    except KeyError:
        try:
            grp.getgrnam('nogroup')
            return 'nogroup'
        except KeyError:
            return None


def tostr(s):
    return s.decode('utf-8')

VERSION = "11"
SCRIPT = "bitmask-root"
NAMESERVER_TCP = "10.41.0.1"
NAMESERVER_UDP = "10.42.0.1"
# for the time being, we're hardcoding tcp on connection params.
NAMESERVER = NAMESERVER_TCP
BITMASK_CHAIN = "bitmask"
BITMASK_CHAIN_NAT_OUT = "bitmask"
BITMASK_CHAIN_NAT_POST = "bitmask_postrouting"
BITMASK_CHAIN_EMAIL = "bitmask_email"
BITMASK_CHAIN_EMAIL_OUT = "bitmask_email_output"
LOCAL_INTERFACE = "lo"
IMAP_PORT = "1984"
SMTP_PORT = "2013"

IP = "/sbin/ip"
IPTABLES = "/sbin/iptables"
IP6TABLES = "/sbin/ip6tables"
SYSCTL = "/sbin/sysctl"

OPENVPN_USER = "nobody"
OPENVPN_GROUP = get_no_group_name()
LEAPOPENVPN = "LEAPOPENVPN"
OPENVPN_SYSTEM_BIN = "/usr/sbin/openvpn"  # Debian location
OPENVPN_LEAP_BIN = "/usr/local/sbin/leap-openvpn"  # installed by bundle
OPENVPN_SNAP_BIN = "/snap/bin/riseup-vpn.openvpn"  # installed by snap

FIXED_FLAGS = [
    "--setenv", "LEAPOPENVPN", "1",
    "--nobind",
    "--client",
    "--dev", "tun",
    "--tls-client",
    "--remote-cert-tls", "server",
    "--management-signal",
    "--script-security", "1",
    "--user", "nobody",
    "--persist-key",
    "--persist-local-ip",
    "--tls-version-min", "1.0",
]

if OPENVPN_GROUP is not None:
    FIXED_FLAGS.extend(["--group", OPENVPN_GROUP])

ALLOWED_FLAGS = {
    "--remote": ["IP", "NUMBER", "PROTO"],
    "--tls-cipher": ["CIPHER"],
    "--cipher": ["CIPHER"],
    "--auth": ["CIPHER"],
    "--management": ["DIR||IP", "UNIXSOCKET||NUMBER"],
    "--management-client-user": ["USER"],
    "--cert": ["FILE"],
    "--key": ["FILE"],
    "--ca": ["FILE"],
    "--fragment": ["NUMBER"],
    "--keepalive": ["NUMBER", "NUMBER"],
    "--verb": ["NUMBER"],
    "--management-client": [],
    "--tun-ipv6": [],
}

PARAM_FORMATS = {
    "NUMBER": lambda s: re.match("^\d+$", s),
    "PROTO": lambda s: re.match("^(tcp|udp|tcp4|udp4)$", s),
    "IP": lambda s: is_valid_address(s),
    "CIPHER": lambda s: re.match("^[A-Z0-9-]+$", s),
    "USER": lambda s: re.match(
        "^[a-zA-Z0-9_\.\@][a-zA-Z0-9_\-\.\@]*\$?$", s),  # IEEE Std 1003.1-2001
    "FILE": lambda s: os.path.isfile(s),
    "DIR": lambda s: os.path.isdir(os.path.split(s)[0]),
    "UNIXSOCKET": lambda s: s == "unix",
    "UID": lambda s: re.match("^[a-zA-Z0-9]+$", s)
}

# Determine Qubes OS version, if any
QUBES_PROXY = os.path.exists("/var/run/qubes/this-is-proxyvm")
if os.path.isdir("/etc/qubes"):
    QUBES_CFG = "/rw/config/"
    QUBES_IPHOOK = QUBES_CFG + "qubes-ip-change-hook"
    QUBES_FW_SCRIPT = QUBES_CFG + "qubes-firewall-user-script"
    if subprocess.call([IPTABLES, "--list", "QBS-FORWARD"]) == 0:
        QUBES_VER = 4
    else:
        QUBES_VER = 3
else:
    # not a Qubes system
    QUBES_VER = 0


DEBUG = os.getenv("DEBUG")
TEST = os.getenv("TEST")

if DEBUG:
    import logging
    formatter = logging.Formatter(
        "%(asctime)s - %(name)s - %(levelname)s - %(message)s")
    ch = logging.StreamHandler()
    ch.setLevel(logging.DEBUG)
    ch.setFormatter(formatter)
    logger = logging.getLogger(__name__)
    logger.setLevel(logging.DEBUG)
    logger.addHandler(ch)

syslog.openlog(SCRIPT)

#
# UTILITY
#


def is_valid_address(value):
    """
    Validate that the passed ip is a valid IP address.

    :param value: the value to be validated
    :type value: str
    :rtype: bool
    """
    try:
        socket.inet_aton(value)
        return True
    except Exception:
        log("%s: ERROR: MALFORMED IP: %s!" % (SCRIPT, value))
        return False


def split_list(_list, regex):
    """
    Split a list based on a regex:
    e.g. split_list(["xx", "yy", "x1", "zz"], "^x") => [["xx", "yy"], ["x1",
    "zz"]]

    :param _list: the list to be split.
    :type _list: list
    :param regex: the regex expression to filter with.
    :type regex: str

    :rtype: list
    """
    if not hasattr(regex, "match"):
        regex = re.compile(regex)
    result = []
    i = 0
    if not _list:
        return result
    while True:
        if regex.match(_list[i]):
            result.append([])
            while True:
                result[-1].append(_list[i])
                i += 1
                if i >= len(_list) or regex.match(_list[i]):
                    break
        else:
            i += 1
        if i >= len(_list):
            break
    return result


def get_process_list():
    """
    Get a process list by reading `/proc` filesystem.

    :return: a list of tuples, each containing pid and command string.
    :rtype: tuple if lists
    """
    res = []
    pids = [pid for pid in os.listdir('/proc') if pid.isdigit()]

    for pid in pids:
        try:
            res.append((pid, open(
                os.path.join(
                    '/proc', pid, 'cmdline'), 'rb').read()))
        except IOError:  # proc has already terminated
            continue
    return filter(None, res)


def run(command, *args, **options):
    """
    Run an external command.

    Options:

      `check`: If True, check the command's output. bail if non-zero. (the
               default is true unless detach or input is true)
      `exitcode`: like `check`, but return exitcode instead of bailing.
      `detach`: If True, run in detached process.
      `input`: If True, open command for writing stream to, returning the Popen
               object.
      `throw`: If True, raise an exception if there is an error instead
               of bailing.
    """
    parts = [command]
    parts.extend(args)
    debug("%s run: %s " % (SCRIPT, " ".join(parts)))

    _check = options.get("check", True)
    _detach = options.get("detach", False)
    _input = options.get("input", False)
    _exitcode = options.get("exitcode", False)
    _throw = options.get("throw", False)

    if not (_check or _throw) or _detach or _input:
        if _input:
            return subprocess.Popen(parts, stdin=subprocess.PIPE)
        else:
            subprocess.Popen(parts)
            return None
    else:
        try:
            devnull = open('/dev/null', 'w')
            subprocess.check_call(parts, stdout=devnull, stderr=devnull)
            return 0
        except subprocess.CalledProcessError as exc:
            if _exitcode:
                if exc.returncode != 1:
                    # 0 or 1 is to be expected, but anything else
                    # should be logged.
                    debug("ERROR: Could not run %s: %s" %
                          (exc.cmd, exc.output), exception=exc)
                return exc.returncode
            elif _throw:
                raise exc
            else:
                bail("ERROR: Could not run %s: %s" % (exc.cmd, exc.output),
                     exception=exc)


def log(msg=None, exception=None, priority=syslog.LOG_INFO):
    """
    print and log warning message or exception.

    :param msg: optional error message.
    :type msg: str
    :param msg: optional exception.
    :type msg: Exception
    :param msg: syslog level
    :type msg: one of LOG_EMERG, LOG_ALERT, LOG_CRIT, LOG_ERR,
               LOG_WARNING, LOG_NOTICE, LOG_INFO, LOG_DEBUG
    """
    if msg is not None:
        print("%s: %s" % (SCRIPT, msg))
        syslog.syslog(priority, msg)
    if exception is not None:
        if TEST or DEBUG:
            traceback.print_exc()
        syslog.syslog(priority, traceback.format_exc())


def debug(msg=None, exception=None):
    """
    Just like log, but is skipped unless DEBUG. Use syslog.LOG_INFO
    even for debug messages (we don't want to miss them).
    """
    if TEST or DEBUG:
        log(msg, exception)


def bail(msg=None, exception=None):
    """
    abnormal exit. like log(), but exits with error status code.
    """
    log(msg, exception)
    exit(1)

#
# OPENVPN
#


def get_openvpn_bin():
    """
    Return the path for either the system openvpn or the one the
    bundle has put there.
    """
    if os.environ.get('SNAP') and os.path.isfile(OPENVPN_SNAP_BIN):
        # the snap option should be removed from the debian package.
        return OPENVPN_SNAP_BIN

    if os.path.isfile(OPENVPN_SYSTEM_BIN):
        return OPENVPN_SYSTEM_BIN

    # the bundle option should also be removed from the debian.
    if os.path.isfile(OPENVPN_LEAP_BIN):
        return OPENVPN_LEAP_BIN


def parse_openvpn_flags(args):
    """
    Take argument list from the command line and parse it, only allowing some
    configuration flags.

    :type args: list
    """
    result = []
    try:
        for flag in split_list(args, "^--"):
            flag_name = flag[0]
            if flag_name in ALLOWED_FLAGS:
                result.append(flag_name)
                required_params = ALLOWED_FLAGS[flag_name]
                if required_params:
                    # flatten if separated by spaces
                    flag_params = [i for sublist in map(
                        lambda s: s.split(), flag[1:]) for i in sublist]
                    if len(flag_params) != len(required_params):
                        log("%s: ERROR: not enough params for %s" %
                            (SCRIPT, flag_name))
                        return None
                    for param, param_type in zip(flag_params, required_params):
                        for tpe in param_type.split("||"):
                            if PARAM_FORMATS[tpe](param):
                                result.append(param)
                                break
                        else:
                            log("%s: ERROR: Bad argument %s" %
                                (SCRIPT, param))
                            return None
            else:
                log("WARNING: unrecognized openvpn flag %s" % flag_name)
        return result
    except Exception as exc:
        log("%s: ERROR PARSING FLAGS: %s" % (SCRIPT, exc))
        if DEBUG:
            logger.exception(exc)
        return None


def openvpn_start(args):
    """
    Launch openvpn, sanitizing input, and replacing the current process with
    the openvpn process.

    :param args: arguments to be passed to openvpn
    :type args: list
    """
    openvpn_flags = parse_openvpn_flags(args)
    if openvpn_flags:
        OPENVPN = get_openvpn_bin()
        flags = [OPENVPN] + FIXED_FLAGS + openvpn_flags
        if DEBUG:
            log("%s: running openvpn with flags:" % (SCRIPT,))
            log(flags)
        # note: first argument to command is ignored, but customarily set to
        # the command.
        os.execv(OPENVPN, flags)
    else:
        bail('ERROR: could not parse openvpn options')


def openvpn_stop(args):
    """
    Stop the openvpn that has likely been launched by bitmask.

    :param args: arguments to openvpn
    :type args: list
    """
    plist = get_process_list()
    for pid, proc in plist:
        if bytes("openvpn", 'utf-8') in proc and bytes(LEAPOPENVPN, 'utf-8') in proc:
            os.kill(int(pid), signal.SIGTERM)
            break

#
# FIREWALL
#


def get_gateways(gateways):
    """
    Filter a passed sequence of gateways, returning only the valid ones.

    :param gateways: a sequence of gateways to filter.
    :type gateways: iterable
    :rtype: iterable
    """
    result = filter(is_valid_address, gateways)
    if not result:
        bail("ERROR: No valid gateways specified")
    else:
        return result


def get_default_device():
    """
    Retrieve the current default network device.

    :rtype: str
    """
    routes = subprocess.check_output([IP, "route", "show"])
    match = re.search(rb"^default .*dev ([^\s]*) .*$", routes, flags=re.M)
    if match and match.groups():
        return tostr(match.group(1))
    else:
        bail("Could not find default device")


def get_local_network_ipv4(device):
    """
    Get the local ipv4 addres for a given device.

    :param device:
    :type device: str
    """
    addresses = cmdcheck([IP, "-o", "address", "show", "dev", device])
    match = re.search(rb"^.*inet ([^ ]*) .*$", addresses, flags=re.M)
    if match and match.groups():
        return tostr(match.group(1))
    else:
        return None


def get_local_network_ipv6(device):
    """
    Get the local ipv6 addres for a given device.

    :param device:
    :type device: str
    """
    addresses = cmdcheck([IP, "-o", "address", "show", "dev", device])
    match = re.search(rb"^.*inet6 ([^ ]*) .*$", addresses, flags=re.M)
    if match and match.groups():
        return tostr(match.group(1))
    else:
        return None


def run_iptable_with_check(cmd, *args, **options):
    """
    Run an iptables command checking to see if it should:
      for --append: run only if rule does not already exist.
      for --insert: run only if rule does not already exist.
      for --delete: run only if rule does exist.
    other commands are run normally.
    """
    if "--insert" in args:
        check_args = [arg.replace("--insert", "--check") for arg in args]
        check_code = run(cmd, *check_args, exitcode=True)
        if check_code != 0:
            run(cmd, *args, **options)
    elif "--append" in args:
        check_args = [arg.replace("--append", "--check") for arg in args]
        check_code = run(cmd, *check_args, exitcode=True)
        if check_code != 0:
            run(cmd, *args, **options)
    elif "--delete" in args:
        check_args = [arg.replace("--delete", "--check") for arg in args]
        check_code = run(cmd, *check_args, exitcode=True)
        if check_code == 0:
            run(cmd, *args, **options)
    else:
        run(cmd, *args, **options)


def iptables(*args, **options):
    """
    Run iptables4 and iptables6.
    """
    ip4tables(*args, **options)
    ip6tables(*args, **options)


def ip4tables(*args, **options):
    """
    Run iptables4 with checks.
    """
    run_iptable_with_check(IPTABLES, *args, **options)


def ip6tables(*args, **options):
    """
    Run iptables6 with checks.
    """
    run_iptable_with_check(IP6TABLES, *args, **options)


def toggle_ipv6(status='disable'):
    if status == 'disable':
        arg = 1
    elif status == 'enable':
        arg = 0
    else:
        return
    cmdcheck([SYSCTL, '-w', 'net.ipv6.conf.all.disable_ipv6=%s' % arg])


#
# NOTE: these tests to see if a chain exists might incorrectly return false.
# This happens when there is an error in calling `iptables --list bitmask`.
#
# For this reason, when stopping the firewall, we do not trust the
# output of ipvx_chain_exists() but instead always attempt to delete
# the chain.
#


def ipv4_chain_exists(chain, table=None):
    """
    Check if a given chain exists. Only returns true if it actually exists,
    but might return false if it exists and iptables failed to run.

    :param chain: the chain to check against
    :type chain: str
    :rtype: bool
    """
    if table is not None:
        code = run(IPTABLES, "-t", table,
                   "--list", chain, "--numeric", exitcode=True)
    else:
        code = run(IPTABLES, "--list", chain, "--numeric", exitcode=True)
    if code == 0:
        return True
    elif code == 1:
        return False
    else:
        log("ERROR: Could not determine state of iptable chain")
        return False


def ipv6_chain_exists(chain):
    """
    see ipv4_chain_exists()

    :param chain: the chain to check against
    :type chain: str
    :rtype: bool
    """
    code = run(IP6TABLES, "--list", chain, "--numeric", exitcode=True)
    if code == 0:
        return True
    elif code == 1:
        return False
    else:
        log("ERROR: Could not determine state of iptable chain")
        return False


def enable_ip_forwarding():
    """
    ip_fowarding must be enabled for the firewall to work.
    """
    with open('/proc/sys/net/ipv4/ip_forward', 'w') as f:
        f.write('1\n')


def firewall_start(args):
    """
    Bring up the firewall.

    :param args: list of gateways, to be sanitized.
    :type args: list
    """
    default_device = get_default_device()
    local_network_ipv4 = get_local_network_ipv4(default_device)
    local_network_ipv6 = get_local_network_ipv6(default_device)
    gateways = get_gateways(args)

    # add custom chain "bitmask" to front of OUTPUT chain for both
    # the 'filter' and the 'nat' tables.
    if not ipv4_chain_exists(BITMASK_CHAIN):
        ip4tables("--new-chain", BITMASK_CHAIN)
    if not ipv4_chain_exists(BITMASK_CHAIN_NAT_OUT, 'nat'):
        ip4tables("--table", "nat", "--new-chain", BITMASK_CHAIN_NAT_OUT)
    if not ipv4_chain_exists(BITMASK_CHAIN_NAT_POST, 'nat'):
        ip4tables("--table", "nat", "--new-chain", BITMASK_CHAIN_NAT_POST)
    if not ipv6_chain_exists(BITMASK_CHAIN):
        ip6tables("--new-chain", BITMASK_CHAIN)
    ip4tables("--table", "nat", "--insert", "OUTPUT",
              "--jump", BITMASK_CHAIN_NAT_OUT)
    ip4tables("--table", "nat", "--insert", "POSTROUTING",
              "--jump", BITMASK_CHAIN_NAT_POST)
    iptables("--insert", "OUTPUT", "--jump", BITMASK_CHAIN)

    # route all ipv4 DNS over VPN
    # (note: NAT does not work with ipv6 until kernel 3.7)
    enable_ip_forwarding()
    if QUBES_PROXY and QUBES_VER >= 3:
        # rewrite DNS packets for VPN DNS; Qubes preconfigures masquerade
        ip4tables("-t", "nat", "--flush", "PR-QBS")
        ip4tables("-t", "nat", "--append", "PR-QBS", "-p", "udp",
                  "--dport", "53", "--jump", "DNAT", "--to",
                  NAMESERVER + ":53")
        ip4tables("-t", "nat", "--append", "PR-QBS", "-p", "tcp",
                  "--dport", "53", "--jump", "DNAT", "--to",
                  NAMESERVER + ":53")
    else:
        # allow dns to localhost
        ip4tables("-t", "nat", "--append", BITMASK_CHAIN, "--protocol", "udp",
                  "--dest", "127.0.1.1,127.0.0.1,127.0.0.53", "--dport", "53",
                  "--jump", "ACCEPT")
        # rewrite all outgoing packets to use VPN DNS server
        # (DNS does sometimes use TCP!)
        ip4tables("-t", "nat", "--append", BITMASK_CHAIN_NAT_OUT, "-p", "udp",
                  "--dport", "53", "--jump", "DNAT", "--to",
                  NAMESERVER + ":53")
        ip4tables("-t", "nat", "--append", BITMASK_CHAIN_NAT_OUT, "-p", "tcp",
                  "--dport", "53", "--jump", "DNAT", "--to",
                  NAMESERVER + ":53")
        # enable masquerading, so that DNS packets rewritten by DNAT will
        # have the correct source IPs. Apply masquerade only to the NAMESERVER,
        # we don't want to apply it to the localhost dns resolver.
        ip4tables("-t", "nat", "--append", BITMASK_CHAIN_NAT_POST,
                  "--dest", NAMESERVER,
                  "--protocol", "udp", "--dport", "53", "--jump", "MASQUERADE")
        ip4tables("-t", "nat", "--append", BITMASK_CHAIN_NAT_POST,
                  "--dest", NAMESERVER,
                  "--protocol", "tcp", "--dport", "53", "--jump", "MASQUERADE")

    # allow local network traffic
    if local_network_ipv4:
        # allow local network destinations
        ip4tables("--append", BITMASK_CHAIN,
                  "--destination", local_network_ipv4, "-o", default_device,
                  "--jump", "ACCEPT")
        # allow local network sources for DNS
        # (required to allow local network DNS that gets rewritten by NAT
        #  to get passed through so that MASQUERADE can set correct source IP)
        ip4tables("--append", BITMASK_CHAIN,
                  "--source", local_network_ipv4, "-o", default_device,
                  "-p", "udp", "--dport", "53", "--jump", "ACCEPT")
        ip4tables("--append", BITMASK_CHAIN,
                  "--source", local_network_ipv4, "-o", default_device,
                  "-p", "tcp", "--dport", "53", "--jump", "ACCEPT")
        # allow multicast Simple Service Discovery Protocol
        ip4tables("--append", BITMASK_CHAIN,
                  "--protocol", "udp",
                  "--destination", "239.255.255.250", "--dport", "1900",
                  "-o", default_device, "--jump", "RETURN")
        # allow multicast Bonjour/mDNS
        ip4tables("--append", BITMASK_CHAIN,
                  "--protocol", "udp",
                  "--destination", "224.0.0.251", "--dport", "5353",
                  "-o", default_device, "--jump", "RETURN")
    if local_network_ipv6:
        ip6tables("--append", BITMASK_CHAIN,
                  "--destination", local_network_ipv6, "-o", default_device,
                  "--jump", "ACCEPT")
        # allow multicast Simple Service Discovery Protocol
        ip6tables("--append", BITMASK_CHAIN,
                  "--protocol", "udp",
                  "--destination", "FF05::C", "--dport", "1900",
                  "-o", default_device, "--jump", "RETURN")
        # allow multicast Bonjour/mDNS
        ip6tables("--append", BITMASK_CHAIN,
                  "--protocol", "udp",
                  "--destination", "FF02::FB", "--dport", "5353",
                  "-o", default_device, "--jump", "RETURN")

    # allow ipv4 traffic to gateways
    for gateway in gateways:
        ip4tables("--append", BITMASK_CHAIN, "--destination", gateway,
                  "-o", default_device, "--jump", "ACCEPT")

    # log rejected packets to syslog
    if DEBUG:
        iptables("--append", BITMASK_CHAIN, "-o", default_device,
                 "--jump", "LOG", "--log-prefix", "iptables denied: ",
                 "--log-level", "7")

    # for now, ensure all other ipv6 packets get rejected (regardless of
    # device). not sure why, but "-p any" doesn't work.
    ip6tables("--append", BITMASK_CHAIN, "-p", "tcp", "--jump", "REJECT")
    ip6tables("--append", BITMASK_CHAIN, "-p", "udp", "--jump", "REJECT")

    # reject all other ipv4 sent over the default device
    ip4tables("--append", BITMASK_CHAIN, "-o",
              default_device, "--jump", "REJECT")

    # On Qubes OS, add anti-leak rules for proxyVM qubes-firewall.service
    # Must stay on 'top' of chain!
    if QUBES_PROXY and QUBES_VER >= 3 and run("grep", "installed\ by\ " +
                                              SCRIPT, QUBES_FW_SCRIPT,
                                              exitcode=True) != 0:
        with open(QUBES_FW_SCRIPT, mode="w") as qfile:
                qfile.write("#!/bin/sh\n")
                qfile.write("# Anti-leak rules installed by " + SCRIPT + " "
                            + VERSION + "\n")
                qfile.write("iptables --insert FORWARD -i eth0 -j DROP\n")
                qfile.write("iptables --insert FORWARD -o eth0 -j DROP\n")
                qfile.write("ip6tables --insert FORWARD -i eth0 -j DROP\n")
                qfile.write("ip6tables --insert FORWARD -o eth0 -j DROP\n")
                qfile.write("iptables --insert INPUT -i tun+ -j DROP\n")
                qfile.write("ip6tables --insert INPUT -i tun+ -j DROP\n")
        os.chmod(QUBES_FW_SCRIPT, stat.S_IRWXU)
        if not os.path.exists(QUBES_IPHOOK):
            os.symlink(QUBES_FW_SCRIPT, QUBES_IPHOOK)
        if QUBES_VER == 4:
            run(QUBES_FW_SCRIPT)
        elif QUBES_VER == 3:
            run("systemctl", "restart", "qubes-firewall.service")

    # toggle_ipv6('disable')


def firewall_stop():
    """
    Stop the firewall. Because we really really always want the firewall to
    be stopped if at all possible, this function is cautious and contains a
    lot of trys and excepts.

    If there were any problems, we raise an exception at the end. This allows
    the calling code to retry stopping the firewall. Stopping the firewall
    can fail if iptables is being run by another process (only one iptables
    command can be run at a time).
    """
    ok = True

    # -t filter -D OUTPUT -j bitmask
    try:
        iptables("--delete", "OUTPUT", "--jump", BITMASK_CHAIN, throw=True)
    except subprocess.CalledProcessError as exc:
        debug("INFO: not able to remove bitmask firewall from OUTPUT chain "
              "(maybe it is already removed?)", exc)
        ok = False

    # -t nat -D OUTPUT -j bitmask
    try:
        ip4tables("-t", "nat", "--delete", "OUTPUT",
                  "--jump", BITMASK_CHAIN_NAT_OUT, throw=True)
    except subprocess.CalledProcessError as exc:
        debug("INFO: not able to remove bitmask firewall from OUTPUT chain "
              "in 'nat' table (maybe it is already removed?)", exc)
        ok = False

    # -t nat -D POSTROUTING -j bitmask_postrouting
    try:
        ip4tables("-t", "nat", "--delete", "POSTROUTING",
                  "--jump", BITMASK_CHAIN_NAT_POST, throw=True)
    except subprocess.CalledProcessError as exc:
        debug("INFO: not able to remove bitmask firewall from POSTROUTING "
              "chain in 'nat' table (maybe it is already removed?)", exc)
        ok = False

    # -t filter --delete-chain bitmask
    try:
        ip4tables("--flush", BITMASK_CHAIN, throw=True)
        ip4tables("--delete-chain", BITMASK_CHAIN, throw=True)
    except subprocess.CalledProcessError as exc:
        debug("INFO: not able to flush and delete bitmask ipv4 firewall "
              "chain (maybe it is already destroyed?)", exc)
        ok = False

    # -t nat --delete-chain bitmask
    try:
        ip4tables("-t", "nat", "--flush", BITMASK_CHAIN_NAT_OUT, throw=True)
        ip4tables("-t", "nat", "--delete-chain",
                  BITMASK_CHAIN_NAT_OUT, throw=True)
    except subprocess.CalledProcessError as exc:
        debug("INFO: not able to flush and delete bitmask ipv4 firewall "
              "chain in 'nat' table (maybe it is already destroyed?)", exc)
        ok = False

    # -t nat --delete-chain bitmask_postrouting
    try:
        ip4tables("-t", "nat", "--flush", BITMASK_CHAIN_NAT_POST, throw=True)
        ip4tables("-t", "nat", "--delete-chain",
                  BITMASK_CHAIN_NAT_POST, throw=True)
    except subprocess.CalledProcessError as exc:
        debug("INFO: not able to flush and delete bitmask ipv4 firewall "
              "chain in 'nat' table (maybe it is already destroyed?)", exc)
        ok = False

    # -t filter --delete-chain bitmask (ipv6)
    try:
        ip6tables("--flush", BITMASK_CHAIN, throw=True)
        ip6tables("--delete-chain", BITMASK_CHAIN, throw=True)
    except subprocess.CalledProcessError as exc:
        debug("INFO: not able to flush and delete bitmask ipv6 firewall "
              "chain (maybe it is already destroyed?)", exc)
        ok = False

    # toggle_ipv6('enable')

    if not (ok or ipv4_chain_exists or ipv6_chain_exists):
        raise Exception("firewall might still be left up. "
                        "Please try `firewall stop` again.")


def fw_email_start(args):
    """
    Bring up the email firewall.

    :param args: the user uid of the bitmask process
    :type args: list
    """
    # add custom chain "bitmask_email" to front of INPUT chain
    if not ipv4_chain_exists(BITMASK_CHAIN_EMAIL):
        ip4tables("--new-chain", BITMASK_CHAIN_EMAIL)
    if not ipv6_chain_exists(BITMASK_CHAIN_EMAIL):
        ip6tables("--new-chain", BITMASK_CHAIN_EMAIL)
    iptables("--insert", "INPUT", "--jump", BITMASK_CHAIN_EMAIL)

    # add custom chain "bitmask_email_output" to front of OUTPUT chain
    if not ipv4_chain_exists(BITMASK_CHAIN_EMAIL_OUT):
        ip4tables("--new-chain", BITMASK_CHAIN_EMAIL_OUT)
    if not ipv6_chain_exists(BITMASK_CHAIN_EMAIL_OUT):
        ip6tables("--new-chain", BITMASK_CHAIN_EMAIL_OUT)
    iptables("--insert", "OUTPUT", "--jump", BITMASK_CHAIN_EMAIL_OUT)

    # Disable the access to imap and smtp from outside
    iptables("--append", BITMASK_CHAIN_EMAIL,
             "--in-interface", LOCAL_INTERFACE, "--protocol", "tcp",
             "--dport", IMAP_PORT, "--jump", "ACCEPT")
    iptables("--append", BITMASK_CHAIN_EMAIL,
             "--in-interface", LOCAL_INTERFACE, "--protocol", "tcp",
             "--dport", SMTP_PORT, "--jump", "ACCEPT")
    iptables("--append", BITMASK_CHAIN_EMAIL,
             "--protocol", "tcp", "--dport", IMAP_PORT, "--jump", "REJECT")
    iptables("--append", BITMASK_CHAIN_EMAIL,
             "--protocol", "tcp", "--dport", SMTP_PORT, "--jump", "REJECT")

    if not args or not PARAM_FORMATS["UID"](args[0]):
        raise Exception("No uid given")
    uid = args[0]

    # Only the unix 'uid' have access to the email imap and smtp ports
    iptables("--append", BITMASK_CHAIN_EMAIL_OUT,
             "--out-interface", LOCAL_INTERFACE,
             "--match", "owner", "--uid-owner", uid, "--protocol", "tcp",
             "--dport", IMAP_PORT, "--jump", "ACCEPT")
    iptables("--append", BITMASK_CHAIN_EMAIL_OUT,
             "--out-interface", LOCAL_INTERFACE,
             "--match", "owner", "--uid-owner", uid, "--protocol", "tcp",
             "--dport", SMTP_PORT, "--jump", "ACCEPT")
    iptables("--append", BITMASK_CHAIN_EMAIL_OUT,
             "--out-interface", LOCAL_INTERFACE,
             "--protocol", "tcp", "--dport", IMAP_PORT, "--jump", "REJECT")
    iptables("--append", BITMASK_CHAIN_EMAIL_OUT,
             "--out-interface", LOCAL_INTERFACE,
             "--protocol", "tcp", "--dport", SMTP_PORT, "--jump", "REJECT")


def fw_email_stop():
    """
    Stop the email firewall.
    """
    ok = True

    try:
        iptables("--delete", "INPUT", "--jump", BITMASK_CHAIN_EMAIL,
                 throw=True)
    except subprocess.CalledProcessError as exc:
        debug("INFO: not able to remove bitmask email firewall from INPUT "
              "chain (maybe it is already removed?)", exc)
        ok = False

    try:
        iptables("--delete", "OUTPUT", "--jump", BITMASK_CHAIN_EMAIL_OUT,
                 throw=True)
    except subprocess.CalledProcessError as exc:
        debug("INFO: not able to remove bitmask email firewall from OUTPUT "
              "chain (maybe it is already removed?)", exc)
        ok = False

    try:
        ip4tables("--flush", BITMASK_CHAIN_EMAIL, throw=True)
        ip4tables("--delete-chain", BITMASK_CHAIN_EMAIL, throw=True)
    except subprocess.CalledProcessError as exc:
        debug("INFO: not able to flush and delete bitmask ipv4 email firewall "
              "chain (maybe it is already destroyed?)", exc)
        ok = False

    try:
        ip6tables("--flush", BITMASK_CHAIN_EMAIL, throw=True)
        ip6tables("--delete-chain", BITMASK_CHAIN_EMAIL, throw=True)
    except subprocess.CalledProcessError as exc:
        debug("INFO: not able to flush and delete bitmask ipv6 email firewall "
              "chain (maybe it is already destroyed?)", exc)
        ok = False

    try:
        ip4tables("--flush", BITMASK_CHAIN_EMAIL_OUT, throw=True)
        ip4tables("--delete-chain", BITMASK_CHAIN_EMAIL_OUT, throw=True)
    except subprocess.CalledProcessError as exc:
        debug("INFO: not able to flush and delete bitmask ipv4 email firewall "
              "chain (maybe it is already destroyed?)", exc)
        ok = False

    try:
        ip6tables("--flush", BITMASK_CHAIN_EMAIL_OUT, throw=True)
        ip6tables("--delete-chain", BITMASK_CHAIN_EMAIL_OUT, throw=True)
    except subprocess.CalledProcessError as exc:
        debug("INFO: not able to flush and delete bitmask ipv6 email firewall "
              "chain (maybe it is already destroyed?)", exc)
        ok = False

    if not (ok or ipv4_chain_exists or ipv6_chain_exists):
        raise Exception("email firewall might still be left up. "
                        "Please try `fw-email stop` again.")


#
# MAIN
#

USAGE = """
This is bitmask-root version {VERSION}

This program manipulates the Bitmask firewall. It is *not* intented to be used
manually.

Commands:

{SCRIPT} version
{SCRIPT} restart
{SCRIPT} openvpn start <args>
{SCRIPT} openvpn stop
{SCRIPT} firewall start <args>
{SCRIPT} firewall stop
{SCRIPT} firewall isup
{SCRIPT} fw-email start
{SCRIPT} fw-email stop
{SCRIPT} fw-email isup
""".format(SCRIPT=SCRIPT, VERSION=VERSION)


def main():
    """
    Entry point for cmdline execution.
    """
    # TODO use argparse instead please.

    if len(sys.argv) >= 2:
        command = "_".join(sys.argv[1:3])
        args = sys.argv[3:]

        is_restart = False

        if command == 'help' or command == '-h':
            print(USAGE)
            exit(0)

        if args and args[0] == 'restart':
            is_restart = True
            args.remove('restart')

        if command == "version":
            print(VERSION)
            exit(0)

        if os.getuid() != 0:
            bail("ERROR: must be run as root")

        if command == "openvpn_start":
            openvpn_start(args)

        elif command == "openvpn_stop":
            openvpn_stop(args)

        elif command == "firewall_start":
            try:
                firewall_start(args)
            except Exception as ex:
                if not is_restart:
                    firewall_stop()
                bail("ERROR: could not start firewall", ex)

        elif command == "firewall_stop":
            try:
                firewall_stop()
            except Exception as ex:
                bail("ERROR: could not stop firewall", ex)

        elif command == "firewall_isup":
            if ipv4_chain_exists(BITMASK_CHAIN):
                # too verbose since bitmask polls this
                pass
            else:
                bail("INFO: bitmask firewall is down")

        elif command == "fw-email_start":
            try:
                fw_email_start(args)
            except Exception as ex:
                if not is_restart:
                    fw_email_stop()
                bail("ERROR: could not start email firewall", ex)

        elif command == "fw-email_stop":
            try:
                fw_email_stop()
            except Exception as ex:
                bail("ERROR: could not stop email firewall", ex)

        elif command == "fw-email_isup":
            if ipv4_chain_exists(BITMASK_CHAIN_EMAIL):
                log("%s: INFO: bitmask email firewall is up" % (SCRIPT,))
            else:
                bail("INFO: bitmask email firewall is down")

        else:
            bail("ERROR: No such command. Try bitmask-root help")
    else:
        bail("ERROR: No such command. Try bitmask-root help")


if __name__ == "__main__":
    debug(" ".join(sys.argv))
    main()
    exit(0)