[feature] add install/uninstall command for helpers

1 files changed, 971 insertions, 0 deletions

diff --git a/src/leap/bitmask/vpn/helpers/linux/bitmask-root b/src/leap/bitmask/vpn/helpers/linux/bitmask-root
new file mode 100755
index 00000000..80ac12e8
--- /dev/null
+++ b/src/leap/bitmask/vpn/helpers/linux/bitmask-root
@@ -0,0 +1,971 @@
+#!/usr/bin/python2.7
+# -*- coding: utf-8 -*-
+#
+# Copyright (C) 2014 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.
+
+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.
+"""
+# TODO should be tested with python3, which can be the default on some distro.
+from __future__ import print_function
+import os
+import re
+import signal
+import socket
+import syslog
+import subprocess
+import sys
+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
+
+
+VERSION = "6"
+SCRIPT = "bitmask-root"
+NAMESERVER = "10.42.0.1"
+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"
+
+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
+
+FIXED_FLAGS = [
+    "--setenv", "LEAPOPENVPN", "1",
+    "--nobind",
+    "--client",
+    "--dev", "tun",
+    "--tls-client",
+    "--remote-cert-tls", "server",
+    "--management-signal",
+    "--script-security", "1",
+    "--user", "nobody",
+    "--remap-usr1", "SIGTERM",
+]
+
+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", "UNIXSOCKET"],
+    "--management-client-user": ["USER"],
+    "--cert": ["FILE"],
+    "--key": ["FILE"],
+    "--ca": ["FILE"],
+    "--fragment": ["NUMBER"]
+}
+
+PARAM_FORMATS = {
+    "NUMBER": lambda s: re.match("^\d+$", s),
+    "PROTO": lambda s: re.match("^(tcp|udp)$", 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)
+}
+
+
+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.path.isfile(OPENVPN_SYSTEM_BIN):
+        return OPENVPN_SYSTEM_BIN
+
+    # the bundle option should be removed from the debian package.
+    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:
+                    flag_params = flag[1:]
+                    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):
+                        if PARAM_FORMATS[param_type](param):
+                            result.append(param)
+                        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()
+    OPENVPN_BIN = get_openvpn_bin()
+    found_leap_openvpn = filter(
+        lambda (p, s): s.startswith(OPENVPN_BIN) and LEAPOPENVPN in s,
+        plist)
+
+    if found_leap_openvpn:
+        pid = found_leap_openvpn[0][0]
+        os.kill(int(pid), signal.SIGTERM)
+
+#
+# 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("^default .*dev ([^\s]*) .*$", routes, flags=re.M)
+    if match and match.groups():
+        return 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("^.*inet ([^ ]*) .*$", addresses, flags=re.M)
+    if match and match.groups():
+        return match.group(1)
+    else:
+        return None
+
+
+def get_local_network_ipv6(device):
+    """
+    Get the local ipv6 addres for a given device.
+
+    :param device:
+    :type device: str
+    """
+    addresses = cmdcheck([IP, "-o", "address", "show", "dev", device])
+    match = re.search("^.*inet6 ([^ ]*) .*$", addresses, flags=re.M)
+    if match and match.groups():
+        return 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)
+
+#
+# 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()
+    # allow dns to localhost
+    ip4tables("-t", "nat", "--append", BITMASK_CHAIN, "--protocol", "udp",
+              "--dest", "127.0.1.1,127.0.0.1", "--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
+    ip4tables("-t", "nat", "--append", BITMASK_CHAIN_NAT_POST,
+              "--protocol", "udp", "--dport", "53", "--jump", "MASQUERADE")
+    ip4tables("-t", "nat", "--append", BITMASK_CHAIN_NAT_POST,
+              "--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")
+
+
+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
+
+    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
+#
+
+
+def main():
+    """
+    Entry point for cmdline execution.
+    """
+    # TODO use argparse instead.
+
+    if len(sys.argv) >= 2:
+        command = "_".join(sys.argv[1:3])
+        args = sys.argv[3:]
+
+        is_restart = False
+        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):
+                log("%s: INFO: bitmask firewall is up" % (SCRIPT,))
+            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")
+    else:
+        bail("ERROR: No such command")
+
+if __name__ == "__main__":
+    debug(" ".join(sys.argv))
+    main()
+    log("done")
+    exit(0)