path: root/src/conf_mode/interfaces-openvpn.py

#!/usr/bin/env python3
#
# Copyright (C) 2019-2020 VyOS maintainers and contributors
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License version 2 or later as
# published by the Free Software Foundation.
#
# 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/>.

import os
import re

from copy import deepcopy
from sys import exit,stderr
from ipaddress import ip_address,ip_network,IPv4Address,IPv4Network,IPv6Address,IPv6Network,summarize_address_range
from netifaces import interfaces
from time import sleep
from shutil import rmtree

from vyos.config import Config
from vyos.ifconfig import VTunIf
from vyos.template import render
from vyos.util import call, chown, chmod_600, chmod_755
from vyos.validate import is_addr_assigned, is_bridge_member, is_ipv4
from vyos import ConfigError

user = 'openvpn'
group = 'openvpn'

default_config_data = {
    'address': [],
    'auth_user': '',
    'auth_pass': '',
    'auth_user_pass_file': '',
    'auth': False,
    'bridge_member': [],
    'compress_lzo': False,
    'deleted': False,
    'description': '',
    'disable': False,
    'disable_ncp': False,
    'encryption': '',
    'hash': '',
    'intf': '',
    'ipv6_autoconf': 0,
    'ipv6_eui64_prefix': [],
    'ipv6_eui64_prefix_remove': [],
    'ipv6_forwarding': 1,
    'ipv6_dup_addr_detect': 1,
    'ipv6_local_address': [],
    'ipv6_remote_address': [],
    'is_bridge_member': False,
    'ping_restart': '60',
    'ping_interval': '10',
    'local_address': [],
    'local_address_subnet': '',
    'local_host': '',
    'local_port': '',
    'mode': '',
    'ncp_ciphers': '',
    'options': [],
    'persistent_tunnel': False,
    'protocol': 'udp',
    'protocol_real': '',
    'redirect_gateway': '',
    'remote_address': [],
    'remote_host': [],
    'remote_port': '',
    'client': [],
    'server_domain': '',
    'server_max_conn': '',
    'server_dns_nameserver': [],
    'server_pool': True,
    'server_pool_start': '',
    'server_pool_stop': '',
    'server_pool_netmask': '',
    'server_push_route': [],
    'server_reject_unconfigured': False,
    'server_subnet': [],
    'server_topology': '',
    'server_ipv6_dns_nameserver': [],
    'server_ipv6_local': '',
    'server_ipv6_prefixlen': '',
    'server_ipv6_remote': '',
    'server_ipv6_pool': True,
    'server_ipv6_pool_base': '',
    'server_ipv6_pool_prefixlen': '',
    'server_ipv6_push_route': [],
    'server_ipv6_subnet': [],
    'shared_secret_file': '',
    'tls': False,
    'tls_auth': '',
    'tls_ca_cert': '',
    'tls_cert': '',
    'tls_crl': '',
    'tls_dh': '',
    'tls_key': '',
    'tls_crypt': '',
    'tls_role': '',
    'tls_version_min': '',
    'type': 'tun',
    'uid': user,
    'gid': group,
}


def get_config_name(intf):
    cfg_file = f'/run/openvpn/{intf}.conf'
    return cfg_file


def checkCertHeader(header, filename):
    """
    Verify if filename contains specified header.
    Returns True if match is found, False if no match or file is not found
    """
    if not os.path.isfile(filename):
        return False

    with open(filename, 'r') as f:
        for line in f:
            if re.match(header, line):
                return True

    return False

def getDefaultServer(network, topology, devtype):
    """
    Gets the default server parameters for a IPv4 "server" directive.
    Logic from openvpn's src/openvpn/helper.c.
    Returns a dict with addresses or False if the input parameters were incorrect.
    """
    if not (devtype == 'tun' or devtype == 'tap'):
        return False

    if not network.version == 4:
        return False
    elif (devtype == 'tun' and network.prefixlen > 29) or (devtype == 'tap' and network.prefixlen > 30):
        return False

    server = {
        'local': '',
        'remote_netmask': '',
        'client_remote_netmask': '',
        'pool_start': '',
        'pool_stop': '',
        'pool_netmask': ''
    }

    if devtype == 'tun':
        if topology == 'net30' or topology == 'point-to-point':
            server['local'] = network[1]
            server['remote_netmask'] = network[2]
            server['client_remote_netmask'] = server['local']

            # pool start is 4th host IP in subnet (.4 in a /24)
            server['pool_start'] = network[4]

            if network.prefixlen == 29:
                server['pool_stop'] = network.broadcast_address
            else:
                # pool end is -4 from the broadcast address (.251 in a /24)
                server['pool_stop'] = network[-5]

        elif topology == 'subnet':
            server['local'] = network[1]
            server['remote_netmask'] = str(network.netmask)
            server['client_remote_netmask'] = server['remote_netmask']
            server['pool_start'] = network[2]
            server['pool_stop'] = network[-3]
            server['pool_netmask'] = server['remote_netmask']

    elif devtype == 'tap':
        server['local'] = network[1]
        server['remote_netmask'] = str(network.netmask)
        server['client_remote_netmask'] = server['remote_netmask']
        server['pool_start'] = network[2]
        server['pool_stop'] = network[-2]
        server['pool_netmask'] = server['remote_netmask']

    return server

def get_config():
    openvpn = deepcopy(default_config_data)
    conf = Config()

    # determine tagNode instance
    if 'VYOS_TAGNODE_VALUE' not in os.environ:
        raise ConfigError('Interface (VYOS_TAGNODE_VALUE) not specified')

    openvpn['intf'] = os.environ['VYOS_TAGNODE_VALUE']
    openvpn['auth_user_pass_file'] = f"/run/openvpn/{openvpn['intf']}.pw"

    # Check if interface instance has been removed
    if not conf.exists('interfaces openvpn ' + openvpn['intf']):
        openvpn['deleted'] = True
        # check if interface is member if a bridge
        openvpn['is_bridge_member'] = is_bridge_member(conf, openvpn['intf'])
        return openvpn

    # Check if we belong to any bridge interface
    for bridge in conf.list_nodes('interfaces bridge'):
        for intf in conf.list_nodes('interfaces bridge {} member interface'.format(bridge)):
            if intf == openvpn['intf']:
                openvpn['bridge_member'].append(intf)

    # bridged server should not have a pool by default (but can be specified manually)
    if openvpn['bridge_member']:
        openvpn['server_pool'] = False
        openvpn['server_ipv6_pool'] = False

    # set configuration level
    conf.set_level('interfaces openvpn ' + openvpn['intf'])

    # retrieve authentication options - username
    if conf.exists('authentication username'):
        openvpn['auth_user'] = conf.return_value('authentication username')
        openvpn['auth'] = True

    # retrieve authentication options - username
    if conf.exists('authentication password'):
        openvpn['auth_pass'] = conf.return_value('authentication password')
        openvpn['auth'] = True

    # retrieve interface description
    if conf.exists('description'):
        openvpn['description'] = conf.return_value('description')

    # interface device-type
    if conf.exists('device-type'):
        openvpn['type'] = conf.return_value('device-type')

    # disable interface
    if conf.exists('disable'):
        openvpn['disable'] = True

    # data encryption algorithm cipher
    if conf.exists('encryption cipher'):
        openvpn['encryption'] = conf.return_value('encryption cipher')

    # disable ncp-ciphers support
    if conf.exists('encryption disable-ncp'):
        openvpn['disable_ncp'] = True

    # data encryption algorithm ncp-list
    if conf.exists('encryption ncp-ciphers'):
        _ncp_ciphers = []
        for enc in conf.return_values('encryption ncp-ciphers'):
            if enc == 'des':
                _ncp_ciphers.append('des-cbc')
                _ncp_ciphers.append('DES-CBC')
            elif enc == '3des':
                _ncp_ciphers.append('des-ede3-cbc')
                _ncp_ciphers.append('DES-EDE3-CBC')
            elif enc == 'aes128':
                _ncp_ciphers.append('aes-128-cbc')
                _ncp_ciphers.append('AES-128-CBC')
            elif enc == 'aes128gcm':
                _ncp_ciphers.append('aes-128-gcm')
                _ncp_ciphers.append('AES-128-GCM')
            elif enc == 'aes192':
                _ncp_ciphers.append('aes-192-cbc')
                _ncp_ciphers.append('AES-192-CBC')
            elif enc == 'aes192gcm':
                _ncp_ciphers.append('aes-192-gcm')
                _ncp_ciphers.append('AES-192-GCM')
            elif enc == 'aes256':
                _ncp_ciphers.append('aes-256-cbc')
                _ncp_ciphers.append('AES-256-CBC')
            elif enc == 'aes256gcm':
                _ncp_ciphers.append('aes-256-gcm')
                _ncp_ciphers.append('AES-256-GCM')
        openvpn['ncp_ciphers'] = ':'.join(_ncp_ciphers)

    # hash algorithm
    if conf.exists('hash'):
        openvpn['hash'] = conf.return_value('hash')

    # Maximum number of keepalive packet failures
    if conf.exists('keep-alive failure-count') and conf.exists('keep-alive interval'):
        fail_count = conf.return_value('keep-alive failure-count')
        interval = conf.return_value('keep-alive interval')
        openvpn['ping_interval' ] = interval
        openvpn['ping_restart' ] = int(interval) * int(fail_count)

    # Local IP address of tunnel - even as it is a tag node - we can only work
    # on the first address
    if conf.exists('local-address'):
        for tmp in conf.list_nodes('local-address'):
            tmp_ip = ip_address(tmp)
            if tmp_ip.version == 4:
                openvpn['local_address'].append(tmp)
                if conf.exists('local-address {} subnet-mask'.format(tmp)):
                    openvpn['local_address_subnet'] = conf.return_value('local-address {} subnet-mask'.format(tmp))
            elif tmp_ip.version == 6:
                # input IPv6 address could be expanded so get the compressed version
                openvpn['ipv6_local_address'].append(str(tmp_ip))

    # Local IP address to accept connections
    if conf.exists('local-host'):
        openvpn['local_host'] = conf.return_value('local-host')

    # Local port number to accept connections
    if conf.exists('local-port'):
        openvpn['local_port'] = conf.return_value('local-port')

    # Enable acquisition of IPv6 address using stateless autoconfig (SLAAC)
    if conf.exists('ipv6 address autoconf'):
        openvpn['ipv6_autoconf'] = 1

    # Get prefix for IPv6 addressing based on MAC address (EUI-64)
    if conf.exists('ipv6 address eui64'):
        openvpn['ipv6_eui64_prefix'].append(conf.return_value('ipv6 address eui64'))

    # Determine currently effective EUI64 address - to determine which
    # address is no longer valid and needs to be removed
    eff_addr = conf.return_effective_value('ipv6 address eui64')
    if eff_addr and eff_addr not in openvpn['ipv6_eui64_prefix']:
        openvpn['ipv6_eui64_prefix_remove'].append(eff_addr)

    # Disable IPv6 forwarding on this interface
    if conf.exists('ipv6 disable-forwarding'):
        openvpn['ipv6_forwarding'] = 0

    # IPv6 Duplicate Address Detection (DAD) tries
    if conf.exists('ipv6 dup-addr-detect-transmits'):
        openvpn['ipv6_dup_addr_detect'] = int(conf.return_value('ipv6 dup-addr-detect-transmits'))

    # OpenVPN operation mode
    if conf.exists('mode'):
        openvpn['mode'] = conf.return_value('mode')

    # Additional OpenVPN options
    if conf.exists('openvpn-option'):
        openvpn['options'] = conf.return_values('openvpn-option')

    # Do not close and reopen interface
    if conf.exists('persistent-tunnel'):
        openvpn['persistent_tunnel'] = True

    # Communication protocol
    if conf.exists('protocol'):
        openvpn['protocol'] = conf.return_value('protocol')

    # IP address of remote end of tunnel
    if conf.exists('remote-address'):
        for tmp in conf.return_values('remote-address'):
            tmp_ip = ip_address(tmp)
            if tmp_ip.version == 4:
                openvpn['remote_address'].append(tmp)
            elif tmp_ip.version == 6:
                openvpn['ipv6_remote_address'].append(str(tmp_ip))

    # Remote host to connect to (dynamic if not set)
    if conf.exists('remote-host'):
        openvpn['remote_host'] = conf.return_values('remote-host')

    # Remote port number to connect to
    if conf.exists('remote-port'):
        openvpn['remote_port'] = conf.return_value('remote-port')

    # OpenVPN tunnel to be used as the default route
    # see https://openvpn.net/community-resources/reference-manual-for-openvpn-2-4/
    # redirect-gateway flags
    if conf.exists('replace-default-route'):
        openvpn['redirect_gateway'] = 'def1'

    if conf.exists('replace-default-route local'):
        openvpn['redirect_gateway'] = 'local def1'

    # Topology for clients
    if conf.exists('server topology'):
        openvpn['server_topology'] = conf.return_value('server topology')

    # Server-mode subnet (from which client IPs are allocated)
    server_network_v4 = None
    server_network_v6 = None
    if conf.exists('server subnet'):
        for tmp in conf.return_values('server subnet'):
            tmp_ip = ip_network(tmp)
            if tmp_ip.version == 4:
                server_network_v4 = tmp_ip
                # convert the network to format: "192.0.2.0 255.255.255.0" for later use in template
                openvpn['server_subnet'].append(tmp_ip.with_netmask.replace(r'/', ' '))
            elif tmp_ip.version == 6:
                server_network_v6 = tmp_ip
                openvpn['server_ipv6_subnet'].append(str(tmp_ip))

    # Client-specific settings
    for client in conf.list_nodes('server client'):
        # set configuration level
        conf.set_level('interfaces openvpn ' + openvpn['intf'] + ' server client ' + client)
        data = {
            'name': client,
            'disable': False,
            'ip': [],
            'ipv6_ip': [],
            'ipv6_remote': '',
            'ipv6_push_route': [],
            'ipv6_subnet': [],
            'push_route': [],
            'subnet': [],
            'remote_netmask': ''
        }

        # Option to disable client connection
        if conf.exists('disable'):
            data['disable'] = True

        # IP address of the client
        for tmp in conf.return_values('ip'):
            tmp_ip = ip_address(tmp)
            if tmp_ip.version == 4:
                data['ip'].append(tmp)
            elif tmp_ip.version == 6:
                data['ipv6_ip'].append(str(tmp_ip))

        # Route to be pushed to the client
        for tmp in conf.return_values('push-route'):
            tmp_ip = ip_network(tmp)
            if tmp_ip.version == 4:
                data['push_route'].append(tmp_ip.with_netmask.replace(r'/', ' '))
            elif tmp_ip.version == 6:
                data['ipv6_push_route'].append(str(tmp_ip))

        # Subnet belonging to the client
        for tmp in conf.return_values('subnet'):
            tmp_ip = ip_network(tmp)
            if tmp_ip.version == 4:
                data['subnet'].append(tmp_ip.with_netmask.replace(r'/', ' '))
            elif tmp_ip.version == 6:
                data['ipv6_subnet'].append(str(tmp_ip))

        # Append to global client list
        openvpn['client'].append(data)

    # re-set configuration level
    conf.set_level('interfaces openvpn ' + openvpn['intf'])

    # Server client IP pool
    if conf.exists('server client-ip-pool'):
        conf.set_level('interfaces openvpn ' + openvpn['intf'] + ' server client-ip-pool')

        # enable or disable server_pool where necessary
        # default is enabled, or disabled in bridge mode
        openvpn['server_pool'] = not conf.exists('disable')

        if conf.exists('start'):
            openvpn['server_pool_start'] = conf.return_value('start')

        if conf.exists('stop'):
            openvpn['server_pool_stop'] = conf.return_value('stop')

        if conf.exists('netmask'):
            openvpn['server_pool_netmask'] = conf.return_value('netmask')

        conf.set_level('interfaces openvpn ' + openvpn['intf'])

    # Server client IPv6 pool
    if conf.exists('server client-ipv6-pool'):
        conf.set_level('interfaces openvpn ' + openvpn['intf'] + ' server client-ipv6-pool')
        openvpn['server_ipv6_pool'] = not conf.exists('disable')
        if conf.exists('base'):
            tmp = conf.return_value('base').split('/')
            openvpn['server_ipv6_pool_base'] = str(IPv6Address(tmp[0]))
            if 1 < len(tmp):
                openvpn['server_ipv6_pool_prefixlen'] = tmp[1]

        conf.set_level('interfaces openvpn ' + openvpn['intf'])

    # DNS suffix to be pushed to all clients
    if conf.exists('server domain-name'):
        openvpn['server_domain'] = conf.return_value('server domain-name')

    # Number of maximum client connections
    if conf.exists('server max-connections'):
        openvpn['server_max_conn'] = conf.return_value('server max-connections')

    # Domain Name Server (DNS)
    if conf.exists('server name-server'):
        for tmp in conf.return_values('server name-server'):
            tmp_ip = ip_address(tmp)
            if tmp_ip.version == 4:
                openvpn['server_dns_nameserver'].append(tmp)
            elif tmp_ip.version == 6:
                openvpn['server_ipv6_dns_nameserver'].append(str(tmp_ip))

    # Route to be pushed to all clients
    if conf.exists('server push-route'):
        for tmp in conf.return_values('server push-route'):
            tmp_ip = ip_network(tmp)
            if tmp_ip.version == 4:
                openvpn['server_push_route'].append(tmp_ip.with_netmask.replace(r'/', ' '))
            elif tmp_ip.version == 6:
                openvpn['server_ipv6_push_route'].append(str(tmp_ip))

    # Reject connections from clients that are not explicitly configured
    if conf.exists('server reject-unconfigured-clients'):
        openvpn['server_reject_unconfigured'] = True

    # File containing TLS auth static key
    if conf.exists('tls auth-file'):
        openvpn['tls_auth'] = conf.return_value('tls auth-file')
        openvpn['tls'] = True

    # File containing certificate for Certificate Authority (CA)
    if conf.exists('tls ca-cert-file'):
         openvpn['tls_ca_cert'] = conf.return_value('tls ca-cert-file')
         openvpn['tls'] = True

    # File containing certificate for this host
    if conf.exists('tls cert-file'):
         openvpn['tls_cert'] = conf.return_value('tls cert-file')
         openvpn['tls'] = True

    # File containing certificate revocation list (CRL) for this host
    if conf.exists('tls crl-file'):
         openvpn['tls_crl'] = conf.return_value('tls crl-file')
         openvpn['tls'] = True

    # File containing Diffie Hellman parameters (server only)
    if conf.exists('tls dh-file'):
         openvpn['tls_dh'] = conf.return_value('tls dh-file')
         openvpn['tls'] = True

    # File containing this host's private key
    if conf.exists('tls key-file'):
         openvpn['tls_key'] = conf.return_value('tls key-file')
         openvpn['tls'] = True

    # File containing key to encrypt control channel packets
    if conf.exists('tls crypt-file'):
         openvpn['tls_crypt'] = conf.return_value('tls crypt-file')
         openvpn['tls'] = True

    # Role in TLS negotiation
    if conf.exists('tls role'):
         openvpn['tls_role'] = conf.return_value('tls role')
         openvpn['tls'] = True

    # Minimum required TLS version
    if conf.exists('tls tls-version-min'):
         openvpn['tls_version_min'] = conf.return_value('tls tls-version-min')
         openvpn['tls'] = True

    if conf.exists('shared-secret-key-file'):
        openvpn['shared_secret_file'] = conf.return_value('shared-secret-key-file')

    if conf.exists('use-lzo-compression'):
        openvpn['compress_lzo'] = True

    # Special case when using EC certificates:
    # if key-file is EC and dh-file is unset, set tls_dh to 'none'
    if not openvpn['tls_dh'] and openvpn['tls_key'] and checkCertHeader('-----BEGIN EC PRIVATE KEY-----', openvpn['tls_key']):
        openvpn['tls_dh'] = 'none'

    # set default server topology to net30
    if openvpn['mode'] == 'server' and not openvpn['server_topology']:
        openvpn['server_topology'] = 'net30'

    # Convert protocol to real protocol used by openvpn.
    # To make openvpn listen on both IPv4 and IPv6 we must use *6 protocols
    # (https://community.openvpn.net/openvpn/ticket/360), unless local is IPv4
    # in which case it must use the standard protocols.
    # Note: this will break openvpn if IPv6 is disabled on the system.
    # This currently isn't supported, a check can be added in the future.
    if openvpn['protocol'] == 'tcp-active':
        openvpn['protocol_real'] = 'tcp6-client'
    elif openvpn['protocol'] == 'tcp-passive':
        openvpn['protocol_real'] = 'tcp6-server'
    else:
        openvpn['protocol_real'] = 'udp6'

    if is_ipv4(openvpn['local_host']):
        # takes out the '6'
        openvpn['protocol_real'] = openvpn['protocol_real'][:3] + openvpn['protocol_real'][4:]

    # Set defaults where necessary.
    # If any of the input parameters are wrong,
    # this will return False and no defaults will be set.
    if server_network_v4 and openvpn['server_topology'] and openvpn['type']:
        default_server = None
        default_server = getDefaultServer(server_network_v4, openvpn['server_topology'], openvpn['type'])
        if default_server:
            # server-bridge doesn't require a pool so don't set defaults for it
            if openvpn['server_pool'] and not openvpn['bridge_member']:
                if not openvpn['server_pool_start']:
                    openvpn['server_pool_start'] = default_server['pool_start']

                if not openvpn['server_pool_stop']:
                    openvpn['server_pool_stop'] = default_server['pool_stop']

                if not openvpn['server_pool_netmask']:
                    openvpn['server_pool_netmask'] = default_server['pool_netmask']

            for client in openvpn['client']:
                client['remote_netmask'] = default_server['client_remote_netmask']

    if server_network_v6:
        if not openvpn['server_ipv6_local']:
            openvpn['server_ipv6_local'] = server_network_v6[1]
        if not openvpn['server_ipv6_prefixlen']:
            openvpn['server_ipv6_prefixlen'] = server_network_v6.prefixlen
        if not openvpn['server_ipv6_remote']:
            openvpn['server_ipv6_remote'] = server_network_v6[2]

        if openvpn['server_ipv6_pool'] and server_network_v6.prefixlen < 112:
            if not openvpn['server_ipv6_pool_base']:
                openvpn['server_ipv6_pool_base'] = server_network_v6[0x1000]
            if not openvpn['server_ipv6_pool_prefixlen']:
                openvpn['server_ipv6_pool_prefixlen'] = openvpn['server_ipv6_prefixlen']

        for client in openvpn['client']:
            client['ipv6_remote'] = openvpn['server_ipv6_local']

        if openvpn['redirect_gateway']:
            openvpn['redirect_gateway'] += ' ipv6'

    return openvpn

def verify(openvpn):
    if openvpn['deleted']:
        if openvpn['is_bridge_member']:
            interface = openvpn['intf']
            bridge = openvpn['is_bridge_member']
            raise ConfigError(f'Interface "{interface}" can not be deleted as it belongs to bridge "{bridge}"!')

        return None


    if not openvpn['mode']:
        raise ConfigError('Must specify OpenVPN operation mode')

    # Checks which need to be performed on interface rmeoval
    if openvpn['deleted']:
        # OpenVPN interface can not be deleted if it's still member of a bridge
        if openvpn['bridge_member']:
            raise ConfigError('Can not delete {} as it is a member interface of bridge {}!'.format(openvpn['intf'], bridge))

    # Check if we have disabled ncp and at the same time specified ncp-ciphers
    if openvpn['disable_ncp'] and openvpn['ncp_ciphers']:
        raise ConfigError('Cannot specify both "encryption disable-ncp" and "encryption ncp-ciphers"')
    #
    # OpenVPN client mode - VERIFY
    #
    if openvpn['mode'] == 'client':
        if openvpn['local_port']:
            raise ConfigError('Cannot specify "local-port" in client mode')

        if openvpn['local_host']:
            raise ConfigError('Cannot specify "local-host" in client mode')

        if openvpn['protocol'] == 'tcp-passive':
            raise ConfigError('Protocol "tcp-passive" is not valid in client mode')

        if not openvpn['remote_host']:
            raise ConfigError('Must specify "remote-host" in client mode')

        if openvpn['tls_dh'] and openvpn['tls_dh'] != 'none':
            raise ConfigError('Cannot specify "tls dh-file" in client mode')

    #
    # OpenVPN site-to-site - VERIFY
    #
    if openvpn['mode'] == 'site-to-site':
        if openvpn['ncp_ciphers']:
            raise ConfigError('encryption ncp-ciphers cannot be specified in site-to-site mode, only server or client')

    if openvpn['mode'] == 'site-to-site' and not openvpn['bridge_member']:
        if not (openvpn['local_address'] or openvpn['ipv6_local_address']):
            raise ConfigError('Must specify "local-address" or "bridge member interface"')

        if len(openvpn['local_address']) > 1 or len(openvpn['ipv6_local_address']) > 1:
            raise ConfigError('Cannot specify more than 1 IPv4 and 1 IPv6 "local-address"')

        if len(openvpn['remote_address']) > 1 or len(openvpn['ipv6_remote_address']) > 1:
            raise ConfigError('Cannot specify more than 1 IPv4 and 1 IPv6 "remote-address"')

        for host in openvpn['remote_host']:
            if host in openvpn['remote_address'] or host in openvpn['ipv6_remote_address']:
                raise ConfigError('"remote-address" cannot be the same as "remote-host"')

        if openvpn['local_address'] and not (openvpn['remote_address'] or openvpn['local_address_subnet']):
            raise ConfigError('IPv4 "local-address" requires IPv4 "remote-address" or IPv4 "local-address subnet"')

        if openvpn['remote_address'] and not openvpn['local_address']:
            raise ConfigError('IPv4 "remote-address" requires IPv4 "local-address"')

        if openvpn['ipv6_local_address'] and not openvpn['ipv6_remote_address']:
            raise ConfigError('IPv6 "local-address" requires IPv6 "remote-address"')

        if openvpn['ipv6_remote_address'] and not openvpn['ipv6_local_address']:
            raise ConfigError('IPv6 "remote-address" requires IPv6 "local-address"')

        if openvpn['type'] == 'tun':
            if not (openvpn['remote_address'] or openvpn['ipv6_remote_address']):
                raise ConfigError('Must specify "remote-address"')

            if ( (openvpn['local_address'] and openvpn['local_address'] == openvpn['remote_address']) or
                    (openvpn['ipv6_local_address'] and openvpn['ipv6_local_address'] == openvpn['ipv6_remote_address']) ):
                raise ConfigError('"local-address" and "remote-address" cannot be the same')

            if openvpn['local_host'] in openvpn['local_address'] or openvpn['local_host'] in openvpn['ipv6_local_address']:
                raise ConfigError('"local-address" cannot be the same as "local-host"')

    else:
        # checks for client-server or site-to-site bridged
        if openvpn['local_address'] or openvpn['ipv6_local_address'] or openvpn['remote_address'] or openvpn['ipv6_remote_address']:
            raise ConfigError('Cannot specify "local-address" or "remote-address" in client-server or bridge mode')

    #
    # OpenVPN server mode - VERIFY
    #
    if openvpn['mode'] == 'server':
        if openvpn['protocol'] == 'tcp-active':
            raise ConfigError('Protocol "tcp-active" is not valid in server mode')

        if openvpn['remote_port']:
            raise ConfigError('Cannot specify "remote-port" in server mode')

        if openvpn['remote_host']:
            raise ConfigError('Cannot specify "remote-host" in server mode')

        if openvpn['protocol'] == 'tcp-passive' and len(openvpn['remote_host']) > 1:
            raise ConfigError('Cannot specify more than 1 "remote-host" with "tcp-passive"')

        if not openvpn['tls_dh'] and not checkCertHeader('-----BEGIN EC PRIVATE KEY-----', openvpn['tls_key']):
            raise ConfigError('Must specify "tls dh-file" when not using EC keys in server mode')

        if len(openvpn['server_subnet']) > 1 or len(openvpn['server_ipv6_subnet']) > 1:
            raise ConfigError('Cannot specify more than 1 IPv4 and 1 IPv6 server subnet')

        for client in openvpn['client']:
            if len(client['ip']) > 1 or len(client['ipv6_ip']) > 1:
                raise ConfigError(f'Server client "{client["name"]}": cannot specify more than 1 IPv4 and 1 IPv6 IP')

        if openvpn['server_subnet']:
            subnet = IPv4Network(openvpn['server_subnet'][0].replace(' ', '/'))

            if openvpn['type'] == 'tun' and subnet.prefixlen > 29:
                raise ConfigError('Server subnets smaller than /29 with device type "tun" are not supported')
            elif openvpn['type'] == 'tap' and subnet.prefixlen > 30:
                raise ConfigError('Server subnets smaller than /30 with device type "tap" are not supported')

            for client in openvpn['client']:
                if client['ip'] and not IPv4Address(client['ip'][0]) in subnet:
                    raise ConfigError(f'Client "{client["name"]}" IP {client["ip"][0]} not in server subnet {subnet}')

        else:
            if not openvpn['bridge_member']:
                raise ConfigError('Must specify "server subnet" or "bridge member interface" in server mode')

        if openvpn['server_pool']:
            if not (openvpn['server_pool_start'] and openvpn['server_pool_stop']):
                raise ConfigError('Server client-ip-pool requires both start and stop addresses in bridged mode')
            else:
                v4PoolStart = IPv4Address(openvpn['server_pool_start'])
                v4PoolStop = IPv4Address(openvpn['server_pool_stop'])
                if v4PoolStart > v4PoolStop:
                    raise ConfigError(f'Server client-ip-pool start address {v4PoolStart} is larger than stop address {v4PoolStop}')

                v4PoolSize = int(v4PoolStop) - int(v4PoolStart)
                if v4PoolSize >= 65536:
                    raise ConfigError(f'Server client-ip-pool is too large [{v4PoolStart} -> {v4PoolStop} = {v4PoolSize}], maximum is 65536 addresses.')

                v4PoolNets = list(summarize_address_range(v4PoolStart, v4PoolStop))
                for client in openvpn['client']:
                    if client['ip']:
                        for v4PoolNet in v4PoolNets:
                            if IPv4Address(client['ip'][0]) in v4PoolNet:
                                print(f'Warning: Client "{client["name"]}" IP {client["ip"][0]} is in server IP pool, it is not reserved for this client.',
                                        file=stderr)

        if openvpn['server_ipv6_subnet']:
            if not openvpn['server_subnet']:
                raise ConfigError('IPv6 server requires an IPv4 server subnet')

            if openvpn['server_ipv6_pool']:
                if not openvpn['server_pool']:
                    raise ConfigError('IPv6 server pool requires an IPv4 server pool')

                if int(openvpn['server_ipv6_pool_prefixlen']) >= 112:
                    raise ConfigError('IPv6 server pool must be larger than /112')

                v6PoolStart = IPv6Address(openvpn['server_ipv6_pool_base'])
                v6PoolStop = IPv6Network((v6PoolStart, openvpn['server_ipv6_pool_prefixlen']), strict=False)[-1] # don't remove the parentheses, it's a 2-tuple
                v6PoolSize = int(v6PoolStop) - int(v6PoolStart) if int(openvpn['server_ipv6_pool_prefixlen']) > 96 else 65536
                if v6PoolSize < v4PoolSize:
                    raise ConfigError(f'IPv6 server pool must be at least as large as the IPv4 pool (current sizes: IPv6={v6PoolSize} IPv4={v4PoolSize})')

                v6PoolNets = list(summarize_address_range(v6PoolStart, v6PoolStop))
                for client in openvpn['client']:
                    if client['ipv6_ip']:
                        for v6PoolNet in v6PoolNets:
                            if IPv6Address(client['ipv6_ip'][0]) in v6PoolNet:
                                print(f'Warning: Client "{client["name"]}" IP {client["ipv6_ip"][0]} is in server IP pool, it is not reserved for this client.',
                                        file=stderr)

        else:
            if openvpn['server_ipv6_push_route']:
                raise ConfigError('IPv6 push-route requires an IPv6 server subnet')

            for client in openvpn ['client']:
                if client['ipv6_ip']:
                    raise ConfigError(f'Server client "{client["name"]}" IPv6 IP requires an IPv6 server subnet')
                if client['ipv6_push_route']:
                    raise ConfigError(f'Server client "{client["name"]} IPv6 push-route requires an IPv6 server subnet"')
                if client['ipv6_subnet']:
                    raise ConfigError(f'Server client "{client["name"]} IPv6 subnet requires an IPv6 server subnet"')

    else:
        # checks for both client and site-to-site go here
        if openvpn['server_reject_unconfigured']:
            raise ConfigError('reject-unconfigured-clients is only supported in OpenVPN server mode')

        if openvpn['server_topology']:
            raise ConfigError('The "topology" option is only valid in server mode')

        if (not openvpn['remote_host']) and openvpn['redirect_gateway']:
            raise ConfigError('Cannot set "replace-default-route" without "remote-host"')

    #
    # OpenVPN common verification section
    # not depending on any operation mode
    #

    # verify specified IP address is present on any interface on this system
    if openvpn['local_host']:
        if not is_addr_assigned(openvpn['local_host']):
            raise ConfigError('No interface on system with specified local-host IP address: {}'.format(openvpn['local_host']))

    # TCP active
    if openvpn['protocol'] == 'tcp-active':
        if openvpn['local_port']:
            raise ConfigError('Cannot specify "local-port" with "tcp-active"')

        if not openvpn['remote_host']:
            raise ConfigError('Must specify "remote-host" with "tcp-active"')

    # shared secret and TLS
    if not (openvpn['shared_secret_file'] or openvpn['tls']):
        raise ConfigError('Must specify one of "shared-secret-key-file" and "tls"')

    if openvpn['shared_secret_file'] and openvpn['tls']:
        raise ConfigError('Can only specify one of "shared-secret-key-file" and "tls"')

    if openvpn['mode'] in ['client', 'server']:
        if not openvpn['tls']:
            raise ConfigError('Must specify "tls" in client-server mode')

    #
    # TLS/encryption
    #
    if openvpn['shared_secret_file']:
        if openvpn['encryption'] in ['aes128gcm', 'aes192gcm', 'aes256gcm']:
            raise ConfigError('GCM encryption with shared-secret-key-file is not supported')

        if not checkCertHeader('-----BEGIN OpenVPN Static key V1-----', openvpn['shared_secret_file']):
            raise ConfigError('Specified shared-secret-key-file "{}" is not valid'.format(openvpn['shared_secret_file']))

    if openvpn['tls']:
        if not openvpn['tls_ca_cert']:
            raise ConfigError('Must specify "tls ca-cert-file"')

        if not (openvpn['mode'] == 'client' and openvpn['auth']):
            if not openvpn['tls_cert']:
                raise ConfigError('Must specify "tls cert-file"')

            if not openvpn['tls_key']:
                raise ConfigError('Must specify "tls key-file"')

        if openvpn['tls_auth'] and openvpn['tls_crypt']:
            raise ConfigError('TLS auth and crypt are mutually exclusive')

        if not checkCertHeader('-----BEGIN CERTIFICATE-----', openvpn['tls_ca_cert']):
            raise ConfigError('Specified ca-cert-file "{}" is invalid'.format(openvpn['tls_ca_cert']))

        if openvpn['tls_auth']:
            if not checkCertHeader('-----BEGIN OpenVPN Static key V1-----', openvpn['tls_auth']):
                raise ConfigError('Specified auth-file "{}" is invalid'.format(openvpn['tls_auth']))

        if openvpn['tls_cert']:
            if not checkCertHeader('-----BEGIN CERTIFICATE-----', openvpn['tls_cert']):
                raise ConfigError('Specified cert-file "{}" is invalid'.format(openvpn['tls_cert']))

        if openvpn['tls_key']:
            if not checkCertHeader('-----BEGIN (?:RSA |EC )?PRIVATE KEY-----', openvpn['tls_key']):
                raise ConfigError('Specified key-file "{}" is not valid'.format(openvpn['tls_key']))

        if openvpn['tls_crypt']:
            if not checkCertHeader('-----BEGIN OpenVPN Static key V1-----', openvpn['tls_crypt']):
                raise ConfigError('Specified TLS crypt-file "{}" is invalid'.format(openvpn['tls_crypt']))

        if openvpn['tls_crl']:
            if not checkCertHeader('-----BEGIN X509 CRL-----', openvpn['tls_crl']):
                raise ConfigError('Specified crl-file "{} not valid'.format(openvpn['tls_crl']))

        if openvpn['tls_dh'] and openvpn['tls_dh'] != 'none':
            if not checkCertHeader('-----BEGIN DH PARAMETERS-----', openvpn['tls_dh']):
                raise ConfigError('Specified dh-file "{}" is not valid'.format(openvpn['tls_dh']))

        if openvpn['tls_role']:
            if openvpn['mode'] in ['client', 'server']:
                if not openvpn['tls_auth']:
                    raise ConfigError('Cannot specify "tls role" in client-server mode')

            if openvpn['tls_role'] == 'active':
                if openvpn['protocol'] == 'tcp-passive':
                    raise ConfigError('Cannot specify "tcp-passive" when "tls role" is "active"')

                if openvpn['tls_dh'] and openvpn['tls_dh'] != 'none':
                    raise ConfigError('Cannot specify "tls dh-file" when "tls role" is "active"')

            elif openvpn['tls_role'] == 'passive':
                if openvpn['protocol'] == 'tcp-active':
                    raise ConfigError('Cannot specify "tcp-active" when "tls role" is "passive"')

                if not openvpn['tls_dh']:
                    raise ConfigError('Must specify "tls dh-file" when "tls role" is "passive"')

        if openvpn['tls_key'] and checkCertHeader('-----BEGIN EC PRIVATE KEY-----', openvpn['tls_key']):
            if openvpn['tls_dh'] and openvpn['tls_dh'] != 'none':
                print('Warning: using dh-file and EC keys simultaneously will lead to DH ciphers being used instead of ECDH')
            else:
                print('Diffie-Hellman prime file is unspecified, assuming ECDH')

    #
    # Auth user/pass
    #
    if openvpn['auth']:
        if not openvpn['auth_user']:
            raise ConfigError('Username for authentication is missing')

        if not openvpn['auth_pass']:
            raise ConfigError('Password for authentication is missing')

    return None

def generate(openvpn):
    interface = openvpn['intf']
    directory = os.path.dirname(get_config_name(interface))

    # we can't know in advance which clients have been removed,
    # thus all client configs will be removed and re-added on demand
    ccd_dir = os.path.join(directory, 'ccd', interface)
    if os.path.isdir(ccd_dir):
        rmtree(ccd_dir, ignore_errors=True)

    if openvpn['deleted'] or openvpn['disable']:
        return None

    # create config directory on demand
    directories = []
    directories.append(f'{directory}/status')
    directories.append(f'{directory}/ccd/{interface}')
    for onedir in directories:
        if not os.path.exists(onedir):
            os.makedirs(onedir, 0o755)
        chown(onedir, user, group)

    # Fix file permissons for keys
    fix_permissions = []
    fix_permissions.append(openvpn['shared_secret_file'])
    fix_permissions.append(openvpn['tls_key'])

    # Generate User/Password authentication file
    if openvpn['auth']:
        with open(openvpn['auth_user_pass_file'], 'w') as f:
            f.write('{}\n{}'.format(openvpn['auth_user'], openvpn['auth_pass']))
        # also change permission on auth file
        fix_permissions.append(openvpn['auth_user_pass_file'])

    else:
        # delete old auth file if present
        if os.path.isfile(openvpn['auth_user_pass_file']):
            os.remove(openvpn['auth_user_pass_file'])

    # Generate client specific configuration
    for client in openvpn['client']:
        client_file = os.path.join(ccd_dir, client['name'])
        render(client_file, 'openvpn/client.conf.tmpl', client)
        chown(client_file, user, group)

    # we need to support quoting of raw parameters from OpenVPN CLI
    # see https://phabricator.vyos.net/T1632
    render(get_config_name(interface), 'openvpn/server.conf.tmpl', openvpn,
           formater=lambda _: _.replace("&quot;", '"'))
    chown(get_config_name(interface), user, group)

    # Fixup file permissions
    for file in fix_permissions:
        chmod_600(file)

    return None

def apply(openvpn):
    interface = openvpn['intf']
    call(f'systemctl stop openvpn@{interface}.service')

    # Do some cleanup when OpenVPN is disabled/deleted
    if openvpn['deleted'] or openvpn['disable']:
        # cleanup old configuration files
        cleanup = []
        cleanup.append(get_config_name(interface))
        cleanup.append(openvpn['auth_user_pass_file'])

        for file in cleanup:
            if os.path.isfile(file):
                os.unlink(file)

        return None

    # On configuration change we need to wait for the 'old' interface to
    # vanish from the Kernel, if it is not gone, OpenVPN will report:
    # ERROR: Cannot ioctl TUNSETIFF vtun10: Device or resource busy (errno=16)
    while interface in interfaces():
        sleep(0.250) # 250ms

    # No matching OpenVPN process running - maybe it got killed or none
    # existed - nevertheless, spawn new OpenVPN process
    call(f'systemctl start openvpn@{interface}.service')

    # better late then sorry ... but we can only set interface alias after
    # OpenVPN has been launched and created the interface
    cnt = 0
    while interface not in interfaces():
        # If VPN tunnel can't be established because the peer/server isn't
        # (temporarily) available, the vtun interface never becomes registered
        # with the kernel, and the commit would hang if there is no bail out
        # condition
        cnt += 1
        if cnt == 50:
            break

        # sleep 250ms
        sleep(0.250)

    try:
        # we need to catch the exception if the interface is not up due to
        # reason stated above
        o = VTunIf(interface)
        # update interface description used e.g. within SNMP
        o.set_alias(openvpn['description'])
        # IPv6 address autoconfiguration
        o.set_ipv6_autoconf(openvpn['ipv6_autoconf'])
        # IPv6 forwarding
        o.set_ipv6_forwarding(openvpn['ipv6_forwarding'])
        # IPv6 Duplicate Address Detection (DAD) tries
        o.set_ipv6_dad_messages(openvpn['ipv6_dup_addr_detect'])

        # IPv6 EUI-based addresses - only in TAP mode (TUN's have no MAC)
        # If MAC has changed, old EUI64 addresses won't get deleted,
        # but this isn't easy to solve, so leave them.
        # This is even more difficult as openvpn uses a random MAC for the
        # initial interface creation, unless set by 'lladdr'.
        # NOTE: right now the interface is always deleted. For future
        # compatibility when tap's are not deleted, leave the del_ in
        if openvpn['mode'] == 'tap':
            for addr in openvpn['ipv6_eui64_prefix_remove']:
                o.del_ipv6_eui64_address(addr)
            for addr in openvpn['ipv6_eui64_prefix']:
                o.add_ipv6_eui64_address(addr)

    except:
        pass

    # TAP interface needs to be brought up explicitly
    if openvpn['type'] == 'tap':
        if not openvpn['disable']:
            VTunIf(interface).set_admin_state('up')

    return None


if __name__ == '__main__':
    try:
        c = get_config()
        verify(c)
        generate(c)
        apply(c)
    except ConfigError as e:
        print(e)
        exit(1)