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nat.py
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#!/usr/bin/env python3
#
# Copyright (C) 2020-2022 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 jmespath
import json
import os
from distutils.version import LooseVersion
from platform import release as kernel_version
from sys import exit
from netifaces import interfaces
from vyos.base import Warning
from vyos.config import Config
from vyos.configdict import dict_merge
from vyos.template import render
from vyos.template import is_ip_network
from vyos.util import cmd
from vyos.util import run
from vyos.util import check_kmod
from vyos.util import dict_search
from vyos.util import dict_search_args
from vyos.validate import is_addr_assigned
from vyos.xml import defaults
from vyos import ConfigError
from vyos import airbag
airbag.enable()
if LooseVersion(kernel_version()) > LooseVersion('5.1'):
k_mod = ['nft_nat', 'nft_chain_nat']
else:
k_mod = ['nft_nat', 'nft_chain_nat_ipv4']
nftables_nat_config = '/run/nftables_nat.conf'
nftables_static_nat_conf = '/run/nftables_static-nat-rules.nft'
valid_groups = [
'address_group',
'domain_group',
'network_group',
'port_group'
]
def get_handler(json, chain, target):
""" Get nftable rule handler number of given chain/target combination.
Handler is required when adding NAT/Conntrack helper targets """
for x in json:
if x['chain'] != chain:
continue
if x['target'] != target:
continue
return x['handle']
return None
def verify_rule(config, err_msg, groups_dict):
""" Common verify steps used for both source and destination NAT """
if (dict_search('translation.port', config) != None or
dict_search('destination.port', config) != None or
dict_search('source.port', config)):
if config['protocol'] not in ['tcp', 'udp', 'tcp_udp']:
raise ConfigError(f'{err_msg}\n' \
'ports can only be specified when protocol is '\
'either tcp, udp or tcp_udp!')
if is_ip_network(dict_search('translation.address', config)):
raise ConfigError(f'{err_msg}\n' \
'Cannot use ports with an IPv4 network as translation address as it\n' \
'statically maps a whole network of addresses onto another\n' \
'network of addresses')
for side in ['destination', 'source']:
if side in config:
side_conf = config[side]
if len({'address', 'fqdn'} & set(side_conf)) > 1:
raise ConfigError('Only one of address, fqdn or geoip can be specified')
if 'group' in side_conf:
if len({'address_group', 'network_group', 'domain_group'} & set(side_conf['group'])) > 1:
raise ConfigError('Only one address-group, network-group or domain-group can be specified')
for group in valid_groups:
if group in side_conf['group']:
group_name = side_conf['group'][group]
error_group = group.replace("_", "-")
if group in ['address_group', 'network_group', 'domain_group']:
types = [t for t in ['address', 'fqdn'] if t in side_conf]
if types:
raise ConfigError(f'{error_group} and {types[0]} cannot both be defined')
if group_name and group_name[0] == '!':
group_name = group_name[1:]
group_obj = dict_search_args(groups_dict, group, group_name)
if group_obj is None:
raise ConfigError(f'Invalid {error_group} "{group_name}" on firewall rule')
if not group_obj:
Warning(f'{error_group} "{group_name}" has no members!')
if dict_search_args(side_conf, 'group', 'port_group'):
if 'protocol' not in config:
raise ConfigError('Protocol must be defined if specifying a port-group')
if config['protocol'] not in ['tcp', 'udp', 'tcp_udp']:
raise ConfigError('Protocol must be tcp, udp, or tcp_udp when specifying a port-group')
def get_config(config=None):
if config:
conf = config
else:
conf = Config()
base = ['nat']
nat = conf.get_config_dict(base, key_mangling=('-', '_'), get_first_key=True)
# T2665: we must add the tagNode defaults individually until this is
# moved to the base class
for direction in ['source', 'destination', 'static']:
if direction in nat:
default_values = defaults(base + [direction, 'rule'])
for rule in dict_search(f'{direction}.rule', nat) or []:
nat[direction]['rule'][rule] = dict_merge(default_values,
nat[direction]['rule'][rule])
# read in current nftable (once) for further processing
tmp = cmd('nft -j list table raw')
nftable_json = json.loads(tmp)
# condense the full JSON table into a list with only relevand informations
pattern = 'nftables[?rule].rule[?expr[].jump].{chain: chain, handle: handle, target: expr[].jump.target | [0]}'
condensed_json = jmespath.search(pattern, nftable_json)
if not conf.exists(base):
if get_handler(condensed_json, 'PREROUTING', 'VYOS_CT_HELPER'):
nat['helper_functions'] = 'remove'
# Retrieve current table handler positions
nat['pre_ct_ignore'] = get_handler(condensed_json, 'PREROUTING', 'VYOS_CT_HELPER')
nat['pre_ct_conntrack'] = get_handler(condensed_json, 'PREROUTING', 'NAT_CONNTRACK')
nat['out_ct_ignore'] = get_handler(condensed_json, 'OUTPUT', 'VYOS_CT_HELPER')
nat['out_ct_conntrack'] = get_handler(condensed_json, 'OUTPUT', 'NAT_CONNTRACK')
nat['deleted'] = ''
return nat
nat['firewall_group'] = conf.get_config_dict(['firewall', 'group'], key_mangling=('-', '_'), get_first_key=True,
no_tag_node_value_mangle=True)
# check if NAT connection tracking helpers need to be set up - this has to
# be done only once
if not get_handler(condensed_json, 'PREROUTING', 'NAT_CONNTRACK'):
nat['helper_functions'] = 'add'
# Retrieve current table handler positions
nat['pre_ct_ignore'] = get_handler(condensed_json, 'PREROUTING', 'VYOS_CT_IGNORE')
nat['pre_ct_conntrack'] = get_handler(condensed_json, 'PREROUTING', 'VYOS_CT_PREROUTING_HOOK')
nat['out_ct_ignore'] = get_handler(condensed_json, 'OUTPUT', 'VYOS_CT_IGNORE')
nat['out_ct_conntrack'] = get_handler(condensed_json, 'OUTPUT', 'VYOS_CT_OUTPUT_HOOK')
return nat
def verify(nat):
if not nat or 'deleted' in nat:
# no need to verify the CLI as NAT is going to be deactivated
return None
if 'helper_functions' in nat:
if not (nat['pre_ct_ignore'] or nat['pre_ct_conntrack'] or nat['out_ct_ignore'] or nat['out_ct_conntrack']):
raise Exception('could not determine nftable ruleset handlers')
if dict_search('source.rule', nat):
for rule, config in dict_search('source.rule', nat).items():
err_msg = f'Source NAT configuration error in rule {rule}:'
if 'outbound_interface' not in config:
raise ConfigError(f'{err_msg} outbound-interface not specified')
if config['outbound_interface'] not in 'any' and config['outbound_interface'] not in interfaces():
Warning(f'rule "{rule}" interface "{config["outbound_interface"]}" does not exist on this system')
if not dict_search('translation.address', config) and not dict_search('translation.port', config):
if 'exclude' not in config:
raise ConfigError(f'{err_msg} translation requires address and/or port')
addr = dict_search('translation.address', config)
if addr != None and addr != 'masquerade' and not is_ip_network(addr):
for ip in addr.split('-'):
if not is_addr_assigned(ip):
Warning(f'IP address {ip} does not exist on the system!')
# common rule verification
verify_rule(config, err_msg, nat['firewall_group'])
if dict_search('destination.rule', nat):
for rule, config in dict_search('destination.rule', nat).items():
err_msg = f'Destination NAT configuration error in rule {rule}:'
if 'inbound_interface' not in config:
raise ConfigError(f'{err_msg}\n' \
'inbound-interface not specified')
elif config['inbound_interface'] not in 'any' and config['inbound_interface'] not in interfaces():
Warning(f'rule "{rule}" interface "{config["inbound_interface"]}" does not exist on this system')
if not dict_search('translation.address', config) and not dict_search('translation.port', config):
if 'exclude' not in config:
raise ConfigError(f'{err_msg} translation requires address and/or port')
# common rule verification
verify_rule(config, err_msg, nat['firewall_group'])
if dict_search('static.rule', nat):
for rule, config in dict_search('static.rule', nat).items():
err_msg = f'Static NAT configuration error in rule {rule}:'
if 'inbound_interface' not in config:
raise ConfigError(f'{err_msg}\n' \
'inbound-interface not specified')
# common rule verification
verify_rule(config, err_msg, nat['firewall_group'])
return None
def generate(nat):
if not os.path.exists(nftables_nat_config):
nat['first_install'] = True
render(nftables_nat_config, 'firewall/nftables-nat.j2', nat)
render(nftables_static_nat_conf, 'firewall/nftables-static-nat.j2', nat)
# dry-run newly generated configuration
tmp = run(f'nft -c -f {nftables_nat_config}')
if tmp > 0:
raise ConfigError('Configuration file errors encountered!')
tmp = run(f'nft -c -f {nftables_static_nat_conf}')
if tmp > 0:
raise ConfigError('Configuration file errors encountered!')
return None
def apply(nat):
cmd(f'nft -f {nftables_nat_config}')
cmd(f'nft -f {nftables_static_nat_conf}')
if not nat or 'deleted' in nat:
os.unlink(nftables_nat_config)
os.unlink(nftables_static_nat_conf)
return None
if __name__ == '__main__':
try:
check_kmod(k_mod)
c = get_config()
verify(c)
generate(c)
apply(c)
except ConfigError as e:
print(e)
exit(1)

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