#!/usr/bin/env python3 # # Copyright (C) 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 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.config import Config from vyos.configdict import dict_merge from vyos.template import render from vyos.util import cmd from vyos.util import check_kmod from vyos.util import dict_search 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'] iptables_nat_config = '/tmp/vyos-nat-rules.nft' 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): """ 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 '/' in (dict_search('translation.address', config) or []): raise ConfigError(f'{err_msg}\n' \ 'Cannot use ports with an IPv4net type translation address as it\n' \ 'statically maps a whole network of addresses onto another\n' \ 'network of addresses') 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']: 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): nat['helper_functions'] = 'remove' # Retrieve current table handler positions nat['pre_ct_ignore'] = get_handler(condensed_json, 'PREROUTING', 'VYATTA_CT_HELPER') nat['pre_ct_conntrack'] = get_handler(condensed_json, 'PREROUTING', 'NAT_CONNTRACK') nat['out_ct_ignore'] = get_handler(condensed_json, 'OUTPUT', 'VYATTA_CT_HELPER') nat['out_ct_conntrack'] = get_handler(condensed_json, 'OUTPUT', 'NAT_CONNTRACK') nat['deleted'] = '' return nat # 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', 'VYATTA_CT_IGNORE') nat['pre_ct_conntrack'] = get_handler(condensed_json, 'PREROUTING', 'VYATTA_CT_PREROUTING_HOOK') nat['out_ct_ignore'] = get_handler(condensed_json, 'OUTPUT', 'VYATTA_CT_IGNORE') nat['out_ct_conntrack'] = get_handler(condensed_json, 'OUTPUT', 'VYATTA_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}\n' \ 'outbound-interface not specified') else: if config['outbound_interface'] not in 'any' and config['outbound_interface'] not in interfaces(): print(f'WARNING: rule "{rule}" interface "{config["outbound_interface"]}" does not exist on this system') addr = dict_search('translation.address', config) if addr != None: if addr != 'masquerade': for ip in addr.split('-'): if not is_addr_assigned(ip): print(f'WARNING: IP address {ip} does not exist on the system!') elif 'exclude' not in config: raise ConfigError(f'{err_msg}\n' \ 'translation address not specified') # common rule verification verify_rule(config, err_msg) 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') else: if config['inbound_interface'] not in 'any' and config['inbound_interface'] not in interfaces(): print(f'WARNING: rule "{rule}" interface "{config["inbound_interface"]}" does not exist on this system') if dict_search('translation.address', config) == None and 'exclude' not in config: raise ConfigError(f'{err_msg}\n' \ 'translation address not specified') # common rule verification verify_rule(config, err_msg) return None def generate(nat): render(iptables_nat_config, 'firewall/nftables-nat.tmpl', nat, permission=0o755) return None def apply(nat): cmd(f'{iptables_nat_config}') if os.path.isfile(iptables_nat_config): os.unlink(iptables_nat_config) 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)