wgsd-client

#!/usr/bin/env python3
# Copyright (C) 2021 Luca Filipozzi <luca.filipozzi@gmail.com>
#
# This Source Code Form is subject to the terms of the Mozilla Public
# License, v. 2.0.  If a copy of the MPL was not distributed with this
# file, You can obtain one at http://mozilla.org/MPL/2.0/.
#
# This Source Code Form is "Incompatible With Secondary Licenses", as
# defined by the Mozilla Public License, v. 2.0.
#
#
# This Source Code Form (hereafter 'program') implements a 'client'
# for DNS-based Service Discovery (DNS-SD; RFC 6763 [1]) that extracts
# data from PTR+SRV+TXT records relating to wireguard nodes.
#
#
# usage: wgsd-client --domain example.com
#
#
# [1]: https://tools.ietf.org/html/rfc6763


import click
import dns.resolver
try:
    from dns.resolver import resolve as query
except ImportError:
    from dns.resolver import query as query
import munch


@click.command()
@click.option('--domain', type=str, required=True)
def main(domain):
    nodes = []

    # for each target in the PTR record
    ptr_answer = query(f'_wireguard._udp.{domain}', 'PTR')
    for ptr_target in [x.target for x in ptr_answer]:
        node = munch.Munch()

        # fetch the SRV record to obtain the UDP port
        srv_answer = query(ptr_target, 'SRV')
        if len(srv_answer) != 1:
            raise Exception('incorrect number of SRV records')
        node.port = srv_answer[0].port
        node.target = srv_answer[0].target

        # fetch the TXT record to obtain the public key
        txt_answer = query(node.target, 'TXT')
        if len(txt_answer) != 1:
            raise Exception('incorrect number of TXT records')
        node.update(munch.Munch(x.decode('utf-8').split('=', 1) for x in txt_answer[0].strings))
        if node.txtvers != '1':
            raise Exception('unknown version')

        # fetch the A record to obtain the IPv4 address
        a_answer = query(node.target, 'A')
        if len(a_answer) != 1:
            raise Exception('incorrect number of A records')
        node.address = a_answer[0].address

        nodes.append(node)

    for node in nodes:
        print(f'{node.pub} {node.port} {node.target} {node.address}')


if __name__ == '__main__':
    main()