dn42-scripts/asn-dns.py

#!/usr/bin/env python
# Maintained at https://code.ffdn.org/zorun/dn42-scripts

"""This script generates DNS TXT records containing ASN information.

The idea comes from asn.cymru.com.  Example:

  dig +short AS1.asn.cymru.com TXT

The output looks like this:

  "1 | US | arin | 2001-09-20 | LVLT-1 - Level 3 Communications, Inc."

In dn42, we try to respect this format. Fields 2 and 3 are set to "DN42"
and "dn42", respectively.  The date field is left empty, as we currently
do not record this information in the registry. For the last field, we use
"[as-name] [descr]" from the registry.

"""

import sys
import time
import argparse

from registry import AutNum

def gen_zone(args):
    out = args.output
    # SOA and stuff
    out.write("$ORIGIN {}\n".format(args.zone))
    out.write("$TTL {}\n".format(args.ttl))
    serial = int(time.time())
    out.write("@ IN SOA {0.ns[0]} {0.rname} "
              "({1} {0.refresh} {0.retry} {0.expire} {0.negative})\n".format(args,
                                                                             serial))
    # NS
    for ns in args.ns:
        out.write("@ NS {}\n".format(ns))

    # TXT data
    autnum = AutNum(args.registry)
    for (asn, data) in autnum.data.items():
        comment = ""
        if "as-name" in data:
            comment = data["as-name"][0]
            if "descr" in data:
                comment += " " + data["descr"][0]
        comment.replace('"', '')
        # Bind and NSD are quite happy with UTF-8 in TXT records, but
        # KnotDNS isn't (at least Knot 1.4.7).  This is a hack to work around this.
        comment = comment.encode('ascii', errors='xmlcharrefreplace').decode()
        out.write('{} TXT "{} | DN42 | dn42 |  | {}"\n'.format(asn, asn[2:], comment))

def cleanup(args):
    def final_dot(s):
        if not s.endswith('.'):
            return s + "."
        else:
            return s
    args.zone = final_dot(args.zone)
    args.rname = args.rname.replace("@", ".")
    args.rname = final_dot(args.rname)
    for (i, ns) in enumerate(args.ns):
        args.ns[i] = final_dot(ns)


if __name__ == "__main__":
    parser = argparse.ArgumentParser(description=__doc__)
    parser.add_argument("-n", "--ns", action="append", required=True,
                        help="name server, can be passed multiple times (the first one will be listed as master in the SOA)")
    parser.add_argument("-r", "--rname", required=True,
                        help="contact email of the administrator of the zone")
    parser.add_argument("-o", "--output", default=sys.stdout, type=argparse.FileType('w'),
                        help="output file (default: stdout)")
    parser.add_argument("registry", help="path to the monotone registry")
    opt = parser.add_argument_group("Zone options")
    opt.add_argument("-z", "--zone", default="asn.dn42.",
                     help="zone to generate data for (default: %(default)s)")
    opt.add_argument("-t", "--ttl", default="1h",
                     help="TTL for all records (default: %(default)s)")
    opt.add_argument("--refresh", default="1d",
                     help="refresh timer for slaves (default: %(default)s)")
    opt.add_argument("--retry", default="1h",
                     help="retry timer for slaves (default: %(default)s)")
    opt.add_argument("--expire", default="4w",
                     help="expire time for slaves (default: %(default)s)")
    opt.add_argument("--negative", default="5m",
                     help="negative TTL (default: %(default)s)")
    args = parser.parse_args()
    # Sanity checks
    cleanup(args)
    gen_zone(args)