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#!/usr/bin/env python3
import time
from contextlib import contextmanager
import re
import os
import os.path
import random
import string
import subprocess
import sqlite3
import hmac
from ipaddress import IPv4Address, IPv6Address
from flask import Flask, request, abort
import uwsgidecorators
app = Flask(__name__)
app.config.update(dict(
RECORD_EXPIRY_S = 86400,
NSD_CONTROL = 'nsd-control'
))
app.config.from_pyfile('config.py')
ZONEFILE_TEMPLATE = '''\
; #################################################### ;
; THIS FILE IS AUTOMATICALLY GENERATED! DO NOT MODIFY! ;
; #################################################### ;
$ORIGIN {zone}.
$TTL 1800
@ IN SOA {ns}. {mail}. (
{serial} ; serial number
60 ; refresh
60 ; retry
{expire} ; expire
60 ; ttl
)
; Name servers
IN NS {ns}.
; Additional A records from template
; @ IN A 192.0.2.3
; www IN A 192.0.2.3
; Dynamically generated records
{dynamic_records}
'''
db = sqlite3.connect(app.config['SQLITE_DB'], check_same_thread=False)
with db as conn:
conn.execute('''CREATE TABLE IF NOT EXISTS zone_versions (date TEXT)''')
conn.execute('''CREATE TABLE IF NOT EXISTS records
(name TEXT PRIMARY KEY, ipv4 TEXT, ipv6 TEXT, last_update INTEGER)''')
def purge_expired_records():
with db as conn:
conn.execute('DELETE FROM records WHERE last_update < ?',
(int(time.time()) - app.config['RECORD_EXPIRY_S'],))
def update_record(record, ipv4=None, ipv6=None):
with db as conn:
old_v4, old_v6 = conn.execute('SELECT ipv4, ipv6 FROM records WHERE name=?', (record,)).fetchone() or (None, None)
conn.execute('INSERT OR REPLACE INTO records VALUES (?, ?, ?, ?)', (record, ipv4, ipv6, int(time.time())))
return ipv4 != old_v4 or ipv6 != old_v6
@contextmanager
def inplace_rewrite(filename, cleanup=True):
print('Writing', filename)
filename = os.path.abspath(filename)
if cleanup:
basename = os.path.basename(filename)
for entry in os.scandir(os.path.dirname(filename)):
if entry.name.startswith(basename) and re.match(r'\.tmp-[a-zA-Z0-9]{8}', entry.name[len(basename):]):
os.remove(entry.path)
tmp_fn = filename + f'.tmp-' + ''.join(random.choices(string.ascii_letters + string.digits, k=8))
with open(tmp_fn, 'w') as tmp_f:
yield tmp_f
tmp_f.flush()
os.fsync(tmp_f.fileno())
os.rename(tmp_fn, filename)
def write_zonefile():
# Find the next free zonefile version number
with db as conn:
conn.execute('INSERT INTO zone_versions VALUES (DATE())')
date, version_num, = conn.execute('SELECT zone_versions.date, COUNT(*) FROM zone_versions WHERE zone_versions.date = DATE()').fetchone()
zone_version = f'{date.replace("-", "")}{version_num:02d}'
# Generate dynamic record block
with db as conn:
records = db.execute('SELECT name, "A", ipv4 FROM records UNION SELECT name, "AAAA", ipv6 FROM records')
dynamic_records = '\n'.join(f'{name:<20} IN {rtype:<4} {value}' for name, rtype, value in records if value is not None)
# Template zone file content
content = ZONEFILE_TEMPLATE.format(
zone = app.config['ZONE'],
ns = app.config['NAMESERVER'],
mail = app.config['NAMESERVER_MAIL'].replace('@', '.'),
serial = zone_version,
dynamic_records = dynamic_records,
expire = app.config['RECORD_EXPIRY_S']
)
with inplace_rewrite(app.config['ZONEFILE'], cleanup=True) as f:
f.write(content)
def kick_nsd():
prog = app.config['NSD_CONTROL']
if isinstance(prog, str):
prog = [prog]
subprocess.run([*prog, 'reload', app.config['ZONE']], check=True)
@app.before_first_request
@uwsgidecorators.timer(300)
def update_zonefile():
purge_expired_records()
write_zonefile()
kick_nsd()
@app.route('/update', methods=['POST'])
def route_update():
if request.authorization is None:
abort(403)
record = request.authorization['username']
record_config = app.config['DYNAMIC_RECORDS'].get(record)
if record_config is None:
abort(403)
*supported_formats, password = record_config
if not hmac.compare_digest(request.authorization['password'], password):
abort(403)
ipv4 = request.args.get('ipv4', '127.0.0.1')
ipv6 = request.args.get('ipv6', '::1')
ipv4 = str(IPv4Address(ipv4)) if 'v4' in supported_formats else None
ipv6 = str(IPv6Address(ipv6)) if 'v6' in supported_formats else None
if update_record(record, ipv4=ipv4, ipv6=ipv6):
update_zonefile()
return 'success'
if __name__ == '__main__':
app.run()
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