Forked from andreif/Simple DNS server (UDP and TCP) in Python using dnslib.py
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August 18, 2024 14:28
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Simple DNS server (UDP and TCP) in Python using dnslib.py
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#!/usr/bin/env python | |
""" | |
LICENSE http://www.apache.org/licenses/LICENSE-2.0 | |
""" | |
import argparse | |
import datetime | |
import sys | |
import time | |
import threading | |
import traceback | |
import socketserver | |
import struct | |
try: | |
from dnslib import * | |
except ImportError: | |
print("Missing dependency dnslib: <https://pypi.python.org/pypi/dnslib>. Please install it with `pip`.") | |
sys.exit(2) | |
class DomainName(str): | |
def __getattr__(self, item): | |
return DomainName(item + '.' + self) | |
D = DomainName('example.com.') | |
IP = '127.0.0.1' | |
TTL = 60 * 5 | |
soa_record = SOA( | |
mname=D.ns1, # primary name server | |
rname=D.andrei, # email of the domain administrator | |
times=( | |
201307231, # serial number | |
60 * 60 * 1, # refresh | |
60 * 60 * 3, # retry | |
60 * 60 * 24, # expire | |
60 * 60 * 1, # minimum | |
) | |
) | |
ns_records = [NS(D.ns1), NS(D.ns2)] | |
records = { | |
D: [A(IP), AAAA((0,) * 16), MX(D.mail), soa_record] + ns_records, | |
D.ns1: [A(IP)], # MX and NS records must never point to a CNAME alias (RFC 2181 section 10.3) | |
D.ns2: [A(IP)], | |
D.mail: [A(IP)], | |
D.andrei: [CNAME(D)], | |
} | |
def dns_response(data): | |
request = DNSRecord.parse(data) | |
print(request) | |
reply = DNSRecord(DNSHeader(id=request.header.id, qr=1, aa=1, ra=1), q=request.q) | |
qname = request.q.qname | |
qn = str(qname) | |
qtype = request.q.qtype | |
qt = QTYPE[qtype] | |
if qn == D or qn.endswith('.' + D): | |
for name, rrs in records.items(): | |
if name == qn: | |
for rdata in rrs: | |
rqt = rdata.__class__.__name__ | |
if qt in ['*', rqt]: | |
reply.add_answer(RR(rname=qname, rtype=getattr(QTYPE, rqt), rclass=1, ttl=TTL, rdata=rdata)) | |
for rdata in ns_records: | |
reply.add_ar(RR(rname=D, rtype=QTYPE.NS, rclass=1, ttl=TTL, rdata=rdata)) | |
reply.add_auth(RR(rname=D, rtype=QTYPE.SOA, rclass=1, ttl=TTL, rdata=soa_record)) | |
print("---- Reply:\n", reply) | |
return reply.pack() | |
class BaseRequestHandler(socketserver.BaseRequestHandler): | |
def get_data(self): | |
raise NotImplementedError | |
def send_data(self, data): | |
raise NotImplementedError | |
def handle(self): | |
now = datetime.datetime.utcnow().strftime('%Y-%m-%d %H:%M:%S.%f') | |
print("\n\n%s request %s (%s %s):" % (self.__class__.__name__[:3], now, self.client_address[0], | |
self.client_address[1])) | |
try: | |
data = self.get_data() | |
print(len(data), data) # repr(data).replace('\\x', '')[1:-1] | |
self.send_data(dns_response(data)) | |
except Exception: | |
traceback.print_exc(file=sys.stderr) | |
class TCPRequestHandler(BaseRequestHandler): | |
def get_data(self): | |
data = self.request.recv(8192).strip() | |
sz = struct.unpack('>H', data[:2])[0] | |
if sz < len(data) - 2: | |
raise Exception("Wrong size of TCP packet") | |
elif sz > len(data) - 2: | |
raise Exception("Too big TCP packet") | |
return data[2:] | |
def send_data(self, data): | |
sz = struct.pack('>H', len(data)) | |
return self.request.sendall(sz + data) | |
class UDPRequestHandler(BaseRequestHandler): | |
def get_data(self): | |
return self.request[0].strip() | |
def send_data(self, data): | |
return self.request[1].sendto(data, self.client_address) | |
def main(): | |
parser = argparse.ArgumentParser(description='Start a DNS implemented in Python.') | |
parser = argparse.ArgumentParser(description='Start a DNS implemented in Python. Usually DNSs use UDP on port 53.') | |
parser.add_argument('--port', default=5053, type=int, help='The port to listen on.') | |
parser.add_argument('--tcp', action='store_true', help='Listen to TCP connections.') | |
parser.add_argument('--udp', action='store_true', help='Listen to UDP datagrams.') | |
args = parser.parse_args() | |
if not (args.udp or args.tcp): parser.error("Please select at least one of --udp or --tcp.") | |
print("Starting nameserver...") | |
servers = [] | |
if args.udp: servers.append(socketserver.ThreadingUDPServer(('', args.port), UDPRequestHandler)) | |
if args.tcp: servers.append(socketserver.ThreadingTCPServer(('', args.port), TCPRequestHandler)) | |
for s in servers: | |
thread = threading.Thread(target=s.serve_forever) # that thread will start one more thread for each request | |
thread.daemon = True # exit the server thread when the main thread terminates | |
thread.start() | |
print("%s server loop running in thread: %s" % (s.RequestHandlerClass.__name__[:3], thread.name)) | |
try: | |
while 1: | |
time.sleep(1) | |
sys.stderr.flush() | |
sys.stdout.flush() | |
except KeyboardInterrupt: | |
pass | |
finally: | |
for s in servers: | |
s.shutdown() | |
if __name__ == '__main__': | |
main() |
Nice man!!!
Can we make this support NAPTR query as well?
This code is great!!! Awesome!!!
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@kj7rrv thanks for your comment. andreif's original gist, has been re-licensed under the Apache license, so I updated this code here, too.
Alternatives:
What about checking out @samuelcolvin's comment including a hint to his software https://github.com/samuelcolvin/dnserver. This is licensed under the MIT license and loosely based on the ideas here.