#!/usr/bin/env python3 # # Unix SMB/CIFS implementation. # Copyright (C) Volker Lendecke 2017 # # This program is free software; you can redistribute it and/or modify # it under the terms of the GNU General Public License as published by # the Free Software Foundation; either version 3 of the License, or # (at your option) any later version. # # 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 . # # Used by selftest to proxy DNS queries to the correct testenv DC. # See selftest/target/README for more details. # Based on the EchoServer example from python docs import threading import sys import select import socket import collections import time from samba.dcerpc import dns import samba.ndr as ndr import socketserver sserver = socketserver DNS_REQUEST_TIMEOUT = 10 # make sure the script dies immediately when hitting control-C, # rather than raising KeyboardInterrupt. As we do all database # operations using transactions, this is safe. import signal signal.signal(signal.SIGINT, signal.SIG_DFL) class DnsHandler(sserver.BaseRequestHandler): dns_qtype_strings = dict((v, k) for k, v in vars(dns).items() if k.startswith('DNS_QTYPE_')) def dns_qtype_string(self, qtype): "Return a readable qtype code" return self.dns_qtype_strings[qtype] dns_rcode_strings = dict((v, k) for k, v in vars(dns).items() if k.startswith('DNS_RCODE_')) def dns_rcode_string(self, rcode): "Return a readable error code" return self.dns_rcode_strings[rcode] def dns_transaction_udp(self, packet, host): "send a DNS query and read the reply" s = None flags = socket.AddressInfo.AI_NUMERICHOST flags |= socket.AddressInfo.AI_NUMERICSERV flags |= socket.AddressInfo.AI_PASSIVE addr_info = socket.getaddrinfo(host, int(53), type=socket.SocketKind.SOCK_DGRAM, flags=flags) assert len(addr_info) == 1 try: send_packet = ndr.ndr_pack(packet) s = socket.socket(addr_info[0][0], addr_info[0][1], 0) s.settimeout(DNS_REQUEST_TIMEOUT) s.connect(addr_info[0][4]) s.sendall(send_packet, 0) recv_packet = s.recv(2048, 0) return ndr.ndr_unpack(dns.name_packet, recv_packet) except socket.error as err: print("Error sending to host %s for name %s: %s\n" % (host, packet.questions[0].name, err.errno)) raise finally: if s is not None: s.close() def get_pdc_ipv4_addr(self, lookup_name): """Maps a DNS realm to the IPv4 address of the PDC for that testenv""" realm_to_ip_mappings = self.server.realm_to_ip_mappings # sort the realms so we find the longest-match first testenv_realms = sorted(realm_to_ip_mappings.keys(), key=len) testenv_realms.reverse() for realm in testenv_realms: if lookup_name.endswith(realm): # return the corresponding IP address for this realm's PDC return realm_to_ip_mappings[realm] return None def forwarder(self, name): lname = name.lower() # check for special cases used by tests (e.g. dns_forwarder.py) if lname.endswith('an-address-that-will-not-resolve'): return 'ignore' if lname.endswith('dsfsdfs'): return 'fail' if lname.endswith("torture1", 0, len(lname)-2): # CATCH TORTURE100, TORTURE101, ... return 'torture' if lname.endswith('_none_.example.com'): return 'torture' if lname.endswith('torturedom.samba.example.com'): return 'torture' # return the testenv PDC matching the realm being requested return self.get_pdc_ipv4_addr(lname) def handle(self): start = time.monotonic() data, sock = self.request query = ndr.ndr_unpack(dns.name_packet, data) name = query.questions[0].name forwarder = self.forwarder(name) response = None if forwarder == 'ignore': return elif forwarder == 'fail': pass elif forwarder in ['torture', None]: response = query response.operation |= dns.DNS_FLAG_REPLY response.operation |= dns.DNS_FLAG_RECURSION_AVAIL response.operation |= dns.DNS_RCODE_NXDOMAIN else: try: response = self.dns_transaction_udp(query, forwarder) except OSError as err: print("dns_hub: Error sending dns query to forwarder[%s] for name[%s]: %s" % (forwarder, name, err)) if response is None: response = query response.operation |= dns.DNS_FLAG_REPLY response.operation |= dns.DNS_FLAG_RECURSION_AVAIL response.operation |= dns.DNS_RCODE_SERVFAIL send_packet = ndr.ndr_pack(response) end = time.monotonic() tdiff = end - start errcode = response.operation & dns.DNS_RCODE if tdiff > (DNS_REQUEST_TIMEOUT/5): debug = True else: debug = False if debug: print("dns_hub: forwarder[%s] client[%s] name[%s][%s] %s response.operation[0x%x] tdiff[%s]\n" % (forwarder, self.client_address, name, self.dns_qtype_string(query.questions[0].question_type), self.dns_rcode_string(errcode), response.operation, tdiff)) try: sock.sendto(send_packet, self.client_address) except socket.error as err: print("dns_hub: Error sending response to client[%s] for name[%s] tdiff[%s]: %s\n" % (self.client_address, name, tdiff, err)) class server_thread(threading.Thread): def __init__(self, server, name): threading.Thread.__init__(self, name=name) self.server = server def run(self): print("dns_hub[%s]: before serve_forever()" % self.name) self.server.serve_forever() print("dns_hub[%s]: after serve_forever()" % self.name) def stop(self): print("dns_hub[%s]: before shutdown()" % self.name) self.server.shutdown() print("dns_hub[%s]: after shutdown()" % self.name) self.server.server_close() class UDPV4Server(sserver.UDPServer): address_family = socket.AF_INET class UDPV6Server(sserver.UDPServer): address_family = socket.AF_INET6 def main(): if len(sys.argv) < 4: print("Usage: dns_hub.py TIMEOUT LISTENADDRESS[,LISTENADDRESS,...] MAPPING[,MAPPING,...]") sys.exit(1) timeout = int(sys.argv[1]) * 1000 timeout = min(timeout, 2**31 - 1) # poll with 32-bit int can't take more # we pass in the listen addresses as a comma-separated string. listenaddresses = sys.argv[2].split(',') # we pass in the realm-to-IP mappings as a comma-separated key=value # string. Convert this back into a dictionary that the DnsHandler can use realm_mappings = collections.OrderedDict(kv.split('=') for kv in sys.argv[3].split(',')) def prepare_server_thread(listenaddress, realm_mappings): flags = socket.AddressInfo.AI_NUMERICHOST flags |= socket.AddressInfo.AI_NUMERICSERV flags |= socket.AddressInfo.AI_PASSIVE addr_info = socket.getaddrinfo(listenaddress, int(53), type=socket.SocketKind.SOCK_DGRAM, flags=flags) assert len(addr_info) == 1 if addr_info[0][0] == socket.AddressFamily.AF_INET6: server = UDPV6Server(addr_info[0][4], DnsHandler) else: server = UDPV4Server(addr_info[0][4], DnsHandler) # we pass in the realm-to-IP mappings as a comma-separated key=value # string. Convert this back into a dictionary that the DnsHandler can use server.realm_to_ip_mappings = realm_mappings t = server_thread(server, name="UDP[%s]" % listenaddress) return t print("dns_hub will proxy DNS requests for the following realms:") for realm, ip in realm_mappings.items(): print(" {0} ==> {1}".format(realm, ip)) print("dns_hub will listen on the following UDP addresses:") threads = [] for listenaddress in listenaddresses: print(" %s" % listenaddress) t = prepare_server_thread(listenaddress, realm_mappings) threads.append(t) for t in threads: t.start() p = select.poll() stdin = sys.stdin.fileno() p.register(stdin, select.POLLIN) p.poll(timeout) print("dns_hub: after poll()") for t in threads: t.stop() for t in threads: t.join() print("dns_hub: before exit()") sys.exit(0) main()