selftest/target/dns_hub.py

   1 #!/usr/bin/env python
   2 #
   3 # Unix SMB/CIFS implementation.
   4 # Copyright (C) Volker Lendecke 2017
   5 #
   6 # This program is free software; you can redistribute it and/or modify
   7 # it under the terms of the GNU General Public License as published by
   8 # the Free Software Foundation; either version 3 of the License, or
   9 # (at your option) any later version.
  10 #
  11 # This program is distributed in the hope that it will be useful,
  12 # but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14 # GNU General Public License for more details.
  15 #
  16 # You should have received a copy of the GNU General Public License
  17 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
  18 #
  19 # Used by selftest to proxy DNS queries to the correct testenv DC.
  20 # See selftest/target/README for more details.
  21 # Based on the EchoServer example from python docs
  22
  23 import threading
  24 import sys
  25 import select
  26 import socket
  27 import time
  28 from samba.dcerpc import dns
  29 import samba.ndr as ndr
  30
  31 if sys.version_info[0] < 3:
  32     import SocketServer
  33     sserver = SocketServer
  34 else:
  35     import socketserver
  36     sserver = socketserver
  37
  38 DNS_REQUEST_TIMEOUT = 10
  39
  40
  41 class DnsHandler(sserver.BaseRequestHandler):
  42     dns_qtype_strings = dict((v, k) for k, v in vars(dns).items() if k.startswith('DNS_QTYPE_'))
  43     def dns_qtype_string(self, qtype):
  44         "Return a readable qtype code"
  45         return self.dns_qtype_strings[qtype]
  46
  47     dns_rcode_strings = dict((v, k) for k, v in vars(dns).items() if k.startswith('DNS_RCODE_'))
  48     def dns_rcode_string(self, rcode):
  49         "Return a readable error code"
  50         return self.dns_rcode_strings[rcode]
  51
  52     def dns_transaction_udp(self, packet, host):
  53         "send a DNS query and read the reply"
  54         s = None
  55         try:
  56             send_packet = ndr.ndr_pack(packet)
  57             s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM, 0)
  58             s.settimeout(DNS_REQUEST_TIMEOUT)
  59             s.connect((host, 53))
  60             s.sendall(send_packet, 0)
  61             recv_packet = s.recv(2048, 0)
  62             return ndr.ndr_unpack(dns.name_packet, recv_packet)
  63         except socket.error as err:
  64             print("Error sending to host %s for name %s: %s\n" %
  65                   (host, packet.questions[0].name, err.errno))
  66             raise
  67         finally:
  68             if s is not None:
  69                 s.close()
  70         return None
  71
  72     def forwarder(self, name):
  73         lname = name.lower()
  74
  75         if lname.endswith('an-address-that-will-not-resolve'):
  76             return 'ignore'
  77         if lname.endswith('dsfsdfs'):
  78             return 'fail'
  79         if lname.endswith("torture1", 0, len(lname)-2):
  80             # CATCH TORTURE100, TORTURE101, ...
  81             return 'torture'
  82         if lname.endswith('_none_.example.com'):
  83             return 'torture'
  84         if lname.endswith('torturedom.samba.example.com'):
  85             return 'torture'
  86         if lname.endswith('adnonssdom.samba.example.com'):
  87             return '127.0.0.17'
  88         if lname.endswith('adnontlmdom.samba.example.com'):
  89             return '127.0.0.18'
  90         if lname.endswith('samba2000.example.com'):
  91             return '127.0.0.25'
  92         if lname.endswith('samba2003.example.com'):
  93             return '127.0.0.26'
  94         if lname.endswith('samba2008r2.example.com'):
  95             return '127.0.0.27'
  96         if lname.endswith('addom.samba.example.com'):
  97             return '127.0.0.30'
  98         if lname.endswith('sub.samba.example.com'):
  99             return '127.0.0.31'
 100         if lname.endswith('chgdcpassword.samba.example.com'):
 101             return '127.0.0.32'
 102         if lname.endswith('backupdom.samba.example.com'):
 103             return '127.0.0.40'
 104         if lname.endswith('renamedom.samba.example.com'):
 105             return '127.0.0.42'
 106         if lname.endswith('labdom.samba.example.com'):
 107             return '127.0.0.43'
 108         if lname.endswith('samba.example.com'):
 109             return '127.0.0.21'
 110         return None
 111
 112     def handle(self):
 113         start = time.monotonic()
 114         data, sock = self.request
 115         query = ndr.ndr_unpack(dns.name_packet, data)
 116         name = query.questions[0].name
 117         forwarder = self.forwarder(name)
 118         response = None
 119
 120         if forwarder is 'ignore':
 121             return
 122         elif forwarder is 'fail':
 123             pass
 124         elif forwarder in ['torture', None]:
 125             response = query
 126             response.operation |= dns.DNS_FLAG_REPLY
 127             response.operation |= dns.DNS_FLAG_RECURSION_AVAIL
 128             response.operation |= dns.DNS_RCODE_NXDOMAIN
 129         else:
 130             response = self.dns_transaction_udp(query, forwarder)
 131
 132         if response is None:
 133             response = query
 134             response.operation |= dns.DNS_FLAG_REPLY
 135             response.operation |= dns.DNS_FLAG_RECURSION_AVAIL
 136             response.operation |= dns.DNS_RCODE_SERVFAIL
 137
 138         send_packet = ndr.ndr_pack(response)
 139
 140         end = time.monotonic()
 141         tdiff = end - start
 142         errcode = response.operation & dns.DNS_RCODE
 143         if tdiff > (DNS_REQUEST_TIMEOUT/5):
 144             debug = True
 145         else:
 146             debug = False
 147         if debug:
 148             print("dns_hub: forwarder[%s] client[%s] name[%s][%s] %s response.operation[0x%x] tdiff[%s]\n" %
 149                 (forwarder, self.client_address, name,
 150                  self.dns_qtype_string(query.questions[0].question_type),
 151                  self.dns_rcode_string(errcode), response.operation, tdiff))
 152
 153         try:
 154             sock.sendto(send_packet, self.client_address)
 155         except socket.error as err:
 156             print("dns_hub: Error sending response to client[%s] for name[%s] tdiff[%s]: %s\n" %
 157                 (self.client_address, name, tdiff, err))
 158
 159
 160 class server_thread(threading.Thread):
 161     def __init__(self, server):
 162         threading.Thread.__init__(self)
 163         self.server = server
 164
 165     def run(self):
 166         self.server.serve_forever()
 167         print("dns_hub: after serve_forever()")
 168
 169
 170 def main():
 171     timeout = int(sys.argv[1]) * 1000
 172     timeout = min(timeout, 2**31 - 1)  # poll with 32-bit int can't take more
 173     host = sys.argv[2]
 174     server = sserver.UDPServer((host, int(53)), DnsHandler)
 175     t = server_thread(server)
 176     t.start()
 177     p = select.poll()
 178     stdin = sys.stdin.fileno()
 179     p.register(stdin, select.POLLIN)
 180     p.poll(timeout)
 181     print("dns_hub: after poll()")
 182     server.shutdown()
 183     t.join()
 184     print("dns_hub: before exit()")
 185     sys.exit(0)
 186
 187 main()