1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
|
# Copyright (C) Internet Systems Consortium, Inc. ("ISC")
#
# SPDX-License-Identifier: MPL-2.0
#
# This Source Code Form is subject to the terms of the Mozilla Public
# License, v. 2.0. If a copy of the MPL was not distributed with this
# file, you can obtain one at https://mozilla.org/MPL/2.0/.
#
# See the COPYRIGHT file distributed with this work for additional
# information regarding copyright ownership.
from __future__ import print_function
import os
import sys
import signal
import socket
import select
import struct
from datetime import datetime, timedelta
import time
import functools
import dns, dns.message, dns.query, dns.flags
from dns.rdatatype import *
from dns.rdataclass import *
from dns.rcode import *
from dns.name import *
# Log query to file
def logquery(type, qname):
with open("qlog", "a") as f:
f.write("%s %s\n", type, qname)
# Create a UDP listener
def udp_listen(ip, port, is_ipv6=False):
try:
udp = socket.socket(
socket.AF_INET6 if is_ipv6 else socket.AF_INET, socket.SOCK_DGRAM
)
try:
udp.bind((ip, port))
except:
udp.close()
udp = None
except:
udp = None
if udp is None and not is_ipv6:
raise socket.error("Can not create an IPv4 UDP listener")
return udp
# Create a TCP listener
def tcp_listen(ip, port, is_ipv6=False):
try:
tcp = socket.socket(
socket.AF_INET6 if is_ipv6 else socket.AF_INET, socket.SOCK_STREAM
)
try:
tcp.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
tcp.bind((ip, port))
tcp.listen(100)
except:
tcp.close()
tcp = None
except:
tcp = None
if tcp is None and not is_ipv6:
raise socket.error("Can not create an IPv4 TCP listener")
return tcp
############################################################################
# Control channel - send "1" or "0" to enable or disable the "silent" mode.
############################################################################
silent = False
def ctrl_channel(msg):
global silent
msg = msg.splitlines().pop(0)
print("Received control message: %s" % msg)
if len(msg) != 1:
return
if silent:
if msg == b"0":
silent = False
print("Silent mode was disabled")
else:
if msg == b"1":
silent = True
print("Silent mode was enabled")
############################################################################
# Respond to a DNS query.
############################################################################
def create_response(msg):
m = dns.message.from_wire(msg)
qname = m.question[0].name.to_text()
rrtype = m.question[0].rdtype
typename = dns.rdatatype.to_text(rrtype)
with open("query.log", "a") as f:
f.write("%s %s\n" % (typename, qname))
print("%s %s" % (typename, qname), end=" ")
r = dns.message.make_response(m)
r.set_rcode(NOERROR)
if rrtype == A:
tld = qname.split(".")[-2] + "."
ns = "local." + tld
r.answer.append(dns.rrset.from_text(qname, 300, IN, A, "10.53.0.11"))
r.answer.append(dns.rrset.from_text(tld, 300, IN, NS, "local." + tld))
r.additional.append(dns.rrset.from_text(ns, 300, IN, A, "10.53.0.11"))
elif rrtype == NS:
r.answer.append(dns.rrset.from_text(qname, 300, IN, NS, "."))
elif rrtype == SOA:
r.answer.append(dns.rrset.from_text(qname, 300, IN, SOA, ". . 0 0 0 0 0"))
else:
r.authority.append(dns.rrset.from_text(qname, 300, IN, SOA, ". . 0 0 0 0 0"))
r.flags |= dns.flags.AA
return r
def sigterm(signum, frame):
print("Shutting down now...")
os.remove("ans.pid")
running = False
sys.exit(0)
############################################################################
# Main
#
# Set up responder and control channel, open the pid file, and start
# the main loop, listening for queries on the query channel or commands
# on the control channel and acting on them.
############################################################################
ip4 = "10.53.0.11"
ip6 = "fd92:7065:b8e:ffff::11"
try:
port = int(os.environ["PORT"])
except:
port = 5300
try:
ctrlport = int(os.environ["EXTRAPORT1"])
except:
ctrlport = 5300
ctrl4_tcp = tcp_listen(ip4, ctrlport)
query4_udp = udp_listen(ip4, port)
query6_udp = udp_listen(ip6, port, is_ipv6=True)
query4_tcp = tcp_listen(ip4, port)
query6_tcp = tcp_listen(ip6, port, is_ipv6=True)
havev6 = query6_udp is not None and query6_tcp is not None
signal.signal(signal.SIGTERM, sigterm)
f = open("ans.pid", "w")
pid = os.getpid()
print(pid, file=f)
f.close()
running = True
print("Listening on %s port %d" % (ip4, ctrlport))
print("Listening on %s port %d" % (ip4, port))
if havev6:
print("Listening on %s port %d" % (ip6, port))
print("Ctrl-c to quit")
if havev6:
input = [ctrl4_tcp, query4_udp, query6_udp, query4_tcp, query6_tcp]
else:
input = [ctrl4_tcp, query4_udp, query4_tcp]
hung_conns = []
while running:
try:
inputready, outputready, exceptready = select.select(input, [], [])
except select.error as e:
break
except socket.error as e:
break
except KeyboardInterrupt:
break
for s in inputready:
if s == ctrl4_tcp:
print("Control channel connected")
conn = None
try:
# Handle control channel input
conn, addr = s.accept()
msg = conn.recv(1)
if msg:
ctrl_channel(msg)
conn.close()
except s.timeout:
pass
if conn:
conn.close()
elif s == query4_tcp or s == query6_tcp:
print(
"TCP query received on %s" % (ip4 if s == query4_tcp else ip6), end=" "
)
conn = None
try:
# Handle incoming queries
conn, addr = s.accept()
if not silent:
# get TCP message length
msg = conn.recv(2)
if len(msg) != 2:
print("NO RESPONSE (can not read the message length)")
conn.close()
continue
length = struct.unpack(">H", msg[:2])[0]
msg = conn.recv(length)
if len(msg) != length:
print("NO RESPONSE (can not read the message)")
conn.close()
continue
rsp = create_response(msg)
if rsp:
print(dns.rcode.to_text(rsp.rcode()))
wire = rsp.to_wire()
conn.send(struct.pack(">H", len(wire)))
conn.send(wire)
else:
print("NO RESPONSE (can not create a response)")
else:
# Do not respond and hang the connection.
print("NO RESPONSE (silent mode)")
hung_conns.append(conn)
continue
except socket.error as e:
print("NO RESPONSE (error: %s)" % str(e))
if conn:
conn.close()
elif s == query4_udp or s == query6_udp:
print(
"UDP query received on %s" % (ip4 if s == query4_udp else ip6), end=" "
)
# Handle incoming queries
msg = s.recvfrom(65535)
if not silent:
rsp = create_response(msg[0])
if rsp:
print(dns.rcode.to_text(rsp.rcode()))
s.sendto(rsp.to_wire(), msg[1])
else:
print("NO RESPONSE (can not create a response)")
else:
# Do not respond.
print("NO RESPONSE (silent mode)")
if not running:
break
|
