1# Copyright (C) Internet Systems Consortium, Inc. ("ISC")
2#
3# SPDX-License-Identifier: MPL-2.0
4#
5# This Source Code Form is subject to the terms of the Mozilla Public
6# License, v. 2.0.  If a copy of the MPL was not distributed with this
7# file, you can obtain one at https://mozilla.org/MPL/2.0/.
8#
9# See the COPYRIGHT file distributed with this work for additional
10# information regarding copyright ownership.
11
12from __future__ import print_function
13import os
14import sys
15import signal
16import socket
17import select
18from datetime import datetime, timedelta
19import time
20import functools
21
22import dns, dns.message, dns.query, dns.flags
23from dns.rdatatype import *
24from dns.rdataclass import *
25from dns.rcode import *
26from dns.name import *
27
28
29# Log query to file
30def logquery(type, qname):
31    with open("qlog", "a") as f:
32        f.write("%s %s\n", type, qname)
33
34def endswith(domain, labels):
35    return domain.endswith("." + labels) or domain == labels
36
37############################################################################
38# Respond to a DNS query.
39# For good. it serves:
40# ns2.good. IN A 10.53.0.2
41# zoop.boing.good. NS ns3.good.
42# ns3.good. IN A 10.53.0.3
43# too.many.labels.a.b.c.d.e.f.g.h.i.j.k.l.m.n.o.p.q.r.s.t.u.v.w.x.y.z.good. A 192.0.2.2
44# it responds properly (with NODATA empty response) to non-empty terminals
45#
46# For slow. it works the same as for good., but each response is delayed by 400 milliseconds
47#
48# For bad. it works the same as for good., but returns NXDOMAIN to non-empty terminals
49#
50# For ugly. it works the same as for good., but returns garbage to non-empty terminals
51#
52# For 1.0.0.2.ip6.arpa it serves
53# 1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.8.f.4.0.1.0.0.2.ip6.arpa. IN PTR nee.com.
54# 8.2.6.0.1.0.0.2.ip6.arpa IN NS ns3.good
55# 1.0.0.2.ip6.arpa. IN NS ns2.good
56# ip6.arpa. IN NS ns2.good
57#
58# For stale. it serves:
59# a.b. NS ns.a.b.stale.
60# ns.a.b.stale. IN A 10.53.0.3
61# b. NS ns.b.stale.
62# ns.b.stale. IN A 10.53.0.4
63############################################################################
64def create_response(msg):
65    m = dns.message.from_wire(msg)
66    qname = m.question[0].name.to_text()
67    lqname = qname.lower()
68    labels = lqname.split('.')
69
70    # get qtype
71    rrtype = m.question[0].rdtype
72    typename = dns.rdatatype.to_text(rrtype)
73    if typename == "A" or typename == "AAAA":
74        typename = "ADDR"
75    bad = False
76    ugly = False
77    slow = False
78
79    # log this query
80    with open("query.log", "a") as f:
81        f.write("%s %s\n" % (typename, lqname))
82        print("%s %s" % (typename, lqname), end=" ")
83
84    r = dns.message.make_response(m)
85    r.set_rcode(NOERROR)
86
87    if endswith(lqname, "1.0.0.2.ip6.arpa."):
88        # Direct query - give direct answer
89        if endswith(lqname, "8.2.6.0.1.0.0.2.ip6.arpa."):
90            # Delegate to ns3
91            r.authority.append(dns.rrset.from_text("8.2.6.0.1.0.0.2.ip6.arpa.", 60, IN, NS, "ns3.good."))
92            r.additional.append(dns.rrset.from_text("ns3.good.", 60, IN, A, "10.53.0.3"))
93        elif lqname == "1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.8.f.4.0.1.0.0.2.ip6.arpa." and rrtype == PTR:
94            # Direct query - give direct answer
95            r.answer.append(dns.rrset.from_text("1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.8.f.4.0.1.0.0.2.ip6.arpa.", 1, IN, PTR, "nee.com."))
96            r.flags |= dns.flags.AA
97        elif lqname == "1.0.0.2.ip6.arpa." and rrtype == NS:
98            # NS query at the apex
99            r.answer.append(dns.rrset.from_text("1.0.0.2.ip6.arpa.", 30, IN, NS, "ns2.good."))
100            r.flags |= dns.flags.AA
101        elif endswith("1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.8.f.4.0.1.0.0.2.ip6.arpa.", lqname):
102            # NODATA answer
103            r.authority.append(dns.rrset.from_text("1.0.0.2.ip6.arpa.", 30, IN, SOA, "ns2.good. hostmaster.arpa. 2018050100 1 1 1 1"))
104        else:
105            # NXDOMAIN
106            r.authority.append(dns.rrset.from_text("1.0.0.2.ip6.arpa.", 30, IN, SOA, "ns2.good. hostmaster.arpa. 2018050100 1 1 1 1"))
107            r.set_rcode(NXDOMAIN)
108        return r
109    elif endswith(lqname, "ip6.arpa."):
110        if lqname == "ip6.arpa." and rrtype == NS:
111            # NS query at the apex
112            r.answer.append(dns.rrset.from_text("ip6.arpa.", 30, IN, NS, "ns2.good."))
113            r.flags |= dns.flags.AA
114        elif endswith("1.0.0.2.ip6.arpa.", lqname):
115            # NODATA answer
116            r.authority.append(dns.rrset.from_text("ip6.arpa.", 30, IN, SOA, "ns2.good. hostmaster.arpa. 2018050100 1 1 1 1"))
117        else:
118            # NXDOMAIN
119            r.authority.append(dns.rrset.from_text("ip6.arpa.", 30, IN, SOA, "ns2.good. hostmaster.arpa. 2018050100 1 1 1 1"))
120            r.set_rcode(NXDOMAIN)
121        return r
122    elif endswith(lqname, "stale."):
123        if endswith(lqname, "a.b.stale."):
124            # Delegate to ns.a.b.stale.
125            r.authority.append(dns.rrset.from_text("a.b.stale.", 2, IN, NS, "ns.a.b.stale."))
126            r.additional.append(dns.rrset.from_text("ns.a.b.stale.", 2, IN, A, "10.53.0.3"))
127        elif endswith(lqname, "b.stale."):
128            # Delegate to ns.b.stale.
129            r.authority.append(dns.rrset.from_text("b.stale.", 2, IN, NS, "ns.b.stale."))
130            r.additional.append(dns.rrset.from_text("ns.b.stale.", 2, IN, A, "10.53.0.4"))
131        elif lqname == "stale." and rrtype == NS:
132            # NS query at the apex.
133            r.answer.append(dns.rrset.from_text("stale.", 2, IN, NS, "ns2.stale."))
134            r.flags |= dns.flags.AA
135        elif lqname == "stale." and rrtype == SOA:
136            # SOA query at the apex.
137            r.answer.append(dns.rrset.from_text("stale.", 2, IN, SOA, "ns2.stale. hostmaster.stale. 1 2 3 4 5"))
138            r.flags |= dns.flags.AA
139        elif lqname == "stale.":
140            # NODATA answer
141            r.authority.append(dns.rrset.from_text("stale.", 2, IN, SOA, "ns2.stale. hostmaster.arpa. 1 2 3 4 5"))
142        else:
143            # NXDOMAIN
144            r.authority.append(dns.rrset.from_text("stale.", 2, IN, SOA, "ns2.stale. hostmaster.arpa. 1 2 3 4 5"))
145            r.set_rcode(NXDOMAIN)
146        return r
147    elif endswith(lqname, "bad."):
148        bad = True
149        suffix = "bad."
150        lqname = lqname[:-4]
151    elif endswith(lqname, "ugly."):
152        ugly = True
153        suffix = "ugly."
154        lqname = lqname[:-5]
155    elif endswith(lqname, "good."):
156        suffix = "good."
157        lqname = lqname[:-5]
158    elif endswith(lqname, "slow."):
159        slow = True
160        suffix = "slow."
161        lqname = lqname[:-5]
162    elif endswith(lqname, "fwd."):
163        suffix = "fwd."
164        lqname = lqname[:-4]
165    else:
166        r.set_rcode(REFUSED)
167        return r
168
169    # Good/bad/ugly differs only in how we treat non-empty terminals
170    if endswith(lqname, "zoop.boing."):
171        r.authority.append(dns.rrset.from_text("zoop.boing." + suffix, 1, IN, NS, "ns3." + suffix))
172    elif lqname == "many.labels.a.b.c.d.e.f.g.h.i.j.k.l.m.n.o.p.q.r.s.t.u.v.w.x.y.z." and rrtype == A:
173        r.answer.append(dns.rrset.from_text(lqname + suffix, 1, IN, A, "192.0.2.2"))
174        r.flags |= dns.flags.AA
175    elif lqname == "" and rrtype == NS:
176        r.answer.append(dns.rrset.from_text(suffix, 30, IN, NS, "ns2." + suffix))
177        r.flags |= dns.flags.AA
178    elif lqname == "ns2." and rrtype == A:
179        r.answer.append(dns.rrset.from_text("ns2."+suffix, 30, IN, A, "10.53.0.2"))
180        r.flags |= dns.flags.AA
181    elif lqname == "ns2." and rrtype == AAAA:
182        r.answer.append(dns.rrset.from_text("ns2."+suffix, 30, IN, AAAA, "fd92:7065:b8e:ffff::2"))
183        r.flags |= dns.flags.AA
184    elif lqname == "ns3." and rrtype == A:
185        r.answer.append(dns.rrset.from_text("ns3."+suffix, 30, IN, A, "10.53.0.3"))
186        r.flags |= dns.flags.AA
187    elif lqname == "ns3." and rrtype == AAAA:
188        r.answer.append(dns.rrset.from_text("ns3."+suffix, 30, IN, AAAA, "fd92:7065:b8e:ffff::3"))
189        r.flags |= dns.flags.AA
190    elif lqname == "ns4." and rrtype == A:
191        r.answer.append(dns.rrset.from_text("ns4."+suffix, 30, IN, A, "10.53.0.4"))
192        r.flags |= dns.flags.AA
193    elif lqname == "ns4." and rrtype == AAAA:
194        r.answer.append(dns.rrset.from_text("ns4."+suffix, 30, IN, AAAA, "fd92:7065:b8e:ffff::4"))
195        r.flags |= dns.flags.AA
196    elif lqname == "a.bit.longer.ns.name." and rrtype == A:
197        r.answer.append(dns.rrset.from_text("a.bit.longer.ns.name."+suffix, 1, IN, A, "10.53.0.4"))
198        r.flags |= dns.flags.AA
199    elif lqname == "a.bit.longer.ns.name." and rrtype == AAAA:
200        r.answer.append(dns.rrset.from_text("a.bit.longer.ns.name."+suffix, 1, IN, AAAA, "fd92:7065:b8e:ffff::4"))
201        r.flags |= dns.flags.AA
202    else:
203        r.authority.append(dns.rrset.from_text(suffix, 1, IN, SOA, "ns2." + suffix + " hostmaster.arpa. 2018050100 1 1 1 1"))
204        if bad or not \
205            (endswith("icky.icky.icky.ptang.zoop.boing.", lqname) or \
206             endswith("many.labels.a.b.c.d.e.f.g.h.i.j.k.l.m.n.o.p.q.r.s.t.u.v.w.x.y.z.", lqname) or \
207             endswith("a.bit.longer.ns.name.", lqname)):
208            r.set_rcode(NXDOMAIN)
209        if ugly:
210            r.set_rcode(FORMERR)
211    if slow:
212        time.sleep(0.2)
213    return r
214
215
216def sigterm(signum, frame):
217    print ("Shutting down now...")
218    os.remove('ans.pid')
219    running = False
220    sys.exit(0)
221
222############################################################################
223# Main
224#
225# Set up responder and control channel, open the pid file, and start
226# the main loop, listening for queries on the query channel or commands
227# on the control channel and acting on them.
228############################################################################
229ip4 = "10.53.0.2"
230ip6 = "fd92:7065:b8e:ffff::2"
231
232try: port=int(os.environ['PORT'])
233except: port=5300
234
235query4_socket = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
236query4_socket.bind((ip4, port))
237
238havev6 = True
239try:
240    query6_socket = socket.socket(socket.AF_INET6, socket.SOCK_DGRAM)
241    try:
242        query6_socket.bind((ip6, port))
243    except:
244        query6_socket.close()
245        havev6 = False
246except:
247    havev6 = False
248
249signal.signal(signal.SIGTERM, sigterm)
250
251f = open('ans.pid', 'w')
252pid = os.getpid()
253print (pid, file=f)
254f.close()
255
256running = True
257
258print ("Listening on %s port %d" % (ip4, port))
259if havev6:
260    print ("Listening on %s port %d" % (ip6, port))
261print ("Ctrl-c to quit")
262
263if havev6:
264    input = [query4_socket, query6_socket]
265else:
266    input = [query4_socket]
267
268while running:
269    try:
270        inputready, outputready, exceptready = select.select(input, [], [])
271    except select.error as e:
272        break
273    except socket.error as e:
274        break
275    except KeyboardInterrupt:
276        break
277
278    for s in inputready:
279        if s == query4_socket or s == query6_socket:
280            print ("Query received on %s" %
281                    (ip4 if s == query4_socket else ip6), end=" ")
282            # Handle incoming queries
283            msg = s.recvfrom(65535)
284            rsp = create_response(msg[0])
285            if rsp:
286                print(dns.rcode.to_text(rsp.rcode()))
287                s.sendto(rsp.to_wire(), msg[1])
288            else:
289                print("NO RESPONSE")
290    if not running:
291        break
292