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
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
|
#!/usr/bin/perl
#
# Copyright (C) Internet Systems Consortium, Inc. ("ISC")
#
# 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 http://mozilla.org/MPL/2.0/.
#
# See the COPYRIGHT file distributed with this work for additional
# information regarding copyright ownership.
#
# This is the name server from hell. It provides canned
# responses based on pattern matching the queries, and
# can be reprogrammed on-the-fly over a TCP connection.
#
# The server listens for control connections on port 5301.
# A control connection is a TCP stream of lines like
#
# /pattern/
# name ttl type rdata
# name ttl type rdata
# ...
# /pattern/
# name ttl type rdata
# name ttl type rdata
# ...
#
# There can be any number of patterns, each associated
# with any number of response RRs. Each pattern is a
# Perl regular expression.
#
# Each incoming query is converted into a string of the form
# "qname qtype" (the printable query domain name, space,
# printable query type) and matched against each pattern.
#
# The first pattern matching the query is selected, and
# the RR following the pattern line are sent in the
# answer section of the response.
#
# Each new control connection causes the current set of
# patterns and responses to be cleared before adding new
# ones.
#
# The server handles UDP and TCP queries. Zone transfer
# responses work, but must fit in a single 64 k message.
#
# Now you can add TSIG, just specify key/key data with:
#
# /pattern <key> <key_data>/
# name ttl type rdata
# name ttl type rdata
#
# Note that this data will still be sent with any request for
# pattern, only this data will be signed. Currently, this is only
# done for TCP.
use IO::File;
use IO::Socket;
use Data::Dumper;
use Net::DNS;
use Net::DNS::Packet;
use strict;
# Ignore SIGPIPE so we won't fail if peer closes a TCP socket early
local $SIG{PIPE} = 'IGNORE';
# Flush logged output after every line
local $| = 1;
my $server_addr = "10.53.0.4";
my $localport = int($ENV{'PORT'});
if (!$localport) { $localport = 5300; }
my $udpsock = IO::Socket::INET->new(LocalAddr => "$server_addr",
LocalPort => $localport, Proto => "udp", Reuse => 1) or die "$!";
my $tcpsock = IO::Socket::INET->new(LocalAddr => "$server_addr",
LocalPort => $localport, Proto => "tcp", Listen => 5, Reuse => 1) or die "$!";
print "listening on $server_addr:$localport.\n";
my $pidf = new IO::File "ans.pid", "w" or die "cannot open pid file: $!";
print $pidf "$$\n" or die "cannot write pid file: $!";
$pidf->close or die "cannot close pid file: $!";;
sub rmpid { unlink "ans.pid"; exit 1; };
$SIG{INT} = \&rmpid;
$SIG{TERM} = \&rmpid;
#my @answers = ();
my @rules;
sub handleUDP {
my ($buf) = @_;
my $packet;
if ($Net::DNS::VERSION > 0.68) {
$packet = new Net::DNS::Packet(\$buf, 0);
$@ and die $@;
} else {
my $err;
($packet, $err) = new Net::DNS::Packet(\$buf, 0);
$err and die $err;
}
$packet->header->qr(1);
$packet->header->aa(1);
my @questions = $packet->question;
my $qname = $questions[0]->qname;
my $qtype = $questions[0]->qtype;
# get the existing signature if any, and clear the additional section
my $prev_tsig;
while (my $rr = $packet->pop("additional")) {
if ($rr->type eq "TSIG") {
$prev_tsig = $rr;
}
}
my $r;
foreach $r (@rules) {
my $pattern = $r->{pattern};
my($dbtype, $key_name, $key_data) = split(/ /,$pattern);
print "[handleUDP] $dbtype, $key_name, $key_data \n";
if ("$qname $qtype" =~ /$dbtype/) {
my $a;
foreach $a (@{$r->{answer}}) {
$packet->push("answer", $a);
}
if(defined($key_name) && defined($key_data)) {
# Sign the packet
print " Signing the response with " .
"$key_name/$key_data\n";
my $tsig = Net::DNS::RR->
new("$key_name TSIG $key_data");
# These kluges are necessary because Net::DNS
# doesn't know how to sign responses. We
# clear compnames so that the TSIG key and
# algorithm name won't be compressed, and
# add one to arcount because the signing
# function will attempt to decrement it,
# which is incorrect in a response. Finally
# we set request_mac to the previous digest.
$packet->{"compnames"} = {};
$packet->{"header"}{"arcount"} += 1;
if (defined($prev_tsig)) {
my $rmac = pack('n H*',
$prev_tsig->mac_size,
$prev_tsig->mac);
$tsig->{"request_mac"} =
unpack("H*", $rmac);
}
$packet->sign_tsig($tsig);
}
last;
}
}
#$packet->print;
return $packet->data;
}
# namelen:
# given a stream of data, reads a DNS-formatted name and returns its
# total length, thus making it possible to skip past it.
sub namelen {
my ($data) = @_;
my $len = 0;
my $label_len = 0;
do {
$label_len = unpack("c", $data);
$data = substr($data, $label_len + 1);
$len += $label_len + 1;
} while ($label_len != 0);
return ($len);
}
# packetlen:
# given a stream of data, reads a DNS wire-format packet and returns
# its total length, making it possible to skip past it.
sub packetlen {
my ($data) = @_;
my $q;
my $rr;
my ($header, $offset) = Net::DNS::Header->parse(\$data);
for (1 .. $header->qdcount) {
($q, $offset) = Net::DNS::Question->parse(\$data, $offset);
}
for (1 .. $header->ancount) {
($rr, $offset) = Net::DNS::RR->parse(\$data, $offset);
}
for (1 .. $header->nscount) {
($rr, $offset) = Net::DNS::RR->parse(\$data, $offset);
}
for (1 .. $header->arcount) {
($rr, $offset) = Net::DNS::RR->parse(\$data, $offset);
}
return $offset;
}
# sign_tcp_continuation:
# This is a hack to correct the problem that Net::DNS has no idea how
# to sign multiple-message TCP responses. Several data that are included
# in the digest when signing a query or the first message of a response are
# omitted when signing subsequent messages in a TCP stream.
#
# Net::DNS::Packet->sign_tsig() has the ability to use a custom signing
# function (specified by calling Packet->sign_func()). We use this
# function as the signing function for TCP continuations, and it removes
# the unwanted data from the digest before calling the default sign_hmac
# function.
sub sign_tcp_continuation {
my ($key, $data) = @_;
# copy out first two bytes: size of the previous MAC
my $rmacsize = unpack("n", $data);
$data = substr($data, 2);
# copy out previous MAC
my $rmac = substr($data, 0, $rmacsize);
$data = substr($data, $rmacsize);
# try parsing out the packet information
my $plen = packetlen($data);
my $pdata = substr($data, 0, $plen);
$data = substr($data, $plen);
# remove the keyname, ttl, class, and algorithm name
$data = substr($data, namelen($data));
$data = substr($data, 6);
$data = substr($data, namelen($data));
# preserve the TSIG data
my $tdata = substr($data, 0, 8);
# prepare a new digest and sign with it
$data = pack("n", $rmacsize) . $rmac . $pdata . $tdata;
return Net::DNS::RR::TSIG::sign_hmac($key, $data);
}
sub handleTCP {
my ($buf) = @_;
my $packet;
if ($Net::DNS::VERSION > 0.68) {
$packet = new Net::DNS::Packet(\$buf, 0);
$@ and die $@;
} else {
my $err;
($packet, $err) = new Net::DNS::Packet(\$buf, 0);
$err and die $err;
}
$packet->header->qr(1);
$packet->header->aa(1);
my @questions = $packet->question;
my $qname = $questions[0]->qname;
my $qtype = $questions[0]->qtype;
# get the existing signature if any, and clear the additional section
my $prev_tsig;
my $signer;
while (my $rr = $packet->pop("additional")) {
if ($rr->type eq "TSIG") {
$prev_tsig = $rr;
}
}
my @results = ();
my $count_these = 0;
my $r;
foreach $r (@rules) {
my $pattern = $r->{pattern};
my($dbtype, $key_name, $key_data) = split(/ /,$pattern);
print "[handleTCP] $dbtype, $key_name, $key_data \n";
if ("$qname $qtype" =~ /$dbtype/) {
$count_these++;
my $a;
foreach $a (@{$r->{answer}}) {
$packet->push("answer", $a);
}
if(defined($key_name) && defined($key_data)) {
# sign the packet
print " Signing the data with " .
"$key_name/$key_data\n";
my $tsig = Net::DNS::RR->
new("$key_name TSIG $key_data");
# These kluges are necessary because Net::DNS
# doesn't know how to sign responses. We
# clear compnames so that the TSIG key and
# algorithm name won't be compressed, and
# add one to arcount because the signing
# function will attempt to decrement it,
# which is incorrect in a response. Finally
# we set request_mac to the previous digest.
$packet->{"compnames"} = {};
$packet->{"header"}{"arcount"} += 1;
if (defined($prev_tsig)) {
my $rmac = pack('n H*',
$prev_tsig->mac_size,
$prev_tsig->mac);
$tsig->{"request_mac"} =
unpack("H*", $rmac);
}
$tsig->sign_func($signer) if defined($signer);
$packet->sign_tsig($tsig);
$signer = \&sign_tcp_continuation;
my $copy =
Net::DNS::Packet->new(\($packet->data));
$prev_tsig = $copy->pop("additional");
}
#$packet->print;
push(@results,$packet->data);
$packet = new Net::DNS::Packet(\$buf, 0);
$packet->header->qr(1);
$packet->header->aa(1);
}
}
print " A total of $count_these patterns matched\n";
return \@results;
}
# Main
my $rin;
my $rout;
for (;;) {
$rin = '';
vec($rin, fileno($tcpsock), 1) = 1;
vec($rin, fileno($udpsock), 1) = 1;
select($rout = $rin, undef, undef, undef);
if (vec($rout, fileno($udpsock), 1)) {
printf "UDP request\n";
my $buf;
$udpsock->recv($buf, 512);
} elsif (vec($rout, fileno($tcpsock), 1)) {
my $conn = $tcpsock->accept;
my $buf;
for (;;) {
my $lenbuf;
my $n = $conn->sysread($lenbuf, 2);
last unless $n == 2;
my $len = unpack("n", $lenbuf);
$n = $conn->sysread($buf, $len);
}
sleep(1);
}
}
|