1#!/usr/bin/perl 2 3# Copyright (C) Internet Systems Consortium, Inc. ("ISC") 4# 5# SPDX-License-Identifier: MPL-2.0 6# 7# This Source Code Form is subject to the terms of the Mozilla Public 8# License, v. 2.0. If a copy of the MPL was not distributed with this 9# file, you can obtain one at https://mozilla.org/MPL/2.0/. 10# 11# See the COPYRIGHT file distributed with this work for additional 12# information regarding copyright ownership. 13 14# 15# This is the name server from hell. It provides canned 16# responses based on pattern matching the queries, and 17# can be reprogrammed on-the-fly over a TCP connection. 18# 19# The server listens for queries on port 5300 (or PORT). 20# 21# The server listens for control connections on port 5301 (or EXTRAPORT1). 22# 23# A control connection is a TCP stream of lines like 24# 25# /pattern/ 26# name ttl type rdata 27# name ttl type rdata 28# ... 29# /pattern/ 30# name ttl type rdata 31# name ttl type rdata 32# ... 33# 34# There can be any number of patterns, each associated 35# with any number of response RRs. Each pattern is a 36# Perl regular expression. If an empty pattern ("//") is 37# received, the server will ignore all incoming queries (TCP 38# connections will still be accepted, but both UDP queries 39# and TCP queries will not be responded to). If a non-empty 40# pattern is then received over the same control connection, 41# default behavior is restored. 42# 43# Each incoming query is converted into a string of the form 44# "qname qtype" (the printable query domain name, space, 45# printable query type) and matched against each pattern. 46# 47# The first pattern matching the query is selected, and 48# the RR following the pattern line are sent in the 49# answer section of the response. 50# 51# Each new control connection causes the current set of 52# patterns and responses to be cleared before adding new 53# ones. 54# 55# The server handles UDP and TCP queries. Zone transfer 56# responses work, but must fit in a single 64 k message. 57# 58# Now you can add TSIG, just specify key/key data with: 59# 60# /pattern <key> <key_data>/ 61# name ttl type rdata 62# name ttl type rdata 63# 64# Note that this data will still be sent with any request for 65# pattern, only this data will be signed. Currently, this is only 66# done for TCP. 67# 68# /pattern bad-id <key> <key_data>/ 69# /pattern bad-id/ 70# 71# will add 50 to the message id of the response. 72 73 74use IO::File; 75use IO::Socket; 76use Data::Dumper; 77use Net::DNS; 78use Net::DNS::Packet; 79use strict; 80 81# Ignore SIGPIPE so we won't fail if peer closes a TCP socket early 82local $SIG{PIPE} = 'IGNORE'; 83 84# Flush logged output after every line 85local $| = 1; 86 87# We default to listening on 10.53.0.2 for historical reasons 88# XXX: we should also be able to specify IPv6 89my $server_addr = "10.53.0.2"; 90if (@ARGV > 0) { 91 $server_addr = @ARGV[0]; 92} 93 94my $mainport = int($ENV{'PORT'}); 95if (!$mainport) { $mainport = 5300; } 96my $ctrlport = int($ENV{'EXTRAPORT1'}); 97if (!$ctrlport) { $ctrlport = 5301; } 98 99# XXX: we should also be able to set the port numbers to listen on. 100my $ctlsock = IO::Socket::INET->new(LocalAddr => "$server_addr", 101 LocalPort => $ctrlport, Proto => "tcp", Listen => 5, Reuse => 1) or die "$!"; 102 103my $udpsock = IO::Socket::INET->new(LocalAddr => "$server_addr", 104 LocalPort => $mainport, Proto => "udp", Reuse => 1) or die "$!"; 105 106my $tcpsock = IO::Socket::INET->new(LocalAddr => "$server_addr", 107 LocalPort => $mainport, Proto => "tcp", Listen => 5, Reuse => 1) or die "$!"; 108 109print "listening on $server_addr:$mainport,$ctrlport.\n"; 110print "Using Net::DNS $Net::DNS::VERSION\n"; 111 112my $pidf = new IO::File "ans.pid", "w" or die "cannot open pid file: $!"; 113print $pidf "$$\n" or die "cannot write pid file: $!"; 114$pidf->close or die "cannot close pid file: $!";; 115sub rmpid { unlink "ans.pid"; exit 1; }; 116 117$SIG{INT} = \&rmpid; 118$SIG{TERM} = \&rmpid; 119 120#my @answers = (); 121my @rules; 122my $udphandler; 123my $tcphandler; 124 125sub handleUDP { 126 my ($buf) = @_; 127 my $request; 128 129 if ($Net::DNS::VERSION > 0.68) { 130 $request = new Net::DNS::Packet(\$buf, 0); 131 $@ and die $@; 132 } else { 133 my $err; 134 ($request, $err) = new Net::DNS::Packet(\$buf, 0); 135 $err and die $err; 136 } 137 138 my @questions = $request->question; 139 my $qname = $questions[0]->qname; 140 my $qtype = $questions[0]->qtype; 141 my $qclass = $questions[0]->qclass; 142 my $id = $request->header->id; 143 144 my $packet = new Net::DNS::Packet($qname, $qtype, $qclass); 145 $packet->header->qr(1); 146 $packet->header->aa(1); 147 $packet->header->id($id); 148 149 # get the existing signature if any, and clear the additional section 150 my $prev_tsig; 151 while (my $rr = $request->pop("additional")) { 152 $prev_tsig = $rr if ($rr->type eq "TSIG"); 153 } 154 155 my $r; 156 foreach $r (@rules) { 157 my $pattern = $r->{pattern}; 158 my($dbtype, $key_name, $key_data) = split(/ /,$pattern); 159 print "[handleUDP] $dbtype, $key_name, $key_data \n"; 160 if ("$qname $qtype" =~ /$dbtype/) { 161 my $a; 162 foreach $a (@{$r->{answer}}) { 163 $packet->push("answer", $a); 164 } 165 if(defined($key_name) && defined($key_data)) { 166 my $tsig; 167 # Sign the packet 168 print " Signing the response with " . 169 "$key_name/$key_data\n"; 170 171 if ($Net::DNS::VERSION < 0.69) { 172 $tsig = Net::DNS::RR->new( 173 "$key_name TSIG $key_data"); 174 } else { 175 $tsig = Net::DNS::RR->new( 176 name => $key_name, 177 type => 'TSIG', 178 key => $key_data); 179 } 180 181 # These kluges are necessary because Net::DNS 182 # doesn't know how to sign responses. We 183 # clear compnames so that the TSIG key and 184 # algorithm name won't be compressed, and 185 # add one to arcount because the signing 186 # function will attempt to decrement it, 187 # which is incorrect in a response. Finally 188 # we set request_mac to the previous digest. 189 $packet->{"compnames"} = {} 190 if ($Net::DNS::VERSION < 0.70); 191 $packet->{"header"}{"arcount"} += 1 192 if ($Net::DNS::VERSION < 0.70); 193 if (defined($prev_tsig)) { 194 if ($Net::DNS::VERSION < 0.73) { 195 my $rmac = pack('n H*', 196 length($prev_tsig->mac)/2, 197 $prev_tsig->mac); 198 $tsig->{"request_mac"} = 199 unpack("H*", $rmac); 200 } else { 201 $tsig->request_mac( 202 $prev_tsig->mac); 203 } 204 } 205 206 $packet->sign_tsig($tsig); 207 } 208 last; 209 } 210 } 211 #$packet->print; 212 213 return $packet->data; 214} 215 216# namelen: 217# given a stream of data, reads a DNS-formatted name and returns its 218# total length, thus making it possible to skip past it. 219sub namelen { 220 my ($data) = @_; 221 my $len = 0; 222 my $label_len = 0; 223 do { 224 $label_len = unpack("c", $data); 225 $data = substr($data, $label_len + 1); 226 $len += $label_len + 1; 227 } while ($label_len != 0); 228 return ($len); 229} 230 231# packetlen: 232# given a stream of data, reads a DNS wire-format packet and returns 233# its total length, making it possible to skip past it. 234sub packetlen { 235 my ($data) = @_; 236 my $q; 237 my $rr; 238 my $header; 239 my $offset; 240 241 # 242 # decode/encode were introduced in Net::DNS 0.68 243 # parse is no longer a method and calling it here makes perl croak. 244 # 245 my $decode = 0; 246 $decode = 1 if ($Net::DNS::VERSION >= 0.68); 247 248 if ($decode) { 249 ($header, $offset) = Net::DNS::Header->decode(\$data); 250 } else { 251 ($header, $offset) = Net::DNS::Header->parse(\$data); 252 } 253 254 for (1 .. $header->qdcount) { 255 if ($decode) { 256 ($q, $offset) = 257 Net::DNS::Question->decode(\$data, $offset); 258 } else { 259 ($q, $offset) = 260 Net::DNS::Question->parse(\$data, $offset); 261 } 262 } 263 for (1 .. $header->ancount) { 264 if ($decode) { 265 ($q, $offset) = Net::DNS::RR->decode(\$data, $offset); 266 } else { 267 ($q, $offset) = Net::DNS::RR->parse(\$data, $offset); 268 } 269 } 270 for (1 .. $header->nscount) { 271 if ($decode) { 272 ($q, $offset) = Net::DNS::RR->decode(\$data, $offset); 273 } else { 274 ($q, $offset) = Net::DNS::RR->parse(\$data, $offset); 275 } 276 } 277 for (1 .. $header->arcount) { 278 if ($decode) { 279 ($q, $offset) = Net::DNS::RR->decode(\$data, $offset); 280 } else { 281 ($q, $offset) = Net::DNS::RR->parse(\$data, $offset); 282 } 283 } 284 return $offset; 285} 286 287# sign_tcp_continuation: 288# This is a hack to correct the problem that Net::DNS has no idea how 289# to sign multiple-message TCP responses. Several data that are included 290# in the digest when signing a query or the first message of a response are 291# omitted when signing subsequent messages in a TCP stream. 292# 293# Net::DNS::Packet->sign_tsig() has the ability to use a custom signing 294# function (specified by calling Packet->sign_func()). We use this 295# function as the signing function for TCP continuations, and it removes 296# the unwanted data from the digest before calling the default sign_hmac 297# function. 298sub sign_tcp_continuation { 299 my ($key, $data) = @_; 300 301 # copy out first two bytes: size of the previous MAC 302 my $rmacsize = unpack("n", $data); 303 $data = substr($data, 2); 304 305 # copy out previous MAC 306 my $rmac = substr($data, 0, $rmacsize); 307 $data = substr($data, $rmacsize); 308 309 # try parsing out the packet information 310 my $plen = packetlen($data); 311 my $pdata = substr($data, 0, $plen); 312 $data = substr($data, $plen); 313 314 # remove the keyname, ttl, class, and algorithm name 315 $data = substr($data, namelen($data)); 316 $data = substr($data, 6); 317 $data = substr($data, namelen($data)); 318 319 # preserve the TSIG data 320 my $tdata = substr($data, 0, 8); 321 322 # prepare a new digest and sign with it 323 $data = pack("n", $rmacsize) . $rmac . $pdata . $tdata; 324 return Net::DNS::RR::TSIG::sign_hmac($key, $data); 325} 326 327sub handleTCP { 328 my ($buf) = @_; 329 my $request; 330 331 if ($Net::DNS::VERSION > 0.68) { 332 $request = new Net::DNS::Packet(\$buf, 0); 333 $@ and die $@; 334 } else { 335 my $err; 336 ($request, $err) = new Net::DNS::Packet(\$buf, 0); 337 $err and die $err; 338 } 339 340 my @questions = $request->question; 341 my $qname = $questions[0]->qname; 342 my $qtype = $questions[0]->qtype; 343 my $qclass = $questions[0]->qclass; 344 my $id = $request->header->id; 345 346 my $opaque; 347 348 my $packet = new Net::DNS::Packet($qname, $qtype, $qclass); 349 $packet->header->qr(1); 350 $packet->header->aa(1); 351 $packet->header->id($id); 352 353 # get the existing signature if any, and clear the additional section 354 my $prev_tsig; 355 my $signer; 356 my $continuation = 0; 357 if ($Net::DNS::VERSION < 0.81) { 358 while (my $rr = $request->pop("additional")) { 359 if ($rr->type eq "TSIG") { 360 $prev_tsig = $rr; 361 } 362 } 363 } 364 365 my @results = (); 366 my $count_these = 0; 367 368 my $r; 369 foreach $r (@rules) { 370 my $pattern = $r->{pattern}; 371 my($dbtype, $key_name, $key_data, $extra) = split(/ /,$pattern); 372 print "[handleTCP] $dbtype, $key_name, $key_data \n"; 373 if ("$qname $qtype" =~ /$dbtype/) { 374 $count_these++; 375 my $a; 376 foreach $a (@{$r->{answer}}) { 377 $packet->push("answer", $a); 378 } 379 if(defined($key_name) && $key_name eq "bad-id") { 380 $packet->header->id(($id+50)%0xffff); 381 $key_name = $key_data; 382 $key_data = $extra; 383 } 384 if (defined($key_name) && defined($key_data)) { 385 my $tsig; 386 # sign the packet 387 print " Signing the data with " . 388 "$key_name/$key_data\n"; 389 390 if ($Net::DNS::VERSION < 0.69) { 391 $tsig = Net::DNS::RR->new( 392 "$key_name TSIG $key_data"); 393 } elsif ($Net::DNS::VERSION >= 0.81 && 394 $continuation) { 395 } elsif ($Net::DNS::VERSION >= 0.75 && 396 $continuation) { 397 $tsig = $prev_tsig; 398 } else { 399 $tsig = Net::DNS::RR->new( 400 name => $key_name, 401 type => 'TSIG', 402 key => $key_data); 403 } 404 405 # These kluges are necessary because Net::DNS 406 # doesn't know how to sign responses. We 407 # clear compnames so that the TSIG key and 408 # algorithm name won't be compressed, and 409 # add one to arcount because the signing 410 # function will attempt to decrement it, 411 # which is incorrect in a response. Finally 412 # we set request_mac to the previous digest. 413 $packet->{"compnames"} = {} 414 if ($Net::DNS::VERSION < 0.70); 415 $packet->{"header"}{"arcount"} += 1 416 if ($Net::DNS::VERSION < 0.70); 417 if (defined($prev_tsig)) { 418 if ($Net::DNS::VERSION < 0.73) { 419 my $rmac = pack('n H*', 420 length($prev_tsig->mac)/2, 421 $prev_tsig->mac); 422 $tsig->{"request_mac"} = 423 unpack("H*", $rmac); 424 } elsif ($Net::DNS::VERSION < 0.81) { 425 $tsig->request_mac( 426 $prev_tsig->mac); 427 } 428 } 429 430 $tsig->sign_func($signer) if defined($signer); 431 $tsig->continuation($continuation) if 432 ($Net::DNS::VERSION >= 0.71 && 433 $Net::DNS::VERSION <= 0.74 ); 434 if ($Net::DNS::VERSION < 0.81) { 435 $packet->sign_tsig($tsig); 436 } elsif ($continuation) { 437 $opaque = $packet->sign_tsig($opaque); 438 } else { 439 $opaque = $packet->sign_tsig($request); 440 } 441 $signer = \&sign_tcp_continuation 442 if ($Net::DNS::VERSION < 0.70); 443 $continuation = 1; 444 445 my $copy = 446 Net::DNS::Packet->new(\($packet->data)); 447 $prev_tsig = $copy->pop("additional"); 448 } 449 #$packet->print; 450 push(@results,$packet->data); 451 $packet = new Net::DNS::Packet($qname, $qtype, $qclass); 452 $packet->header->qr(1); 453 $packet->header->aa(1); 454 $packet->header->id($id); 455 } 456 } 457 print " A total of $count_these patterns matched\n"; 458 return \@results; 459} 460 461# Main 462my $rin; 463my $rout; 464for (;;) { 465 $rin = ''; 466 vec($rin, fileno($ctlsock), 1) = 1; 467 vec($rin, fileno($tcpsock), 1) = 1; 468 vec($rin, fileno($udpsock), 1) = 1; 469 470 select($rout = $rin, undef, undef, undef); 471 472 if (vec($rout, fileno($ctlsock), 1)) { 473 warn "ctl conn"; 474 my $conn = $ctlsock->accept; 475 my $rule = (); 476 @rules = (); 477 while (my $line = $conn->getline) { 478 chomp $line; 479 if ($line =~ m!^/(.*)/$!) { 480 if (length($1) == 0) { 481 $udphandler = sub { return; }; 482 $tcphandler = sub { return; }; 483 } else { 484 $udphandler = \&handleUDP; 485 $tcphandler = \&handleTCP; 486 $rule = { pattern => $1, answer => [] }; 487 push(@rules, $rule); 488 } 489 } else { 490 push(@{$rule->{answer}}, 491 new Net::DNS::RR($line)); 492 } 493 } 494 $conn->close; 495 #print Dumper(@rules); 496 #print "+=+=+ $rules[0]->{'pattern'}\n"; 497 #print "+=+=+ $rules[0]->{'answer'}->[0]->{'rname'}\n"; 498 #print "+=+=+ $rules[0]->{'answer'}->[0]\n"; 499 } elsif (vec($rout, fileno($udpsock), 1)) { 500 printf "UDP request\n"; 501 my $buf; 502 $udpsock->recv($buf, 512); 503 my $result = &$udphandler($buf); 504 if (defined($result)) { 505 my $num_chars = $udpsock->send($result); 506 print " Sent $num_chars bytes via UDP\n"; 507 } 508 } elsif (vec($rout, fileno($tcpsock), 1)) { 509 my $conn = $tcpsock->accept; 510 my $buf; 511 for (;;) { 512 my $lenbuf; 513 my $n = $conn->sysread($lenbuf, 2); 514 last unless $n == 2; 515 my $len = unpack("n", $lenbuf); 516 $n = $conn->sysread($buf, $len); 517 last unless $n == $len; 518 print "TCP request\n"; 519 my $result = &$tcphandler($buf); 520 if (defined($result)) { 521 foreach my $response (@$result) { 522 $len = length($response); 523 $n = $conn->syswrite(pack("n", $len), 2); 524 $n = $conn->syswrite($response, $len); 525 print " Sent: $n chars via TCP\n"; 526 } 527 } 528 } 529 $conn->close; 530 } 531} 532