1#!/usr/bin/perl 2# 3# Copyright (C) 2011, 2012 Internet Systems Consortium, Inc. ("ISC") 4# 5# Permission to use, copy, modify, and/or distribute this software for any 6# purpose with or without fee is hereby granted, provided that the above 7# copyright notice and this permission notice appear in all copies. 8# 9# THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH 10# REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY 11# AND FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT, 12# INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM 13# LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE 14# OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR 15# PERFORMANCE OF THIS SOFTWARE. 16 17# $Id$ 18 19# 20# This is the name server from hell. It provides canned 21# responses based on pattern matching the queries, and 22# can be reprogrammed on-the-fly over a TCP connection. 23# 24# The server listens for control connections on port 5301. 25# A control connection is a TCP stream of lines like 26# 27# /pattern/ 28# name ttl type rdata 29# name ttl type rdata 30# ... 31# /pattern/ 32# name ttl type rdata 33# name ttl type rdata 34# ... 35# 36# There can be any number of patterns, each associated 37# with any number of response RRs. Each pattern is a 38# Perl regular expression. 39# 40# Each incoming query is converted into a string of the form 41# "qname qtype" (the printable query domain name, space, 42# printable query type) and matched against each pattern. 43# 44# The first pattern matching the query is selected, and 45# the RR following the pattern line are sent in the 46# answer section of the response. 47# 48# Each new control connection causes the current set of 49# patterns and responses to be cleared before adding new 50# ones. 51# 52# The server handles UDP and TCP queries. Zone transfer 53# responses work, but must fit in a single 64 k message. 54# 55# Now you can add TSIG, just specify key/key data with: 56# 57# /pattern <key> <key_data>/ 58# name ttl type rdata 59# name ttl type rdata 60# 61# Note that this data will still be sent with any request for 62# pattern, only this data will be signed. Currently, this is only 63# done for TCP. 64 65 66use IO::File; 67use IO::Socket; 68use Data::Dumper; 69use Net::DNS; 70use Net::DNS::Packet; 71use strict; 72 73# Ignore SIGPIPE so we won't fail if peer closes a TCP socket early 74local $SIG{PIPE} = 'IGNORE'; 75 76# Flush logged output after every line 77local $| = 1; 78 79my $server_addr = "10.53.0.4"; 80 81my $udpsock = IO::Socket::INET->new(LocalAddr => "$server_addr", 82 LocalPort => 5300, Proto => "udp", Reuse => 1) or die "$!"; 83 84my $tcpsock = IO::Socket::INET->new(LocalAddr => "$server_addr", 85 LocalPort => 5300, Proto => "tcp", Listen => 5, Reuse => 1) or die "$!"; 86 87print "listening on $server_addr:5300.\n"; 88 89my $pidf = new IO::File "ans.pid", "w" or die "cannot open pid file: $!"; 90print $pidf "$$\n" or die "cannot write pid file: $!"; 91$pidf->close or die "cannot close pid file: $!";; 92sub rmpid { unlink "ans.pid"; exit 1; }; 93 94$SIG{INT} = \&rmpid; 95$SIG{TERM} = \&rmpid; 96 97#my @answers = (); 98my @rules; 99sub handleUDP { 100 my ($buf) = @_; 101 102 my ($packet, $err) = new Net::DNS::Packet(\$buf, 0); 103 $err and die $err; 104 105 $packet->header->qr(1); 106 $packet->header->aa(1); 107 108 my @questions = $packet->question; 109 my $qname = $questions[0]->qname; 110 my $qtype = $questions[0]->qtype; 111 112 # get the existing signature if any, and clear the additional section 113 my $prev_tsig; 114 while (my $rr = $packet->pop("additional")) { 115 if ($rr->type eq "TSIG") { 116 $prev_tsig = $rr; 117 } 118 } 119 120 my $r; 121 foreach $r (@rules) { 122 my $pattern = $r->{pattern}; 123 my($dbtype, $key_name, $key_data) = split(/ /,$pattern); 124 print "[handleUDP] $dbtype, $key_name, $key_data \n"; 125 if ("$qname $qtype" =~ /$dbtype/) { 126 my $a; 127 foreach $a (@{$r->{answer}}) { 128 $packet->push("answer", $a); 129 } 130 if(defined($key_name) && defined($key_data)) { 131 # Sign the packet 132 print " Signing the response with " . 133 "$key_name/$key_data\n"; 134 my $tsig = Net::DNS::RR-> 135 new("$key_name TSIG $key_data"); 136 137 # These kluges are necessary because Net::DNS 138 # doesn't know how to sign responses. We 139 # clear compnames so that the TSIG key and 140 # algorithm name won't be compressed, and 141 # add one to arcount because the signing 142 # function will attempt to decrement it, 143 # which is incorrect in a response. Finally 144 # we set request_mac to the previous digest. 145 $packet->{"compnames"} = {}; 146 $packet->{"header"}{"arcount"} += 1; 147 if (defined($prev_tsig)) { 148 my $rmac = pack('n H*', 149 $prev_tsig->mac_size, 150 $prev_tsig->mac); 151 $tsig->{"request_mac"} = 152 unpack("H*", $rmac); 153 } 154 155 $packet->sign_tsig($tsig); 156 } 157 last; 158 } 159 } 160 #$packet->print; 161 162 return $packet->data; 163} 164 165# namelen: 166# given a stream of data, reads a DNS-formatted name and returns its 167# total length, thus making it possible to skip past it. 168sub namelen { 169 my ($data) = @_; 170 my $len = 0; 171 my $label_len = 0; 172 do { 173 $label_len = unpack("c", $data); 174 $data = substr($data, $label_len + 1); 175 $len += $label_len + 1; 176 } while ($label_len != 0); 177 return ($len); 178} 179 180# packetlen: 181# given a stream of data, reads a DNS wire-format packet and returns 182# its total length, making it possible to skip past it. 183sub packetlen { 184 my ($data) = @_; 185 my $q; 186 my $rr; 187 188 my ($header, $offset) = Net::DNS::Header->parse(\$data); 189 for (1 .. $header->qdcount) { 190 ($q, $offset) = Net::DNS::Question->parse(\$data, $offset); 191 } 192 for (1 .. $header->ancount) { 193 ($rr, $offset) = Net::DNS::RR->parse(\$data, $offset); 194 } 195 for (1 .. $header->nscount) { 196 ($rr, $offset) = Net::DNS::RR->parse(\$data, $offset); 197 } 198 for (1 .. $header->arcount) { 199 ($rr, $offset) = Net::DNS::RR->parse(\$data, $offset); 200 } 201 return $offset; 202} 203 204# sign_tcp_continuation: 205# This is a hack to correct the problem that Net::DNS has no idea how 206# to sign multiple-message TCP responses. Several data that are included 207# in the digest when signing a query or the first message of a response are 208# omitted when signing subsequent messages in a TCP stream. 209# 210# Net::DNS::Packet->sign_tsig() has the ability to use a custom signing 211# function (specified by calling Packet->sign_func()). We use this 212# function as the signing function for TCP continuations, and it removes 213# the unwanted data from the digest before calling the default sign_hmac 214# function. 215sub sign_tcp_continuation { 216 my ($key, $data) = @_; 217 218 # copy out first two bytes: size of the previous MAC 219 my $rmacsize = unpack("n", $data); 220 $data = substr($data, 2); 221 222 # copy out previous MAC 223 my $rmac = substr($data, 0, $rmacsize); 224 $data = substr($data, $rmacsize); 225 226 # try parsing out the packet information 227 my $plen = packetlen($data); 228 my $pdata = substr($data, 0, $plen); 229 $data = substr($data, $plen); 230 231 # remove the keyname, ttl, class, and algorithm name 232 $data = substr($data, namelen($data)); 233 $data = substr($data, 6); 234 $data = substr($data, namelen($data)); 235 236 # preserve the TSIG data 237 my $tdata = substr($data, 0, 8); 238 239 # prepare a new digest and sign with it 240 $data = pack("n", $rmacsize) . $rmac . $pdata . $tdata; 241 return Net::DNS::RR::TSIG::sign_hmac($key, $data); 242} 243 244sub handleTCP { 245 my ($buf) = @_; 246 247 my ($packet, $err) = new Net::DNS::Packet(\$buf, 0); 248 $err and die $err; 249 250 $packet->header->qr(1); 251 $packet->header->aa(1); 252 253 my @questions = $packet->question; 254 my $qname = $questions[0]->qname; 255 my $qtype = $questions[0]->qtype; 256 257 # get the existing signature if any, and clear the additional section 258 my $prev_tsig; 259 my $signer; 260 while (my $rr = $packet->pop("additional")) { 261 if ($rr->type eq "TSIG") { 262 $prev_tsig = $rr; 263 } 264 } 265 266 my @results = (); 267 my $count_these = 0; 268 269 my $r; 270 foreach $r (@rules) { 271 my $pattern = $r->{pattern}; 272 my($dbtype, $key_name, $key_data) = split(/ /,$pattern); 273 print "[handleTCP] $dbtype, $key_name, $key_data \n"; 274 if ("$qname $qtype" =~ /$dbtype/) { 275 $count_these++; 276 my $a; 277 foreach $a (@{$r->{answer}}) { 278 $packet->push("answer", $a); 279 } 280 if(defined($key_name) && defined($key_data)) { 281 # sign the packet 282 print " Signing the data with " . 283 "$key_name/$key_data\n"; 284 285 my $tsig = Net::DNS::RR-> 286 new("$key_name TSIG $key_data"); 287 288 # These kluges are necessary because Net::DNS 289 # doesn't know how to sign responses. We 290 # clear compnames so that the TSIG key and 291 # algorithm name won't be compressed, and 292 # add one to arcount because the signing 293 # function will attempt to decrement it, 294 # which is incorrect in a response. Finally 295 # we set request_mac to the previous digest. 296 $packet->{"compnames"} = {}; 297 $packet->{"header"}{"arcount"} += 1; 298 if (defined($prev_tsig)) { 299 my $rmac = pack('n H*', 300 $prev_tsig->mac_size, 301 $prev_tsig->mac); 302 $tsig->{"request_mac"} = 303 unpack("H*", $rmac); 304 } 305 306 $tsig->sign_func($signer) if defined($signer); 307 $packet->sign_tsig($tsig); 308 $signer = \&sign_tcp_continuation; 309 310 my $copy = 311 Net::DNS::Packet->new(\($packet->data)); 312 $prev_tsig = $copy->pop("additional"); 313 } 314 #$packet->print; 315 push(@results,$packet->data); 316 $packet = new Net::DNS::Packet(\$buf, 0); 317 $packet->header->qr(1); 318 $packet->header->aa(1); 319 } 320 } 321 print " A total of $count_these patterns matched\n"; 322 return \@results; 323} 324 325# Main 326my $rin; 327my $rout; 328for (;;) { 329 $rin = ''; 330 vec($rin, fileno($tcpsock), 1) = 1; 331 vec($rin, fileno($udpsock), 1) = 1; 332 333 select($rout = $rin, undef, undef, undef); 334 335 if (vec($rout, fileno($udpsock), 1)) { 336 printf "UDP request\n"; 337 my $buf; 338 $udpsock->recv($buf, 512); 339 } elsif (vec($rout, fileno($tcpsock), 1)) { 340 my $conn = $tcpsock->accept; 341 my $buf; 342 for (;;) { 343 my $lenbuf; 344 my $n = $conn->sysread($lenbuf, 2); 345 last unless $n == 2; 346 my $len = unpack("n", $lenbuf); 347 $n = $conn->sysread($buf, $len); 348 } 349 sleep(1); 350 } 351} 352