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+#!/usr/bin/perl
+
+# 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.
+
+#
+# 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);
+ }
+}
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