tests/system/ans.pl

	ans.pl revision 490b05960c9956cc37f52f5fd4443829d75ce7d6
#!/usr/bin/perl
#
# Copyright (C) 2011  Internet Systems Consortium, Inc. ("ISC")
#
# Permission to use, copy, modify, and/or distribute this software for any
# purpose with or without fee is hereby granted, provided that the above
# copyright notice and this permission notice appear in all copies.
#
# THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
# REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
# AND FITNESS.  IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
# INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
# LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
# OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
# PERFORMANCE OF THIS SOFTWARE.

# $Id: ans.pl,v 1.5 2012/02/22 14:22:54 marka Exp $

#
# 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;

# We default to listening on 10.53.0.2 for historical reasons
# XXX: we should also be able to specify IPv6
my $server_addr = "10.53.0.2";
if (@ARGV > 0) {
    $server_addr = @ARGV[0];
}

# XXX: we should also be able to set the port numbers to listen on.
my $ctlsock = IO::Socket::INET->new(LocalAddr => "$server_addr",
   LocalPort => 5301, Proto => "tcp", Listen => 5, Reuse => 1) or die "$!";

my $udpsock = IO::Socket::INET->new(LocalAddr => "$server_addr",
   LocalPort => 5300, Proto => "udp", Reuse => 1) or die "$!";

my $tcpsock = IO::Socket::INET->new(LocalAddr => "$server_addr",
   LocalPort => 5300, Proto => "tcp", Listen => 5, Reuse => 1) or die "$!";

print "listening on $server_addr:5300,5301.\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 ($request, $err) = new Net::DNS::Packet(\$buf, 0);
    $err and die $err;

    my @questions = $request->question;
    my $qname = $questions[0]->qname;
    my $qtype = $questions[0]->qtype;
    my $qclass = $questions[0]->qclass;
    my $id = $request->header->id;

    my $packet = new Net::DNS::Packet($qname, $qtype, $qclass);
    $packet->header->qr(1);
    $packet->header->aa(1);
    $packet->header->id($id);

    # get the existing signature if any, and clear the additional section
    my $prev_tsig;
    while (my $rr = $request->pop("additional")) {
        if ($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;
    my $offset;

    #
    # decode/encode were introduced in Net::DNS 0.68
    # parse is no longer a method and calling it here makes perl croak.
    #
    my $decode = 0;
    $decode = 1 if ($Net::DNS::VERSION >= 0.68);

    if ($decode) {
        ($header, $offset) = Net::DNS::Header->decode(\$data);
    } else {
        ($header, $offset) = Net::DNS::Header->parse(\$data);
    }

    for (1 .. $header->qdcount) {
        if ($decode) {
            ($q, $offset) =
                 Net::DNS::Question->decode(\$data, $offset);
        } else {
            ($q, $offset) =
                 Net::DNS::Question->parse(\$data, $offset);
        }
    }
    for (1 .. $header->ancount) {
        if ($decode) {
            ($q, $offset) = Net::DNS::RR->decode(\$data, $offset);
        } else {
            ($q, $offset) = Net::DNS::RR->parse(\$data, $offset);
        }
    }
    for (1 .. $header->nscount) {
        if ($decode) {
            ($q, $offset) = Net::DNS::RR->decode(\$data, $offset);
        } else {
            ($q, $offset) = Net::DNS::RR->parse(\$data, $offset);
        }
    }
    for (1 .. $header->arcount) {
        if ($decode) {
            ($q, $offset) = Net::DNS::RR->decode(\$data, $offset);
        } else {
            ($q, $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 ($request, $err) = new Net::DNS::Packet(\$buf, 0);
    $err and die $err;

    my @questions = $request->question;
    my $qname = $questions[0]->qname;
    my $qtype = $questions[0]->qtype;
    my $qclass = $questions[0]->qclass;
    my $id = $request->header->id;

    my $packet = new Net::DNS::Packet($qname, $qtype, $qclass);
    $packet->header->qr(1);
    $packet->header->aa(1);
    $packet->header->id($id);

    # get the existing signature if any, and clear the additional section
    my $prev_tsig;
    my $signer;
    while (my $rr = $request->pop("additional")) {
        if ($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);
            $packet = new Net::DNS::Packet($qname, $qtype, $qclass);
            $packet->header->qr(1);
            $packet->header->aa(1);
            $packet->header->id($id);
        }
    }
    print " A total of $count_these patterns matched\n";
    return \@results;
}

# Main
my $rin;
my $rout;
for (;;) {
    $rin = '';
    vec($rin, fileno($ctlsock), 1) = 1;
    vec($rin, fileno($tcpsock), 1) = 1;
    vec($rin, fileno($udpsock), 1) = 1;

    select($rout = $rin, undef, undef, undef);

    if (vec($rout, fileno($ctlsock), 1)) {
        warn "ctl conn";
        my $conn = $ctlsock->accept;
        my $rule = ();
        @rules = ();
        while (my $line = $conn->getline) {
            chomp $line;
            if ($line =~ m!^/(.*)/$!) {
                $rule = { pattern => $1, answer => [] };
                push(@rules, $rule);
            } else {
                push(@{$rule->{answer}},
                     new Net::DNS::RR($line));
            }
        }
        $conn->close;
        #print Dumper(@rules);
        #print "+=+=+ $rules[0]->{'pattern'}\n";
        #print "+=+=+ $rules[0]->{'answer'}->[0]->{'rname'}\n";
        #print "+=+=+ $rules[0]->{'answer'}->[0]\n";
    } elsif (vec($rout, fileno($udpsock), 1)) {
        printf "UDP request\n";
        my $buf;
        $udpsock->recv($buf, 512);
        my $result = handleUDP($buf);
        my $num_chars = $udpsock->send($result);
        print "  Sent $num_chars bytes via UDP\n";
    } elsif (vec($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);
            last unless $n == $len;
            print "TCP request\n";
            my $result = handleTCP($buf);
            foreach my $response (@$result) {
                $len = length($response);
                $n = $conn->syswrite(pack("n", $len), 2);
                $n = $conn->syswrite($response, $len);
                print "    Sent: $n chars via TCP\n";
            }
        }
        $conn->close;
    }
}