1#!/usr/bin/env perl
2#
3# Copyright (C) Internet Systems Consortium, Inc. ("ISC")
4#
5# This Source Code Form is subject to the terms of the Mozilla Public
6# License, v. 2.0. If a copy of the MPL was not distributed with this
7# file, you can obtain one at https://mozilla.org/MPL/2.0/.
8#
9# See the COPYRIGHT file distributed with this work for additional
10# information regarding copyright ownership.
11
12use strict;
13use warnings;
14
15use IO::File;
16use Getopt::Long;
17use Net::DNS::Nameserver;
18
19my $pidf = new IO::File "ans.pid", "w" or die "cannot open pid file: $!";
20print $pidf "$$\n" or die "cannot write pid file: $!";
21$pidf->close or die "cannot close pid file: $!";
22sub rmpid { unlink "ans.pid"; exit 1; };
23
24$SIG{INT} = \&rmpid;
25$SIG{TERM} = \&rmpid;
26
27my $localaddr = "10.53.0.3";
28
29my $localport = int($ENV{'PORT'});
30if (!$localport) { $localport = 5300; }
31
32my $verbose = 0;
33my $ttl = 60;
34my $zone = "example.broken";
35my $nsname = "ns3.$zone";
36my $synth = "synth-then-dname.$zone";
37my $synth2 = "synth2-then-dname.$zone";
38
39sub reply_handler {
40    my ($qname, $qclass, $qtype, $peerhost, $query, $conn) = @_;
41    my ($rcode, @ans, @auth, @add);
42
43    print ("request: $qname/$qtype\n");
44    STDOUT->flush();
45
46    if ($qname eq "example.broken") {
47        if ($qtype eq "SOA") {
48	    my $rr = new Net::DNS::RR("$qname $ttl $qclass SOA . . 0 0 0 0 0");
49	    push @ans, $rr;
50        } elsif ($qtype eq "NS") {
51	    my $rr = new Net::DNS::RR("$qname $ttl $qclass NS $nsname");
52	    push @ans, $rr;
53	    $rr = new Net::DNS::RR("$nsname $ttl $qclass A $localaddr");
54	    push @add, $rr;
55        }
56        $rcode = "NOERROR";
57    } elsif ($qname eq "cname-to-$synth2") {
58        my $rr = new Net::DNS::RR("$qname $ttl $qclass CNAME name.$synth2");
59	push @ans, $rr;
60        $rr = new Net::DNS::RR("name.$synth2 $ttl $qclass CNAME name");
61	push @ans, $rr;
62        $rr = new Net::DNS::RR("$synth2 $ttl $qclass DNAME .");
63	push @ans, $rr;
64	$rcode = "NOERROR";
65    } elsif ($qname eq "$synth" || $qname eq "$synth2") {
66	if ($qtype eq "DNAME") {
67	    my $rr = new Net::DNS::RR("$qname $ttl $qclass DNAME .");
68	    push @ans, $rr;
69	}
70	$rcode = "NOERROR";
71    } elsif ($qname eq "name.$synth") {
72	my $rr = new Net::DNS::RR("$qname $ttl $qclass CNAME name.");
73	push @ans, $rr;
74	$rr = new Net::DNS::RR("$synth $ttl $qclass DNAME .");
75	push @ans, $rr;
76	$rcode = "NOERROR";
77    } elsif ($qname eq "name.$synth2") {
78	my $rr = new Net::DNS::RR("$qname $ttl $qclass CNAME name.");
79	push @ans, $rr;
80	$rr = new Net::DNS::RR("$synth2 $ttl $qclass DNAME .");
81	push @ans, $rr;
82	$rcode = "NOERROR";
83    # The following three code branches referring to the "example.dname"
84    # zone are necessary for the resolver variant of the CVE-2021-25215
85    # regression test to work.  A named instance cannot be used for
86    # serving the DNAME records below as a version of BIND vulnerable to
87    # CVE-2021-25215 would crash while answering the queries asked by
88    # the tested resolver.
89    } elsif ($qname eq "ns3.example.dname") {
90	if ($qtype eq "A") {
91		my $rr = new Net::DNS::RR("$qname $ttl $qclass A 10.53.0.3");
92		push @ans, $rr;
93	}
94	if ($qtype eq "AAAA") {
95		my $rr = new Net::DNS::RR("example.dname. $ttl $qclass SOA . . 0 0 0 0 $ttl");
96		push @auth, $rr;
97	}
98	$rcode = "NOERROR";
99    } elsif ($qname eq "self.example.self.example.dname") {
100	my $rr = new Net::DNS::RR("self.example.dname. $ttl $qclass DNAME dname.");
101	push @ans, $rr;
102	$rr = new Net::DNS::RR("$qname $ttl $qclass CNAME self.example.dname.");
103	push @ans, $rr;
104	$rcode = "NOERROR";
105    } elsif ($qname eq "self.example.dname") {
106	if ($qtype eq "DNAME") {
107		my $rr = new Net::DNS::RR("$qname $ttl $qclass DNAME dname.");
108		push @ans, $rr;
109	}
110	$rcode = "NOERROR";
111    } else {
112	$rcode = "REFUSED";
113    }
114    return ($rcode, \@ans, \@auth, \@add, { aa => 1 });
115}
116
117GetOptions(
118    'port=i' => \$localport,
119    'verbose!' => \$verbose,
120);
121
122my $ns = Net::DNS::Nameserver->new(
123    LocalAddr => $localaddr,
124    LocalPort => $localport,
125    ReplyHandler => \&reply_handler,
126    Verbose => $verbose,
127);
128
129$ns->main_loop;
130