4 # Copyright (C) 2004-2005 Jan Kratochvil <project-netdnsspoof@jankratochvil.net>
6 # This program is free software; you can redistribute it and/or modify
7 # it under the terms of the GNU General Public License as published by
8 # the Free Software Foundation; exactly version 2 of June 1991 is required
10 # This program is distributed in the hope that it will be useful,
11 # but WITHOUT ANY WARRANTY; without even the implied warranty of
12 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 # GNU General Public License for more details.
15 # You should have received a copy of the GNU General Public License
16 # along with this program; if not, write to the Free Software
17 # Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
23 require IO::Socket::INET;
24 require Net::DNS::Packet;
26 use Carp qw(cluck confess);
29 require "linux/in.ph";
38 my $opt_forward_addr="localhost";
39 my $opt_forward_port=53;
40 my $opt_spoof_ip="192.168.1.1";
42 "a|addr=s",\$opt_addr,
43 "p|port=s",\$opt_port,
44 "forward-addr=s",\$opt_forward_addr,
45 "forward-port=s",\$opt_forward_port,
46 "i|spoof-ip=s",\$opt_spoof_ip,
49 my $forward_host=gethostbyname($opt_forward_addr) or die "resolving $opt_forward_addr: $!";
50 my $forward_addr=sockaddr_in($opt_forward_port,$forward_host) or die "assembling $opt_forward_addr:$opt_forward_port";
52 my $sock_udp=IO::Socket::INET->new(
56 ) or die "socket(): $!";
57 my $sock_udp_priv=IO::Socket::INET->new(
59 ) or die "socket(): $!";
60 ###fcntl($sock_udp,F_SETFL,O_NONBLOCK) or die "fnctl(sock_udp,F_SETFL,O_NONBLOCK)";
62 my $ip_pktinfo_got=setsockopt $sock_udp,IPPROTO_IP(),IP_PKTINFO(),pack("i",1);
63 # FIXME: Why Linux kernel 2.6.9-1.678_FC3 returns 1 instead of 0?
64 confess 'setsockopt(sock_udp,IPPROTO_IP,IP_PKTINFO,&1)='.$ip_pktinfo_got
65 if !defined $ip_pktinfo_got || 0>$ip_pktinfo_got;
66 my $ip_pktinfo_val=getsockopt $sock_udp,IPPROTO_IP(),IP_PKTINFO();
67 confess 'getsockopt(sock_udp,IPPROTO_IP,IP_PKTINFO)!=1'
68 if 1!=unpack("i",$ip_pktinfo_val);
74 $id=int(rand(0x10000)) if !defined $id;
84 my($msg,$from_addr,$pktinfo_data)=@_;
86 my $query=Net::DNS::Packet->new(\$msg);
87 # FIXME: It really occured on hoteltest.
88 do { warn "Failed to parse DNS packet query: ".unpack("H*",$msg); return; } if !$query;
89 my $query_id_orig=$query->header()->id();
90 my $query_id=id_next();
91 $query->header()->id($query_id);
92 my $msg_forward=$query->data();
93 $query->header()->id($query_id_orig); # fix-up back
96 "from_addr"=>$from_addr,
97 "pktinfo_data"=>$pktinfo_data,
100 warn "registered pending query id $query_id..." if $D;
101 warn "sending forwarded DNS query (mapped id $query_id_orig -> $query_id)..." if $D;
102 send $sock_udp_priv,$msg_forward,0,$forward_addr or cluck "send(): $!";
105 sub check_spoofable($$)
107 my($reply,$query)=@_;
109 warn "checking packet spoofability from the reply... (non-spoofable if silent)" if $D;
110 my @questions=$query->question();
111 return 0 if 1!=@questions;
112 my $question=$questions[0];
113 return 0 if $question->qtype() ne "A"
114 && $question->qtype() ne "ANY";
115 return 0 if $reply->header()->rcode() ne "NXDOMAIN";
116 warn "packet considered as spoofable." if $D;
122 my($query_from_addr,$query)=@_;
124 warn "assembling spoof reply..." if $D;
125 my $question=($query->question())[0];
126 my $spoof=Net::DNS::Packet->new($question->qname(),$question->qclass(),$question->qtype());
127 $spoof->push("answer",Net::DNS::RR->new(join(" ",
132 $opt_spoof_ip, # rdata
134 $spoof->header()->rcode("NOERROR");
135 $spoof->header()->aa(0);
136 $spoof->header()->qr(1);
137 $spoof->header()->ra(1);
138 $spoof->header()->rd($query->header()->rd());
139 $spoof->header()->id($query->header()->id());
140 my $msg_spoof=$spoof->data();
141 warn "sending spoof reply..." if $D;
143 my($query_from_addr_port,$query_from_addr_host)=sockaddr_in($query_from_addr);
144 my $query_from_addr_name=inet_ntoa $query_from_addr_host;
145 print localtime()." spoof:"
146 ." from=$query_from_addr_name:$query_from_addr_port"
147 ." qname=".$question->qname()
148 ." ip=".$opt_spoof_ip
154 sub got_forward_reply($)
158 warn "parsing reply from our forwarded DNS..." if $D;
159 my $reply=Net::DNS::Packet->new(\$msg);
160 my $reply_id=$reply->header()->id();
161 my($query_msg,$query_from_addr,$query_pktinfo_data,$query);
162 if (my $hash=$sent{$reply_id}) {
163 delete $sent{$reply_id};
164 $query_msg =$hash->{"msg"};
165 $query_from_addr =$hash->{"from_addr"};
166 $query_pktinfo_data=$hash->{"pktinfo_data"};
167 $query =$hash->{"query"};
168 warn "deleted pending record with id $reply_id." if $D;
171 warn "Got DNS reply for unknown packet id $reply_id";
175 if (check_spoofable($reply,$query)) {
176 $reply_back=reply_spoof $query_from_addr,$query or return;
179 $reply->header()->id($query->header()->id());
180 $reply_back=$reply->data();
181 warn "passing reply back to the original query host..." if $D;
183 my $msghdr=Socket::MsgHdr->new();
184 $msghdr->buf($reply_back);
185 $msghdr->name($query_from_addr);
186 $msghdr->cmsghdr(IPPROTO_IP(),IP_PKTINFO(),$query_pktinfo_data);
187 sendmsg $sock_udp,$msghdr or cluck "sendmsg(): $!";
190 $V and print localtime()." START\n";
193 vec($rfds,fileno($sock_udp),1)=1;
194 vec($rfds,fileno($sock_udp_priv),1)=1;
195 warn "select(2)..." if $D;
196 my $got=select $rfds,undef(),undef(),undef();
197 warn "got from select." if $D;
198 die "Invalid select(2): ".Dumper($got) if !defined $got || $got<0;
200 if (vec($rfds,fileno($sock_udp_priv),1)) {{
202 defined(my $from_addr=recv $sock_udp_priv,$msg,0x10000,0) or do { cluck "recv(sock_udp_priv): $!"; next; };
203 warn "got packet from forwarding DNS..." if $D;
204 my($from_addr_port,$from_addr_host)=sockaddr_in($from_addr);
206 if ($from_addr_host ne $forward_host || $from_addr_port ne $opt_forward_port) {
207 warn "original query forbidden from the private forwarding socket";
210 got_forward_reply $msg;
212 if (vec($rfds,fileno($sock_udp),1)) {{
213 # "namelen"=>0x10 to prevent: Bad arg length for Socket::unpack_sockaddr_in, length is 4096, should be 16 at /usr/lib/perl5/5.8.5/i386-linux-thread-multi/Socket.pm line 370.
214 my $msghdr=Socket::MsgHdr->new("buflen"=>0x10000,"namelen"=>0x10,"controllen"=>0x1000);
215 defined(recvmsg($sock_udp,$msghdr,0)) or do { cluck "recvmsg(sock_udp): $!"; next; };
216 warn "got packet as original query..." if $D;
217 my $msg=$msghdr->buf();
219 my @cmsg=$msghdr->cmsghdr();
220 while (my($level,$type,$data)=splice(@cmsg,0,3)) {
221 do { warn "unknown cmsg level $level"; next; } if $level!=IPPROTO_IP();
222 do { warn "unknown cmsg level $type"; next; } if $type !=IP_PKTINFO();
225 do { warn "IP_PKTINFO not found for a packet"; next; } if !defined $pktinfo_data;
226 my $from_addr=$msghdr->name();
227 my($from_addr_port,$from_addr_host)=sockaddr_in($from_addr);
229 if ($from_addr_host eq $forward_host && $from_addr_port eq $opt_forward_port) {
230 warn "packet returned from forwarding DNS forbidden from the main listening socket";
233 got_query $msg,$from_addr,$pktinfo_data;