Summerschool Aachen 2004/Project Day I
HTTP Tunnelling
I was planning to implement in my project first a simple program and then extend it to a more "advanced" program: Assume we have a host H1 behind a firewall F who wants to communicate with a host H2 who is outside the firewall. Let us further assume that the firewall F only lets HTTP packets through, i.e. packets with destination port 80, and assume that host H1 wants to build up an SSH connection with host H2. I want first to write a (static) C program run on a host X between host H1 and H2, such that H1 can contact build up an SSH connection with X at port 80 (meaning that the traffic will be let through by F) and X forwards the traffic to H2 at port 22. F should also forward the traffic from H2 to H1. Later I want to extend this program to a more dynamic program in a way that H1 can tell X with whom he wants to build up an SSH connection and X does this. If there is still some time left (which I hope there will be :)) I would like to extend that program to a more generic program which cannot only forward SSH traffic but also SMTP and other kinds of traffic. I know that there are probably already many tunnelling programs doing such kinds of things. However, as I don't have that much experience of network programming (except a small webserver I have once set up in Java) I think that such a project will help me to improve my skills in network programming.
Fingerprinting Tool in perl
This is the current version of the fingerprinting tool, I'm working on.
#!/usr/bin/perl -w
use strict;
# ---------------------------------------------------------------------------------
package Net::DNS::PacketExt;
use strict;
use vars qw(@ISA);
@ISA = qw(Net::DNS::Packet);
sub new
{
my $proto = shift;
my $class = ref $proto || $proto;
my $data = shift;
my $self = Net::DNS::Packet->new($data);
$self->{"header"} = Net::DNS::HeaderExt->new($data);
bless $self, $class;
return $self;
}
1;
# ---------------------------------------------------------------------------------
package Net::DNS::HeaderExt;
use strict;
use vars qw(@ISA);
@ISA = qw(Net::DNS::Header);
sub new
{
my $proto = shift;
my $class = ref $proto || $proto;
my $data = shift;
my $self = Net::DNS::Header->new($data);
my @a = unpack("n C2 n4", $$data);
$self->{"z0"} = ($a[2] >> 6) & 0x1;
$self->{"z1"} = ($a[2] >> 5) & 0x1;
$self->{"z2"} = ($a[2] >> 4) & 0x1;
bless $self, $class;
return $self;
}
1;
# ---------------------------------------------------------------------------------
package MapTool;
use strict;
use Carp;
sub new
{
my $proto = shift;
my $class = ref $proto || $proto;
my $targethost = $_[0] or croak "need target host";
my %self;
$self{targethost} = $targethost;
$self{smtp} = MapTool::Smtp->new();
$self{ftp} = MapTool::Ftp->new();
$self{dns} = MapTool::Dns->new();
bless \%self, $class;
return \%self;
}
sub probe
{
my $self = shift;
$self->{dns}->probe($self->{targethost});
}
sub results
{
my $self = shift;
$self->{dns}->results();
}
1;
# ---------------------------------------------------------------------------------
package MapTool::Smtp;
use strict;
use vars qw/@ISA/;
use Carp;
use Net::DNS::Resolver;
@ISA = ("MapTool");
my $mydomain = 'ccc.de';
my $validsrc = 'cpunkt@ccc.de';
sub new
{
my $proto = shift;
my $class = ref($proto) || $proto;
my $fpres = "smtp_fingerprints";
my $fpcmd = "smtp_tests";
my $self = {};
bless $self, $class;
$self->mkdb($fpcmd, $fpres);
return $self;
}
sub mkdb
{
my $self = shift;
$self->{commands} = [];
$self->{fingerprints} = {};
open TESTS, "$_[0]" or croak "can't open $_[0]";
open RESULTS, "$_[1]" or croak "can't open $_[1]";
while (my $tline = <TESTS>) {
next if ($tline =~ /^#/);
chomp $tline;
my $invalidsrc = $self->generate_source_address();
$tline =~ s/\$MY_DOMAIN/${mydomain}/g;
$tline =~ s/\$VALID_SOURCE/${validsrc}/g;
$tline =~ s/\$INVALID_SOURCE/${invalidsrc}/g;
my @cmd_sequence = split /->/, $tline;
push @{$self->{commands}}, \@cmd_sequence;
}
close TESTS;
while (my $rline = <RESULTS>) {
next if ($rline =~ /^#/);
chomp $rline;
my @res_sequence = split /:/, $rline;
my $software_version = shift @res_sequence;
$self->{fingerprints}->{$software_version} = \@res_sequence;
}
close RESULTS;
}
sub generate_source_address
{
my ($i, $ok, $query);
my ($fake_domain, $fake_user) = ('', '');
my $res = Net::DNS::Resolver->new;
my @VALID_CHARS = ( 'A' .. 'Z', 'a' .. 'z', '0' .. '9', '_');
while (not $ok) {
for $i (1 .. 25) {
$fake_domain .= $VALID_CHARS[int rand(@VALID_CHARS)];
}
$fake_domain .= '.com';
$ok = 1;
$query = $res->query($fake_domain, 'SOA');
$ok = 1 if (not $query);
}
for $i (1 .. 10) {
$fake_user .= $VALID_CHARS[int rand(@VALID_CHARS)];
}
return "$fake_user\@$fake_domain";
}
1;
# ---------------------------------------------------------------------------------
package MapTool::Ftp;
use strict;
use vars qw/@ISA/;
use Carp;
@ISA = ("MapTool");
sub new
{
my $proto = shift;
my $class = ref($proto) || $proto;
my $fpres = "ftp_fingerprints";
my $fpcmd = "ftp_tests";
my $self = {};
bless $self, $class;
$self->mkdb($fpcmd, $fpres);
return $self;
}
sub mkdb
{
my $self = shift;
$self->{commands} = [];
$self->{fingerprints} = {};
open TESTS, "$_[0]" or croak "can't open $_[0]";
open RESULTS, "$_[1]" or croak "can't open $_[1]";
my $isnulled = 0;
while (my $tline = <TESTS>) {
next if ($tline =~ /^#/);
chomp $tline;
if ($tline =~ /^#if 0/) {
$isnulled = 1;
} elsif ($isnulled && $tline =~ /^#endif/) {
$isnulled = 0;
}
next if ($isnulled || $tline !~ /^\s*"([^"]+)"/);
push @{$self->{commands}}, $1;
}
close TESTS;
my $inblock = 0;
my $softwareversion;
while (my $rline = <RESULTS>) {
chomp $rline;
if ($inblock && $rline =~ /^\s*\}/) {
$inblock = 0;
$softwareversion = '';
next;
} elsif ($inblock) {
my @checksums = split /,/, $rline;
push @{$self->{fingerprints}->{$softwareversion}}, \@checksums;
next;
}
if ($rline =~ /^\s*0UL,\s*"([^"]+)"/) {
$softwareversion = $1;
$inblock = 1
}
}
close RESULTS;
}
1;
# ---------------------------------------------------------------------------------
package MapTool::Dns;
use strict;
use vars qw/@ISA/;
use Carp;
use LWP::UserAgent;
use Sys::Hostname;
use Socket;
@ISA = ("MapTool");
sub new
{
my $proto = shift;
my $class = ref($proto) || $proto;
my $self = {};
my $ua = LWP::UserAgent->new;
$ua->timeout(23);
my $djb_response = $ua->get('http://cr.yp.to/surveys/dns1.html');
if ($djb_response->is_success) {
bless $self, $class;
$self->mkdb($djb_response->content);
return $self;
}
croak $djb_response->status_line;
}
sub mkdb
{
my $self = shift;
$self->{commands} = [];
$self->{fingerprints} = {};
my $html_response = $_[0];
my @html_lines = split /\n/, $html_response;
my $tables = 0;
my $table_open = 0;
$self->{commands} = [
"\0\0\10\0\0\1\0\0\0\0\0\0\4test\17network-surveys\2cr\2yp\2to\0\0\20\0\1",
"\0\0\0\0\0\1\0\0\0\0\0\0\4test\17network-surveys\2cr\2yp\2to\0\0\20\0\3",
"\0\0\0\0\0\1\0\0\0\0\0\0\4test\17network-surveys\2cr\2yp\2to\0\0\20\0\77",
"\0\0\0\0\0\2\0\0\0\0\0\0\4test\17network-surveys\2cr\2yp\2to\0\0\20\0\1\0\0\20\0\1",
"\0\0\40\0\0\1\0\0\0\0\0\0\4test\17network-surveys\2cr\2yp\2to\0\0\20\0\1",
"\0\0\50\0\0\1\0\0\0\0\0\0\4test\17network-surveys\2cr\2yp\2to\0\0\20\0\1",
"\0\0\0\0\0\0\0\0\0\0\0\0",
"\0\0\0\0\0\1\0\0\0\0\0\0\6",
"\0\0\0\0\0\1\0\0\0\0\0\0\4test\17network-surveys\2cr\2yp\2to\0",
"\0\0\2\0\0\1\0\0\0\0\0\0\4test\17network-surveys\2cr\2yp\2to\0\0\20\0\1",
"\0\0\0\0\0\1\0\0\0\0\0\0\7Authors\4BIND\0\0\20\0\3",
"\0\0\4\0\0\1\0\0\0\0\0\0\4test\17network-surveys\2cr\2yp\2to\0\0\20\0\1",
"\0\0\0\17\0\1\0\0\0\0\0\0\4test\17network-surveys\2cr\2yp\2to\0\0\20\0\1",
"\0\0\0\20\0\1\0\0\0\0\0\0\4test\17network-surveys\2cr\2yp\2to\0\0\20\0\1",
"\0\0\0\40\0\1\0\0\0\0\0\0\4test\17network-surveys\2cr\2yp\2to\0\0\20\0\1",
"\0\0\0\100\0\1\0\0\0\0\0\0\4test\17network-surveys\2cr\2yp\2to\0\0\20\0\1",
"\0\0\20\0\0\1\0\0\0\0\0\0\4test\17network-surveys\2cr\2yp\2to\0\0\20\0\1",
"\0\0\30\0\0\1\0\0\0\0\0\0\4test\17network-surveys\2cr\2yp\2to\0\0\20\0\1",
"\0\0\60\0\0\1\0\0\0\0\0\0\4test\17network-surveys\2cr\2yp\2to\0\0\20\0\1",
"\0\0\0\0\0\1\0\0\0\0\0\0\4test\17network-surveys\2cr\2yp\2to\0\0\20\0\1",
"\0\0\0\0\0\1\0\0\0\0\0\0\25erre-con-erre-cigarro\7maradns\3org\0\0\20\0\1",
"\0\0\0\0\0\1\0\0\0\0\0\0\7version\6server\0\0\20\0\3",
"\0\0\0\0\0\1\0\0\0\0\0\0\7version\4bind\0\0\20\0\3"
];
foreach my $hline (@html_lines) {
if ($hline =~ /<table/) {
$tables++;
$table_open = 1;
next;
} elsif ($hline =~ /<\/table/) {
$table_open = 0;
next;
}
if ($tables > 3 && $tables < 10 && $table_open) {
if ($hline =~ /<tr><td>Software/ || $hline !~ s/<tr><td>([^<]+)<\/td>//) {
next;
}
my $softwareversion = $1;
my @results;
while ($hline =~ s/<td>([^<]+)<\/td>//) {
push @results, $1;
}
push @{$self->{fingerprints}->{$softwareversion}}, \@results;
}
}
}
sub probe
{
my $self = shift;
my $targethost = $_[0];
my $iaddr = inet_aton("0.0.0.0");
my $proto = getprotobyname('udp');
my $port = getservbyname('domain', 'udp');
my $paddr = sockaddr_in(0, $iaddr);
socket(SOCK, PF_INET, SOCK_DGRAM, $proto) || croak "socket: $!";
bind(SOCK, $paddr) || croak "bind: $!";
$| = 1;
my $hisiaddr = inet_aton($targethost) || croak "unknown host";
my $hispaddr = sockaddr_in($port, $hisiaddr);
my $count = 0;
foreach my $request (@{$self->{commands}}) {
$count++;
defined(send(SOCK, $request, 0, $hispaddr)) || croak "send ".$targethost.": $!";
my $rin = '';
vec($rin, fileno(SOCK), 1) = 1;
my $rout;
if (!select($rout = $rin, undef, undef, 3.0)) {
$count > 0 && do { $count = 0; $self->pushresult("timeout"); next; };
redo;
}
my $response;
($hispaddr = recv(SOCK, $response, 1000, 0)) || croak "recv: $!";
$self->pushresult($response);
$count = 0;
}
}
sub pushresult
{
my $self = shift;
my $result = $_[0];
push @{$self->{answers}}, $result;
}
sub results
{
my $self = shift;
if (scalar @{$self->{answers}} != scalar @{$self->{commands}}) {
croak "number of answers doesn't match number of commands";
}
$self->{results} = {};
foreach my $swversion (keys %{$self->{fingerprints}}) {
for (my $j = 0; $j < scalar @{$self->{fingerprints}->{$swversion}}; $j++) {
my $matchcount;
for (my $i = 0; $i < scalar @{$self->{answers}}; $i++) {
$matchcount += $self->compare($self->{answers}->[$i],
$self->{fingerprints}->{$swversion}->[$j]->[$i]);
}
push @{$self->{results}->{$matchcount}}, $swversion;
}
}
for (my $score = scalar @{$self->{answers}}; $score >= 0; $score--) {
next unless (defined $self->{results}->{$score});
print "matched with score ".int ($score/(scalar @{$self->{answers}})*100).":\n";
map { print "\t$_\n"; } @{$self->{results}->{$score}};
}
}
sub compare
{
my $self = shift;
my ($response, $fingerprint) = @_;
$fingerprint =~ s/\s+//g;
if ($fingerprint =~ /t/) {
return($response eq 'timeout');
} elsif ($response eq 'timeout') {
return 0;
}
my @alternatives = split /,/, $fingerprint;
my $packet = Net::DNS::PacketExt->new(\$response);
$packet || croak("DNS::Packet refuses the response...");
my $header = $packet->header;
my @queries = $packet->question;
my @answers = $packet->answer;
my $match = 0;
foreach my $alternative (@alternatives) {
if ($alternative =~ s/0//) {
$match = ($header->rcode eq 'NOERROR');
next unless ($match);
}
if ($alternative =~ s/1//) {
$match = ($header->rcode eq 'FORMERR');
next unless ($match);
}
if ($alternative =~ s/2//) {
$match = ($header->rcode eq 'SERVFAIL');
next unless ($match);
}
if ($alternative =~ s/3//) {
$match = ($header->rcode eq 'NXDOMAIN');
next unless ($match);
}
if ($alternative =~ s/4//) {
$match = ($header->rcode eq 'NOTIMP');
next unless ($match);
}
if ($alternative =~ s/5//) {
$match = ($header->rcode eq 'REFUSED');
next unless ($match);
}
if ($alternative =~ s/TC//) {
$match = $header->tc;
next unless ($match);
}
if ($alternative =~ s/RD//) {
$match = $header->rd;
next unless ($match);
}
if ($alternative =~ s/AA//) {
$match = $header->aa;
next unless ($match);
}
if ($alternative =~ s/Z0//) {
$match = $header->z0;
next unless ($match);
}
if ($alternative =~ s/Z1//) {
$match = $header->z1;
next unless ($match);
}
if ($alternative =~ s/Z2//) {
$match = $header->z2;
next unless ($match);
}
if ($alternative =~ s/q//) {
$match = ($#queries == -1);
next unless ($match);
}
if ($alternative =~ s/Q2//) {
$match = ($#queries == 1);
next unless ($match);
}
if ($alternative =~ s/X//) {
$match = 1;
next unless ($match);
}
if ($alternative =~ s/D//) {
$match = ($#answers > -1);
next unless ($match);
}
}
return $match;
}
1;
# ---------------------------------------------------------------------------------
use strict;
if ($#ARGV != 0) {
print "usage: $0 <hostname>\n\n";
exit 1;
}
my $targethost = $ARGV[0];
my $map = MapTool->new($targethost);
$map->probe();
$map->results();
