#!/usr/bin/perl
# (C) 2006 Julian Haight (http://www.julianhaight.com) GPL License
use strict; my($usage) = q{

NAME
     bait - encode or decode ip and timestamp

SYNOPSIS
     <!--#include virtual="/cgi-bin/bait" -->@s.example.com">
     bait 0A000001-4432ba6f

DESCRIPTION
     Script can be used in two modes - 

     First, as a CGI script from within an html page to generate a hex
     code for the client IP address and timestamp.  Install in cgi-bin
     directory (or similar) and then link into pages with, for example,
     server-parsed HTML like so:

     <!-- DO NOT SEND EMAIL HERE: -->
     <a onclick="alert('WARNING - do not send email here')"
      style="text-decoration: none" 
      href="mailto:<!--#include virtual="/cgi-bin/bait" -->@s.example.com"
     ><font color="white">&nbsp;</font></a>
     <!-- END SPAM BAIT -->

     Second, as a command-line utility or CGI to decode a given hex code
     back into it's component IP address and time.

     $ bait 0A000001-4432ba6f
     Bait 0A000001-4432ba6f:
     Harvested on: Tue Apr  4 14:26:55 2006
     By: 10.0.0.1

};

if ($ENV{'REMOTE_ADDR'}) {
    showBait();
} elsif ($ARGV[0]) {
    decodeBait($ARGV[0]);
} else {
    print $usage;
}
exit 0;

sub showBait {    
    print 'Content-type: text/html

' . sprintf('%x', unpack
	    ('N', (pack('C4', split(/\./, $ENV{'REMOTE_ADDR'}))))) . '-' . 
		sprintf('%x', time());
}

sub decodeBait {
    use Socket;
    my($ip, $time) = split('-', $_[0]);

    print 'Bait ' . $_[0] . ':
Harvested on: ' . localtime(unpack('N', pack('H8', $time))) . '
By: ' . join('.', unpack('C4', pack('H8', $ip))) . '
';
}