Using Integer Multiplication to Protect Web Forms with Ajax - The application's full source code (
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As I said in the section that you just read, below I listed all of the source code that corresponds to this Ajax-based application, which implements a simple mathematical mechanism that protects a web form from possible hacks. Here are all of the files that comprise the program:
(definition of 'sample_form.htm' file)
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" />
<title>Ajax-based challenge strings generator</title>
<style type="text/css">
body{
padding: 0;
margin: 0;
background: #fff;
}
h1{
font: bold 16pt Arial, Helvetica, sans-serif;
color: #000;
}
p{
font: bold 9pt Arial, Helvetica, sans-serif;
color: #000;
}
#formbox{
width: 380px;
text-align: right;
padding: 10px;
background: #eee;
}
#codebox{
font: bold 18pt Arial, Helvetica, sans-serif;
color: #00f;
}
.inputbox,textarea{
width: 300px;
border: 1px solid #999;
}
.checkingcode{
width: 50px;
border: 1px solid #999;
}
</style>
<script language="javascript" src="jquery.js"></script>
<script language="javascript">
$(document).ready(function(){
// get verification code with Ajax
$.get('get_checkingcode.php',{data:'getting code'},function(checkingcode){$('#codebox').html(checkingcode);});
});
</script>
</head>
<body>
<h1>Ajax-based challenge strings generator</h1>
<div id="formbox">
<form action="check_form.php" method="post">
<p>First Name <input type="text" class="inputbox" title="Enter your first name" /></p>
<p>Last Name <input type="text" class="inputbox" title="Enter your last name" /></p>
<p>Email <input type="text" class="inputbox" title="Enter your email address" /></p>
<p>Enter your comments below:</p>
<p><textarea title="Enter your comments" rows="10" cols="10"></textarea></p>
<div id="codebox"></div>
<p>Verification Code: <input type="text" name="code" class="checkingcode" title="Multiply the above digits and enter the result" /></p>
<p><input type="submit" value="Send Data"></p>
</form>
</div>
</body>
</html>
(definition of 'get_checkingcode.php' file)
<?php
session_start();
$valuea=rand(1,10);
$valueb=rand(1,10);
$_SESSION['checkcode']=$valuea*$valueb;
echo $valuea.' x '.$valueb;
?>
(definition of 'check_form.php' file)
<?php
session_start();
if($_SESSION['checkcode']==$_POST['code']){
echo 'Correct verification code!';
}
else{
echo 'Incorrect verification code!';
}
?>
Undoubtedly, the set of source files shown above demonstrates how easy it is to build an Ajax application that generates a multiplication problems to make a targeted web form a bit more secure.
Below I've included a couple of complementary images that show how these challenge calculations are displayed when the previous sample form is being filled in with some trivial data:
Of course, there's plenty of room for enhancing this Ajax-driven program, for instance, by embedding these operations directly into an image generated dynamically. But this improvement, and others, will be left as homework for you. In this case one thing is for sure: fun is already guaranteed!
Final thoughts
In this third episode of the series, I walked you through the development of an Ajax-driven application, which was capable of displaying multiplication problems within a targeted web form to protect it against malicious, automated submissions.
In the last chapter, I'll be building a similar program for protecting HTML forms, but this time it'll generate divisions as challenge strings. Thus, now that you've been warned about the subject of the next part, you won't want to miss it!
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