Decoder for Dean Edwards' JavaScript Packer

Igor Krupitsky

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4 Mar 2010CPOL

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This short article shows how to decrypt and beautify code encoded with Dean Edwards' Javascript Packer.

Download Decoder - 518 B

Introduction

If you are a website admin, you might want to know if the JavaScript provided to you is malicious. This code will decrypt the JavaScript code encrypted with Dean Edwards' Javascript Packer. JavaScript encoded with Dean Edwards' JavaScript Packer begins with this line:

JavaScript

eval(function(p,a,c,k,e,d){e=function(c){

Using the Code

This code is a simple HTML page with few lines of JavaScript.

HTML

<html xmlns="http://www.w3.org/1999/xhtml" >
<head>
<title>Decoder for Dean Edwards' Javascript Packer</title>
<script language="javascript" type="text/javascript">
function Decode() {
eval("var value=String" + txtInput.value.slice(4));
txtOutput.value = value;
}
</script>
</head>
<body>
<div>Input</div>
<textarea id="txtInput" style="width: 632px; height: 253px"></textarea>
<br />
<input id="btnDecode" style="width: 198px" 
type="button" value="Decode" onclick="Decode()" />
<br />
<div>Output</div>
<textarea id="txtOutput" style="width: 630px; height: 273px"></textarea>
<br />
<a href="http://dean.edwards.name/packer/">Dean Edwards' JS packer</a>
<br />
<a href="http://jsbeautifier.org/">Javascript unpacker and beautifier</a>
</body>
</html>

Points of Interest

After you decode the JavaScript with the page, beautify it with Javascript unpacker and beautifier.

You can read more about Dean Edwards' JS packer's inner workings on Golan Yosef blog.

History

5^th March, 2010: Initial post

License

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

Written By

Igor Krupitsky

Web Developer

United States

Igor is a business intelligence consultant working in Tampa, Florida. He has a BS in Finance from University of South Carolina and Masters in Information Management System from University of South Florida. He also has following professional certifications: MCSD, MCDBA, MCAD.

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