Black Hat

One week before my demo at the Black Hat Arsenal I released a peepdf challenge. The idea was solving the challenge using just peepdf, of course ;) This post will tell you how to solve the challenge so if you want to try by yourself (you should!) STOP READING HERE! The PDF file can be downloaded from here and it is not harmful. No shellcodes, no exploits, no kitten killed. In summary, you can open it with no fear, but do it with a version of Adobe Reader prior to XI ;)

Let's start! :) This is what you see with the last version of peepdf:

In a quick look you can spot some Javascript code located in object 13 and also an embedded file in the same object. Checking the references to this object and some info about it we see that it is an embedded PDF file:

In one week I will be traveling to Las Vegas to show how peepdf works in the Black Hat USA Arsenal. My time slot will be on Wednesday the 5th from 15:30 to 18:00, so you are more than welcome to come by and say hi, ask questions or just talk to me. I will also be presenting some of the work Rohit Dua is doing during the Google Summer of Code (GSoC), adding a scoring system for peepdf.

Two months ago Google announced that Google Code was slowly dying: no new projects can be created, it will be read only soon and in January 2016 the project will close definitely. peepdf was hosted there so it was time to move to another platform. The code is currently hosted at GitHub, way more active than Google Code:

https://github.com/jesparza/peepdf

If you are using peepdf you must update the tool because it is pointing to Google Code now. After executing “peepdf.py -u” the tool will point to GitHub and it will be able to be up to date with the latest commits. The peepdf Google Code page will also point to GitHub soon.

Another important announcement is that Rohit Dua will be the student who will work with peepdf this summer in the Google Summer of Code (GSoC). I initially presented three ideas to improve peepdf through The Honeynet Project:

• Project 12 - PEEPDF1: Improve PDF filters in peepdf

As I already announced in the last blog post, I was in Las Vegas giving a workshop about how to analyze exploit kits and PDF documents at BlackHat. The part related to exploit kits included some tips to analyze obfuscated Javascript code manually and obtain the exploit URLs or/and shellcodes. The tools needed to accomplish this task were just a text editor, a Javascript engine like Spidermonkey, Rhino or PyV8, and some tool to beautify the code (like peepdf ;p). In a generic way, we can say that the steps to analyze an exploit kit page are the following:
 

• Removing unnecessary HTML tags
• Convert HTML elements which are called in the Javascript code to Javascript variables
• Find and replace eval functions with prints, for example, or hook the eval function if it is possible (PyV8)
• Execute the Javascript code
• Beautify the code
• Find shellcodes and exploit URLs
• Repeat if necessary

 
BlackHat USA 2013 is here and tomorrow I will be explaining how to analyze exploit kits and PDF documents in my workshop “PDF Attack: From the Exploit Kit to the Shellcode” from 14:15 to 16:30 in the Florentine room. It will be really practical so bring your laptop and expect a practical session ;) All you need is a Linux distribution with pylibemu and PyV8 installed to join the party. You can run all on Windows too if you prefer.

Now Spidermonkey is not needed because I decided to change the Javascript engine to PyV8, it really works better. Take a look at the automatic analysis of the Javascript code using Spidermonkey (left) and PyV8 (right).