Friday, June 14, 2013

Android Application Reverse Engineering. Reversing Angry Birds.

Ok, so this article has been a long time coming.
One of my pastimes is reverse engineering Android applications, just to see “what makes them tick”. In this article, in order to really drive this home, I will reverse engineer the popular “Angry Birds” application.
Due to time constraints and basic laziness, I went for the first APK I could find – Angry Birds in Space.
Also, before anyone asks, in the following article I will NOT be releasing the Angry Birds source code. I simply am using it as a demo :)
First off, you will want to have the Unix “unzip” utility installed. We will be using this to unpack the .apk file.
Second, grab the following pieces of software:
dex2jar – – for converting the .dex file into a .jar file :)
jd-gui – – For decompiling the (.jar) Java file into its (.java) source code :)
Now, the idea behind this article is NOT to teach you to crack apps. Instead, this is the skillset needed to reverse engineer Android Malware – as seen in my previous post –
So. You have your .apk file, the first thing we do is use the GNU Unzip utility to unpackage it!
$ unzip Angry_Birds_Space_Premium_1.3.0.apk
Next, use the utility from dex2jar to convert classes.dex to a JAR file.
$ ./dex2jar- classes.dex
Screenshot of the above 2 steps (I piped output to /dev/null to avoid MASSIVE SPAM OF DATA)
unzip and dex2jar
Next, we simply open the .JAR file using jd-gui.
Decompiling the JAR file
Finally we can simply export the source code from jd-gui for our viewing, and editing pleasure :)
So. In conclusion
  • Android applications are trivial to reverse engineer
  • Software for decompiling them is readily available
  • Fun times :D


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