decompiling DEX into Java sourcecode

Question

How can one decompile Android DEX (VM bytecode) files into corresponding Java sourcecode?

Answer 1

To clarify somewhat, there are two major paths you might take here depending on what you want to accomplish:

Decompile the Dalvik bytecode (dex) into readable Java source. You can do this easily with dex2jar and jd-gui, as fred mentions. The resulting source is useful to read and understand the functionality of an app, but will likely not produce 100% usable code. In other words, you can read the source, but you can't really modify and repackage it. Note that if the source has been obfuscated with proguard, the resulting source code will be substantially more difficult to untangle.

The other major alternative is to disassemble the bytecode to smali, an assembly language designed for precisely this purpose. I've found that the easiest way to do this is with apktool. Once you've got apktool installed, you can just point it at an apk file, and you'll get back a smali file for each class contained in the application. You can read and modify the smali or even replace classes entirely by generating smali from new Java source (to do this, you could compile your .java source to .class files with javac, then convert your .class files to .dex files with Android's dx compiler, and then use baksmali (smali disassembler) to convert the .dex to .smali files, as described in this question. There might be a shortcut here). Once you're done, you can easily package the apk back up with apktool again. Note that apktool does not sign the resulting apk, so you'll need to take care of that just like any other Android application.

If you go the smali route, you might want to try APK Studio, an IDE that automates some of the above steps to assist you with decompiling and recompiling an apk and installing it on a device.

In short, your choices are pretty much either to decompile into Java, which is more readable but likely irreversible, or to disassemble to smali, which is harder to read but much more flexible to make changes and repackage a modified app. Which approach you choose would depend on what you're looking to achieve.

Lastly, the suggestion of dare is also of note. It's a retargeting tool to convert .dex and .apk files to java .class files, so that they can be analyzed using typical java static analysis tools.

Answer 2

Once you downloaded your APK file , You need to do the following steps to get a editable java code/document.

1. Convert your apk file to zip (while start your download don't go with "save" option , just go with "save as" and mention your extension as .zip) by doing like this you may avoid APKTOOL...
2. Extract the zip file , there you can find somefilename.dex. so now we need to convert dex -> .class
3. To do that, you need "dex2jar"(you can download it from http://code.google.com/p/dex2jar/ , after extracted, in command prompt you have to mention like, [D:\dex2jar-0.09>dex2jar somefilename.dex] (Keep in mind that your somefilename.dex must be inside the same folder where you have keep your dex2jar.)
4. Download jad from http://www.viralpatel.net/blogs/download/jad/jad.zip and extract it. Once extracted you can see two files like "jad.exe" and "Readme.txt" (sometimes "jad.txt" may there instead of "jad.exe", so just rename its extension as.exe to run)
5. Finally, in command prompt you have to mention like [D:\jad>jad -sjava yourfilename.class] it will parse your class file into editable java document.

Answer 3

You might try JADX (https://bitbucket.org/mstrobel/procyon/wiki/Java%20Decompiler), this is a perfect tool for DEX decompilation.

And yes, it is also available online on (my :0)) new site: http://www.javadecompilers.com/apk/

Answer 4

^{A more complete version of fred's answer:}

Manual way

First you need a tool to extract all the (compiled) classes on the DEX to a JAR.
There's one called dex2jar, which is made by a chinese student.

Then, you can use jd-gui to decompile the classes on the JAR to source code.
The resulting source should be quite readable, as dex2jar applies some optimizations.

Automatic way

You can use APKTool. It will automatically extract all the classes (.dex), resources (.asrc), then it will convert binary XML to human-readable XML, and it will also dissassemble the classes for you.
Disassembly will always be more robust than decompiling, especially with
JARs obfuscated with Pro Guard!

Just tell APKTool to decode the APK into a directory, then modify what you want,
and finally encode it back to an APK. That's all.

Important: APKTool dissassembles. It doesn't decompile.
The generated code won't be Java source.
But you should be able to read it, and even edit it if you're familiar with jasmin.
If you want Java source, please go over the Manual way.

Answer 5

Android Reverse Engineering is possible . Follow these steps to get .java file from apk file.

Step1 . Using dex2jar

• Generate .jar file from .apk file
• command : dex2jar sampleApp.apk

Step2 . Decompiling .jar using JD-GUI

• it decompiles the .class files i.e., we'll get obfuscated .java back from the apk.