android decompilation tools and methods

Foreword

Sometimes during the development process, you will encounter some functions that you don’t know how to do. However, other software already has them. At this time, you can use decompilation to unlock other programs to understand some of them. At the same time, you can also learn from other people’s software structures, resource files, etc., haha. Then I will explain some knowledge about decompilation, mainly divided into three parts. The first part introduces the tools and methods of decompilation, the second part introduces the syntax of smali, and the third part introduces how to prevent decompilation, mainly through this A few articles to learn how to do decompilation and code reinforcement.

Tools

apktools - the most powerful decompilation tool at present

Easily decompile apk, parse out resource files, xml files, generate smali files, and you can also use the modified files to generate apk.

Support windows, linux, mac.

Download address: https://code.google.com/p/android-apktool/downloads/list Please bring your own ladder

dex2jar

Convert the dex file in the apk into a jar file. Many people will not read smali files, it is more comfortable to look at java class files. At this time, you can use this tool to convert to java, which also supports windows, linux, and mac.

Download address: http://code.google.com/p/dex2jar/downloads/list

jd-gui

View the jar file, you can basically see the java class file, and it also supports mac, windows, and linux.

Download address: http://jd.benow.ca/

apktool command line comprehensive tool recommendation apktool plus

is actually a tool written by others, which integrates the functions of apktool and also supports signing apk. The latest version is v9update6, which only supports Windows systems.

Download address: http://dl.dbank.com/c0jndlkbu4#

Decompile

Use apktools

Execute the following command in the apktools directory

./apktool d pathtoapk outdir #mac linux
apktool.bat d pathtoapk outdir #window

In this way, the decompilation can be successful. You can view the resource files and smali files. Of course, some apps have undergone special processing, and not all of them can be decompiled.

At the same time, apktool can also reverse the decompiled file into an apk file with the following format.

./apktool b apppath outpath

If the reversed file is unsigned, it needs to be signed before it can be installed.

Use dex2jar

The apk file itself is actually a zip compressed package. First, let’s change the apk into a .zip file and decompress it to get a classes.dex. Go to the directory of dex2jar and execute the following command.

./d2j-dex2jar.sh pathtoclasses.dex #mac linux
d2j-dex2jar.bat pathtoclasses.dex #wind

After that, a jar file will be generated, which can be opened with jd-gui You can see the java code in it.

Others

In fact, the decompilation we use is enough. Usually we cannot obtain a lot of code. After all, others have measures to deal with it.