apktool

Description

A tool for reverse engineering Android APK files. It can decompile APKs into their constituent resources and smali code, and recompile (rebuild) modified APKs back into installable packages.

Usage 1: Decompile an APK

Decompiles the APK file into a folder containing smali files, resources, and the AndroidManifest.xml.

Command:

apktool d example.apk

Or using the jar directly:

apktool.jar d example.apk

Usage 2: Recompile (Build) a Modified APK

After modifying smali code or resources, rebuild the APK from the decompiled folder. The rebuilt APK will be placed in the dist folder inside the app directory.

Command:

apktool.jar b myapp

Usage 3: Sign the Rebuilt APK

After rebuilding, the APK must be signed before it can be installed. First generate a keystore, then sign the APK with it.

Generate a Keystore:

"C:\Program Files\Java\jdk-21\bin\keytool.exe" -genkey -keystore keystorehere -validity 1000 -alias yaqoob -keyalg rsa

Sign the APK:

"C:\Program Files\Java\jdk-21\bin\jarsigner.exe" -keystore keystorehere -verbose myapp\dist\myapp.apk yaqoob

Verify the Signature:

"C:\Program Files\Java\jdk-21\bin\jarsigner.exe" -verify -verbose -certs app.apk

Notes

• After decompilation, smali files can be found at smali>com>example>name>myapplication>mainactivity.smali and the assembly code can be modified there.
• Smali files are assembled (bytecode-level) representations of the Android Dalvik code.
• The rebuilt APK in the dist folder must be signed before installation on a device.