android-babel-sample

Songtive uses Xamarin as main framework for music related applications. We chosed OS X to unify the whole development for both platforms: iOS and Android. That being said, we had to configure the packaging and obfuscating process right from OS X. For obfuscating we selected https://babelfor.net/ which just works greatly without any additional tweaks. Babel provides Task for MSBuild to obfuscate your app but Tasks doesn’t work for well for Xamarin.Studio. So you are stuck to use only custom commands or custom Targets in csproj.

This document is step by step guide how to integrate Babel into your Android APK build process.

First of all, we have to create a bash file which starts the build process and prepares APK:

#!/bin/bash

cd ../BabelTest

# clean project
xbuild BabelTest.csproj /p:Configuration=Release /t:Clean

# build and sign APK
xbuild BabelTest.csproj /p:Configuration=Release /t:SignAndroidPackage

Run it to check if script works as expected and generates APK: BabelTest/bin/com.companyname.babeltest-Signed.apk

Let’s move forward and include intermediate script to obfuscate assemblies before packing APK using the following Target in BabelTest.csproj:

  <Target Name="Obfuscate" AfterTargets="_CopyIntermediateAssemblies" Condition="'$(Configuration)' == 'Release'">
    <Exec Command="obfuscate" WorkingDirectory="../scripts" />
  </Target>

Please note that this Target is used only in Release mode and after “_CopyIntermediateAssemblies” which basically copies all assemblies into /BabelTest/obj/Release/assemblies.

The obfuscate script is located in ./scripts directory and has the following content:

#!/bin/bash
BABEL_PATH=./babel.exe
SRC=../BabelTest/obj/Release/assemblies

mono $BABEL_PATH --unicode s,_ $SRC/BabelTest.dll $SRC/BabelLibrary.dll --output $SRC/BabelTest.dll

# prepare stub assembly
mcs -t:library -out:$SRC/BabelLibrary.dll stub.cs

We specify to Babel that we are going to merge our library right into Android application and obfuscate them together. Since Xamarin is still trying to load BabelLibrary during packaging - we generate stub assembly with empty class and overwrite it.

Let’s run /script/build again and unzip APK to get /assemblies/BabelTest.dll. Use ILSpy to see what we have here:

Your assemblies are obfuscated.