Proj 14: mAadhaar Code Modification (20 pts)

What You Need for This Project

Purpose

To modify the Indian government app mAadhaar so it runs on a rooted device.

This will give us practice using apktool and Jadx.

This tutorial follows a tweetstream by @fs0c131y.

Note for Windows Users

Use Nox, not Bluestacks, because you need to be root.

Task 1: Getting the App

Download the APK

The app doesn't appear in Google Play in the USA, so download the APK from this page:

https://www.apkmonk.com/app/in.gov.uidai.mAadhaarPlus/

You should get this file: in.gov.uidai.mAadhaarPlus_2018-09-26.apk

If you are doing this project after Jan. 2019, the app may have been updated. If you want the APK file I used, you can get it here.

Installing the App

Launch Kali. Connect it to your Genymotion device with adb. Copy the APK file into Kali.

On Kali, execute this command:

adb install in.gov.uidai.mAadhaarPlus_2018-09-26.apk 
The installation succeeds, as shown below.

Running the App

On your Genymotion device, launch the mAadhaar app.

A message appears on your phone telling you that you cannot use this app, as shown below.


Task 2: Using Jadx to Read the Code

You can use 64-bit Windows or Kali Linux to run Jadx. Choose one of them and follow the instructions below.

Using 64-Bit Windows

Launch your Windows machine. (Jadx is Java-based, so it should run on other platforms also, but I wrote these instructions using Windows.) Copy the in.gov.uidai.mAadhaarPlus_2018-09-26.apk file into your Windows machine.

Installing Java

First open Control Panal and uninstall all old Java versions.

Then open a Web browser and go here:

https://java.com/en/download/manual.jsp

Download "Windows Offline (64-bit)" version and install it. as shown below.

Installing Jadx on Windows

Go here:

https://github.com/skylot/jadx/releases/tag/v0.8.0

Download jadx-gui, as shown below.

Launch Jadx.

Using Kali

In Kali, execute these commands:
git clone https://github.com/skylot/jadx.git
cd jadx
./gradlew dist
./build/jadx/bin/jadx-gui

Examining the Android Manifest

In Jadx, open the in.gov.uidai.mAadhaarPlus_2018-09-26.apk file.

In the left pane, at the bottom expand Resources.

Click AndroidManifest.xml.

The contents appear on the right side, as shown below.

Notice that the LAUNCHER activity, which runs when the app launches, is

in.gov.uidai.mAadhaarPlus.ui.activity.SplashScreenActivity

as outlined in green in the imager below.

According to the official Android documentation , the first method called when an activity is launched is the "onCreate" method, as shown at the top of the diagram below.

Reading the onCreate Method

In the left pane, in the top section, expand these items, as shown below. Click SplashScreenActivity, as shown below.

In the right pane, scroll down to the OnCreate() method.

Notice the two code sections outlined in green in the image below.

The first section is Integrity Verfication, using methods named f.a and f.b to detect app modification.

The second section uses a method named b to detect rooted devices.

We want to disable both these operations.

Finding the Integrity Verification Code

The routine to detect an altered app is "f.a". Scroll to the top of the SplashScreenActivity code, and you can see that this module imports

in.gov.uidai.mAadhaarPlus.ui.activity.b.f

as shown below.

In the left pane, scroll up and navigate to that module. Here you can find the a() method, as shown below.

This module compares a SHA-256 hash with a hard-coded value to see if the app has been modified.


Task 3: Modifying the App

Checking apktool Version

In Kali, execute this command:
apktool 
You need version "v2.3.3-dirty", as shown below. Version 2.3.4 does NOT work.

If you have version 2.3.4, execute this command to get the older version:

wget https://bitbucket.org/iBotPeaches/apktool/downloads/apktool_2.3.3.jar
And instead of using "apktool" in the commands below, use "java -jar apktool_2.3.3.jar".

Unpacking the APK

Copy the in.gov.uidai.mAadhaarPlus_2018-09-26.apk file into Kali.

On Kali, execute this command:

apktool d -f -r in.gov.uidai.mAadhaarPlus_2018-09-26.apk

Disabling Integrity Control

First we need to find the code to modify.

On Kali, execute this command:

grep SplashScreenActivity -r . | less -S
The main smali file path appears, highlighted in the image below.

Press Q to exit "less".

Execute this command to edit the file:

nano ./in.gov.uidai.mAadhaarPlus_2018-09-26/smali/in/gov/uidai/mAadhaarPlus/ui/activity/SplashScreenActivity.smali
Scroll down and find the code shown below.

This code calls the f->a and f->b methods, highlighted in yellow in the image below.

If the app is modified, the code sets the parameter "p1" to zero, as highlighted in light gray in the image below.

Change the 0x0 value to 0x1, outlined in green in the image below.

This modification allows us to change the app without being detected.

Disabling Root Detection

Scroll down a few lines and find the code shown below.

This code calls a scottyab RootBeer function to detect a rooted phone. If the phone is rooted, it kills the app.

To prevent that, add # characters to comment out the nine lines colored blue in the image below.

Now the app will run on a rooted phone.

Rebuilding the App

On Kali, execute this command:
apktool b in.gov.uidai.mAadhaarPlus_2018-09-26
The file builds without errors, as shown below.

Making a Code Signing Certificate

Android won't run unsigned apps, so we need a signing certificate.

Execute this command:

keytool -genkey -v -keystore my-release-key.keystore -alias alias_name -keyalg RSA -keysize 2048 -validity 10000
A prompt asks for a "keystore password". Enter password twice.

Then a series of question asks for your name, etc. You can press Enter for each question except the last one, which you must answer yes to, as shown below.

Signing the APK

On Kali, execute this command:
jarsigner -sigalg SHA1withRSA \
-digestalg SHA1 -keystore my-release-key.keystore \
in.gov.uidai.mAadhaarPlus_2018-09-26/dist/in.gov.uidai.mAadhaarPlus_2018-09-26.apk alias_name
Enter the password of password when you are prompted to.

The app is signed, as shown below.

Uninstalling the Old App

On your Genymotion virtual Android device, open Settings and tap these items.

Installing the Modified App

On Kali, execute this command:
adb install in.gov.uidai.mAadhaarPlus_2018-09-26/dist/in.gov.uidai.mAadhaarPlus_2018-09-26.apk 
The installation succeeds, as shown below.

Launching the App

On your Genymotion device, launch the mAadhaar app.

It asks whether it can make phone calls. Click ALLOW.

In the "mAadhaar Consent" page, click OK.

In the "Usage Guidelines" page, at the top left, click the leftware-pointing arrow.

You see the app's starting screen, as shown below.

Saving a Screen Image

Make sure you can see the start screen, as shown above.

Save a full-desktop image. On a Mac, press Shift+Commmand+3. On a PC, press Shift+PrntScrn and paste into Paint.

YOU MUST SUBMIT A FULL-SCREEN IMAGE FOR FULL CREDIT!

Save the image with the filename "YOUR NAME Proj 14", replacing "YOUR NAME" with your real name.

Turning in your Project

Email the image to to cnit.128sam@gmail.com with the subject line: Proj 14 from YOUR NAME

Source

How to remove the root detection and the anti tampering mechanism from the mAadhaar app by @fs0c131y.
Posted 1-30-19
Linux Jadx instructions added 2-12-19
Apktool version added 3-11-19
Emulator specifications updated at top 4-3-19