How to Block Resigning and Repackaging Android Apps

Learn to Prevent App Repacking in Android apps, in mobile CI/CD with a Data-Driven DevSecOps™ build system.

What is App Repackaging?

App repacking involves hackers manipulating an app’s original code or injecting harmful code into it, subsequently repackaging this altered app for distribution. By actively preventing app repacking, you not only preserve the authenticity and originality of your app but also ensure the continuous safety and trust of your users.

To ensure your app is protected against unauthorized changes or any modification that can compromise them is critical. Some examples are:

• Repackaging the app
• Resigning the application
• Modifying the application’s executable
  • iOS: Main executable (see structure of an iOS application)
  • Android: DEX files (see structure of an Android application)
• Attempting to Modify the Appdome adapter
• Moving the application’s sandbox under the name of a different package

Why Prevent App Repacking in Android Apps??

Tamper prevention against app repackaging protects your app against unwanted changes, mods, and hacks  that can negative impact or compromise your mobile business application including financial and data loss, intellectual privacy & repetitional damage. Appdome prevents all this without adding development work or time to your release cycles.  This is done by sealing your app and actively detecting modifications during initialization and at multiple other points during run-time.

Prerequisites for Using Prevent App Repacking:

To use Appdome’s mobile app security build system to Prevent App Repacking , you’ll need:

• Appdome account (create a free Appdome account here)
• A license for Prevent App Repacking
• Mobile App (.apk or .aab for Android)
• Signing Credentials (see Signing Secure Android apps and Signing Secure iOS apps)

Prevent App Repacking on Android apps using Appdome

On Appdome, follow these 3 simple steps to create self-defending Android Apps that Prevent App Repacking without an SDK or gateway:

1. Upload the Mobile App to Appdome.

   1. Upload an app to Appdome’s Mobile App Security Build System

   2. Upload Method: Appdome Console or DEV-API
   3. Android Formats: .apk or .aab
   4. Prevent App Repacking Compatible With: Java, JS, C++, C#, Kotlin, Flutter, React Native, Unity, Xamarin, Cordova and other Android apps

2. Build the feature: Prevent App Repacking.

   1. Building Prevent App Repacking by using Appdome’s DEV-API:

      1. Create and name the Fusion Set (security template) that will contain the Prevent App Repacking feature as shown below:
      

      Figure 1: Fusion Set that will contain the Prevent App Repacking feature
      Note: Naming the Fusion Set to correspond to the protection(s) selected is for illustration purposes only (not required).

      2. Follow the steps in Sections 2.2.1-2.2.2 of this article, Building the Prevent App Repacking feature via Appdome Console, to add the Prevent App Repacking feature to this Fusion Set.

      3. Open the Fusion Set Detail Summary by clicking the “...” symbol on the far-right corner of the Fusion Set, as shown in Figure 1 above, and get the Fusion Set ID from the Fusion Set Detail Summary (as shown below):

         Figure 2: Fusion Set Detail Summary
         Note: Annotating the Fusion Set to identify the protection(s) selected is optional only (not mandatory).

      4. Follow the instructions below to use the Fusion Set ID inside any standard mobile DevOps or CI/CD toolkit like Bitrise, App Center, Jenkins, Travis, Team City, Cirlce CI or other system:

         1. Build an API for the app – for instructions, see the tasks under Appdome API Reference Guide
         2. Look for sample APIs in Appdome’s GitHub Repository

   2. Building the Prevent App Repacking feature via Appdome Console

      To build the Prevent App Repacking protection by using Appdome Console, follow the instructions below.

      1. Where: Inside the Appdome Console, go to Build > Security Tab > ONEShield™ section.

         Like all other options in ONEShield™, Prevent App Repacking is turned on by default, as shown below:

         Figure 3: Prevent App Repacking option
         Note: The App Compromise Notification contains an easy to follow default remediation path for the mobile app end user. You can customize this message as required to achieve brand specific support, workflow or other messaging.

      2. How: Toggle (turn ON) Prevent App Repacking, as shown below.

         Figure 3: Prevent App Repacking option

      3. When you select the Prevent App Repacking you'll notice that your Fusion Set you created in step 2.1.1 now bears the icon of the protection category that contains Prevent App Repacking

         

         Figure 4: Fusion Set that displays the newly added Prevent App Repacking protection

      4. Click Build My App at the bottom of the Build Workflow (shown in Figure 3).

   Congratulations!  The Prevent App Repacking protection is now added to the mobile app

3. Certify the Prevent App Repacking feature in Android Apps.

   After building Prevent App Repacking, Appdome generates a Certified Secure™ certificate to guarantee that the Prevent App Repacking protection has been added and is protecting the app. To verify that the Prevent App Repacking protection has been added to the mobile app, locate the protection in the Certified Secure™ certificate as shown below:

   Figure 5: Certified Secure™ certificate

   Each Certified Secure™ certificate provides DevOps and DevSecOps organizations the entire workflow summary, audit trail of each build, and proof of protection that Prevent App Repacking has been added to each Android app. Certified Secure provides instant and in-line DevSecOps compliance certification that Prevent App Repacking and other mobile app security features are in each build of the mobile app