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:
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Upload the Mobile App to Appdome.
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Upload an app to Appdome’s Mobile App Security Build System
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Upload Method: Appdome Console or DEV-API
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Android Formats: .apk or .aab
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Prevent App Repacking Compatible With: Java, JS, C++, C#, Kotlin, Flutter, React Native, Unity, Xamarin, Cordova and other Android apps
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Build the feature: Prevent App Repacking.
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Building Prevent App Repacking by using Appdome’s DEV-API:
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Create and name the Fusion Set (security template) that will contain the Prevent App Repacking feature as shown below:
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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.
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Open the Fusion Set Detail Summary by clicking the “...” symbol on the far-right corner of the Fusion Set. Copy 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). -
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, Circle CI or other system:
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Build an API for the app – for instructions, see the tasks under Appdome API Reference Guide
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Look for sample APIs in Appdome’s GitHub Repository
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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). -
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Building the Prevent App Repacking feature via Appdome Console
To build the Prevent App Repacking protection by using Appdome Console, follow the instructions below.
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Where: Inside the Appdome Console, go to Build > Security Tab > ONEShield™ section.
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How: Check whether is toggled On (enabled), otherwise enable it . The feature Prevent App Repacking is enabled by default, as shown below. Toggle (turn ON) Prevent App Repacking, as shown below.
Figure 3: Prevent App Repacking option
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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
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Click Build My App at the bottom of the Build Workflow (shown in Figure 3).
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Congratulations! The Prevent App Repacking protection is now added to the mobile app -
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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
Using Threat-Events™ for App Repacking Intelligence and Control in Android Apps
Appdome Threat-Events™ provides consumable in-app mobile app attack intelligence and defense control when App Repacking is detected. To consume and use Threat-Events™ for App Repacking in Android Apps, use registerReceiver in the Application OnCreate, and the code samples for Threat-Events™ for App Repacking shown below.
The specifications and options for Threat-Events™ for App Repacking are:
Threat-Event™ Elements | Prevent App Repacking Method Detail |
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Appdome Feature Name | Prevent App Repacking |
Threat-Event Mode | |
OFF, IN-APP DEFENSE | Appdome detects, defends and notifies user (standard OS dialog) using customizable messaging. |
ON, IN-APP DETECTION | Appdome detects the attack or threat and passes the event in a standard format to the app for processing (app chooses how and when to enforce). |
ON, IN-APP DEFENSE | Uses Appdome Enforce mode for any attack or threat and passes the event in a standard format to the app for processing (gather intel on attacks and threats without losing any protection). |
Certified Secure™ Threat Event Check | |
Visible in ThreatScope™ | |
Developer Parameters for Preventing App Repacking Threat-Event™ | |
Threat-Event NAME | AppIntegrityError |
Threat-Event DATA | reasonData |
Threat-Event CODE | reasonCode |
Threat-Event REF | 6801 |
Threat-Event SCORE | |
currentThreatEventScore | Current Threat-Event score |
threatEventsScore | Total Threat-events score |
Threat-Event Context Keys | |
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message | Message displayed for the user on event |
failSafeEnforce | Timed enforcement against the identified threat |
externalID | The external ID of the event which can be listened via Threat Events |
osVersion | OS version of the current device |
deviceModel | Current device model |
deviceManufacturer | The manufacturer of the current device |
fusedAppToken | The task ID of the Appdome fusion of the currently running app |
kernelInfo | Info about the kernel: system name, node name, release, version and machine. |
carrierPlmn | PLMN of the device. Only available for Android devices. |
deviceID | Current device ID |
reasonCode | Reason code of the occurred event |
buildDate | Appdome fusion date of the current application |
devicePlatform | OS name of the current device |
carrierName | Carrier name of the current device. Only available for Android. |
updatedOSVersion | Is the OS version up to date |
deviceBrand | Brand of the device |
deviceBoard | Board of the device |
buildUser | Build user |
buildHost | Build host |
sdkVersion | Sdk version |
timeZone | Time zone |
deviceFaceDown | Is the device face down |
locationLong | Location longitude conditioned by location permission |
locationLat | Location latitude conditioned by location permission |
locationState | Location state conditioned by location permission |
wifiSsid | Wifi SSID |
wifiSsidPermissionStatus | Wifi SSID permission status |
AntampIntegrityErrorMessage | Error message |
data | Data related to the security event |
certificateSHA1 | Failed certificate |
With Threat-Events™ enabled (turned ON), Android developers can get detailed attack intelligence and granular defense control in Android applications and create amazing user experiences for all mobile end users when App Repacking is detected.
The following is a code sample for native Android apps, which uses all values in the specification above for Prevent App Repacking:
x
IntentFilter intentFilter = new IntentFilter();
intentFilter.addAction("AppIntegrityError");
BroadcastReceiver threatEventReceiver = new BroadcastReceiver() {
public void onReceive(Context context, Intent intent) {
String message = intent.getStringExtra("message"); // Message shown to the user
String reasonData = intent.getStringExtra("reasonData"); // Threat detection cause
String reasonCode = intent.getStringExtra("reasonCode"); // Event reason code
String currentThreatEventScore = intent.getStringExtra("currentThreatEventScore"); // Current threat event score
String threatEventsScore = intent.getStringExtra("threatEventsScore"); // Total threat events score
String variable = intent.getStringExtra("<Context Key>"); // Any other event specific context key
​
// Your logic goes here (Send data to Splunk/Dynatrace/Show Popup...)
}
};
​
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.TIRAMISU) {
registerReceiver(threatEventReceiver, intentFilter, Context.RECEIVER_NOT_EXPORTED);
} else {
registerReceiver(threatEventReceiver, intentFilter);
}
x
val intentFilter = IntentFilter()
intentFilter.addAction("AppIntegrityError")
val threatEventReceiver = object : BroadcastReceiver() {
override fun onReceive(context: Context?, intent: Intent?) {
var message = intent?.getStringExtra("message") // Message shown to the user
var reasonData = intent?.getStringExtra("reasonData") // Threat detection cause
var reasonCode = intent?.getStringExtra("reasonCode") // Event reason code
var currentThreatEventScore = intent?.getStringExtra("currentThreatEventScore") // Current threat event score
var threatEventsScore = intent?.getStringExtra("threatEventsScore") // Total threat events score
var variable = intent?.getStringExtra("<Context Key>") // Any other event specific context key
​
// Your logic goes here (Send data to Splunk/Dynatrace/Show Popup...)
}
}
​
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.TIRAMISU) {
registerReceiver(threatEventReceiver, intentFilter, Context.RECEIVER_NOT_EXPORTED)
} else {
registerReceiver(threatEventReceiver, intentFilter)
}
const { ADDevEvents } = NativeModules;
const aDDevEvents = new NativeEventEmitter(ADDevEvents);
function registerToDevEvent(action, callback) {
NativeModules.ADDevEvents.registerForDevEvent(action);
aDDevEvents.addListener(action, callback);
}
export function registerToAllEvents() {
registerToDevEvent(
"AppIntegrityError",
(userinfo) => Alert.alert(JSON.stringify(userinfo))
var message = userinfo["message"] // Message shown to the user
var reasonData = userinfo["reasonData"] // Threat detection cause
var reasonCode = userinfo["reasonCode"] // Event reason code
var currentThreatEventScore = userinfo["currentThreatEventScore"] // Current threat event score
var threatEventsScore = userinfo["threatEventsScore"] // Total threat events score
var variable = userinfo["<Context Key>"] // Any other event specific context key
// Your logic goes here (Send data to Splunk/Dynatrace/Show Popup...)
);
}
RegisterReceiver(new ThreatEventReceiver(), new IntentFilter("AppIntegrityError"));
class ThreatEventReceiver : BroadcastReceiver
{
public override void OnReceive(Context context, Intent intent)
{
String message = intent.GetStringExtra("message"); // Message shown to the user
String reasonData = intent.GetStringExtra("reasonData"); // Threat detection cause
String reasonCode = intent.GetStringExtra("reasonCode"); // Event reason code
String currentThreatEventScore = intent.GetStringExtra("currentThreatEventScore"); // Current threat event score
String threatEventsScore = intent.GetStringExtra("threatEventsScore"); // Total threat events score
String variable = intent.GetStringExtra("<Context Key>"); // Any other event specific context key
// Your logic goes here (Send data to Splunk/Dynatrace/Show Popup...)
}
}
NSNotificationCenter.DefaultCenter.AddObserver(
(NSString)"AppIntegrityError", // Threat-Event Identifier
delegate (NSNotification notification)
{
var message = notification.UserInfo.ObjectForKey("message"); // Message shown to the user
var reasonData = notification.UserInfo.ObjectForKey("reasonData"); // Threat detection cause
var reasonCode = notification.UserInfo.ObjectForKey("reasonCode"); // Event reason code
var currentThreatEventScore = notification.UserInfo.ObjectForKey("currentThreatEventScore"); // Current threat event score
var threatEventsScore = notification.UserInfo.ObjectForKey("threatEventsScore"); // Total threat events score
var variable = notification.UserInfo.ObjectForKey("<Context Keys>"); // Any other event specific context key
// Your logic goes here (Send data to Splunk/Dynatrace/Show Popup...)
});
window.broadcaster.addEventListener("AppIntegrityError", function(userInfo) {
var message = userInfo.message // Message shown to the user
var reasonData = userInfo.reasonData // Threat detection cause
var reasonCode = userInfo.reasonCode // Event reason code
var currentThreatEventScore = userInfo.currentThreatEventScore // Current threat event score
var threatEventsScore = userInfo.threatEventsScore // Total threat events score
var variable = userInfo.<Context Key> // Any other event specific context key
// Your logic goes here (Send data to Splunk/Dynatrace/Show Popup...)
});
xxxxxxxxxx
import 'dart:async';
​
import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
​
class PlatformChannel extends StatefulWidget {
const PlatformChannel({super.key});
​
State<PlatformChannel> createState() => _PlatformChannelState();
}
​
class _PlatformChannelState extends State<PlatformChannel> {
static const String _eventChannelName = 'AppIntegrityError'; // Replace with your EventChannel name
static const EventChannel _eventChannel = EventChannel(_eventChannelName);
​
void initState() {
super.initState();
_eventChannel.receiveBroadcastStream().listen(_onEvent, onError: _onError);
}
​
void _onEvent(Object? event) {
setState(() {
// Adapt this section based on your specific event data structure
var eventData = event as Map;
​
// Example: Accessing 'externalID' field from the event
var externalID = eventData['externalID'];
​
// Customize the rest of the fields based on your event structure
String message = eventData['message']; // Message shown to the user
String reasonData = eventData['reasonData']; // Threat detection cause
String reasonCode = eventData['reasonCode']; // Event reason code
String currentThreatEventScore = eventData['currentThreatEventScore']; // Current threat event score
String threatEventsScore = eventData['threatEventsScore']; // Total threat events score
​
// Any other event specific context key
String variable = eventData['<Context Key>'];
});
}
​
// Your logic goes here (Send data to Splunk/Dynatrace/Show Popup...)
}
Using Appdome, there are no development or coding prerequisites to build secured Android Apps by using Prevent App Repacking. There is no SDK and no library to code or implement in the app and no gateway to deploy in your network. All protections are built into each app and the resulting app is self-defending and self-protecting.
Releasing and Publishing Mobile Apps with Prevent App Repacking
After successfully securing your app by using Appdome, there are several available options to complete your project, depending on your app lifecycle or workflow. These include:
- Customizing, Configuring & Branding Secure Mobile Apps
- Deploying/Publishing Secure mobile apps to Public or Private app stores
- Releasing Secured Android & iOS Apps built on Appdome.
Related Articles:
- How to Block Runtime Code Manipulations in Android & iOS Apps
- How to Prevent Debuggable Android & iOS Apps in Production
- Running a Checksum Validation of Android & iOS Apps
- How to Prevent Android Apps from Running on Emulators
- How to Prevent iOS Apps from Running on Emulators
How Do I Learn More?
If you have any questions, please send them our way at support.appdome.com or via the chat window on the Appdome platform.
Thank you!
Thanks for visiting Appdome! Our mission is to secure every app on the planet by making mobile app security easy. We hope we’re living up to the mission with your project.