Dex Relocation, Anti-Reversing for Android Apps

Last updated November 29, 2023 by Appdome

This Knowledge Base article describes how to use Appdome’s AI/ML in your CI/CD pipeline to continuously deliver plugins that Use Dex Relocation in Android apps.

What is Dex Relocation?

In Android, compiled Java/Kotlin code resides in classes.dex files. Appdome’s Dex Relocation refers to a security technique that modifies a mobile app’s compiled code by obfuscating the logical control flow, thereby protecting Android apps against static code analysis and other forms of reverse engineering. The purpose of Dex relocation is to make reverse engineering tools ineffective and even unusable, making the code difficult to trace and understand.

Why Use Appdome's Dex Relocation?

Implementing Appdome’s Dex Relocation offers a crucial layer of protection for Android apps. By obfuscating the logical flow of the compiled code, it deters potential attackers by making the code significantly more difficult to decipher and exploit. In essence, Dex Relocation ensures the application’s integrity, safeguards user data, and protects the developer’s intellectual assets. To do this, Appdome uses several techniques such as applying call obfuscation to the compiled Java code and modifying the function call targets to obscure functions.

Appdome’s Dex Relocation doesn’t operate in isolation. When combined with Appdome’s TotalCode Obfuscation techniques, a reinforced protective layer emerges. These techniques complement and fortify each other, resulting in a comprehensive defense strategy that offers heightened resistance against potential threats.

Prerequisites for Using Appdome's Dex Relocation Plugins:

To use Appdome’s mobile app security build system to Use Dex Relocation , you’ll need:

How to Implement Use Dex Relocation in Android Apps Using Appdome

On Appdome, follow these 3 simple steps to create self-defending Android Apps that Use Dex Relocation without an SDK or gateway:

  1. Designate the Mobile App to be protected.

    1. Upload an app via the Appdome Mobile Defense platform GUI or via Appdome’s DEV-API or CI/CD Plugins.

    2. Android Formats: .apk or .aab
    3. Dex Relocation is compatible with: Java, JS, C++, C#, Kotlin, Flutter, React Native, Unity, Xamarin, Cordova and other Android apps.
  2. Select the defense: Dex Relocation.

      1. Create and name the Fusion Set (security template) that will contain the Dex Relocation feature as shown below:
        fusion set that contains Dex Relocation .

        Figure 1: Fusion Set that will contain the Dex Relocation 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 2.2-2.2.2 of this article to add the Dex Relocation feature to your Fusion Set via the Appdome Console.

      3. When you select the Dex Relocation you'll notice that the Fusion Set you created in step 2.1 now bears the icon of the protection category that contains Dex Relocation.

        Fusion Set applied Dex Relocation

        Figure 2: Fusion Set that displays the newly added Dex Relocation protection
        Note: Annotating the Fusion Set to identify the protection(s) selected is optional only (not mandatory).

      4. 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): fusion Set Detail Summary image

        Figure 3: Fusion Set Detail Summary

      5. Follow the instructions below to use the Fusion Set ID inside any standard mobile DevOps or CI/CD toolkit like Bitrise, Jenkins, Travis, Team City, Circle CI or other system:
        1. Refer to the Appdome API Reference Guide for API building instructions.
        2. Look for sample APIs in Appdome’s GitHub Repository.
    1. Add the Dex Relocation feature to your security template.

      1. Navigate to Build > Security tab > TOTALCode™ Obfuscation section in the Appdome Console.
      2. Toggle On > Dex Relocation.
        Dex Relocation option

        Figure 4: Selecting Use Dex Relocation

      3. Extra Configuration with Dex Relocation:
        1. Favor Loading Time

          Automatically detect and optimize obfuscation of publicly available components in order to preserve application loading time.

        2. Exclude Specific Classes

          List class or package prefixes to exclude and not obfuscate.

        3. No Mapping File/Script

          Changes the flow logic, but does not rename functions. No mapping file or script needed.

    2. Initiate the build command either by clicking Build My App at the bottom of the Build Workflow (shown in Figure 4) or via your CI/CD as described in Section 2.1.4.
    Congratulations!  The Dex Relocation protection is now added to the mobile app
  3. Certify the Dex Relocation feature in Android Apps

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

    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 Dex Relocation has been added to each Android app. Certified Secure provides instant and in-line DevSecOps compliance certification that Dex Relocation and other mobile app security features are in each build of the mobile app.

Using Threat-Events™ for Dex Relocation Intelligence and Control in Android Apps

Appdome Threat-Events™ provides consumable in-app mobile app attack intelligence and defense control when Dex Relocation is detected. To consume and use Threat-Events™ for Dex Relocation in Android Apps, use registerReceiver in the Application OnCreate, and the code samples for Threat-Events™ for Dex Relocation shown below.

The specifications and options for Threat-Events™ for Dex Relocation are:

Threat-Event™ Elements Use Dex Relocation Method Detail
Appdome Feature Name Dex Relocation
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 x
Visible in ThreatScope™ x
Developer Parameters for Using Dex Relocation Threat-Event™
Threat-Event NAME
Threat-Event DATA reasonData
Threat-Event CODE reasonCode
Threat-Event REF
Threat-Event SCORE
currentThreatEventScore Current Threat-Event score
threatEventsScore Total Threat-events score
Threat-Event Context Keys
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
threatCode The last six characters of the threat code specify the OS, allowing the Threat Resolution Center to address the attack on the affected device.

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 Dex Relocation is detected.


The following is a code sample for native Android apps, which uses all values in the specification above for Dex Relocation:


Important! Replace all placeholder instances of <Context Key> with the specific name of your threat event context key across all language examples. This is crucial to ensure your code functions correctly with the intended event data. For example, The <Context Key> could be the message, externalID, OS Version, reason code, etc.



Using Appdome, there are no development or coding prerequisites to build secured Android Apps by using Dex Relocation. 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 Dex Relocation

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:

Related Articles:

 

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.

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