iOS Binding Obfuscation, Anti-Reversing in iOS Apps

Last updated August 11, 2022 by Appdome

Learn to Add Binding Obfuscation in iOS apps, in mobile CI/CD with a Data-Driven DevSecOps™ build system.

What is Binding Obfuscation?

iOS apps consist of binaries in Mach-O format. This format contains “Binding Information” which is required to perform dynamic resolution of system symbols. “Binding Information” consists of a list of instructions the OS will follow when loading the app into memory so that the app has all it needs to function properly. One type of instruction will instruct OS to provide the app with the address of a function that is implemented in a system library, a.k.a dynamic resolution system symbols. In order to properly obfuscate binding information, two guidelines need to be followed (a) render the binding instructions incomprehensible to an attacker so they can’t be converted back to the original symbol while (b) ensuring that when the app is launched all the required functions are resolved properly and in the correct timing.

Why should you obfuscate iOS Bindings ?

Attackers will use Binding information during static analysis and reverse engineering to gain a deep understanding of the inner workings of an iOS app. Since the binding instructions list includes the system function names the app is planning to call, combining all the system function names into a list will give an insight into the app’s business logic and potential vectors to attack the app. Furthermore, attackers can perform the opposite conversion, following the binding instruction to convert the system function names to the location the OS is instructed to store the resolved address, to find all calls to the system in question. Obfuscating iOS Bindings in the application binary will prevent the attacker from performing these conversions and therefore make reverse engineering very limited.

Adding Binding Obfuscation on iOS apps by Using Appdome

On Appdome, follow these 3 simple steps to create self-defending iOS Apps that Add Binding Obfuscation 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. iOS Formats: .ipa
  2. Build the Protection: Binding Obfuscation.

    1. Building Binding Obfuscation by using Appdome’s DEV-API:

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

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

      3. Follow the steps in Sections 2.2.1-2.2.2 of this article, Building the Binding Obfuscation feature via Appdome Console, to add the Binding Obfuscation feature to this Fusion Set.

      4. 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): fusion Set Detail Summary image

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

      5. 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 Binding Obfuscation feature via Appdome Console

      To build the Binding Obfuscation protection by using Appdome Console, follow the instructions below.

      1. Where: Inside the Appdome Console, go to Build > Security Tab > TOTALCode™ Obfuscation section
      2. How: Toggle (turn ON) Binding Obfuscation, as shown below. Binding Obfuscation option

        Figure 3: Add Binding Obfuscation option

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

        Fusion Set applied Binding Obfuscation

        Figure 4: Fusion Set that displays the newly added Binding Obfuscation protection

      4. Click Build My App at the bottom of the Build Workflow (shown in Figure 3).
    Congratulations!  The Binding Obfuscation protection is now added to the mobile app
  3. Certify the Binding Obfuscation feature in iOS Apps.

    After building Binding Obfuscation, Appdome generates a Certified Secure™ certificate to guarantee that the Binding Obfuscation protection has been added and is protecting the app. To verify that the Binding Obfuscation protection has been added to the mobile app, locate the protection in the Certified Secure™ certificate as shown below: Binding Obfuscation 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 Binding Obfuscation has been added to each iOS app. Certified Secure provides instant and in-line DevSecOps compliance certification that Binding Obfuscation and other mobile app security features are in each build of the mobile app

Prerequisites to Using Binding Obfuscation:

To use Appdome’s mobile app security build system to Add Binding Obfuscation , you’ll need:

Using Appdome, there are no development or coding prerequisites to build secured Apps by using Binding Obfuscation. 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 Binding Obfuscation

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:

All apps protected by Appdome are fully compatible with any public app store, including Apple App Store, Google Play, Huawei App Gallery and more.

Protections Similar to Binding Obfuscation

Here are a few related resources:

https://blog.efiens.com/post/luibo/osx/linker-info/

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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