How to Obfuscate Dynamically Loaded Symbols in iOS Apps

Learn to Obfuscate Dynamically Loaded Symbols in iOS apps, in mobile CI/CD with a Data-Driven DevSecOps™ build system.

What are Dynamically Loaded Symbols?

Dynamically Loaded Symbols, commonly known as Lazy symbols, are symbols found in iOS binaries (Mach-O format). These symbols are imported from other binaries or dynamically linked libraries, be they from the system or third-party sources, yet they aren’t implemented directly within the binary. Every binary might contain lazy symbols from various libraries. What sets lazy symbols apart is their addressing; Their final address is determined only when the app first tries to use them upon loading. In contrast, all other imported symbols have their addresses resolved during the app’s initial launch, rather than at first use. The responsibility for resolving these imported symbols and identifying their addresses falls to the dyld, the dynamic linker component of iOS.

Why It's Necessary to Obfuscate Dynamically Loaded Symbols?

Obfuscating Dynamically Loaded Symbols is vital, especially in the context of defending against static analysis by reversers. Through static analysis, reversers can meticulously extract detailed information about the symbols an app imports. A particular area of concern is the unveiling of cryptographic functions, such as MD5 or SHA256, that the app might be leveraging from system libraries or third-party sources. By discerning which cryptographic methods are in play, reversers not only gain hints about decrypting secured data but also establish a precise anchor pinpointing where and when these functions come into action. Armed with this insight, they can potentially manipulate the app in real-time, disabling or even altering the intended purpose of these imported functions. Given these significant threats, obfuscation stands as not just a protective measure but an imperative shield, ensuring that the app remains inscrutable, safeguarding its intellectual property, data, and overall functionality from potentially disastrous tampering.

Prerequisites for Using Obfuscate Dynamically Loaded Symbols:

To use Appdome’s mobile app security build system to Obfuscate Dynamically Loaded Symbols , you’ll need:

• Appdome account (create a free Appdome account here)
• A license for Obfuscate Dynamically Loaded Symbols
• Mobile App (.ipa for iOS)
• Signing Credentials (see Signing Secure Android apps and Signing Secure iOS apps)

Obfuscate Dynamically Loaded Symbols on iOS apps using Appdome

On Appdome, follow these simple steps to create self-defending iOS Apps that Obfuscate Dynamically Loaded Symbols 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
   4. Obfuscate Dynamically Loaded Symbols Compatible With: Obj-C, C+, Java, Swift, Flutter, React Native, Unity, Xamarin, Cordova and more

2. Build the feature: Obfuscate Dynamically Loaded Symbols.

   1. Building Obfuscate Dynamically Loaded Symbols by using Appdome’s DEV-API:

      1. Create and name the Fusion Set (security template) that will contain the Obfuscate Dynamically Loaded Symbols feature as shown below:
      

      Figure 1: Fusion Set that will contain the Obfuscate Dynamically Loaded Symbols 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 Obfuscate Dynamically Loaded Symbols feature via Appdome Console, to add the Obfuscate Dynamically Loaded Symbols 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 Obfuscate Dynamically Loaded Symbols feature via Appdome Console

      To build the Obfuscate Dynamically Loaded Symbols protection by using Appdome Console, follow the instructions below.

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

         Like all other options in ONEShield™, Obfuscate Dynamically Loaded Symbols is turned on by default, as shown below:

         Figure 3: Obfuscate Dynamically Loaded Symbols 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: Check whether Binding Obfuscation is toggled On (enabled), otherwise enable it . You can see that the feature Obfuscate Dynamically Loaded Symbols is enabled by default, as shown below.

         Figure 3: Obfuscate Dynamically Loaded Symbols option

      3. When you enable 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 Obfuscate Dynamically Loaded Symbols

         

         Figure 4: Fusion Set that displays the newly added Obfuscate Dynamically Loaded Symbols protection

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

   Congratulations!  The Obfuscate Dynamically Loaded Symbols protection is now added to the mobile app

3. Certify the Obfuscate Dynamically Loaded Symbols feature in iOS Apps.

   After building Obfuscate Dynamically Loaded Symbols, Appdome generates a Certified Secure™ certificate to guarantee that the Obfuscate Dynamically Loaded Symbols protection has been added and is protecting the app. To verify that the Obfuscate Dynamically Loaded Symbols 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 Obfuscate Dynamically Loaded Symbols has been added to each iOS app. Certified Secure provides instant and in-line DevSecOps compliance certification that Obfuscate Dynamically Loaded Symbols and other mobile app security features are in each build of the mobile app