How to Enforce Secure Certificate Pinning in Android & iOS Apps

Last updated September 24, 2024 by Appdome

This Knowledge Base article describes how to use Appdome’s AI/ML in your CI/CD pipeline to continuously deliver plugins that Enforce Secure Certificate Pinning in Mobile apps.

What is Secure Certificate Pinning?

Certificate Pinning is the process of embedding a mobile app with a valid SSL certificate for trusted servers. An application that pins a certificate or public key no longer depends on external elements such as DNS or intermediate/public certificate authorities, when making security decisions relating to a peer server’s identity.

The most common form of certificate pinning is embedding the server certificates inside the mobile app, to ensure that the server certificate is always trusted. This will prevent hackers from presenting modified fraudulent certificates to the mobile app in an attempt to redirect the mobile user to a malicious site. A host or service’s certificate or public key can be added to an application at development time, or it can be added upon first encountering the certificate or public key. The former—adding at development time—is preferred since preloading the certificate or public key out of band means the attacker cannot taint the pin by intercepting the session before the TLS handshake completes.

 

How Appdome Implements Secure Certificate Pinning?

Certificate pinning is the practice of embedding the certificate(s) of the known trusted server(s) inside the mobile application (obfuscated and encrypted for protection). Each time a TLS session is initiated by either end, Appdome inspects the pinned certificate stored inside the app to make sure it matches that of the trusted server. In the event of a mismatch, the session is not allowed.

When setting up Secure Certificate Pinning, here are the certificates expected for each evaluation scheme:

  • Strict Evaluation scheme: server certificate
  • Chain Evaluation scheme: Root CA cert + the intermediate certificate or/and the server certificate
  • Root Evaluation scheme: root CA certificate
  • Public Key Evaluation scheme: server certificate

Note: Appdome validates uploaded certificates before the build step. During this validation process, Appdome detects and alerts on known errors in the certificates, including expired certificates, invalid certificate formats, missing certificates in the chain, non-valid root certificates, and invalid files and file types. Appdome supports certificate file types such as .cer,.crt,.pem,.der, or.zip. It is important to remember that a single certificate file cannot contain multiple certificates. For entries requiring more than one certificate, each certificate must be provided as a single file, and then all files can be zipped together.

In addition, by defining a service domain, mobile app developers can use various methods to verify and pin certificates for specific domains. Each service domain can be configured by using * as a wildcard value and can be applied to multiple domains.


Important:
Please be aware that Security Certificate Pinning and the Anti-Bot Pin to Host are mutually exclusive. Implementing them together will result in a conflict within the engine. Ensure that you use only one method at a time to avoid potential issues.

 

Prerequisites for Using Appdome's Secure Certificate Pinning Plugins:

To use Appdome’s mobile app security build system to Enforce Secure Certificate Pinning , you’ll need:

How to Implement Enforce Secure Certificate Pinning in Mobile Apps Using Appdome

On Appdome, follow these 3 simple steps to create self-defending Mobile Apps that Enforce Secure Certificate Pinning 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. Mobile App Formats: .ipa for iOS, or .apk or .aab for Android
    3. Secure Certificate Pinning is compatible with: Obj-C, Java, JS, C#, C++, Swift, Kotlin, Flutter, React Native, Unity, Xamarin, and more.
  2. Select the defense: Secure Certificate Pinning.

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

        Figure 1: Fusion Set that will contain the Secure Certificate Pinning 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 Secure Certificate Pinning feature to your Fusion Set via the Appdome Console.

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

        Fusion Set applied Secure Certificate Pinning

        Figure 2: Fusion Set that displays the newly added Secure Certificate Pinning 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 Secure Certificate Pinning feature to your security template.

      1. Navigate to Build > Security tab > Secure Communication section in the Appdome Console.
      2. Toggle On > Secure Certificate Pinning.
        Secure Certificate Pinning option

        Figure 4: Selecting Enforce Secure Certificate Pinning

        Note: The Appdome Platform displays the Mobile Operation Systems supported by each defense in real-time. For more details, see our OS Support Policy KB.

      3. Configure the User Experience Options for Secure Certificate Pinning:
        With Threat-Events™ OFF, Appdome provides several user experience options for mobile brands and developers.
        1. App Compromise Notification: Customize the pop-up or toast Appdome uses to notify the user when a threat is present while using the protected mobile app.
        2. Short message Option. This is available for mobile devices that allow a banner notification for security events.
        3. Localized Message Option. Allows Appdome users to support global languages in security notifications.

          Localized Message

          Figure 5: Default User Experience Options for Appdome’s Secure Certificate Pinning

        4. Secure Certificate Pinning Threat Code™. Appdome uses AI/ML to generate a unique code each time Secure Certificate Pinning is triggered by an active threat on the mobile device. Use the code in Appdome Threat Resolution Center™ to help end users identify, find and resolve active threats on the personal mobile devices.
      4. Extra Configuration with Secure Certificate Pinning:
        1. Enforce Certificate Roles

          Enforce network connections to verify 'basicConstraints' extension in the certificate chain.

        2. Enforce Strong RSA Signature

          Enforce server certificate signatures to use a Rivest-Shamir-Adleman (RSA) key with a length of at least 2048 bits.

        3. Enforce Strong ECC Signature

          Enforce server certificate signatures to use Elliptic-Curve Cryptography (ECC) key with a size of at least 256 bits.

        4. Enforce SHA256 Digest

          Enforce server certificate signatures to use at least a SHA256 certificate hashing algorithm.

    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 Secure Certificate Pinning protection is now added to the mobile app
  3. Certify the Secure Certificate Pinning feature in Mobile Apps

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

    Figure 6: 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 Secure Certificate Pinning has been added to each Mobile app. Certified Secure provides instant and in-line DevSecOps compliance certification that Secure Certificate Pinning and other mobile app security features are in each build of the mobile app.

Using Threat-Events™ for Secure Certificate Pinning Intelligence and Control in Mobile Apps

Appdome Threat-Events™ provides consumable in-app mobile app attack intelligence and defense control when Secure Certificate Pinning is detected. To consume and use Threat-Events™ for Secure Certificate Pinning in Mobile Apps, use AddObserverForName in Notification Center, and the code samples for Threat-Events™ for Secure Certificate Pinning shown below.

The specifications and options for Threat-Events™ for Secure Certificate Pinning are:

Threat-Event™ Elements Enforce Secure Certificate Pinning Method Detail
Appdome Feature Name Secure Certificate Pinning
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 Enforcing Secure Certificate Pinning 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), Mobile developers can get detailed attack intelligence and granular defense control in Mobile applications and create amazing user experiences for all mobile end users when Secure Certificate Pinning is detected.


The following is a code sample for native Mobile apps, which uses all values in the specification above for Secure Certificate Pinning:


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 Mobile Apps by using Secure Certificate Pinning. 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 Secure Certificate Pinning

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 to Enforce Strong RSA Signature in Android & iOS Apps

How to Enforce Strong ECC Signature in iOS Apps

How to Enforce SHA-256 Digest in Android & iOS Apps

 

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.

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