Implement Firebase App Check to protect APIs from unauthorized clients

When you call an API directly from a mobile or web app (for example, the APIs that allow access to generative AI models), the API is vulnerable to abuse by unauthorized clients. To help protect these APIs, you can use Firebase App Check to verify that all incoming API calls are from your actual app.

Firebase AI Logic provides a proxy gateway that lets you integrate with Firebase App Check and protect the generative AI model APIs called by your mobile and web apps. Using App Check with the Firebase AI Logic SDKs supports all our configurations:

• Protects both "Gemini API" providers: Gemini Developer API and Vertex AI Gemini API.

• Protects all supported models, both Gemini models and Imagen models.

We strongly recommend implementing Firebase App Check into your app as early as possible, even during development, so that every version of your app is protected from API abuse.

High-level summary of how App Check works

With App Check, devices running your app use an app or device attestation provider that verifies one or both of the following:

• Requests originate from your authentic app
• Requests originate from an authentic, untampered device

This attestation is attached to every request your app makes using a Firebase AI Logic SDK. When you enable App Check enforcement, requests from clients without a valid attestation will be rejected, as will any request originating from an app or platform you haven't authorized.

We recommend that when you set up App Check, make sure to prepare for upcoming enhanced protection (known as replay protection).

You can find detailed information about App Check in its documentation, including its quotas and limits.

Available providers and implementation instructions

The App Check documentation provides descriptions of attestation providers as well as implementation instructions.

1. Choose a default provider, and follow the implementation instructions at the following links:

   • Apple platforms: DeviceCheck or App Attest
   • Android: Play Integrity
   • Web: reCAPTCHA Enterprise
   • Flutter: Supports all the default providers above
     Also, make sure to follow special instantiation requirements for Flutter and App Check.
   • Unity: Supports all the default providers above

   Note that if none of the default providers are sufficient for your needs, then you can implement a custom provider that uses either a third-party attestation provider or your own attestation techniques.

2. (Recommended) Prepare for upcoming enhanced protection from App Check (known as replay protection).

3. (Required) Before you release your app to real users, enable enforcement of App Check.

Special instantiation required for Flutter

Click your Gemini API provider to view provider-specific content and code on this page. Gemini Developer API Vertex AI Gemini API

When using App Check with Firebase AI Logic in Flutter apps, you need to explicitly pass in App Check during instantiation, like so:

// ...

final ai = await FirebaseAI.googleAI(
  appCheck: FirebaseAppCheck.instance, // for Flutter, pass in App Check explicitly
);

// ...

Prepare for upcoming enhanced protection

Using limited-use tokens is currently only available for Apple platforms (v12.2.0+), Android (v17.2.0+, BoM v34.2.0+), and Web (v12.3.0+) . Support for other platforms will be released over the next several weeks.

By default, App Check uses session tokens which have a configurable time to live (TTL) between 30 minutes and 7 days. These session tokens are cached by the App Check SDK and sent along with requests from your app.

In the future, App Check will add the option to enable replay protection for Firebase AI Logic (similar to the support that App Check already offers for some other resources). When replay protection is enabled, it enhances protection in the following ways:

• App Check will only allow requests if they're accompanied by a special kind of token called a limited-use token.

• After the limited-use token is verified, the token is consumed so that it can be used only once, preventing replay attacks.

To prepare for replay protection, we recommend that you enable the usage of limited-use tokens as part of setting up App Check. That way, when replay protection becomes available, then you can enable it sooner because more of your users will be on versions of your app that send limited-use tokens.

Note the following if you enable usage of limited-use tokens in your app now (while replay protection is unavailable):

• App Check does not block the usage of valid session tokens.

• Just like session tokens, limited-use tokens are cached by the App Check SDK and sent along with requests. These limited-use tokens provide a small amount of additional protection than the default session tokens because limited-use tokens have a shorter TTL (only 5 minutes and not adjustable) compared to session tokens.

• Even though limited-use tokens are valid for 5 minutes, the SDK will still generate a new token for each request. This process can add some latency to your request.

However, when replay protection is available for Firebase AI Logic in the future (and you enable it), the use of session tokens and the reuse of limited-use tokens won't be possible. Note that the additional latency for generating a new token for each request will still happen.

Enable usage of limited-use tokens

Click your Gemini API provider to view provider-specific content and code on this page. Gemini Developer API Vertex AI Gemini API

Note: Consider setting up limited-use tokens to be a Firebase Remote Config parameter so that you can control its setting remotely rather than having it hard-coded in your app. Learn more about using Remote Config.

Here's how to enable usage of limited-use tokens:

1. Implement App Check, and make sure that you've enabled App Check enforcement for your app.

2. In your app during instantiation, enable the usage of limited-use tokens by setting the useLimitedUseAppCheckTokens parameter to true:

   Swift

   
   // ...
   
   // During instantiation, enable usage of limited-use tokens
   let ai = FirebaseAI.firebaseAI(
     backend: .googleAI(),
     useLimitedUseAppCheckTokens: true
   )
   
   // ...
   
   

   Kotlin

   
   // ...
   
   // During instantiation, enable usage of limited-use tokens
   val ai = Firebase.ai(
     backend = GenerativeBackend.googleAI(),
     useLimitedUseAppCheckTokens = true
   )
   
   // ...
   
   

   Java

   
   // ...
   
   // During instantiation, enable usage of limited-use tokens
   FirebaseAI ai = FirebaseAI.getInstance(
     /* backend: */ GenerativeBackend.googleAI(),
     /* useLimitedUseAppCheckTokens: */ true
   );
   
   // ...
   
   

   Web

   
   // ...
   
   // During instantiation, enable usage of limited-use tokens
   const ai = getAI(firebaseApp, {
     backend: new GoogleAIBackend(),
     useLimitedUseAppCheckTokens: true
   });
   
   // ...
   
   

   Dart

   Using limited-use tokens with Flutter apps will be supported in the upcoming release. Check back soon!

   Unity

   Using limited-use tokens with Unity games will be supported in a future release. Check back soon!

Understand how Firebase AI Logic integrates with App Check

To use the Firebase AI Logic SDKs, the Firebase AI Logic API (firebasevertexai.googleapis.com) must be enabled in your Firebase project. This is because requests made by the Firebase AI Logic SDKs are first sent to the Firebase AI Logic server, which acts as a proxy gateway where Firebase App Check verification takes place before the request is allowed to proceed to your chosen "Gemini API" provider's backend and the APIs to access the Gemini and Imagen models.