Add FAC getLimitedUseToken to internal interop interface (#4979)

* Add FAC getLimitedUseToken to internal interop interface

* Typo

* Changelog

* Formatting

* PR feedback

Author: sam-gc

appcheck/firebase-appcheck-interop/src/main/java/com/google/firebase/appcheck/interop/InteropAppCheckTokenProvider.java

@@ -29,6 +29,15 @@ public interface InteropAppCheckTokenProvider {
   @NonNull
   Task<AppCheckTokenResult> getToken(boolean forceRefresh);
 
+  /**
+   * Requests an {@link AppCheckTokenResult} from the installed {@code AppCheckFactory}. This will
+   * always return a successful task, with an {@link AppCheckTokenResult} that contains either a
+   * valid token, or a dummy token and an error string. The token returned from this method will be
+   * a one-time use token.
+   */
+  @NonNull
+  Task<AppCheckTokenResult> getLimitedUseToken();
+
   /**
    * Registers a listener to changes in the token state. There can be more than one listener
    * registered at the same time for one or more FirebaseAppAuth instances. The listeners call back

appcheck/firebase-appcheck/CHANGELOG.md

@@ -1,5 +1,5 @@
 # Unreleased
-
+* [changed] Internal updates to allow Firebase SDKs to obtain limited-use tokens.
 
 # 17.0.0
 * [feature] Added [`getLimitedUseAppCheckToken()`](/docs/reference/android/com/google/firebase/appcheck/FirebaseAppCheck#getLimitedUseAppCheckToken())

appcheck/firebase-appcheck/firebase-appcheck.gradle

@@ -46,7 +46,7 @@ dependencies {
     implementation 'com.google.firebase:firebase-annotations:16.2.0'
     implementation 'com.google.firebase:firebase-common:20.3.1'
     implementation 'com.google.firebase:firebase-components:17.1.0'
-    implementation 'com.google.firebase:firebase-appcheck-interop:17.0.0'
+    implementation project(':appcheck:firebase-appcheck-interop')
     implementation 'com.google.android.gms:play-services-base:18.0.1'
     implementation 'com.google.android.gms:play-services-tasks:18.0.1'
 

appcheck/firebase-appcheck/src/main/java/com/google/firebase/appcheck/internal/DefaultFirebaseAppCheck.java

@@ -213,6 +213,28 @@ public Task<AppCheckTokenResult> getToken(boolean forceRefresh) {
         });
   }
 
+  @NonNull
+  @Override
+  public Task<AppCheckTokenResult> getLimitedUseToken() {
+    return getLimitedUseAppCheckToken()
+        .continueWithTask(
+            liteExecutor,
+            appCheckTokenTask -> {
+              if (appCheckTokenTask.isSuccessful()) {
+                return Tasks.forResult(
+                    DefaultAppCheckTokenResult.constructFromAppCheckToken(
+                        appCheckTokenTask.getResult()));
+              }
+              // If the token exchange failed, return a dummy token for integrators to attach
+              // in their headers.
+              return Tasks.forResult(
+                  DefaultAppCheckTokenResult.constructFromError(
+                      new FirebaseException(
+                          appCheckTokenTask.getException().getMessage(),
+                          appCheckTokenTask.getException())));
+            });
+  }
+
   @NonNull
   @Override
   public Task<AppCheckToken> getAppCheckToken(boolean forceRefresh) {

appcheck/firebase-appcheck/src/test/java/com/google/firebase/appcheck/internal/DefaultFirebaseAppCheckTest.java

@@ -235,6 +235,15 @@ public void testGetLimitedUseAppCheckToken_noFactoryInstalled_taskFails() throws
     assertThat(tokenTask.isSuccessful()).isFalse();
   }
 
+  @Test
+  public void testGetLimitedUseToken_noFactoryInstalled_returnResultWithError() throws Exception {
+    Task<AppCheckTokenResult> tokenTask = defaultFirebaseAppCheck.getLimitedUseToken();
+    assertThat(tokenTask.isComplete()).isTrue();
+    assertThat(tokenTask.isSuccessful()).isTrue();
+    assertThat(tokenTask.getResult().getToken()).isNotNull();
+    assertThat(tokenTask.getResult().getError()).isNotNull();
+  }
+
   @Test
   public void testGetToken_factoryInstalled_proxiesToAppCheckFactory() {
     defaultFirebaseAppCheck.installAppCheckProviderFactory(mockAppCheckProviderFactory);
@@ -422,4 +431,23 @@ public void testGetLimitedUseAppCheckToken_existingToken_requestsNewToken() {
 
     verify(mockAppCheckProvider).getToken();
   }
+
+  @Test
+  public void testGetLimitedUseToken_noExistingToken_requestsNewToken() {
+    defaultFirebaseAppCheck.installAppCheckProviderFactory(mockAppCheckProviderFactory);
+
+    defaultFirebaseAppCheck.getLimitedUseToken();
+
+    verify(mockAppCheckProvider).getToken();
+  }
+
+  @Test
+  public void testGetLimitedUseToken_existingToken_requestsNewToken() {
+    defaultFirebaseAppCheck.setCachedToken(validDefaultAppCheckToken);
+    defaultFirebaseAppCheck.installAppCheckProviderFactory(mockAppCheckProviderFactory);
+
+    defaultFirebaseAppCheck.getLimitedUseToken();
+
+    verify(mockAppCheckProvider).getToken();
+  }
 }

firebase-functions/src/androidTest/java/com/google/firebase/functions/TestInteropAppCheckTokenProvider.java

@@ -66,6 +66,12 @@ public Task<AppCheckTokenResult> getToken(boolean forceRefresh) {
     return Tasks.forResult(testToken);
   }
 
+  @NonNull
+  @Override
+  public Task<AppCheckTokenResult> getLimitedUseToken() {
+    return Tasks.forResult(testToken);
+  }
+
   @Override
   public void addAppCheckTokenListener(@NonNull AppCheckTokenListener listener) {}