Try to address prewarming issue by catching keychain errors instead of using isProtectedDataAvailable (#9898)

* Another attempt at fixing prewarming issues.

* Fix style.

* Check the correct error code.

* Add changelog and fix style.

* Prevent retain cycle?

* Prevent retain cycle?

* Address review comment.

* Move observer removal into block.

* Update version number in changelog.

Author: rosalyntan

FirebaseAuth/CHANGELOG.md

@@ -1,3 +1,6 @@
+# 9.2.0
+- [fixed] Catch keychain errors instead of using the `isProtectedDataAvailable` API for handling prewarming issue. (#9869)
+
 # 9.0.0
 - [fixed] **Breaking change:** Fixed an ObjC-to-Swift API conversion error where `getStoredUser(forAccessGroup:)` returned a non-optional type. This change is breaking for Swift users only (#8599).
 - [fixed] Fixed an iOS 15 keychain access issue related to prewarming. (#8695)

FirebaseAuth/Sources/Auth/FIRAuth.m

@@ -496,46 +496,12 @@ - (nullable instancetype)initWithAPIKey:(NSString *)APIKey
     [GULSceneDelegateSwizzler proxyOriginalSceneDelegate];
 #endif  // TARGET_OS_IOS
 
-#if TARGET_OS_IOS || TARGET_OS_TV || TARGET_OS_MACCATALYST
-    static Class applicationClass = nil;
-    // iOS App extensions should not call [UIApplication sharedApplication], even if UIApplication
-    // responds to it.
-    if (![GULAppEnvironmentUtil isAppExtension]) {
-      Class cls = NSClassFromString(@"UIApplication");
-      if (cls && [cls respondsToSelector:@selector(sharedApplication)]) {
-        applicationClass = cls;
-      }
-    }
-    UIApplication *application = [applicationClass sharedApplication];
-    if ([application respondsToSelector:@selector(isProtectedDataAvailable)]) {
-      if ([application isProtectedDataAvailable]) {
-        [self protectedDataInitialization];
-      } else {
-        // Add listener for UIApplicationProtectedDataDidBecomeAvailable.
-        self->_protectedDataDidBecomeAvailableObserver = [[NSNotificationCenter defaultCenter]
-            addObserverForName:UIApplicationProtectedDataDidBecomeAvailable
-                        object:nil
-                         queue:nil
-                    usingBlock:^(NSNotification *notification) {
-                      [self protectedDataInitialization];
-                    }];
-      }
-    } else {
-      [self protectedDataInitialization];
-    }
-#else
     [self protectedDataInitialization];
-#endif  // TARGET_OS_IOS || TARGET_OS_TV || TARGET_OS_MACCATALYST
   }
   return self;
 }
 
 - (void)protectedDataInitialization {
-#if TARGET_OS_IOS || TARGET_OS_TV || TARGET_OS_MACCATALYST
-  [[NSNotificationCenter defaultCenter] removeObserver:_protectedDataDidBecomeAvailableObserver
-                                                  name:UIApplicationProtectedDataDidBecomeAvailable
-                                                object:nil];
-#endif  // TARGET_OS_IOS || TARGET_OS_TV || TARGET_OS_MACCATALYST
   // Continue with the rest of initialization in the work thread.
   __weak FIRAuth *weakSelf = self;
   dispatch_async(FIRAuthGlobalWorkQueue(), ^{
@@ -564,17 +530,41 @@ - (void)protectedDataInitialization {
           [strongSelf updateCurrentUser:user byForce:NO savingToDisk:NO error:&error];
           self->_lastNotifiedUserToken = user.rawAccessToken;
         } else {
+#if TARGET_OS_IOS || TARGET_OS_TV || TARGET_OS_MACCATALYST
+          if (error.code == FIRAuthErrorCodeKeychainError) {
+            // If there's a keychain error, assume it is due to the keychain being accessed
+            // before the device is unlocked as a result of prewarming, and listen for the
+            // UIApplicationProtectedDataDidBecomeAvailable notification.
+            [strongSelf addProtectedDataDidBecomeAvailableObserver];
+          }
+#endif  // TARGET_OS_IOS || TARGET_OS_TV || TARGET_OS_MACCATALYST
           FIRLogError(kFIRLoggerAuth, @"I-AUT000001",
                       @"Error loading saved user when starting up: %@", error);
         }
       } else {
         [strongSelf internalUseUserAccessGroup:storedUserAccessGroup error:&error];
         if (error) {
+#if TARGET_OS_IOS || TARGET_OS_TV || TARGET_OS_MACCATALYST
+          if (error.code == FIRAuthErrorCodeKeychainError) {
+            // If there's a keychain error, assume it is due to the keychain being accessed
+            // before the device is unlocked as a result of prewarming, and listen for the
+            // UIApplicationProtectedDataDidBecomeAvailable notification.
+            [strongSelf addProtectedDataDidBecomeAvailableObserver];
+          }
+#endif  // TARGET_OS_IOS || TARGET_OS_TV || TARGET_OS_MACCATALYST
           FIRLogError(kFIRLoggerAuth, @"I-AUT000001",
                       @"Error loading saved user when starting up: %@", error);
         }
       }
     } else {
+#if TARGET_OS_IOS || TARGET_OS_TV || TARGET_OS_MACCATALYST
+      if (error.code == FIRAuthErrorCodeKeychainError) {
+        // If there's a keychain error, assume it is due to the keychain being accessed
+        // before the device is unlocked as a result of prewarming, and listen for the
+        // UIApplicationProtectedDataDidBecomeAvailable notification.
+        [strongSelf addProtectedDataDidBecomeAvailableObserver];
+      }
+#endif  // TARGET_OS_IOS || TARGET_OS_TV || TARGET_OS_MACCATALYST
       FIRLogError(kFIRLoggerAuth, @"I-AUT000001", @"Error loading saved user when starting up: %@",
                   error);
     }
@@ -613,6 +603,24 @@ - (void)protectedDataInitialization {
   });
 }
 
+#if TARGET_OS_IOS || TARGET_OS_TV || TARGET_OS_MACCATALYST
+- (void)addProtectedDataDidBecomeAvailableObserver {
+  __weak FIRAuth *weakSelf = self;
+  self->_protectedDataDidBecomeAvailableObserver = [[NSNotificationCenter defaultCenter]
+      addObserverForName:UIApplicationProtectedDataDidBecomeAvailable
+                  object:nil
+                   queue:nil
+              usingBlock:^(NSNotification *notification) {
+                FIRAuth *strongSelf = weakSelf;
+                [[NSNotificationCenter defaultCenter]
+                    removeObserver:strongSelf->_protectedDataDidBecomeAvailableObserver
+                              name:UIApplicationProtectedDataDidBecomeAvailable
+                            object:nil];
+                [strongSelf protectedDataInitialization];
+              }];
+}
+#endif  // TARGET_OS_IOS || TARGET_OS_TV || TARGET_OS_MACCATALYST
+
 - (void)dealloc {
   @synchronized(self) {
     NSNotificationCenter *defaultCenter = [NSNotificationCenter defaultCenter];