App extension check (#1358)

3 files changed, 39 insertions, 4 deletions

diff --git a/Firebase/Auth/Source/FIRAuth.m b/Firebase/Auth/Source/FIRAuth.m
index c83a19a..81008ca 100644
--- a/Firebase/Auth/Source/FIRAuth.m
+++ b/Firebase/Auth/Source/FIRAuth.m
@@ -19,6 +19,7 @@
 #import "FIRAuth_Internal.h"
 
 #import <FirebaseCore/FIRAppAssociationRegistration.h>
+#import <FirebaseCore/FIRAppEnvironmentUtil.h>
 #import <FirebaseCore/FIRAppInternal.h>
 #import <FirebaseCore/FIRLogger.h>
 #import <FirebaseCore/FIROptions.h>
@@ -438,7 +439,18 @@ static NSMutableDictionary *gKeychainServiceNameForAppName;
     _settings = [[FIRAuthSettings alloc] init];
     _firebaseAppName = [appName copy];
     #if TARGET_OS_IOS
-    UIApplication *application = [UIApplication sharedApplication];
+
+    static Class applicationClass = nil;
+    // iOS App extensions should not call [UIApplication sharedApplication], even if UIApplication
+    // responds to it.
+    if (![FIRAppEnvironmentUtil isAppExtension]) {
+      Class cls = NSClassFromString(@"UIApplication");
+      if (cls && [cls respondsToSelector:NSSelectorFromString(@"sharedApplication")]) {
+        applicationClass = cls;
+      }
+    }
+    UIApplication *application = [applicationClass sharedApplication];
+
     // Initialize the shared FIRAuthAppDelegateProxy instance in the main thread if not already.
     [FIRAuthAppDelegateProxy sharedInstance];
     #endif
diff --git a/Firebase/Auth/Source/FIRAuthAppDelegateProxy.m b/Firebase/Auth/Source/FIRAuthAppDelegateProxy.m
index f13e94f..3289b4e 100644
--- a/Firebase/Auth/Source/FIRAuthAppDelegateProxy.m
+++ b/Firebase/Auth/Source/FIRAuthAppDelegateProxy.m
@@ -16,6 +16,8 @@
 
 #import "FIRAuthAppDelegateProxy.h"
 
+#import <FirebaseCore/FIRAppEnvironmentUtil.h>
+
 #import <objc/runtime.h>
 
 NS_ASSUME_NONNULL_BEGIN
@@ -200,8 +202,18 @@ static BOOL isIOS9orLater() {
 + (nullable instancetype)sharedInstance {
   static dispatch_once_t onceToken;
   static FIRAuthAppDelegateProxy *_Nullable sharedInstance;
+  // iOS App extensions should not call [UIApplication sharedApplication], even if UIApplication
+  // responds to it.
+  static Class applicationClass = nil;
+  if (![FIRAppEnvironmentUtil isAppExtension]) {
+    Class cls = NSClassFromString(@"UIApplication");
+    if (cls && [cls respondsToSelector:NSSelectorFromString(@"sharedApplication")]) {
+      applicationClass = cls;
+    }
+  }
+  UIApplication *application = [applicationClass sharedApplication];
   dispatch_once(&onceToken, ^{
-    sharedInstance = [[self alloc] initWithApplication:[UIApplication sharedApplication]];
+    sharedInstance = [[self alloc] initWithApplication:application];
   });
   return sharedInstance;
 }
diff --git a/Firebase/Auth/Source/FIRAuthDefaultUIDelegate.m b/Firebase/Auth/Source/FIRAuthDefaultUIDelegate.m
index a00d0e9..e5aa7f4 100644
--- a/Firebase/Auth/Source/FIRAuthDefaultUIDelegate.m
+++ b/Firebase/Auth/Source/FIRAuthDefaultUIDelegate.m
@@ -16,6 +16,8 @@
 
 #import "FIRAuthDefaultUIDelegate.h"
 
+#import <FirebaseCore/FIRAppEnvironmentUtil.h>
+
 NS_ASSUME_NONNULL_BEGIN
 
 @interface FIRAuthDefaultUIDelegate ()
@@ -58,8 +60,17 @@ NS_ASSUME_NONNULL_BEGIN
 }
 
 + (id<FIRAuthUIDelegate>)defaultUIDelegate {
-  UIViewController *topViewController =
-      [UIApplication sharedApplication].keyWindow.rootViewController;
+  // iOS App extensions should not call [UIApplication sharedApplication], even if UIApplication
+  // responds to it.
+  static Class applicationClass = nil;
+  if (![FIRAppEnvironmentUtil isAppExtension]) {
+    Class cls = NSClassFromString(@"UIApplication");
+    if (cls && [cls respondsToSelector:NSSelectorFromString(@"sharedApplication")]) {
+      applicationClass = cls;
+    }
+  }
+  UIApplication *application = [applicationClass sharedApplication];
+  UIViewController *topViewController = application.keyWindow.rootViewController;
   while (true){
     if (topViewController.presentedViewController) {
       topViewController = topViewController.presentedViewController;