NullReferenceException on PublicClientApplication.AcquireTokenAsync()

[brunokc]

Which Version of MSAL are you using ?
MSAL 2.0.1-preview

Which platform has the issue?
Xamarin iOS

What authentication flow has the issue?
iPhone with iOS 12.

Repro

    string[] MsalScopes = { "User.Read" };
    AuthenticationResult authResult = null;
    var app = App.PublicClientApplication;

    try
    {
        var users = await app.GetAccountsAsync();
        authResult = await app.AcquireTokenSilentAsync(MsalScopes, users.FirstOrDefault());
    }
    catch (MsalUiRequiredException e)
    {
        authResult = await app.AcquireTokenAsync(MsalScopes);
    }

Expected behavior
AcquireTokenAsync() should complete successfully and start the client authentication flow on the phone. This same code snipped worked just fine with MSAL 1.1.4-preview0002.

Note that AcquireTokenSilentAsync() works as expected, throwing a MsalUiRequiredException because users.Count is zero.

Actual behavior
The call into AcquireTokenAsync(MsalScopes) throws a NullReferenceException.

Additional context/ Logs / Screenshots
Stack trace when the exception is thrown:

  at Microsoft.Identity.Client.PublicClientApplication+<AcquireTokenForLoginHintCommonAsync>d__22.MoveNext () [0x0003a] in <707458e4f41141b3b1a5c88f7800ecf3>:0 
--- End of stack trace from previous location where exception was thrown ---
  at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess (System.Threading.Tasks.Task task) [0x00037] in /Library/Frameworks/Xamarin.iOS.framework/Versions/12.0.0.15/src/Xamarin.iOS/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:187 
  at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification (System.Threading.Tasks.Task task) [0x00028] in /Library/Frameworks/Xamarin.iOS.framework/Versions/12.0.0.15/src/Xamarin.iOS/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:156 
  at System.Runtime.CompilerServices.TaskAwaiter.ValidateEnd (System.Threading.Tasks.Task task) [0x00008] in /Library/Frameworks/Xamarin.iOS.framework/Versions/12.0.0.15/src/Xamarin.iOS/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:128 
  at System.Runtime.CompilerServices.ConfiguredTaskAwaitable`1+ConfiguredTaskAwaiter[TResult].GetResult () [0x00000] in <7d5a05cfcb09432d8cc656b9d781e54b>:0 
  at Microsoft.Identity.Client.PublicClientApplication+<AcquireTokenAsync>d__7.MoveNext () [0x00096] in <707458e4f41141b3b1a5c88f7800ecf3>:0 
--- End of stack trace from previous location where exception was thrown ---
  at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess (System.Threading.Tasks.Task task) [0x00037] in /Library/Frameworks/Xamarin.iOS.framework/Versions/12.0.0.15/src/Xamarin.iOS/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:187 
  at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification (System.Threading.Tasks.Task task) [0x00028] in /Library/Frameworks/Xamarin.iOS.framework/Versions/12.0.0.15/src/Xamarin.iOS/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:156 
  at System.Runtime.CompilerServices.TaskAwaiter.ValidateEnd (System.Threading.Tasks.Task task) [0x00008] in /Library/Frameworks/Xamarin.iOS.framework/Versions/12.0.0.15/src/Xamarin.iOS/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:128 
  at System.Runtime.CompilerServices.TaskAwaiter`1[TResult].GetResult () [0x00000] in <7d5a05cfcb09432d8cc656b9d781e54b>:0 
  at Project1.iOS.Services.LoginProvider+<LoginMicrosoftAccountAsync>d__9.MoveNext () [0x001d2] in C:\Users\<user>\OneDrive\Projects\Project1\client\Project1.iOS\Services\LoginProvider.cs:83 
--- End of stack trace from previous location where exception was thrown ---
  at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess (System.Threading.Tasks.Task task) [0x00037] in /Library/Frameworks/Xamarin.iOS.framework/Versions/12.0.0.15/src/Xamarin.iOS/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:187 
  at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification (System.Threading.Tasks.Task task) [0x00028] in /Library/Frameworks/Xamarin.iOS.framework/Versions/12.0.0.15/src/Xamarin.iOS/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:156 
  at System.Runtime.CompilerServices.TaskAwaiter.ValidateEnd (System.Threading.Tasks.Task task) [0x00008] in /Library/Frameworks/Xamarin.iOS.framework/Versions/12.0.0.15/src/Xamarin.iOS/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:128 
  at System.Runtime.CompilerServices.TaskAwaiter`1[TResult].GetResult () [0x00000] in <7d5a05cfcb09432d8cc656b9d781e54b>:0 
  at Project1.iOS.Services.LoginProvider+<LoginAsync>d__13.MoveNext () [0x00088] in C:\Users\<user>\OneDrive\Projects\Project1\client\Project1.iOS\Services\LoginProvider.cs:186 
--- End of stack trace from previous location where exception was thrown ---
  at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess (System.Threading.Tasks.Task task) [0x00037] in /Library/Frameworks/Xamarin.iOS.framework/Versions/12.0.0.15/src/Xamarin.iOS/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:187 
  at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification (System.Threading.Tasks.Task task) [0x00028] in /Library/Frameworks/Xamarin.iOS.framework/Versions/12.0.0.15/src/Xamarin.iOS/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:156 
  at System.Runtime.CompilerServices.TaskAwaiter.ValidateEnd (System.Threading.Tasks.Task task) [0x00008] in /Library/Frameworks/Xamarin.iOS.framework/Versions/12.0.0.15/src/Xamarin.iOS/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:128 
  at System.Runtime.CompilerServices.TaskAwaiter`1[TResult].GetResult () [0x00000] in <7d5a05cfcb09432d8cc656b9d781e54b>:0 
  at Project1.Views.MainPage+<loginProvider>d__6.MoveNext () [0x00050] in C:\Users\<user>\OneDrive\Projects\Project1\client\Project1\Views\MainPage.xaml.cs:61 
--- End of stack trace from previous location where exception was thrown ---
  at System.Runtime.CompilerServices.AsyncMethodBuilderCore+<>c.<ThrowAsync>b__6_0 (System.Object state) [0x00000] in /Library/Frameworks/Xamarin.iOS.framework/Versions/12.0.0.15/src/Xamarin.iOS/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/AsyncMethodBuilder.cs:1018 
  at Foundation.NSAsyncSynchronizationContextDispatcher.Apply () [0x00000] in /Library/Frameworks/Xamarin.iOS.framework/Versions/12.0.0.15/src/Xamarin.iOS/Foundation/NSAction.cs:178 
  at (wrapper managed-to-native) UIKit.UIApplication.UIApplicationMain(int,string[],intptr,intptr)
  at UIKit.UIApplication.Main (System.String[] args, System.IntPtr principal, System.IntPtr delegate) [0x00005] in /Library/Frameworks/Xamarin.iOS.framework/Versions/12.0.0.15/src/Xamarin.iOS/UIKit/UIApplication.cs:79 
  at UIKit.UIApplication.Main (System.String[] args, System.String principalClassName, System.String delegateClassName) [0x0002c] in /Library/Frameworks/Xamarin.iOS.framework/Versions/12.0.0.15/src/Xamarin.iOS/UIKit/UIApplication.cs:63 
  at Project1.iOS.Application.Main (System.String[] args) [0x00002] in C:\Users\<user>\OneDrive\Projects\Project1\client\Project1.iOS\Main.cs:19 

[edit: removed 'other issues' -- it was empty.]

[sergioacortes]

Same problem, I have tested it with emulator and physical device, I have downgrade to version 1.1.4 preview and it works.

Guess it is a problem within the constructor of PublicClientApplication class

Regards

[brunokc]

Thank you for confirming, @sergioacortes. To be clear though, in my case I can construct the class just fine. I set its RedirectUri property and only when I call AcquireTokenAsync() I get the exception. I have also downgraded to 1.1.4-preview0002 and things are working again.

[jennyf19]

@sergioacortes @brunokc

We are aware of the issue w/iOS simulator. Recommendation is to continue using 1.1.4-preview for the time being.

[sergioacortes]

@brunokc @jennyf19 I have downgrade to version 1.1.4 It works well but not with physical devices with iOS 12

Kind regards

[brunokc]

@sergioacortes, version 1.1.4 seems to be working fine for me on my iPhone with iOS 12. I can't use the resulting token to authenticate with my Azure Mobile Services but I believe that's a problem there (it doesn't look like it supports RS256 JWTs?). The resulting user returned by MSAL seems to be all correct, as far as I can tell.

[jennyf19]

@brunokc @sergioacortes

Can you try the following, using MSALv2.1.0-preview:

• In VS, under Debug tab, go to nameOfMyApp.iOS Properties...
• Then go to iOS Bundle Signing
• Under Custom Entitlements, click the ... and select the Entitlements.plist file from your app

In the csproj file of the iOS app, you should have this line now included:
<CodesignEntitlements>Entitlements.plist</CodesignEntitlements>
Also, in Entitlements.plist file, make sure you have enabled access to the keychain, using either the below access group or your own:

<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
  <key>keychain-access-groups</key>
  <array>
    <string>$(AppIdentifierPrefix)com.microsoft.adalcache</string>
  </array>
</dict>
</plist>

Remember to rebuild. Let me know if this works for you. It worked for me on a new iOS app and on our V2 sample.
cc: @jmprieur

[brunokc]

Update: it looks like I had forgotten to add the Entitlements for the debug version of my app, as you had requested. I did and now I can't run. I have a free Apple developer account, so there are things I can't do just yet. Unless you can drop the keychain-access-groups requirement, I'm afraid I can't validate the fix for you.

---

@jennyf19 , unfortunately it didn't seem to work for me. Using 2.1.0-preview, made sure I had keychain-access-groups in my Entitlements list (I already had it in there for other reasons) using my own access group, tried that same code and got the same NullReferenceException.

  at Microsoft.Identity.Client.PublicClientApplication+<AcquireTokenForLoginHintCommonAsync>d__22.MoveNext () [0x0003a] in <2a97cd931f1242d58d9f88cc99534e1d>:0 
--- End of stack trace from previous location where exception was thrown ---
  at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess (System.Threading.Tasks.Task task) [0x00037] in /Library/Frameworks/Xamarin.iOS.framework/Versions/12.0.0.15/src/Xamarin.iOS/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:187 
  at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification (System.Threading.Tasks.Task task) [0x00028] in /Library/Frameworks/Xamarin.iOS.framework/Versions/12.0.0.15/src/Xamarin.iOS/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:156 
  at System.Runtime.CompilerServices.TaskAwaiter.ValidateEnd (System.Threading.Tasks.Task task) [0x00008] in /Library/Frameworks/Xamarin.iOS.framework/Versions/12.0.0.15/src/Xamarin.iOS/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:128 
  at System.Runtime.CompilerServices.ConfiguredTaskAwaitable`1+ConfiguredTaskAwaiter[TResult].GetResult () [0x00000] in <7d5a05cfcb09432d8cc656b9d781e54b>:0 
  at Microsoft.Identity.Client.PublicClientApplication+<AcquireTokenAsync>d__7.MoveNext () [0x00096] in <2a97cd931f1242d58d9f88cc99534e1d>:0 
--- End of stack trace from previous location where exception was thrown ---
  at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess (System.Threading.Tasks.Task task) [0x00037] in /Library/Frameworks/Xamarin.iOS.framework/Versions/12.0.0.15/src/Xamarin.iOS/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:187 
  at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification (System.Threading.Tasks.Task task) [0x00028] in /Library/Frameworks/Xamarin.iOS.framework/Versions/12.0.0.15/src/Xamarin.iOS/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:156 
  at System.Runtime.CompilerServices.TaskAwaiter.ValidateEnd (System.Threading.Tasks.Task task) [0x00008] in /Library/Frameworks/Xamarin.iOS.framework/Versions/12.0.0.15/src/Xamarin.iOS/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:128 
  at System.Runtime.CompilerServices.TaskAwaiter`1[TResult].GetResult () [0x00000] in <7d5a05cfcb09432d8cc656b9d781e54b>:0 
  at Project.iOS.Services.LoginProvider+<LoginMicrosoftAccountAsync>d__9.MoveNext () [0x001c8] in C:\Users\<user>\OneDrive\Projects\Project\client\Project.iOS\Services\LoginProvider.cs:83 
--- End of stack trace from previous location where exception was thrown ---
  at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess (System.Threading.Tasks.Task task) [0x00037] in /Library/Frameworks/Xamarin.iOS.framework/Versions/12.0.0.15/src/Xamarin.iOS/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:187 
  at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification (System.Threading.Tasks.Task task) [0x00028] in /Library/Frameworks/Xamarin.iOS.framework/Versions/12.0.0.15/src/Xamarin.iOS/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:156 
  at System.Runtime.CompilerServices.TaskAwaiter.ValidateEnd (System.Threading.Tasks.Task task) [0x00008] in /Library/Frameworks/Xamarin.iOS.framework/Versions/12.0.0.15/src/Xamarin.iOS/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:128 
  at System.Runtime.CompilerServices.TaskAwaiter`1[TResult].GetResult () [0x00000] in <7d5a05cfcb09432d8cc656b9d781e54b>:0 
  at Project.iOS.Services.LoginProvider+<LoginAsync>d__13.MoveNext () [0x00088] in C:\Users\<user>\OneDrive\Projects\Project\client\Project.iOS\Services\LoginProvider.cs:185 
--- End of stack trace from previous location where exception was thrown ---
  at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess (System.Threading.Tasks.Task task) [0x00037] in /Library/Frameworks/Xamarin.iOS.framework/Versions/12.0.0.15/src/Xamarin.iOS/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:187 
  at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification (System.Threading.Tasks.Task task) [0x00028] in /Library/Frameworks/Xamarin.iOS.framework/Versions/12.0.0.15/src/Xamarin.iOS/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:156 
  at System.Runtime.CompilerServices.TaskAwaiter.ValidateEnd (System.Threading.Tasks.Task task) [0x00008] in /Library/Frameworks/Xamarin.iOS.framework/Versions/12.0.0.15/src/Xamarin.iOS/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/TaskAwaiter.cs:128 
  at System.Runtime.CompilerServices.TaskAwaiter`1[TResult].GetResult () [0x00000] in <7d5a05cfcb09432d8cc656b9d781e54b>:0 
  at Project.Views.MainPage+<loginProvider>d__6.MoveNext () [0x00050] in C:\Users\<user>\OneDrive\Projects\Project\client\Project\Views\MainPage.xaml.cs:61 
--- End of stack trace from previous location where exception was thrown ---
  at System.Runtime.CompilerServices.AsyncMethodBuilderCore+<>c.<ThrowAsync>b__6_0 (System.Object state) [0x00000] in /Library/Frameworks/Xamarin.iOS.framework/Versions/12.0.0.15/src/Xamarin.iOS/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/AsyncMethodBuilder.cs:1018 
  at Foundation.NSAsyncSynchronizationContextDispatcher.Apply () [0x00000] in /Library/Frameworks/Xamarin.iOS.framework/Versions/12.0.0.15/src/Xamarin.iOS/Foundation/NSAction.cs:178 
  at (wrapper managed-to-native) UIKit.UIApplication.UIApplicationMain(int,string[],intptr,intptr)
  at UIKit.UIApplication.Main (System.String[] args, System.IntPtr principal, System.IntPtr delegate) [0x00005] in /Library/Frameworks/Xamarin.iOS.framework/Versions/12.0.0.15/src/Xamarin.iOS/UIKit/UIApplication.cs:79 
  at UIKit.UIApplication.Main (System.String[] args, System.String principalClassName, System.String delegateClassName) [0x0002c] in /Library/Frameworks/Xamarin.iOS.framework/Versions/12.0.0.15/src/Xamarin.iOS/UIKit/UIApplication.cs:63 
  at Project.iOS.Application.Main (System.String[] args) [0x00002] in 

Again, this was tested on a real device (iPhone 6S with iOS 12).

Let me know if I can provide any additional information.

[jennyf19]

Thanks @brunokc - do you have this in the csproj file of the iOS app?<CodesignEntitlements>Entitlements.plist</CodesignEntitlements>

[brunokc]

I do. At first it was only under Release|iPhone. Following your instructions, I added it under Debug|iPhone as well. That's when deployment stopped working, probably due to my limited (free) developer account I'm using.

[jennyf19]

@brunokc
Returning error message in MSAL v2.2.0 and updates to wiki for configuration assistance

Can you try w/v2.2.0? if you're still having issues, email me (jeferrie@microsoft.com) and we'll go from there.

[jennyf19]

Fixed w/MSALv2.2.0 and update to Wiki w/clearer advice for iOS UIParent and fixing of incorrect link to Xamarin-v2 sample. FYI - @brunokc
cc: @jmprieur