Xamarin Android, app crashes after selecting account (ADAL/broker) - xamarin.forms

Question

I have been using the ADAL library to authenticate users in my Xamarin Android app for a while and this all works fine. But after enabling Conditional Access in Azure for the backend API, I have to make use of a broker to make this work. I followed all instructions on the ADAL Wiki (https://github.com/AzureAD/azure-activedirectory-library-for-dotnet/wiki/leveraging-brokers-on-Android-and-iOS), but still without getting a working situation.
Xamarin Forms
ADAL version: 5.2.4
Below the code I used to authenticate the users:
public async Task<AuthenticationResult> Authenticate(string authority, string resource, string clientId, string returnUri)
{
var context = new AuthenticationContext(authority);
var param = new PlatformParameters(CrossCurrentActivity.Current.Activity, true, PromptBehavior.SelectAccount);
if (context.TokenCache.ReadItems().Count() > 0)
context = new AuthenticationContext(context.TokenCache.ReadItems().First().Authority);
try
{
authResult = await context.AcquireTokenAsync(resource, clientId, new Uri(returnUri), param, userId).ConfigureAwait(false);
return authResult;
}
catch
{
return null;
}
}
In the MainActivity I added the following:
protected override void OnResume()
{
base.OnResume();
if (ContextCompat.CheckSelfPermission(this, Manifest.Permission.GetAccounts) == (int)Android.Content.PM.Permission.Granted)
{
enablingBrokerSupport();
}
}
private void enablingBrokerSupport()
{
const string WORK_AND_SCHOOL_TYPE = "com.microsoft.workaccount";
var accManager = AccountManager.Get(Application.Context);
Account[] accounts = accManager.GetAccountsByType(WORK_AND_SCHOOL_TYPE);
Intent intent = AccountManager.NewChooseAccountIntent(null, null, new[] { WORK_AND_SCHOOL_TYPE }, null, null, null, null);
CrossCurrentActivity.Current.Activity.StartActivityForResult(intent, 999);
accManager.GetAccountsByType(WORK_AND_SCHOOL_TYPE);
}
public override void OnRequestPermissionsResult(int requestCode, string[] permissions, [GeneratedEnum] Android.Content.PM.Permission[] grantResults)
{
Xamarin.Essentials.Platform.OnRequestPermissionsResult(requestCode, permissions, grantResults);
base.OnRequestPermissionsResult(requestCode, permissions, grantResults);
}
protected override void OnActivityResult(int requestCode, Result resultCode, Intent data)
{
base.OnActivityResult(requestCode, resultCode, data);
AuthenticationAgentContinuationHelper.SetAuthenticationAgentContinuationEventArgs(requestCode, resultCode, data);
}
After launching the app, it first prompts for the GetAccunts permissions (as expected). After granting the permissions it will show the account picker in which my account is shown. Assuming it is getting the account from the broker, all the necessary code has to be correctly implemented to my understanding.
I can see the following error in the debug console:
[MonoDroid] UNHANDLED EXCEPTION:
[MonoDroid] System.NullReferenceException: Object reference not set to an instance of an object
[MonoDroid] at Microsoft.IdentityModel.Clients.ActiveDirectory.AuthenticationAgentContinuationHelper.SetAuthenticationAgentContinuationEventArgs (System.Int32 requestCode, Android.App.Result resultCode, Android.Content.Intent data) [0x0001c] in <41e5a54c101e43dca8a2f462dab041fa>:0
[MonoDroid] at ADALTest.Droid.MainActivity.OnActivityResult (System.Int32 requestCode, Android.App.Result resultCode, Android.Content.Intent data) [0x00009] in :0
[MonoDroid] at Android.App.Activity.n_OnActivityResult_IILandroid_content_Intent_ (System.IntPtr jnienv, System.IntPtr native__this, System.Int32 requestCode, System.Int32 native_resultCode, System.IntPtr native_data) [0x00014] in :0
[MonoDroid] at (wrapper dynamic-method) Android.Runtime.DynamicMethodNameCounter.6(intptr,intptr,int,int,intptr)
[DALTes] JNI RegisterNativeMethods: attempt to register 0 native methods for android.runtime.JavaProxyThrowable
[AndroidRuntime] Shutting down VM
[AndroidRuntime] FATAL EXCEPTION: main
[AndroidRuntime] Process: <my_packageid>, PID: 23545
[AndroidRuntime] android.runtime.JavaProxyThrowable: System.NullReferenceException: Object reference not set to an instance of an object
[AndroidRuntime] at Microsoft.IdentityModel.Clients.ActiveDirectory.AuthenticationAgentContinuationHelper.SetAuthenticationAgentContinuationEventArgs (System.Int32 requestCode, Android.App.Result resultCode, Android.Content.Intent data) [0x0001c] in <41e5a54c101e43dca8a2f462dab041fa>:0
[AndroidRuntime] at ADALTest.Droid.MainActivity.OnActivityResult (System.Int32 requestCode, Android.App.Result resultCode, Android.Content.Intent data) [0x00009] in :0
[AndroidRuntime] at Android.App.Activity.n_OnActivityResult_IILandroid_content_Intent_ (System.IntPtr jnienv, System.IntPtr native__this, System.Int32 requestCode, System.Int32 native_resultCode, System.IntPtr native_data) [0x00014] in :0
[AndroidRuntime] at (wrapper dynamic-method) Android.Runtime.DynamicMethodNameCounter.6(intptr,intptr,int,int,intptr)
[AndroidRuntime] at md5b4882cfeb0ca027f9661a63d1a4e24bc.MainActivity.n_onActivityResult(Native Method)
[AndroidRuntime] at md5b4882cfeb0ca027f9661a63d1a4e24bc.MainActivity.onActivityResult(MainActivity.java:65)
[AndroidRuntime] at android.app.Activity.dispatchActivityResult(Activity.java:7762)
[AndroidRuntime] at android.app.ActivityThread.deliverResults(ActivityThread.java:4603)
[AndroidRuntime] at android.app.ActivityThread.handleSendResult(ActivityThread.java:4652)
[AndroidRuntime] at android.app.servertransaction.ActivityResultItem.execute(ActivityResultItem.java:49)
[AndroidRuntime] at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:108)
[AndroidRuntime] at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:68)
[AndroidRuntime] at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1948)
[AndroidRuntime] at android.os.Handler.dispatchMessage(Handler.java:106)
[AndroidRuntime] at android.os.Looper.loop(Looper.java:214)
[AndroidRuntime] at android.app.ActivityThread.main(ActivityThread.java:7050)
[AndroidRuntime] at java.lang.reflect.Method.invoke(Native Method)
[AndroidRuntime] at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493)
[AndroidRuntime] at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:965)
Any help is appreciated.

Answer 1

You need to add try[}catch{} to the OnActivityResult and check witch param is null. Because from your logs i see
System.NullReferenceException: Object reference not set to an instance of an object [AndroidRuntime] at Microsoft.IdentityModel.Clients.ActiveDirectory.AuthenticationAgentContinuationHelper.SetAuthenticationAgentContinuationEventArgs (System.Int32 requestCode, Android.App.Result resultCode, Android.Content.Intent data)
apparently a mistake in this method
And maybe this will help https://github.com/AzureAD/azure-activedirectory-library-for-dotnet/issues/1000