[Bug] Windows Broker and Embedded Web View do check cancellation tokens

[kyle-rader]

Version: MSAL.NET @ 4.42
Platform: Windows 11, net5.0-windows10.0.17763.0
Auth flow: Broker and Interactive Web auth (embedded web view only)

Repro
@bgavrilMS - we have an easy repro internally and a current bugfix in the auth CLI.

private class MsalHttpClientFactoryAdaptor : IMsalHttpClientFactory
        {
            private HttpClient instance;

            public MsalHttpClientFactoryAdaptor(HttpClient instance)
            {
                if (instance == null)
                {
                    throw new ArgumentNullException(nameof(instance));
                }

                this.instance = instance;
            }

            public HttpClient GetHttpClient()
            {
                // MSAL calls this method each time it wants to use an HTTP client.
                // We ensure we only create a single instance to avoid socket exhaustion.
                return this.instance;
            }
        }
//---

ver pca = PublicClientApplicationBuilder
    .Create(this.clientId.ToString())
    .WithAuthority(this.Authority)
    .WithBroker();

var tokenSource = new CancellationStokenSource();
var timeout = TimeSpan.FromSeconds(15);

tokenSource.CancelAfter(timeout);

await pca.AcquireTokenInteractive(scopes)
    .ExecuteAsync(tokenSource.Token);

// Expect OperationCancelledException to be thrown - but the Web or broker UI hangs forever.

Expected behavior
An OperationCancelledException should be thrown by calling token.ThrowIfCancellationRequested().

Possible solution
Internally we have a workaround to run await a timer task that checks if the task is done every 100ms and after the timeout, returns a Task.FromResult<T>(null).

Additional context / logs / screenshots / links to code
We have debugged the un-cancellable call to this Task that runs with a custom Task Scheduler

microsoft-authentication-library-for-dotnet/src/client/Microsoft.Identity.Client/Platforms/Features/WebView2WebUi/WebView2WebUi.cs

Line 74 in 96ec275

Task.Factory.StartNew(

[MichelZ]

Is it as simple as using the cancellationToken in Wait?
e.g.

Task.Factory.StartNew(
        sendAuthorizeRequest,
        cancellationToken,
        TaskCreationOptions.None,
        staTaskScheduler).Wait(cancellationToken);

[MichelZ]

I took a different approach than just killing the thread. The Form gets auto-closed when the Cancellation Token is set, and an OperationCancelledException gets thrown

[pmaytak]

Released in 4.46.0