Xamarin-macios: NSUrlSessionHandler times out with empty credentials

[dotMorten]

If you set UseDefaultCredentials on the HttpClientHandler you'll get a default empty network credential. When copying the (default) credentials from that handler to the NSUrlSessionHandler, the request hangs until it times out, instead of failing with a 401 as this service should have.

Steps to Reproduce

1. Add the following code to an iOS app:

var handler = new NSUrlSessionHandler()
{
    Credentials = new System.Net.NetworkCredential("", "", "")
};
HttpClient client = new HttpClient(handler);
try
{
    var s1 = await client1.GetAsync("https://jigsaw.w3.org/HTTP/Basic/");
    Debug.WriteLine("Request 1 returned: " + s1.StatusCode.ToString()); // Never makes it here
}
catch(System.Exception ex)
{
    Debug.WriteLine("Request 1 Error: " + ex.Message); //Makes it here after connection times out
}

1. Run the app / above code
2. Notice that the request never completes, but times out with a cancelled exception about 90s later.
3. Remove the credential and it'll work

Side-note: Set user/pass to guest/guest and the request will succeed, so the Credential property does work with the right credential.

Expected Behavior

A 401 HTTP Status error should be returned.

Actual Behavior

Request times out with a cancelled exception

Environment

Microsoft Visual Studio Enterprise 2019
Version 16.5.3
VisualStudio.16.Release/16.5.3+30002.166
Microsoft .NET Framework
Version 4.8.03752

Installed Version: Enterprise

Visual C++ 2019   00435-60000-00000-AA802
Microsoft Visual C++ 2019

.NET Portability Analyzer   1.1.10808.0
Evaluates portability of assemblies across .NET platforms.

ArcGIS Runtime SDK for .NET   100.7.0
ArcGIS Runtime SDK for .NET allows developers to build immersive, native mapping applications for Windows, Android, and iOS devices using C#.  It includes five APIs: WPF to create apps for Windows Desktop, UWP to create Universal Windows apps, Xamarin.Android and Xamarin.iOS for Android and iOS apps that need access to native functionality, and Xamarin.Forms to create apps that share UI layouts across Android, iOS, and UWP.

ASP.NET and Web Tools 2019   16.5.236.49856
ASP.NET and Web Tools 2019

ASP.NET Web Frameworks and Tools 2019   16.5.236.49856
For additional information, visit https://www.asp.net/

Azure App Service Tools v3.0.0   16.5.236.49856
Azure App Service Tools v3.0.0

Azure Functions and Web Jobs Tools   16.5.236.49856
Azure Functions and Web Jobs Tools

C# Tools   3.5.0-beta4-20153-05+20b9af913f1b8ce0a62f72bea9e75e4aa3cf6b0e
C# components used in the IDE. Depending on your project type and settings, a different version of the compiler may be used.

Common Azure Tools   1.10
Provides common services for use by Azure Mobile Services and Microsoft Azure Tools.

Extensibility Message Bus   1.2.0 (d16-2@8b56e20)
Provides common messaging-based MEF services for loosely coupled Visual Studio extension components communication and integration.

GitHub.VisualStudio   2.10.8.8121
A Visual Studio Extension that brings the GitHub Flow into Visual Studio.

IntelliCode Extension   1.0
IntelliCode Visual Studio Extension Detailed Info

Microsoft Azure Tools   2.9
Microsoft Azure Tools for Microsoft Visual Studio 2019 - v2.9.30207.1

Microsoft Continuous Delivery Tools for Visual Studio   0.4
Simplifying the configuration of Azure DevOps pipelines from within the Visual Studio IDE.

Microsoft JVM Debugger   1.0
Provides support for connecting the Visual Studio debugger to JDWP compatible Java Virtual Machines

Microsoft Library Manager   2.1.25+gdacdb9b7a1
Install client-side libraries easily to any web project

Microsoft MI-Based Debugger   1.0
Provides support for connecting Visual Studio to MI compatible debuggers

Microsoft Visual C++ Wizards   1.0
Microsoft Visual C++ Wizards

Microsoft Visual Studio Tools for Containers   1.1
Develop, run, validate your ASP.NET Core applications in the target environment. F5 your application directly into a container with debugging, or CTRL + F5 to edit & refresh your app without having to rebuild the container.

Microsoft Visual Studio VC Package   1.0
Microsoft Visual Studio VC Package

Mono Debugging for Visual Studio   16.5.514 (c4f36a9)
Support for debugging Mono processes with Visual Studio.

NuGet Package Manager   5.5.0
NuGet Package Manager in Visual Studio. For more information about NuGet, visit https://docs.nuget.org/

Project System Tools   1.0
Tools for working with C#, VisualBasic, and F# projects.

ProjectServicesPackage Extension   1.0
ProjectServicesPackage Visual Studio Extension Detailed Info

Snapshot Debugging Extension   1.0
Snapshot Debugging Visual Studio Extension Detailed Info

SQL Server Data Tools   16.0.62003.05170
Microsoft SQL Server Data Tools

Test Adapter for Boost.Test   1.0
Enables Visual Studio's testing tools with unit tests written for Boost.Test.  The use terms and Third Party Notices are available in the extension installation directory.

Test Adapter for Google Test   1.0
Enables Visual Studio's testing tools with unit tests written for Google Test.  The use terms and Third Party Notices are available in the extension installation directory.

TypeScript Tools   16.0.20225.2001
TypeScript Tools for Microsoft Visual Studio

Visual Basic Tools   3.5.0-beta4-20153-05+20b9af913f1b8ce0a62f72bea9e75e4aa3cf6b0e
Visual Basic components used in the IDE. Depending on your project type and settings, a different version of the compiler may be used.

Visual F# Tools 10.8.0.0 for F# 4.7   16.5.0-beta.20181.6+85af456066acd4e76d2bc7821b44a325e46f2fca
Microsoft Visual F# Tools 10.8.0.0 for F# 4.7

Visual Studio Code Debug Adapter Host Package   1.0
Interop layer for hosting Visual Studio Code debug adapters in Visual Studio

Visual Studio Container Tools Extensions (Preview)   1.0
View, manage, and diagnose containers within Visual Studio.

Visual Studio Tools for CMake   1.0
Visual Studio Tools for CMake

Visual Studio Tools for Containers   1.0
Visual Studio Tools for Containers

VisualStudio.DeviceLog   1.0
Information about my package

VisualStudio.Foo   1.0
Information about my package

VisualStudio.Mac   1.0
Mac Extension for Visual Studio

Xamarin   16.5.000.533 (d16-5@9152e1b)
Visual Studio extension to enable development for Xamarin.iOS and Xamarin.Android.

Xamarin Designer   16.5.0.470 (remotes/origin/d16-5@681de3fd6)
Visual Studio extension to enable Xamarin Designer tools in Visual Studio.

Xamarin Templates   16.5.49 (0904f41)
Templates for building iOS, Android, and Windows apps with Xamarin and Xamarin.Forms.

Xamarin.Android SDK   10.2.0.100 (d16-5/988c811)
Xamarin.Android Reference Assemblies and MSBuild support.
    Mono: c0c5c78
    Java.Interop: xamarin/java.interop/d16-5@fc18c54
    ProGuard: xamarin/proguard/master@905836d
    SQLite: xamarin/sqlite/3.28.0@46204c4
    Xamarin.Android Tools: xamarin/xamarin-android-tools/d16-5@9f4ed4b


Xamarin.iOS and Xamarin.Mac SDK   13.16.0.13 (b75deaf)
Xamarin.iOS and Xamarin.Mac Reference Assemblies and MSBuild support.

[chamons]

I took a quick look at repro in ObjC:

NSURLSessionConfiguration * config;
NSURLSession * session;
NSURLSessionDownloadTask * downloadTask;

- (void)applicationDidFinishLaunching:(NSNotification *)aNotification{
    config = [NSURLSessionConfiguration defaultSessionConfiguration];
    session = [NSURLSession sessionWithConfiguration:config delegate:self delegateQueue:nil];
    NSURL * url = [[NSURL alloc] initWithString:@"https://jigsaw.w3.org/HTTP/Basic/"];

    downloadTask = [session downloadTaskWithURL:url completionHandler:^(NSURL * _Nullable location, NSURLResponse * _Nullable response, NSError * _Nullable error) {
        NSLog(@"%@", response);
    }];
    [downloadTask resume];
}

- (void)URLSession:(NSURLSession *)session didReceiveChallenge:(NSURLAuthenticationChallenge *)challenge
 completionHandler:(void (^)(NSURLSessionAuthChallengeDisposition disposition, NSURLCredential * _Nullable credential))completionHandler {
    NSURLCredential * cred = [[NSURLCredential alloc] initWithUser:@"" password:@"" persistence:NSURLCredentialPersistenceForSession];
    completionHandler(NSURLSessionAuthChallengeUseCredential, cred);
}

and I don't see a hang, so it looks like a bug at first glance.

[mandel-macaque]

Fun issue, should have been fixed by the PR.