ServiceAuthenticationBehavior throws NullReferenceException in GetAuthorizationService if new:ed up to be applied to one specific service only

I’m trying to apply a ServiceAuthenticationBehavior on a specific ServiceHostBase only. I do this by:

serviceBuilder.ConfigureAllServiceHostBase(serviceHost =>
{
    if (serviceHost.Description.ServiceType == typeof(MyCustomService))
    {
        serviceHost.Description.Behaviors.Remove<ServiceAuthorizationBehavior>(); // The shared Singleton instance
        serviceHost.Description.Behaviors.Add(new ServiceAuthorizationBehavior
        {
            ExternalAuthorizationPolicies = new ReadOnlyCollection<IAuthorizationPolicy>(new List<IAuthorizationPolicy> { new MyCustomAuthorizationPolicy() }),
            PrincipalPermissionMode = PrincipalPermissionMode.Custom,
        });
    }
}

However, when I do so, a NullReferenceException is thrown:

System.NullReferenceException
  HResult=0x80004003
  Message=Object reference not set to an instance of an object.
  Source=CoreWCF.Primitives
  StackTrace:
   at CoreWCF.Description.ServiceAuthorizationBehavior.CoreWCF.Description.IServiceBehavior.ApplyDispatchBehavior(ServiceDescription description, ServiceHostBase serviceHostBase) in /_/src/CoreWCF.Primitives/src/CoreWCF/Description/ServiceAuthorizationBehavior.cs:line 216

This code is called from DispatchBuilder.InitializeServiceHost.

It appears to be because the internal setter property ServiceScopeFactory is never assigned a value, so it remains null.

Only workaround I’ve found is to set it through reflection, i.e:

typeof(ServiceAuthorizationBehavior)
    .GetProperty("ServiceScopeFactory", System.Reflection.BindingFlags.NonPublic | System.Reflection.BindingFlags.Instance)
    .SetValue(tempServiceAuthorizationBehavior, app.ApplicationServices.GetService<IServiceScopeFactory>());

But this can’t be right. Is there a better way of doing this or have I stumbled upon a bug or unsupported scenario?

[g7ed6e]

@ksjoberg @allderidge please have a look to the test of the linked PR to get the expected behavior.

[allderidge]

I have the same issue. I’ve worked around using refection as above as in my case there are many ServiceAuthorizationBehavior’s with configuration dependent on the service.

So inside the code: builder.ConfigureServiceHostBase(service.Type, serviceHost =>

The behaviour is replaced via:

serviceHost.Description.Behaviors.RemoveAll<ServiceAuthorizationBehavior>();
var replace = new ServiceAuthorizationBehavior
{
    PrincipalPermissionMode = PrincipalPermissionMode.Custom,
    ExternalAuthorizationPolicies =
        ... policies that are dependent on service.Type ...
};
replace.GetType().GetProperty("ServiceScopeFactory", BindingFlags.Instance | BindingFlags.NonPublic)!
    .SetValue(replace, app.ApplicationServices.GetService<IServiceScopeFactory>());
serviceHost.Description.Behaviors.Add(replace);

Changing the service registration to make the behaviour transient using the following code:

            var registration = builder.Services.First(e => e.ServiceType == typeof(ServiceAuthorizationBehavior));
            builder.Services.Remove(registration);
            builder.Services.AddTransient<ServiceAuthorizationBehavior>();

Triggers the same null ref exception.

As far as I can tell there isn’t a way of fixing this by altering the setup of the app services.