Implementing Windows Authentication for Specific Users in a Blazor Server App

Learn how to control access to your Blazor Server app by implementing Windows Authentication for specific users using policies and authorization in .NET 6.0.
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Introduction

If you're working on a Blazor Server application and want to limit access to specific users in your organization, you may find yourself facing some challenges. Unlike traditional ASP.Net Web Forms, where you could easily use <allow users...> and <deny users...> tags in the web.config, Blazor does not support these tags natively. So, you might be wondering how to enforce Windows authentication for certain users when hosting your Blazor Server app with IIS in .NET 6.0.

This post will guide you through the process of setting up Windows authentication for specific users using policies in Blazor Server, allowing you to streamline access control in your application.

Setting Up Windows Authentication in Blazor Server

To allow only certain domain users to access your Blazor Server application, you can utilize the authorization policy feature. This requires some modifications to your application's setup, but it’s straightforward.

Step-by-Step Guide

1. Install Required Packages

First, ensure you have the necessary ASP.NET Core authentication packages installed in your Blazor Server application. Typically, this involves:

Microsoft.AspNetCore.Authentication.Negotiate

Microsoft.AspNetCore.Authorization

You can install these via NuGet Package Manager or using the command line.

2. Configure Windows Authentication

In your Startup.cs or wherever you configure services in your application, you need to set up Windows authentication. Example:

[[See Video to Reveal this Text or Code Snippet]]

3. Adding Authorization Policy

To restrict access to certain users, define an authorization policy in the ConfigureServices method. Here's a simple way to set this up:

[[See Video to Reveal this Text or Code Snippet]]

4. Implementing Policies

Feel free to customize the authorization logic to suit your needs. For instance, if you want to allow multiple users, you could modify the condition in the RequireAssertion method. Here's how you can extend it to check for a list of users:

[[See Video to Reveal this Text or Code Snippet]]

5. Test Your Application

Once you’ve configured your Blazor Server app this way, run it and try to access the application as different users within the specified Active Directory domain. The access should now be limited according to the rules you've set in the authorization policies.

Conclusion

Controlling access to your Blazor Server app through Windows authentication does require a bit of setup but can be achieved effectively using authorization policies. By leveraging ASP.NET Core's built-in authentication and authorization features, you can ensure that only the right users can access your application. This approach provides a robust framework for managing user access while meeting your application security needs.

We hope this guide helps you to successfully implement Windows authentication for specific users in your Blazor Server app. If you have any questions or need further assistance, feel free to leave a comment below!

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