How to implement IP whitelists in ASP.NET Core 6

When working with applications in ASP.NET Core 6, you will often want to create an IP address whitelist to allow client requests only from certain IP addresses, while blocking requests from all other addresses. We do this to protect our API endpoints from potentially malicious requests from bad actors, while at the same time allowing requests originating from trusted IP addresses.

Also called an IP safelist, an IP whitelist helps to ensure that our application’s sensitive data is exposed only to IP addresses that we know and trust. An IP whitelist can be implemented in ASP.NET Core by using middleware or by using MVC action filters. This article shows how we can implement an IP whitelist in ASP.NET Core 6 by using middleware.

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To work with the code examples provided in this article, you should have Visual Studio 2022 installed in your system. If you don’t already have a copy, you can download Visual Studio 2022 here.

Create an ASP.NET Core Web API project in Visual Studio 2022

First off, let’s create an ASP.NET Core project in Visual Studio 2022. Following these steps will create a new ASP.NET Core Web API project in Visual Studio 2022:

1. Launch the Visual Studio 2022 IDE.
2. Click on “Create new project.”
3. In the “Create new project” window, select “ASP.NET Core Web API” from the list of templates displayed.
4. Click Next.
5. In the “Configure your new project” window, specify the name and location for the new project.
6. Optionally check the “Place solution and project in the same directory” check box, depending on your preferences.
7. Click Next.
8. In the “Additional Information” window shown next, ensure that the “Use controllers…” check box is checked. Leave the “Authentication Type” set to “None” (default). And make sure the check boxes “Enable Docker,” “Configure for HTTPS,” and “Enable Open API Support” are unchecked as we won’t be using any of those features here.
9. Click Create.

We’ll use this ASP.NET Core 6 Web API project to work with IP whitelists in the subsequent sections of this article.

The Program class in ASP.NET Core 6

Read more here.

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