With the release of ASP.NET Core 2.0, a lot of things were changed from a security perspective. To help you getting started I can recommend the ASP.NET Core Authorization Lab created by Barry Dorans.
In this workshop you will learn how to:
- Setup and configure the authentication middleware
- Add global authorization using authorization policies
- Configure role based access control
- Create simple claim based policies and more advanced code based policies
- Add resource bases requirements
- Applying authorization in your MVC views