ASP.NET Core - Policy-Based Authorization for Fine-Grained Access Control

ASP.NET Core provides a powerful feature called policy-based authorization, which allows you to define fine-grained access control rules for your application. Instead of hardcoding authorization checks throughout your code, you can centralize them in policy definitions.

To implement policy-based authorization:

• Define Policies: In your Startup.cs file or a separate authorization configuration file, define policies using the services.AddAuthorization() method. For example:

   services.AddAuthorization(options =>
   {
       options.AddPolicy("RequireAdminRole", policy =>
           policy.RequireRole("Admin"));
       options.AddPolicy("RequireMinimumAge", policy =>
           policy.Requirements.Add(new MinimumAgeRequirement(18)));
   });

• Create Policy Requirements: Create custom policy requirement classes that implement the IAuthorizationRequirement interface. In the example above, we have a custom requirement called MinimumAgeRequirement.

• Use Policies: Apply policies to your controllers or action methods using the [Authorize] attribute and specifying the policy name. For example:
  

   [Authorize(Policy = "RequireAdminRole")]
   public IActionResult AdminDashboard()
   {
       // This action can only be accessed by users with the "Admin" role.
       // ...
   }

• Handle Authorization Failures: If a user doesn't meet the policy requirements, ASP.NET Core will automatically handle authorization failures. You can customize the behavior by implementing an IAuthorizationHandler.

Policy-based authorization provides a flexible and maintainable way to control access to your application's resources based on various factors like roles, claims, and custom requirements. It promotes a clean separation of authorization logic from your business logic, making your application more secure and easier to manage.