Need

Implementation of robust data validation to prevent out-of-range access

Context

• Usage of C# for building robust and scalable applications
• Usage of Microsoft.AspNetCore.Mvc for building web applications with ASP.NET Core MVC
• Usage of Microsoft.AspNetCore.Authorization for implementing authorization and access control in ASP.NET Core applications

Description

Non compliant code

        [Authorize]
public class EmployeeController : Controller
{
    [HttpGet]
    public IActionResult Index()
    {
        return View();
    }

    [HttpGet]
    public IActionResult Manage()
    {
        return View();
    }
}
        
        

The above code represents a controller in an ASP.NET Core application. The EmployeeController class is decorated with the Authorize attribute, which means that all actions within this controller require the user to be authenticated.

There are two action methods within this controller: Index and Manage. The Index method is intended to be accessible to all authenticated users, while the Manage method is intended to be restricted to only certain users, such as administrators.

However, there's no additional authorization logic in place to enforce this restriction. This means that any authenticated user could potentially access the Manage method by directly navigating to its absolute path (e.g., https://yourwebsite.com/Employee/Manage), even if they're not supposed to have access to this functionality.

This is a vulnerability because it allows for privilege escalation: a user with lower privileges could potentially perform actions that should be restricted to users with higher privileges. This could lead to unauthorized changes to employee data, among other potential issues.

Steps

• Implement input validation to ensure that the user's input is within the expected range.
• Use authorization policies to restrict access to specific functionalities based on user roles or permissions.
• Consider implementing a role-based access control system to manage user permissions more effectively.
• Regularly review and update the authorization policies to ensure they align with the current security requirements.
• Perform security testing and code reviews to identify and address any potential vulnerabilities.
• Stay updated with the latest security best practices and guidelines provided by the ASP.NET Core community.

Compliant code

        [Authorize]
public class EmployeeController : Controller
{
    [HttpGet]
    [Authorize(Policy = "EmployeeManagement")]
    public IActionResult Index()
    {
        return View();
    }

    [HttpGet]
    [Authorize(Policy = "EmployeeManagement")]
    public IActionResult Manage()
    {
        return View();
    }
}
        
        

The updated code now includes an authorization policy named "EmployeeManagement" on both the Index and Manage methods. This policy should be defined in the Startup.cs file and should specify the roles or permissions required to access these methods.

The [Authorize(Policy = "EmployeeManagement")] attribute ensures that only users who meet the requirements of the "EmployeeManagement" policy can access the Index and Manage methods. If a user does not meet these requirements, they will receive a 403 Forbidden response when trying to access these methods.

This approach effectively prevents users from bypassing restrictions by using absolute paths, as the server will validate their permissions before granting access to these methods.

Remember to define the "EmployeeManagement" policy in your Startup.cs file, specifying the roles or permissions required to access the Index and Manage methods. Here is an example of how you might define this policy:

                services.AddAuthorization(options =>
{
    options.AddPolicy("EmployeeManagement", policy =>
        policy.RequireClaim("Permission", "EmployeeManagement"));
});

            

References

• 198. Lack of data validation - Out of range