CWE-554: ASP.NET Misconfiguration: Not Using Input Validation Framework

What is ASP.NET Misconfiguration: Not Using Input Validation Framework?

• Overview: This vulnerability occurs when an ASP.NET application is misconfigured by not using an input validation framework. This leaves the application susceptible to malicious input that can lead to security breaches.

• Exploitation Methods:

• Attackers can exploit this by injecting malicious data into the application, which the application processes without validation.
• Common attack patterns include SQL injection, cross-site scripting (XSS), and command injection, where attackers send input that manipulates the application's behavior or accesses unauthorized data.

• Security Impact:

• Direct consequences include unauthorized access to sensitive data, data corruption, and compromise of application integrity.
• Potential cascading effects include further exploitation of the system, such as privilege escalation or use of the compromised application as a launch point for attacks on other systems.
• Business impact could include loss of customer trust, legal implications, and financial loss due to compromised data and service outages.

• Prevention Guidelines:

• Specific code-level fixes include implementing input validation using frameworks such as ASP.NET's own validation controls or libraries like FluentValidation.
• Security best practices include validating all input against a whitelist of acceptable values, applying the principle of least privilege, and ensuring proper error handling that does not expose sensitive information.
• Recommended tools and frameworks include using ASP.NET's built-in validation features, employing third-party validation libraries, and conducting regular security audits and testing.

Corgea can automatically detect and fix ASP.NET Misconfiguration: Not Using Input Validation Framework in your codebase. [Try Corgea free today](https://corgea.app).

Technical Details

Likelihood of Exploit: Not specified

Affected Languages: ASP.NET

Affected Technologies: Not specified

Vulnerable Code Example

ASP.NET Example

// HomeController.cs {6-12}
// This example demonstrates a vulnerability where user input is not validated
using Microsoft.AspNetCore.Mvc;

public class HomeController : Controller
{
    // Action method vulnerable to input validation issues
    [HttpPost]
    public IActionResult SubmitForm(string userInput)
    {
        // Directly using user input without validation
        // This can lead to security issues like XSS or SQL Injection
        ViewBag.Message = "User input: " + userInput;
        return View();
    }
}

Explanation of Vulnerability:

• Lack of Input Validation: The SubmitForm method directly uses the userInput parameter without any validation. This can lead to security vulnerabilities such as Cross-Site Scripting (XSS) or SQL Injection if the input is used in database queries.
• No Output Encoding: The user input is directly appended to ViewBag.Message and rendered in the view, making the application susceptible to XSS attacks.

How to fix ASP.NET Misconfiguration: Not Using Input Validation Framework?

Fixed Code Example

// HomeController.cs {5-14, 18-30}
// Fixed code implementing input validation using ASP.NET Core's validation framework
using Microsoft.AspNetCore.Mvc;
using System.ComponentModel.DataAnnotations;
using System.Net;

public class UserInputModel
{
    // Using validation attributes to ensure input safety
    [Required(ErrorMessage = "Input is required.")]
    [StringLength(100, ErrorMessage = "Input too long.")]
    public string UserInput { get; set; }
}

public class HomeController : Controller
{
    [HttpPost]
    public IActionResult SubmitForm(UserInputModel model)
    {
        if (ModelState.IsValid) // Ensures input meets validation criteria
        {
            // Properly encode output to prevent XSS
            ViewBag.Message = "User input: " + WebUtility.HtmlEncode(model.UserInput);
        }
        else
        {
            ViewBag.Message = "Invalid input.";
        }
        return View(model);
    }
}

Explanation of Fix:

• Model Class with Validation: A UserInputModel class is created with validation attributes such as [Required] and [StringLength], ensuring the input is both required and within a specified length.
• Model Binding and Validation: The SubmitForm method now accepts a UserInputModel object. It checks ModelState.IsValid to ensure the input meets the defined validation criteria before proceeding.
• Output Encoding: The WebUtility.HtmlEncode method is used to encode the user input before rendering it. This prevents XSS by ensuring any HTML tags in the input are rendered harmlessly.

By implementing these practices, the application is better protected against common input-related vulnerabilities. The code now follows best practices for input validation and output encoding in ASP.NET Core.