logo

Database

Insecure functionality

Need

Secure functionality to prevent exploitation by attackers

Context

• Usage of C# for building robust and scalable applications

• Usage of System for accessing and manipulating system-level functionalities

• Usage of System.IO for Input/Output operations in .NET development

• Usage of Microsoft.AspNetCore.Mvc for building web applications with ASP.NET Core

Description

1. Non compliant code

using System;
using System.IO;
using Microsoft.AspNetCore.Mvc;

namespace VulnerableApp.Controllers
{
    [Route("api/[controller]")]
    public class FileController : ControllerBase...

The above code represents a simple ASP.NET Core controller with a single action that reads a file from the server and returns its content. This action is vulnerable to Path Traversal attacks as it does not validate or sanitize the `fileName` parameter. An attacker can manipulate the `fileName` parameter to include `../` sequences, which can potentially allow them to read any file on the system that the web server has access to. For example, an attacker could request `/api/file/../../../etc/passwd` to retrieve a critical system file. This is a severe security issue as it can lead to information disclosure, allowing an attacker to gain information about the system, its structure, and its files. This information can be used for further attacks.

2. Steps

• Implement proper access control mechanisms to restrict unauthorized access to sensitive files.

• Validate user input to prevent directory traversal attacks.

• Use a secure file storage mechanism to store sensitive files.

• Implement proper error handling to prevent information leakage.

• Consider implementing authentication and authorization mechanisms to control access to the file functionality.

3. Secure code example

using System;
using System.IO;
using System.Linq;
using Microsoft.AspNetCore.Authorization;
using Microsoft.AspNetCore.Mvc;

namespace SecureApp.Controllers
    [Route("api/[controller]")]...

The updated code includes several security improvements to address the insecure functionality vulnerability: 1. **Access Control**: The `[Authorize]` attribute is added to the `FileController` class. This ensures that only authenticated users can access the file functionality. 2. **Input Validation**: The code now checks the file extension against a list of valid extensions before processing the request. This helps to prevent the execution of potentially malicious files. Additionally, the code checks for directory traversal attacks by looking for ".." in the file name. 3. **Secure File Storage**: The files are stored in a directory within the current directory of the application. This is a simple form of secure file storage, but in a real-world application, you might want to consider more secure options such as storing files in a database or using a cloud storage service with strong access controls. 4. **Error Handling**: The code now returns appropriate HTTP status codes and error messages when something goes wrong, such as when the requested file does not exist or the file name is invalid. This helps to prevent information leakage. 5. **Authentication and Authorization**: The `[Authorize]` attribute also provides a basic form of authorization by restricting access to authenticated users. In a real-world application, you might want to implement more granular access controls based on user roles or permissions.

On this page