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Authentication mechanism absence or evasion - Redirect

Need​

Implementation of a robust and secure authentication mechanism

Context​

  • Usage of Dart for building cross-platform mobile, web, and desktop applications
  • Usage of Shelf for managing and organizing data in a Node.js application

Description​

Non compliant code​

import 'package:shelf/shelf.dart' as shelf;

shelf.Response handleRequest(shelf.Request request) {
  var response;
  var username = request.url.queryParameters['username'];
  
  if(username != null) {
    response = shelf.Response.found('/dashboard');
  } else {
    response = shelf.Response.found('/login');
  }

  return response;
}

In the above code, we have a handleRequest function that handles incoming requests. It checks if the username query parameter is present in the request URL. If it is, it redirects the user to the '/dashboard' route, otherwise, it redirects the user to the '/login' route.

The vulnerability here is that the server does not validate the authenticity of the user before redirecting them to the dashboard. An attacker can simply add a username query parameter to the request URL and be redirected to the dashboard without having to authenticate. This can lead to unauthorized access to the application, compromising user data and application integrity.

Steps​

  • Implement an authentication mechanism to verify the identity of the user. This could be a password, a token, or a two-factor authentication system.
  • Check the authentication status of the user before redirecting to the dashboard. If the user is not authenticated, redirect them to the login page.
  • Do not rely solely on the username for authentication. An attacker could easily guess or know a valid username.
  • Encrypt sensitive data like usernames and passwords during transmission and at rest.
  • Use secure and updated libraries for handling user authentication.
  • Implement rate limiting to prevent brute force attacks.
  • Log and monitor authentication attempts to detect any suspicious activities.

Compliant code​

import 'package:shelf/shelf.dart' as shelf;
import 'package:shelf_auth/shelf_auth.dart';

shelf.Response handleRequest(shelf.Request request) {
  var response;
  var username = request.url.queryParameters['username'];
  var password = request.url.queryParameters['password'];

  // Implement an authentication mechanism
  var authMiddleware = authenticate(
    [new BasicAuthenticator(myBasicAuthFunction)],
    sessionHandler: new InMemorySessionHandler(),
    allowHttp: false,
  );

  // Check the authentication status of the user before redirecting
  if(username != null && password != null && authMiddleware.authenticate(username, password)) {
    response = shelf.Response.found('/dashboard');
  } else {
    response = shelf.Response.found('/login');
  }

  return response;
}

// This function should be replaced with your own function that validates the username and password
bool myBasicAuthFunction(String username, String password) {
  // Validate the username and password
  // This is just a placeholder function
  return true;
}

The code above fixes the vulnerability by implementing an authentication mechanism using the shelf_auth package. This package provides middleware for authenticating requests in a Shelf application.

The authenticate function is used to create an authentication middleware. This middleware uses a BasicAuthenticator which authenticates requests based on a username and password. The myBasicAuthFunction function is used to validate the username and password. This function should be replaced with your own function that validates the username and password.

The sessionHandler parameter is set to an InMemorySessionHandler. This handler stores session data in memory.

The allowHttp parameter is set to false to prevent the transmission of sensitive data over an unencrypted connection.

Before redirecting to the dashboard, the code checks if the username and password are not null and if the authentication is successful. If the authentication is not successful, the user is redirected to the login page.

This code does not rely solely on the username for authentication. It also requires a password. This makes it harder for an attacker to gain access to the application by guessing or knowing a valid username.

Please note that this code is a basic example and may need to be adjusted to fit your specific needs. For example, you may want to encrypt the username and password during transmission and at rest, use secure and updated libraries for handling user authentication, implement rate limiting to prevent brute force attacks, and log and monitor authentication attempts to detect any suspicious activities.

References​

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