Need

Implementation of proper data validation for OTP tokenCode parameter

Context

Description

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

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

  if (tokenCode == null) {
    return shelf.Response(400, body: 'Missing tokenCode parameter');
...

The above code represents a handler for a request in a backend application using the shelf framework in Dart. The vulnerability lies in the `handleRequest` function, where the `tokenCode` parameter is fetched from the URL query parameters. The `tokenCode` is then passed to the `validateToken` function to verify its validity. The issue here is that there's no evidence of validation of the values sent in the `tokenCode` parameter to complete the request, allowing random values to be used in multiple attempts. This means an attacker could potentially brute force the OTP by sending multiple requests with different `tokenCode` values. Since there's no limit or validation on these attempts, the application is vulnerable to this type of attack.

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

// Create a memory store for rate limiting
final store = MemoryStore();

// Define the rate limiting rules
...

The code above fixes the vulnerability by implementing several security measures: 1. **Rate Limiting**: A rate limiting mechanism is implemented using the `rate_limiter` package. This limits the number of attempts a user can make within a certain time period (5 attempts every 15 minutes in this example). If a user exceeds this limit, a 429 (Too Many Requests) response is returned. 2. **Token Format Validation**: Before validating the token, the code checks if the token is in the correct format and length using a regular expression. This is a simple example and should be replaced with your own validation logic. 3. **Token Validation**: The `validateToken` function simulates token validation. Consider using a more secure method for generating and validating tokens, such as JWT or a library specifically designed for OTPs. Note: This code does not implement a lockout mechanism or logging of failed attempts. These features would require a more complex setup, possibly involving a database or external logging service, and are beyond the scope of this example.

References