Implementation of proper data validation for OTP tokenCode parameter
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');
}
// Here is the vulnerability, no validation of the tokenCode
// Any random values can be used in multiple attempts
var isTokenValid = validateToken(tokenCode);
if (isTokenValid) {
return shelf.Response.ok('Token is valid');
} else {
return shelf.Response(400, body: 'Invalid token');
}
}
bool validateToken(String token) {
// Simulate token validation
return token == '123456';
}
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
final rateLimiter = RateLimiter(store, points: 5, duration: Duration(minutes: 15));
shelf.Response handleRequest(shelf.Request request) {
var tokenCode = request.url.queryParameters['tokenCode'];
if (tokenCode == null || !isTokenFormatValid(tokenCode)) {
return shelf.Response(400, body: 'Missing or invalid tokenCode parameter');
}
// Check if the user has exceeded the rate limit
if (!rateLimiter.consume(request.remoteAddress)) {
return shelf.Response(429, body: 'Too many requests');
}
var isTokenValid = validateToken(tokenCode);
if (isTokenValid) {
return shelf.Response.ok('Token is valid');
} else {
return shelf.Response(400, body: 'Invalid token');
}
}
bool isTokenFormatValid(String token) {
// Check if the token is in the correct format and length
// This is a simple example, replace with your own validation logic
return RegExp(r'^\\d{6}$').hasMatch(token);
}
bool validateToken(String token) {
// Simulate token validation
// Consider using a more secure method for generating and validating tokens
return token == '123456';
}
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.