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Insecure functionality - Fingerprint

Need​

Secure and controlled user data updates

Context​

  • Usage of Dart 2.0 for developing high-performance, cross-platform applications
  • Usage of Shelf for managing and organizing data in a Node.js application
  • Usage of shelf_router for creating a router in a Shelf application
  • Usage of dart:convert for encoding and decoding data in Dart

Description​

Non compliant code​

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

class UserController {
  final Router _router;

  UserController(this._router) {
    _router.post('/updateUser', _updateUser);
  }

  shelf.Response _updateUser(shelf.Request request) async {
    final body = jsonDecode(await request.readAsString()) as Map<String, dynamic>;

    String userId = body['userId'];
    String userData = body['userData'];

    // update user data in database
    updateUserInDatabase(userId, userData);

    return shelf.Response.ok('User data updated');
  }

  void updateUserInDatabase(String userId, String userData) {
    // This function updates the user data in the database
  }
}

void main() {
  final router = Router();
  UserController(router);

  // start server
}

The above code represents a simple Dart backend application using the shelf framework.

The vulnerability lies within the UserController class, specifically the _updateUser method. This method is responsible for handling POST requests to the /updateUser endpoint.

When a POST request is made to this endpoint, the method reads the request body, which is expected to be a JSON object containing a userId and userData. It then directly uses these values to update the user data in the database with the updateUserInDatabase function.

The problem here is that there is no authentication or authorization process in place to verify the identity of the user making the request. This means that any user, even if they're not the owner of the account, can send a POST request to this endpoint with any userId and userData they want, and the server will update the user data in the database without question.

This is a serious security flaw, as it could allow malicious users to change other users' data, leading to potential data corruption, privacy violations, and other issues.

Steps​

  • Authenticate the user before allowing them to update data. This can be done by implementing an authentication middleware that verifies the user's identity before processing the request.
  • Authorize the user to ensure they have the necessary permissions to update the data. This can be done by checking the user's role or permissions in the system.
  • Validate the input data to ensure it is in the correct format and does not contain any malicious content. This can be done by using a schema validation library or writing custom validation logic.
  • Implement rate limiting to prevent brute force attacks. This can be done by tracking the number of requests from a user within a certain time period and blocking them if they exceed the limit.
  • Log all attempts to update user data for auditing purposes. This can be done by using a logging library or service.

Compliant code​

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

class UserController {
  final Router _router;

  UserController(this._router) {
    _router.post('/updateUser', _authenticate, _authorize, _validateInput, _rateLimit, _updateUser);
  }

  shelf.Middleware _authenticate(shelf.Request request) {
    // Implement authentication logic here
  }

  shelf.Middleware _authorize(shelf.Request request) {
    // Implement authorization logic here
  }

  shelf.Middleware _validateInput(shelf.Request request) {
    // Implement input validation logic here
  }

  shelf.Middleware _rateLimit(shelf.Request request) {
    // Implement rate limiting logic here
  }

  shelf.Response _updateUser(shelf.Request request) async {
    final body = jsonDecode(await request.readAsString()) as Map<String, dynamic>;

    String userId = body['userId'];
    String userData = body['userData'];

    // update user data in database
    updateUserInDatabase(userId, userData);

    // Log the update attempt
    logUpdateAttempt(userId, userData);

    return shelf.Response.ok('User data updated');
  }

  void updateUserInDatabase(String userId, String userData) {
    // This function updates the user data in the database
  }

  void logUpdateAttempt(String userId, String userData) {
    // This function logs the update attempt
  }
}

void main() {
  final router = Router();
  UserController(router);

  // start server
}

The updated code includes several middleware functions that are executed before the _updateUser function. These middleware functions are used to authenticate the user, authorize the user, validate the input data, and implement rate limiting.

The _authenticate function is used to verify the user's identity. This can be done by checking the user's credentials against a database or another trusted source.

The _authorize function is used to check if the user has the necessary permissions to update the data. This can be done by checking the user's role or permissions in the system.

The _validateInput function is used to ensure that the input data is in the correct format and does not contain any malicious content. This can be done by using a schema validation library or writing custom validation logic.

The _rateLimit function is used to prevent brute force attacks by limiting the number of requests a user can make within a certain time period.

The _updateUser function now also includes a call to the logUpdateAttempt function, which logs all attempts to update user data. This can be useful for auditing purposes and for identifying potential security threats.

References​

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