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Automatic information enumeration - Credit Cards

Need​

Enhancement of credit card validation and security measures

Context​

  • Usage of TypeScript for statically typed JavaScript development
  • Usage of Express for building web applications and handling HTTP requests

Description​

Non compliant code​

import express from 'express';

const app = express();

app.post('/payment', (req, res) => {
  const { creditCardNumber, expirationDate, securityCode } = req.body;

  // Process payment without validating credit card information
  // ...

  res.send('Payment processed successfully');
});

app.listen(3000, () => {
  console.log('Server started on port 3000');
});

The vulnerability in this code is that it allows for automatic enumeration of credit card information. The code receives credit card details, including the credit card number, expiration date, and security code, through a POST request to the '/payment' endpoint. However, it does not validate or filter the received credit card information.

This means that an attacker could potentially exploit this vulnerability by sending multiple requests with different credit card numbers, expiration dates, and security codes, and the server would process the payment without validating the credit card information. This could lead to unauthorized access to credit card details and potential misuse of the credit card information.

To mitigate this vulnerability, it is recommended to implement proper validation and filtering of the credit card information received. This could include implementing checks to ensure that the credit card number is valid, the expiration date is in the correct format and not expired, and the security code meets the required criteria. Additionally, it is important to use secure methods for transmitting and storing credit card information, such as encrypting the data and following PCI DSS compliance guidelines.

Steps​

  • Implement validation for credit card information such as credit card number, expiration date, and security code
  • Use a library or algorithm to validate the credit card number
  • Implement validation for the expiration date to ensure it is a valid date in the future
  • Implement validation for the security code to ensure it is a valid code according to the credit card provider's rules
  • If any of the validations fail, return an appropriate error response instead of processing the payment
  • Consider storing only the last 4 digits of the credit card number for security purposes
  • Encrypt or tokenize the credit card information before storing it in a database

Compliant code​

import express from 'express';
import { validateCreditCardNumber, validateExpirationDate, validateSecurityCode } from './validators';

const app = express();

app.use(express.json());

app.post('/payment', (req, res) => {
  const { creditCardNumber, expirationDate, securityCode } = req.body;

  if (!validateCreditCardNumber(creditCardNumber)) {
    return res.status(400).json({ error: 'Invalid credit card number' });
  }

  if (!validateExpirationDate(expirationDate)) {
    return res.status(400).json({ error: 'Invalid expiration date' });
  }

  if (!validateSecurityCode(securityCode)) {
    return res.status(400).json({ error: 'Invalid security code' });
  }

  // Process payment with validated credit card information
  // ...

  res.send('Payment processed successfully');
});

app.listen(3000, () => {
  console.log('Server started on port 3000');
});

The fixed code addresses the vulnerability by implementing input validation for credit card information. Here's an explanation of the changes made:

  1. The code imports the necessary validation functions from a separate file called 'validators'. This file likely contains functions that validate the credit card number, expiration date, and security code.

  2. The Express server is created using the 'express' module.

  3. The server is configured to parse JSON data using the 'express.json()' middleware.

  4. A POST route is defined for '/payment' which expects the credit card information in the request body.

  5. Inside the route handler, the credit card number, expiration date, and security code are extracted from the request body.

  6. The extracted credit card number is then passed to the 'validateCreditCardNumber' function. If the credit card number is invalid, a 400 response is sent back with an error message indicating the issue.

  7. Similarly, the expiration date and security code are validated using the 'validateExpirationDate' and 'validateSecurityCode' functions respectively. If any of these validations fail, a 400 response is sent back with an appropriate error message.

  8. If all the credit card information is valid, the code proceeds to process the payment using the validated credit card information. This part is not shown in the code snippet.

  9. Finally, a success message is sent back to the client indicating that the payment was processed successfully.

By implementing these validation checks, the code ensures that only valid credit card information is accepted for processing payments, mitigating the risk of automatic information enumeration.

References​

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