Automatic information enumeration

Automatic information enumeration - Credit Cards

Need

Enhancement of credit card validation and security measures

Context

• Usage of Python 3 for scripting and general-purpose programming

• Usage of Django for building web applications in Python

Description

1. Non compliant code

from django.http import HttpResponse
from django.views import View

class CreditCardView(View):
    def get(self, request, *args, **kwargs):
        card_number = request.GET.get('card_number')
        expiration_date = request.GET.get('expiration_date')
...

The above code is a Django view that processes credit card information. The view retrieves the credit card number, expiration date, and security code from the GET parameters of the request and then processes the credit card information without any validation. The vulnerability lies in the fact that the view does not validate the credit card information before processing it. This allows an attacker to automatically enumerate credit card information by sending a large number of requests with different credit card numbers, expiration dates, and security codes. Since the view does not validate the credit card information, all these requests will be processed, potentially leading to a breach of sensitive information.

2. Steps

• Introduce input validation for the credit card information. This should include checks for the card number, expiration date, and security code.

• For the card number, implement a Luhn algorithm check to ensure it's a valid number.

• For the expiration date, ensure it's a future date and in the correct format (MM/YY or MM/YYYY).

• For the security code (CVV), ensure it's a 3 or 4 digit number, depending on the card type.

• Consider using a secure, third-party service for handling credit card information to ensure compliance with Payment Card Industry Data Security Standard (PCI DSS).

• Encrypt sensitive data like credit card information during transmission and at rest.

• Implement rate limiting to prevent brute force attacks and automatic enumeration of credit card information.

3. Secure code example

from django.http import HttpResponse
from django.views import View
from datetime import datetime
import re

class CreditCardView(View):
    def get(self, request, *args, **kwargs):
        expiration_date = request.GET.get('expiration_date')...

The updated code introduces input validation for the credit card information. This includes checks for the card number, expiration date, and security code. - For the card number, a Luhn algorithm check is implemented to ensure it's a valid number. The `luhn_check` function calculates the checksum of the card number and returns `True` if it's valid, `False` otherwise. - For the expiration date, the `validate_expiration_date` function checks if it's a future date and in the correct format (MM/YYYY). If the date is in the past or in an incorrect format, the function returns `False`. - For the security code (CVV), the `validate_security_code` function checks if it's a 3 or 4 digit number. If the security code doesn't match this pattern, the function returns `False`. If any of these checks fail, the `validate_credit_card` function returns `False` and the credit card information is not processed. Please note that this code does not include measures for PCI DSS compliance, encryption of sensitive data, or rate limiting. These are important considerations for a production environment and should be implemented as well.

References

• 254. Automatic information enumeration - Credit Cards

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