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Insecure functionality - Fingerprint

Need​

Secure and controlled user data updates

Context​

  • Usage of Python 3 for developing Python applications
  • Usage of Django for building web applications

Description​

Non compliant code​

from django.shortcuts import render
from django.views.decorators.csrf import csrf_exempt
from .models import UserProfile

@csrf_exempt
def update_user_profile(request):
    if request.method == 'POST':
        user_id = request.POST.get('user_id')
        new_fingerprint = request.POST.get('fingerprint')

        user = UserProfile.objects.get(id=user_id)
        user.fingerprint = new_fingerprint
        user.save()

        return render(request, 'update_successful.html')

In the above code, the update_user_profile function is used to update the user's fingerprint. This function is decorated with @csrf_exempt, which means that it will not perform CSRF token validation. CSRF (Cross-Site Request Forgery) is a type of attack that tricks the victim into submitting a malicious request.

The function retrieves the user_id and new_fingerprint from the POST request data. It then fetches the user with the corresponding user_id from the UserProfile model. The fingerprint of this user is then updated with the new_fingerprint value and saved to the database.

The problem here is that the function does not check if the request was made by an authenticated user who has the right to update the user data. This means that any user, authenticated or not, can send a POST request to this endpoint and update the fingerprint of any user. This is a serious security vulnerability as it allows for unsolicited user data updates.

Steps​

  • Authenticate the user before allowing any updates to user data. This can be done by checking if the user is logged in and if the user has the necessary permissions to update the data.
  • Validate the user input. Ensure that the 'user_id' and 'fingerprint' are valid before using them in the query. This can be done using Django's form validation or custom validation.
  • Implement CSRF protection. The @csrf_exempt decorator should be removed as it disables CSRF protection. Django has built-in CSRF protection that should be used.
  • Limit the rate of requests to prevent brute force attacks. This can be done using Django's built-in rate limiting or a third-party library.
  • Encrypt sensitive data like the fingerprint. This can be done using Django's built-in encryption or a third-party library.
  • Log all attempts to update user data. This can help in identifying suspicious activity and can be done using Django's logging.

Compliant code​

from django.shortcuts import render
from django.contrib.auth.decorators import login_required
from .models import UserProfile
from .forms import UserProfileForm
from django.views.decorators.cache import ratelimit_page
from django.core.exceptions import PermissionDenied
from django.contrib.auth.models import User

@login_required
@ratelimit_page('100/m')  # limit to 100 requests per minute
def update_user_profile(request):
    if request.method == 'POST':
        form = UserProfileForm(request.POST)
        if form.is_valid():
            user_id = form.cleaned_data['user_id']
            new_fingerprint = form.cleaned_data['fingerprint']

            # Check if the user has permission to update the data
            if request.user.id != user_id:
                raise PermissionDenied

            user = UserProfile.objects.get(id=user_id)
            user.fingerprint = new_fingerprint
            user.save()

            return render(request, 'update_successful.html')
        else:
            return render(request, 'error.html', {'form': form})

The updated code includes several security measures to prevent unsolicited user data updates:

  1. User Authentication: The @login_required decorator is used to ensure that the user is logged in before they can update their data.

  2. Rate Limiting: The @ratelimit_page decorator is used to limit the number of requests a user can make to update their data. This helps prevent brute force attacks.

  3. Input Validation: The UserProfileForm is used to validate the user input. This ensures that the 'user_id' and 'fingerprint' are valid before they are used in the query.

  4. Permission Check: The code checks if the logged-in user is the same as the user whose data is being updated. If not, a PermissionDenied exception is raised.

  5. CSRF Protection: CSRF protection is enabled by default in Django. The @csrf_exempt decorator, which was disabling this protection, has been removed.

  6. Data Encryption: Although not shown in the code, sensitive data like the fingerprint should be encrypted before being stored in the database. This can be done using Django's built-in encryption or a third-party library.

  7. Logging: Although not shown in the code, all attempts to update user data should be logged. This can help in identifying suspicious activity. This can be done using Django's logging.

References​

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