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Insecure object reference - Session management

Need​

Secure session management

Context​

  • Usage of Python 3 for writing and executing Python code
  • Usage of Django for building web applications in Python

Description​

Non compliant code​

from django.contrib.auth import get_user_model
from django.contrib.sessions.models import Session

def close_user_session(request):
    email = request.GET.get('email')
    User = get_user_model()
    user = User.objects.get(email=email)
    Session.objects.filter(user=user).delete()

In the above code, the close_user_session function is used to close the session of a user by providing their email. This function is vulnerable to insecure object reference as it does not perform any authorization check to verify if the requestor has the necessary rights to close the session of the provided user email.

The function first retrieves the email from the request parameters using request.GET.get('email') and then uses this email to find the corresponding user in the database with User.objects.get(email=email).

After finding the user, it closes the session of this user by deleting all sessions associated with this user using Session.objects.filter(user=user).delete().

This means that if an attacker knows the email of another user, they can simply send a request to this function with the other user's email and close their session. This can lead to unauthorized session termination and can be used to disrupt the service for the user with the provided email.

Steps​

  • Authenticate the user making the request to ensure they have the necessary permissions to close sessions.
  • Implement a mechanism to prevent users from closing sessions of other users. This could be done by comparing the email in the request with the email of the user making the request.
  • Use secure session management techniques such as session tokens or cookies that are securely stored and transmitted.
  • Implement input validation to ensure that the email provided in the request is valid and belongs to an existing user.
  • Encrypt sensitive data such as email addresses to prevent them from being exposed in the request.
  • Implement error handling to prevent information leakage in case of errors.

Compliant code​

from django.contrib.auth import get_user_model
from django.contrib.sessions.models import Session
from django.contrib.auth.decorators import login_required
from django.http import HttpResponseForbidden

@login_required
def close_user_session(request):
    User = get_user_model()
    user = User.objects.get(email=request.user.email)
    if user is not None:
        Session.objects.filter(user=user).delete()
        return HttpResponse('Session closed successfully')
    else:
        return HttpResponseForbidden('You do not have permission to close this session')

The updated code now includes a decorator @login_required which ensures that the user is authenticated before they can close a session. This is a built-in Django decorator that redirects unauthenticated users to the login page or shows an error message.

The close_user_session function now gets the email of the currently logged-in user (request.user.email) instead of getting it from the request parameters. This ensures that a user can only close their own session and not the sessions of other users.

If the user object is found, the session associated with the user is deleted. If the user object is not found (which means the user is not authenticated), an HTTP 403 Forbidden response is returned, indicating that the server understood the request but refuses to authorize it.

This way, we ensure that only authenticated users can close their own sessions, thereby fixing the insecure direct object reference vulnerability.

References​

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