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.sessions.models import Session
from django.shortcuts import render

def logout_view(request):
    """
    Log out the user but not delete the session from the server side.
    """
    auth.logout(request)
    return render(request, 'logged_out.html')
        
        

In the above code, the logout_view function is used to log out a user. The auth.logout(request) method is used, which logs out the user associated with the given request. However, this does not delete the session on the server side.

This means that the session token associated with the user does not expire when the user logs out. If an attacker intercepts this session token, they can use it to make requests to the server as if they were the user, even after the user has logged out. This is because the server still recognizes the session token as valid.

This represents a significant security vulnerability known as insecure session management. It is important to ensure that session tokens are invalidated when a user logs out, to prevent potential misuse.

Steps

• Import the necessary Django module to delete a session.
• In the logout_view function, after logging out the user, delete the session from the server side.
• Ensure that the session token is invalidated and cannot be used to post requests afterwards.

Compliant code

        from django.contrib.sessions.models import Session
from django.shortcuts import render
from django.contrib.auth import logout

def logout_view(request):
    """
    Log out the user and delete the session from the server side.
    """
    logout(request)
    request.session.flush()
    return render(request, 'logged_out.html')
        
        

The updated code now includes a call to request.session.flush() after the user is logged out. The flush() method ensures that the current session data is completely deleted from the session store and a new, empty session object is created.

This is a crucial step in secure session management as it prevents session tokens from being reused after a user has logged out. Without this step, an attacker could potentially use an old session token to impersonate a user, leading to unauthorized access and potential data breaches.

By calling flush(), we ensure that the session token is invalidated and cannot be used to post requests afterwards, thus fixing the insecure session management vulnerability.

References

• 076. Insecure session management