Fixing Session Cookie Issues Over HTTPS in Reimpact Platform

The Problem

Users of the Reimpact platform were experiencing 401 errors during Livewire POST requests. The investigation revealed that session cookies were not being sent correctly when the application was served over HTTPS. The root cause was identified as the same_site attribute of the session cookie being null while the secure attribute was also false, leading to the browser blocking the cookie.

The Solution

To address this issue, the same_site attribute of the session cookie was explicitly set to lax as the default behavior. This ensures better compatibility with HTTPS and prevents session cookies from being blocked.

ini_set('session.cookie_samesite', 'Lax');

This configuration change ensures that the session cookie is sent with cross-site requests only when the user is navigating to the site, such as when following a link. It provides a balance between security and usability, preventing CSRF attacks while still allowing the session to be maintained during normal navigation.

Why Lax?

The Lax setting offers a reasonable default that enhances security without disrupting user experience in most common scenarios. Strict would provide the highest level of security, but it could also lead to issues with legitimate cross-site requests, such as those originating from external links. By setting same_site to Lax, the Reimpact platform ensures that session cookies are sent when users navigate to the site, but not when the request originates from a third-party site via a POST request.

Key Takeaway

Properly configuring session cookies, especially the same_site attribute, is crucial for maintaining session integrity over HTTPS. Explicitly setting same_site to Lax provides a balanced approach to security and usability, preventing common issues with cookie transmission in modern browsers.