Fix reviving revoked sessions and invalidating login (#16943)

Up until now, we have used Devise's Rememberable mechanism to re-log users
after the end of their browser sessions. This mechanism relies on a signed
cookie containing a token. That token was stored on the user's record,
meaning it was shared across all logged in browsers, meaning truly revoking
a browser's ability to auto-log-in involves revoking the token itself, and
revoking access from *all* logged-in browsers.

We had a session mechanism that dynamically checks whether a user's session
has been disabled, and would log out the user if so. However, this would only
clear a session being actively used, and a new one could be respawned with
the `remember_user_token` cookie.

In practice, this caused two issues:
- sessions could be revived after being closed from /auth/edit (security issue)
- auto-log-in would be disabled for *all* browsers after logging out from one
  of them

This PR removes the `remember_token` mechanism and treats the `_session_id`
cookie/token as a browser-specific `remember_token`, fixing both issues.

1 files changed, 0 insertions, 3 deletions

diff --git a/app/controllers/auth/registrations_controller.rb b/app/controllers/auth/registrations_controller.rb
index a3114ab25..3c1730f25 100644
--- a/app/controllers/auth/registrations_controller.rb
+++ b/app/controllers/auth/registrations_controller.rb
@@ -1,7 +1,6 @@
 # frozen_string_literal: true
 
 class Auth::RegistrationsController < Devise::RegistrationsController
-  include Devise::Controllers::Rememberable
   include RegistrationSpamConcern
 
   layout :determine_layout
@@ -30,8 +29,6 @@ class Auth::RegistrationsController < Devise::RegistrationsController
     super do |resource|
       if resource.saved_change_to_encrypted_password?
         resource.clear_other_sessions(current_session.session_id)
-        resource.forget_me!
-        remember_me(resource)
       end
     end
   end