Redmine

Hello,

I am using a bitnami stack for redmine (version 2.4) and would like to add multi factor authentication to all my users. I have looked at plugins like 2FA (https://github.com/centosadmin/redmine_2fa). But for this to work we need redmine 3.4 or later. There's an issue with this as some of my current plugins are not compatible with 3.4. Are there any other methods to add Mullti Factor Authentication on version 2.4?