OTP(e.g. OPIE or FreeAuth) - authentication on FW

[john99]

Hello,

I would like to use OTP authentication(like OPIE or FreeAuth) in order to be able a access (from remote workstations) different applications, e.g. a webmailer like Zimbra/ZCS (behind the FW).

I heard that - if the application does not use PAM-calls - it's not easy to setup such an environment :-(

Due to security reasons we would prefer to have this authentication-process done directly on the firewall
instead of using an authentication portal like capitve.

Questions:
Is there a way to integrate OPT-authentication directly on pfSense, or are there better approaches?

Thank you very much in advance for every feedback!

John