OpenVPN auth with Fido/U2F via pam-u2f ?
Has anyone tried out the Yubico pam module for the Fido U2F protocol?
The source code for the module is here: https://github.com/Yubico/pam-u2f
Hints on around the web suggest that Yubico will come out with a Bluetooth-enabled version of their 4096-bit Yubikey-4 which would be quite interesting as something that would work both with desktop and mobile devices.
Only Chrome has it built in as yet but there is a user-contributed plugin for Firefox.