Pam u2f for GDM about pam-u2f

[a-dma]

I have installed Fedora and done some testing.

The module works fine for me. I have added the rule to the end of gdm-password as stated before.
The only "problematic" behavior I have noticed is if you add the rule at the beginning of the file and no u2f device is plugged in when you attempt login. This is because the u2f module is constantly accessed and repeatedly returns an error failing to discover devices, but as soon as you plug a device in, the following request succedes and the module waits for a touch event (and a password afterwards).

I'm not sure at this point what could be, do you have any other custom modification to the system?
My advice here would be to install pamtester, enable debug mode on the u2f module and do some debugging. You can use pamtester like this

'' $ pamtester gdm-password adma authenticate ''

you should be able to see what's going wrong.

[a-dma]

What kind of failures are you experiencing?

I can get it up and running on Jessie and it seems to be working reliably.
I'm adding a rule at the end of gdm-password and both requisite and required seem to work.

[Spindel]

On fedora, you have to add it before the Password include stack ( as system-password is Requisite marked ) and it appears to lock me out when I try it in u2f => password order. ( I get three instant-failures )