Arch Linux

eearcher

Member

Registered: 2021-01-08

Posts: 21

[SOLVED] Fingerprint Authentication with GDM and fprint not working

I have a Thinkpad P14s with an integrated fingerprint reader. I'd like to use it to login in via GDM.
I followed the Arch Wiki's instructions for setting up fprint.
As it is stated there, I skipped the "Login Configuration" step, because I use GDM.

In the terminal, I can use

fprintd-enroll

to enroll my fingerprint. This seems to work fine (no error message).
I can also use

fprintd-verify

to verify if my fingerprint was saved correctly. It matches every time it should.
Since I installed fprintd, the login screen prompts "(or swipe finger)", so obviously it detected it in some way.

But now the problem:
When I use the fingerprint sensor during login, nothing happens. I can try it as many times as I want, nothing changes.
When I try

fprintd-verify

again after reboot, it says

Using device /net/reactivated/Fprint/Device/0
failed to claim device: GDBus.Error:net.reactivated.Fprint.Error.AlreadyInUse: Device was already claimed

So I would say that there are some conflicting services who'd like to access the fingerprint reader. But how can I investigate this?

I tried

journalctl -b | grep fprintd

and got

Jan 08 22:03:44 thinkpad dbus-daemon[320]: [system] Activating via systemd: service name='net.reactivated.Fprint' unit='fprintd.service' requested by ':1.20' (uid=120 pid=652 comm="/usr/bin/gnome-shell ")
Jan 08 22:03:44 thinkpad fprintd[859]: Device responded with error: 789 retry: 1
Jan 08 22:03:44 thinkpad audit[1]: SERVICE_START pid=1 uid=0 auid=4294967295 ses=4294967295 msg='unit=fprintd comm="systemd" exe="/usr/lib/systemd/systemd" hostname=? addr=? terminal=? res=success'

What is "error: 789"? Where can I find out?

GDM version is "gdm 3.38.2.1-1"
fprintd version is "1.90.8-1"
uname -r gives "5.10.5-arch1-1"

Thanks in advance.
Cheers, eearcher

Last edited by eearcher (2021-01-09 15:31:57)

icar

Member

From: Catalunya

Registered: 2020-07-31

Posts: 456

Re: [SOLVED] Fingerprint Authentication with GDM and fprint not working

Assuming you use Gnome since you are using GDM.

There is an option to enroll your fingerprint in the Gnome Settings. I would delete the one you created through the terminal and give that tool a shot. It's under your account management page.

eearcher

Member

Registered: 2021-01-08

Posts: 21

Re: [SOLVED] Fingerprint Authentication with GDM and fprint not working

Thanks for your reply.

So I reverted the config changes I made and found the entry you mentioned in Gnome Settings.
I activated fingerprint login there and saw that my fingerprint from before is saved.

My problem still persists, but it seems to me like there is a permission problem. Gnome Settings says "Some Settings must be unlocked before they can be changed".
But when I do this, it will be locked again when I reboot. (Fingerprint reader: exact same problem, can't log in and fprintd states that device is already claimed).

Any ideas what could cause this?

Cheers eearcher

Last edited by eearcher (2021-01-09 15:31:32)

eearcher

Member

Registered: 2021-01-08

Posts: 21

Re: [SOLVED] Fingerprint Authentication with GDM and fprint not working

Ok, I think I got it.

According to this issue, this is a problem with the BIOS.
There is something called "Predesktop Authentication", and as far as I understand it, this allows to use the fingerprint reader before boot. The problem is, that the device is therefore claimed by the BIOS first (this is where the "device is already claimed" error comes from, I guess) and meant to be handed over to Windows (!). So if you're not using Windows, but want to use the fingerprint reader, you need to:

• Disable "Predesktop Authentication" in BIOS (Security -> Fingerprint)

• Reset Fingerprint Data in BIOS (Security -> Fingerprint)

After doing this the authentication works as expected. Currently I still get the ("Settings need to be unlocked" message in Gnome Settings, but I really don't care about this right now, as long as it works). I also added the entry in /etc/pam.d/system-local-login back in, as described by the Arch Wiki (link in first post).

Marking this as solved.

Cheers, eearcher

archerious

Member

Registered: 2017-04-16

Posts: 2

Re: [SOLVED] Fingerprint Authentication with GDM and fprint not working

Ok, I think I got it.

According to this issue, this is a problem with the BIOS.
There is something called "Predesktop Authentication", and as far as I understand it, this allows to use the fingerprint reader before boot. The problem is, that the device is therefore claimed by the BIOS first (this is where the "device is already claimed" error comes from, I guess) and meant to be handed over to Windows (!). So if you're not using Windows, but want to use the fingerprint reader, you need to:

• Disable "Predesktop Authentication" in BIOS (Security -> Fingerprint)

• Reset Fingerprint Data in BIOS (Security -> Fingerprint)

After doing this the authentication works as expected. Currently I still get the ("Settings need to be unlocked" message in Gnome Settings, but I really don't care about this right now, as long as it works). I also added the entry in /etc/pam.d/system-local-login back in, as described by the Arch Wiki (link in first post).

Marking this as solved.

Cheers, eearcher

Thank you, that resolved it for me too.

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