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I have enabled U2F device authentication for PAM on my Ubuntu 20.04. I have used this approach https://support.yubico.com/hc/en-us/articles/360016649099-Ubuntu-Linux-Login-Guide-U2F and put configuration into "/etc/pam.d/common-auth". Everything works as expected so I can log in via password AND U2F device touch.

Now I would like to avoid typing password once I am already logged into my account. (I always lock my computer when I leave it and take U2F token with me.)

For sudo I have added into "/etc/pam.d/sudo" line (above line @include common-auth):

auth sufficient pam_u2f.so authfile=/etc/u2f_mappings cue

After that change, I can confirm sudo just by pressing U2F button. Great.

Is there a way how to achieve the same with system dialogs asking for password? I mean this dialog that appears when I try to install package via Ubuntu Software:

I mean this

System should keep asking for password + U2F touch during log in.

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    I am unable to give you the verified answer, but maybe a hint that will help you is that these prompts are probably controlled by PolicyKit (en.wikipedia.org/wiki/Polkit), so the file /etc/pam.d/polkit-1 is probably the place to look for. I don't know anything more.
    – raj
    Feb 8 at 16:02
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I accidentally figured this out from your article, and from @raj's comment! Open up /etc/pam.d/polkit-1. After the @include's, add this line:

session required pam_u2f.so authfile=/etc/u2f_mappings cue

Thank you for your wonderful article! I'm using my generic U2F key for everything now.

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  • You're welcome. This setting does not work for me. It still requires password. I already had U2F confirmation in my dialogues when I added "required" line into /etc/pam.d/common-auth as my article suggests kubos.cz/2021/01/30/u2f-login-ubuntu May 4 at 19:25
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It was basically simple. Based on raj's answer I put:

auth sufficient pam_u2f.so authfile=/etc/u2f_mappings cue

In front of "@include" section of /etc/pam.d/polkit-1. And now I am required to enter password only on lock/login screen. Once I am logged in, I only press button on donge.

This topic is complex. Please read https://www.kubos.cz/2021/01/30/u2f-login-ubuntu or similar article before you start experimens!

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