pam_usb - weakish/cheat GitHub Wiki

As root:

apt-get install pamusb-tools libpam-usb
pamusb-conf --add-device my-usb-stick
pamusb-conf --add-user your-user-name

Make sure /etc/pam.d/common-auth contains:

auth    sufficient      pam_usb.so

(The default setting on Debian.)