pam_systemd_loadkey - Man Page

pam_systemd_loadkey.so

pam_systemd_loadkey reads a NUL-separated password list from the kernel keyring, and sets the last password in the list as the PAM authtok, which can be used by e.g. pam_get_authtok(3).

The password list is supposed to be stored in the "user" keyring of the root user, by an earlier call to systemd-ask-password(1) with --keyname=. You can pass the keyname to pam_systemd_loadkey via the keyname= option.

The following options are understood:

keyname=

Takes a string argument which sets the keyname to read. The default is "cryptsetup". During boot, systemd-cryptsetup@.service(8) stores a passphrase or PIN in the keyring. The LUKS2 volume key can also be used, via the link-volume-key option in crypttab(5).

Table 1.  Possible values for keyname.

Value	Description
cryptsetup	Passphrase or recovery key
fido2-pin	Security token PIN
luks2-pin	LUKS2 token PIN
tpm2-pin	TPM2 PIN

Added in version 255.

debug

The module will log debugging information as it operates.

Added in version 255.

This module is intended to be used when you use LUKS with a passphrase, enable autologin in the display manager, and want to unlock Gnome Keyring / KDE KWallet automatically. So in total, you only enter one password during boot.

You need to set the password of your Gnome Keyring/KWallet to the same as your LUKS passphrase. Then add the following lines to your display manager's PAM config under /etc/pam.d/ (e.g. sddm-autologin):

-auth       optional    pam_systemd_loadkey.so
-auth       optional    pam_gnome_keyring.so
-session    optional    pam_gnome_keyring.so auto_start
-session    optional    pam_kwallet5.so auto_start

And add the following lines to your display manager's systemd service file, so it can access root's keyring:

[Service]
KeyringMode=inherit

In this setup, early during the boot process, systemd-cryptsetup@.service(8) will ask for the passphrase and store it in the kernel keyring with the keyname "cryptsetup". Then when the display manager does the autologin, pam_systemd_loadkey will read the passphrase from the kernel keyring, set it as the PAM authtok, and then pam_gnome_keyring and pam_kwallet5 will unlock with the same passphrase.

systemd.directives(7), systemd.index(7).