systemd-cryptsetup@.service.8

SYSTEMD−CRYPTSETUP

NAME
SYNOPSIS
DESCRIPTION
CREDENTIALS
SEE ALSO
NOTES

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NAME

systemd-cryptsetup, systemd-cryptsetup@.service − Full disk decryption logic

SYNOPSIS

systemd−cryptsetup@.service

system−systemd\x2dcryptsetup.slice

DESCRIPTION

systemd−cryptsetup is used to set up (with attach) and tear down (with detach) access to an encrypted block device. It is primarily used via systemd−cryptsetup@.service during early boot, but may also be called manually. The positional arguments VOLUME, SOURCE−DEVICE, KEY−FILE, and CRYPTTAB−OPTIONS have the same meaning as the fields in crypttab(5).

systemd−cryptsetup@.service is a service responsible for providing access to encrypted block devices. It is instantiated for each device that requires decryption.

systemd−cryptsetup@.service instances are part of the system−systemd\x2dcryptsetup.slice slice, which is destroyed only very late in the shutdown procedure. This allows the encrypted devices to remain up until filesystems have been unmounted.

systemd−cryptsetup@.service will ask for hard disk passwords via the password agent logic [1] , in order to query the user for the password using the right mechanism at boot and during runtime.

At early boot and when the system manager configuration is reloaded, /etc/crypttab is translated into systemd−cryptsetup@.service units by systemd-cryptsetup-generator(8).

In order to unlock a volume a password or binary key is required. systemd−cryptsetup@.service tries to acquire a suitable password or binary key via the following mechanisms, tried in order:

1. If a key file is explicitly configured (via the third column in /etc/crypttab), a key read from it is used. If a PKCS#11 token, FIDO2 token or TPM2 device is configured (using the pkcs11−uri=, fido2−device=, tpm2−device= options) the key is decrypted before use.

2. If no key file is configured explicitly this way, a key file is automatically loaded from /etc/cryptsetup−keys.d/volume.key and /run/cryptsetup−keys.d/volume.key, if present. Here too, if a PKCS#11/FIDO2/TPM2 token/device is configured, any key found this way is decrypted before use.

3. If the try−empty−password option is specified then unlocking the volume with an empty password is attempted.

4. If the password−cache= option is set to “yes” or “read−only”, the kernel keyring is then checked for a suitable cached password from previous attempts.

5. Finally, the user is queried for a password, possibly multiple times, unless the headless option is set.

If no suitable key may be acquired via any of the mechanisms describes above, volume activation fails.

CREDENTIALS

systemd−cryptsetup supports the service credentials logic as implemented by ImportCredential=/LoadCredential=/SetCredential= (see systemd.exec(5) for details). The following credentials are used by “systemd−crypsetup@root.service” (generated by systemd−gpt−auto−generator) when passed in:

cryptsetup.passphrase

This credential specifies the passphrase of the LUKS volume.

Added in version 256.

cryptsetup.tpm2−pin

This credential specifies the TPM pin.

Added in version 256.

cryptsetup.fido2−pin

This credential specifies the FIDO2 token pin.

Added in version 256.

cryptsetup.pkcs11−pin

This credential specifies the PKCS11 token pin.

Added in version 256.

cryptsetup.luks2−pin

This credential specifies the pin requested by generic LUKS2 token modules.

Added in version 256.

SEE ALSO

systemd(1), systemd-cryptsetup-generator(8), crypttab(5), systemd-cryptenroll(1), cryptsetup(8), TPM2 PCR Measurements Made by systemd [2]

NOTES

https://systemd.io/PASSWORD_AGENTS/

https://systemd.io/TPM2_PCR_MEASUREMENTS

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