Provided by: systemd_252.5-2ubuntu3_amd64 
NAME
systemd-cryptenroll - Enroll PKCS#11, FIDO2, TPM2 token/devices to LUKS2 encrypted volumes
SYNOPSIS
systemd-cryptenroll [OPTIONS...] [DEVICE]
DESCRIPTION
systemd-cryptenroll is a tool for enrolling hardware security tokens and devices into a
LUKS2 encrypted volume, which may then be used to unlock the volume during boot.
Specifically, it supports tokens and credentials of the following kind to be enrolled:
1. PKCS#11 security tokens and smartcards that may carry an RSA key pair (e.g. various
YubiKeys)
2. FIDO2 security tokens that implement the "hmac-secret" extension (most FIDO2 keys,
including YubiKeys)
3. TPM2 security devices
4. Regular passphrases
5. Recovery keys. These are similar to regular passphrases, however are randomly
generated on the computer and thus generally have higher entropy than user-chosen
passphrases. Their character set has been designed to ensure they are easy to type in,
while having high entropy. They may also be scanned off screen using QR codes.
Recovery keys may be used for unlocking LUKS2 volumes wherever passphrases are
accepted. They are intended to be used in combination with an enrolled hardware
security token, as a recovery option when the token is lost.
In addition, the tool may be used to enumerate currently enrolled security tokens and wipe
a subset of them. The latter may be combined with the enrollment operation of a new
security token, in order to update or replace enrollments.
The tool supports only LUKS2 volumes, as it stores token meta-information in the LUKS2
JSON token area, which is not available in other encryption formats.
LIMITATIONS
Note that currently when enrolling a new key of one of the five supported types listed
above, it is required to first provide a passphrase or recovery key (i.e. one of the
latter two key types). For example, it's currently not possible to unlock a device with a
FIDO2 key in order to enroll a new FIDO2 key. Instead, in order to enroll a new FIDO2 key,
it is necessary to provide an already enrolled regular passphrase or recovery key. Thus,
if in future key roll-over is desired it's generally recommended to combine TPM2, FIDO2,
PKCS#11 key enrollment with enrolling a regular passphrase or recovery key.
Also note that support for enrolling multiple FIDO2 tokens is currently not too useful, as
while unlocking systemd-cryptsetup cannot identify which token is currently plugged in and
thus does not know which authentication request to send to the device. This limitation
does not apply to tokens enrolled via PKCS#11 — because tokens of this type may be
identified immediately, before authentication.
OPTIONS
The following options are understood:
--password
Enroll a regular password/passphrase. This command is mostly equivalent to cryptsetup
luksAddKey, however may be combined with --wipe-slot= in one call, see below.
--recovery-key
Enroll a recovery key. Recovery keys are mostly identical to passphrases, but are
computer-generated instead of being chosen by a human, and thus have a guaranteed high
entropy. The key uses a character set that is easy to type in, and may be scanned off
screen via a QR code.
--unlock-key-file=PATH
Use a file instead of a password/passphrase read from stdin to unlock the volume.
Expects the PATH to the file containing your key to unlock the volume. Currently there
is nothing like --key-file-offset= or --key-file-size= so this file has to only
contain the full key.
--pkcs11-token-uri=URI
Enroll a PKCS#11 security token or smartcard (e.g. a YubiKey). Expects a PKCS#11
smartcard URI referring to the token. Alternatively the special value "auto" may be
specified, in order to automatically determine the URI of a currently plugged in
security token (of which there must be exactly one). The special value "list" may be
used to enumerate all suitable PKCS#11 tokens currently plugged in. The security token
must contain an RSA key pair which is used to encrypt the randomly generated key that
is used to unlock the LUKS2 volume. The encrypted key is then stored in the LUKS2 JSON
token header area.
In order to unlock a LUKS2 volume with an enrolled PKCS#11 security token, specify the
pkcs11-uri= option in the respective /etc/crypttab line:
myvolume /dev/sda1 - pkcs11-uri=auto
See crypttab(5) for a more comprehensive example of a systemd-cryptenroll invocation
and its matching /etc/crypttab line.
--fido2-credential-algorithm=STRING
Specify COSE algorithm used in credential generation. The default value is "es256".
Supported values are "es256", "rs256" and "eddsa".
"es256" denotes ECDSA over NIST P-256 with SHA-256. "rs256" denotes 2048-bit RSA with
PKCS#1.5 padding and SHA-256. "eddsa" denotes EDDSA over Curve25519 with SHA-512.
Note that your authenticator may not support some algorithms.
--fido2-device=PATH
Enroll a FIDO2 security token that implements the "hmac-secret" extension (e.g. a
YubiKey). Expects a hidraw device referring to the FIDO2 device (e.g. /dev/hidraw1).
Alternatively the special value "auto" may be specified, in order to automatically
determine the device node of a currently plugged in security token (of which there
must be exactly one). The special value "list" may be used to enumerate all suitable
FIDO2 tokens currently plugged in. Note that many hardware security tokens that
implement FIDO2 also implement the older PKCS#11 standard. Typically FIDO2 is
preferable, given it's simpler to use and more modern.
In order to unlock a LUKS2 volume with an enrolled FIDO2 security token, specify the
fido2-device= option in the respective /etc/crypttab line:
myvolume /dev/sda1 - fido2-device=auto
See crypttab(5) for a more comprehensive example of a systemd-cryptenroll invocation
and its matching /etc/crypttab line.
--fido2-with-client-pin=BOOL
When enrolling a FIDO2 security token, controls whether to require the user to enter a
PIN when unlocking the volume (the FIDO2 "clientPin" feature). Defaults to "yes".
(Note: this setting is without effect if the security token does not support the
"clientPin" feature at all, or does not allow enabling or disabling it.)
--fido2-with-user-presence=BOOL
When enrolling a FIDO2 security token, controls whether to require the user to verify
presence (tap the token, the FIDO2 "up" feature) when unlocking the volume. Defaults
to "yes". (Note: this setting is without effect if the security token does not support
the "up" feature at all, or does not allow enabling or disabling it.)
--fido2-with-user-verification=BOOL
When enrolling a FIDO2 security token, controls whether to require user verification
when unlocking the volume (the FIDO2 "uv" feature). Defaults to "no". (Note: this
setting is without effect if the security token does not support the "uv" feature at
all, or does not allow enabling or disabling it.)
--tpm2-device=PATH
Enroll a TPM2 security chip. Expects a device node path referring to the TPM2 chip
(e.g. /dev/tpmrm0). Alternatively the special value "auto" may be specified, in order
to automatically determine the device node of a currently discovered TPM2 device (of
which there must be exactly one). The special value "list" may be used to enumerate
all suitable TPM2 devices currently discovered.
In order to unlock a LUKS2 volume with an enrolled TPM2 security chip, specify the
tpm2-device= option in the respective /etc/crypttab line:
myvolume /dev/sda1 - tpm2-device=auto
See crypttab(5) for a more comprehensive example of a systemd-cryptenroll invocation
and its matching /etc/crypttab line.
Use --tpm2-pcrs= (see below) to configure which TPM2 PCR indexes to bind the
enrollment to.
--tpm2-pcrs= [PCR...]
Configures the TPM2 PCRs (Platform Configuration Registers) to bind the enrollment
requested via --tpm2-device= to. Takes a "+" separated list of numeric PCR indexes in
the range 0...23. If not used, defaults to PCR 7 only. If an empty string is
specified, binds the enrollment to no PCRs at all. PCRs allow binding the enrollment
to specific software versions and system state, so that the enrolled unlocking key is
only accessible (may be "unsealed") if specific trusted software and/or configuration
is used.
Table 1. Well-known PCR Definitions
┌────┬──────────────────────────────────┐
│PCR │ Explanation │
├────┼──────────────────────────────────┤
│0 │ Core system firmware executable │
│ │ code; changes on firmware │
│ │ updates │
├────┼──────────────────────────────────┤
│1 │ Core system firmware data/host │
│ │ platform configuration; │
│ │ typically contains serial and │
│ │ model numbers, changes on basic │
│ │ hardware/CPU/RAM replacements │
├────┼──────────────────────────────────┤
│2 │ Extended or pluggable executable │
│ │ code; includes option ROMs on │
│ │ pluggable hardware │
├────┼──────────────────────────────────┤
│3 │ Extended or pluggable firmware │
│ │ data; includes information about │
│ │ pluggable hardware │
├────┼──────────────────────────────────┤
│4 │ Boot loader and additional │
│ │ drivers; changes on boot loader │
│ │ updates. The shim project will │
│ │ measure the PE binary it chain │
│ │ loads into this PCR. If the │
│ │ Linux kernel is invoked as UEFI │
│ │ PE binary, it is measured here, │
│ │ too. sd-stub(7) measures system │
│ │ extension images read from the │
│ │ ESP here too (see systemd- │
│ │ sysext(8)). │
├────┼──────────────────────────────────┤
│5 │ GPT/Partition table; changes │
│ │ when the partitions are added, │
│ │ modified or removed │
├────┼──────────────────────────────────┤
│6 │ Power state events; changes on │
│ │ system suspend/sleep │
├────┼──────────────────────────────────┤
│7 │ Secure boot state; changes when │
│ │ UEFI SecureBoot mode is │
│ │ enabled/disabled, or firmware │
│ │ certificates (PK, KEK, db, dbx, │
│ │ ...) changes. The shim project │
│ │ will measure most of its │
│ │ (non-MOK) certificates and SBAT │
│ │ data into this PCR. │
├────┼──────────────────────────────────┤
│9 │ The Linux kernel measures all │
│ │ initrds it receives into this │
│ │ PCR. │
├────┼──────────────────────────────────┤
│10 │ The IMA project measures its │
│ │ runtime state into this PCR. │
├────┼──────────────────────────────────┤
│11 │ systemd-stub(7) measures the ELF │
│ │ kernel image, embedded initrd │
│ │ and other payload of the PE │
│ │ image it is placed in into this │
│ │ PCR. Unlike PCR 4 (where the │
│ │ same data should be measured │
│ │ into), this PCR value should be │
│ │ easy to pre-calculate, as this │
│ │ only contains static parts of │
│ │ the PE binary. Use this PCR to │
│ │ bind TPM policies to a specific │
│ │ kernel image, possibly with an │
│ │ embedded initrd. systemd- │
│ │ pcrphase.service(8) measures │
│ │ boot phase strings into this PCR │
│ │ at various milestones of the │
│ │ boot process. │
├────┼──────────────────────────────────┤
│12 │ systemd-boot(7) measures any │
│ │ specified kernel command line │
│ │ into this PCR. systemd-stub(7) │
│ │ measures any manually specified │
│ │ kernel command line (i.e. a │
│ │ kernel command line that │
│ │ overrides the one embedded in │
│ │ the unified PE image) and loaded │
│ │ credentials into this PCR. (Note │
│ │ that if systemd-boot and │
│ │ systemd-stub are used in │
│ │ combination the command line │
│ │ might be measured twice!) │
├────┼──────────────────────────────────┤
│13 │ systemd-stub(7) measures any │
│ │ systemd-sysext(8) images it │
│ │ loads and passed to the booted │
│ │ kernel into this PCR. │
├────┼──────────────────────────────────┤
│14 │ The shim project measures its │
│ │ "MOK" certificates and hashes │
│ │ into this PCR. │
└────┴──────────────────────────────────┘
For most applications it should be sufficient to bind against PCR 7 (and possibly PCR
14, if shim/MOK is desired), as this includes measurements of the trusted certificates
(and possibly hashes) that are used to validate all components of the boot process up
to and including the OS kernel. In order to simplify firmware and OS version updates
it's typically not advisable to include PCRs such as 0 and 2 in the binding of the
enrollment, since the program code they cover should already be protected indirectly
through the certificates measured into PCR 7. Validation through these certificates is
typically preferable over validation through direct measurements as it is less brittle
in context of OS/firmware updates: the measurements will change on every update, but
code signatures likely will validate against pre-existing certificates.
--tpm2-with-pin=BOOL
When enrolling a TPM2 device, controls whether to require the user to enter a PIN when
unlocking the volume in addition to PCR binding, based on TPM2 policy authentication.
Defaults to "no". Despite being called PIN, any character can be used, not just
numbers.
Note that incorrect PIN entry when unlocking increments the TPM dictionary attack
lockout mechanism, and may lock out users for a prolonged time, depending on its
configuration. The lockout mechanism is a global property of the TPM,
systemd-cryptenroll does not control or configure the lockout mechanism. You may use
tpm2-tss tools to inspect or configure the dictionary attack lockout, with
tpm2_getcap(1) and tpm2_dictionarylockout(1) commands, respectively.
--tpm2-public-key= [PATH], --tpm2-public-key-pcrs= [PCR...], --tpm2-signature= [PATH]
Configures a TPM2 signed PCR policy to bind encryption to. The --tpm2-public-key=
option accepts a path to a PEM encoded RSA public key, to bind the encryption to. If
this is not specified explicitly, but a file tpm2-pcr-public-key.pem exists in one of
the directories /etc/systemd/, /run/systemd/, /usr/lib/systemd/ (searched in this
order), it is automatically used. The --tpm2-public-key-pcrs= option takes a list of
TPM2 PCR indexes to bind to (same syntax as --tpm2-pcrs= described above). If not
specified defaults to 11 (i.e. this binds the policy to any unified kernel image for
which a PCR signature can be provided).
Note the difference between --tpm2-pcrs= and --tpm2-public-key-pcrs=: the former binds
decryption to the current, specific PCR values; the latter binds decryption to any set
of PCR values for which a signature by the specified public key can be provided. The
latter is hence more useful in scenarios where software updates shell be possible
without losing access to all previously encrypted LUKS2 volumes.
The --tpm2-signature= option takes a path to a TPM2 PCR signature file as generated by
the systemd-measure(1) tool. If this this is not specified explicitly a suitable
signature file tpm2-pcr-signature.json is searched for in /etc/systemd/,
/run/systemd/, /usr/lib/systemd/ (in this order) and used. If a signature file is
specified or found it is used to verify if the volume can be unlocked with it given
the current PCR state, before the new slot is written to disk. This is intended as
safety net to ensure that access to a volume is not lost if a public key is enrolled
for which no valid signature for the current PCR state is available. If the supplied
signature does not unlock the current PCR state and public key combination, no slot is
enrolled and the operation will fail. If no signature file is specified or found no
such safety verification is done.
--wipe-slot= [SLOT...]
Wipes one or more LUKS2 key slots. Takes a comma separated list of numeric slot
indexes, or the special strings "all" (for wiping all key slots), "empty" (for wiping
all key slots that are unlocked by an empty passphrase), "password" (for wiping all
key slots that are unlocked by a traditional passphrase), "recovery" (for wiping all
key slots that are unlocked by a recovery key), "pkcs11" (for wiping all key slots
that are unlocked by a PKCS#11 token), "fido2" (for wiping all key slots that are
unlocked by a FIDO2 token), "tpm2" (for wiping all key slots that are unlocked by a
TPM2 chip), or any combination of these strings or numeric indexes, in which case all
slots matching either are wiped. As safety precaution an operation that wipes all
slots without exception (so that the volume cannot be unlocked at all anymore, unless
the volume key is known) is refused.
This switch may be used alone, in which case only the requested wipe operation is
executed. It may also be used in combination with any of the enrollment options listed
above, in which case the enrollment is completed first, and only when successful the
wipe operation executed — and the newly added slot is always excluded from the wiping.
Combining enrollment and slot wiping may thus be used to update existing enrollments:
systemd-cryptenroll /dev/sda1 --wipe-slot=tpm2 --tpm2-device=auto
The above command will enroll the TPM2 chip, and then wipe all previously created TPM2
enrollments on the LUKS2 volume, leaving only the newly created one. Combining wiping
and enrollment may also be used to replace enrollments of different types, for example
for changing from a PKCS#11 enrollment to a FIDO2 one:
systemd-cryptenroll /dev/sda1 --wipe-slot=pkcs11 --fido2-device=auto
Or for replacing an enrolled empty password by TPM2:
systemd-cryptenroll /dev/sda1 --wipe-slot=empty --tpm2-device=auto
-h, --help
Print a short help text and exit.
--version
Print a short version string and exit.
EXIT STATUS
On success, 0 is returned, a non-zero failure code otherwise.
SEE ALSO
systemd(1), systemd-cryptsetup@.service(8), crypttab(5), cryptsetup(8), systemd-measure(1)