Provided by: systemd_255.4-1ubuntu8.11_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.
TPM2 PCRs and policies
PCRs allow binding of the encryption of secrets to specific software versions and system state, so that
the enrolled key is only accessible (may be "unsealed") if specific trusted software and/or configuration
is used. Such bindings may be created with the option --tpm2-pcrs= described below.
Secrets may also be bound indirectly: a signed policy for a state of some combination of PCR values is
provided, and the secret is bound to the public part of the key used to sign this policy. This means that
the owner of a key can generate a sequence of signed policies, for specific software versions and system
states, and the secret can be decrypted as long as the machine state matches one of those policies. For
example, a vendor may provide such a policy for each kernel+initrd update, allowing users to encrypt
secrets so that they can be decrypted when running any kernel+initrd signed by the vendor. Such bindings
may be created with the options --tpm2-public-key=, --tpm2-public-key-pcrs=, --tpm2-signature= described
below.
See Linux TPM PCR Registry[1] for an authoritative list of PCRs and how they are updated. The table below
contains a quick reference, describing in particular the PCRs modified by systemd.
Table 1. Well-known PCR Definitions
┌─────┬─────────────────────┬──────────────────────────────┐
│ PCR │ name │ Explanation │
├─────┼─────────────────────┼──────────────────────────────┤
│ 0 │ platform-code │ Core system firmware │
│ │ │ executable code; changes on │
│ │ │ firmware updates │
├─────┼─────────────────────┼──────────────────────────────┤
│ 1 │ platform-config │ Core system firmware │
│ │ │ data/host platform │
│ │ │ configuration; typically │
│ │ │ contains serial and model │
│ │ │ numbers, changes on basic │
│ │ │ hardware/CPU/RAM │
│ │ │ replacements │
├─────┼─────────────────────┼──────────────────────────────┤
│ 2 │ external-code │ Extended or pluggable │
│ │ │ executable code; includes │
│ │ │ option ROMs on pluggable │
│ │ │ hardware │
├─────┼─────────────────────┼──────────────────────────────┤
│ 3 │ external-config │ Extended or pluggable │
│ │ │ firmware data; includes │
│ │ │ information about pluggable │
│ │ │ hardware │
├─────┼─────────────────────┼──────────────────────────────┤
│ 4 │ boot-loader-code │ Boot loader and additional │
│ │ │ drivers, PE binaries invoked │
│ │ │ by the boot loader; changes │
│ │ │ on boot loader updates. sd- │
│ │ │ stub(7) measures system │
│ │ │ extension images read from │
│ │ │ the ESP here too (see │
│ │ │ systemd-sysext(8)). │
├─────┼─────────────────────┼──────────────────────────────┤
│ 5 │ boot-loader-config │ GPT/Partition table; changes │
│ │ │ when the partitions are │
│ │ │ added, modified, or removed │
├─────┼─────────────────────┼──────────────────────────────┤
│ 7 │ secure-boot-policy │ Secure Boot state; changes │
│ │ │ when UEFI SecureBoot mode is │
│ │ │ enabled/disabled, or │
│ │ │ firmware certificates (PK, │
│ │ │ KEK, db, dbx, ...) changes. │
├─────┼─────────────────────┼──────────────────────────────┤
│ 9 │ kernel-initrd │ The Linux kernel measures │
│ │ │ all initrds it receives into │
│ │ │ this PCR. │
├─────┼─────────────────────┼──────────────────────────────┤
│ 10 │ ima │ The IMA project measures its │
│ │ │ runtime state into this PCR. │
├─────┼─────────────────────┼──────────────────────────────┤
│ 11 │ kernel-boot │ systemd-stub(7) measures the │
│ │ │ ELF kernel image, embedded │
│ │ │ initrd and other payload of │
│ │ │ the PE image it is placed in │
│ │ │ into this PCR. systemd- │
│ │ │ pcrphase.service(8) measures │
│ │ │ boot phase strings into this │
│ │ │ PCR at various milestones of │
│ │ │ the boot process. │
├─────┼─────────────────────┼──────────────────────────────┤
│ 12 │ kernel-config │ systemd-boot(7) measures the │
│ │ │ 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. │
├─────┼─────────────────────┼──────────────────────────────┤
│ 13 │ sysexts │ systemd-stub(7) measures any │
│ │ │ systemd-sysext(8) images it │
│ │ │ passes to the booted kernel │
│ │ │ into this PCR. │
├─────┼─────────────────────┼──────────────────────────────┤
│ 14 │ shim-policy │ The shim project measures │
│ │ │ its "MOK" certificates and │
│ │ │ hashes into this PCR. │
├─────┼─────────────────────┼──────────────────────────────┤
│ 15 │ system-identity │ systemd-cryptsetup(8) │
│ │ │ optionally measures the │
│ │ │ volume key of activated LUKS │
│ │ │ volumes into this PCR. │
│ │ │ systemd- │
│ │ │ pcrmachine.service(8) │
│ │ │ measures the machine-id(5) │
│ │ │ into this PCR. systemd- │
│ │ │ pcrfs@.service(8) measures │
│ │ │ mount points, file system │
│ │ │ UUIDs, labels, partition │
│ │ │ UUIDs of the root and /var/ │
│ │ │ filesystems into this PCR. │
├─────┼─────────────────────┼──────────────────────────────┤
│ 16 │ debug │ Debug │
├─────┼─────────────────────┼──────────────────────────────┤
│ 23 │ application-support │ Application Support │
└─────┴─────────────────────┴──────────────────────────────┘
In general, encrypted volumes would be bound to some combination of PCRs 7, 11, and 14 (if shim/MOK is
used). In order to allow firmware and OS version updates, it is typically not advisable to use PCRs such
as 0 and 2, since the program code they cover should already be covered indirectly through the
certificates measured into PCR 7. Validation through certificates hashes 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 signatures should remain unchanged. See the Linux TPM PCR
Registry[1] for more discussion.
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, a recovery key or a FIDO2 token. It's currently not supported to
unlock a device with a TPM2/PKCS#11 key in order to enroll a new TPM2/PKCS#11 key. Thus, if in future key
roll-over is desired it's generally recommended to ensure a passphrase, a recovery key or a FIDO2 token
is always enrolled.
Also note that support for enrolling multiple FIDO2 tokens is currently limited. When multiple FIDO2
tokens are enrolled, systemd-cryptseup will perform pre-flight requests to attempt to identify which of
the enrolled tokens are currently plugged in. However, this is not possible for FIDO2 tokens with user
verification (UV, usually via biometrics), in which case it will fall back to attempting each enrolled
token one by one. This will result in multiple prompts for PIN and user verification. This limitation
does not apply to PKCS#11 tokens.
COMPATIBILITY
Security technology both in systemd and in the general industry constantly evolves. In order to provide
best security guarantees, the way TPM2, FIDO2, PKCS#11 devices are enrolled is regularly updated in newer
versions of systemd. Whenever this happens the following compatibility guarantees are given:
• Old enrollments continue to be supported and may be unlocked with newer versions of systemd-
cryptsetup@.service(8).
• The opposite is not guaranteed however: it might not be possible to unlock volumes with enrollments
done with a newer version of systemd-cryptenroll with an older version of systemd-cryptsetup.
That said, it is generally recommended to use matching versions of systemd-cryptenroll and
systemd-cryptsetup, since this is best tested and supported.
It might be advisable to re-enroll existing enrollments to take benefit of newer security features, as
they are added to systemd.
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.
Added in version 248.
--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.
Added in version 248.
--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.
Added in version 252.
--unlock-fido2-device=PATH
Use a FIDO2 device instead of a password/passphrase read from stdin to unlock the volume. 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). This automatic discovery is unsupported if
--fido2-device= option is also specified.
Added in version 253.
--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.
Added in version 248.
--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.
Added in version 251.
--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). This automatic discovery is unsupported if
--unlock-fido2-device= option is also specified. 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.
Added in version 248.
--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.)
Added in version 249.
--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.)
Added in version 249.
--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.)
Added in version 249.
--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.
Added in version 248.
--tpm2-device-key=PATH
Enroll a TPM2 security chip using its public key. Expects a path referring to the TPM2 public key in
TPM2B_PUBLIC format. This cannot be used with --tpm2-device=, as it performs the same operation, but
without connecting to the TPM2 security chip; instead the enrollment is calculated using the provided
TPM2 key. This is useful in situations where the TPM2 security chip is not available at the time of
enrollment.
The key, in most cases, should be the Storage Root Key (SRK) from a local TPM2 security chip. If a
key from a different handle (not the SRK) is used, you must specify its handle index using
--tpm2-seal-key-handle=.
The systemd-tpm2-setup.service(8) service writes the SRK to
/run/systemd/tpm2-srk-public-key.tpm2b_public automatically during boot, in the correct format.
Alternatively, you may use systemd-analyze srk to retrieve the SRK from the TPM2 security chip
explicitly. See systemd-analyze(1) for details. Example:
systemd-analyze srk > srk.tpm2b_public
Added in version 255.
--tpm2-seal-key-handle=HANDLE
Configures which parent key to use for sealing, using the TPM handle (index) of the key. This is used
to "seal" (encrypt) a secret and must be used later to "unseal" (decrypt) the secret. Expects a
hexadecimal 32bit integer, optionally prefixed with "0x". Allowable values are any handle index in
the persistent ("0x81000000"-"0x81ffffff") or transient ("0x80000000"-"0x80ffffff") ranges. Since
transient handles are lost after a TPM reset, and may be flushed during TPM context switching, they
should not be used except for very specific use cases, e.g. testing.
The default is the Storage Root Key (SRK) handle index "0x81000001". A value of 0 will use the
default. For the SRK handle, a new key will be created and stored in the TPM if one does not already
exist; for any other handle, the key must already exist in the TPM at the specified handle index.
This should not be changed unless you know what you are doing.
Added in version 255.
--tpm2-pcrs= [PCR...]
Configures the TPM2 PCRs (Platform Configuration Registers) to bind to when enrollment is requested
via --tpm2-device=. Takes a list of PCR entries, where each entry starts with a name or numeric index
in the range 0...23, optionally followed by ":" and a hash algorithm name (specifying the PCR bank),
optionally followed by "=" and a hash digest value. Multiple PCR entries are separated by "+". If not
specified, the default is to use PCR 7 only. If an empty string is specified, binds the enrollment to
no PCRs at all. See the table above for a list of available PCRs.
Example: --tpm2-pcrs=boot-loader-code+platform-config+boot-loader-config specifies that PCR registers
4, 1, and 5 should be used.
Example: --tpm2-pcrs=7:sha256 specifies that PCR register 7 from the SHA256 bank should be used.
Example: --tpm2-pcrs=4:sha1=3a3f780f11a4b49969fcaa80cd6e3957c33b2275 specifies that PCR register 4
from the SHA1 bank should be used, and a hash digest value of
3a3f780f11a4b49969fcaa80cd6e3957c33b2275 will be used instead of reading the current PCR value.
Added in version 248.
--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.
Added in version 251.
--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. Like with --tpm2-pcrs=, names defined in the table above can also be used to specify the
registers, for instance --tpm2-public-key-pcrs=boot-loader-code+system-identity.
The --tpm2-signature= option takes a path to a TPM2 PCR signature file as generated by the systemd-
measure(1) tool. If 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.
Added in version 252.
--tpm2-pcrlock= [PATH]
Configures a TPM2 pcrlock policy to bind encryption to. Expects a path to a pcrlock policy file as
generated by the systemd-pcrlock(1) tool. If a TPM2 device is enrolled and this option is not used
but a file pcrlock.json is found in /run/systemd/ or /var/lib/systemd/ it is automatically used.
Assign an empty string to turn this behaviour off.
Added in version 255.
--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
Added in version 248.
-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.
EXAMPLES
crypttab(5) and systemd-measure(1) contain various examples employing systemd-cryptenroll.
SEE ALSO
systemd(1), systemd-cryptsetup@.service(8), crypttab(5), cryptsetup(8), systemd-measure(1)
NOTES
1. Linux TPM PCR Registry
https://uapi-group.org/specifications/specs/linux_tpm_pcr_registry/
systemd 255 SYSTEMD-CRYPTENROLL(1)