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NAME | SYNOPSIS | DESCRIPTION | LIMITATIONS | OPTIONS | EXIT STATUS | SEE ALSO | COLOPHON |
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SYSTEMD-CRYPTENROLL(1) systemd-cryptenroll SYSTEMD-CRYPTENROLL(1)
systemd-cryptenroll - Enroll PKCS#11, FIDO2, TPM2 token/devices
to LUKS2 encrypted volumes
systemd-cryptenroll [OPTIONS...] [DEVICE]
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.
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.
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.
On success, 0 is returned, a non-zero failure code otherwise.
systemd(1), systemd-cryptsetup@.service(8), crypttab(5),
cryptsetup(8), systemd-measure(1)
This page is part of the systemd (systemd system and service
manager) project. Information about the project can be found at
⟨http://www.freedesktop.org/wiki/Software/systemd⟩. If you have
a bug report for this manual page, see
⟨http://www.freedesktop.org/wiki/Software/systemd/#bugreports⟩.
This page was obtained from the project's upstream Git repository
⟨https://github.com/systemd/systemd.git⟩ on 2022-12-17. (At that
time, the date of the most recent commit that was found in the
repository was 2022-12-16.) If you discover any rendering
problems in this HTML version of the page, or you believe there
is a better or more up-to-date source for the page, or you have
corrections or improvements to the information in this COLOPHON
(which is not part of the original manual page), send a mail to
man-pages@man7.org
systemd 252 SYSTEMD-CRYPTENROLL(1)
Pages that refer to this page: systemd-creds(1), crypttab(5), repart.d(5), systemd.directives(7), systemd.index(7), systemd-cryptsetup-generator(8), systemd-cryptsetup@.service(8), systemd-repart(8)
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