Ubuntu Manpage: systemd-pcrlock, systemd-pcrlock-file-system.service, systemd-pcrlock-firmware-

Provided by: systemd_256.5-2ubuntu3.1_amd64

NAME

       systemd-pcrlock, systemd-pcrlock-file-system.service, systemd-pcrlock-firmware-
       code.service, systemd-pcrlock-firmware-config.service, systemd-pcrlock-machine-id.service,
       systemd-pcrlock-make-policy.service, systemd-pcrlock-secureboot-authority.service,
       systemd-pcrlock-secureboot-policy.service - Analyze and predict TPM2 PCR states and
       generate an access policy from the prediction

SYNOPSIS

       /usr/lib/systemd/systemd-pcrlock [OPTIONS...]

DESCRIPTION

Note: this command is experimental for now. While it is likely to become a regular
component of systemd, it might still change in behaviour and interface.

systemd-pcrlock is a tool that may be used to analyze and predict TPM2 PCR measurements,
and generate TPM2 access policies from the prediction which it stores in a TPM2 NV index
(i.e. in the TPM2 non-volatile memory). This may then be used to restrict access to TPM2
objects (such as disk encryption keys) to system boot-ups in which only specific, trusted
components are used.

systemd-pcrlock uses as input for its analysis and prediction:

• The UEFI firmware TPM2 event log (i.e.
/sys/kernel/security/tpm0/binary_bios_measurements) of the current boot.

• The userspace TPM2 event log (i.e. /run/log/systemd/tpm2-measure.log) of the current
boot.

• The current PCR state of the TPM2 chip.

• Boot component definition files (*.pcrlock and *.pcrlock.d/*.pcrlock, see
systemd.pcrlock(5)) that each define expected measurements for one component of the
boot process, permitting alternative variants for each. (Variants may be used to bless
multiple kernel versions or boot loader versions at the same time.)

It uses these inputs to generate a combined event log, validating it against the PCR
states. It then attempts to recognize event log records and matches them against the
defined components. For each PCR where this can be done comprehensively (i.e. where all
listed records and all defined components have been matched) this may then be used to
predict future PCR measurements, taking the alternative variants defined for each
component into account. This prediction may then be converted into a TPM2 access policy
(consisting of TPM2 PolicyPCR and PolicyOR items), which is then stored in an NV index in
the TPM2. This may be used to then lock secrets (such as disk encryption keys) to these
policies (via a TPM2 PolicyAuthorizeNV policy).

Use tools such as systemd-cryptenroll(1) or systemd-repart(8) to bind disk encryption to
such a systemd-pcrlock TPM2 policy. Specifically, see the --tpm2-pcrlock= switches of
these tools.

The access policy logic requires a TPM2 device that implements the "PolicyAuthorizeNV"
command, i.e. implements TPM 2.0 version 1.38 or newer.

COMMANDS

The following commands are understood:

log
This reads the combined TPM2 event log, validates it, matches it against the current
PCR values, and outputs both in tabular form. Combine with --json= to generate output
in JSON format.

Added in version 255.

cel
This reads the combined TPM2 event log and writes it to STDOUT in TCG Canonical Event
Log Format (CEL-JSON)[1] format.

Added in version 255.

list-components
Shows a list of component definitions and their variants, i.e. the *.pcrlock files
discovered in /var/lib/pcrlock.d/, /usr/lib/pcrlock.d/, and the other supported
directories. See systemd.pcrlock(5) for details on these files and the full list of
directories searched.

Added in version 255.

predict
Predicts the PCR state on future boots. This will analyze the TPM2 event log as
described above, recognize components, and then generate all possible resulting PCR
values for all combinations of component variants. Note that no prediction is made for
PCRs whose value does not match the event log records, for which unrecognized
measurements are discovered or for which components are defined that cannot be found
in the event log. This is a safety measure to ensure that any generated access policy
can be fulfilled correctly on current and future boots.

Added in version 255.

make-policy
This predicts the PCR state for future boots, much like the predict command above. It
then uses this data to generate a TPM2 access policy which it stores in a TPM2 NV
index. The prediction and information about the used TPM2 and its NV index are written
to /var/lib/systemd/pcrlock.json.

The NV index is allocated on first invocation, and updated on subsequent invocations.

The NV index contents may be changed (and thus the policy stored in it updated) by
providing an access PIN. This PIN is normally generated automatically and stored in
encrypted form (with an access policy binding it to the NV index itself) in the
aforementioned JSON policy file. This PIN may be chosen by the user, via the
--recovery-pin= switch. If specified it may be used as alternative path of access to
update the policy.

If the new prediction matches the old this command terminates quickly and executes no
further operation. (Unless --force is specified, see below.)

Starting with v256, a copy of the /var/lib/systemd/pcrlock.json policy file is encoded
in a credential (see systemd-creds(1) for details) and written to the EFI System
Partition or XBOOTLDR partition, in the /loader/credentials/ subdirectory. There it is
picked up at boot by systemd-stub(7) and passed to the invoked initrd, where it can be
used to unlock the root file system (which typically contains /var/, which is where
the primary copy of the policy is located, which hence cannot be used to unlock the
root file system). The credential file is named after the boot entry token of the
installation (see bootctl(1)), which is configurable via the --entry-token= switch,
see below.

Added in version 255.

remove-policy
Removes a previously generated policy. Deletes the /var/lib/systemd/pcrlock.json file,
and deallocates the NV index.

Added in version 255.

lock-firmware-code, unlock-firmware-code
Generates/removes .pcrlock files based on the TPM2 event log of the current boot
covering all records for PCRs 0 ("platform-code") and 2 ("external-code").

This operation allows locking the boot process to the current version of the firmware
of the system and its extension cards. This operation should only be used if the
system vendor does not provide suitable pcrlock data ahead of time.

Note that this data only matches the current version of the firmware. If a firmware
update is applied this data will be out-of-date and any access policy generated from
it will no longer pass. It is thus recommended to invoke unlock-firmware-code before
doing a firmware update, followed by make-policy to refresh the policy.

systemd-pcrlock lock-firmware-code is invoked automatically at boot via the
systemd-pcrlock-firmware-code.service unit, if enabled. This ensures that an access
policy managed by systemd-pcrlock is automatically locked to the new firmware version
whenever the policy has been relaxed temporarily, in order to cover for firmware
updates, as described above.

The files are only generated from the event log if the event log matches the current
TPM2 PCR state.

This writes/removes the files
/var/lib/pcrlock.d/250-firmware-code-early.pcrlock.d/generated.pcrlock and
/var/lib/pcrlock.d/550-firmware-code-late.pcrlock.d/generated.pcrlock.

Added in version 255.

lock-firmware-config, unlock-firmware-config
This is similar to lock-firmware-code/unlock-firmware-code but locks down the firmware
configuration, i.e. PCRs 1 ("platform-config") and 3 ("external-config").

This functionality should be used with care as in most scenarios a minor firmware
configuration change should not invalidate access policies to TPM2 objects. Also note
that some systems measure unstable and unpredictable information (e.g. current CPU
voltages, temperatures, as part of SMBIOS data) to these PCRs, which means this form
of lockdown cannot be used reliably on such systems. Use this functionality only if
the system and hardware is well known and does not suffer by these limitations, for
example in virtualized environments.

Use unlock-firmware-config before making firmware configuration changes. If the
systemd-pcrlock-firmware-config.service unit is enabled it will automatically generate
a pcrlock file from the new measurements.

This writes/removes the files
/var/lib/pcrlock.d/250-firmware-config-early.pcrlock.d/generated.pcrlock and
/var/lib/pcrlock.d/550-firmware-config-late.pcrlock.d/generated.pcrlock.

Added in version 255.

lock-secureboot-policy, unlock-secureboot-policy
Generates/removes a .pcrlock file based on the SecureBoot policy currently enforced.
This looks at the SecureBoot, PK, KEK, db, dbx, dbt, dbr EFI variables and predicts
their measurements to PCR 7 ("secure-boot-policy") on the next boot.

Use unlock-firmware-config before applying SecureBoot policy updates. If the
systemd-pcrlock-secureboot-policy.service unit is enabled it will automatically
generate a pcrlock file from the policy discovered.

This writes/removes the file
/var/lib/pcrlock.d/230-secureboot-policy.pcrlock.d/generated.pcrlock.

Added in version 255.

lock-secureboot-authority, unlock-secureboot-authority
Generates/removes a .pcrlock file based on the SecureBoot authorities used to validate
the boot path. SecureBoot authorities are the specific SecureBoot database entries
that where used to validate the UEFI PE binaries executed at boot. This looks at the
event log of the current boot, and uses relevant measurements on PCR 7
("secure-boot-policy").

This writes/removes the file
/var/lib/pcrlock.d/620-secureboot-authority.pcrlock.d/generated.pcrlock.

Added in version 255.

lock-gpt [DEVICE], unlock-gpt
Generates/removes a .pcrlock file based on the GPT partition table of the specified
disk. If no disk is specified automatically determines the block device backing the
root file system. This locks the state of the disk partitioning of the booted medium,
which firmware measures to PCR 5 ("boot-loader-config").

This writes/removes the file /var/lib/pcrlock.d/600-gpt.pcrlock.d/generated.pcrlock.

Added in version 255.

lock-pe [BINARY], unlock-pe
Generates/removes a .pcrlock file based on the specified PE binary. This is useful for
predicting measurements the firmware makes to PCR 4 ("boot-loader-code") if the
specified binary is part of the UEFI boot process. Use this on boot loader binaries
and suchlike. Use lock-uki (see below) for PE binaries that are unified kernel images
(UKIs).

Expects a path to the PE binary as argument. If not specified, reads the binary from
STDIN instead.

The pcrlock file to write must be specified via the --pcrlock= switch.

Added in version 255.

lock-uki [UKI], unlock-uki
Generates/removes a .pcrlock file based on the specified UKI PE binary. This is useful
for predicting measurements the firmware makes to PCR 4 ("boot-loader-code"), and
systemd-stub(7) makes to PCR 11 ("kernel-boot"), if the specified UKI is booted. This
is a superset of lock-pe.

Expects a path to the UKI PE binary as argument. If not specified, reads the binary
from STDIN instead.

The pcrlock file to write must be specified via the --pcrlock= switch.

Added in version 255.

lock-machine-id, unlock-machine-id
Generates/removes a .pcrlock file based on /etc/machine-id. This is useful for
predicting measurements systemd-pcrmachine.service(8) makes to PCR 15
("system-identity").

This writes/removes the file /var/lib/pcrlock.d/820-machine-id.pcrlock.

Added in version 255.

lock-file-system [PATH], unlock-file-system [PATH]
Generates/removes a .pcrlock file based on file system identity. This is useful for
predicting measurements systemd-pcrfs@.service(8) makes to PCR 15 ("system-identity")
for the root and /var/ file systems.

This writes/removes the files /var/lib/pcrlock.d/830-root-file-system.pcrlock and
/var/lib/pcrlock.d/840-file-system-path.pcrlock.

Added in version 255.

lock-kernel-cmdline [FILE], unlock-kernel-cmdline
Generates/removes a .pcrlock file based on /proc/cmdline (or the specified file if
given). This is useful for predicting measurements the Linux kernel makes to PCR 9
("kernel-initrd").

This writes/removes the file
/var/lib/pcrlock.d/710-kernel-cmdline.pcrlock/generated.pcrlock.

Added in version 255.

lock-kernel-initrd FILE, unlock-kernel-initrd
Generates/removes a .pcrlock file based on a kernel initrd cpio archive. This is
useful for predicting measurements the Linux kernel makes to PCR 9 ("kernel-initrd").
Do not use for systemd-stub UKIs, as the initrd is combined dynamically from various
sources and hence does not take a single input, like this command.

This writes/removes the file
/var/lib/pcrlock.d/720-kernel-initrd.pcrlock/generated.pcrlock.

Added in version 255.

lock-raw [FILE], unlock-raw
Generates/removes a .pcrlock file based on raw binary data. The data is either read
from the specified file or from STDIN (if none is specified). This requires that
--pcrs= is specified. The generated .pcrlock file is written to the file specified via
--pcrlock= or to STDOUT (if none is specified).

Added in version 255.

OPTIONS

The following options are understood:

--raw-description
When displaying the TPM2 event log do not attempt to decode the records to provide a
friendly event log description string. Instead, show the binary payload data in
escaped form.

Added in version 255.

--pcr=
Specifies the PCR number to use. May be specified more than once to select multiple
PCRs.

This is used by lock-raw and lock-pe to select the PCR to lock against.

If used with predict and make-policy this will override which PCRs to include in the
prediction and policy. If unspecified this defaults to PCRs 0-5, 7, 11-15. Note that
these commands will not include any PCRs in the prediction/policy (even if specified
explicitly) if there are measurements in the event log that do not match the current
PCR value, or there are unrecognized measurements in the event log, or components
define measurements not seen in the event log.

Added in version 255.

--nv-index=
Specifies the NV index to store the policy in. Honoured by make-policy. If not
specified the command will automatically pick a free NV index.

Added in version 255.

--components=
Takes a path to read *.pcrlock and *.pcrlock.d/*.pcrlock files from. May be used more
than once to specify multiple such directories. If not specified defaults to
/etc/pcrlock.d/, /run/pcrlock.d/, /var/lib/pcrlock.d/, /usr/local/pcrlock.d/,
/usr/lib/pcrlock.d/.

Added in version 255.

--location=
Takes either a string or a colon-separated pair of strings. Configures up to which
point in the sorted list of defined components to analyze/predict PCRs to. Typically,
the systemd-pcrlock tool is invoked from a fully booted system after boot-up and
before shutdown. This means various components that are defined for shutdown have not
been measured yet, and should not be searched for. This option allows one to restrict
which components are considered for analysis (taking only components before some point
into account, ignoring components after them). The expected string is ordered against
the filenames of the components defined. Any components with a lexicographically later
name are ignored. This logic applies to the log, predict, and make-policy verbs. If a
colon-separated pair of strings are specified then they select which phases of the
boot to include in the prediction/policy. The first string defines where the first
prediction shall be made, and the second string defines where the last prediction
shall be made. All such predictions are then combined into one set.

If used with list-components the selected location range will be highlighted in the
component list.

Defaults to "760-:940-", which means the policies generated by default will basically
cover the whole runtime of the OS userspace, from the initrd (as "760-" closely
follows 750-enter-initrd.pcrlock) until (and including) the main runtime of the system
(as "940-" is closely followed by 950-shutdown.pcrlock). See systemd.pcrlock(5) for a
full list of well-known components, that illustrate where this range is placed by
default.

Added in version 255.

--recovery-pin=
Takes one of "hide", "show" or "query". Defaults to "hide". Honoured by make-policy.
If "query", will query the user for a PIN to unlock the TPM2 NV index with. If no
policy was created before, this PIN is used to protect the newly allocated NV index.
If a policy has been created before, the PIN is used to unlock write access to the NV
index. If either "hide" or "show" is used, a PIN is automatically generated, and —
only in case of "show" — displayed on screen. Regardless if user supplied or
automatically generated, it is stored in encrypted form in the policy metadata file.
The recovery PIN may be used to regain write access to an NV index in case the access
policy became out of date.

Added in version 255.

--pcrlock=
Takes a file system path as argument. If specified overrides where to write the
generated pcrlock data to. Honoured by the various lock-* commands. If not specified,
a default path is generally used, as documented above.

Added in version 255.

--policy=
Takes a file system path as argument. If specified overrides where to write pcrlock
policy metadata to. If not specified defaults to /var/lib/systemd/pcrlock.json.

Added in version 255.

--force
If specified with make-policy, the predicted policy will be written to the NV index
even if it is detected to be the same as the previously stored one.

Added in version 255.

--entry-token=
Sets the boot entry token to use for the file name for the pcrlock policy credential
in the EFI System Partition or XBOOTLDR partition. See the bootctl(1) option of the
same regarding expected values. This switch has an effect on the make-policy command
only.

Added in version 256.

--json=MODE
Shows output formatted as JSON. Expects one of "short" (for the shortest possible
output without any redundant whitespace or line breaks), "pretty" (for a pretty
version of the same, with indentation and line breaks) or "off" (to turn off JSON
output, the default).

--no-pager
Do not pipe output into a pager.

-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.

NOTES

        1. TCG Canonical Event Log Format (CEL-JSON)
           https://trustedcomputinggroup.org/resource/canonical-event-log-format/

NAME

SYNOPSIS

DESCRIPTION

COMMANDS

OPTIONS

EXIT STATUS

SEE ALSO

NOTES