Some (out of tree) servers require use of a USB keyboard, and need
the USB kernel modules loaded prior to checking for keypress to enter
a recovery console. Since loading the modules affects the value in PRC5
and can cause issues putting a LUKS key in TPM, guard the loading of the
USB modules with CONFIG_USB_KEYBOARD and remove the unguarded call from
gui-init.
This should resolve issues #603 and #674.
Signed-off-by: Matt DeVillier <matt.devillier@puri.sm>
Not setting USB_FAILED when call to mount-usb succeeds results
in a spurious 'sh: 0 unknown operand' error printed to console.
Signed-off-by: Matt DeVillier <matt.devillier@puri.sm>
Since the custom password is used to set the GPG admin
password as well as the TPM and GPG user passwords, an
8-character minimum is required. Inform the user of this,
and validate custom password length upon entry.
Signed-off-by: Matt DeVillier <matt.devillier@puri.sm>
If /boot isn't mounted, we can't read the HOTP counter, so no
point in reading from the TPM. This speeds up getting to the
main menu in the case of an inaccessible or non-existant /boot.
Signed-off-by: Matt DeVillier <matt.devillier@puri.sm>
Update text on TOTP error prompt to provide better
guidance for users following the use of the OEM
factory reset function
Signed-off-by: Matt DeVillier <matt.devillier@puri.sm>
If kexec-sign-config fails due to GPG key not present,
the double die() results in a kernel panic (and if it didn't,
/boot would be left mounted RW). Fix this by removing call to
die() and ensuring /boot remounted RO regardless checksum
update success or failure.
Signed-off-by: Matt DeVillier <matt.devillier@puri.sm>
Normally we resort to default passwords for OEM reset, however we have a
use case where it would be convenient to set a custom password instead.
This patch adds a simple prompt (that defaults to the defaults if you
hit Enter) that enables someone using the OEM reset to enter a single
password that will replace the defaults (TPM, GPG Admin, GPG User).
If the user chooses to flash a "cleaned" ROM (not persisting settings
or GPG keys) then the signatures on /boot are no longer valid, so clear
them out. This allows for the OEM factory reset prompt to be shown on
the next boot.
Signed-off-by: Matt DeVillier <matt.devillier@puri.sm>
Users may wish to temporarily boot an OS from a drive other than
their primary boot drive, without changing the default and saving
to ROM. Mounting /boot after changing the device selection
facilitates this by allowing the user to then choose an unsafe boot
from the newly-selected boot drive.
Signed-off-by: Matt DeVillier <matt.devillier@puri.sm>
when commit [928f003] config-gui: add 'Full Reset' option
was added, the bottom end of the save config option was
accidentally truncated; restore it to fix save config option
Signed-off-by: Matt DeVillier <matt.devillier@puri.sm>
Add a check to determine if first boot after flashing a cleaned
ROM, and prompt user to run the OEM Factory Reset if so
Signed-off-by: Matt DeVillier <matt.devillier@puri.sm>
Add an OEM Factory Reset menu option, which performs an
unattended reset and configuration of the device's TPM,
GPG security token, and boot device / boot selection.
Signed-off-by: Matt DeVillier <matt.devillier@puri.sm>
Add oem-factory-reset script which performs an unattended
reset and configuration of the device's TPM, GPG security token,
and boot device / boot selection.
Signed-off-by: Matt DeVillier <matt.devillier@puri.sm>
Add function to detect boot device. Start by checking
CONFIG_BOOT_DEV, then iterate thru all bootable partitions.
Check if partition is mountable, contains grub directory.
Update CONFIG_BOOT_DEV and mount on /boot if successful.
Signed-off-by: Matt DeVillier <matt.devillier@puri.sm>
Initial card detection can sometimes fail, so prompt the user
to remove/reinsert their GPG card before retrying. Since
errexit is likely set, disable it prior to calling --card-status so
we can handle the error ourself, then re-set if necessary when done.
Signed-off-by: Matt DeVillier <matt.devillier@puri.sm>
Next prompt will be to ensure GPG key is attached, which defaults
to Y, so default here as well for consistency
Signed-off-by: Matt DeVillier <matt.devillier@puri.sm>
Check that any files added to cbfs exist before attempting to
add them, so flashing doesn't fail after a reset.
Signed-off-by: Matt DeVillier <matt.devillier@puri.sm>
Add Full Reset option to clear all GPG keys and user settings,
both from the local filesystem and running firmware, and
clear/reset the TPM
Signed-off-by: Matt DeVillier <matt.devillier@puri.sm>
If the boot device is invalid or unabled to be mounted
and the user opts to select a new boot device, jump
directly to that menu option and avoid the additional
step of showing the config main menu.
Signed-off-by: Matt DeVillier <matt.devillier@puri.sm>
Updating TOTP/HOTP is mainly necessary after a user updates
their firmware, and no need to force another reboot.
Signed-off-by: Matt DeVillier <matt.devillier@puri.sm>
use similar filtering logic as with USB drives to provide
the user a more sane list of boot device options. Show user
only valid bootable partitions, not block devices.
There's no point in showing /dev/nvme0 and /dev/nvme0n1 (eg)
when /dev/nvme0n1p[1..n] (eg) exist, as the former are not
valid boot devices.
Signed-off-by: Matt DeVillier <matt.devillier@puri.sm>
Add optional parameter to bypass menu selection and
immediately select a menu option. This allows us to call
the 'Set Boot Device' option directly, saving the user
an unnecessary step.
Signed-off-by: Matt DeVillier <matt.devillier@puri.sm>
Introduce option to remove any existing key(s) from firmware
and add a user-suppled key, before reflashing.
Move existing code for adding a new key to a separate function
so it can be reused for new feature without duplication.
Signed-off-by: Matt DeVillier <matt.devillier@puri.sm>
If CONFIG_BOOT_DEV isn't set or otherwise fails to mount,
we prompt the user to change the /boot device, but never
attempt to mount it to ensure it's sane, leading to
potential failures later in the config/boot process.
Ensure that CONFIG_BOOT_DEV is updated after the /boot device
is changed, and attempt to re-mount /boot after the change.
Signed-off-by: Matt DeVillier <matt.devillier@puri.sm>
If the user has changed the /boot config but not yet flashed,
it's reasonable for them to expect that flashing to add/update
a GPG key won't revert those changes.
Signed-off-by: Matt DeVillier <matt.devillier@puri.sm>
In order to streamline the initial setup, prompt user to
update checksums/sign /boot files after adding a key and
updating the firmware, in order to avoid an extra reboot.
Signed-off-by: Matt DeVillier <matt.devillier@puri.sm>
Move the non-GUI component of update_checksums() to
/etc/functions so it can be reused outside of gui-init.
Add check that /boot/kexec_default_hashes.txt exists before parsing
it, since doesn't exist if there's no default boot target set yet.
Eliminates spurious error text and/or premature exit depending on
state of errexit.
Signed-off-by: Matt DeVillier <matt.devillier@puri.sm>
'Options' makes more sense than 'Settings' given the submenu's contents.
Tidy up Boot Options as well
Signed-off-by: Matt DeVillier <matt.devillier@puri.sm>
Before anything else, ensure that a default boot device
is set. If not, prompt the user to set one. If set, ensure
that /boot can be mounted successfully; else prompt the
user to select a new boot device.
Signed-off-by: Matt DeVillier <matt.devillier@puri.sm>
If /boot isn't mounted, we can't read the HOTP secret, so no
point in reading from the TPM. This speeds up getting to the
main menu in the case of an inaccessible or non-existant /boot,
and maintains the warning condition from not being able to
validate the HOTP.
Signed-off-by: Matt DeVillier <matt.devillier@puri.sm>
Since a USB boot target can't be the default (at least currently,
/boot must be on internal media), skip the extraneous prompt to
set it as such when booting from USB.
Signed-off-by: Matt DeVillier <matt.devillier@puri.sm>
Exclude dot folders from ROM search path, so that files in
.Trash (eg) aren't shown. Sort the remaining options.
Signed-off-by: Matt DeVillier <matt.devillier@puri.sm>
Using sort on USB boot options produces a reverse-ordered list,
leading users to often select the wrong option. Add the -r
parameter to sort to correct the list order and make the default
option the first in the list.
Signed-off-by: Matt DeVillier <matt.devillier@puri.sm>
Because of the way unseal-hotp is called from gui-init,
dropping to a recovery shell when failing to mount /boot
causes it to hang, leaving the user stranded until they
kill it with CTRL+C. Instead, simply return and continue
to the main GUI menu where the user can address the problem.
Rename the function to clarify difference from other versions
of mount_boot() which do drop to the recovery shell.
Signed-off-by: Matt DeVillier <matt.devillier@puri.sm>
Fix HOTP verfication failure if LK admin pin/passphrase contains
spaces by quoting the variables when passed to functions.
Test: set LK admin pin to passphrase with spaces, generate
new TOTP/HOTP, verification passes.
Signed-off-by: Matt DeVillier <matt.devillier@puri.sm>
Reading the file into a variable and then redirecting to stdin
via echo() can cause the binary data to be truncated, leading
to an invalid base32 value and failure to properly generate
and validate the HOTP code.
To resolve this, pass the file directly to hotp(), and ensure
it is removed properly regardless of success or failure to
prevent leakage.
Fixes "Invalid base32 string" error seen when attempting to
generate a new TOTP secret.
Signed-off-by: Matt DeVillier <matt.devillier@puri.sm>
Add a main boot menu entry to power off. This enables users to
only verify the firmware integrity using OTP, and do nothing more.
After having left the device out of sight, one might want to do
a quick sanity check only.
Since we already have a script to safely power down, we make use of
it now.
Instead of relying on a hard-coded USB disk, it would be better if the
mount script attempted to dynamically detect available USB disks. This
modification to the USB mount script attempts to handle the common case
of a single USB disk but can also handle the case of multiple disks
where it will present the user with all available USB disks
This mimics tlauion's OEM work in the sense that a user (or OEM) could
choose this option and it will reset an OpenPGP smart card and
automatically generate a random key on it. The idea is to allow an OEM
to set up a Librem Key and Heads on a machine before shipping with a
random key, so the user can test for tampering when they receive the
machine, and then the user can choose to reset all of the keys with
their chosen keys after that fact.
Currently Heads relies on a hard-coded config value to determine which
USB disk to mount. This can be problematic when trying to distribute a
pre-built version of Heads that can work on multiple disk
configurations. I've modified the USB mounting script so that it
attempts to detect all USB boot disks present on the system, pick sane
defaults, and prompt the user when there are multiple choices.
I've also removed the USB configuration option from config-gui.sh as
this config option is no longer used.
This change updates the very basic GPG smartcard feature in the GPG GUI
so that it can properly support generating a key from within Heads. It
offers the user the option to copy the generated GPG public key to a USB
thumb drive so it's not lost as well as the option to reflash the
current Heads BIOS with this new public key added to the keyring.
I've moved the common functions required to flash a new ROM with GPG
changes into a shared function at the top of the script.
It makes more logical sense for GPG functions to be split out into their
own menu instead of being part of the "Flash" menu. This creates a
gpg-gui.sh script and moves GPG options there while adding a few
additional features (like listing keys and initial smartcard key
generation support).
key-init makes sure trustdb is updated at run time and user and distro keys are ultimately trusted. Each time a file is signed, the related public key is showed without error on it's trustability.
flash-gui deals with gpg1 to gpg2 migration. If pubring.kbx is found, pubring.gpg is deleted from running rom dump.
.ash_history: add examples to generate keys and otrust in rom
flash-gui: export otrust and import it in rom
key-init: import otrust.txt if present to supress warning about user public key being untrusted
gpg2 needs GPG_TTY set to function properly. We set it in /init so it
is inherited by all children. The call to $(tty) must be after /dev and
(preferably) /dev/pts are mounted.
Signed-off-by: Jason Andryuk <jandryuk@gmail.com>
There are cases when grepping for an option in the config file where
grep will not find it, which is fine in this case, but without adjusting
the exit code in that case it can make an entire script bail out.
We need to handle the case where the specific config file doesn't exist,
or else grep fails, so we touch the file ahead of time. Mounting the usb
storage caused problems when you re-enter the menu a second time, so we
will just load the storage module.
As part of the config gui we want to be able to have the system define
new config options without them being lost if the user makes their own
changes in CBFS. To allow that this change creates a function initiated
in init that combines all /etc/config* files into /tmp/config. All
existing scripts have been changed to source /tmp/config instead of
/etc/config. The config-gui.sh script now uses /etc/config.user to hold
user configuration options but the combine_configs function will allow
that to expand as others want to split configuration out further.
As it stands here are the current config files:
/etc/config -- Compiled-in configuration options
/etc/config.user -- User preferences that override /etc/config
/tmp/config -- Running config referenced by the BIOS, combination
of existing configs
This change will add a new GUI script that will allow users to change
their running configuration (currently just /boot and USB boot options)
and optionally persist that modified configuration with reflashing the
BIOS with a modified cbfs.
The Librem coreboot is labeled with the current version and is visible
from dmidecode and is supposed to reflect the current version of
coreboot, however it was out of date and reflected 4.7 when Heads has
moved on to 4.8.1.
I've also added a simple change to further simplify onboarding by
warning users who have Librem Key configured when they boot without it
being inserted.
We want to catch the missing GPG keyring error regardless of TPM failure
or even in the case of a system without a TPM at all so we need to move
that section up above the TPM check.
To help with onboarding new users to Heads, this change will detect when
Heads does not have any keys in its keyring and will guide the user
through adding a key to the running BIOS. It's important that this
happen *before* guiding them through setting up an initial TOTP/HOTP
secret because adding a GPG key changes the BIOS, so the user would have
to generate TOTP/HOTP secrets 2x unless we handle the keyring case
first.
In addition to this change I've simplified the main menu so that the
majority of the options appear under an 'advanced' menu.
When the Librem Key is enabled, the kernel loads USB modules at boot,
this causes PCR5 to change and breaks unsealing the LUKS key (if set).
This change retains the protection of the PCR5 check unless Librem Key
is enabled.
Granted the user should really be using the Librem Key/phone to check
for tampering (since an attacker could control the Heads background
color) but this provides another visual queue for the user with
the GUI menu to catch less sophisticated tampering.
The HOTP counter isn't a secret but is just used to prevent replay
attacks (the time-based counter in TOTP isn't a secret either) so it
doesn't need to be protected in the TPM and storing it as a TPM
monotonic counter was causing conflicts with the Heads configuration
counter as TPM 1.2 can only increment one counter per reboot.
This change moves the HOTP counter into the file in /boot that was
previously keeping track of the TPM counter id.
TPM v1.2 has a limitation in that only a single monotonic counter can be
incremented between reboots [1]. So in the event we are using HOTP
monotonic counters, we need to reference those for the Heads rollback
counter when we update file signatures in /boot, otherwise the increment
stage at kexec-sign-config will fail since at each boot, the HOTP
monotonic counter has already been incremented.
[1] https://projects.csail.mit.edu/tc/tpmj/UsersGuide.html#inccounter
The Librem Key is a custom device USB-based security token Nitrokey is
producing for Purism and among other things it has custom firmware
created for use with Heads. In particular, when a board is configured
with CONFIG_LIBREMKEY, this custom firmware allows Heads to use the
sealed TOTP secret to also send an HOTP authentication to the Librem
Key. If the HOTP code is successful, the Librem Key will blink a green
LED, if unsuccessful it will blink red, thereby informing the user that
Heads has been tampered with without requiring them to use a phone to
validate the TOTP secret.
Heads will still use and show the TOTP secret, in case the user wants to
validate both codes (in case the Librem Key was lost or is no longer
trusted). It will also show the result of the HOTP verification (but not
the code itself), even though the user should trust only what the Librem
Key displays, so the user can confirm that both the device and Heads are
in sync. If HOTP is enabled, Heads will maintain a new TPM counter
separate from the Heads TPM counter that will increment each time HOTP
codes are checked.
This change also modifies the routines that update TOTP so that if
the Librem Key executables are present it will also update HOTP codes
and synchronize them with a Librem Key.
In addition to being able to flash a ROM from the GUI, it would also be
useful for a user to be able to add a GPG key to their keyring using the
flashing tool. This change adds the ability for a user to edit both a
ROM located on a USB key and also edit the running BIOS by using
flashrom to make a local copy of the running BIOS, edit it, then reflash
it. This also supports the upcoming delete feature in CBFS for
circumstances where keyring files already exist within CBFS.
If we want to modify a running BIOS we will need the ability to pull
down the current BIOS, modify it, and then reflash. This change adds a
read option to flash.sh and pulls down three versions of the BIOS and
only exists successfully if all three match.
To keep the flash logic simpler the GUI logic has been split into a
flash-gui.sh program so flash.sh behaves closer to the original flashrom
scripts it was based from. I've also removed the previous flashrom
scripts and incorporated their options into flash.sh. Finally I set
CONFIG_BOARD via the Makefile instead of setting a duplicate option in
each board's config.
Based on the conversation for PR #406, we decided to go with a more
generic script for general-purpose flashing instead of having individual
(and therefore very similar) flash scripts for each board type. This
script currently handles flashrom on Librem and X230 board types and
introduces a new CONFIG_BOARD option that sets specific flashrom
arguments based on the board.
It also adds support to gui-init to call this flash script.
Currently the TPM counter label is hard-coded. By changing it to a
variable in this function we can reuse all of the TPM counter functions
to create other monotonic counters in the TPM (if the hardware supports
it) with custom labels.
Wrapping text to 80 characters works but due to font size and padding
the maximum 80 character lines start to get truncated. Extending the
window to 90 characters will resolve this.
While the whiptail program wraps text appropriately based on column
size, the fbwhiptail program doesn't, leading to text that scrolls off
the window where it can no longer be read. This change wraps the longer
text output so it all fits.
Since fbwhiptail allows us to customize the background colors, we should
colorize warnings and error messages to provide a user with an
additional subtle cue that there might be a problem. I have added two
additional configuration options:
CONFIG_WARNING_BG_COLOR
CONFIG_ERROR_BG_COLOR
and in the librem13v2.config file you can see an example for how to set
them to be yellow and red gradients, respectively. I've also updated the
main two scripts that use whiptail to include those background colors.
If you decide to use regular whiptail, just don't set these config
options and it should behave as expected.
When a user gets confirmation of their boot menu choice, that's largely
to give them the option of making their boot choice the default. In the
case of "force mode" there's no reason for the user to be presented with
that dialog so this change skips right ahead to the boot once they have
In the event a user does pick the insecure "force" boot option that
bypasses checksum and signing checks in Heads, it would be nice to
provide a clear visual warning during the boot process that they are in
this state. This change will add a kernel argument that changes the boot
console background to be red and removes any boot splash that might
obscure it, in the event the user picks the insecure boot mode.
Since a user should only boot into this mode during emergencies, having
it be apparent that it's an unsafe mode helps ensure the user doesn't
pick this boot option needlessly.
Currently when the boot entries change, kexec-select-boot dies. Given
the normal loop is set up to catch this event and display a regular boot
menu at the next iteration of the loop, instead of dying it would be
better to just warn and then return from that function back into the
main loop. In addition to that I added a GUI menu for the same warning
when in GUI mode.
Part of the Heads workflow involves handling legitimate changes to /boot
as part of the package manager. This is a challenging workflow to handle
as package managers on many systems work in a completely unattended way
(and some even reboot first, apply updates, and then reboot again).
We need to be able to detect changes that are potentially caused by a
package manager so to do that I've set up a trigger within the OS
(currently just for Debian) that runs both before and after package
updates. It verifies the signatures in /boot and if they fail before
package updates it creates a log file in
/boot/kexec_package_trigger_pre.txt. If they fail after package updates
run /boot/kexec_package_trigger_post.txt is created. These files contain
the following fields:
CHANGED_FILES: A list of files in /boot that failed the sha256sum check
UPDATE_INITRAMFS_PACKAGE: An (optional) list of packages known to
trigger initramfs changes
Following those fields is a list of log output from the last package
manager run which contains its own formatted fields (I'm pulling from
/var/lib/dpkg/info).
When a user selects a boot option, gui-init first verifies the
checksums just to catch errors before calling kexec-select-boot. If
there are any errors it looks for these package logs and if they exist,
it displays appropriate warnings. If the files are absent it displays a
more generic warning. The user is also given an opportunity to re-sign
the /boot hashes.
There was a bug in the "force" boot mode where it would still fail if
signatures didn't match. This was because the check_config function
validates the signatures for kexec files. I've added a few conditionals
here so that in the case of a forced boot mode, we can bypass those
signature checks that would prevent boot and error out to a recovery
console.
The number of options we want in the menu is starting to get large
enough that it's worth slimming things down in the main menu and move
options to nested menus. Along with this nested menu change is the
option to re-sign and re-hash files in /boot directly from the menu.
One of the other core functions a user needs when bootstrapping is
taking over the TPM. I've added a new option in the menu for this and it
revealed that some of the menus needed more space so I've widened all
the menus and also made the main menu longer so the options don't
scroll.
The point of this change is to provide a failsafe (failunsafe?) mode for
less technically-savvy users who will ultimately be using Heads by
default on Librem laptops.
There are some scenarios where an end user might forget to update hashes
in /boot after an initrd change or might have some other hash mismatch.
Currently that user would then be stuck in a recovery console in Heads
not knowing what to do within that limited shell environment to fix the
situation.
This change adds a 'force' mode to kexec-select-boot that goes straight
into a boot menu and bypasses the hash checks so the user could more
easily get back into their system to attempt to repair it. It adds
appropriate warnings about why this is a risky option and moves it down
toward the bottom of the menu. The goal would be to just have this be an
emergency option our support could guide a user to if they ended up in
this situation.
Guarded linuxboot specific init entries
Removed Makefile entries into separate file (conflicts with srcing /etc/config)
Added CONFIG_BOOT_LOCAL/_REMOTE to control interface setup
Fixed CONFIG_TPM usage
if "CONFIG_TPM=y" is not present in the config file, functionalities
needing TPM could be disabled, while leaving other functionalities intact.
This will make Heads a more general-usage bootloader payload atop coreboot.
In particular I added a GUI menu to instruct the user if there is no
TOTP code registered (as is the case upon first flash) and also added
better handling of the case the user selects 'default boot' when there
is no default boot set yet. Apart from that where there were text-only
menus left in gui-init I've replaced them with GUI menus.
When selecting the boot menu option (m) in the gui-init you call out to
kexec-select-boot. To better maintain the graphical menu experience,
I've added a -g option to kexec-select-boot that, when set, will use a
graphical whiptail menu for the most common menu selection modes.
This is a modified version of the generic-init script that uses whiptail
to generate a graphical menu. I changed two of the options so that the
user can refresh the menu to get an updated TOTP code if needed.
USB smart card readers are most full speed devices, and there is no
"rate-matching hubs" beneath the root hub on older (e.g. GM45) plat-
forms, which has companion OHCI or UHCI controllers and needs cor-
responding drivers to communicate with card readers directly plugged
into the motherboard, otherwise a discrete USB hub should be inserted
between the motherboard and the reader.
This time I make inserting linux modules for OHCI and UHCI controllable
with option CONFIG_LINUX_USB_COMPANION_CONTROLLER.
A linux config for x200 is added as an example.
Tested on my x200s and elitebook revolve 810g1.
if "CONFIG_TPM=y" is not present in the config file, functionalities
needing TPM could be disabled, while leaving other functionalities intact.
This will make Heads a more general-usage bootloader payload atop coreboot.
This development branch builds a NERF firmware for the Dell R630
server. It does not use coreboot; instead it branches directly
from the vendor's PEI core into Linux and the Heads runtime
that is setup to be run as an EFI executable.
Closes issue #226
Also changed to procedure to show LVM volume groups and block
device ids to aid in choosing the right combination during the
TPM LUKS key sealing process.
Changed the checking of required hashes or required rollback state
to be right before boot, allowing the user to sign/set defaults
in interactive mode.
Also cleaned up usages of recovery and fixed iso parameter
regression.
Similar to qubes-update, it will save then verify the hashes of
the kexec files. Once TOTP is verified, a normal boot will verify
that the file hashes and all the kexec params match and if
successful, boot directly to OS.
Also added a config option to require hash verification for
non-recovery boots, failing to recovery not met.
Refactored boot parsing code and applied that in local-init to
scan /boot for grub options and allow the user to unsafely boot
anything. This goes a long way to addressing #196.
Optionally the user can customize those boot parameters or enforce
arbitrary hashes on the boot device by creating and signing config
files in /boot/ or /media/ or /media/kexec_iso/ISO_FILENAME/.
usb-boot automatically uses internal xen binary / command line
when multiboot is detected.
also tweaked to evaluate/remove variable refs in kexec arguments
Supports booting from USB media using either the root device or
a signed ISO as the boot device. Boot options are parsed with
quick/dirty shell scripts to infer kexec params.
Closes#195 and begins to address #196
This adds support for seamless booting of Qubes with a TPM disk key,
as well as signing of qubes files in /boot with a Yubikey.
The signed hashes also includes a TPM counter, which is incremented
when new hashes are signed. This prevents rollback attacks against
the /boot filesystem.
The TPMTOTP value is presented to the user at the time of entering
the disk encryption keys. Hitting enter will generate a new code.
The LUKS headers are included in the TPM sealing of the disk
encryption keys.
