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sbctl/docs/sbctl.8.txt
Lena bf194cbcc9 sbctl.8: fix typo in the man page 
The RSA key size is 4096, not 4098.
2024-08-05 18:46:33 +02:00

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sbctl(8)
========
Name
----
sbctl - Secure Boot Manager
Synopsis
--------
*sbctl* <command>
Description
-----------
*sbctl* is a tool that allows one to create keys for secure boot, securely
enroll them and keep track of files to sign.
EFI signing commands
--------------------
**status**::
Shows the current secure boot status of the system. It checks if you are
currently booted in UEFI with Secure Boot, and whether Setup Mode
has been enabled.
**create-keys**::
Creates a set of signing keys used to sign EFI binaries. Currently, it
will create the following keys:
* Platform Key
* Key Exchange Key
* Signature Database Key
*-e*, *--export*;;
The directory to persist the exported keys.
*-d*, *--database-path*;;
Path to save the GUID file when generating keys.
**enroll-keys**::
Enrolls the created key into the EFI variables.
Note that some devices have hardware firmware that is signed and
validated when Secure Boot is enabled. Failing to validate this firmware
could brick devices. It's recommended to enroll your own keys with
Microsoft certificates.
*-m*, *--microsoft*;;
Enroll UEFI vendor certificates from Microsoft into the
signature database.
+
See **Option ROM***.
*-t*, *--tpm-eventlog*;;
Enroll checksums from the TPM Eventlog into the signature
database.
+
See **Option ROM***.
+
This feature is experimental
*-c*, *--custom*;;
Enroll custom KEK and db certificates from "/var/lib/sbctl/keys/custom/KEK/",
"/var/lib/sbctl/keys/custom/db/",
respectively.
*-f*, *--firmware-builtin*;;
Enroll signatures from dbDefault, KEKDefault or PKDefault. This
is usefull if sbctl does not vendor your OEM certificates, or
doesn't include all of them.
+
Valid values are "db", "KEK" or "PK" passed as a comma
delimitered string.
+
Default: "db,KEK"
*--yes-this-might-brick-my-machine*, **--yolo**;;
Ignore the Option ROM error and continue enrolling keys into the
UEFI firmware.
+
See **Option ROM***.
*-i*, *--ignore-immutable*;;
Ignore checking `/sys/firmware/efi/efivars/` for immutable
files and unset the immutable attribute before enrolling
certificates.
*--export*;;
Export the keys we intend to enroll as EFI Signature Lists
(esl), or EFI Authenticated Variables (auth) into the current
working directory.
+
Valid values are: esl, auth.
*-p*, *--partial*;;
Enroll keys only for the hierarchy specified.
+
Valid values are: db, KEK, PK.
*--custom-bytes*;;
Enroll a custom bytefile provided by its path to the efivar specified by partial.
*-a*, *--append*;;
Instead of replacing the currently enrolled keys, append the provided one.
*--keytype*;;
Set the keytype for all signing keys used by sbctl. This
includes PK, KEK and db keys.
+
Default: file
+
Valid values are: file, tpm
*--pk-keytype*;;
Set the PK key type.
+
Default: file
+
Valid values are: file, tpm
*--kek-keytype*;;
Set the KEK key type.
+
Default: file
+
Valid values are: file, tpm
*--db-keytype*;;
Set the db key type.
+
Default: file
+
Valid values are: file, tpm
**sign** <FILE>...::
Signs an EFI binary with the created key. The file will be checked for
valid signatures to avoid duplicates.
*-o* 'PATH', *--output* 'PATH';;
Output filename. Default replaces the file.
*-s*, *--save*;;
Save file to the database.
**sign-all**::
Signs all enrolled EFI binaries.
*-g*, *--generate*;;
Generate all bundles before signing.
**import-keys**::
Imports existing keys into sbctl.
*--db-cert* 'PATH';;
Path to a valid Database (db) certificate.
*--db-key* 'PATH' ;;
Path to a valid Database (db) private key.
*--kek-cert* 'PATH' ;;
Path to a valid Key Exchange Key (KEK) certificate.
*--kek-key* 'PATH' ;;
Path to a valid Key Exchange Key (KEK) private key.
*--pk-cert* 'PATH' ;;
Path to a valid Platform Key(PK) certificate.
*--pk-key* 'PATH' ;;
Path to a valid Platform Key (PK) private key.
*--directory* 'PATH' ;;
Path to a key directory. The expected file locations inside this directory are:
* PK/PK.key
* PK/PK.pem
* KEK/KEK.key
* KEK/KEK.pem
* db/db.key
* db/db.pem
*--force*;;
Overwrite the existing key directory used by sbctl.
**list-files**, **ls-files**, **ls**::
Lists all enrolled EFI binaries.
**remove-file** <FILE>, **rm-file** <FILE>, **rm** <FILE>::
Removes the file from the signing database.
**list-enrolled-keys**, **ls-enrolled-keys**::
Lists all enrolled keys on the system.
**verify** [FILE...]::
Looks for EFI binaries with the mime type application/x-dosexec in the
ESP partition, and looks at the file database. Checks if they have been
signed with the Signature Database Key. Takes an optional file argument
to check specific files.
**reset**::
Resets the Platform Key. This sets the machine out of Secure Boot mode
and allows key rotation.
*-p*, *--partial*;;
Reset keys only for the hierarchy specified.
+
Valid values are: db, KEK, PK.
**rotate-keys**::
Rotate the secure boot keys and replace them with newly generated keys.
Saves the old keys to a directory in /var/tmp and resigns any files from
the file database.
*--backup-dir* 'PATH';;
Choose backup directory for old keys.
*-p*, *--partial*;;
Rotate keys only for the hierarchy specified.
+
Valid values are: db, KEK, PK.
*-k*, *--key-file*;;
Key file to be appended for the specified hierarchy.
*-c*, *--cert-file*;;
Certificate file to be appended for the specified hierarchy.
*--keytype*;;
Set the keytype for all signing keys used by sbctl. This
includes PK, KEK and db keys.
+
Default: file
+
Valid values are: file, tpm
*--pk-keytype*;;
Set the PK key type.
+
Default: file
+
Valid values are: file, tpm
*--kek-keytype*;;
Set the KEK key type.
+
Default: file
+
Valid values are: file, tpm
*--db-keytype*;;
Set the db key type.
+
Default: file
+
Valid values are: file, tpm
**export-enrolled-keys**::
Export already enrolled keys from the system.
*--dir* 'PATH';;
Output directory for the exported keys.
*--format* 'TYPE';;
Format of the exported keys.
+
Default: der
Valid values: esl, auth.
**setup**::
Setup an sbctl installation.
This commands enables declarative configuration of sbctl through the
configuration file. It can also print the current configuration and the
current state of the installation.
*--setup*;;
Setup an sbctl install based off on the provided configuration
file, or the default read configuration from
/etc/sbctl/sbctl.conf.
+
This will automatically do the create-keys and enroll-keys
commands and also setup the files database for signing.
+
See linkman:sbctl.conf[5] for details.
*--migrate*;;
Migrate the configuration and setup of sbctl to a new iteration.
+
Currently the only migration for sbctl is moving from
/usr/share/secureboot to /var/lib/sbctl.
*--print-config*;;
Prints a serialized version of the current configuration of
sbctl.
+
See linkman:sbctl.conf[5] for details.
*--print-state*;;
Prints the state of the sbctl installation. Currently only
prints whether or not sbctl has been installed on the system.
+
Note: This option requires passing --json.
**help**::
Displays a help message.
EFI binary commands
------------------
**bundle** ['FLAGS'] <NAME>::
Creates a bundle that should produce EFI binaries. See **BUNDLES**
below for more details.
*-a* 'PATH', *--amducode* 'PATH';;
AMD microcode location.
*-c* 'PATH', *--cmdline* 'PATH';;
Cmdline location. (default "/etc/kernel/cmdline")
*-e* 'PATH', *--efi-stub* 'PATH';;
EFI Stub location. (default "/usr/lib/systemd/boot/efi/linuxx64.efi.stub")
*-p* 'PATH', *--esp* 'PATH';;
ESP location. (default "/efi")
*-h*, *--help*;;
Help for bundle.
*-f* 'PATH', *--initramfs* 'PATH';;
Initramfs location. (default "/boot/initramfs-linux.img")
*-i* 'PATH', *--intelucode* 'PATH';;
Intel microcode location.
*-k* 'PATH', *--kernel-img* 'PATH';;
Kernel image location. (default "/boot/vmlinuz-linux")
*-o* 'PATH', *--os-release* 'PATH';;
OS Release file location. (default "/usr/lib/os-release")
*-s*, *--save*;;
Save bundle to the database.
*-l* 'PATH', *--splash-img* 'PATH';;
Boot splash image location.
**generate-bundles**::
This command generates all bundles.
*-s*, *--sign*;;
Sign all the generated bundles.
**remove-bundle** <NAME>, **rm-bundle** <NAME>::
Removes a bundle from the list. This does not delete the bundle itself.
**list-bundles**, **ls-bundle**::
List all registered bundles to generate.
Options
-------
**-j**, **--json**::
This enables supported commands to output their values in json instead
of human-readable text. This is practical for parsing data with tools
like `jq`.
**-c**, **--config**::
An optionally provided path to the configuration file that should be
used by sbctl.
+
Default: /etc/sbctl/sbctl.conf
**--disable-landlock**::
Disables landlock sandboxing in sbctl.
+
See linkman:landlock[7].
**--debug**::
Enable verbose debug logging. This will break the pretty printed text.
Bundles
-------
Note: This is being deprecated. Please move to dracut/mkinitcpio/ukify.
Normally, only the kernel is signed with your secure boot keys. This means the
kernel command line and initramfs can be changed without possibility of verification.
Bundles are EFI executables which pack all three (initramfs, kernel and
cmdline) into a single file which is easy to sign. Avoiding any unsigned
files during boot makes the whole process more tamper-proof.
When a bundle is generated, its configuration is stored into the bundle
database (see **FILES**). Subsequent executions of *sbctl generate-bundles*
will rebuild these bundles, so you don't need to re-specify all parameters
after each system update.
Tip: systemd-boot will automatically show entries for any bundles found in
*esp/EFI/Linux/+++*+++.efi*.
Supported key types
-------------------
sbctl currently supports storing keys as plain unencrypted files, or as TPM
shielded keys.
Plain unencrypted files (*file*) should only be used when the root partition is
encrypted. This is the default key type for historic reasons. File keys are
hardcoded to RSA 4096.
TPM shielded keys (*tpm*) are shielded inside the TPM and available if there is
an accessible TPM on the system. TPM policies are not supported which means we
can't seal keys towards the system state. Note that TPM keys are hardcoded to
RSA 2048, which is usually the highest bit strength supported by TPMs.
When creating a key hierarchy for Secure Boot, the user can decide which key
type each of the keys in the hierarchy gets. Because TPMs can be slow to sign,
it's generally adviced to keep PK and KEK in the TPM, while the db key can be a
standard *file* key.
Note that password protection is currently not supported.
Landlock
--------
sbctl supports landlock and will attempt to restrict access to filepaths to
where it's needed during execution. Any attempts at establishing network access
is also restricted.
This feature can be disabled by setting **landlock: false** in the configuration
file, or by passing **--disable-landlock** to sbctl.
Option ROM
----------
See https://github.com/Foxboron/sbctl/wiki/FAQ#option-rom
Usage
-----
'Note': To use custom Secure Boot keys it's important to reboot into firmware setup
(`systemctl reboot --firmware-setup`) and navigate into the 'Secure Boot' menu to
enter 'Setup Mode'. This is normally achieved by deleting/clearing the secure boot keys
(or at a minimum the Platform Key) while leaving secure boot mode enabled. Some firmwares
have a 'Custom Mode' which only disables signature verification and should therefore
not be enabled unless no other way to enter key management is provided.
If this step is not completed, enrolling custom keys will be rejected by the firmware.
Next is creating the keys for secure boot. 'create-keys' creates the key
hierarchy needed for secure boot into "/var/lib/sbctl/keys".
# sbctl create-keys
Created Owner UUID a9fbbdb7-a05f-48d5-b63a-08c5df45ee70
Creating secure boot keys...✔
Secure boot keys created!
Next up is enrolling the keys into the efi firmware. *sbctl* supports doing this
on a live system instead of having to boot or run a key management tool from the
UEFI shell.
'Note': This can fail because of firmware issues and unique options in the
machine BIOS menu. Also, some devices have hardware firmware that is signed and
validated when Secure Boot is enabled. Failing to validate this firmware could
brick devices. It's recommended to enroll your own keys with Microsoft
certificates using the '-m' option. See **Option ROM*** above.
# sbctl enroll-keys
Enrolling keys to EFI variables...✔
Enrolled keys to the EFI variables!
After we have successfully enrolled the keys, we need to sign our current
boot chain. Traditionally on UEFI systems one can have an EFI System Partition
('ESP') on '/efi', '/boot' or '/boot/efi'. One can usually find the correct one by
looking at mount points or finding the 'EFI' directory on the ESP.
The most important file to sign is the kernel. This location differs between
distributions but can usually be found on the ESP or /boot. We use '--save' to
store the file path, so we don't need to manually sign it later.
Note that *sbctl* can only keep track of file paths. On versioned kernels this
might prove tricky.
# sbctl sign --save /efi/vmlinuz-linux
✔ Signed /efi/vmlinuz-linux
Next is to sign the bootloader. This can usually be found on the standard path
below, but might differ between installations.
# sbctl sign --save /efi/EFI/BOOT/BOOTX64.EFI
✔ Signed /efi/EFI/BOOT/BOOTX64.EFI
*sbctl* is able to find and verify the ESP, along with any saved files to verify
we have signed the files we need.
# sbctl verify
Verifying file database and EFI images in /efi...
✔ /efi/EFI/BOOT/BOOTX64.EFI is signed
✔ /efi/vmlinuz-linux is signed
Once we have confirmed everything works, we can reboot. Once we have logged back
in, we can verify the state of the system. There should be no need to re-enable
Secure Boot or enter User Mode in the firmware.
$ sbctl status
Installed: ✓ sbctl is installed
Owner GUID: a7b893cc-949d-408c-b5cc-6e7d0370fdb6
Setup Mode: ✓ Disabled
Secure Boot: ✓ Enabled
When we do a system update, we can run 'sign-all' to resign all the saved files
from earlier.
# sbctl sign-all
File has already been signed /boot/vmlinuz-linux
✓ Signed /efi/EFI/BOOT/BOOTX64.EFI
sbctl supports creating unified kernel images. These UEFI executables bundles
the initramfs, kernel and cmdline into one executable which can be signed for
secure boot. This allows you to authenticate larger parts of the bootchain
instead of only signing the kernel.
# sbctl bundle -i /boot/intel-ucode.img
-l /usr/share/systemd/bootctl/splash-arch.bmp
-k /boot/vmlinuz-linux
-f /boot/initramfs-linux-lts.img
-c /etc/kernel/cmdline
/efi/EFI/Linux/linux-linux.efi
Note that linkman:dracut[8] and linkman:mkinitcpio[8] supports unified kernel
features, and they should be preferred over the sbctl implementation. It is
mostly provided in the cases where this feature is not supported by the
initramfs generator of the distribution.
Notes
-----
All commands that take path arguments convert them into absolute paths when
saving them to the database.
Exit status
-----------
On success, 0 is returned, a non-zero failure code otherwise.
Environment variables
---------------------
**SYSTEMD_ESP_PATH**, **ESP_PATH**::
Defines the EFI system partition (ESP) location. This overrides the
behaviour from **sbctl** where we query for the correct partition with
**lsblk**. No checks are performed on this path and can be usefull for testing
purposes.
**SBCTL_UNICODE**::
If this value is "0" sbctl will replace the unicode symbols to equivalent
ascii ones. The default value is assumed to be 1.
Files
----
**/etc/sbctl/sbctl.conf**:;
Defautl configuration file.
See linkman:sbctl.conf[5]
**/var/lib/sbctl**::
Default storage directory.
**/var/lib/sbctl/GUID**::
Owner identification. This is a randomly generated UUID.
**/var/lib/sbctl/files.db**::
Contains a list of EFI binaries to be signed by the generated key.
**/var/lib/sbctl/bundles.db**::
Contains a list of EFI bundles to be generated.
**/var/lib/sbctl/keys/db/db.{pem,key}**::
Contains the Signature Database key used for signing EFI binaries.
**/var/lib/sbctl/keys/KEK/KEK.{pem,key}**::
Contains the Key Exchange Key.
**/var/lib/sbctl/keys/PK/PK.{pem,key}**::
Contains the Platform Key.
**/var/lib/sbctl/keys/custom/KEK/***::
Contains custom certificates which will be added to the firmware as
additional Key Exchange Keys.
**/var/lib/sbctl/keys/custom/db/***::
Contains custom certificates which will be added to the firmware
Signature Database.
See Also
--------
linkman:bootctl[1]
linkman:jq[1]
linkman:sbctl.conf[5]
linkman:landlock[7]
Authors
-------
* Morten Linderud <morten@linderud.pw>
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