From 22f9f3e49580b99176491624000842964f4b7787 Mon Sep 17 00:00:00 2001 From: =?utf8?q?Fabian=20Gr=C3=BCnbichler?= Date: Thu, 23 Nov 2023 10:45:23 +0100 Subject: [PATCH] secure boot: add subsection for DKMS/MOK MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit similar, but a bit more beginner friendly compared to the wiki article. Signed-off-by: Fabian Grünbichler --- system-booting.adoc | 43 +++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 43 insertions(+) diff --git a/system-booting.adoc b/system-booting.adoc index 0cc9c13..511eddf 100644 --- a/system-booting.adoc +++ b/system-booting.adoc @@ -492,3 +492,46 @@ disk as a boot option in the UEFI firmware setup utility and run TIP: To enroll custom keys, see the accompanying https://pve.proxmox.com/wiki/Secure_Boot_Setup#Setup_instructions_for_db_key_variant[Secure Boot wiki page]. + +Using DKMS/third party modules with Secure Boot +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +On systems with Secure Boot enabled, the kernel will refuse to load modules +which are not signed by a trusted key. The default set of modules shipped with +the kernel packages is signed with an ephemeral key embedded in the kernel +image which is trusted by that specific version of the kernel image. + +In order to load other modules, such as those built with DKMS or manually, they +need to be signed with a key trusted by the Secure Boot stack. The easiest way +to achieve this is to enroll them as Machine Owner Key (`MOK`) with `mokutil`. + +The `dkms` tool will automatically generate a keypair and certificate in +`/var/lib/dkms/mok.key` and `/var/lib/dkms/mok.pub` and use it for signing +the kernel modules it builds and installs. + +You can view the certificate contents with + +---- +# openssl x509 -in /var/lib/dkms/mok.pub -noout -text +---- + +and enroll it on your system using the following command: + +---- +# mokutil --import /var/lib/dkms/mok.pub +input password: +input password again: +---- + +The `mokutil` command will ask for a (temporary) password twice, this password +needs to be entered one more time in the next step of the process! Rebooting +the system should automatically boot into the `MOKManager` EFI binary, which +allows you to verify the key/certificate and confirm the enrollment using the +password selected when starting the enrollment using `mokutil`. Afterwards, the +kernel should allow loading modules built with DKMS (which are signed with the +enrolled `MOK`). The `MOK` can also be used to sign custom EFI binaries and +kernel images if desired. + +The same procedure can also be used for custom/third-party modules not managed +with DKMS, but the key/certificate generation and signing steps need to be done +manually in that case. -- 2.39.2