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This repo is for review of requests for signing shim. To create a request for review:

  • clone this repo
  • edit the template below
  • add the shim.efi to be signed
  • add build logs
  • add any additional binaries/certificates/SHA256 hashes that may be needed
  • commit all of that
  • tag it with a tag of the form "myorg-shim-arch-YYYYMMDD"
  • push that to github
  • file an issue at https://github.com/rhboot/shim-review/issues with a link to your tag
  • approval is ready when the "accepted" label is added to your issue

Note that we really only have experience with using GRUB2 or systemd-boot on Linux, so asking us to endorse anything else for signing is going to require some convincing on your part.

Check the docs directory in this repo for guidance on submission and getting your shim signed.

Here's the template:

What organization or people are asking to have this signed?

Certus Software S.R.L.

What product or service is this for?

Certus Erasure (https://www.certus.software/en/certus-erasure-for-storage-devices/)

What's the justification that this really does need to be signed for the whole world to be able to boot it?

The main reason for this is to easier the effort of Certus Erasure user when booting the software products on machines where he needs to securely remove the data from the attached storage devices. The most affected users are the technicians working with the ITAD companies which are required to remove the data stored on a great amount of machines, on a daily basis.

Why are you unable to reuse shim from another distro that is already signed?

Reusing the shim of another distribution would also require reusing the grub and kernel. We have to build our own kernel.

Who is the primary contact for security updates, etc.?

The security contacts need to be verified before the shim can be accepted. For subsequent requests, contact verification is only necessary if the security contacts or their PGP keys have changed since the last successful verification.

An authorized reviewer will initiate contact verification by sending each security contact a PGP-encrypted email containing random words. You will be asked to post the contents of these mails in your shim-review issue to prove ownership of the email addresses and PGP keys.

  • Name: Eduard Acatrinei
  • Position: Software Engineer
  • Email address: [email protected]
  • PGP key fingerprint: EduardAcatrinei.pub

(Key should be signed by the other security contacts, pushed to a keyserver like keyserver.ubuntu.com, and preferably have signatures that are reasonably well known in the Linux community.)

Who is the secondary contact for security updates, etc.?

  • Name: Adrian Parfene
  • Position: Engineering Manager
  • Email address: [email protected]
  • PGP key fingerprint: AdrianParfene.pub

(Key should be signed by the other security contacts, pushed to a keyserver like keyserver.ubuntu.com, and preferably have signatures that are reasonably well known in the Linux community.)

Were these binaries created from the 15.8 shim release tar?

Please create your shim binaries starting with the 15.8 shim release tar file: https://github.com/rhboot/shim/releases/download/15.8/shim-15.8.tar.bz2

This matches https://github.com/rhboot/shim/releases/tag/15.8 and contains the appropriate gnu-efi source.

We confirm that our shim binaries are built from the referenced tarball.

URL for a repo that contains the exact code which was built to get this binary:

https://github.com/rhboot/shim/releases/tag/15.8

What patches are being applied and why:

None.

Do you have the NX bit set in your shim? If so, is your entire boot stack NX-compatible and what testing have you done to ensure such compatibility?

See https://techcommunity.microsoft.com/t5/hardware-dev-center/nx-exception-for-shim-community/ba-p/3976522 for more details on the signing of shim without NX bit.

Not set.

If shim is loading GRUB2 bootloader what exact implementation of Secureboot in GRUB2 do you have? (Either Upstream GRUB2 shim_lock verifier or Downstream RHEL/Fedora/Debian/Canonical-like implementation)

Using upstream GRUB2 with shim_lock verifier.

If shim is loading GRUB2 bootloader and your previously released shim booted a version of GRUB2 affected by any of the CVEs in the July 2020, the March 2021, the June 7th 2022, the November 15th 2022, or 3rd of October 2023 GRUB2 CVE list, have fixes for all these CVEs been applied?

Yes.

If shim is loading GRUB2 bootloader, and if these fixes have been applied, is the upstream global SBAT generation in your GRUB2 binary set to 4?

The entry should look similar to: grub,4,Free Software Foundation,grub,GRUB_UPSTREAM_VERSION,https://www.gnu.org/software/grub/

Yes.

Were old shims hashes provided to Microsoft for verification and to be added to future DBX updates?

Does your new chain of trust disallow booting old GRUB2 builds affected by the CVEs?

We don't have previeus signed shim without SBAT (first signed is 15.7). Grub2 is only loaded by SHIM, which checks against SBAT entries.

If your boot chain of trust includes a Linux kernel:

Is upstream commit 1957a85b0032a81e6482ca4aab883643b8dae06e "efi: Restrict efivar_ssdt_load when the kernel is locked down" applied?

Is upstream commit 75b0cea7bf307f362057cc778efe89af4c615354 "ACPI: configfs: Disallow loading ACPI tables when locked down" applied?

Is upstream commit eadb2f47a3ced5c64b23b90fd2a3463f63726066 "lockdown: also lock down previous kgdb use" applied?

Yes.

Do you build your signed kernel with additional local patches? What do they do?

Yes, we are building our signed kernel with the below described additional patches:

  • aufs-standalone, AUFS adds file system multilayer unification support.
  • linux-t2-patches, These patches provide hardware support and compatibility improvements for MacBooks with the T2 chip, things that are not yet available in the upstream kernel.
  • linux-surface, These patches provide hardware support and compatibility improvements for Microsoft Surface devices, things that are not yet available in the upstream kernel.

Do you use an ephemeral key for signing kernel modules?

If not, please describe how you ensure that one kernel build does not load modules built for another kernel.

Yes, we do use ephemeral keys for every kernel build.

If you use vendor_db functionality of providing multiple certificates and/or hashes please briefly describe your certificate setup.

If there are allow-listed hashes please provide exact binaries for which hashes are created via file sharing service, available in public with anonymous access for verification.

We do not use this functionality.

If you are re-using a previously used (CA) certificate, you will need to add the hashes of the previous GRUB2 binaries exposed to the CVEs to vendor_dbx in shim in order to prevent GRUB2 from being able to chainload those older GRUB2 binaries. If you are changing to a new (CA) certificate, this does not apply.

Please describe your strategy.

Our GRUB2 binaries, which are signed by us, are not exposed to CVEs.

What OS and toolchain must we use to reproduce this build? Include where to find it, etc. We're going to try to reproduce your build as closely as possible to verify that it's really a build of the source tree you tell us it is, so these need to be fairly thorough. At the very least include the specific versions of gcc, binutils, and gnu-efi which were used, and where to find those binaries.

If the shim binaries can't be reproduced using the provided Dockerfile, please explain why that's the case and what the differences would be.

docker build . --no-cache

Which files in this repo are the logs for your build?

This should include logs for creating the buildroots, applying patches, doing the build, creating the archives, etc.

build_log.txt

What changes were made in the distor's secure boot chain since your SHIM was last signed?

For example, signing new kernel's variants, UKI, systemd-boot, new certs, new CA, etc..

Last signed Certus SHIM is 15.7 based, this update rebased against 15.8, no other changes.

What is the SHA256 hash of your final SHIM binary?

3be5b56b64d4e37391899eacd34c3773c1fd87fa97ddb5080880d135001cc366

How do you manage and protect the keys used in your SHIM?

Keys are stored in a FIPS 140-2 certified HW token provided by Certification Authorities.

Do you use EV certificates as embedded certificates in the SHIM?

Yes.

Do you add a vendor-specific SBAT entry to the SBAT section in each binary that supports SBAT metadata ( GRUB2, fwupd, fwupdate, systemd-boot, systemd-stub, shim + all child shim binaries )?

Please provide exact SBAT entries for all SBAT binaries you are booting or planning to boot directly through shim.

Where your code is only slightly modified from an upstream vendor's, please also preserve their SBAT entries to simplify revocation.

If you are using a downstream implementation of GRUB2 or systemd-boot (e.g. from Fedora or Debian), please preserve the SBAT entry from those distributions and only append your own. More information on how SBAT works can be found here.

Yes.

shim SBAT:

sbat,1,SBAT Version,sbat,1,https://github.com/rhboot/shim/blob/main/SBAT.md
shim,4,UEFI shim,shim,1,https://github.com/rhboot/shim
shim.certus,1,Certus Software S.R.L.,shim,15.8,mail:[email protected]

grub SBAT:

sbat,1,SBAT Version,sbat,1,https://github.com/rhboot/shim/blob/main/SBAT.md
grub,4,Free Software Foundation,grub,2.06,https://www.gnu.org/software/grub/
grub.debian,5,Debian,grub2,2.06-13+deb12u1,https://tracker.debian.org/pkg/grub2
grub.certus,1,Certus Software S.R.L.,grub2,2.06-13+deb12u1,mail:[email protected]

If shim is loading GRUB2 bootloader, which modules are built into your signed GRUB2 image?

iso9660 linux normal search efi_gop efi_uga all_video gfxmenu linuxefi gfxterm gfxterm_background tftp http efinet font png jpeg chain

If you are using systemd-boot on arm64 or riscv, is the fix for unverified Devicetree Blob loading included?

Currently, we do not use shim for these architectures.

What is the origin and full version number of your bootloader (GRUB2 or systemd-boot or other)?

2.06-13+deb12u1 from https://salsa.debian.org/grub-team/grub/-/tree/debian/2.06-13+deb12u1/debian

If your SHIM launches any other components, please provide further details on what is launched.

N/A

If your GRUB2 or systemd-boot launches any other binaries that are not the Linux kernel in SecureBoot mode, please provide further details on what is launched and how it enforces Secureboot lockdown.

N/A

How do the launched components prevent execution of unauthenticated code?

Our shim launches grub2 built with secure-boot support.

Does your SHIM load any loaders that support loading unsigned kernels (e.g. GRUB2)?

It launched grub, nothing else.

What kernel are you using? Which patches does it includes to enforce Secure Boot?

Kernel 6.1.38 and has secure boot enabled(CONFIG_LOCK_DOWN_IN_EFI_SECURE_BOOT).

Add any additional information you think we may need to validate this shim.

We have updated the GRUB2 to include additional modules for PXE boot. We've bumped the sbat entry for grub.debian (shim revocations).

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