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 on Linux, so asking us to endorse anything else for signing is going to require some convincing on your part.

Here's the template:

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What organization or people are asking to have this signed?

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System76.

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What product or service is this for?

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Pop OS.

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

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Having a shim with the System76 Secure Boot database certificate will allow Pop OS to be booted on systems with Secure Boot enabled and the Microsoft third party UEFI certificate installed.

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

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Pop OS, though based on Ubuntu, uses a different bootloader (systemd-boot) and a customized Linux kernel, both being built on Pop OS infrastructure:

• https://github.com/pop-os/systemd/
• https://github.com/pop-os/linux/

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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.

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• Name: Jeremy Soller
• Position: Principal Engineer
• Email address: jeremy@system76.com
• PGP key fingerprint: DA08 78FC F806 089E D4FD DF58 E988 B49E E78A 7FB1

(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.)

This key can be found on keyserver.ubuntu.com: https://keyserver.ubuntu.com/pks/lookup?search=DA0878FCF806089ED4FDDF58E988B49EE78A7FB1&fingerprint=on&op=index

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

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• Name: Tim Crawford
• Position: Kernel Engineer
• Email address: tcrawford@system76.com
• PGP key fingerprint: 9495 B69D CFA3 D043 3C65 53A8 68E5 58D2 BBD8 56E3

(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.)

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Were these binaries created from the 15.7 shim release tar?

Please create your shim binaries starting with the 15.7 shim release tar file: https://github.com/rhboot/shim/releases/download/15.7/shim-15.7.tar.bz2

This matches https://github.com/rhboot/shim/releases/tag/15.7 and contains the appropriate gnu-efi source.

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Yes, these binaries were created from the tag with no changes, as can be seen in the Dockerfile.

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

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https://github.com/system76/shim-review/releases/tag/system76-shim-x86_64-20230131

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What patches are being applied and why:

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No patches have been applied.

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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)

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Shim is loading systemd-boot.

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If shim is loading GRUB2 bootloader and your previously released shim booted a version of grub affected by any of the CVEs in the July 2020 grub2 CVE list, the March 2021 grub2 CVE list, the June 7th 2022 grub2 CVE list, or the November 15th 2022 list, have fixes for all these CVEs been applied?

• CVE-2020-14372

• CVE-2020-25632

• CVE-2020-25647

• CVE-2020-27749

• CVE-2020-27779

• CVE-2021-20225

• CVE-2021-20233

• CVE-2020-10713

• CVE-2020-14308

• CVE-2020-14309

• CVE-2020-14310

• CVE-2020-14311

• CVE-2020-15705

• CVE-2021-3418 (if you are shipping the shim_lock module)

• CVE-2021-3695

• CVE-2021-3696

• CVE-2021-3697

• CVE-2022-28733

• CVE-2022-28734

• CVE-2022-28735

• CVE-2022-28736

• CVE-2022-28737

• CVE-2022-2601

• CVE-2022-3775

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Shim is loading systemd-boot.

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If these fixes have been applied, have you set the global SBAT generation on your GRUB binary to 3?

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Shim is loading systemd-boot.

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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?

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Shim is loading systemd-boot. If there is ever a vulnerability impacting Secure Boot signed by us, we will submit hashes as necessary for DBX inclusion.

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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?

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All of these commits are applied.

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

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We minimize patches from the upstream kernel and work to ship stable upstream kernels as soon as they pass our quality assurance tests. Our changes as of the 6.0 and 6.1 kernel series are limited to enabling audio quirks for devices we ship (prior to those quirks being accepted upstream), backporting security fixes (such as CVE-2023-0179), and minor changes to improve device support. All of these changes are carefully checked to ensure they do not change security critical code, and most changes are submitted upstream.

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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.

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We do not use this functionality.

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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.

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We have not signed any GRUB2 binaries.

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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.

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Ubuntu 22.04, as specified in the Dockerfile.

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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.

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See build.log for the build log.

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What changes were made since your SHIM was last signed?

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We have not had previous SHIM versions signed.

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What is the SHA256 hash of your final SHIM binary?

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c2f68d9214792d6e76901a287f01a8befea760ca1ec82b13f2b3c9f19bda52a4

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

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The "System76 Secure Boot Database Key" included in our SHIM is stored in Amazon Web Services Key Management Storage (AWS KMS), and the ability to sign binaries is limited to one user account. This user account is logged in via awscli on a physically secure system we use only for signing the result of systemd and Linux builds for Pop OS.

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

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No.

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Do you add a vendor-specific SBAT entry to the SBAT section in each binary that supports SBAT metadata ( grub2, fwupd, fwupdate, 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.

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Yes. The SHIM SBAT data can be seen in sbat.csv. We will add SBAT data to any binaries we sign for use with this SHIM.

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Which modules are built into your signed grub image?

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We use systemd-boot.

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What is the origin and full version number of your bootloader (GRUB or other)?

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Currently, systemd-boot version 249.11-0ubuntu3.6pop0167407407722.04~d0333cb, as built from https://github.com/pop-os/systemd/commit/d0333cb493888d26e682074391fb8f6b181fe1e4.

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

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We may in the future launch fwupd's EFI binary with SHIM.

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If your GRUB2 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.

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We use systemd-boot. It will not be able to launch other binaries than the Linux kernel as signed by us and potentially fwupd. Neither of these should compromize Secure Boot lockdown.

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How do the launched components prevent execution of unauthenticated code?

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systemd-boot only executes binaries signed for Secure Boot when that is enabled. Fwupd only executes signed capsule updates.

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

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No.

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

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Linux 6.0 or later. We have no specific patches to enforce Secure Boot and rely on upstream for any such support.

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

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