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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?

[NComputing Global, Inc. NComputing is a software developer providing secure endpoint solutions for companies and organizations worldwide. https://ncomputing.com ]

What product or service is this for?

[LEAF OS Linux software endpoint solution by NComputing ]

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

[NComputing LEAF OS is a Linux software endpoint solution that transforms any x86-64 PC, laptop, or thin client into a secure and centrally managed endpoint to access popular desktop virtualization environments, including Microsoft Azure Virtual Desktop (AVD), Windows 365 Cloud PC, Microsoft Remote Desktop Services (RDS) and others. LEAF OS solution is available worldwide, covering education, SMB, SME and enterprise customers.

LEAF OS endpoint solution addresses concerns related to security, corporate data leakage, patch management and central manageability for companies with working-from-home and BYOD initiatives using personal devices. A bootable USB memory stick can be created containing LEAF OS. Any x86-64 hardware device can secure boot to LEAF OS and instantly becomes a locked-down LEAF OS thin client.

LEAF OS can be used to repurpose PCs and laptops by converting any x86-64 hardware from a stand-alone computer to a dedicated thin client by installing directly onto an internal hard drive and removing the old system and files. This method extends the usefulness of aging computers using end-of-life operating systems like Windows 7 while giving users powerful up-to-date desktops.

NComputing would like customers to be able to run LEAFOS Linux endpoint on any x86-64 devices without disabling Secure Boot.]

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

[NComputing LEAF OS is deeply customized operating system]

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.

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

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, shim binary will be created from https://github.com/rhboot/shim/releases/tag/15.8 ]

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 the only difference it is built with NComputing Certificate embedded ]

What patches are being applied and why:

[no patches ]

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.

[NX bit is not set in our shim]

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 ]

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?

[We are using upstream GRUB 2.12 which has above CVEs fixed]

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, upstream global SBAT generation in our GRUB2 binary is set to 4]

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?

[ Our new shim does not allow older grub because of upper sbat generation id ]

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?

[we have first 2 upstream commits: 1957a85b0032a81e6482ca4aab883643b8dae06e and 75b0cea7bf307f362057cc778efe89af4c615354. 3rd is not used in our upstream kernel version but CONFIG_DEBUG_KERNEL is not set ]

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

[No local patches]

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, ephemeral key for signing kernel modules is used]

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.

[No vendor_db]

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.

[We changing to a new (CA) certificate. Anyway in future older GRUB2 builds will be disallowed to boot by generation id in SBAT]

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.

[Ubuntu 18.4 or above with Docker, run make-shim.sh ]

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 file is output of make-shim.sh ]

What changes were made in the distro'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..

[New NComputing certificate in shim bootloader, updated grub2 version to 2.12, updated kernel to 6.1.78 or upper ]

What is the SHA256 hash of your final SHIM binary?

[1075d8cee7fac50c87e3b9b10accaed6eaff7514d09122fd7803ece1e3fcbaa0 shimx64.efi]

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 shim binaries as well as all SBAT binaries that shim will directly boot.

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.

[SHIM:
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.ncomputing,1,NComputing Global Inc,shim,15.8,mail:[email protected]

GRUB2:
sbat,1,SBAT Version,sbat,1,https://github.com/rhboot/shim/blob/main/SBAT.md
grub,4,Free Software Foundation,grub,2.12,https//www.gnu.org/software/grub/
grub.ncomputing,1,NComputing Global Inc,grub2,2.12,mail:[email protected]
]

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

[all_video boot linux ext2 fat font squash4 part_msdos part_gpt normal]

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

[No arm64 or RISCV]

1What is the origin and full version number of your bootloader (GRUB2 or systemd-boot or other)?

[ Upstream GRUB2 https://git.savannah.gnu.org/git/grub.git, tag grub-2.12 ]

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

[ shimx64.efi launches only GRUB2, which then launches kernel ]

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.

[ GRUB2 launches kernel only, no other components. GRUB2 verifies signatures of kernel using shim routines. ]

How do the launched components prevent execution of unauthenticated code?

[GRUB2 verifies signatures of kernel using shim routines]

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

[no]

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

[ upstream kernel 6.1.78 which supports SecureBoot ]

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

[]

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