This repo is for review of requests for signing shim. To create a request for review:
- clone this repo (preferably fork it)
- 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 it 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.
Hint: check the docs directory in this repo for guidance on submission and getting your shim signed.
Here's the template:
Organization name and website:
Viasat UK Ltd. is a subsidiary of global communications company Viasat Inc.
https://www.viasat.com/defense
The reviewers should be able to easily verify, that your organization is a legal entity, to prevent abuse. Provide the information, which can prove the genuineness with certainty.
Company/tax register entries or equivalent:
(a link to the organization entry in your jurisdiction's register will do)
NASDAQ: VSAT. https://www.nasdaq.com/market-activity/stocks/vsat
The public details of both your organization and the issuer in the EV certificate used for signing .cab files at Microsoft Hardware Dev Center File Signing Services.
(not the CA certificate embedded in your shim binary)
Example:
Issuer: O=MyIssuer, Ltd., CN=MyIssuer EV Code Signing CA
Subject: C=XX, O=MyCompany, Inc., CN=MyCompany, Inc.
Issuer: O=Sectigo Limited, CN=Sectigo Public Code Signing CA EV R.36, C=GB
Subject: C=US, S=California, O=Viasat, Inc., CN=Viasat, Inc.
Viasat Data-At-Rest Cryptography Solid State Drive (DARC-SSD).
What's the justification that this really does need to be signed for the whole world to be able to boot it?
Viasat provides secure data protection for government and defence agencies around the world. We have used a Microsoft Secure Boot signed shim since 2016.
Viasat's shim does not load a GRUB2 bootloader or a Linux kernel.
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: SecAlert, Viasat
- Position: Responsible Disclosure
- Email address: [email protected]
- PGP key fingerprint: 1284 0089 74E2 7365 8177 2E28 5C6D 02C9 2AFB 4B25
- See SecAlert_Viasat.asc
- Available on PGP Global Directory.
(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.)
- Name: Customer Support, Viasat
- Position: General Support
- Email address: [email protected]
- PGP key fingerprint: 3FCF 9C5E C75E 930D EE90 525A 8BD1 A937 2266 D44A
- See Customer_Support_Viasat.asc
- Available on PGP Global Directory.
(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.)
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.
Make sure the tarball is correct by verifying your download's checksum with the following ones:
a9452c2e6fafe4e1b87ab2e1cac9ec00 shim-15.8.tar.bz2
cdec924ca437a4509dcb178396996ddf92c11183 shim-15.8.tar.bz2
a79f0a9b89f3681ab384865b1a46ab3f79d88b11b4ca59aa040ab03fffae80a9 shim-15.8.tar.bz2
30b3390ae935121ea6fe728d8f59d37ded7b918ad81bea06e213464298b4bdabbca881b30817965bd397facc596db1ad0b8462a84c87896ce6c1204b19371cd1 shim-15.8.tar.bz2
Make sure that you've verified that your build process uses that file as a source of truth (excluding external patches) and its checksum matches. Furthermore, there's a detached signature as well - check with the public key that has the fingerprint 8107B101A432AAC9FE8E547CA348D61BC2713E9F that the tarball is authentic. Once you're sure, please confirm this here with a simple yes.
A short guide on verifying public keys and signatures should be available in the docs directory.
Yes. See build/CMakeLists.txt.
Hint: If you attach all the patches and modifications that are being used to your application, you can point to the URL of your application here (https://github.com/YOUR_ORGANIZATION/shim-review).
You can also point to your custom git servers, where the code is hosted.
https://github.com/viasat/shim-review
Mention all the external patches and build process modifications, which are used during your building process, that make your shim binary be the exact one that you posted as part of this application.
VENDOR_CERT_FILE=viasatuk.der
- PAE is signed by Viasat UK.
DEFAULT_LOADER=\\\\\\\\\\\\\\\\paex64.efi
- Shim shall load PAE only.
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 disabled.
objdump -p build/data/BOOTX64.EFI | grep DllCharacteristics
DllCharacteristics 00000000
What exact implementation of Secure Boot in GRUB2 do you have? (Either Upstream GRUB2 shim_lock verifier or Downstream RHEL/Fedora/Debian/Canonical-like implementation)
Skip this, if you're not using GRUB2.
No GRUB2 bootloader.
Skip this, if you're not using GRUB2, otherwise make sure these are present and confirm with yes.
- 2020 July - BootHole
- Details: https://lists.gnu.org/archive/html/grub-devel/2020-07/msg00034.html
- CVE-2020-10713
- CVE-2020-14308
- CVE-2020-14309
- CVE-2020-14310
- CVE-2020-14311
- CVE-2020-15705
- CVE-2020-15706
- CVE-2020-15707
- March 2021
- Details: https://lists.gnu.org/archive/html/grub-devel/2021-03/msg00007.html
- CVE-2020-14372
- CVE-2020-25632
- CVE-2020-25647
- CVE-2020-27749
- CVE-2020-27779
- CVE-2021-3418 (if you are shipping the shim_lock module)
- CVE-2021-20225
- CVE-2021-20233
- June 2022
- Details: https://lists.gnu.org/archive/html/grub-devel/2022-06/msg00035.html, SBAT increase to 2
- CVE-2021-3695
- CVE-2021-3696
- CVE-2021-3697
- CVE-2022-28733
- CVE-2022-28734
- CVE-2022-28735
- CVE-2022-28736
- CVE-2022-28737
- November 2022
- Details: https://lists.gnu.org/archive/html/grub-devel/2022-11/msg00059.html, SBAT increase to 3
- CVE-2022-2601
- CVE-2022-3775
- October 2023 - NTFS vulnerabilities
- Details: https://lists.gnu.org/archive/html/grub-devel/2023-10/msg00028.html, SBAT increase to 4
- CVE-2023-4693
- CVE-2023-4692
No GRUB2 bootloader.
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?
Skip this, if you're not using GRUB2, otherwise do you have an entry in your GRUB2 binary similar to:
grub,4,Free Software Foundation,grub,GRUB_UPSTREAM_VERSION,https://www.gnu.org/software/grub/?
No GRUB2 bootloader.
If you had no previous signed shim, say so here. Otherwise a simple yes will do.
No GRUB2 bootloader.
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?
Hint: upstream kernels should have all these applied, but if you ship your own heavily-modified older kernel version, that is being maintained separately from upstream, this may not be the case.
If you are shipping an older kernel, double-check your sources; maybe you do not have all the patches, but ship a configuration, that does not expose the issue(s).
No Linux kernel.
No Linux kernel.
If not, please describe how you ensure that one kernel build does not load modules built for another kernel.
No Linux kernel.
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.
Our embedded certificate is used to verify the PAE binary.
If you are re-using the CA certificate from your last shim binary, you will need to add the hashes of the previous GRUB2 binaries exposed to the CVEs mentioned earlier to vendor_dbx in shim. Please describe your strategy.
This ensures that your new shim+GRUB2 can no longer chainload those older GRUB2 binaries with issues.
If this is your first application or you're using a new CA certificate, please say so here.
No GRUB2 bootloader.
A reviewer should always be able to run docker build . to get the exact binary you attached in your application.
Hint: Prefer using frozen packages for your toolchain, since an update to GCC, binutils, gnu-efi may result in building a shim binary with a different checksum.
If your shim binaries can't be reproduced using the provided Dockerfile, please explain why that's the case, what the differences would be and what build environment (OS and toolchain) is being used to reproduce this build? In this case please write a detailed guide, how to setup this build environment from scratch.
build/build_shim.sh- Installs required packages, invokescmake, and compares the built binarybuild/output/BOOTX64.EFIto the reference binarybuild/data/BOOTX64.EFI.build/build.sh- Invokesbuild_shim.shand pipes output to log fileoutput/build_shim.log.build/CMakeLists.txt- Builds shim twice to compare Viasat shim to Red Hat shim.
If you have Windows 10 with WSL 2 enabled and Python 3 installed, you can run the scripts under setup/. Otherwise, you can follow the steps manually to create a VM to perform the reproducible build and run bash build.sh from build/ inside the VM.
-
setup/vm_0_setup.py- Imports a fresh Ubuntu 24.04.1 LTS into a build VM in WSL 2.- Ubuntu 24.04.1 LTS rootfs
SHA256=a66c7d1db2a64e727d3cd13767ad8c543290abcc1311f2ae0e46dfc49c0c6277
wsl.exe --importrequires at least Windows 10.0.18305.
- Ubuntu 24.04.1 LTS rootfs
-
setup/vm_1_build.py- Imports thebuild/directory into the build VM to perform a reproducible build.- Installs frozen packages:
bsdmainutils=12.1.8cmake=3.28.3-1build7dos2unix=7.5.1-1gcc=4:13.2.0-7ubuntu1g++=4:13.2.0-7ubuntu1git=1:2.43.0-1ubuntu7.1make=4.3-4.1build2pesign=116-7wget=1.21.4-1ubuntu4.1
- Installs frozen packages:
-
setup/vm_2_clean.py- Unregisters and removes the build VM.
Example PowerShell session:
WSL> py -3 .\setup\vm_0_setup.py
wsl.exe --list
Downloading Ubuntu image...
Date Thu, 12 Sep 2024 13:30:28 GMT
Server Apache/2.4.29 (Ubuntu)
Last-Modified Thu, 05 Sep 2024 20:18:37 GMT
ETag "157c692f-62164fee8fb37"
Accept-Ranges bytes
Content-Length 360474927
Connection close
Content-Type application/x-gzip
Verifying Ubuntu image...
Importing Ubuntu image...
wsl.exe --import Ubuntu-Viasat E:\WSL\setup\..\temp\ubuntu-viasat E:\WSL\setup\..\temp\ubuntu-viasat.rootfs.tar.gz
WSL> py -3 .\setup\vm_1_build.py
wsl.exe --list
Importing source ...
wsl.exe -d Ubuntu-Viasat -e cp -r ../build /root
Building shim ...
wsl.exe -d Ubuntu-Viasat --cd /root/build -e bash build.sh
Exporting output ...
wsl.exe -d Ubuntu-Viasat -e cp -r /root/build/output/ ../buildThis should include logs for creating the buildroots, applying patches, doing the build, creating the archives, etc.
logs/build_shim.log- Reproducible build.logs/viasat-shim-build.log- Viasat shim build.
For example, signing new kernel's variants, UKI, systemd-boot, new certs, new CA, etc..
Skip this, if this is your first application for having shim signed.
Update shim to address #682.
ad18f6eb26fff69de7d162967512ac3af5accdb9dbbae52152fc76b4a8f8a255
Describe the security strategy that is used for key protection. This can range from using hardware tokens like HSMs or Smartcards, air-gapped vaults, physical safes to other good practices.
The private key is stored on a hardware token with restricted access.
A yes or no will do. There's no penalty for the latter.
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 )?
Hint: The history of SBAT and more information on how it works can be found here. That document is large, so for just some examples check out SBAT.example.md
If you are using a downstream implementation of GRUB2 (e.g. from Fedora or Debian), make sure you have their SBAT entries preserved and that you append your own (don't replace theirs) to simplify revocation.
Remember to post the entries of all the binaries. Apart from your bootloader, you may also be shipping e.g. a firmware updater, which will also have these.
Hint: run objcopy --only-section .sbat -O binary YOUR_EFI_BINARY /dev/stdout to get these entries. Paste them here. Preferably surround each listing with three backticks (```), so they render well.
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.viasat,2,Viasat UK,shim,15.8,mailto:[email protected]
PAE:
sbat,1,SBAT Version,sbat,1,https://github.com/rhboot/shim/blob/main/SBAT.md
viasat.pae,1,Viasat UK,pae,2.0.0,mailto:[email protected]
Skip this, if you're not using GRUB2.
Hint: this is about those modules that are in the binary itself, not the .mod files in your filesystem.
No GRUB2 bootloader.
If you are using systemd-boot on arm64 or riscv, is the fix for unverified Devicetree Blob loading included?
No systemd-boot bootloader.
Our PAE application is proprietary.
If your shim launches any other components apart from your bootloader, please provide further details on what is launched.
Hint: The most common case here will be a firmware updater like fwupd.
The SHIM launches our Pre-Authentication Environment (PAE) application which allows an authenticated user to administer and boot Viasat DARC-SSDs. It does not allow the loading and execution of further code.
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.
Skip this, if you're not using GRUB2 or systemd-boot.
No GRUB2 or systemd-boot bootloader.
Summarize in one or two sentences, how your secure bootchain works on higher level.
The integrity of the PAE is verified with a digital signature by the SHIM.
Does your shim load any loaders that support loading unsigned kernels (e.g. certain GRUB2 configurations)?
No.
No Linux kernel.
The reviewing process is meant to be a peer-review effort and the best way to have your application reviewed faster is to help with reviewing others. We are in most cases volunteers working on this venue in our free time, rather than being employed and paid to review the applications during our business hours.
A reasonable timeframe of waiting for a review can reach 2-3 months. Helping us is the best way to shorten this period. The more help we get, the faster and the smoother things will go.
For newcomers, the applications labeled as easy to review are recommended to start the contribution process.
We hope the instructions provided to perform a reproducible build without a Dockerfile are acceptable.
None.