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:
Hedgehog SONiC Foundation (https://githedgehog.com/)
We want to use the signed shim for booting:
- Hedgehog SONiC
- Hedgehog ONIE
What's the justification that this really does need to be signed for the whole world to be able to boot it?
Bringing Secure Boot to SONiC capable devices is a major value add that we want to provide with Hedgehog SONiC. Currently there is no open SONiC distribution which would allow an end-user to enable Secure Boot on their switches without using a MOK. Additionally we have yet to encounter an ONIE installation on a switch which is Secure Boot capable. Furthermore this enables for us the use of Hedgehog SONiC and ONIE on both hardware as well as cloud use-cases using the same builds.
Both ONIE as well as SONiC need customized compiled Linux kernels for every different device that we support. In order to uphold the trusted boot chain we need to sign our Linux kernels with the certificate/key which we are going to embed into our shim which we want to submit for signing.
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: Marcus Heese
- Position: Linux Platform Engineer
- Email address: [email protected]
- PGP key fingerprint:
65F20EF3617803DCC5E0C3180A9749F383D6B2A9
(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: Mike Dvorkin
- Position: CTO
- Email address: [email protected]
- PGP key fingerprint:
C2661FA61B891C30E837281976C23BC6495DA313
(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 15.7 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.
Yes, as can be seen in the Dockerfile.
https://github.com/githedgehog/shim-review
All patches that are being applied can be seen in the Dockerfile, and can be found in the shim-patches/ folder in this repository.
All patches are either necessary (like the NX compatibility patch) or are upstream bug fixes which are not part of any official shim release yet.
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)
For both ONIE and SONiC we rely on the Fedora maintained grub2 release. Fedora has its own downstream implementation.
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
N/A. We have no previously released shim. This is our first submission. However, the grub version have these patches applied.
Yes.
Yes.
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.
Both ONIE and SONiC come with a different set of patches per device. This is expected as every switch has a different combination of hardware/ASIC that they need to support.
For SONiC we do not deviate from what is built for the upstream community SONiC distribution. The Linux kernel is based on Debian 11 Bullseye and the patchset can be found at: https://github.com/sonic-net/sonic-linux-kernel/
For ONIE the patches are completely dependent on the platform (= the different switch hardware) and usually related to accessing fans, SFPs, etc. (I2C subsystem).
If not, please describe how you ensure that one kernel build does not load modules built for another kernel.
For ONIE we currently do not build any Linux kernel modules.
For SONiC we build with CONFIG_MODVERSIONS=y.
However, we require that Linux kernel modules must be signed with CONFIG_MODULE_SIG_FORCE=y.
This is a requirement as we cannot always 100% guarantee that we know which kernel modules are needed ahead of time.
We need room to be able to build a kernel module out of tree and ad hoc afterwards.
An ephemeral key would prevent us from doing so.
However, we want to guarantee that only our compiled modules can be loaded and no other modules.
While this does not guarantee that modules from previous/older kernel versions can be loaded, we will roll the Linux kernel module keys when required, for example in cases when an older compiled module could compromise the secure boot functionality.
The key with which we sign Linux kernel modules is secured in the same fashion as the key which is included in our shim (see below).
No other keys are included that are allowed to load Linux kernel modules.
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 at this point in time.
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.
N/A. This is our first submission.
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.
We are using Ubuntu 22.04 as the toolchain for building the shim.
The build can be fully reproduced with the attached Dockerfile.
In fact it was used to generate the submitted shim binaries to begin with.
This should include logs for creating the buildroots, applying patches, doing the build, creating the archives, etc.
You can find the build logs in the build-x86_64.log file for the x64 build and the build-arm64.log file for the aa64 build of this repository.
It is an executed run of the docker image from the Dockerfile as executed by the Makefile.
N/A. This is our first submission and we have not yet a shim signed.
SHA-256 sum of shimx64.efi:
f43357e978b690aaef58b53de9e898105230d45cc825a4fb8ef996e577e8c541 artifacts/shimx64.efi
SHA-256 sum of shimaa64.efi:
c9cb5349cb38fb3e6305a8beab75b2bab498057f1b8a1f0589f473f7859d760c artifacts/shimaa64.efi
The keys which are used in our shim reside on an HSM. We have a backup HSM which has the same keys. And we also have an encrypted offline backup of the keys. There is only one authentication key for the HSM which can use the keys for signing operation which can only be achieved through our CI system on a tagged release (git tag).
No.
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.
shim:
sbat,1,SBAT Version,sbat,1,https://github.com/rhboot/shim/blob/main/SBAT.md
shim,3,UEFI shim,shim,1,https://github.com/rhboot/shim
shim.hedgehog,1,Hedgehog SONiC Foundation,shim,15.7,https://github.com/githedgehog/shim-review
grub:
sbat,1,SBAT Version,sbat,1,https://github.com/rhboot/shim/blob/main/SBAT.md
grub,3,Free Software Foundation,grub,2.06,https//www.gnu.org/software/grub/
grub.rh,2,Red Hat,grub2,2.06-94.fc37,mailto:[email protected]
grub.hedgehog,1,Hedgehog SONiC Foundation,grub,2.06,https://github.com/githedgehog/grub-build
We are building separate grub images for ONIE and SONiC.
The built-in modules for ONIE are (merger of upstream ONIE grub modules and Fedora modules plus the version module):
- all_video
- archelp
- at_keyboard
- backtrace
- blscfg
- boot
- btrfs
- bufio
- cat
- chain
- configfile
- connectefi
- crypto
- cryptodisk
- echo
- efi_gop
- efi_netfs
- efi_uga
- efifwsetup
- efinet
- ext2
- f2fs
- fat
- font
- fshelp
- gcry_dsa
- gcry_rijndael
- gcry_rsa
- gcry_serpent
- gcry_sha1
- gcry_sha256
- gcry_sha512
- gcry_twofish
- gcry_whirlpool
- gettext
- gfxmenu
- gfxterm
- gfxterm_background
- gzio
- halt
- hfsplus
- http
- increment
- is_sb_enabled
- iso9660
- jpeg
- keylayouts
- keystatus
- linux
- loadenv
- loopback
- lsefi
- lsefimmap
- lsefisystab
- lssal
- luks
- luks2
- lvm
- mdraid09
- mdraid1x
- memdisk
- minicmd
- net
- normal
- part_apple
- part_gpt
- part_msdos
- password_pbkdf2
- pgp
- png
- raid5rec
- raid6rec
- reboot
- regexp
- search
- search_fs_file
- search_fs_uuid
- search_label
- serial
- sleep
- squash4
- syslinuxcfg
- terminal
- terminfo
- test
- tftp
- tpm
- true
- usb
- usbserial_common
- usbserial_ftdi
- usbserial_pl2303
- usbserial_usbdebug
- version
- video
- xfs
- zfs
- zfscrypt
- zfsinfo
- zstd
The buil-in modules for SONiC are (upstream Fedora modules, plus the is_sb_enabled and version modules):
- all_video
- at_keyboard
- backtrace
- blscfg
- boot
- btrfs
- cat
- chain
- configfile
- connectefi
- cryptodisk
- echo
- efi_netfs
- efifwsetup
- efinet
- ext2
- f2fs
- fat
- font
- gcry_rijndael
- gcry_rsa
- gcry_serpent
- gcry_sha256
- gcry_twofish
- gcry_whirlpool
- gfxmenu
- gfxterm
- gzio
- halt
- hfsplus
- http
- increment
- is_sb_enabled
- iso9660
- jpeg
- keylayouts
- linux
- loadenv
- loopback
- lsefi
- lsefimmap
- luks
- luks2
- lvm
- mdraid09
- mdraid1x
- memdisk
- minicmd
- net
- normal
- part_apple
- part_gpt
- part_msdos
- password_pbkdf2
- pgp
- png
- reboot
- regexp
- search
- search_fs_file
- search_fs_uuid
- search_label
- serial
- sleep
- squash4
- syslinuxcfg
- test
- tftp
- tpm
- usb
- usbserial_common
- usbserial_ftdi
- usbserial_pl2303
- usbserial_usbdebug
- version
- video
- xfs
- zstd
Our grub builds are done in: https://github.com/githedgehog/grub-build
It is based on Fedora grub from: https://src.fedoraproject.org/rpms/grub2.git
The version number as shown by the internal version command:
GRUB version 2.06
Platform x86_64-efi
RPM package version 2.06-94.fc37
Compiler version 12.2.1 20221121 (Red Hat 12.2.1-4)
GRUB version 2.06
Platform arm64-efi
RPM package version 2.06-94.fc37
Compiler version 12.2.1 20221121 (Red Hat 12.2.1-4)
It does not launch any other components.
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.
Grub launches only the Linux kernel in SecureBoot mode or it chainloads to another grub. From the SONiC grub boot menu the user is able to chainload into the grub of ONIE when he needs to perform an ONIE function. The chainloading will in fact chainload to the signed shim which will load grub again.
Fedora's grub verifies signatures of kernels via the shim protocol. It includes a set of common secure boot patches to achieve that. Additionally the ONIE grub includes a PGP key with which all grub configuration, Linux kernel and initramfs files are signed. When the system is in Secure Boot mode it requires the signatures. Additionally it requires a password when in Secure Boot mode in order to shell out in grub or to edit a command line.
All our signed Linux kernels either have all necessary lockdown patches dervived from the upstream Linux kernel or have them applied separately where necessary.
No.
As mentioned above we need to use different kernel versions and patches for every different device that we support. That means that we are going to apply patches for ACPI and lockdown so that signed kernel module loading is enforced when in secure boot mode if the upstream Linux kernel does not already have them applied.
For SONiC the Linux kernel is based on the Linux kernel from Debian 11 Bullseye - which is currently at 5.10.179.
For ONIE we are trying to base the Linux kernel on the latest vanilla 6.1 release (6.1.44 at the time of writing). However, not all required patches for all platforms (= different switch hardware) work on Linux kernel 6.1 just yet, in which case we need to work with an older Linux version.