Re: [PATCH v2 00/21] Appended Signature Secure Boot Support for PowerPC

[sudhakar <sudhakar@linux.ibm.com>]

Hi Marta,

Thanks Martha, yes that would be very helpful and I appreciate your 
consideration for that. Yes the patch-set is getting reviewed actively 
so I am also hopeful that these would be upstreamed soon.

Thanks,
Sudhakar Kuppusamy


On 2025-05-13 19:46, Marta Lewandowska wrote:
> Red Hat has been carrying patches 1-13 of this set for like four
> years now. We would be willing to test the remainder, with the hope
> that at least those first 13 will get accepted sometime soon. Is that
> reasonable? thanks, marta On Wed, Mar
> 
> 
> Red Hat has been carrying patches 1-13 of this set for like four years
> now. We would be willing to test the remainder, with the hope that at
> least those first 13 will get accepted sometime soon. Is that
> reasonable?
> 
> thanks,
> marta
> 
> On Wed, Mar 26, 2025 at 8:33 PM Sudhakar Kuppusamy
> <sudhakar@linux.ibm.com> wrote:
> 
>> This patch set contains v2 of the consolidated version of the patch
>> sets for secure boot using appended signatures on powerpc,
>> rebased on top of git HEAD.
>> 
>> The v1 series is at
>> https://lists.gnu.org/archive/html/grub-devel/2024-12/msg00071.html
>> 
>> Linux on Power LPAR secure boot ensures the integrity of the Linux
>> boot
>> stack. The hypervisor and partition firmware are part of the core
>> root of
>> trust. The partition firmware verifies the signature on the GRUB
>> image
>> before handing control to GRUB. Similarly, GRUB verifies the
>> signature on
>> the kernel image before booting the OS. This ensures that every
>> image
>> running at the boot time is verified and trusted. UEFI platforms
>> relies
>> on PECOFF based signature scheme. Since Power is not a UEFI
>> platform, an
>> alternative mechanism is needed. Power already uses appended
>> signatures
>> on the Linux Kernel, and is now extended to sign the grub as well.
>> 
>> Linux on Power also allows multiple signers, and if any one of the
>> signature passes, then the image passes the validation. Appended
>> signature
>> scheme uses CMS structure to contain signatures. On Power, the
>> multiple
>> signature support relies on the multiple signers features already
>> supported
>> by CMS standards. It does require that all the signers should sign
>> at the
>> same time and are not allowed to add or remove the signatures
>> randomly.
>> 
>> By default, Linux LPAR secure boot uses static key management[1].
>> This means
>> that each image embeds the keys it needs to verify the image it
>> loads.
>> For example, the keys used to verify the GRUB image are built into
>> the
>> firmware image. Similarly, the keys used for verifying the kernel
>> image
>> are built into the GRUB image. These are pre-defined keys and they
>> cannot
>> be modified at runtime. The drawback of this approach is that key
>> rotations
>> results in both firmware and OS updates. This is where dynamic key
>> management is useful.
>> 
>> An admin can switch from static keys to dynamic keys by coordinating
>> with
>> Hardware Management Console(HMC) admin and enabling the required
>> flags
>> for the given LPAR.
>> 
>> The dynamic key management relies on the Platform KeyStore(PKS)[2]
>> storage
>> allocation for each LPAR with individually managed access controls
>> to
>> store sensitive information securely. Once switched to dynamic keys,
>> HMC
>> advertises this flag to the PowerVM, which then initializes the PKS
>> with the default secvars. It also creates a variable SB_VERSION that
>> represents the secure boot key management mode. The default secvars
>> are
>> used by Partition firmware, grub and the linux kernel to reads keys
>> for
>> verification. These secvars can be managed by user interface exposed
>> via
>> linux kernel. The linux kernel already supports this interface and
>> it is available in the upstream kernel.
>> 
>> This patchset adds the appended signature support both for signing
>> and
>> verification and the key management to the grub component. The whole
>> patchset can be split into following four main parts:
>> 
>> The series has following four main parts:
>> 
>> 1.) Sign grub.elf with an appended signature. (Patches 1 - 3)
>> 
>> These patches provide some infrastructure and documentation for
>> signing grub's core.elf with a Linux-kernel-module style appended
>> signature.
>> 
>> An appended signature is a 'dumb' signature over the contents of a
>> file. (It is distinct from schemes like Authenticode that are aware
>> of
>> the structure of the file and only sign certain parts.) The
>> signature
>> is wrapped in a PKCS#7 message, and is appended to the signed file
>> along with some metadata and a magic string. The signatures are
>> validated against a public key which is usually provided as an x509
>> certificate.
>> 
>> Because some platforms, such as powerpc-ieee1275, may load grub from
>> a
>> raw disk partition rather than a filesystem, we extend grub-install
>> to
>> add an ELF note that allows us to specify the size and location of
>> the
>> signature.
>> 
>> 2.) Enable appended signature verification using builtin keys
>> (Patches 4 - 10).
>> 
>> Part of a secure boot chain is allowing grub to verify the boot
>> kernel. For UEFI platforms, this is usually delegated to the
>> shim. However, for platforms that do not implement UEFI, an
>> alternative scheme is required.
>> 
>> This part teaches grub how to verify Linux kernel-style appended
>> signatures. Kernels on powerpc are already signed with this scheme
>> and
>> can be verified by IMA for kexec.
>> 
>> As PKCS#7 messages and x509 certificates are both based on ASN.1, we
>> import libtasn1 to parse them. Because ASN.1 isn't self-documenting,
>> we import from GNUTLS the information we need to navigate their
>> structure.
>> 
>> This section is composed of the following patches:
>> 
>> - patch 4 is a small fix to allow persistent modules to work on the
>> emu target.
>> 
>> - patches 5 and 6 are small refactorings.
>> 
>> - patch 7 allows x509 certificates to be built in to the grub core
>> in much the same way as PGP keys.
>> 
>> - patch 8 brings in the code from GNUTLS that allows us to parse
>> PKCS#7 and x509 with libtasn1.
>> 
>> - patch 9 is our PKCS#7 and x509 parser. They're minimal and fairly
>> strict parsers that extract only the bits we need to verify the
>> signatures.
>> 
>> - patch 10 is the guts of the appended signature verifier. It uses
>> the verifier infrastructure like pgp, and adds a number of
>> user-friendly commands that mirror the pgp module.
>> 
>> - patch 11 adds tests, and patch 12 adds documentation.
>> 
>> 3.) Enable lockdown if secure boot is enabled (Patch 13)
>> 
>> If the 'ibm,secure-boot' property of the root node is 2 or greater,
>> enter lockdown.The main appended signature module now tests for
>> lockdown to
>> enter 'forced' mode.
>> 
>> 4.) Enable accessing keys dynamically from Platform KeyStore (Patch
>> 14 - 21)
>> 
>> This part teaches grub how to read db and dbx variables from
>> platform keystore
>> using client interface call then load keys from those two variable,
>> and use it
>> to verify Linux kernel.
>> 
>> This section is composed of the following patches:
>> 
>> - patch 14 is an exposes an interface in ieee1275 for reading
>> secure boot
>> variable
>> db and dbx from Platform Keystore.
>> 
>> - patch 15 is a read secure boot variables such as db and dbx from
>> PKS and
>> extract certificates from ESL.
>> 
>> - patch 16 is creates the trusted and distrusted lists.
>> 
>> - patch 17 is verify the kernel using trusted and distrusted lists
>> 
>> - patch 18 sets the use_static_keys flag if DB not available in
>> PKS,
>> and patch 19  is reads the DB default keys from ELF Note and
>> store it in trusted lists if use_static_keys flag is set.
>> 
>> - patch 20 adds trusted and distrusted commands, and patch 21 adds
>> documentation.
>> 
>> Thanks to Stefan Berger, Avnish Chouhan, Michal Suchanek, and
>> Vladimir Serbinenko for providing review comments on v1.
>> 
>> I've pushed this all to
>> https://github.com/SudhakarKuppusamy1/grub/tree/appendedsig-2.13
>> 
>> 
> [1]https://www.ibm.com/docs/en/linux-on-systems?topic=servers-guest-secure-boot-static-keys
>> 
> [2]https://community.ibm.com/community/user/power/blogs/chris-engel1/2020/11/20/powervm-introduces-the-platform-keystore
>> 
>> Alastair D'Silva (1):
>> grub-install: support embedding x509 certificates
>> 
>> Daniel Axtens (11):
>> docs/grub: Document signing grub under UEFI
>> docs/grub: Document signing grub with an appended signature
>> dl: provide a fake grub_dl_set_persistent for the emu target
>> pgp: factor out rsa_pad
>> crypto: move storage for grub_crypto_pk_* to crypto.c
>> appended signatures: import GNUTLS's ASN.1 description files
>> appended signatures: parse PKCS#7 signedData and X.509
>> certificates
>> appended signatures: support verifying appended signatures
>> appended signatures: verification tests
>> appended signatures: documentation
>> ieee1275: enter lockdown based on /ibm,secure-boot
>> 
>> Rashmica Gupta (1):
>> powerpc-ieee1275: Add support for signing grub with an appended
>> signature
>> 
>> Sudhakar Kuppusamy (8):
>> ieee1275: Platform Keystore (PKS) Support
>> ieee1275: Read the DB and DBX secure boot variables
>> appendedsig: The creation of trusted and distrusted lists
>> appendedsig: While verifying the kernel, use trusted and
>> distrusted
>> lists
>> powerpc_ieee1275: set use_static_keys flag
>> appendedsig: Reads the default DB keys from ELF Note
>> appendedsig: The grub command's trusted and distrusted support
>> appendedsig: documentation
>> 
>> docs/grub.texi                                |  283 +++-
>> grub-core/Makefile.am                         |    2 +
>> grub-core/Makefile.core.def                   |   31 +
>> grub-core/commands/appendedsig/appendedsig.c  | 1411
>> +++++++++++++++++
>> grub-core/commands/appendedsig/appendedsig.h  |  110 ++
>> grub-core/commands/appendedsig/asn1util.c     |   98 ++
>> .../commands/appendedsig/gnutls_asn1_tab.c    |  121 ++
>> grub-core/commands/appendedsig/pkcs7.c        |  460 ++++++
>> .../commands/appendedsig/pkix_asn1_tab.c      |  484 ++++++
>> grub-core/commands/appendedsig/x509.c         |  953 +++++++++++
>> grub-core/commands/pgp.c                      |   34 +-
>> grub-core/kern/file.c                         |   34 +
>> grub-core/kern/ieee1275/init.c                |   46 +
>> grub-core/kern/powerpc/ieee1275/ieee1275.c    |  140 ++
>> .../kern/powerpc/ieee1275/platform_keystore.c |  346 ++++
>> grub-core/lib/crypto.c                        |    4 +
>> grub-core/lib/pkcs1_v15.c                     |   59 +
>> grub-core/term/tparm.c                        |    1 -
>> grub-core/tests/appended_signature_test.c     |  258 +++
>> grub-core/tests/appended_signatures.h         |  975 ++++++++++++
>> grub-core/tests/lib/functional_test.c         |    1 +
>> include/grub/dl.h                             |   11 +
>> include/grub/file.h                           |    3 +
>> include/grub/kernel.h                         |    2 +
>> include/grub/lockdown.h                       |    3 +-
>> include/grub/pkcs1_v15.h                      |   27 +
>> include/grub/powerpc/ieee1275/ieee1275.h      |   14 +
>> .../grub/powerpc/ieee1275/platform_keystore.h |  226 +++
>> include/grub/types.h                          |   11 +
>> include/grub/util/install.h                   |   10 +-
>> include/grub/util/mkimage.h                   |    4 +-
>> util/grub-install-common.c                    |   34 +-
>> util/grub-mkimage.c                           |   25 +-
>> util/grub-mkimagexx.c                         |   38 +-
>> util/mkimage.c                                |   39 +-
>> 35 files changed, 6229 insertions(+), 69 deletions(-)
>> create mode 100644 grub-core/commands/appendedsig/appendedsig.c
>> create mode 100644 grub-core/commands/appendedsig/appendedsig.h
>> create mode 100644 grub-core/commands/appendedsig/asn1util.c
>> create mode 100644 grub-core/commands/appendedsig/gnutls_asn1_tab.c
>> create mode 100644 grub-core/commands/appendedsig/pkcs7.c
>> create mode 100644 grub-core/commands/appendedsig/pkix_asn1_tab.c
>> create mode 100644 grub-core/commands/appendedsig/x509.c
>> create mode 100644 grub-core/kern/powerpc/ieee1275/ieee1275.c
>> create mode 100644
>> grub-core/kern/powerpc/ieee1275/platform_keystore.c
>> create mode 100644 grub-core/lib/pkcs1_v15.c
>> create mode 100644 grub-core/tests/appended_signature_test.c
>> create mode 100644 grub-core/tests/appended_signatures.h
>> create mode 100644 include/grub/pkcs1_v15.h
>> create mode 100644
>> include/grub/powerpc/ieee1275/platform_keystore.h
>> 
>> --
>> 2.43.5
> 
> 
> Links:
> ------
> [1] 
> https://us-phishalarm-ewt.proofpoint.com/EWT/v1/AdhS1Rd-!-XFVHHVa3OJT9VR5Za8gPdRF0zC5n_bZ0RUCAt27UE3C-XDLgiqLMbD2NUoiY_q9qtOF9O7ECQBRONUTavAThgVVsAFD2RS6-fQgO_NzvFzsuKo8HoOFcd8cU0ZJfQ$

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