Re: [PATCH 1/3] integrity: Make arch_ima_get_secureboot integrity-wide

[Mimi Zohar <zohar@linux.ibm.com>]

On Fri, 2026-01-16 at 18:27 +0100, Ard Biesheuvel wrote:
> On Fri, 16 Jan 2026 at 17:39, Mimi Zohar <zohar@linux.ibm.com> wrote:
> > 
> > On Fri, 2026-01-16 at 14:18 +0100, Ard Biesheuvel wrote:
> > > On Fri, 16 Jan 2026 at 14:11, Mimi Zohar <zohar@linux.ibm.com> wrote:
> > > > 
> > > > On Fri, 2026-01-16 at 10:41 +0100, Ard Biesheuvel wrote:
> > > > > On Thu, 15 Jan 2026 at 01:43, Coiby Xu <coxu@redhat.com> wrote:
> > > > > > 
> > > > > > EVM and other LSMs need the ability to query the secure boot status of
> > > > > > the system, without directly calling the IMA arch_ima_get_secureboot
> > > > > > function. Refactor the secure boot status check into a general,
> > > > > > integrity-wide function named arch_integrity_get_secureboot.
> > > > > > 
> > > > > > Define a new Kconfig option CONFIG_INTEGRITY_SECURE_BOOT, which is
> > > > > > automatically configured by the supported architectures. The existing
> > > > > > IMA_SECURE_AND_OR_TRUSTED_BOOT Kconfig loads the architecture specific
> > > > > > IMA policy based on the refactored secure boot status code.
> > > > > > 
> > > > > > Reported-and-suggested-by: Mimi Zohar <zohar@linux.ibm.com>
> > > > > > Suggested-by: Roberto Sassu <roberto.sassu@huaweicloud.com>
> > > > > > Signed-off-by: Coiby Xu <coxu@redhat.com>
> > > > > > ---
> > > > > >  arch/arm64/Kconfig                            |  1 +
> > > > > >  arch/powerpc/Kconfig                          |  1 +
> > > > > >  arch/powerpc/kernel/Makefile                  |  2 +-
> > > > > >  arch/powerpc/kernel/ima_arch.c                |  5 --
> > > > > >  arch/powerpc/kernel/integrity_sb_arch.c       | 13 +++++
> > > > > >  arch/s390/Kconfig                             |  1 +
> > > > > >  arch/s390/kernel/Makefile                     |  1 +
> > > > > >  arch/s390/kernel/ima_arch.c                   |  6 --
> > > > > >  arch/s390/kernel/integrity_sb_arch.c          |  9 +++
> > > > > >  arch/x86/Kconfig                              |  1 +
> > > > > >  arch/x86/include/asm/efi.h                    |  4 +-
> > > > > >  arch/x86/platform/efi/efi.c                   |  2 +-
> > > > > >  include/linux/ima.h                           |  7 +--
> > > > > >  include/linux/integrity.h                     |  8 +++
> > > > > >  security/integrity/Kconfig                    |  6 ++
> > > > > >  security/integrity/Makefile                   |  3 +
> > > > > >  security/integrity/efi_secureboot.c           | 56 +++++++++++++++++++
> > > > > >  security/integrity/ima/ima_appraise.c         |  2 +-
> > > > > >  security/integrity/ima/ima_efi.c              | 47 +---------------
> > > > > >  security/integrity/ima/ima_main.c             |  4 +-
> > > > > >  security/integrity/platform_certs/load_uefi.c |  2 +-
> > > > > >  21 files changed, 111 insertions(+), 70 deletions(-)
> > > > > >  create mode 100644 arch/powerpc/kernel/integrity_sb_arch.c
> > > > > >  create mode 100644 arch/s390/kernel/integrity_sb_arch.c
> > > > > >  create mode 100644 security/integrity/efi_secureboot.c
> > > > > > 
> > > > > > diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> > > > > > index 93173f0a09c7..4c265b7386bb 100644
> > > > > > --- a/arch/arm64/Kconfig
> > > > > > +++ b/arch/arm64/Kconfig
> > > > > > @@ -2427,6 +2427,7 @@ config EFI
> > > > > >         select EFI_STUB
> > > > > >         select EFI_GENERIC_STUB
> > > > > >         imply IMA_SECURE_AND_OR_TRUSTED_BOOT
> > > > > > +       imply INTEGRITY_SECURE_BOOT
> > > > > 
> > > > > This allows both to be en/disabled individually, which I don't think
> > > > > is what we want. It also results in more churn across the
> > > > > arch-specific Kconfigs than needed.
> > > > > 
> > > > > Wouldn't it be better if IMA_SECURE_AND_OR_TRUSTED_BOOT 'select'ed
> > > > > INTEGRITY_SECURE_BOOT in its Kconfig definition?
> > > > 
> > > > As much as possible, EVM (and other LSMs) shouldn't be dependent on another LSM,
> > > > in this case IMA, being configured.
> > > 
> > > Sure, but that is not my point.
> > > 
> > > This arrangement allows for IMA_SECURE_AND_OR_TRUSTED_BOOT to be
> > > enabled without INTEGRITY_SECURE_BOOT, resulting in the stub
> > > implementation of arch_integrity_get_secureboot() being used, which
> > > always returns false.
> > 
> > I understand your concern, but instead of "select"ing INTEGRITY_SECURE_BOOT from
> > IMA_SECURE_AND_OR_TRUSTED_BOOT, how making IMA_SECURE_AND_OR_TRUSTED_BOOT
> > dependent on both IMA_ARCH_POLICY and INTEGRITY_SECURE_BOOT.
> > 
> 
> Given that INTEGRITY_SECURE_BOOT has no dependencies of its own,
> afaict, selecting it is the least disruptive option, as otherwise,
> existing configs will disable IMA_SECURE_AND_OR_TRUSTED_BOOT as the
> kernel is being upgraded. But conceptually, I agree that they are
> equivalent.
> 
> > Including the "imply INTEGRITY_SECURE_BOOT" here in the arch Kconfig allows EVM
> > to query the secure boot state without relying on IMA_SECURE_AND_OR_TRUSTED_BOOT
> > being configured.
> 
> Yes, I understand that this is the whole point of the exercise. But
> 'imply' should be used with care, and in this case, implying both from
> CONFIG_EFI really makes little sense. INTEGRITY_SECURE_BOOT should be
> selected by options that need the functionality, not 'implied' by
> options that might provide it.

As not all arch's implement arch_integrity_get_secureboot, the definition in
include/linux/integrity.h would need to be updated.  Something like:

-#ifdef CONFIG_INTEGRITY_SECURE_BOOT
+#if (defined(CONFIG_INTEGRITY_SECURE_BOOT) && \
+       (defined(CONFIG_X86) && defined(CONFIG_EFI)) || defined(CONFIG_S390) \
+        || defined(CONFIG_PPC_SECURE_BOOT))

Then IMA_SECURE_AND_OR_TRUSTED_BOOT and EVM could select INTEGRITY_SECURE_BOOT,
as suggested.

Mimi