Re: [PATCH] ima: add a new CONFIG for loading arch-specific policies

Ard Biesheuvel
2020-03-02T14:52:22Z

On Mon, 2 Mar 2020 at 15:48, Mimi Zohar <zohar@linux.ibm.com> wrote:
>
> On Wed, 2020-02-26 at 14:10 -0500, Nayna Jain wrote:
> > Every time a new architecture defines the IMA architecture specific
> > functions - arch_ima_get_secureboot() and arch_ima_get_policy(), the IMA
> > include file needs to be updated. To avoid this "noise", this patch
> > defines a new IMA Kconfig IMA_SECURE_AND_OR_TRUSTED_BOOT option, allowing
> > the different architectures to select it.
> >
> > Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
> > Signed-off-by: Nayna Jain <nayna@linux.ibm.com>
> > Cc: Ard Biesheuvel <ardb@kernel.org>
> > Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
> > Cc: Philipp Rudo <prudo@linux.ibm.com>
> > Cc: Michael Ellerman <mpe@ellerman.id.au>
> > ---
> > arch/powerpc/Kconfig | 2 +-
> > arch/s390/Kconfig | 1 +
> > arch/x86/Kconfig | 1 +
> > include/linux/ima.h | 3 +--
> > security/integrity/ima/Kconfig | 9 +++++++++
> > 5 files changed, 13 insertions(+), 3 deletions(-)
> >
> > diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
> > index 497b7d0b2d7e..b8ce1b995633 100644
> > --- a/arch/powerpc/Kconfig
> > +++ b/arch/powerpc/Kconfig
> > @@ -246,6 +246,7 @@ config PPC
> > select SYSCTL_EXCEPTION_TRACE
> > select THREAD_INFO_IN_TASK
> > select VIRT_TO_BUS if !PPC64
> > + select IMA_SECURE_AND_OR_TRUSTED_BOOT if PPC_SECURE_BOOT
> > #
> > # Please keep this list sorted alphabetically.
> > #
> > @@ -978,7 +979,6 @@ config PPC_SECURE_BOOT
> > prompt "Enable secure boot support"
> > bool
> > depends on PPC_POWERNV
> > - depends on IMA_ARCH_POLICY
> > help
> > Systems with firmware secure boot enabled need to define security
> > policies to extend secure boot to the OS. This config allows a user
> > diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
> > index 8abe77536d9d..90ff3633ade6 100644
> > --- a/arch/s390/Kconfig
> > +++ b/arch/s390/Kconfig
> > @@ -195,6 +195,7 @@ config S390
> > select ARCH_HAS_FORCE_DMA_UNENCRYPTED
> > select SWIOTLB
> > select GENERIC_ALLOCATOR
> > + select IMA_SECURE_AND_OR_TRUSTED_BOOT
> >
> >
> > config SCHED_OMIT_FRAME_POINTER
> > diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> > index beea77046f9b..cafa66313fe2 100644
> > --- a/arch/x86/Kconfig
> > +++ b/arch/x86/Kconfig
> > @@ -230,6 +230,7 @@ config X86
> > select VIRT_TO_BUS
> > select X86_FEATURE_NAMES if PROC_FS
> > select PROC_PID_ARCH_STATUS if PROC_FS
> > + select IMA_SECURE_AND_OR_TRUSTED_BOOT if EFI
>
> Not everyone is interested in enabling IMA or requiring IMA runtime
> policies. With this patch, enabling IMA_ARCH_POLICY is therefore
> still left up to the person building the kernel. As a result, I'm
> seeing the following warning, which is kind of cool.
>
> WARNING: unmet direct dependencies detected for
> IMA_SECURE_AND_OR_TRUSTED_BOOT
> Depends on [n]: INTEGRITY [=y] && IMA [=y] && IMA_ARCH_POLICY [=n]
> Selected by [y]:
> - X86 [=y] && EFI [=y]
>
> Ard, Michael, Martin, just making sure this type of warning is
> acceptable before upstreaming this patch. I would appreciate your
> tags.
>

Ehm, no, warnings like these are not really acceptable. It means there
is an inconsistency in the way the Kconfig dependencies are defined.

Does this help:

select IMA_SECURE_AND_OR_TRUSTED_BOOT if EFI && IMA_ARCH_POLICY

?

>
> >
> > config INSTRUCTION_DECODER
> > def_bool y
> > diff --git a/include/linux/ima.h b/include/linux/ima.h
> > index 1659217e9b60..aefe758f4466 100644
> > --- a/include/linux/ima.h
> > +++ b/include/linux/ima.h
> > @@ -30,8 +30,7 @@ extern void ima_kexec_cmdline(const void *buf, int size);
> > extern void ima_add_kexec_buffer(struct kimage *image);
> > #endif
> >
> > -#if (defined(CONFIG_X86) && defined(CONFIG_EFI)) || defined(CONFIG_S390) \
> > - || defined(CONFIG_PPC_SECURE_BOOT)
> > +#ifdef CONFIG_IMA_SECURE_AND_OR_TRUSTED_BOOT
> > extern bool arch_ima_get_secureboot(void);
> > extern const char * const *arch_get_ima_policy(void);
> > #else
> > diff --git a/security/integrity/ima/Kconfig b/security/integrity/ima/Kconfig
> > index 3f3ee4e2eb0d..d17972aa413a 100644
> > --- a/security/integrity/ima/Kconfig
> > +++ b/security/integrity/ima/Kconfig
> > @@ -327,3 +327,12 @@ config IMA_QUEUE_EARLY_BOOT_KEYS
> > depends on IMA_MEASURE_ASYMMETRIC_KEYS
> > depends on SYSTEM_TRUSTED_KEYRING
> > default y
> > +
> > +config IMA_SECURE_AND_OR_TRUSTED_BOOT
> > + bool
> > + depends on IMA
> > + depends on IMA_ARCH_POLICY
> > + default n
> > + help
> > + This option is selected by architectures to enable secure and/or
> > + trusted boot based on IMA runtime policies.
>
>
>
>