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

Michael Ellerman
2020-03-02T23:24:05Z

Mimi Zohar <zohar@linux.ibm.com> writes:
> On Mon, 2020-03-02 at 15:52 +0100, Ard Biesheuvel wrote:
>> 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
>>
>> ?
>
> Yes, that's fine for x86.  Michael, Martin, do you want something
> similar or would you prefer actually selecting IMA_ARCH_POLICY?

For powerpc this should be all we need:

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 497b7d0b2d7e..a5cfde432983 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -976,12 +976,13 @@ config PPC_MEM_KEYS

config PPC_SECURE_BOOT
prompt "Enable secure boot support"
bool
depends on PPC_POWERNV
depends on IMA_ARCH_POLICY
+ select IMA_SECURE_AND_OR_TRUSTED_BOOT
help
Systems with firmware secure boot enabled need to define security
policies to extend secure boot to the OS. This config allows a user
to enable OS secure boot on systems that have firmware support for
it. If in doubt say N.

cheers