Re: [PATCH v2] ima: defer arch_ima_get_secureboot() call to IMA init time

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

On Wed, 2020-10-14 at 17:35 +0800, Chester Lin wrote:
> Hi Ard & Mimi,
> 
> On Tue, Oct 13, 2020 at 06:59:21PM +0200, Ard Biesheuvel wrote:
> > On Tue, 13 Oct 2020 at 18:46, Mimi Zohar <zohar@linux.ibm.com> wrote:
> > >
> > > [Cc'ing linuxppc-dev@lists.ozlabs.org]
> > >
> > > On Tue, 2020-10-13 at 10:18 +0200, Ard Biesheuvel wrote:
> > > > Chester reports that it is necessary to introduce a new way to pass
> > > > the EFI secure boot status between the EFI stub and the core kernel
> > > > on ARM systems. The usual way of obtaining this information is by
> > > > checking the SecureBoot and SetupMode EFI variables, but this can
> > > > only be done after the EFI variable workqueue is created, which
> > > > occurs in a subsys_initcall(), whereas arch_ima_get_secureboot()
> > > > is called much earlier by the IMA framework.
> > > >
> > > > However, the IMA framework itself is started as a late_initcall,
> > > > and the only reason the call to arch_ima_get_secureboot() occurs
> > > > so early is because it happens in the context of a __setup()
> > > > callback that parses the ima_appraise= command line parameter.
> > > >
> > > > So let's refactor this code a little bit, by using a core_param()
> > > > callback to capture the command line argument, and deferring any
> > > > reasoning based on its contents to the IMA init routine.
> > > >
> > > > Cc: Chester Lin <clin@suse.com>
> > > > Cc: Mimi Zohar <zohar@linux.ibm.com>
> > > > Cc: Dmitry Kasatkin <dmitry.kasatkin@gmail.com>
> > > > Cc: James Morris <jmorris@namei.org>
> > > > Cc: "Serge E. Hallyn" <serge@hallyn.com>
> > > > Link: https://lore.kernel.org/linux-arm-kernel/20200904072905.25332-2-clin@suse.com/
> > > > Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
> > > > ---
> > > > v2: rebase onto series 'integrity: improve user feedback for invalid bootparams'
> > >
> > > Thanks, Ard.  Based on my initial, limited testing on Power, it looks
> > > good, but I'm hesistant to include it in the integrity 5.10 pull
> > > request without it having been in linux-next and some additional
> > > testing.  It's now queued in the next-integrity-testing branch awaiting
> > > some tags.
> > >
> 
> Tested-by: Chester Lin <clin@suse.com>
> 
> I have tested this patch on x86 VM.
> 
> * System configuration:
>   - Platform: QEMU/KVM
>   - Firmware: EDK2/OVMF + secure boot enabled.
>   - OS: SLE15-SP2 + SUSE's kernel-vanilla (=linux v5.9) + the follow commits
>     from linux-next and upstream:
>     * [PATCH v2] ima: defer arch_ima_get_secureboot() call to IMA init time
>       https://www.spinics.net/lists/linux-efi/msg20645.html
>     * e4d7e2df3a09 "ima: limit secure boot feedback scope for appraise"
>     * 7fe2bb7e7e5c "integrity: invalid kernel parameters feedback"
>     * 4afb28ab03d5 "ima: add check for enforced appraise option"
> 
> * Logs with UEFI secure boot enabled:
> 
>   [    0.000000] Linux version 5.9.0-858-g865c50e1d279-1.g8764d18-vanilla (geeko@b
>   uildhost) (gcc (SUSE Linux) 10.2.1 20200825 [revision c0746a1beb1ba073c7981eb09f
>   55b3d993b32e5c], GNU ld (GNU Binutils; openSUSE Tumbleweed) 2.34.0.20200325-1) #
>   1 SMP Wed Oct 14 04:00:11 UTC 2020 (8764d18)
>   [    0.000000] Command line: BOOT_IMAGE=/boot/vmlinuz-5.9.0-858-g865c50e1d279-1.
>   g8764d18-vanilla root=UUID=5304c03e-4d8a-4d67-873a-32a32e57cdeb console=ttyS0,11
>   5200 resume=/dev/disk/by-path/pci-0000:04:00.0-part4 mitigations=auto ignore_log
>   level crashkernel=192M,high crashkernel=72M,low ima_appraise=off
>   [    0.000000] x86/fpu: Supporting XSAVE feature 0x001: 'x87 floating point regi
>   sters'
>   [    0.000000] x86/fpu: Supporting XSAVE feature 0x002: 'SSE registers'
>   [    0.000000] x86/fpu: Supporting XSAVE feature 0x004: 'AVX registers'
>   ....
>   ....
>   [    1.720309] ima: Secure boot enabled: ignoring ima_appraise=off option
>   [    1.720314] ima: No TPM chip found, activating TPM-bypass!
>   [    1.722129] ima: Allocated hash algorithm: sha256


Thank you for testing the options aren't being set in secure boot mode.
My main concern, however, is that IMA doesn't go into TPM-bypass mode. 
Does this system have a TPM?

Mimi