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:

quoted

On Tue, 13 Oct 2020 at 18:46, Mimi Zohar [off-list ref] wrote:

quoted

[Cc'ing linuxppc-dev@lists.ozlabs.org]

On Tue, 2020-10-13 at 10:18 +0200, Ard Biesheuvel wrote:

quoted

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 <redacted>
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/ (local)
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 <redacted>

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