linux-kernel - Re: [PATCH v3 0/2] ima: make appraisal state runtime dependent on secure boot

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Message-ID: <20200626144631.GC2702@glitch>
Date:   Fri, 26 Jun 2020 11:46:31 -0300
From:   Bruno Meneguele <bmeneg@...hat.com>
To:     linux-integrity@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     zohar@...ux.ibm.com, erichte@...ux.ibm.com, nayna@...ux.ibm.com
Subject: Re: [PATCH v3 0/2] ima: make appraisal state runtime dependent on
 secure boot

Gentle ping for review.

I also forgot to add the changelog for the patch, please see below.

On Tue, Jun 23, 2020 at 05:26:38PM -0300, Bruno Meneguele wrote:
> To switch APPRAISE_BOOTPARAM and ARCH_POLICY dependency from compile time to
> run time the secure boot checking code (specific to each arch) had to be
> slightly modified to include, in the PowerPC arch, the Trusted Boot state,
> which is also relevant to the arch policy choice and also required the
> ima_appraise to be enforced. 
> 
> With that I changed the checking order: instead of first check the
> arch_policy and then the secure/trusted boot state, now we first check the
> boot state, set ima_appraise to be enforced and then the existence of arch
> policy. In other words, whenever secure/trusted boot is enabled,
> (ima_appraise & IMA_APPRAISE_ENFORCE) == true.
> 
> I've tested these patches in a x86_64 platform with and without secure boot
> enabled and in a PowerPC without secure boot enabled:
> 
> 1) with secure boot enabled (x86_64) and ima_policy=appraise_tcb, the
> ima_appraise= options were completly ignored and the boot always failed with
> "missing-hash" for /sbin/init, which is the expected result;
> 
> 2) with secure boot enabled (x86_64), but no ima_policy:
> 
> [    1.396111] ima: Allocated hash algorithm: sha256
> [    1.424025] ima: setting IMA appraisal to enforced
> [    1.424039] audit: type=1807 audit(1592927955.557:2): action=measure func=KEXEC_KERNEL_CHECK res=1
> [    1.424040] audit: type=1807 audit(1592927955.557:3): action=measure func=MODULE_CHECK res=1
> 
> 3) with secure boot disabled (PowerPC and x86_64) and
> "ima_policy=appraise_tcb ima_appraise=fix", audit messages were triggered
> with "op=appraisal_data cause=missing-hash" but the system worked fine due
> to "fix".

Changelog:

v2:
  - pr_info() message prefix correction
v3:
  - extend secure boot arch checker to also consider trusted boot
  - enforce IMA appraisal when secure boot is effectively enabled (Nayna)
  - fix ima_appraise flag assignment by or'ing it (Mimi)

> 
> Bruno Meneguele (2):
>   arch/ima: extend secure boot check to include trusted boot
>   ima: move APPRAISE_BOOTPARAM dependency on ARCH_POLICY to runtime
> 
>  arch/powerpc/kernel/ima_arch.c      |  5 +++--
>  arch/s390/kernel/ima_arch.c         |  2 +-
>  arch/x86/kernel/ima_arch.c          |  4 ++--
>  include/linux/ima.h                 |  4 ++--
>  security/integrity/ima/Kconfig      |  2 +-
>  security/integrity/ima/ima_main.c   |  2 +-
>  security/integrity/ima/ima_policy.c | 20 ++++++++++++++------
>  7 files changed, 24 insertions(+), 15 deletions(-)
> 
> -- 
> 2.26.2
> 

-- 
bmeneg 
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