linux-kernel - Re: [PATCH v2 5/7] efi/capsule: Prepare for loading images with security header

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Message-ID: <a3d4da19-015d-0559-f837-550631f1d491@siemens.com>
Date:   Tue, 28 Mar 2017 17:13:15 +0200
From:   Jan Kiszka <jan.kiszka@...mens.com>
To:     Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Matt Fleming <matt@...eblueprint.co.uk>
Cc:     "linux-efi@...r.kernel.org" <linux-efi@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        "Bryan O'Donoghue" <pure.logic@...us-software.ie>,
        Hock Leong Kweh <hock.leong.kweh@...el.com>,
        Borislav Petkov <bp@...en8.de>,
        Sascha Weisenberger <sascha.weisenberger@...mens.com>
Subject: Re: [PATCH v2 5/7] efi/capsule: Prepare for loading images with
 security header

On 2017-03-28 15:49, Ard Biesheuvel wrote:
> On 24 March 2017 at 17:34, Jan Kiszka <jan.kiszka@...mens.com> wrote:
>> The Quark security header is nicely located in front of the capsule
>> image, but we still need to pass the image to the update service as if
>> there was none. Prepare efi_capsule_update and its user for this by
>> defining and evaluating a EFI header displacement in the image located
>> in memory. For standard-conforming capsules, this displacement is 0.
>>
>> Signed-off-by: Jan Kiszka <jan.kiszka@...mens.com>
> 
> Hello Jan,
> 
> Thanks for taking the time to respin this.
> 
> I played around with these patches a bit (I can't really test them
> since I don't have the hardware), and I am not really happy with the
> non-trivial changes to the generic code, only to allow a header
> displacement.
> 
> So instead, I attempted to come up with an alternative which does not
> use a displacement field, but makes the core capsule routines work
> with a copy of the capsule header rather than mandating that it exists
> at the start of the buffer. This way, we can override the code that
> performs the copy, and make it originate from somewhere else.
> 
> Could you please have a look at
> 
> https://git.kernel.org/pub/scm/linux/kernel/git/ardb/linux.git/log/?h=quark-capsule
> 
> and tell me if that would work for you? I will send them out for
> proper review in any case, but to avoid confusion (if I missed
> something obvious), I don't want to send them out just yet.

There is more needed to make things work again, maybe around passing the
right image size. I'm looking into this.

Another observation: Making EFI_CAPSULE_QUIRK_QUARK_CSH select
EFI_CAPSULE_LOADER technically resolves the problem that the platform
code would otherwise need something from a capsule loader module.
However, a logical configuration would rather make the quirk depend on
the loader, wouldn't it? But I'm fine with both.

Thanks,
Jan

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