linux-kernel - Re: [PATCH v8 4/4] kexec, KEYS, s390: Make use of built-in and secondary keyring for signature verification

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Date:   Thu, 16 Jun 2022 09:46:50 +0800
From:   Coiby Xu <coxu@...hat.com>
To:     Mimi Zohar <zohar@...ux.ibm.com>
Cc:     Baoquan He <bhe@...hat.com>,
        Michal Suchánek <msuchanek@...e.de>,
        Heiko Carstens <hca@...ux.ibm.com>, akpm@...ux-foundation.org,
        kexec@...ts.infradead.org, keyrings@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        Dave Young <dyoung@...hat.com>, Will Deacon <will@...nel.org>,
        "Eric W . Biederman" <ebiederm@...ssion.com>,
        Chun-Yi Lee <jlee@...e.com>, stable@...r.kernel.org,
        Philipp Rudo <prudo@...ux.ibm.com>,
        linux-security-module@...r.kernel.org,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Alexander Gordeev <agordeev@...ux.ibm.com>,
        Christian Borntraeger <borntraeger@...ux.ibm.com>,
        Sven Schnelle <svens@...ux.ibm.com>,
        Martin Schwidefsky <schwidefsky@...ibm.com>,
        "open list:S390" <linux-s390@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>,
        linux-integrity <linux-integrity@...r.kernel.org>,
        Jarkko Sakkinen <jarkko@...nel.org>
Subject: Re: [PATCH v8 4/4] kexec, KEYS, s390: Make use of built-in and
 secondary keyring for signature verification

Hi Mimi,

>> >
>> > This patch set could probably go through KEYS/KEYRINGS_INTEGRITY, but
>> > it's kind of late to be asking.  Has it been in linux-next?  Should I
>> > assume this patch set has been fully tested or can we get some "tags"?
>>
[...]
>>
>> IIRC, Coiby has tested it on x86_64/arm64, not sure if he took test on
>> s390. No, this hasn't been in linux-next.

For arm64, recently I did a new round of test and the patches works as
expected,
   1. Build 5.19.0-rc2
   2. generate keys and add them to .secondary_trusted_keys, MOK, UEFI
      db; 
   3. sign different kernel images with different keys including keys
      from .builtin_trusted_key, .secondary_trusted_keys keyring, UEFI db
      key and MOK key 
   4. Without lockdown, all kernel images can be kexec'ed; with lockdown
      enabled, only the kernel image signed by the key from
      .builtin_trusted_key can be kexec'ed

Then I build a new kernel with the patches applied and confirm all
kernel images can be kexec'ed.

>
>I used the s390 code on powerpc and there it did not work because the
>built-in key was needed to verify the kernel.
>
>I did not really run this on s390, only ported the fix I needed on
>powerpc back to s390.

For 390, I commented out the code that skips signature verification
when secure boot is not enabled since I couldn't find a machine that
supports secure boot and confirm before applying the patch, kernel
images signed by keys from .builtin_trusted_key, .secondary_trusted_keys
couldn't be kexec'ed when lockdown is enabled; after applying the
patch, those kernel images could be kexec'ed. 

>
>Thanks
>
>Michal
>

-- 
Best regards,
Coiby