linux-kernel - Re: [PATCH v6 00/13] Enroll kernel keys thru MOK

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Message-ID: <bee0ebc354a651ea5b263897f9b155dc604fa7c5.camel@kernel.org>
Date:   Wed, 15 Sep 2021 20:57:39 +0300
From:   Jarkko Sakkinen <jarkko@...nel.org>
To:     Eric Snowberg <eric.snowberg@...cle.com>, keyrings@...r.kernel.org,
        linux-integrity@...r.kernel.org, zohar@...ux.ibm.com,
        dhowells@...hat.com, dwmw2@...radead.org,
        herbert@...dor.apana.org.au, davem@...emloft.net,
        jmorris@...ei.org, serge@...lyn.com
Cc:     keescook@...omium.org, gregkh@...uxfoundation.org,
        torvalds@...ux-foundation.org, scott.branden@...adcom.com,
        weiyongjun1@...wei.com, nayna@...ux.ibm.com, ebiggers@...gle.com,
        ardb@...nel.org, nramas@...ux.microsoft.com, lszubowi@...hat.com,
        linux-kernel@...r.kernel.org, linux-crypto@...r.kernel.org,
        linux-security-module@...r.kernel.org,
        James.Bottomley@...senPartnership.com, pjones@...hat.com,
        konrad.wilk@...cle.com
Subject: Re: [PATCH v6 00/13] Enroll kernel keys thru MOK

On Tue, 2021-09-14 at 17:14 -0400, Eric Snowberg wrote:
> Back in 2013 Linus requested a feature to allow end-users to have the 
> ability "to add their own keys and sign modules they trust". This was
> his *second* order outlined here [1]. There have been many attempts 
> over the years to solve this problem, all have been rejected.  Many 
> of the failed attempts loaded all preboot firmware keys into the kernel,
> including the Secure Boot keys. Many distributions carry one of these 
> rejected attempts [2], [3], [4]. This series tries to solve this problem 
> with a solution that takes into account all the problems brought up in 
> the previous attempts.
> 
> On UEFI based systems, this series introduces a new Linux kernel keyring 
> containing the Machine Owner Keys (MOK) called machine. It also defines
> a new MOK variable in shim. This variable allows the end-user to decide 
> if they want to load MOK keys into the machine keyring. Mimi has suggested 
> that only CA keys contained within the MOK be loaded into the machine 
> keyring. All other certs will load into the platform keyring instead.
> 
> By default, nothing changes; MOK keys are not loaded into the machine
> keyring.  They are only loaded after the end-user makes the decision 
> themselves.  The end-user would set this through mokutil using a new 
> --trust-mok option [5]. This would work similar to how the kernel uses 
> MOK variables to enable/disable signature validation as well as use/ignore 
> the db. Any kernel operation that uses either the builtin or secondary 
> trusted keys as a trust source shall also reference the new machine 
> keyring as a trust source.
> 
> Secure Boot keys will never be loaded into the machine keyring.  They
> will always be loaded into the platform keyring.  If an end-user wanted 
> to load one, they would need to enroll it into the MOK.
> 
> Steps required by the end user:
> 
> Sign kernel module with user created key:
> $ /usr/src/kernels/$(uname -r)/scripts/sign-file sha512 \
>    machine_signing_key.priv machine_signing_key.x509 my_module.ko
> 
> Import the key into the MOK
> $ mokutil --import machine_signing_key.x509
> 
> Setup the kernel to load MOK keys into the .machine keyring
> $ mokutil --trust-mok
> 
> Then reboot, the MokManager will load and ask if you want to trust the
> MOK key and enroll the MOK into the MOKList.  Afterwards the signed kernel
> module will load.
> 
> I have included links to both the mokutil [5] and shim [6] changes I
> have made to support this new functionality.

How hard it is to self-compile shim and boot it with QEMU (I
do not know even the GIT location of Shim)?

I'm all my SGX testing already with TianoCore and QEMU so I
thought it might not be that huge stretch to get testing env
for this.

/Jarkko