linux-kernel - Re: [PATCH v4] certs: Add EFI_CERT_X509

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Message-ID: <YBSZ2bfYsUo2Y28i@kernel.org>
Date:   Sat, 30 Jan 2021 01:27:21 +0200
From:   Jarkko Sakkinen <jarkko@...nel.org>
To:     Mimi Zohar <zohar@...ux.ibm.com>
Cc:     David Howells <dhowells@...hat.com>,
        linux-integrity <linux-integrity@...r.kernel.org>,
        Eric Snowberg <eric.snowberg@...cle.com>,
        Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
        dwmw2@...radead.org, herbert@...dor.apana.org.au,
        davem@...emloft.net, jmorris@...ei.org, serge@...lyn.com,
        nayna@...ux.ibm.com, erichte@...ux.ibm.com, mpe@...erman.id.au,
        keyrings@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-crypto@...r.kernel.org,
        linux-security-module@...r.kernel.org,
        James.Bottomley@...senpartnership.com
Subject: Re: [PATCH v4] certs: Add EFI_CERT_X509_GUID support for dbx entries

On Wed, Jan 27, 2021 at 09:03:59AM -0500, Mimi Zohar wrote:
> [Cc'ing linux-integrity]
> 
> On Wed, 2021-01-27 at 11:46 +0000, David Howells wrote:
> > Jarkko Sakkinen <jarkko@...nel.org> wrote:
> > 
> > > > I suppose a user space tool could be created. But wouldn’t what is
> > > > currently done in the kernel in this area need to be removed?
> > > 
> > > Right. I don't think this was a great idea in the first place to
> > > do to the kernel but since it exists, I guess the patch does make
> > > sense.
> > 
> > This information needs to be loaded from the UEFI tables before the system
> > starts loading any kernel modules or running any programs (if we do
> > verification of such, which I think IMA can do).
> 
> There needs to a clear distinction between the pre-boot and post-boot
> keys.  UEFI has its own trust model, which should be limited to UEFI. 
> The .platform keyring was upstreamed and limited to verifying the kexec
> kernel image.   Any other usage of the .platform keyring keys is
> abusing its intended purpose.
> 
> The cover letter says,   "Anytime the .platform keyring is used, the
> keys in the .blacklist keyring are referenced, if a matching key is
> found, the key will be rejected."   I don't have a problem with loading
> the UEFI X509 dbx entries as long as its usage is limited to verifying
> the kexec kernel image.
> 
> Mimi

Thanks Mimi, this is a valid argument. I agree.

/Jarkko