linux-kernel - Re: [PATCH 4/5] MODSIGN: checking the blacklisted hash before loading a kernel module

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Date:   Tue, 13 Mar 2018 10:18:35 -0700
From:   James Bottomley <James.Bottomley@...senPartnership.com>
To:     "Lee, Chun-Yi" <joeyli.kernel@...il.com>,
        David Howells <dhowells@...hat.com>
Cc:     linux-fs@...r.kernel.org, linux-efi@...r.kernel.org,
        linux-kernel@...r.kernel.org, "Lee, Chun-Yi" <jlee@...e.com>,
        Josh Boyer <jwboyer@...oraproject.org>
Subject: Re: [PATCH 4/5] MODSIGN: checking the blacklisted hash before
 loading a kernel module

On Tue, 2018-03-13 at 18:38 +0800, Lee, Chun-Yi wrote:
> This patch adds the logic for checking the kernel module's hash
> base on blacklist. The hash must be generated by sha256 and enrolled
> to dbx/mokx.
> 
> For example:
> 	sha256sum sample.ko
> 	mokutil --mokx --import-hash $HASH_RESULT
> 
> Whether the signature on ko file is stripped or not, the hash can be
> compared by kernel.

What's the use case for this?  We're already in trouble from the ODMs
for the size of dbx and its consumption of the extremely limited
variable space, so do we really have a use case for adding module
blacklist hashes to the UEFI variables given the space constraints (as
in one we can't do any other way)?

James