linux-kernel - Re: [RFC PATCH v2 0/8] Clavis LSM

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Date: Wed, 5 Jun 2024 20:41:27 +0000
From: Eric Snowberg <eric.snowberg@...cle.com>
To: Jarkko Sakkinen <jarkko@...nel.org>
CC: "open list:SECURITY SUBSYSTEM" <linux-security-module@...r.kernel.org>,
        David Howells <dhowells@...hat.com>,
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Subject: Re: [RFC PATCH v2 0/8] Clavis LSM



> On Jun 4, 2024, at 11:59 AM, Jarkko Sakkinen <jarkko@...nel.org> wrote:
> 
> On Fri May 31, 2024 at 3:39 AM EEST, Eric Snowberg wrote:
>> Introduce a new LSM called Clavis (Latin word meaning key).  The motivation
>> behind this LSM is to provide access control for system keys.  Before spending
>> more time on this LSM, I am sending this as an RFC to start a discussion to see
>> if the current direction taken has a possibility of being accepted in the
>> future.
>> 
>> Today the kernel has the following system keyrings: .builtin_trusted_keyring,
>> .secondary_trusted_keyring, and the .machine.  It also has the .platform
>> keyring which has limited capabilities; it can only be used to verify a kernel
>> for kexec.
> 
> Would be nice to have a reminder of applications for secondary keyrings
> use cases of today [1]. It is not entirely clear for me, given that I
> need personally just the builtin and machine keyring. This is not the
> same as saying that it would not be useful, but it would clarity to
> scope it a bit in the current state of the art.
> 
>> 
>> Today the kernel also tracks key usage for verification done with any of these
>> keys. Current verification usage includes: VERIFYING_MODULE_SIGNATURE,
>> VERIFYING_FIRMWARE_SIGNATURE, VERIFYING_KEXEC_PE_SIGNATURE,
>> VERIFYING_KEY_SIGNATURE, VERIFYING_KEY_SELF_SIGNATURE, and
>> VERIFYING_UNSPECIFIED_SIGNATURE. After these usage types were originally
>> introduced, most additions have typically used the
>> VERIFYING_UNSPECIFIED_SIGNATURE.
> 
> Since there are so many why not just format them as a list here?
> 
> Maybe start the whole cover letter with exactly two lists:
> 
> 1. All possible keyrings that are below described as "system keys",
>   and their purpose and scope (briefly).
> 2. The above verification methods and exact same level of detail
>   for each.
> 
> There's so much text here that maybe even subsections like:
> 
> Background
> ==========
> 
> <Those two lists>
> 
> Motivation
> ==========
> 
> <Motivation behind Clavis>
> 
> Solution
> ========
> 
> <Mechanics of Clavis>
> 
> Would make reviewing this heck a lot easier as you can then focus in one
> of these three parts. And I guess I have a brain of a goldfish ;-)

If you think that would make reviewing easier, I'll make these changes to the cover 
letter in the next round.  Thanks.