linux-kernel - Re: [PATCH v4] KEYS: encrypted: Instantiate key with user-provided decrypted data

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Date:   Thu, 6 Jan 2022 13:30:29 -0500
From:   Yael Tiomkin <yaelt@...gle.com>
To:     Jarkko Sakkinen <jarkko@...nel.org>
Cc:     linux-integrity@...r.kernel.org, jejb@...ux.ibm.com,
        Mimi Zohar <zohar@...ux.ibm.com>, corbet@....net,
        dhowells@...hat.com, jmorris@...ei.org, serge@...lyn.com,
        keyrings@...r.kernel.org, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        linux-security-module <linux-security-module@...r.kernel.org>
Subject: Re: [PATCH v4] KEYS: encrypted: Instantiate key with user-provided
 decrypted data

On Wed, Jan 5, 2022 at 3:12 PM Jarkko Sakkinen <jarkko@...nel.org> wrote:
>
> On Wed, 2021-12-29 at 16:53 -0500, Yael Tiomkin wrote:
> > The encrypted.c class supports instantiation of encrypted keys with
> > either an already-encrypted key material, or by generating new key
> > material based on random numbers. This patch defines a new datablob
> > format: [<format>] <master-key name> <decrypted data length>
> > <decrypted data> that allows to instantiate encrypted keys using
> > user-provided decrypted data, and therefore allows to perform key
> > encryption from userspace. The decrypted key material will be
> > inaccessible from userspace.
>
> The 2nd to last sentence is essentially a tautology but fails to
> be even that, as you can already "perform key encryption" from user
> space, just not with arbitrary key material.
>
> It does not elighten any applications of this feature.
>
> /Jarkko

Sure. Please look at the modification below.

The encrypted.c class supports instantiation of encrypted keys with
either an already-encrypted key material, or by generating new key
material based on random numbers. This patch defines a new datablob
format: [<format>] <master-key name> <decrypted data length>
<decrypted data> that allows to inject (and encrypt) user-provided
decrypted data. The decrypted key material will be inaccessible from
userspace. This feature also acts as a building block for a userspace
envelope encryption capability.

Yael