linux-kernel - Migration to trusted keys: sealing user-provided key?

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Message-ID: <74830d4f-5a76-8ba8-aad0-0d79f7c01af9@pengutronix.de>
Date:   Thu, 28 Jan 2021 18:31:57 +0100
From:   Ahmad Fatoum <a.fatoum@...gutronix.de>
To:     James Bottomley <jejb@...ux.ibm.com>,
        Jarkko Sakkinen <jarkko@...nel.org>,
        Mimi Zohar <zohar@...ux.ibm.com>,
        David Howells <dhowells@...hat.com>, keyrings@...r.kernel.org
Cc:     linux-integrity@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-security-module@...r.kernel.org, kernel@...gutronix.de,
        jlu@...gutronix.de
Subject: Migration to trusted keys: sealing user-provided key?

Hello,

I've been looking into how a migration to using trusted/encrypted keys
would look like (particularly with dm-crypt).

Currently, it seems the the only way is to re-encrypt the partitions
because trusted/encrypted keys always generate their payloads from
RNG.

If instead there was a key command to initialize a new trusted/encrypted
key with a user provided value, users could use whatever mechanism they
used beforehand to get a plaintext key and use that to initialize a new
trusted/encrypted key. From there on, the key will be like any other
trusted/encrypted key and not be disclosed again to userspace.

What are your thoughts on this? Would an API like

  keyctl add trusted dmcrypt-key 'set <content>' # user-supplied content

be acceptable?

Cheers,
Ahmad

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