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

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Date:   Sat, 30 Jan 2021 19:53:39 +0200
From:   Jarkko Sakkinen <jarkko@...nel.org>
To:     Ahmad Fatoum <a.fatoum@...gutronix.de>,
        James Bottomley <jejb@...ux.ibm.com>,
        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: Re: Migration to trusted keys: sealing user-provided key?

On Thu, 2021-01-28 at 18:31 +0100, Ahmad Fatoum wrote:
> 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?

Maybe it's the lack of knowledge with dm-crypt, but why this would be
useful? Just want to understand the bottleneck, that's all.

> Cheers,
> Ahmad

/Jarkko