linux-kernel - Re: [RFC PATCH v2 2/2] dm-inlinecrypt: add target for inline block device encryption

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Message-ID: <20241018173323.GA1127@sol.localdomain>
Date: Fri, 18 Oct 2024 10:33:23 -0700
From: Eric Biggers <ebiggers@...nel.org>
To: Adrian Vovk <adrianvovk@...il.com>
Cc: dm-devel@...ts.linux.dev, linux-block@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Md Sadre Alam <quic_mdalam@...cinc.com>,
	Israel Rukshin <israelr@...dia.com>,
	Milan Broz <gmazyland@...il.com>,
	Mikulas Patocka <mpatocka@...hat.com>
Subject: Re: [RFC PATCH v2 2/2] dm-inlinecrypt: add target for inline block
 device encryption

On Thu, Oct 17, 2024 at 10:52:42PM -0400, Adrian Vovk wrote:
> Hello,
> 
> On 10/16/24 19:27, Eric Biggers wrote:
> > From: Eric Biggers <ebiggers@...gle.com>
> > 
> > Add a new device-mapper target "dm-inlinecrypt" that is similar to
> > dm-crypt but uses the blk-crypto API instead of the regular crypto API.
> > This allows it to take advantage of inline encryption hardware such as
> > that commonly built into UFS host controllers.
> 
> Wow! Thank you for this patch! This is something we really want in systemd
> and in GNOME, and I came across this patchset on accident while trying to
> find a way to get someone to work on it for us.
> 
> > The table syntax matches dm-crypt's, but for now only a stripped-down
> > set of parameters is supported.  For example, for now AES-256-XTS is the
> > only supported cipher.
> > 
> > dm-inlinecrypt is based on Android's dm-default-key with the
> > controversial passthrough support removed.
> 
> That's quite unfortunate. I'd say this passthrough support is probably the
> most powerful thing about dm-default-key.
> 
> Could you elaborate on why you removed it?

Well, see the conversation you've been having with Christoph.  It seems the
passthrough / "metadata encryption" support will need to be reworked into a
filesystem native feature in order to have a chance at upstream.

Meanwhile there are people who have been waiting for basically "dm-crypt with
blk-crypto", without the passthrough support.  I hoped that I could help with
that in the meantime -- hence this patchset.

I'll go ahead and send out the full dm-default-key patches too as an RFC just so
that people can see what it involves exactly.  But be warned -- it is a bit ugly
with changes in multiple layers (not just the dm target itself).

- Eric