linux-kernel - Re: [PATCH v6 0/5] Allow guest access to EFI confidential computing secret area

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Message-ID: <YdNHgtuVoLofL4cW@zn.tnic>
Date:   Mon, 3 Jan 2022 19:59:14 +0100
From:   Borislav Petkov <bp@...e.de>
To:     Dov Murik <dovmurik@...ux.ibm.com>
Cc:     linux-efi@...r.kernel.org, Ashish Kalra <ashish.kalra@....com>,
        Brijesh Singh <brijesh.singh@....com>,
        Tom Lendacky <thomas.lendacky@....com>,
        Ard Biesheuvel <ardb@...nel.org>,
        James Morris <jmorris@...ei.org>,
        "Serge E. Hallyn" <serge@...lyn.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Greg KH <gregkh@...uxfoundation.org>,
        Andrew Scull <ascull@...gle.com>,
        Dave Hansen <dave.hansen@...el.com>,
        "Dr. David Alan Gilbert" <dgilbert@...hat.com>,
        James Bottomley <jejb@...ux.ibm.com>,
        Tobin Feldman-Fitzthum <tobin@...ux.ibm.com>,
        Jim Cadden <jcadden@....com>,
        Daniele Buono <dbuono@...ux.vnet.ibm.com>,
        linux-coco@...ts.linux.dev, linux-security-module@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6 0/5] Allow guest access to EFI confidential computing
 secret area

On Mon, Nov 29, 2021 at 11:42:46AM +0000, Dov Murik wrote:
> As a usage example, consider a guest performing computations on
> encrypted files.  The Guest Owner provides the decryption key (= secret)
> using the secret injection mechanism.  The guest application reads the
> secret from the efi_secret filesystem and proceeds to decrypt the files
> into memory and then performs the needed computations on the content.
> 
> In this example, the host can't read the files from the disk image
> because they are encrypted.  Host can't read the decryption key because
> it is passed using the secret injection mechanism (= secure channel).
> Host can't read the decrypted content from memory because it's a
> confidential (memory-encrypted) guest.

So maybe I don't understand the example properly or something's missing
but why can't the guest owner simply scp the secrets into the guest? Why
is this special thing needed?

The secret below says "...kata-secrets" so this sounds like
something-automated-containers-thing where they'd profit from getting
secrets automatically supplied to the guest. But I guess there you can
scp too...

So what am I missing?

Thx.

-- 
Regards/Gruss,
    Boris.

SUSE Software Solutions Germany GmbH, GF: Ivo Totev, HRB 36809, AG Nürnberg