linux-kernel - Re: [RFC PATCH v15 18/21] ipe: enable support for fs-verity as a trust provider

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Date: Mon, 18 Mar 2024 09:08:10 +0100
From: Roberto Sassu <roberto.sassu@...weicloud.com>
To: Eric Biggers <ebiggers@...nel.org>, Fan Wu <wufan@...ux.microsoft.com>
Cc: corbet@....net, zohar@...ux.ibm.com, jmorris@...ei.org,
 serge@...lyn.com,  tytso@....edu, axboe@...nel.dk, agk@...hat.com,
 snitzer@...nel.org,  eparis@...hat.com, paul@...l-moore.com,
 linux-doc@...r.kernel.org,  linux-integrity@...r.kernel.org,
 linux-security-module@...r.kernel.org,  fsverity@...ts.linux.dev,
 linux-block@...r.kernel.org, dm-devel@...ts.linux.dev, 
 audit@...r.kernel.org, linux-kernel@...r.kernel.org, Deven Bowers
 <deven.desai@...ux.microsoft.com>
Subject: Re: [RFC PATCH v15 18/21] ipe: enable support for fs-verity as a
 trust provider

On Sun, 2024-03-17 at 22:17 -0700, Eric Biggers wrote:
> On Fri, Mar 15, 2024 at 08:35:48PM -0700, Fan Wu wrote:
> > +config IPE_PROP_FS_VERITY
> > +	bool "Enable property for fs-verity files"
> > +	depends on FS_VERITY && FS_VERITY_BUILTIN_SIGNATURES
> > +	help
> > +	  This option enables the usage of properties "fsverity_signature"
> > +	  and "fsverity_digest". These properties evaluate to TRUE when
> > +	  a file is fsverity enabled and with a signed digest
> 
> Again: why would anyone care if there is a signature, if that signature is not
> checked.
> 
> I think you meant to write something like: "when a file is fsverity enabled and
> has a valid builtin signature whose signing cert is in the .fs-verity keyring".

I was also thinking the same. I didn't follow the recent development
closely, but unless IPE locks somehow the .fs-verity keyring, the
property you suggested would not be immutable. Meaning that someone can
add/remove a key in that keyring, making the property true or false.

Roberto