linux-kernel - Re: [PATCH v20 15/20] fsverity: expose verified fsverity built-in signatures to LSMs

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Message-ID: <20240805185132.GC1564@sol.localdomain>
Date: Mon, 5 Aug 2024 11:51:32 -0700
From: Eric Biggers <ebiggers@...nel.org>
To: 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, mpatocka@...hat.com, 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: [PATCH v20 15/20] fsverity: expose verified fsverity built-in
 signatures to LSMs

On Fri, Aug 02, 2024 at 11:08:29PM -0700, Fan Wu wrote:
> This patch enhances fsverity's capabilities to support both integrity and
> authenticity protection by introducing the exposure of built-in
> signatures through a new LSM hook. This functionality allows LSMs,
> e.g. IPE, to enforce policies based on the authenticity and integrity of
> files, specifically focusing on built-in fsverity signatures. It enables
> a policy enforcement layer within LSMs for fsverity, offering granular
> control over the usage of authenticity claims. For instance, a policy
> could be established to only permit the execution of all files with
> verified built-in fsverity signatures.
> 
> The introduction of a security_inode_setintegrity() hook call within
> fsverity's workflow ensures that the verified built-in signature of a file
> is exposed to LSMs. This enables LSMs to recognize and label fsverity files
> that contain a verified built-in fsverity signature. This hook is invoked
> subsequent to the fsverity_verify_signature() process, guaranteeing the
> signature's verification against fsverity's keyring. This mechanism is
> crucial for maintaining system security, as it operates in kernel space,
> effectively thwarting attempts by malicious binaries to bypass user space
> stack interactions.
> 
> The second to last commit in this patch set will add a link to the IPE
> documentation in fsverity.rst.
> 
> Signed-off-by: Deven Bowers <deven.desai@...ux.microsoft.com>
> Signed-off-by: Fan Wu <wufan@...ux.microsoft.com>

Acked-by: Eric Biggers <ebiggers@...gle.com>

- Eric