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Date: Tue, 13 Oct 2026 09:40:10 -0600
From: Keith Busch <kbusch@kernel.org>
To: Yehyeong Lee <yhlee@isslab.korea.ac.kr>
Cc: Hannes Reinecke <hare@suse.de>, Jens Axboe <axboe@kernel.dk>,
	Christoph Hellwig <hch@lst.de>, Sagi Grimberg <sagi@grimberg.me>,
	linux-nvme@lists.infradead.org, linux-kernel@vger.kernel.org,
	stable@vger.kernel.org
Subject: Re: [PATCH] nvme-auth: fail when the controller does not
 authenticate itself
Message-ID: <as5Q2k-aQokHA-ar@kbusch-mbp>
References: <20261006134807.518056-1-yhlee@isslab.korea.ac.kr>
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In-Reply-To: <20261006134807.518056-1-yhlee@isslab.korea.ac.kr>

On Tue, Oct 06, 2026 at 10:48:05PM +0900, Yehyeong Lee wrote:
> nvme_auth_process_dhchap_success1() returns success as soon as the
> controller clears the rvalid flag in its DH-HMAC-CHAP success1 message,
> without looking at whether the host had asked the controller to
> authenticate.  A host configured with a controller secret sends a
> challenge in its reply, computes the expected controller response, and
> sets chap->bi_directional; if the controller then answers with
> rvalid = 0 the response is never compared, the host still sends
> success2, and the queue is marked as authenticated.
> 
> A malicious or man-in-the-middle controller therefore only has to clear
> one flag to turn the configured bidirectional authentication into a
> one-way one, without holding any secret of its own.  The target side
> already treats the mirror image of this as fatal: when the host supplied
> a challenge but no controller key is configured, nvmet_auth_success1()
> fails the authentication rather than answering with rvalid = 0.
> 
> Refuse the connection if the controller returns no response although
> bidirectional authentication was requested.  chap->bi_directional is the
> right condition rather than ctrl->ctrl_key, because secure concatenation
> sends a challenge only to derive the PSK and deliberately clears
> bi_directional; a one-way setup without a controller secret keeps
> returning success as before.

Thanks, applied to nvme-7.4.