[PATCH] nvme-auth: fail when the controller does not authenticate itself

[Keith Busch]

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.