Re: [PATCH v5 3/5] KEYS: trusted: allow trust sources to use kernel RNG for key material

From: Ahmad Fatoum <a.fatoum@pengutronix.de>
To: James Bottomley <jejb@linux.ibm.com>,
	Jarkko Sakkinen <jarkko@kernel.org>,
	Mimi Zohar <zohar@linux.ibm.com>,
	David Howells <dhowells@redhat.com>
Cc: kernel@pengutronix.de, "Sumit Garg" <sumit.garg@linaro.org>,
	"David Gstir" <david@sigma-star.at>,
	"Tim Harvey" <tharvey@gateworks.com>,
	"James Morris" <jmorris@namei.org>,
	"Serge E. Hallyn" <serge@hallyn.com>,
	"Horia Geantă" <horia.geanta@nxp.com>,
	"Aymen Sghaier" <aymen.sghaier@nxp.com>,
	"Herbert Xu" <herbert@gondor.apana.org.au>,
	"David S. Miller" <davem@davemloft.net>,
	"Eric Biggers" <ebiggers@kernel.org>,
	"Jan Luebbe" <j.luebbe@pengutronix.de>,
	"Richard Weinberger" <richard@nod.at>,
	"Franck LENORMAND" <franck.lenormand@nxp.com>,
	"Matthias Schiffer" <matthias.schiffer@ew.tq-group.com>,
	"Pankaj Gupta" <pankaj.gupta@nxp.com>,
	keyrings@vger.kernel.org, linux-crypto@vger.kernel.org,
	linux-integrity@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-security-module@vger.kernel.org
Subject: Re: [PATCH v5 3/5] KEYS: trusted: allow trust sources to use kernel RNG for key material
Date: Wed, 23 Feb 2022 17:23:06 +0100	[thread overview]
Message-ID: <994a4d49-b1d3-a7ab-d7b3-33405b13c125@pengutronix.de> (raw)
In-Reply-To: <20220222195819.2313913-4-a.fatoum@pengutronix.de>

On 22.02.22 20:58, Ahmad Fatoum wrote:
> The two existing trusted key sources don't make use of the kernel RNG,
> but instead let the hardware that does the sealing/unsealing also
> generate the random key material. While a previous change offers users
> the choice to use the kernel RNG instead for both, new trust sources
> may want to unconditionally use the kernel RNG for generating key
> material, like it's done elsewhere in the kernel.
> 
> This is especially prudent for hardware that has proven-in-production
> HWRNG drivers implemented, as otherwise code would have to be duplicated
> only to arrive at a possibly worse result.
> 
> Make this possible by turning struct trusted_key_ops::get_random
> into an optional member. If a driver leaves it NULL, kernel RNG
> will be used instead.

The rebase on the change in scope of the previous commit made this
one here quite small. I would squash it into the previous commit
for v6, unless there are objections.

> 
> Acked-by: Sumit Garg <sumit.garg@linaro.org>
> Reviewed-by: David Gstir <david@sigma-star.at>
> Tested-By: Tim Harvey <tharvey@gateworks.com>
> Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
> ---
> To: James Bottomley <jejb@linux.ibm.com>
> To: Jarkko Sakkinen <jarkko@kernel.org>
> To: Mimi Zohar <zohar@linux.ibm.com>
> To: David Howells <dhowells@redhat.com>
> Cc: James Morris <jmorris@namei.org>
> Cc: "Serge E. Hallyn" <serge@hallyn.com>
> Cc: "Horia Geantă" <horia.geanta@nxp.com>
> Cc: Aymen Sghaier <aymen.sghaier@nxp.com>
> Cc: Herbert Xu <herbert@gondor.apana.org.au>
> Cc: "David S. Miller" <davem@davemloft.net>
> Cc: Eric Biggers <ebiggers@kernel.org>
> Cc: Jan Luebbe <j.luebbe@pengutronix.de>
> Cc: David Gstir <david@sigma-star.at>
> Cc: Richard Weinberger <richard@nod.at>
> Cc: Franck LENORMAND <franck.lenormand@nxp.com>
> Cc: Sumit Garg <sumit.garg@linaro.org>
> Cc: Tim Harvey <tharvey@gateworks.com>
> Cc: Matthias Schiffer <matthias.schiffer@ew.tq-group.com>
> Cc: Pankaj Gupta <pankaj.gupta@nxp.com>
> Cc: keyrings@vger.kernel.org
> Cc: linux-crypto@vger.kernel.org
> Cc: linux-integrity@vger.kernel.org
> Cc: linux-kernel@vger.kernel.org
> Cc: linux-security-module@vger.kernel.org
> ---
>  include/keys/trusted-type.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/include/keys/trusted-type.h b/include/keys/trusted-type.h
> index d89fa2579ac0..4eb64548a74f 100644
> --- a/include/keys/trusted-type.h
> +++ b/include/keys/trusted-type.h
> @@ -64,7 +64,7 @@ struct trusted_key_ops {
>  	/* Unseal a key. */
>  	int (*unseal)(struct trusted_key_payload *p, char *datablob);
>  
> -	/* Get a randomized key. */
> +	/* Optional: Get a randomized key. */
>  	int (*get_random)(unsigned char *key, size_t key_len);
>  
>  	/* Exit key interface. */

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