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From: Sumit Garg <sumit.garg@linaro.org>
To: Jarkko Sakkinen <jarkko@kernel.org>
Cc: "Ahmad Fatoum" <a.fatoum@pengutronix.de>,
	"James Bottomley" <jejb@linux.ibm.com>,
	"Mimi Zohar" <zohar@linux.ibm.com>,
	"David Howells" <dhowells@redhat.com>,
	kernel <kernel@pengutronix.de>,
	"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>,
	"Udit Agarwal" <udit.agarwal@nxp.com>,
	"Eric Biggers" <ebiggers@kernel.org>,
	"Jan Luebbe" <j.luebbe@pengutronix.de>,
	"David Gstir" <david@sigma-star.at>,
	"Richard Weinberger" <richard@nod.at>,
	"Franck LENORMAND" <franck.lenormand@nxp.com>,
	"open list:ASYMMETRIC KEYS" <keyrings@vger.kernel.org>,
	"open list:HARDWARE RANDOM NUMBER GENERATOR CORE"
	<linux-crypto@vger.kernel.org>,
	linux-integrity <linux-integrity@vger.kernel.org>,
	"Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>,
	"open list:SECURITY SUBSYSTEM"
	<linux-security-module@vger.kernel.org>
Subject: Re: [PATCH 2/4] KEYS: trusted: allow trust sources to use kernel RNG for key material
Date: Tue, 10 Aug 2021 10:54:46 +0530	[thread overview]
Message-ID: <CAFA6WYPg20EiYATXStt1mgGJVjkOK5BK7WDbTdzOujBdcH6KLg@mail.gmail.com> (raw)
In-Reply-To: <20210809095647.7xcxjeot5gyvmlpj@kernel.org>

On Mon, 9 Aug 2021 at 15:26, Jarkko Sakkinen <jarkko@kernel.org> wrote:
>
> On Mon, Aug 09, 2021 at 09:52:20AM +0200, Ahmad Fatoum wrote:
> > Hello Sumit,
> >
> > On 22.07.21 08:31, Sumit Garg wrote:
> > > On Wed, 21 Jul 2021 at 22:19, Ahmad Fatoum <a.fatoum@pengutronix.de> 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.
> > >>
> > >> 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: Udit Agarwal <udit.agarwal@nxp.com>
> > >> 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: 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 +-
> > >>  security/keys/trusted-keys/trusted_core.c | 2 +-
> > >>  2 files changed, 2 insertions(+), 2 deletions(-)
> > >>
> > >> 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. */
> > >> diff --git a/security/keys/trusted-keys/trusted_core.c b/security/keys/trusted-keys/trusted_core.c
> > >> index 569af9af8df0..d2b7626cde8b 100644
> > >> --- a/security/keys/trusted-keys/trusted_core.c
> > >> +++ b/security/keys/trusted-keys/trusted_core.c
> > >> @@ -334,7 +334,7 @@ static int __init init_trusted(void)
> > >>                         continue;
> > >>
> > >>                 get_random = trusted_key_sources[i].ops->get_random;
> > >> -               if (trusted_kernel_rng)
> > >> +               if (trusted_kernel_rng || !get_random)
> > >>                         get_random = kernel_get_random;
> > >>
> > >
> > > For ease of understanding, I would prefer to write it as:
> > >
> > >                   get_random = trusted_key_sources[i].ops->get_random ?:
> > >                                          kernel_get_random;
> > >                   if (trusted_kernel_rng)
> > >                         get_random = kernel_get_random;
> > >
> > > With that:
> > >
> > > Acked-by: Sumit Garg <sumit.garg@linaro.org>
> >
> > I don't think it improves readability to split up the conditional.
> > At least I need to take a second pass over the code to understand
> > the second conditional.
>
> Ternary operators are pain to read, unless a super trivial case.
>
> I'd stick to what you did.

Fair enough, I am fine with the current patch.

-Sumit

>
> /Jarkko

  reply	other threads:[~2021-08-10  5:25 UTC|newest]

Thread overview: 28+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-21 16:48 [PATCH 0/4] KEYS: trusted: Introduce support for NXP CAAM-based trusted keys Ahmad Fatoum
2021-07-21 16:48 ` [PATCH 1/4] KEYS: trusted: allow users to use kernel RNG for key material Ahmad Fatoum
2021-07-22  6:17   ` Sumit Garg
2021-07-21 16:48 ` [PATCH 2/4] KEYS: trusted: allow trust sources " Ahmad Fatoum
2021-07-22  6:31   ` Sumit Garg
2021-08-09  7:52     ` Ahmad Fatoum
2021-08-09  9:56       ` Jarkko Sakkinen
2021-08-10  5:24         ` Sumit Garg [this message]
2021-07-21 16:48 ` [PATCH 3/4] crypto: caam - add in-kernel interface for blob generator Ahmad Fatoum
2021-08-10 11:29   ` David Gstir
2021-08-11 10:22     ` Ahmad Fatoum
2021-08-11 10:43       ` David Gstir
2021-07-21 16:48 ` [PATCH 4/4] KEYS: trusted: Introduce support for NXP CAAM-based trusted keys Ahmad Fatoum
2021-08-06 15:12 ` [PATCH 0/4] " Ahmad Fatoum
2021-08-09  9:35   ` Jarkko Sakkinen
2021-08-09 10:16     ` Ahmad Fatoum
2021-08-10 11:28       ` David Gstir
2021-08-20 16:25         ` Ahmad Fatoum
2021-08-20 15:39 ` Tim Harvey
2021-08-20 16:19   ` Ahmad Fatoum
2021-08-20 20:20     ` Tim Harvey
2021-08-20 20:36       ` Ahmad Fatoum
2021-08-20 21:19         ` Tim Harvey
2021-08-23 13:29           ` Ahmad Fatoum
2021-08-23 17:50             ` Tim Harvey
2021-08-24  7:33               ` Ahmad Fatoum
2021-08-24 15:23                 ` Tim Harvey
2021-08-25  9:34                   ` Ahmad Fatoum

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