Received-SPF: pass (google.com: domain of linux-crypto-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Date:   Tue, 17 May 2022 19:27:08 +0200
From:   "Jason A. Donenfeld" <Jason@zx2c4.com>
To:     Ahmad Fatoum <a.fatoum@pengutronix.de>
Cc:     James Bottomley <jejb@linux.ibm.com>,
        Jarkko Sakkinen <jarkko@kernel.org>,
        Mimi Zohar <zohar@linux.ibm.com>,
        David Howells <dhowells@redhat.com>, kernel@pengutronix.de,
        Sumit Garg <sumit.garg@linaro.org>,
        Pankaj Gupta <pankaj.gupta@nxp.com>,
        David Gstir <david@sigma-star.at>,
        Michael Walle <michael@walle.cc>,
        John Ernberg <john.ernberg@actia.se>,
        James Morris <jmorris@namei.org>,
        "Serge E. Hallyn" <serge@hallyn.com>,
        Horia =?utf-8?Q?Geant=C4=83?= <horia.geanta@nxp.com>,
        Herbert Xu <herbert@gondor.apana.org.au>,
        "David S. Miller" <davem@davemloft.net>,
        Jan Luebbe <j.luebbe@pengutronix.de>,
        Eric Biggers <ebiggers@kernel.org>,
        Richard Weinberger <richard@nod.at>,
        Franck LENORMAND <franck.lenormand@nxp.com>,
        Matthias Schiffer <matthias.schiffer@ew.tq-group.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 v10 2/7] KEYS: trusted: allow use of kernel RNG for key
 material
Message-ID: <YoPa7C8xs8lgKtwv@zx2c4.com>
References: <20220513145705.2080323-1-a.fatoum@pengutronix.de>
 <20220513145705.2080323-3-a.fatoum@pengutronix.de>
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Disposition: inline
In-Reply-To: <20220513145705.2080323-3-a.fatoum@pengutronix.de>
Precedence: bulk

On Fri, May 13, 2022 at 04:57:00PM +0200, Ahmad Fatoum wrote:
> +	trusted.rng=	[KEYS]
> +			Format: <string>
> +			The RNG used to generate key material for trusted keys.
> +			Can be one of:
> +			- "kernel"
> +			- the same value as trusted.source: "tpm" or "tee"
> +			- "default"
> +			If not specified, "default" is used. In this case,
> +			the RNG's choice is left to each individual trust source.
> +

As a general mechanism, I object to this. The kernel's RNG must be
trusted in the first place for key material. That's the whole point of
it.

However, it sounds like you're not proposing a general mechanism, but
just something particular to this "trusted keys" business. In that case,
this should be a module flag, and thus not documented here, but rather
some place namespaced to your trusted keys stuff. "trusted_keys.preferred_rng={whatever}"

Jason