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Message-ID: <21250bc0-623b-f11d-7dbf-458d144b7963@pengutronix.de>
Date:   Tue, 17 May 2022 19:52:51 +0200
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From:   Ahmad Fatoum <a.fatoum@pengutronix.de>
Subject: Re: [PATCH v10 2/7] KEYS: trusted: allow use of kernel RNG for key
 material
To:     "Jason A. Donenfeld" <Jason@zx2c4.com>
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>,
        =?UTF-8?Q?Horia_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
References: <20220513145705.2080323-1-a.fatoum@pengutronix.de>
 <20220513145705.2080323-3-a.fatoum@pengutronix.de>
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Hello Jason,

On 17.05.22 19:27, Jason A. Donenfeld wrote:
> 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.

The two currently upstream trust sources (trusted key backends) each provide
their own RNG callback. This series adds a third backend that uses kernel RNG
and additionally provides users of the two existing trust sources the option
to benefit from kernel RNG as well.

> 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}"

The trusted keys module is trusted.ko and directly before my added lines is
the trusted.source=  documentation, so I think this is already at the correct place.

Thanks,
Ahmad

> 
> Jason
> 


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