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Date:   Tue, 30 Mar 2021 14:47:18 -0700
From:   Eric Biggers <ebiggers@kernel.org>
To:     Jarkko Sakkinen <jarkko@kernel.org>
Cc:     David Gstir <david@sigma-star.at>,
        Sumit Garg <sumit.garg@linaro.org>,
        Ahmad Fatoum <a.fatoum@pengutronix.de>,
        Mimi Zohar <zohar@linux.ibm.com>,
        Horia =?utf-8?Q?Geant=C4=83?= <horia.geanta@nxp.com>,
        Jonathan Corbet <corbet@lwn.net>,
        David Howells <dhowells@redhat.com>,
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        Herbert Xu <herbert@gondor.apana.org.au>,
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Subject: Re: [PATCH v1 3/3] KEYS: trusted: Introduce support for NXP
 CAAM-based trusted keys
Message-ID: <YGOcZtkw3ZM5kvl6@gmail.com>
References: <319e558e1bd19b80ad6447c167a2c3942bdafea2.1615914058.git-series.a.fatoum@pengutronix.de>
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 <63dd7d4b-4729-9e03-cd8f-956b94eab0d9@pengutronix.de>
 <CAFA6WYOw_mQwOUN=onhzb7zCTyYDBrcx0E7C3LRk6nPLAVCWEQ@mail.gmail.com>
 <557b92d2-f3b8-d136-7431-419429f0e059@pengutronix.de>
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On Sun, Mar 28, 2021 at 11:37:23PM +0300, Jarkko Sakkinen wrote:
> 
> Unfortunately, TPM trusted keys started this bad security practice, and
> obviously it cannot be fixed without breaking uapi backwards compatibility.
> 

The whole point of a randomness source is that it is random.  So userspace can't
be depending on any particular output, and the randomness source can be changed
without breaking backwards compatibility.

So IMO, trusted keys should simply be fixed to use get_random_bytes().

- Eric