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Subject: Re: [PATCH v25 10/12] LRNG - add TRNG support
To:     =?UTF-8?Q?Stephan_M=c3=bcller?= <smueller@chronox.de>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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        Linux Crypto Mailing List <linux-crypto@vger.kernel.org>,
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        Linux API <linux-api@vger.kernel.org>,
        "Eric W. Biederman" <ebiederm@xmission.com>,
        "Ahmed S. Darwish" <darwish.07@gmail.com>,
        "Theodore Y. Ts'o" <tytso@mit.edu>, Willy Tarreau <w@1wt.eu>,
        Matthew Garrett <mjg59@srcf.ucam.org>,
        Vito Caputo <vcaputo@pengaru.com>,
        Andreas Dilger <adilger.kernel@dilger.ca>,
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        William Jon McCann <mccann@jhu.edu>,
        zhangjs <zachary@baishancloud.com>,
        Florian Weimer <fweimer@redhat.com>,
        Lennart Poettering <mzxreary@0pointer.de>,
        Nicolai Stange <nstange@suse.de>,
        "Peter, Matthias" <matthias.peter@bsi.bund.de>,
        Marcelo Henrique Cerri <marcelo.cerri@canonical.com>,
        Roman Drahtmueller <draht@schaltsekun.de>,
        Neil Horman <nhorman@redhat.com>
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From:   "Alexander E. Patrakov" <patrakov@gmail.com>
Message-ID: <cdf1791d-0e60-cb9f-6030-0258f12bef3c@gmail.com>
Date:   Wed, 20 Nov 2019 14:55:46 +0500
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20.11.2019 13:58, Stephan Müller пишет:

> Or another idea and apologies if I restart this conversation as there was
> already a discussion around it: what about extending the getrandom(2) call
> instead of adding a device file?
> 
> What about adding yet another flag to getrandom: GRND_TRUERANDOM and process
> it as follows:
> 
>          if (flags & ~(GRND_NONBLOCK|GRND_RANDOM|GRND_INSECURE|
> GRND_TRUERANDOM))
>                  return -EINVAL;
> 
>          //From Andy's tree
>          /*
>           * Requesting insecure and blocking randomness at the same time makes
>           * no sense.
>           */
>          if ((flags & (GRND_INSECURE|GRND_RANDOM)) == (GRND_INSECURE|
> GRND_RANDOM))
>                  return -EINVAL;
> 
> 	  /* We only allow GRND_TRUERANDOM by itself or with NONBLOCK */
> 	  if (! ((flags & GRND_TRUERANDOM) &&
>                 ((flags == GRND_TRUERANDOM) ||
>                  (flags == GRND_TRUERANDOM | GRND_NONBLOCK))))
> 		return -EINVAL;
> 
> 	if (flags & GRND_TRUERANDOM) {
> 		... do the TRNG processing ...
> 		... may return -ENOPNOTSUPP if no TRNG available ...
> 	}

This would totally miss the point of adding a device node: UNIX 
permissions that don't allow "others" to read and deplete "true" random 
numbers.

-- 
Alexander E. Patrakov