linux-kernel - Re: [PATCH v27 09/12] LRNG - add Jitter RNG fast noise source

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Date:   Fri, 10 Jan 2020 08:45:22 +0100
From:   Stephan Mueller <smueller@...onox.de>
To:     Randy Dunlap <rdunlap@...radead.org>
Cc:     Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-crypto@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
        linux-api@...r.kernel.org,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        "Alexander E. Patrakov" <patrakov@...il.com>,
        "Ahmed S. Darwish" <darwish.07@...il.com>,
        "Theodore Y. Ts'o" <tytso@....edu>, Willy Tarreau <w@....eu>,
        Matthew Garrett <mjg59@...f.ucam.org>,
        Vito Caputo <vcaputo@...garu.com>,
        Andreas Dilger <adilger.kernel@...ger.ca>,
        Jan Kara <jack@...e.cz>, Ray Strode <rstrode@...hat.com>,
        William Jon McCann <mccann@....edu>,
        zhangjs <zachary@...shancloud.com>,
        Andy Lutomirski <luto@...nel.org>,
        Florian Weimer <fweimer@...hat.com>,
        Lennart Poettering <mzxreary@...inter.de>,
        Nicolai Stange <nstange@...e.de>,
        "Peter, Matthias" <matthias.peter@....bund.de>,
        Marcelo Henrique Cerri <marcelo.cerri@...onical.com>,
        Roman Drahtmueller <draht@...altsekun.de>,
        Neil Horman <nhorman@...hat.com>,
        Julia Lawall <julia.lawall@...ia.fr>
Subject: Re: [PATCH v27 09/12] LRNG - add Jitter RNG fast noise source

Am Freitag, 10. Januar 2020, 01:24:47 CET schrieb Randy Dunlap:

Hi Randy,

> Hi,
> 
> On 1/9/20 12:34 AM, Stephan Müller wrote:
> > ---
> > 
> >  drivers/char/lrng/Kconfig     | 11 +++++
> >  drivers/char/lrng/Makefile    |  1 +
> >  drivers/char/lrng/lrng_jent.c | 87 +++++++++++++++++++++++++++++++++++
> >  3 files changed, 99 insertions(+)
> >  create mode 100644 drivers/char/lrng/lrng_jent.c
> > 
> > diff --git a/drivers/char/lrng/lrng_jent.c b/drivers/char/lrng/lrng_jent.c
> > new file mode 100644
> > index 000000000000..97c0d192e9c8
> > --- /dev/null
> > +++ b/drivers/char/lrng/lrng_jent.c
> > @@ -0,0 +1,87 @@
> > +// SPDX-License-Identifier: GPL-2.0 OR BSD-2-Clause
> > +/*
> > + * LRNG Fast Noise Source: Jitter RNG
> > + *
> > + * Copyright (C) 2016 - 2020, Stephan Mueller <smueller@...onox.de>
> > + */
> > +
> > +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
> > +
> > +#include <linux/types.h>
> > +#include <crypto/internal/jitterentropy.h>
> > +
> > +#include "lrng_internal.h"
> > +
> > +/*
> > + * Estimated entropy of data is a 16th of
> > LRNG_DRNG_SECURITY_STRENGTH_BITS. + * Albeit a full entropy assessment is
> > provided for the noise source indicating + * that it provides high
> > entropy rates and considering that it deactivates + * when it detects
> > insufficient hardware, the chosen under estimation of + * entropy is
> > considered to be acceptable to all reviewers.
> > + */
> > +static u32 jitterrng = LRNG_DRNG_SECURITY_STRENGTH_BITS>>4;
> > +module_param(jitterrng, uint, 0644);
> > +MODULE_PARM_DESC(jitterrng, "Entropy in bits of 256 data bits from Jitter
> > " +			    "RNG noise source");
> > +
> > +/**
> > + * Get Jitter RNG entropy
> > + *
> > + * @outbuf buffer to store entropy
> > + * @outbuflen length of buffer
> > + * @return > 0 on success where value provides the added entropy in bits
> > + *	   0 if no fast source was available
> > + */
> 
> Don't begin the comment block with /**
> or convert it to Linux kernel-doc notation format.

Yes, the colons are missing and there is no @return. It will be fixed with the 
next patch set.

Thank you.
> 
> > +static struct rand_data *lrng_jent_state;
> > +
> > +u32 lrng_get_jent(u8 *outbuf, unsigned int outbuflen)
> > +{
> > +	int ret;
> > +	u32 ent_bits = jitterrng;
> > +	unsigned long flags;
> > +	static DEFINE_SPINLOCK(lrng_jent_lock);
> > +	static int lrng_jent_initialized = 0;
> > +
> > +	spin_lock_irqsave(&lrng_jent_lock, flags);
> > +
> > +	if (!ent_bits || (lrng_jent_initialized == -1)) {
> > +		spin_unlock_irqrestore(&lrng_jent_lock, flags);
> > +		return 0;
> > +	}
> > +
> > +	if (!lrng_jent_initialized) {
> > +		lrng_jent_state = jent_lrng_entropy_collector();
> > +		if (!lrng_jent_state) {
> > +			jitterrng = 0;
> > +			lrng_jent_initialized = -1;
> > +			spin_unlock_irqrestore(&lrng_jent_lock, flags);
> > +			pr_info("Jitter RNG unusable on current system\n");
> > +			return 0;
> > +		}
> > +		lrng_jent_initialized = 1;
> > +		pr_debug("Jitter RNG working on current system\n");
> > +	}
> > +	ret = jent_read_entropy(lrng_jent_state, outbuf, outbuflen);
> > +	spin_unlock_irqrestore(&lrng_jent_lock, flags);
> > +
> > +	if (ret) {
> > +		pr_debug("Jitter RNG failed with %d\n", ret);
> > +		return 0;
> > +	}
> > +
> > +	/* Obtain entropy statement */
> > +	if (outbuflen != LRNG_DRNG_SECURITY_STRENGTH_BYTES)
> > +		ent_bits = (ent_bits * outbuflen<<3) /
> > +			   LRNG_DRNG_SECURITY_STRENGTH_BITS;
> > +	/* Cap entropy to buffer size in bits */
> > +	ent_bits = min_t(u32, ent_bits, outbuflen<<3);
> > +	pr_debug("obtained %u bits of entropy from Jitter RNG noise source\n",
> > +		 ent_bits);
> > +
> > +	return ent_bits;
> > +}
> > +
> > +u32 lrng_jent_entropylevel(void)
> > +{
> > +	return min_t(u32, jitterrng, LRNG_DRNG_SECURITY_STRENGTH_BITS);
> > +}
> 
> thanks.



Ciao
Stephan