Date:   Thu, 16 Jan 2020 08:22:05 +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>,
        Dan Carpenter <dan.carpenter@...cle.com>
Subject: Re: [PATCH v28 01/12] Linux Random Number Generator

Am Donnerstag, 16. Januar 2020, 01:11:40 CET schrieb Randy Dunlap:

Hi Randy,

> Hi,
> 
> On 1/15/20 2:31 AM, Stephan Müller wrote:
> > CC: "Eric W. Biederman" <ebiederm@...ssion.com>
> > CC: "Alexander E. Patrakov" <patrakov@...il.com>
> > CC: "Ahmed S. Darwish" <darwish.07@...il.com>
> > CC: "Theodore Y. Ts'o" <tytso@....edu>
> > CC: Willy Tarreau <w@....eu>
> > CC: Matthew Garrett <mjg59@...f.ucam.org>
> > CC: Vito Caputo <vcaputo@...garu.com>
> > CC: Andreas Dilger <adilger.kernel@...ger.ca>
> > CC: Jan Kara <jack@...e.cz>
> > CC: Ray Strode <rstrode@...hat.com>
> > CC: William Jon McCann <mccann@....edu>
> > CC: zhangjs <zachary@...shancloud.com>
> > CC: Andy Lutomirski <luto@...nel.org>
> > CC: Florian Weimer <fweimer@...hat.com>
> > CC: Lennart Poettering <mzxreary@...inter.de>
> > CC: Nicolai Stange <nstange@...e.de>
> > Mathematical aspects Reviewed-by: "Peter, Matthias"
> > <matthias.peter@....bund.de> Reviewed-by: Marcelo Henrique Cerri
> > <marcelo.cerri@...onical.com>
> > Reviewed-by: Roman Drahtmueller <draht@...altsekun.de>
> > Tested-by: Roman Drahtmüller <draht@...altsekun.de>
> > Tested-by: Marcelo Henrique Cerri <marcelo.cerri@...onical.com>
> > Tested-by: Neil Horman <nhorman@...hat.com>
> > Signed-off-by: Stephan Mueller <smueller@...onox.de>
> > ---
> > 
> >  MAINTAINERS                         |   7 +
> >  drivers/char/Kconfig                |   2 +
> >  drivers/char/Makefile               |   9 +-
> >  drivers/char/lrng/Kconfig           |  67 +++
> >  drivers/char/lrng/Makefile          |   9 +
> >  drivers/char/lrng/lrng_archrandom.c |  94 ++++
> >  drivers/char/lrng/lrng_aux.c        | 148 +++++++
> >  drivers/char/lrng/lrng_chacha20.c   | 265 ++++++++++++
> >  drivers/char/lrng/lrng_chacha20.h   |  25 ++
> >  drivers/char/lrng/lrng_drng.c       | 400 +++++++++++++++++
> >  drivers/char/lrng/lrng_interfaces.c | 638 ++++++++++++++++++++++++++++
> >  drivers/char/lrng/lrng_internal.h   | 296 +++++++++++++
> >  drivers/char/lrng/lrng_lfsr.h       | 152 +++++++
> >  drivers/char/lrng/lrng_pool.c       | 588 +++++++++++++++++++++++++
> >  drivers/char/lrng/lrng_sw_noise.c   | 102 +++++
> >  drivers/char/lrng/lrng_sw_noise.h   |  57 +++
> >  include/linux/lrng.h                |  63 +++
> >  17 files changed, 2921 insertions(+), 1 deletion(-)
> >  create mode 100644 drivers/char/lrng/Kconfig
> >  create mode 100644 drivers/char/lrng/Makefile
> >  create mode 100644 drivers/char/lrng/lrng_archrandom.c
> >  create mode 100644 drivers/char/lrng/lrng_aux.c
> >  create mode 100644 drivers/char/lrng/lrng_chacha20.c
> >  create mode 100644 drivers/char/lrng/lrng_chacha20.h
> >  create mode 100644 drivers/char/lrng/lrng_drng.c
> >  create mode 100644 drivers/char/lrng/lrng_interfaces.c
> >  create mode 100644 drivers/char/lrng/lrng_internal.h
> >  create mode 100644 drivers/char/lrng/lrng_lfsr.h
> >  create mode 100644 drivers/char/lrng/lrng_pool.c
> >  create mode 100644 drivers/char/lrng/lrng_sw_noise.c
> >  create mode 100644 drivers/char/lrng/lrng_sw_noise.h
> >  create mode 100644 include/linux/lrng.h
> > 
> > diff --git a/drivers/char/lrng/Kconfig b/drivers/char/lrng/Kconfig
> > new file mode 100644
> > index 000000000000..56f13efd3592
> > --- /dev/null
> > +++ b/drivers/char/lrng/Kconfig
> > @@ -0,0 +1,67 @@
> > +# SPDX-License-Identifier: GPL-2.0
> > +#
> > +# Linux Random Number Generator configuration
> > +#
> > +
> > +menuconfig LRNG
> > +	bool "Linux Random Number Generator"
> 
> This should probably depend on CRYPTO and/or some other CRYPTO_xxx symbols.
> Or (worst case) select them.  :(

It does not - all CRYPTO related code is limited into the lrng_drbg.c, 
lrng_kcapi.c and lrng_jent.c which are all guarded by a Kconfig option.
> 
> This message (when CONFIG_CRYPTO is disabled and no crypto facilities are
> enabled) should be avoidable when the correct Kconfig entries are used:
> 
> ../drivers/char/lrng/lrng_drbg.c:38:2: error: #error "Unknown DRBG in use"
>  #error "Unknown DRBG in use"

Right - this should now be fixed with a depends on CRYPTO for the 
aforementioned 3 C files which have an equal entry in Kconfig.
> 
> > +	help
> > +	  The Linux Random Number Generator (LRNG) is the replacement
> > +	  of the existing /dev/random provided with drivers/char/random.c.
> > +	  It generates entropy from different noise sources and
> > +	  delivers significant entropy during boot.
> > +
> > +if LRNG
> > +
> > +choice
> > +	prompt "LRNG Entropy Pool Size"
> > +	default LRNG_POOL_SIZE_4096
> > +	help
> > +	  Select the size of the LRNG entropy pool. The size of the
> > +	  entropy pool is relevant for the amount of entropy that
> > +	  the LRNG can maintain as a maximum. The larger the size
> > +	  of the entropy pool is the more entropy can be maintained
> > +	  but the less often older entropic values are overwritten
> > +	  with new entropy.
> > +
> > +	config LRNG_POOL_SIZE_512
> > +		bool "512 bits"
> > +
> > +	config LRNG_POOL_SIZE_1024
> > +		bool "1024 bits"
> > +
> > +	config LRNG_POOL_SIZE_2048
> > +		bool "2048 bits"
> > +
> > +	config LRNG_POOL_SIZE_4096
> > +		bool "4096 bits (default)"
> > +
> > +	config LRNG_POOL_SIZE_8192
> > +		bool "8192 bits"
> > +
> > +	config LRNG_POOL_SIZE_16384
> > +		bool "16384 bits"
> > +
> > +	config LRNG_POOL_SIZE_32768
> > +		bool "32768 bits"
> > +
> > +	config LRNG_POOL_SIZE_65536
> > +		bool "65536 bits"
> > +
> > +	config LRNG_POOL_SIZE_131072
> > +		bool "131072 bits"
> > +endchoice
> > +
> > +config LRNG_POOL_SIZE
> > +	int
> > +	default 0 if LRNG_POOL_SIZE_512
> > +	default 1 if LRNG_POOL_SIZE_1024
> > +	default 2 if LRNG_POOL_SIZE_2048
> > +	default 3 if LRNG_POOL_SIZE_4096
> > +	default 4 if LRNG_POOL_SIZE_8192
> > +	default 5 if LRNG_POOL_SIZE_16384
> > +	default 6 if LRNG_POOL_SIZE_32768
> > +	default 7 if LRNG_POOL_SIZE_65536
> > +	default 8 if LRNG_POOL_SIZE_131072
> > +
> > +endif # LRNG
> > 
> > diff --git a/drivers/char/lrng/lrng_archrandom.c
> > b/drivers/char/lrng/lrng_archrandom.c new file mode 100644
> > index 000000000000..eeba708d025f
> > --- /dev/null
> > +++ b/drivers/char/lrng/lrng_archrandom.c
> > @@ -0,0 +1,94 @@
> > +// SPDX-License-Identifier: GPL-2.0 OR BSD-2-Clause
> > +/*
> > + * LRNG Fast Noise Source: CPU-based noise source
> > + *
> > + * Copyright (C) 2016 - 2020, Stephan Mueller <smueller@...onox.de>
> > + */
> > +
> > +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
> > +
> > +#include <linux/random.h>
> > +
> > +#include "lrng_internal.h"
> > +
> > +/*
> > + * Estimated entropy of data is a 32th of
> > LRNG_DRNG_SECURITY_STRENGTH_BITS. + * As we have no ability to review the
> > implementation of those noise sources, + * it is prudent to have a
> > conservative estimate here.
> > + */
> > +#define LRNG_ARCHRANDOM_DEFAULT_STRENGTH
> > (LRNG_DRNG_SECURITY_STRENGTH_BITS>>5) +#define
> > LRNG_ARCHRANDOM_TRUST_CPU_STRENGTH LRNG_DRNG_SECURITY_STRENGTH_BITS
> > +#ifdef CONFIG_RANDOM_TRUST_CPU
> > +static u32 archrandom = LRNG_ARCHRANDOM_TRUST_CPU_STRENGTH;
> > +#else
> > +static u32 archrandom = LRNG_ARCHRANDOM_DEFAULT_STRENGTH;
> > +#endif
> > +module_param(archrandom, uint, 0644);
> > +MODULE_PARM_DESC(archrandom, "Entropy in bits of 256 data bits from CPU
> > noise " +			     "source (e.g. RDRAND)");
> 
> Please put the string on one line like several other MODULE_PARM_DESC() are
> done:
> 
> +MODULE_PARM_DESC(archrandom,
> +		"Entropy in bits of 256 data bits from CPU noise source (e.g. 
RDRAND)");

Done.
> 
> 
> With CONFIG_CRYPTO disabled, these warnings happen:
> 
> WARNING: unmet direct dependencies detected for CRYPTO_DRBG_MENU
>   Depends on [n]: CRYPTO [=n]
>   Selected by [m]:
>   - LRNG_DRBG [=m] && LRNG [=y] && LRNG_DRNG_SWITCH [=y]
> 
> WARNING: unmet direct dependencies detected for CRYPTO_RNG
>   Depends on [n]: CRYPTO [=n]
>   Selected by [m]:
>   - LRNG_KCAPI [=m] && LRNG [=y] && LRNG_DRNG_SWITCH [=y]
> 
> ../drivers/char/lrng/lrng_drbg.c: In function ‘lrng_hash_name’:
> ../drivers/char/lrng/lrng_drbg.c:225:1: warning: control reaches end of
> non-void function [-Wreturn-type] }
>  ^
> ../drivers/char/lrng/lrng_drbg.c: In function ‘lrng_drbg_name’:
> ../drivers/char/lrng/lrng_drbg.c:220:1: warning: control reaches end of
> non-void function [-Wreturn-type] }
>  ^
> 
> and build errors happen also, which can be prevented with Kconfig fixes.

With the changes to the Kconfig file as explained in the other emails, I can 
successfully compile the LRNG without the crypto API being enabled.

Thank you for pointing that one out.

Ciao
Stephan

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