Re: [PATCH v28 06/12] LRNG - add SP800-90A DRBG extension

[Randy Dunlap]

On 1/15/20 2:33 AM, Stephan MÃller wrote:

> 
> CC: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>
> CC: "Alexander E. Patrakov" <patrakov@xxxxxxxxx>
> CC: "Ahmed S. Darwish" <darwish.07@xxxxxxxxx>
> CC: "Theodore Y. Ts'o" <tytso@xxxxxxx>
> CC: Willy Tarreau <w@xxxxxx>
> CC: Matthew Garrett <mjg59@xxxxxxxxxxxxx>
> CC: Vito Caputo <vcaputo@xxxxxxxxxxx>
> CC: Andreas Dilger <adilger.kernel@xxxxxxxxx>
> CC: Jan Kara <jack@xxxxxxx>
> CC: Ray Strode <rstrode@xxxxxxxxxx>
> CC: William Jon McCann <mccann@xxxxxxx>
> CC: zhangjs <zachary@xxxxxxxxxxxxxxxx>
> CC: Andy Lutomirski <luto@xxxxxxxxxx>
> CC: Florian Weimer <fweimer@xxxxxxxxxx>
> CC: Lennart Poettering <mzxreary@xxxxxxxxxxx>
> CC: Nicolai Stange <nstange@xxxxxxx>
> Reviewed-by: Roman Drahtmueller <draht@xxxxxxxxxxxxxx>
> Tested-by: Roman DrahtmÃller <draht@xxxxxxxxxxxxxx>
> Tested-by: Marcelo Henrique Cerri <marcelo.cerri@xxxxxxxxxxxxx>
> Tested-by: Neil Horman <nhorman@xxxxxxxxxx>
> Signed-off-by: Stephan Mueller <smueller@xxxxxxxxxx>
> ---
>  drivers/char/lrng/Kconfig     |  11 ++
>  drivers/char/lrng/Makefile    |   1 +
>  drivers/char/lrng/lrng_drbg.c | 260 ++++++++++++++++++++++++++++++++++
>  3 files changed, 272 insertions(+)
>  create mode 100644 drivers/char/lrng/lrng_drbg.c
> 
> diff --git a/drivers/char/lrng/Kconfig b/drivers/char/lrng/Kconfig
> index cb701bb0b8b6..15fb623d9d1f 100644
> --- a/drivers/char/lrng/Kconfig
> +++ b/drivers/char/lrng/Kconfig
> @@ -71,4 +71,15 @@ menuconfig LRNG_DRNG_SWITCH
>  	  accessible via the external interfaces. With this configuration
>  	  option other DRNGs can be selected and loaded at runtime.
>  
> +if LRNG_DRNG_SWITCH
> +config LRNG_DRBG
> +	tristate "SP800-90A support for the LRNG"
> +	select CRYPTO_DRBG_MENU
> +	select CRYPTO_CMAC if CRYPTO_DRBG_CTR

Don't select these if CRYPTO is not already set/enabled.
It causes Kconfig warnings and possible build errors.

> +	help
> +	  Enable the SP800-90A DRBG support for the LRNG. Once the
> +	  module is loaded, output from /dev/random, /dev/urandom,
> +	  getrandom(2), or get_random_bytes is provided by a DRBG.
> +endif # LRNG_DRNG_SWITCH
> +
>  endif # LRNG

> diff --git a/drivers/char/lrng/lrng_drbg.c b/drivers/char/lrng/lrng_drbg.c
> new file mode 100644
> index 000000000000..8bf2badb1fe0
> --- /dev/null
> +++ b/drivers/char/lrng/lrng_drbg.c
> @@ -0,0 +1,260 @@
> +// SPDX-License-Identifier: GPL-2.0 OR BSD-2-Clause
> +/*
> + * Backend for the LRNG providing the cryptographic primitives using the
> + * kernel crypto API and its DRBG.
> + *
> + * Copyright (C) 2016 - 2020, Stephan Mueller <smueller@xxxxxxxxxx>
> + */
> +
> +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
> +
> +#include <crypto/drbg.h>
> +#include <linux/init.h>
> +#include <linux/module.h>
> +#include <linux/lrng.h>
> +
> +/*
> + * Define a DRBG plus a hash / MAC used to extract data from the entropy pool.
> + * For LRNG_HASH_NAME you can use a hash or a MAC (HMAC or CMAC) of your choice
> + * (Note, you should use the suggested selections below -- using SHA-1 or MD5
> + * is not wise). The idea is that the used cipher primitive can be selected to
> + * be the same as used for the DRBG. I.e. the LRNG only uses one cipher
> + * primitive using the same cipher implementation with the options offered in
> + * the following. This means, if the CTR DRBG is selected and AES-NI is present,
> + * both the CTR DRBG and the selected cmac(aes) use AES-NI.
> + *
> + * The security strengths of the DRBGs are all 256 bits according to
> + * SP800-57 section 5.6.1.
> + *
> + * This definition is allowed to be changed.
> + */
> +#ifdef CONFIG_CRYPTO_DRBG_CTR
> +static unsigned int lrng_drbg_type = 0;
> +#elif defined CONFIG_CRYPTO_DRBG_HMAC
> +static unsigned int lrng_drbg_type = 1;
> +#elif defined CONFIG_CRYPTO_DRBG_HASH
> +static unsigned int lrng_drbg_type = 2;
> +#else
> +#error "Unknown DRBG in use"
> +#endif
> +
> +/* The parameter must be r/o in sysfs as otherwise races appear. */
> +module_param(lrng_drbg_type, uint, 0444);
> +MODULE_PARM_DESC(lrng_drbg_type, "DRBG type used for LRNG (0->CTR_DRBG, "
> +				 "1->HMAC_DRBG, 2->Hash_DRBG)");

One line for the string, please, not split.

-- 
~Randy
Reported-by: Randy Dunlap <rdunlap@xxxxxxxxxxxxx>