drbg.c

/*
 * DRBG: Deterministic Random Bits Generator
 *       Based on NIST Recommended DRBG from NIST SP800-90A with the following
 *       properties:
 *		* CTR DRBG with DF with AES-128, AES-192, AES-256 cores
 *		* Hash DRBG with DF with SHA-1, SHA-256, SHA-384, SHA-512 cores
 *		* HMAC DRBG with DF with SHA-1, SHA-256, SHA-384, SHA-512 cores
 *		* with and without prediction resistance
 *
 * Copyright Stephan Mueller <smueller@chronox.de>, 2014
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, and the entire permission notice in its entirety,
 *    including the disclaimer of warranties.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. The name of the author may not be used to endorse or promote
 *    products derived from this software without specific prior
 *    written permission.
 *
 * ALTERNATIVELY, this product may be distributed under the terms of
 * the GNU General Public License, in which case the provisions of the GPL are
 * required INSTEAD OF the above restrictions.  (This clause is
 * necessary due to a potential bad interaction between the GPL and
 * the restrictions contained in a BSD-style copyright.)
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE, ALL OF
 * WHICH ARE HEREBY DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
 * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
 * BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE
 * USE OF THIS SOFTWARE, EVEN IF NOT ADVISED OF THE POSSIBILITY OF SUCH
 * DAMAGE.
 *
 * DRBG Usage
 * ==========
 * The SP 800-90A DRBG allows the user to specify a personalization string
 * for initialization as well as an additional information string for each
 * random number request. The following code fragments show how a caller
 * uses the kernel crypto API to use the full functionality of the DRBG.
 *
 * Usage without any additional data
 * ---------------------------------
 * struct crypto_rng *drng;
 * int err;
 * char data[DATALEN];
 *
 * drng = crypto_alloc_rng(drng_name, 0, 0);
 * err = crypto_rng_get_bytes(drng, &data, DATALEN);
 * crypto_free_rng(drng);
 *
 *
 * Usage with personalization string during initialization
 * -------------------------------------------------------
 * struct crypto_rng *drng;
 * int err;
 * char data[DATALEN];
 * struct drbg_string pers;
 * char personalization[11] = "some-string";
 *
 * drbg_string_fill(&pers, personalization, strlen(personalization));
 * drng = crypto_alloc_rng(drng_name, 0, 0);
 * // The reset completely re-initializes the DRBG with the provided
 * // personalization string
 * err = crypto_rng_reset(drng, &personalization, strlen(personalization));
 * err = crypto_rng_get_bytes(drng, &data, DATALEN);
 * crypto_free_rng(drng);
 *
 *
 * Usage with additional information string during random number request
 * ---------------------------------------------------------------------
 * struct crypto_rng *drng;
 * int err;
 * char data[DATALEN];
 * char addtl_string[11] = "some-string";
 * string drbg_string addtl;
 *
 * drbg_string_fill(&addtl, addtl_string, strlen(addtl_string));
 * drng = crypto_alloc_rng(drng_name, 0, 0);
 * // The following call is a wrapper to crypto_rng_get_bytes() and returns
 * // the same error codes.
 * err = crypto_drbg_get_bytes_addtl(drng, &data, DATALEN, &addtl);
 * crypto_free_rng(drng);
 *
 *
 * Usage with personalization and additional information strings
 * -------------------------------------------------------------
 * Just mix both scenarios above.
 */

#include <crypto/drbg.h>

/***************************************************************
 * Backend cipher definitions available to DRBG
 ***************************************************************/

/*
 * The order of the DRBG definitions here matter: every DRBG is registered
 * as stdrng. Each DRBG receives an increasing cra_priority values the later
 * they are defined in this array (see drbg_fill_array).
 *
 * HMAC DRBGs are favored over Hash DRBGs over CTR DRBGs, and
 * the SHA256 / AES 256 over other ciphers. Thus, the favored
 * DRBGs are the latest entries in this array.
 */
static const struct drbg_core drbg_cores[] = {
#ifdef CONFIG_CRYPTO_DRBG_CTR
	{
		.flags = DRBG_CTR | DRBG_STRENGTH128,
		.statelen = 32, /* 256 bits as defined in 10.2.1 */
		.blocklen_bytes = 16,
		.cra_name = "ctr_aes128",
		.backend_cra_name = "ecb(aes)",
	}, {
		.flags = DRBG_CTR | DRBG_STRENGTH192,
		.statelen = 40, /* 320 bits as defined in 10.2.1 */
		.blocklen_bytes = 16,
		.cra_name = "ctr_aes192",
		.backend_cra_name = "ecb(aes)",
	}, {
		.flags = DRBG_CTR | DRBG_STRENGTH256,
		.statelen = 48, /* 384 bits as defined in 10.2.1 */
		.blocklen_bytes = 16,
		.cra_name = "ctr_aes256",
		.backend_cra_name = "ecb(aes)",
	},
#endif /* CONFIG_CRYPTO_DRBG_CTR */
#ifdef CONFIG_CRYPTO_DRBG_HASH
	{
		.flags = DRBG_HASH | DRBG_STRENGTH128,
		.statelen = 55, /* 440 bits */
		.blocklen_bytes = 20,
		.cra_name = "sha1",
		.backend_cra_name = "sha1",
	}, {
		.flags = DRBG_HASH | DRBG_STRENGTH256,
		.statelen = 111, /* 888 bits */
		.blocklen_bytes = 48,
		.cra_name = "sha384",
		.backend_cra_name = "sha384",
	}, {
		.flags = DRBG_HASH | DRBG_STRENGTH256,
		.statelen = 111, /* 888 bits */
		.blocklen_bytes = 64,
		.cra_name = "sha512",
		.backend_cra_name = "sha512",
	}, {
		.flags = DRBG_HASH | DRBG_STRENGTH256,
		.statelen = 55, /* 440 bits */
		.blocklen_bytes = 32,
		.cra_name = "sha256",
		.backend_cra_name = "sha256",
	},
#endif /* CONFIG_CRYPTO_DRBG_HASH */
#ifdef CONFIG_CRYPTO_DRBG_HMAC
	{
		.flags = DRBG_HMAC | DRBG_STRENGTH128,
		.statelen = 20, /* block length of cipher */
		.blocklen_bytes = 20,
		.cra_name = "hmac_sha1",
		.backend_cra_name = "hmac(sha1)",
	}, {
		.flags = DRBG_HMAC | DRBG_STRENGTH256,
		.statelen = 48, /* block length of cipher */
		.blocklen_bytes = 48,
		.cra_name = "hmac_sha384",
		.backend_cra_name = "hmac(sha384)",
	}, {
		.flags = DRBG_HMAC | DRBG_STRENGTH256,
		.statelen = 64, /* block length of cipher */
		.blocklen_bytes = 64,
		.cra_name = "hmac_sha512",
		.backend_cra_name = "hmac(sha512)",
	}, {
		.flags = DRBG_HMAC | DRBG_STRENGTH256,
		.statelen = 32, /* block length of cipher */
		.blocklen_bytes = 32,
		.cra_name = "hmac_sha256",
		.backend_cra_name = "hmac(sha256)",
	},
#endif /* CONFIG_CRYPTO_DRBG_HMAC */
};

/******************************************************************
 * Generic helper functions
 ******************************************************************/

/*
 * Return strength of DRBG according to SP800-90A section 8.4
 *
 * @flags DRBG flags reference