/* drbg-aes.h

 *

 * The CTR-AES-256-based random-number generator from SP800-90A.

 */

/* Copyright (C) 2013 Red Hat

 *  

 * The nettle library is free software; you can redistribute it and/or modify

 * it under the terms of the GNU Lesser General Public License as published by

 * the Free Software Foundation; either version 2.1 of the License, or (at your

 * option) any later version.

 * 

 * The nettle library is distributed in the hope that it will be useful, but

 * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY

 * or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public

 * License for more details.

 * 

 * You should have received a copy of the GNU Lesser General Public License

 * along with the nettle library; see the file COPYING.LIB.  If not, write to

 * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,

 * MA 02111-1301, USA.

 */

#ifndef GNUTLS_LIB_NETTLE_INT_DRBG_AES_H

#define GNUTLS_LIB_NETTLE_INT_DRBG_AES_H

#include <config.h>

#include <nettle/aes.h>

/* This is nettle's increment macro */

/* Requires that size > 0 */

#define INCREMENT(size, ctr)                    \

  do {                                          \

    unsigned increment_i = (size) - 1;          \

    if (++(ctr)[increment_i] == 0)              \

      while (increment_i > 0                    \

             && ++(ctr)[--increment_i] == 0 )   \

        ;                                       \

  } while (0)

#define DRBG_AES_KEY_SIZE AES256_KEY_SIZE

#define DRBG_AES_SEED_SIZE (AES_BLOCK_SIZE+DRBG_AES_KEY_SIZE)

/* This is the CTR-AES-256-based random-number generator from SP800-90A.

 */

struct drbg_aes_ctx {

	unsigned seeded;

	/* The current key */

	struct aes256_ctx key;

	uint8_t v[AES_BLOCK_SIZE];

	unsigned reseed_counter;

};

/* max_number_of_bits_per_request */

#define MAX_DRBG_AES_GENERATE_SIZE 65536 /* 2^19 */

/* This DRBG should be reseeded if reseed_counter exceeds

 * that number. Otherwise drbg_aes_random() will fail.

 */

#define DRBG_AES_RESEED_TIME 16777216

/* The entropy provided in these functions should be of

 * size DRBG_AES_SEED_SIZE. Additional data and pers.

 * string may be <= DRBG_AES_SEED_SIZE.

 */

int

drbg_aes_init(struct drbg_aes_ctx *ctx, 

	unsigned entropy_size, const uint8_t *entropy, 

	unsigned pstring_size, const uint8_t* pstring);

int

drbg_aes_reseed(struct drbg_aes_ctx *ctx, 

	unsigned entropy_size, const uint8_t *entropy, 

	unsigned add_size, const uint8_t* add);

/* our wrapper for the low-level drbg_aes_generate */

int

drbg_aes_random(struct drbg_aes_ctx *ctx, unsigned length,

		uint8_t * dst);

int

drbg_aes_generate(struct drbg_aes_ctx *ctx, unsigned length,

		uint8_t * dst, unsigned add_size, const uint8_t* add);

/* For deinitialization use zeroize_key() on the context */

int drbg_aes_is_seeded(struct drbg_aes_ctx *ctx);

int drbg_aes_self_test(void);

#endif /* GNUTLS_LIB_NETTLE_INT_DRBG_AES_H */