/* 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.  If not, see <https://www.gnu.org/licenses/>.
 */

#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 */
