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/*
* Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
*
* Licensed under the Apache License, Version 2.0 (the "License").
* You may not use this file except in compliance with the License.
* A copy of the License is located at
*
* http://aws.amazon.com/apache2.0
*
* or in the "license" file accompanying this file. This file is distributed
* on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either
* express or implied. See the License for the specific language governing
* permissions and limitations under the License.
*/
#pragma once
#include <openssl/evp.h>
#include "crypto/s2n_hash.h"
#include "utils/s2n_blob.h"
#include "utils/s2n_result.h"
#define S2N_DRBG_BLOCK_SIZE 16
#define S2N_DRBG_MAX_KEY_SIZE 32
#define S2N_DRBG_MAX_SEED_SIZE (S2N_DRBG_BLOCK_SIZE + S2N_DRBG_MAX_KEY_SIZE)
/* The maximum size of any one request: from NIST SP800-90A 10.2.1 Table 3 */
#define S2N_DRBG_GENERATE_LIMIT 8192
/* We reseed after 2^35 bytes have been generated: from NIST SP800-90A 10.2.1 Table 3 */
#define S2N_DRBG_RESEED_LIMIT 34359738368
struct s2n_drbg {
/* Track how many bytes have been used */
uint64_t bytes_used;
EVP_CIPHER_CTX *ctx;
/* The current DRBG 'value' */
uint8_t v[S2N_DRBG_BLOCK_SIZE];
/* Used only by the unit tests: how many times has entropy been mixed in */
uint64_t mixes;
};
/*
* S2N_AES_128_CTR_NO_DF_PR is a deterministic random bit generator using AES 128 in counter mode (AES_128_CTR). It does not
* use a derivation function (NO_DF) on the seed but does have prediction resistance (PR).
*
* S2N_AES_256_CTR_NO_DF_PR is a deterministic random bit generator using AES 256 in counter mode (AES_128_CTR). It does not
* use a derivation function on the seed but does have prediction resistance.
*/
typedef enum {S2N_AES_128_CTR_NO_DF_PR, S2N_AES_256_CTR_NO_DF_PR} s2n_drbg_mode;
/* Per NIST SP 800-90C 6.3
*
* s2n's DRBG does provide prediction resistance
* and does not support the additional_input parameter (which per 800-90C may be zero).
*
* The security strength provided by s2n's DRBG is either 128 or 256 bits depending on the s2n_drbg_mode passed in.
*/
extern int s2n_drbg_instantiate(struct s2n_drbg *drbg, struct s2n_blob *personalization_string, const s2n_drbg_mode mode);
extern int s2n_drbg_generate(struct s2n_drbg *drbg, struct s2n_blob *returned_bits);
extern int s2n_drbg_wipe(struct s2n_drbg *drbg);
extern int s2n_drbg_bytes_used(struct s2n_drbg *drbg, uint64_t *bytes_used);
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