/**
* \file ctr_drbg.h
*
* \brief This file contains CTR_DRBG definitions and functions.
*
* CTR_DRBG is a standardized way of building a PRNG from a block-cipher
* in counter mode operation, as defined in <em>NIST SP 800-90A:
* Recommendation for Random Number Generation Using Deterministic Random
* Bit Generators</em>.
*
* The Mbed TLS implementation of CTR_DRBG uses AES-256 as the underlying
* block cipher.
*/
/*
* Copyright (C) 2006-2018, Arm Limited (or its affiliates), All Rights Reserved
* SPDX-License-Identifier: GPL-2.0
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program 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 General Public License for more details.
*
* You should have received a copy of the GNU General Public License along
* with this program; if not, write to the Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*
* This file is part of Mbed TLS (https://tls.mbed.org)
*/
#ifndef MBEDTLS_CTR_DRBG_H
#define MBEDTLS_CTR_DRBG_H
#include "aes.h"
#if defined(MBEDTLS_THREADING_C)
#include "threading.h"
#endif
#define MBEDTLS_ERR_CTR_DRBG_ENTROPY_SOURCE_FAILED -0x0034 /**< The entropy source failed. */
#define MBEDTLS_ERR_CTR_DRBG_REQUEST_TOO_BIG -0x0036 /**< The requested random buffer length is too big. */
#define MBEDTLS_ERR_CTR_DRBG_INPUT_TOO_BIG -0x0038 /**< The input (entropy + additional data) is too large. */
#define MBEDTLS_ERR_CTR_DRBG_FILE_IO_ERROR -0x003A /**< Read or write error in file. */
#define MBEDTLS_CTR_DRBG_BLOCKSIZE 16 /**< The block size used by the cipher. */
#define MBEDTLS_CTR_DRBG_KEYSIZE 32 /**< The key size used by the cipher. */
#define MBEDTLS_CTR_DRBG_KEYBITS ( MBEDTLS_CTR_DRBG_KEYSIZE * 8 ) /**< The key size for the DRBG operation, in bits. */
#define MBEDTLS_CTR_DRBG_SEEDLEN ( MBEDTLS_CTR_DRBG_KEYSIZE + MBEDTLS_CTR_DRBG_BLOCKSIZE ) /**< The seed length, calculated as (counter + AES key). */
/**
* \name SECTION: Module settings
*
* The configuration options you can set for this module are in this section.
* Either change them in config.h or define them using the compiler command
* line.
* \{
*/
#if !defined(MBEDTLS_CTR_DRBG_ENTROPY_LEN)
#if defined(MBEDTLS_SHA512_C) && !defined(MBEDTLS_ENTROPY_FORCE_SHA256)
#define MBEDTLS_CTR_DRBG_ENTROPY_LEN 48
/**< The amount of entropy used per seed by default:
* <ul><li>48 with SHA-512.</li>
* <li>32 with SHA-256.</li></ul>
*/
#else
#define MBEDTLS_CTR_DRBG_ENTROPY_LEN 32
/**< Amount of entropy used per seed by default:
* <ul><li>48 with SHA-512.</li>
* <li>32 with SHA-256.</li></ul>
*/
#endif
#endif
#if !defined(MBEDTLS_CTR_DRBG_RESEED_INTERVAL)
#define MBEDTLS_CTR_DRBG_RESEED_INTERVAL 10000
/**< The interval before reseed is performed by default. */
#endif
#if !defined(MBEDTLS_CTR_DRBG_MAX_INPUT)
#define MBEDTLS_CTR_DRBG_MAX_INPUT 256
/**< The maximum number of additional input Bytes. */
#endif
#if !defined(MBEDTLS_CTR_DRBG_MAX_REQUEST)
#define MBEDTLS_CTR_DRBG_MAX_REQUEST 1024
/**< The maximum number of requested Bytes per call. */
#endif
#if !defined(MBEDTLS_CTR_DRBG_MAX_SEED_INPUT)
#define MBEDTLS_CTR_DRBG_MAX_SEED_INPUT 384
/**< The maximum size of seed or reseed buffer. */
#endif
/* \} name SECTION: Module settings */
#define MBEDTLS_CTR_DRBG_PR_OFF 0
/**< Prediction resistance is disabled. */
#define MBEDTLS_CTR_DRBG_PR_ON 1
/**< Prediction resistance is enabled. */
#ifdef __cplusplus
extern "C" {
#endif
/**
* \brief The CTR_DRBG context structure.
*/
typedef struct mbedtls_ctr_drbg_context {
unsigned char counter[16]; /*!< The counter (V). */
int reseed_counter; /*!< The reseed counter. */
int prediction_resistance; /*!< This determines whether prediction
resistance is enabled, that is
whether to systematically reseed before
each random generation. */
size_t entropy_len; /*!< The amount of entropy grabbed on each
seed or reseed operation. */
int reseed_interval; /*!< The reseed interval. */
mbedtls_aes_context aes_ctx; /*!< The AES context. */
/*
* Callbacks (Entropy)
*/
int (*f_entropy)(void *, unsigned char *, size_t);
/*!< The entropy callback function. */
void *p_entropy; /*!< The context for the entropy function. */
#if defined(MBEDTLS_THREADING_C)
mbedtls_threading_mutex_t mutex;
#endif
}
mbedtls_ctr_drbg_context;
/**
* \brief This function initializes the CTR_DRBG context,
* and prepares it for mbedtls_ctr_drbg_seed()
* or mbedtls_ctr_drbg_free().
*
* \param ctx The CTR_DRBG context to initialize.
*/
void mbedtls_ctr_drbg_init(mbedtls_ctr_drbg_context *ctx);
/**
* \brief This function seeds and sets up the CTR_DRBG
* entropy source for future reseeds.
*
* \note Personalization data can be provided in addition to the more generic
* entropy source, to make this instantiation as unique as possible.
*
* \param ctx The CTR_DRBG context to seed.
* \param f_entropy The entropy callback, taking as arguments the
* \p p_entropy context, the buffer to fill, and the
length of the buffer.
* \param p_entropy The entropy context.
* \param custom Personalization data, that is device-specific
identifiers. Can be NULL.
* \param len The length of the personalization data.
*
* \return \c 0 on success.
* \return #MBEDTLS_ERR_CTR_DRBG_ENTROPY_SOURCE_FAILED on failure.
*/
int mbedtls_ctr_drbg_seed(mbedtls_ctr_drbg_context *ctx,
int (*f_entropy)(void *, unsigned char *, size_t),
void *p_entropy,
const unsigned char *custom,
size_t len);
/**
* \brief This function clears CTR_CRBG context data.
*
* \param ctx The CTR_DRBG context to clear.
*/
void mbedtls_ctr_drbg_free(mbedtls_ctr_drbg_context *ctx);
/**
* \brief This function turns prediction resistance on or off.
* The default value is off.
*
* \note If enabled, entropy is gathered at the beginning of
* every call to mbedtls_ctr_drbg_random_with_add().
* Only use this if your entropy source has sufficient
* throughput.
*
* \param ctx The CTR_DRBG context.
* \param resistance #MBEDTLS_CTR_DRBG_PR_ON or #MBEDTLS_CTR_DRBG_PR_OFF.
*/
void mbedtls_ctr_drbg_set_prediction_resistance(mbedtls_ctr_drbg_context *ctx,
int resistance);
/**
* \brief This function sets the amount of entropy grabbed on each
* seed or reseed. The default value is
* #MBEDTLS_CTR_DRBG_ENTROPY_LEN.
*
* \param ctx The CTR_DRBG context.
* \param len The amount of entropy to grab.
*/
void mbedtls_ctr_drbg_set_entropy_len(mbedtls_ctr_drbg_context *ctx,
size_t len);
/**
* \brief This function sets the reseed interval.
* The default value is #MBEDTLS_CTR_DRBG_RESEED_INTERVAL.
*
* \param ctx The CTR_DRBG context.
* \param interval The reseed interval.
*/
void mbedtls_ctr_drbg_set_reseed_interval(mbedtls_ctr_drbg_context *ctx,
int interval);
/**
* \brief This function reseeds the CTR_DRBG context, that is
* extracts data from the entropy source.
*
* \param ctx The CTR_DRBG context.
* \param additional Additional data to add to the state. Can be NULL.
* \param len The length of the additional data.
*
* \return \c 0 on success.
* \return #MBEDTLS_ERR_CTR_DRBG_ENTROPY_SOURCE_FAILED on failure.
*/
int mbedtls_ctr_drbg_reseed(mbedtls_ctr_drbg_context *ctx,
const unsigned char *additional, size_t len);
/**
* \brief This function updates the state of the CTR_DRBG context.
*
* \note If \p add_len is greater than
* #MBEDTLS_CTR_DRBG_MAX_SEED_INPUT, only the first
* #MBEDTLS_CTR_DRBG_MAX_SEED_INPUT Bytes are used.
* The remaining Bytes are silently discarded.
*
* \param ctx The CTR_DRBG context.
* \param additional The data to update the state with.
* \param add_len Length of \p additional data.
*
*/
void mbedtls_ctr_drbg_update(mbedtls_ctr_drbg_context *ctx,
const unsigned char *additional, size_t add_len);
/**
* \brief This function updates a CTR_DRBG instance with additional
* data and uses it to generate random data.
*
* \note The function automatically reseeds if the reseed counter is exceeded.
*
* \param p_rng The CTR_DRBG context. This must be a pointer to a
* #mbedtls_ctr_drbg_context structure.
* \param output The buffer to fill.
* \param output_len The length of the buffer.
* \param additional Additional data to update. Can be NULL.
* \param add_len The length of the additional data.
*
* \return \c 0 on success.
* \return #MBEDTLS_ERR_CTR_DRBG_ENTROPY_SOURCE_FAILED or
* #MBEDTLS_ERR_CTR_DRBG_REQUEST_TOO_BIG on failure.
*/
int mbedtls_ctr_drbg_random_with_add(void *p_rng,
unsigned char *output, size_t output_len,
const unsigned char *additional, size_t add_len);
/**
* \brief This function uses CTR_DRBG to generate random data.
*
* \note The function automatically reseeds if the reseed counter is exceeded.
*
* \param p_rng The CTR_DRBG context. This must be a pointer to a
* #mbedtls_ctr_drbg_context structure.
* \param output The buffer to fill.
* \param output_len The length of the buffer.
*
* \return \c 0 on success.
* \return #MBEDTLS_ERR_CTR_DRBG_ENTROPY_SOURCE_FAILED or
* #MBEDTLS_ERR_CTR_DRBG_REQUEST_TOO_BIG on failure.
*/
int mbedtls_ctr_drbg_random(void *p_rng,
unsigned char *output, size_t output_len);
#if defined(MBEDTLS_FS_IO)
/**
* \brief This function writes a seed file.
*
* \param ctx The CTR_DRBG context.
* \param path The name of the file.
*
* \return \c 0 on success.
* \return #MBEDTLS_ERR_CTR_DRBG_FILE_IO_ERROR on file error.
* \return #MBEDTLS_ERR_CTR_DRBG_ENTROPY_SOURCE_FAILED on
* failure.
*/
int mbedtls_ctr_drbg_write_seed_file(mbedtls_ctr_drbg_context *ctx, const char *path);
/**
* \brief This function reads and updates a seed file. The seed
* is added to this instance.
*
* \param ctx The CTR_DRBG context.
* \param path The name of the file.
*
* \return \c 0 on success.
* \return #MBEDTLS_ERR_CTR_DRBG_FILE_IO_ERROR on file error.
* \return #MBEDTLS_ERR_CTR_DRBG_ENTROPY_SOURCE_FAILED or
* #MBEDTLS_ERR_CTR_DRBG_INPUT_TOO_BIG on failure.
*/
int mbedtls_ctr_drbg_update_seed_file(mbedtls_ctr_drbg_context *ctx, const char *path);
#endif /* MBEDTLS_FS_IO */
/**
* \brief The CTR_DRBG checkup routine.
*
* \return \c 0 on success.
* \return \c 1 on failure.
*/
int mbedtls_ctr_drbg_self_test(int verbose);
/* Internal functions (do not call directly) */
int mbedtls_ctr_drbg_seed_entropy_len(mbedtls_ctr_drbg_context *,
int (*)(void *, unsigned char *, size_t), void *,
const unsigned char *, size_t, size_t);
#ifdef __cplusplus
}
#endif
#endif /* ctr_drbg.h */