/**
* \file hmac_drbg.h
*
* \brief The HMAC_DRBG pseudorandom generator.
*
* This module implements the HMAC_DRBG pseudorandom generator described
* in <em>NIST SP 800-90A: Recommendation for Random Number Generation Using
* Deterministic Random Bit Generators</em>.
*/
/*
* Copyright (C) 2006-2019, ARM Limited, 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_HMAC_DRBG_H
#define MBEDTLS_HMAC_DRBG_H
#if !defined(MBEDTLS_CONFIG_FILE)
#include "config.h"
#else
#include MBEDTLS_CONFIG_FILE
#endif
#include "md.h"
#if defined(MBEDTLS_THREADING_C)
#include "threading.h"
#endif
/*
* Error codes
*/
#define MBEDTLS_ERR_HMAC_DRBG_REQUEST_TOO_BIG -0x0003 /**< Too many random requested in single call. */
#define MBEDTLS_ERR_HMAC_DRBG_INPUT_TOO_BIG -0x0005 /**< Input too large (Entropy + additional). */
#define MBEDTLS_ERR_HMAC_DRBG_FILE_IO_ERROR -0x0007 /**< Read/write error in file. */
#define MBEDTLS_ERR_HMAC_DRBG_ENTROPY_SOURCE_FAILED -0x0009 /**< The entropy source failed. */
/**
* \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 on the compiler command line.
* \{
*/
#if !defined(MBEDTLS_HMAC_DRBG_RESEED_INTERVAL)
#define MBEDTLS_HMAC_DRBG_RESEED_INTERVAL 10000 /**< Interval before reseed is performed by default */
#endif
#if !defined(MBEDTLS_HMAC_DRBG_MAX_INPUT)
#define MBEDTLS_HMAC_DRBG_MAX_INPUT 256 /**< Maximum number of additional input bytes */
#endif
#if !defined(MBEDTLS_HMAC_DRBG_MAX_REQUEST)
#define MBEDTLS_HMAC_DRBG_MAX_REQUEST 1024 /**< Maximum number of requested bytes per call */
#endif
#if !defined(MBEDTLS_HMAC_DRBG_MAX_SEED_INPUT)
#define MBEDTLS_HMAC_DRBG_MAX_SEED_INPUT 384 /**< Maximum size of (re)seed buffer */
#endif
/* \} name SECTION: Module settings */
#define MBEDTLS_HMAC_DRBG_PR_OFF 0 /**< No prediction resistance */
#define MBEDTLS_HMAC_DRBG_PR_ON 1 /**< Prediction resistance enabled */
#ifdef __cplusplus
extern "C" {
#endif
/**
* HMAC_DRBG context.
*/
typedef struct mbedtls_hmac_drbg_context
{
/* Working state: the key K is not stored explicitly,
* but is implied by the HMAC context */
mbedtls_md_context_t md_ctx; /*!< HMAC context (inc. K) */
unsigned char V[MBEDTLS_MD_MAX_SIZE]; /*!< V in the spec */
int reseed_counter; /*!< reseed counter */
/* Administrative state */
size_t entropy_len; /*!< entropy bytes grabbed on each (re)seed */
int prediction_resistance; /*!< enable prediction resistance (Automatic
reseed before every random generation) */
int reseed_interval; /*!< reseed interval */
/* Callbacks */
int (*f_entropy)(void *, unsigned char *, size_t); /*!< entropy function */
void *p_entropy; /*!< context for the entropy function */
#if defined(MBEDTLS_THREADING_C)
mbedtls_threading_mutex_t mutex;
#endif
} mbedtls_hmac_drbg_context;
/**
* \brief HMAC_DRBG context initialization.
*
* This function makes the context ready for mbedtls_hmac_drbg_seed(),
* mbedtls_hmac_drbg_seed_buf() or mbedtls_hmac_drbg_free().
*
* \param ctx HMAC_DRBG context to be initialized.
*/
void mbedtls_hmac_drbg_init( mbedtls_hmac_drbg_context *ctx );
/**
* \brief HMAC_DRBG initial seeding.
*
* Set the initial seed and set up the entropy source for future reseeds.
*
* A typical choice for the \p f_entropy and \p p_entropy parameters is
* to use the entropy module:
* - \p f_entropy is mbedtls_entropy_func();
* - \p p_entropy is an instance of ::mbedtls_entropy_context initialized
* with mbedtls_entropy_init() (which registers the platform's default
* entropy sources).
*
* You can provide a personalization string in addition to the
* entropy source, to make this instantiation as unique as possible.
*
* \note By default, the security strength as defined by NIST is:
* - 128 bits if \p md_info is SHA-1;
* - 192 bits if \p md_info is SHA-224;
* - 256 bits if \p md_info is SHA-256, SHA-384 or SHA-512.
* Note that SHA-256 is just as efficient as SHA-224.
* The security strength can be reduced if a smaller
* entropy length is set with
* mbedtls_hmac_drbg_set_entropy_len().
*
* \note The default entropy length is the security strength
* (converted from bits to bytes). You can override
* it by calling mbedtls_hmac_drbg_set_entropy_len().
*
* \note During the initial seeding, this function calls
* the entropy source to obtain a nonce
* whose length is half the entropy length.
*
* \param ctx HMAC_DRBG context to be seeded.
* \param md_info MD algorithm to use for HMAC_DRBG.
* \param f_entropy The entropy callback, taking as arguments the
* \p p_entropy context, the buffer to fill, and the
* length of the buffer.
* \p f_entropy is always called with a length that is
* less than or equal to the entropy length.
* \param p_entropy The entropy context to pass to \p f_entropy.
* \param custom The personalization string.
* This can be \c NULL, in which case the personalization
* string is empty regardless of the value of \p len.
* \param len The length of the personalization string.
* This must be at most #MBEDTLS_HMAC_DRBG_MAX_INPUT
* and also at most
* #MBEDTLS_HMAC_DRBG_MAX_SEED_INPUT - \p entropy_len * 3 / 2
* where \p entropy_len is the entropy length
* described above.
*
* \return \c 0 if successful.
* \return #MBEDTLS_ERR_MD_BAD_INPUT_DATA if \p md_info is
* invalid.
* \return #MBEDTLS_ERR_MD_ALLOC_FAILED if there was not enough
* memory to allocate context data.
* \return #MBEDTLS_ERR_HMAC_DRBG_ENTROPY_SOURCE_FAILED
* if the call to \p f_entropy failed.
*/
int mbedtls_hmac_drbg_seed( mbedtls_hmac_drbg_context *ctx,
const mbedtls_md_info_t * md_info,
int (*f_entropy)(void *, unsigned char *, size_t),
void *p_entropy,
const unsigned char *custom,
size_t len );
/**
* \brief Initilisation of simpified HMAC_DRBG (never reseeds).
*
* This function is meant for use in algorithms that need a pseudorandom
* input such as deterministic ECDSA.
*
* \param ctx HMAC_DRBG context to be initialised.
* \param md_info MD algorithm to use for HMAC_DRBG.
* \param data Concatenation of the initial entropy string and
* the additional data.
* \param data_len Length of \p data in bytes.
*
* \return \c 0 if successful. or
* \return #MBEDTLS_ERR_MD_BAD_INPUT_DATA if \p md_info is
* invalid.
* \return #MBEDTLS_ERR_MD_ALLOC_FAILED if there was not enough
* memory to allocate context data.
*/
int mbedtls_hmac_drbg_seed_buf( mbedtls_hmac_drbg_context *ctx,
const mbedtls_md_info_t * md_info,
const unsigned char *data, size_t data_len );
/**
* \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_hmac_drbg_random_with_add()
* or mbedtls_hmac_drbg_random().
* Only use this if your entropy source has sufficient
* throughput.
*
* \param ctx The HMAC_DRBG context.
* \param resistance #MBEDTLS_HMAC_DRBG_PR_ON or #MBEDTLS_HMAC_DRBG_PR_OFF.
*/
void mbedtls_hmac_drbg_set_prediction_resistance( mbedtls_hmac_drbg_context *ctx,
int resistance );
/**
* \brief This function sets the amount of entropy grabbed on each
* seed or reseed.
*
* See the documentation of mbedtls_hmac_drbg_seed() for the default value.
*
* \param ctx The HMAC_DRBG context.
* \param len The amount of entropy to grab, in bytes.
*/
void mbedtls_hmac_drbg_set_entropy_len( mbedtls_hmac_drbg_context *ctx,
size_t len );
/**
* \brief Set the reseed interval.
*
* The reseed interval is the number of calls to mbedtls_hmac_drbg_random()
* or mbedtls_hmac_drbg_random_with_add() after which the entropy function
* is called again.
*
* The default value is #MBEDTLS_HMAC_DRBG_RESEED_INTERVAL.
*
* \param ctx The HMAC_DRBG context.
* \param interval The reseed interval.
*/
void mbedtls_hmac_drbg_set_reseed_interval( mbedtls_hmac_drbg_context *ctx,
int interval );
/**
* \brief This function updates the state of the HMAC_DRBG context.
*
* \param ctx The HMAC_DRBG context.
* \param additional The data to update the state with.
* If this is \c NULL, there is no additional data.
* \param add_len Length of \p additional in bytes.
* Unused if \p additional is \c NULL.
*
* \return \c 0 on success, or an error from the underlying
* hash calculation.
*/
int mbedtls_hmac_drbg_update_ret( mbedtls_hmac_drbg_context *ctx,
const unsigned char *additional, size_t add_len );
/**
* \brief This function reseeds the HMAC_DRBG context, that is
* extracts data from the entropy source.
*
* \param ctx The HMAC_DRBG context.
* \param additional Additional data to add to the state.
* If this is \c NULL, there is no additional data
* and \p len should be \c 0.
* \param len The length of the additional data.
* This must be at most #MBEDTLS_HMAC_DRBG_MAX_INPUT
* and also at most
* #MBEDTLS_HMAC_DRBG_MAX_SEED_INPUT - \p entropy_len
* where \p entropy_len is the entropy length
* (see mbedtls_hmac_drbg_set_entropy_len()).
*
* \return \c 0 if successful.
* \return #MBEDTLS_ERR_HMAC_DRBG_ENTROPY_SOURCE_FAILED
* if a call to the entropy function failed.
*/
int mbedtls_hmac_drbg_reseed( mbedtls_hmac_drbg_context *ctx,
const unsigned char *additional, size_t len );
/**
* \brief This function updates an HMAC_DRBG instance with additional
* data and uses it to generate random data.
*
* This function automatically reseeds if the reseed counter is exceeded
* or prediction resistance is enabled.
*
* \param p_rng The HMAC_DRBG context. This must be a pointer to a
* #mbedtls_hmac_drbg_context structure.
* \param output The buffer to fill.
* \param output_len The length of the buffer in bytes.
* This must be at most #MBEDTLS_HMAC_DRBG_MAX_REQUEST.
* \param additional Additional data to update with.
* If this is \c NULL, there is no additional data
* and \p add_len should be \c 0.
* \param add_len The length of the additional data.
* This must be at most #MBEDTLS_HMAC_DRBG_MAX_INPUT.
*
* \return \c 0 if successful.
* \return #MBEDTLS_ERR_HMAC_DRBG_ENTROPY_SOURCE_FAILED
* if a call to the entropy source failed.
* \return #MBEDTLS_ERR_HMAC_DRBG_REQUEST_TOO_BIG if
* \p output_len > #MBEDTLS_HMAC_DRBG_MAX_REQUEST.
* \return #MBEDTLS_ERR_HMAC_DRBG_INPUT_TOO_BIG if
* \p add_len > #MBEDTLS_HMAC_DRBG_MAX_INPUT.
*/
int mbedtls_hmac_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 HMAC_DRBG to generate random data.
*
* This function automatically reseeds if the reseed counter is exceeded
* or prediction resistance is enabled.
*
* \param p_rng The HMAC_DRBG context. This must be a pointer to a
* #mbedtls_hmac_drbg_context structure.
* \param output The buffer to fill.
* \param out_len The length of the buffer in bytes.
* This must be at most #MBEDTLS_HMAC_DRBG_MAX_REQUEST.
*
* \return \c 0 if successful.
* \return #MBEDTLS_ERR_HMAC_DRBG_ENTROPY_SOURCE_FAILED
* if a call to the entropy source failed.
* \return #MBEDTLS_ERR_HMAC_DRBG_REQUEST_TOO_BIG if
* \p out_len > #MBEDTLS_HMAC_DRBG_MAX_REQUEST.
*/
int mbedtls_hmac_drbg_random( void *p_rng, unsigned char *output, size_t out_len );
/**
* \brief Free an HMAC_DRBG context
*
* \param ctx The HMAC_DRBG context to free.
*/
void mbedtls_hmac_drbg_free( mbedtls_hmac_drbg_context *ctx );
#if ! defined(MBEDTLS_DEPRECATED_REMOVED)
#if defined(MBEDTLS_DEPRECATED_WARNING)
#define MBEDTLS_DEPRECATED __attribute__((deprecated))
#else
#define MBEDTLS_DEPRECATED
#endif
/**
* \brief This function updates the state of the HMAC_DRBG context.
*
* \deprecated Superseded by mbedtls_hmac_drbg_update_ret()
* in 2.16.0.
*
* \param ctx The HMAC_DRBG context.
* \param additional The data to update the state with.
* If this is \c NULL, there is no additional data.
* \param add_len Length of \p additional in bytes.
* Unused if \p additional is \c NULL.
*/
MBEDTLS_DEPRECATED void mbedtls_hmac_drbg_update(
mbedtls_hmac_drbg_context *ctx,
const unsigned char *additional, size_t add_len );
#undef MBEDTLS_DEPRECATED
#endif /* !MBEDTLS_DEPRECATED_REMOVED */
#if defined(MBEDTLS_FS_IO)
/**
* \brief This function writes a seed file.
*
* \param ctx The HMAC_DRBG context.
* \param path The name of the file.
*
* \return \c 0 on success.
* \return #MBEDTLS_ERR_HMAC_DRBG_FILE_IO_ERROR on file error.
* \return #MBEDTLS_ERR_HMAC_DRBG_ENTROPY_SOURCE_FAILED on reseed
* failure.
*/
int mbedtls_hmac_drbg_write_seed_file( mbedtls_hmac_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 HMAC_DRBG context.
* \param path The name of the file.
*
* \return \c 0 on success.
* \return #MBEDTLS_ERR_HMAC_DRBG_FILE_IO_ERROR on file error.
* \return #MBEDTLS_ERR_HMAC_DRBG_ENTROPY_SOURCE_FAILED on
* reseed failure.
* \return #MBEDTLS_ERR_HMAC_DRBG_INPUT_TOO_BIG if the existing
* seed file is too large.
*/
int mbedtls_hmac_drbg_update_seed_file( mbedtls_hmac_drbg_context *ctx, const char *path );
#endif /* MBEDTLS_FS_IO */
#if defined(MBEDTLS_SELF_TEST)
/**
* \brief The HMAC_DRBG Checkup routine.
*
* \return \c 0 if successful.
* \return \c 1 if the test failed.
*/
int mbedtls_hmac_drbg_self_test( int verbose );
#endif
#ifdef __cplusplus
}
#endif
#endif /* hmac_drbg.h */