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mbedtls/include/polarssl/ctr_drbg.h
Paul Bakker 2ceda57989 Ability to force the Entropy module to use SHA-256 as its basis 
By default the SHA-512 module is used if both are available. On some
systems, SHA-256 is the better choice.

Contributed by: Gergely Budai
2014-02-06 15:55:25 +01:00

240 lines
8.9 KiB
C
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/**
* \file ctr_drbg.h
*
* \brief CTR_DRBG based on AES-256 (NIST SP 800-90)
*
* Copyright (C) 2006-2013, Brainspark B.V.
*
* This file is part of PolarSSL (http://www.polarssl.org)
* Lead Maintainer: Paul Bakker <polarssl_maintainer at polarssl.org>
*
* All rights reserved.
*
* 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.
*/
#ifndef POLARSSL_CTR_DRBG_H
#define POLARSSL_CTR_DRBG_H
#include <string.h>
#include "aes.h"
#define POLARSSL_ERR_CTR_DRBG_ENTROPY_SOURCE_FAILED -0x0034 /**< The entropy source failed. */
#define POLARSSL_ERR_CTR_DRBG_REQUEST_TOO_BIG -0x0036 /**< Too many random requested in single call. */
#define POLARSSL_ERR_CTR_DRBG_INPUT_TOO_BIG -0x0038 /**< Input too large (Entropy + additional). */
#define POLARSSL_ERR_CTR_DRBG_FILE_IO_ERROR -0x003A /**< Read/write error in file. */
#define CTR_DRBG_BLOCKSIZE 16 /**< Block size used by the cipher */
#define CTR_DRBG_KEYSIZE 32 /**< Key size used by the cipher */
#define CTR_DRBG_KEYBITS ( CTR_DRBG_KEYSIZE * 8 )
#define CTR_DRBG_SEEDLEN ( CTR_DRBG_KEYSIZE + CTR_DRBG_BLOCKSIZE )
/**< The seed length (counter + AES key) */
#if !defined(POLARSSL_CONFIG_OPTIONS)
#if defined(POLARSSL_SHA512_C) && !defined(POLARSSL_ENTROPY_FORCE_SHA256)
#define CTR_DRBG_ENTROPY_LEN 48 /**< Amount of entropy used per seed by default (48 with SHA-512, 32 with SHA-256) */
#else
#define CTR_DRBG_ENTROPY_LEN 32 /**< Amount of entropy used per seed by default (48 with SHA-512, 32 with SHA-256) */
#endif
#define CTR_DRBG_RESEED_INTERVAL 10000 /**< Interval before reseed is performed by default */
#define CTR_DRBG_MAX_INPUT 256 /**< Maximum number of additional input bytes */
#define CTR_DRBG_MAX_REQUEST 1024 /**< Maximum number of requested bytes per call */
#define CTR_DRBG_MAX_SEED_INPUT 384 /**< Maximum size of (re)seed buffer */
#endif /* !POLARSSL_CONFIG_OPTIONS */
#define CTR_DRBG_PR_OFF 0 /**< No prediction resistance */
#define CTR_DRBG_PR_ON 1 /**< Prediction resistance enabled */
#ifdef __cplusplus
extern "C" {
#endif
/**
* \brief CTR_DRBG context structure
*/
typedef struct
{
unsigned char counter[16]; /*!< counter (V) */
int reseed_counter; /*!< reseed counter */
int prediction_resistance; /*!< enable prediction resistance (Automatic
reseed before every random generation) */
size_t entropy_len; /*!< amount of entropy grabbed on each (re)seed */
int reseed_interval; /*!< reseed interval */
aes_context aes_ctx; /*!< AES context */
/*
* Callbacks (Entropy)
*/
int (*f_entropy)(void *, unsigned char *, size_t);
void *p_entropy; /*!< context for the entropy function */
}
ctr_drbg_context;
/**
* \brief CTR_DRBG initialization
*
* Note: Personalization data can be provided in addition to the more generic
* entropy source to make this instantiation as unique as possible.
*
* \param ctx CTR_DRBG context to be initialized
* \param f_entropy Entropy callback (p_entropy, buffer to fill, buffer
* length)
* \param p_entropy Entropy context
* \param custom Personalization data (Device specific identifiers)
* (Can be NULL)
* \param len Length of personalization data
*
* \return 0 if successful, or
* POLARSSL_ERR_CTR_DRBG_ENTROPY_SOURCE_FAILED
*/
int ctr_drbg_init( ctr_drbg_context *ctx,
int (*f_entropy)(void *, unsigned char *, size_t),
void *p_entropy,
const unsigned char *custom,
size_t len );
/**
* \brief Enable / disable prediction resistance (Default: Off)
*
* Note: If enabled, entropy is used for ctx->entropy_len before each call!
* Only use this if you have ample supply of good entropy!
*
* \param ctx CTR_DRBG context
* \param resistance CTR_DRBG_PR_ON or CTR_DRBG_PR_OFF
*/
void ctr_drbg_set_prediction_resistance( ctr_drbg_context *ctx,
int resistance );
/**
* \brief Set the amount of entropy grabbed on each (re)seed
* (Default: CTR_DRBG_ENTROPY_LEN)
*
* \param ctx CTR_DRBG context
* \param len Amount of entropy to grab
*/
void ctr_drbg_set_entropy_len( ctr_drbg_context *ctx,
size_t len );
/**
* \brief Set the reseed interval
* (Default: CTR_DRBG_RESEED_INTERVAL)
*
* \param ctx CTR_DRBG context
* \param interval Reseed interval
*/
void ctr_drbg_set_reseed_interval( ctr_drbg_context *ctx,
int interval );
/**
* \brief CTR_DRBG reseeding (extracts data from entropy source)
*
* \param ctx CTR_DRBG context
* \param additional Additional data to add to state (Can be NULL)
* \param len Length of additional data
*
* \return 0 if successful, or
* POLARSSL_ERR_CTR_DRBG_ENTROPY_SOURCE_FAILED
*/
int ctr_drbg_reseed( ctr_drbg_context *ctx,
const unsigned char *additional, size_t len );
/**
* \brief CTR_DRBG update state
*
* \param ctx CTR_DRBG context
* \param additional Additional data to update state with
* \param add_len Length of additional data
*/
void ctr_drbg_update( ctr_drbg_context *ctx,
const unsigned char *additional, size_t add_len );
/**
* \brief CTR_DRBG generate random with additional update input
*
* Note: Automatically reseeds if reseed_counter is reached.
*
* \param p_rng CTR_DRBG context
* \param output Buffer to fill
* \param output_len Length of the buffer
* \param additional Additional data to update with (Can be NULL)
* \param add_len Length of additional data
*
* \return 0 if successful, or
* POLARSSL_ERR_CTR_DRBG_ENTROPY_SOURCE_FAILED, or
* POLARSSL_ERR_CTR_DRBG_REQUEST_TOO_BIG
*/
int ctr_drbg_random_with_add( void *p_rng,
unsigned char *output, size_t output_len,
const unsigned char *additional, size_t add_len );
/**
* \brief CTR_DRBG generate random
*
* Note: Automatically reseeds if reseed_counter is reached.
*
* \param p_rng CTR_DRBG context
* \param output Buffer to fill
* \param output_len Length of the buffer
*
* \return 0 if successful, or
* POLARSSL_ERR_CTR_DRBG_ENTROPY_SOURCE_FAILED, or
* POLARSSL_ERR_CTR_DRBG_REQUEST_TOO_BIG
*/
int ctr_drbg_random( void *p_rng,
unsigned char *output, size_t output_len );
#if defined(POLARSSL_FS_IO)
/**
* \brief Write a seed file
*
* \param ctx CTR_DRBG context
* \param path Name of the file
*
* \return 0 if successful, 1 on file error, or
* POLARSSL_ERR_CTR_DRBG_ENTROPY_SOURCE_FAILED
*/
int ctr_drbg_write_seed_file( ctr_drbg_context *ctx, const char *path );
/**
* \brief Read and update a seed file. Seed is added to this
* instance
*
* \param ctx CTR_DRBG context
* \param path Name of the file
*
* \return 0 if successful, 1 on file error,
* POLARSSL_ERR_CTR_DRBG_ENTROPY_SOURCE_FAILED or
* POLARSSL_ERR_CTR_DRBG_INPUT_TOO_BIG
*/
int ctr_drbg_update_seed_file( ctr_drbg_context *ctx, const char *path );
#endif
/**
* \brief Checkup routine
*
* \return 0 if successful, or 1 if the test failed
*/
int ctr_drbg_self_test( int verbose );
/* Internal functions (do not call directly) */
int ctr_drbg_init_entropy_len( ctr_drbg_context *, int (*)(void *, unsigned char *, size_t), void *, const unsigned char *, size_t, size_t );
#ifdef __cplusplus
}
#endif
#endif /* ctr_drbg.h */
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