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   1 /**
   2  * \file hmac_drbg.h
   3  *
   4  * \brief HMAC_DRBG (NIST SP 800-90A)
   5  *
   6  *  Copyright (C) 2014, ARM Limited, All Rights Reserved
   7  *
   8  *  This file is part of mbed TLS (https://tls.mbed.org)
   9  *
  10  *  This program is free software; you can redistribute it and/or modify
  11  *  it under the terms of the GNU General Public License as published by
  12  *  the Free Software Foundation; either version 2 of the License, or
  13  *  (at your option) any later version.
  14  *
  15  *  This program is distributed in the hope that it will be useful,
  16  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  17  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  18  *  GNU General Public License for more details.
  19  *
  20  *  You should have received a copy of the GNU General Public License along
  21  *  with this program; if not, write to the Free Software Foundation, Inc.,
  22  *  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  23  */
  24 #ifndef MBEDTLS_HMAC_DRBG_H
  25 #define MBEDTLS_HMAC_DRBG_H
  26
  27 #include "md.h"
  28
  29 #if defined(MBEDTLS_THREADING_C)
  30 #include "mbedtls/threading.h"
  31 #endif
  32
  33 /*
  34  * Error codes
  35  */
  36 #define MBEDTLS_ERR_HMAC_DRBG_REQUEST_TOO_BIG              -0x0003  /**< Too many random requested in single call. */
  37 #define MBEDTLS_ERR_HMAC_DRBG_INPUT_TOO_BIG                -0x0005  /**< Input too large (Entropy + additional). */
  38 #define MBEDTLS_ERR_HMAC_DRBG_FILE_IO_ERROR                -0x0007  /**< Read/write error in file. */
  39 #define MBEDTLS_ERR_HMAC_DRBG_ENTROPY_SOURCE_FAILED        -0x0009  /**< The entropy source failed. */
  40
  41 /**
  42  * \name SECTION: Module settings
  43  *
  44  * The configuration options you can set for this module are in this section.
  45  * Either change them in config.h or define them on the compiler command line.
  46  * \{
  47  */
  48
  49 #if !defined(MBEDTLS_HMAC_DRBG_RESEED_INTERVAL)
  50 #define MBEDTLS_HMAC_DRBG_RESEED_INTERVAL   10000   /**< Interval before reseed is performed by default */
  51 #endif
  52
  53 #if !defined(MBEDTLS_HMAC_DRBG_MAX_INPUT)
  54 #define MBEDTLS_HMAC_DRBG_MAX_INPUT         256     /**< Maximum number of additional input bytes */
  55 #endif
  56
  57 #if !defined(MBEDTLS_HMAC_DRBG_MAX_REQUEST)
  58 #define MBEDTLS_HMAC_DRBG_MAX_REQUEST       1024    /**< Maximum number of requested bytes per call */
  59 #endif
  60
  61 #if !defined(MBEDTLS_HMAC_DRBG_MAX_SEED_INPUT)
  62 #define MBEDTLS_HMAC_DRBG_MAX_SEED_INPUT    384     /**< Maximum size of (re)seed buffer */
  63 #endif
  64
  65 /* \} name SECTION: Module settings */
  66
  67 #define MBEDTLS_HMAC_DRBG_PR_OFF   0   /**< No prediction resistance       */
  68 #define MBEDTLS_HMAC_DRBG_PR_ON    1   /**< Prediction resistance enabled  */
  69
  70 #ifdef __cplusplus
  71 extern "C" {
  72 #endif
  73
  74 /**
  75  * HMAC_DRBG context.
  76  */
  77 typedef struct
  78 {
  79     /* Working state: the key K is not stored explicitely,
  80      * but is implied by the HMAC context */
  81     mbedtls_md_context_t md_ctx;                    /*!< HMAC context (inc. K)  */
  82     unsigned char V[MBEDTLS_MD_MAX_SIZE];  /*!< V in the spec          */
  83     int reseed_counter;                     /*!< reseed counter         */
  84
  85     /* Administrative state */
  86     size_t entropy_len;         /*!< entropy bytes grabbed on each (re)seed */
  87     int prediction_resistance;  /*!< enable prediction resistance (Automatic
  88                                      reseed before every random generation) */
  89     int reseed_interval;        /*!< reseed interval   */
  90
  91     /* Callbacks */
  92     int (*f_entropy)(void *, unsigned char *, size_t); /*!< entropy function */
  93     void *p_entropy;            /*!< context for the entropy function        */
  94
  95 #if defined(MBEDTLS_THREADING_C)
  96     mbedtls_threading_mutex_t mutex;
  97 #endif
  98 } mbedtls_hmac_drbg_context;
  99
 100 /**
 101  * \brief               HMAC_DRBG context initialization
 102  *                      Makes the context ready for mbetls_hmac_drbg_seed(),
 103  *                      mbedtls_hmac_drbg_seed_buf() or
 104  *                      mbedtls_hmac_drbg_free().
 105  *
 106  * \param ctx           HMAC_DRBG context to be initialized
 107  */
 108 void mbedtls_hmac_drbg_init( mbedtls_hmac_drbg_context *ctx );
 109
 110 /**
 111  * \brief               HMAC_DRBG initial seeding
 112  *                      Seed and setup entropy source for future reseeds.
 113  *
 114  * \param ctx           HMAC_DRBG context to be seeded
 115  * \param md_info       MD algorithm to use for HMAC_DRBG
 116  * \param f_entropy     Entropy callback (p_entropy, buffer to fill, buffer
 117  *                      length)
 118  * \param p_entropy     Entropy context
 119  * \param custom        Personalization data (Device specific identifiers)
 120  *                      (Can be NULL)
 121  * \param len           Length of personalization data
 122  *
 123  * \note                The "security strength" as defined by NIST is set to:
 124  *                      128 bits if md_alg is SHA-1,
 125  *                      192 bits if md_alg is SHA-224,
 126  *                      256 bits if md_alg is SHA-256 or higher.
 127  *                      Note that SHA-256 is just as efficient as SHA-224.
 128  *
 129  * \return              0 if successful, or
 130  *                      MBEDTLS_ERR_MD_BAD_INPUT_DATA, or
 131  *                      MBEDTLS_ERR_MD_ALLOC_FAILED, or
 132  *                      MBEDTLS_ERR_HMAC_DRBG_ENTROPY_SOURCE_FAILED.
 133  */
 134 int mbedtls_hmac_drbg_seed( mbedtls_hmac_drbg_context *ctx,
 135                     const mbedtls_md_info_t * md_info,
 136                     int (*f_entropy)(void *, unsigned char *, size_t),
 137                     void *p_entropy,
 138                     const unsigned char *custom,
 139                     size_t len );
 140
 141 /**
 142  * \brief               Initilisation of simpified HMAC_DRBG (never reseeds).
 143  *                      (For use with deterministic ECDSA.)
 144  *
 145  * \param ctx           HMAC_DRBG context to be initialised
 146  * \param md_info       MD algorithm to use for HMAC_DRBG
 147  * \param data          Concatenation of entropy string and additional data
 148  * \param data_len      Length of data in bytes
 149  *
 150  * \return              0 if successful, or
 151  *                      MBEDTLS_ERR_MD_BAD_INPUT_DATA, or
 152  *                      MBEDTLS_ERR_MD_ALLOC_FAILED.
 153  */
 154 int mbedtls_hmac_drbg_seed_buf( mbedtls_hmac_drbg_context *ctx,
 155                         const mbedtls_md_info_t * md_info,
 156                         const unsigned char *data, size_t data_len );
 157
 158 /**
 159  * \brief               Enable / disable prediction resistance (Default: Off)
 160  *
 161  * Note: If enabled, entropy is used for ctx->entropy_len before each call!
 162  *       Only use this if you have ample supply of good entropy!
 163  *
 164  * \param ctx           HMAC_DRBG context
 165  * \param resistance    MBEDTLS_HMAC_DRBG_PR_ON or MBEDTLS_HMAC_DRBG_PR_OFF
 166  */
 167 void mbedtls_hmac_drbg_set_prediction_resistance( mbedtls_hmac_drbg_context *ctx,
 168                                           int resistance );
 169
 170 /**
 171  * \brief               Set the amount of entropy grabbed on each reseed
 172  *                      (Default: given by the security strength, which
 173  *                      depends on the hash used, see \c mbedtls_hmac_drbg_init() )
 174  *
 175  * \param ctx           HMAC_DRBG context
 176  * \param len           Amount of entropy to grab, in bytes
 177  */
 178 void mbedtls_hmac_drbg_set_entropy_len( mbedtls_hmac_drbg_context *ctx,
 179                                 size_t len );
 180
 181 /**
 182  * \brief               Set the reseed interval
 183  *                      (Default: MBEDTLS_HMAC_DRBG_RESEED_INTERVAL)
 184  *
 185  * \param ctx           HMAC_DRBG context
 186  * \param interval      Reseed interval
 187  */
 188 void mbedtls_hmac_drbg_set_reseed_interval( mbedtls_hmac_drbg_context *ctx,
 189                                     int interval );
 190
 191 /**
 192  * \brief               HMAC_DRBG update state
 193  *
 194  * \param ctx           HMAC_DRBG context
 195  * \param additional    Additional data to update state with, or NULL
 196  * \param add_len       Length of additional data, or 0
 197  *
 198  * \note                Additional data is optional, pass NULL and 0 as second
 199  *                      third argument if no additional data is being used.
 200  */
 201 void mbedtls_hmac_drbg_update( mbedtls_hmac_drbg_context *ctx,
 202                        const unsigned char *additional, size_t add_len );
 203
 204 /**
 205  * \brief               HMAC_DRBG reseeding (extracts data from entropy source)
 206  *
 207  * \param ctx           HMAC_DRBG context
 208  * \param additional    Additional data to add to state (Can be NULL)
 209  * \param len           Length of additional data
 210  *
 211  * \return              0 if successful, or
 212  *                      MBEDTLS_ERR_HMAC_DRBG_ENTROPY_SOURCE_FAILED
 213  */
 214 int mbedtls_hmac_drbg_reseed( mbedtls_hmac_drbg_context *ctx,
 215                       const unsigned char *additional, size_t len );
 216
 217 /**
 218  * \brief               HMAC_DRBG generate random with additional update input
 219  *
 220  * Note: Automatically reseeds if reseed_counter is reached or PR is enabled.
 221  *
 222  * \param p_rng         HMAC_DRBG context
 223  * \param output        Buffer to fill
 224  * \param output_len    Length of the buffer
 225  * \param additional    Additional data to update with (can be NULL)
 226  * \param add_len       Length of additional data (can be 0)
 227  *
 228  * \return              0 if successful, or
 229  *                      MBEDTLS_ERR_HMAC_DRBG_ENTROPY_SOURCE_FAILED, or
 230  *                      MBEDTLS_ERR_HMAC_DRBG_REQUEST_TOO_BIG, or
 231  *                      MBEDTLS_ERR_HMAC_DRBG_INPUT_TOO_BIG.
 232  */
 233 int mbedtls_hmac_drbg_random_with_add( void *p_rng,
 234                                unsigned char *output, size_t output_len,
 235                                const unsigned char *additional,
 236                                size_t add_len );
 237
 238 /**
 239  * \brief               HMAC_DRBG generate random
 240  *
 241  * Note: Automatically reseeds if reseed_counter is reached or PR is enabled.
 242  *
 243  * \param p_rng         HMAC_DRBG context
 244  * \param output        Buffer to fill
 245  * \param out_len       Length of the buffer
 246  *
 247  * \return              0 if successful, or
 248  *                      MBEDTLS_ERR_HMAC_DRBG_ENTROPY_SOURCE_FAILED, or
 249  *                      MBEDTLS_ERR_HMAC_DRBG_REQUEST_TOO_BIG
 250  */
 251 int mbedtls_hmac_drbg_random( void *p_rng, unsigned char *output, size_t out_len );
 252
 253 /**
 254  * \brief               Free an HMAC_DRBG context
 255  *
 256  * \param ctx           HMAC_DRBG context to free.
 257  */
 258 void mbedtls_hmac_drbg_free( mbedtls_hmac_drbg_context *ctx );
 259
 260 #if defined(MBEDTLS_FS_IO)
 261 /**
 262  * \brief               Write a seed file
 263  *
 264  * \param ctx           HMAC_DRBG context
 265  * \param path          Name of the file
 266  *
 267  * \return              0 if successful, 1 on file error, or
 268  *                      MBEDTLS_ERR_HMAC_DRBG_ENTROPY_SOURCE_FAILED
 269  */
 270 int mbedtls_hmac_drbg_write_seed_file( mbedtls_hmac_drbg_context *ctx, const char *path );
 271
 272 /**
 273  * \brief               Read and update a seed file. Seed is added to this
 274  *                      instance
 275  *
 276  * \param ctx           HMAC_DRBG context
 277  * \param path          Name of the file
 278  *
 279  * \return              0 if successful, 1 on file error,
 280  *                      MBEDTLS_ERR_HMAC_DRBG_ENTROPY_SOURCE_FAILED or
 281  *                      MBEDTLS_ERR_HMAC_DRBG_INPUT_TOO_BIG
 282  */
 283 int mbedtls_hmac_drbg_update_seed_file( mbedtls_hmac_drbg_context *ctx, const char *path );
 284 #endif /* MBEDTLS_FS_IO */
 285
 286
 287 #if defined(MBEDTLS_SELF_TEST)
 288 /**
 289  * \brief               Checkup routine
 290  *
 291  * \return              0 if successful, or 1 if the test failed
 292  */
 293 int mbedtls_hmac_drbg_self_test( int verbose );
 294 #endif
 295
 296 #ifdef __cplusplus
 297 }
 298 #endif
 299
 300 #endif /* hmac_drbg.h */