1 /** 2 * \file hmac_drbg.h 3 * 4 * \brief The HMAC_DRBG pseudorandom generator. 5 * 6 * This module implements the HMAC_DRBG pseudorandom generator described 7 * in <em>NIST SP 800-90A: Recommendation for Random Number Generation Using 8 * Deterministic Random Bit Generators</em>. 9 */ 10 /* 11 * Copyright The Mbed TLS Contributors 12 * SPDX-License-Identifier: Apache-2.0 13 * 14 * Licensed under the Apache License, Version 2.0 (the "License"); you may 15 * not use this file except in compliance with the License. 16 * You may obtain a copy of the License at 17 * 18 * http://www.apache.org/licenses/LICENSE-2.0 19 * 20 * Unless required by applicable law or agreed to in writing, software 21 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT 22 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 23 * See the License for the specific language governing permissions and 24 * limitations under the License. 25 */ 26 #ifndef MBEDTLS_HMAC_DRBG_H 27 #define MBEDTLS_HMAC_DRBG_H 28 #include "mbedtls/private_access.h" 29 30 #include "mbedtls/build_info.h" 31 32 #include "mbedtls/md.h" 33 34 #if defined(MBEDTLS_THREADING_C) 35 #include "mbedtls/threading.h" 36 #endif 37 38 /* 39 * Error codes 40 */ 41 /** Too many random requested in single call. */ 42 #define MBEDTLS_ERR_HMAC_DRBG_REQUEST_TOO_BIG -0x0003 43 /** Input too large (Entropy + additional). */ 44 #define MBEDTLS_ERR_HMAC_DRBG_INPUT_TOO_BIG -0x0005 45 /** Read/write error in file. */ 46 #define MBEDTLS_ERR_HMAC_DRBG_FILE_IO_ERROR -0x0007 47 /** The entropy source failed. */ 48 #define MBEDTLS_ERR_HMAC_DRBG_ENTROPY_SOURCE_FAILED -0x0009 49 50 /** 51 * \name SECTION: Module settings 52 * 53 * The configuration options you can set for this module are in this section. 54 * Either change them in mbedtls_config.h or define them on the compiler command line. 55 * \{ 56 */ 57 58 #if !defined(MBEDTLS_HMAC_DRBG_RESEED_INTERVAL) 59 #define MBEDTLS_HMAC_DRBG_RESEED_INTERVAL 10000 /**< Interval before reseed is performed by default */ 60 #endif 61 62 #if !defined(MBEDTLS_HMAC_DRBG_MAX_INPUT) 63 #define MBEDTLS_HMAC_DRBG_MAX_INPUT 256 /**< Maximum number of additional input bytes */ 64 #endif 65 66 #if !defined(MBEDTLS_HMAC_DRBG_MAX_REQUEST) 67 #define MBEDTLS_HMAC_DRBG_MAX_REQUEST 1024 /**< Maximum number of requested bytes per call */ 68 #endif 69 70 #if !defined(MBEDTLS_HMAC_DRBG_MAX_SEED_INPUT) 71 #define MBEDTLS_HMAC_DRBG_MAX_SEED_INPUT 384 /**< Maximum size of (re)seed buffer */ 72 #endif 73 74 /** \} name SECTION: Module settings */ 75 76 #define MBEDTLS_HMAC_DRBG_PR_OFF 0 /**< No prediction resistance */ 77 #define MBEDTLS_HMAC_DRBG_PR_ON 1 /**< Prediction resistance enabled */ 78 79 #ifdef __cplusplus 80 extern "C" { 81 #endif 82 83 /** 84 * HMAC_DRBG context. 85 */ 86 typedef struct mbedtls_hmac_drbg_context { 87 /* Working state: the key K is not stored explicitly, 88 * but is implied by the HMAC context */ 89 mbedtls_md_context_t MBEDTLS_PRIVATE(md_ctx); /*!< HMAC context (inc. K) */ 90 unsigned char MBEDTLS_PRIVATE(V)[MBEDTLS_MD_MAX_SIZE]; /*!< V in the spec */ 91 int MBEDTLS_PRIVATE(reseed_counter); /*!< reseed counter */ 92 93 /* Administrative state */ 94 size_t MBEDTLS_PRIVATE(entropy_len); /*!< entropy bytes grabbed on each (re)seed */ 95 int MBEDTLS_PRIVATE(prediction_resistance); /*!< enable prediction resistance (Automatic 96 reseed before every random generation) */ 97 int MBEDTLS_PRIVATE(reseed_interval); /*!< reseed interval */ 98 99 /* Callbacks */ 100 int(*MBEDTLS_PRIVATE(f_entropy))(void *, unsigned char *, size_t); /*!< entropy function */ 101 void *MBEDTLS_PRIVATE(p_entropy); /*!< context for the entropy function */ 102 103 #if defined(MBEDTLS_THREADING_C) 104 /* Invariant: the mutex is initialized if and only if 105 * md_ctx->md_info != NULL. This means that the mutex is initialized 106 * during the initial seeding in mbedtls_hmac_drbg_seed() or 107 * mbedtls_hmac_drbg_seed_buf() and freed in mbedtls_ctr_drbg_free(). 108 * 109 * Note that this invariant may change without notice. Do not rely on it 110 * and do not access the mutex directly in application code. 111 */ 112 mbedtls_threading_mutex_t MBEDTLS_PRIVATE(mutex); 113 #endif 114 } mbedtls_hmac_drbg_context; 115 116 /** 117 * \brief HMAC_DRBG context initialization. 118 * 119 * This function makes the context ready for mbedtls_hmac_drbg_seed(), 120 * mbedtls_hmac_drbg_seed_buf() or mbedtls_hmac_drbg_free(). 121 * 122 * \note The reseed interval is #MBEDTLS_HMAC_DRBG_RESEED_INTERVAL 123 * by default. Override this value by calling 124 * mbedtls_hmac_drbg_set_reseed_interval(). 125 * 126 * \param ctx HMAC_DRBG context to be initialized. 127 */ 128 void mbedtls_hmac_drbg_init(mbedtls_hmac_drbg_context *ctx); 129 130 /** 131 * \brief HMAC_DRBG initial seeding. 132 * 133 * Set the initial seed and set up the entropy source for future reseeds. 134 * 135 * A typical choice for the \p f_entropy and \p p_entropy parameters is 136 * to use the entropy module: 137 * - \p f_entropy is mbedtls_entropy_func(); 138 * - \p p_entropy is an instance of ::mbedtls_entropy_context initialized 139 * with mbedtls_entropy_init() (which registers the platform's default 140 * entropy sources). 141 * 142 * You can provide a personalization string in addition to the 143 * entropy source, to make this instantiation as unique as possible. 144 * 145 * \note By default, the security strength as defined by NIST is: 146 * - 128 bits if \p md_info is SHA-1; 147 * - 192 bits if \p md_info is SHA-224; 148 * - 256 bits if \p md_info is SHA-256, SHA-384 or SHA-512. 149 * Note that SHA-256 is just as efficient as SHA-224. 150 * The security strength can be reduced if a smaller 151 * entropy length is set with 152 * mbedtls_hmac_drbg_set_entropy_len(). 153 * 154 * \note The default entropy length is the security strength 155 * (converted from bits to bytes). You can override 156 * it by calling mbedtls_hmac_drbg_set_entropy_len(). 157 * 158 * \note During the initial seeding, this function calls 159 * the entropy source to obtain a nonce 160 * whose length is half the entropy length. 161 */ 162 #if defined(MBEDTLS_THREADING_C) 163 /** 164 * \note When Mbed TLS is built with threading support, 165 * after this function returns successfully, 166 * it is safe to call mbedtls_hmac_drbg_random() 167 * from multiple threads. Other operations, including 168 * reseeding, are not thread-safe. 169 */ 170 #endif /* MBEDTLS_THREADING_C */ 171 /** 172 * \param ctx HMAC_DRBG context to be seeded. 173 * \param md_info MD algorithm to use for HMAC_DRBG. 174 * \param f_entropy The entropy callback, taking as arguments the 175 * \p p_entropy context, the buffer to fill, and the 176 * length of the buffer. 177 * \p f_entropy is always called with a length that is 178 * less than or equal to the entropy length. 179 * \param p_entropy The entropy context to pass to \p f_entropy. 180 * \param custom The personalization string. 181 * This can be \c NULL, in which case the personalization 182 * string is empty regardless of the value of \p len. 183 * \param len The length of the personalization string. 184 * This must be at most #MBEDTLS_HMAC_DRBG_MAX_INPUT 185 * and also at most 186 * #MBEDTLS_HMAC_DRBG_MAX_SEED_INPUT - \p entropy_len * 3 / 2 187 * where \p entropy_len is the entropy length 188 * described above. 189 * 190 * \return \c 0 if successful. 191 * \return #MBEDTLS_ERR_MD_BAD_INPUT_DATA if \p md_info is 192 * invalid. 193 * \return #MBEDTLS_ERR_MD_ALLOC_FAILED if there was not enough 194 * memory to allocate context data. 195 * \return #MBEDTLS_ERR_HMAC_DRBG_ENTROPY_SOURCE_FAILED 196 * if the call to \p f_entropy failed. 197 */ 198 int mbedtls_hmac_drbg_seed(mbedtls_hmac_drbg_context *ctx, 199 const mbedtls_md_info_t *md_info, 200 int (*f_entropy)(void *, unsigned char *, size_t), 201 void *p_entropy, 202 const unsigned char *custom, 203 size_t len); 204 205 /** 206 * \brief Initialisation of simplified HMAC_DRBG (never reseeds). 207 * 208 * This function is meant for use in algorithms that need a pseudorandom 209 * input such as deterministic ECDSA. 210 */ 211 #if defined(MBEDTLS_THREADING_C) 212 /** 213 * \note When Mbed TLS is built with threading support, 214 * after this function returns successfully, 215 * it is safe to call mbedtls_hmac_drbg_random() 216 * from multiple threads. Other operations, including 217 * reseeding, are not thread-safe. 218 */ 219 #endif /* MBEDTLS_THREADING_C */ 220 /** 221 * \param ctx HMAC_DRBG context to be initialised. 222 * \param md_info MD algorithm to use for HMAC_DRBG. 223 * \param data Concatenation of the initial entropy string and 224 * the additional data. 225 * \param data_len Length of \p data in bytes. 226 * 227 * \return \c 0 if successful. or 228 * \return #MBEDTLS_ERR_MD_BAD_INPUT_DATA if \p md_info is 229 * invalid. 230 * \return #MBEDTLS_ERR_MD_ALLOC_FAILED if there was not enough 231 * memory to allocate context data. 232 */ 233 int mbedtls_hmac_drbg_seed_buf(mbedtls_hmac_drbg_context *ctx, 234 const mbedtls_md_info_t *md_info, 235 const unsigned char *data, size_t data_len); 236 237 /** 238 * \brief This function turns prediction resistance on or off. 239 * The default value is off. 240 * 241 * \note If enabled, entropy is gathered at the beginning of 242 * every call to mbedtls_hmac_drbg_random_with_add() 243 * or mbedtls_hmac_drbg_random(). 244 * Only use this if your entropy source has sufficient 245 * throughput. 246 * 247 * \param ctx The HMAC_DRBG context. 248 * \param resistance #MBEDTLS_HMAC_DRBG_PR_ON or #MBEDTLS_HMAC_DRBG_PR_OFF. 249 */ 250 void mbedtls_hmac_drbg_set_prediction_resistance(mbedtls_hmac_drbg_context *ctx, 251 int resistance); 252 253 /** 254 * \brief This function sets the amount of entropy grabbed on each 255 * seed or reseed. 256 * 257 * See the documentation of mbedtls_hmac_drbg_seed() for the default value. 258 * 259 * \param ctx The HMAC_DRBG context. 260 * \param len The amount of entropy to grab, in bytes. 261 */ 262 void mbedtls_hmac_drbg_set_entropy_len(mbedtls_hmac_drbg_context *ctx, 263 size_t len); 264 265 /** 266 * \brief Set the reseed interval. 267 * 268 * The reseed interval is the number of calls to mbedtls_hmac_drbg_random() 269 * or mbedtls_hmac_drbg_random_with_add() after which the entropy function 270 * is called again. 271 * 272 * The default value is #MBEDTLS_HMAC_DRBG_RESEED_INTERVAL. 273 * 274 * \param ctx The HMAC_DRBG context. 275 * \param interval The reseed interval. 276 */ 277 void mbedtls_hmac_drbg_set_reseed_interval(mbedtls_hmac_drbg_context *ctx, 278 int interval); 279 280 /** 281 * \brief This function updates the state of the HMAC_DRBG context. 282 * 283 * \note This function is not thread-safe. It is not safe 284 * to call this function if another thread might be 285 * concurrently obtaining random numbers from the same 286 * context or updating or reseeding the same context. 287 * 288 * \param ctx The HMAC_DRBG context. 289 * \param additional The data to update the state with. 290 * If this is \c NULL, there is no additional data. 291 * \param add_len Length of \p additional in bytes. 292 * Unused if \p additional is \c NULL. 293 * 294 * \return \c 0 on success, or an error from the underlying 295 * hash calculation. 296 */ 297 int mbedtls_hmac_drbg_update(mbedtls_hmac_drbg_context *ctx, 298 const unsigned char *additional, size_t add_len); 299 300 /** 301 * \brief This function reseeds the HMAC_DRBG context, that is 302 * extracts data from the entropy source. 303 * 304 * \note This function is not thread-safe. It is not safe 305 * to call this function if another thread might be 306 * concurrently obtaining random numbers from the same 307 * context or updating or reseeding the same context. 308 * 309 * \param ctx The HMAC_DRBG context. 310 * \param additional Additional data to add to the state. 311 * If this is \c NULL, there is no additional data 312 * and \p len should be \c 0. 313 * \param len The length of the additional data. 314 * This must be at most #MBEDTLS_HMAC_DRBG_MAX_INPUT 315 * and also at most 316 * #MBEDTLS_HMAC_DRBG_MAX_SEED_INPUT - \p entropy_len 317 * where \p entropy_len is the entropy length 318 * (see mbedtls_hmac_drbg_set_entropy_len()). 319 * 320 * \return \c 0 if successful. 321 * \return #MBEDTLS_ERR_HMAC_DRBG_ENTROPY_SOURCE_FAILED 322 * if a call to the entropy function failed. 323 */ 324 int mbedtls_hmac_drbg_reseed(mbedtls_hmac_drbg_context *ctx, 325 const unsigned char *additional, size_t len); 326 327 /** 328 * \brief This function updates an HMAC_DRBG instance with additional 329 * data and uses it to generate random data. 330 * 331 * This function automatically reseeds if the reseed counter is exceeded 332 * or prediction resistance is enabled. 333 * 334 * \note This function is not thread-safe. It is not safe 335 * to call this function if another thread might be 336 * concurrently obtaining random numbers from the same 337 * context or updating or reseeding the same context. 338 * 339 * \param p_rng The HMAC_DRBG context. This must be a pointer to a 340 * #mbedtls_hmac_drbg_context structure. 341 * \param output The buffer to fill. 342 * \param output_len The length of the buffer in bytes. 343 * This must be at most #MBEDTLS_HMAC_DRBG_MAX_REQUEST. 344 * \param additional Additional data to update with. 345 * If this is \c NULL, there is no additional data 346 * and \p add_len should be \c 0. 347 * \param add_len The length of the additional data. 348 * This must be at most #MBEDTLS_HMAC_DRBG_MAX_INPUT. 349 * 350 * \return \c 0 if successful. 351 * \return #MBEDTLS_ERR_HMAC_DRBG_ENTROPY_SOURCE_FAILED 352 * if a call to the entropy source failed. 353 * \return #MBEDTLS_ERR_HMAC_DRBG_REQUEST_TOO_BIG if 354 * \p output_len > #MBEDTLS_HMAC_DRBG_MAX_REQUEST. 355 * \return #MBEDTLS_ERR_HMAC_DRBG_INPUT_TOO_BIG if 356 * \p add_len > #MBEDTLS_HMAC_DRBG_MAX_INPUT. 357 */ 358 int mbedtls_hmac_drbg_random_with_add(void *p_rng, 359 unsigned char *output, size_t output_len, 360 const unsigned char *additional, 361 size_t add_len); 362 363 /** 364 * \brief This function uses HMAC_DRBG to generate random data. 365 * 366 * This function automatically reseeds if the reseed counter is exceeded 367 * or prediction resistance is enabled. 368 */ 369 #if defined(MBEDTLS_THREADING_C) 370 /** 371 * \note When Mbed TLS is built with threading support, 372 * it is safe to call mbedtls_ctr_drbg_random() 373 * from multiple threads. Other operations, including 374 * reseeding, are not thread-safe. 375 */ 376 #endif /* MBEDTLS_THREADING_C */ 377 /** 378 * \param p_rng The HMAC_DRBG context. This must be a pointer to a 379 * #mbedtls_hmac_drbg_context structure. 380 * \param output The buffer to fill. 381 * \param out_len The length of the buffer in bytes. 382 * This must be at most #MBEDTLS_HMAC_DRBG_MAX_REQUEST. 383 * 384 * \return \c 0 if successful. 385 * \return #MBEDTLS_ERR_HMAC_DRBG_ENTROPY_SOURCE_FAILED 386 * if a call to the entropy source failed. 387 * \return #MBEDTLS_ERR_HMAC_DRBG_REQUEST_TOO_BIG if 388 * \p out_len > #MBEDTLS_HMAC_DRBG_MAX_REQUEST. 389 */ 390 int mbedtls_hmac_drbg_random(void *p_rng, unsigned char *output, size_t out_len); 391 392 /** 393 * \brief This function resets HMAC_DRBG context to the state immediately 394 * after initial call of mbedtls_hmac_drbg_init(). 395 * 396 * \param ctx The HMAC_DRBG context to free. 397 */ 398 void mbedtls_hmac_drbg_free(mbedtls_hmac_drbg_context *ctx); 399 400 #if defined(MBEDTLS_FS_IO) 401 /** 402 * \brief This function writes a seed file. 403 * 404 * \param ctx The HMAC_DRBG context. 405 * \param path The name of the file. 406 * 407 * \return \c 0 on success. 408 * \return #MBEDTLS_ERR_HMAC_DRBG_FILE_IO_ERROR on file error. 409 * \return #MBEDTLS_ERR_HMAC_DRBG_ENTROPY_SOURCE_FAILED on reseed 410 * failure. 411 */ 412 int mbedtls_hmac_drbg_write_seed_file(mbedtls_hmac_drbg_context *ctx, const char *path); 413 414 /** 415 * \brief This function reads and updates a seed file. The seed 416 * is added to this instance. 417 * 418 * \param ctx The HMAC_DRBG context. 419 * \param path The name of the file. 420 * 421 * \return \c 0 on success. 422 * \return #MBEDTLS_ERR_HMAC_DRBG_FILE_IO_ERROR on file error. 423 * \return #MBEDTLS_ERR_HMAC_DRBG_ENTROPY_SOURCE_FAILED on 424 * reseed failure. 425 * \return #MBEDTLS_ERR_HMAC_DRBG_INPUT_TOO_BIG if the existing 426 * seed file is too large. 427 */ 428 int mbedtls_hmac_drbg_update_seed_file(mbedtls_hmac_drbg_context *ctx, const char *path); 429 #endif /* MBEDTLS_FS_IO */ 430 431 432 #if defined(MBEDTLS_SELF_TEST) 433 /** 434 * \brief The HMAC_DRBG Checkup routine. 435 * 436 * \return \c 0 if successful. 437 * \return \c 1 if the test failed. 438 */ 439 int mbedtls_hmac_drbg_self_test(int verbose); 440 #endif 441 442 #ifdef __cplusplus 443 } 444 #endif 445 446 #endif /* hmac_drbg.h */ 447
