1 /** 2 * \file ctr_drbg.h 3 * 4 * \brief This file contains definitions and functions for the 5 * CTR_DRBG pseudorandom generator. 6 * 7 * CTR_DRBG is a standardized way of building a PRNG from a block-cipher 8 * in counter mode operation, as defined in <em>NIST SP 800-90A: 9 * Recommendation for Random Number Generation Using Deterministic Random 10 * Bit Generators</em>. 11 * 12 * The Mbed TLS implementation of CTR_DRBG uses AES-256 (default) or AES-128 13 * (if \c MBEDTLS_CTR_DRBG_USE_128_BIT_KEY is enabled at compile time) 14 * as the underlying block cipher, with a derivation function. 15 * 16 * The security strength as defined in NIST SP 800-90A is 17 * 128 bits when AES-128 is used (\c MBEDTLS_CTR_DRBG_USE_128_BIT_KEY enabled) 18 * and 256 bits otherwise, provided that #MBEDTLS_CTR_DRBG_ENTROPY_LEN is 19 * kept at its default value (and not overridden in mbedtls_config.h) and that the 20 * DRBG instance is set up with default parameters. 21 * See the documentation of mbedtls_ctr_drbg_seed() for more 22 * information. 23 */ 24 /* 25 * Copyright The Mbed TLS Contributors 26 * SPDX-License-Identifier: Apache-2.0 27 * 28 * Licensed under the Apache License, Version 2.0 (the "License"); you may 29 * not use this file except in compliance with the License. 30 * You may obtain a copy of the License at 31 * 32 * http://www.apache.org/licenses/LICENSE-2.0 33 * 34 * Unless required by applicable law or agreed to in writing, software 35 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT 36 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 37 * See the License for the specific language governing permissions and 38 * limitations under the License. 39 */ 40 41 #ifndef MBEDTLS_CTR_DRBG_H 42 #define MBEDTLS_CTR_DRBG_H 43 #include "mbedtls/private_access.h" 44 45 #include "mbedtls/build_info.h" 46 47 #include "mbedtls/aes.h" 48 49 #if defined(MBEDTLS_THREADING_C) 50 #include "mbedtls/threading.h" 51 #endif 52 53 /** The entropy source failed. */ 54 #define MBEDTLS_ERR_CTR_DRBG_ENTROPY_SOURCE_FAILED -0x0034 55 /** The requested random buffer length is too big. */ 56 #define MBEDTLS_ERR_CTR_DRBG_REQUEST_TOO_BIG -0x0036 57 /** The input (entropy + additional data) is too large. */ 58 #define MBEDTLS_ERR_CTR_DRBG_INPUT_TOO_BIG -0x0038 59 /** Read or write error in file. */ 60 #define MBEDTLS_ERR_CTR_DRBG_FILE_IO_ERROR -0x003A 61 62 #define MBEDTLS_CTR_DRBG_BLOCKSIZE 16 /**< The block size used by the cipher. */ 63 64 #if defined(MBEDTLS_CTR_DRBG_USE_128_BIT_KEY) 65 #define MBEDTLS_CTR_DRBG_KEYSIZE 16 66 /**< The key size in bytes used by the cipher. 67 * 68 * Compile-time choice: 16 bytes (128 bits) 69 * because #MBEDTLS_CTR_DRBG_USE_128_BIT_KEY is enabled. 70 */ 71 #else 72 #define MBEDTLS_CTR_DRBG_KEYSIZE 32 73 /**< The key size in bytes used by the cipher. 74 * 75 * Compile-time choice: 32 bytes (256 bits) 76 * because \c MBEDTLS_CTR_DRBG_USE_128_BIT_KEY is disabled. 77 */ 78 #endif 79 80 #define MBEDTLS_CTR_DRBG_KEYBITS (MBEDTLS_CTR_DRBG_KEYSIZE * 8) /**< The key size for the DRBG operation, in bits. */ 81 #define MBEDTLS_CTR_DRBG_SEEDLEN (MBEDTLS_CTR_DRBG_KEYSIZE + MBEDTLS_CTR_DRBG_BLOCKSIZE) /**< The seed length, calculated as (counter + AES key). */ 82 83 /** 84 * \name SECTION: Module settings 85 * 86 * The configuration options you can set for this module are in this section. 87 * Either change them in mbedtls_config.h or define them using the compiler command 88 * line. 89 * \{ 90 */ 91 92 /** \def MBEDTLS_CTR_DRBG_ENTROPY_LEN 93 * 94 * \brief The amount of entropy used per seed by default, in bytes. 95 */ 96 #if !defined(MBEDTLS_CTR_DRBG_ENTROPY_LEN) 97 #if defined(MBEDTLS_SHA512_C) && !defined(MBEDTLS_ENTROPY_FORCE_SHA256) 98 /** This is 48 bytes because the entropy module uses SHA-512 99 * (\c MBEDTLS_ENTROPY_FORCE_SHA256 is disabled). 100 */ 101 #define MBEDTLS_CTR_DRBG_ENTROPY_LEN 48 102 103 #else /* defined(MBEDTLS_SHA512_C) && !defined(MBEDTLS_ENTROPY_FORCE_SHA256) */ 104 105 /** This is 32 bytes because the entropy module uses SHA-256 106 * (the SHA512 module is disabled or 107 * \c MBEDTLS_ENTROPY_FORCE_SHA256 is enabled). 108 */ 109 #if !defined(MBEDTLS_CTR_DRBG_USE_128_BIT_KEY) 110 /** \warning To achieve a 256-bit security strength, you must pass a nonce 111 * to mbedtls_ctr_drbg_seed(). 112 */ 113 #endif /* !defined(MBEDTLS_CTR_DRBG_USE_128_BIT_KEY) */ 114 #define MBEDTLS_CTR_DRBG_ENTROPY_LEN 32 115 #endif /* defined(MBEDTLS_SHA512_C) && !defined(MBEDTLS_ENTROPY_FORCE_SHA256) */ 116 #endif /* !defined(MBEDTLS_CTR_DRBG_ENTROPY_LEN) */ 117 118 #if !defined(MBEDTLS_CTR_DRBG_RESEED_INTERVAL) 119 #define MBEDTLS_CTR_DRBG_RESEED_INTERVAL 10000 120 /**< The interval before reseed is performed by default. */ 121 #endif 122 123 #if !defined(MBEDTLS_CTR_DRBG_MAX_INPUT) 124 #define MBEDTLS_CTR_DRBG_MAX_INPUT 256 125 /**< The maximum number of additional input Bytes. */ 126 #endif 127 128 #if !defined(MBEDTLS_CTR_DRBG_MAX_REQUEST) 129 #define MBEDTLS_CTR_DRBG_MAX_REQUEST 1024 130 /**< The maximum number of requested Bytes per call. */ 131 #endif 132 133 #if !defined(MBEDTLS_CTR_DRBG_MAX_SEED_INPUT) 134 #define MBEDTLS_CTR_DRBG_MAX_SEED_INPUT 384 135 /**< The maximum size of seed or reseed buffer in bytes. */ 136 #endif 137 138 /** \} name SECTION: Module settings */ 139 140 #define MBEDTLS_CTR_DRBG_PR_OFF 0 141 /**< Prediction resistance is disabled. */ 142 #define MBEDTLS_CTR_DRBG_PR_ON 1 143 /**< Prediction resistance is enabled. */ 144 145 #ifdef __cplusplus 146 extern "C" { 147 #endif 148 149 #if MBEDTLS_CTR_DRBG_ENTROPY_LEN >= MBEDTLS_CTR_DRBG_KEYSIZE * 3 / 2 150 /** The default length of the nonce read from the entropy source. 151 * 152 * This is \c 0 because a single read from the entropy source is sufficient 153 * to include a nonce. 154 * See the documentation of mbedtls_ctr_drbg_seed() for more information. 155 */ 156 #define MBEDTLS_CTR_DRBG_ENTROPY_NONCE_LEN 0 157 #else 158 /** The default length of the nonce read from the entropy source. 159 * 160 * This is half of the default entropy length because a single read from 161 * the entropy source does not provide enough material to form a nonce. 162 * See the documentation of mbedtls_ctr_drbg_seed() for more information. 163 */ 164 #define MBEDTLS_CTR_DRBG_ENTROPY_NONCE_LEN (MBEDTLS_CTR_DRBG_ENTROPY_LEN + 1) / 2 165 #endif 166 167 /** 168 * \brief The CTR_DRBG context structure. 169 */ 170 typedef struct mbedtls_ctr_drbg_context { 171 unsigned char MBEDTLS_PRIVATE(counter)[16]; /*!< The counter (V). */ 172 int MBEDTLS_PRIVATE(reseed_counter); /*!< The reseed counter. 173 * This is the number of requests that have 174 * been made since the last (re)seeding, 175 * minus one. 176 * Before the initial seeding, this field 177 * contains the amount of entropy in bytes 178 * to use as a nonce for the initial seeding, 179 * or -1 if no nonce length has been explicitly 180 * set (see mbedtls_ctr_drbg_set_nonce_len()). 181 */ 182 int MBEDTLS_PRIVATE(prediction_resistance); /*!< This determines whether prediction 183 resistance is enabled, that is 184 whether to systematically reseed before 185 each random generation. */ 186 size_t MBEDTLS_PRIVATE(entropy_len); /*!< The amount of entropy grabbed on each 187 seed or reseed operation, in bytes. */ 188 int MBEDTLS_PRIVATE(reseed_interval); /*!< The reseed interval. 189 * This is the maximum number of requests 190 * that can be made between reseedings. */ 191 192 mbedtls_aes_context MBEDTLS_PRIVATE(aes_ctx); /*!< The AES context. */ 193 194 /* 195 * Callbacks (Entropy) 196 */ 197 int(*MBEDTLS_PRIVATE(f_entropy))(void *, unsigned char *, size_t); 198 /*!< The entropy callback function. */ 199 200 void *MBEDTLS_PRIVATE(p_entropy); /*!< The context for the entropy function. */ 201 202 #if defined(MBEDTLS_THREADING_C) 203 /* Invariant: the mutex is initialized if and only if f_entropy != NULL. 204 * This means that the mutex is initialized during the initial seeding 205 * in mbedtls_ctr_drbg_seed() and freed in mbedtls_ctr_drbg_free(). 206 * 207 * Note that this invariant may change without notice. Do not rely on it 208 * and do not access the mutex directly in application code. 209 */ 210 mbedtls_threading_mutex_t MBEDTLS_PRIVATE(mutex); 211 #endif 212 } 213 mbedtls_ctr_drbg_context; 214 215 /** 216 * \brief This function initializes the CTR_DRBG context, 217 * and prepares it for mbedtls_ctr_drbg_seed() 218 * or mbedtls_ctr_drbg_free(). 219 * 220 * \note The reseed interval is 221 * #MBEDTLS_CTR_DRBG_RESEED_INTERVAL by default. 222 * You can override it by calling 223 * mbedtls_ctr_drbg_set_reseed_interval(). 224 * 225 * \param ctx The CTR_DRBG context to initialize. 226 */ 227 void mbedtls_ctr_drbg_init(mbedtls_ctr_drbg_context *ctx); 228 229 /** 230 * \brief This function seeds and sets up the CTR_DRBG 231 * entropy source for future reseeds. 232 * 233 * A typical choice for the \p f_entropy and \p p_entropy parameters is 234 * to use the entropy module: 235 * - \p f_entropy is mbedtls_entropy_func(); 236 * - \p p_entropy is an instance of ::mbedtls_entropy_context initialized 237 * with mbedtls_entropy_init() (which registers the platform's default 238 * entropy sources). 239 * 240 * The entropy length is #MBEDTLS_CTR_DRBG_ENTROPY_LEN by default. 241 * You can override it by calling mbedtls_ctr_drbg_set_entropy_len(). 242 * 243 * The entropy nonce length is: 244 * - \c 0 if the entropy length is at least 3/2 times the entropy length, 245 * which guarantees that the security strength is the maximum permitted 246 * by the key size and entropy length according to NIST SP 800-90A §10.2.1; 247 * - Half the entropy length otherwise. 248 * You can override it by calling mbedtls_ctr_drbg_set_nonce_len(). 249 * With the default entropy length, the entropy nonce length is 250 * #MBEDTLS_CTR_DRBG_ENTROPY_NONCE_LEN. 251 * 252 * You can provide a nonce and personalization string in addition to the 253 * entropy source, to make this instantiation as unique as possible. 254 * See SP 800-90A §8.6.7 for more details about nonces. 255 * 256 * The _seed_material_ value passed to the derivation function in 257 * the CTR_DRBG Instantiate Process described in NIST SP 800-90A §10.2.1.3.2 258 * is the concatenation of the following strings: 259 * - A string obtained by calling \p f_entropy function for the entropy 260 * length. 261 */ 262 #if MBEDTLS_CTR_DRBG_ENTROPY_NONCE_LEN == 0 263 /** 264 * - If mbedtls_ctr_drbg_set_nonce_len() has been called, a string 265 * obtained by calling \p f_entropy function for the specified length. 266 */ 267 #else 268 /** 269 * - A string obtained by calling \p f_entropy function for the entropy nonce 270 * length. If the entropy nonce length is \c 0, this function does not 271 * make a second call to \p f_entropy. 272 */ 273 #endif 274 #if defined(MBEDTLS_THREADING_C) 275 /** 276 * \note When Mbed TLS is built with threading support, 277 * after this function returns successfully, 278 * it is safe to call mbedtls_ctr_drbg_random() 279 * from multiple threads. Other operations, including 280 * reseeding, are not thread-safe. 281 */ 282 #endif /* MBEDTLS_THREADING_C */ 283 /** 284 * - The \p custom string. 285 * 286 * \note To achieve the nominal security strength permitted 287 * by CTR_DRBG, the entropy length must be: 288 * - at least 16 bytes for a 128-bit strength 289 * (maximum achievable strength when using AES-128); 290 * - at least 32 bytes for a 256-bit strength 291 * (maximum achievable strength when using AES-256). 292 * 293 * In addition, if you do not pass a nonce in \p custom, 294 * the sum of the entropy length 295 * and the entropy nonce length must be: 296 * - at least 24 bytes for a 128-bit strength 297 * (maximum achievable strength when using AES-128); 298 * - at least 48 bytes for a 256-bit strength 299 * (maximum achievable strength when using AES-256). 300 * 301 * \param ctx The CTR_DRBG context to seed. 302 * It must have been initialized with 303 * mbedtls_ctr_drbg_init(). 304 * After a successful call to mbedtls_ctr_drbg_seed(), 305 * you may not call mbedtls_ctr_drbg_seed() again on 306 * the same context unless you call 307 * mbedtls_ctr_drbg_free() and mbedtls_ctr_drbg_init() 308 * again first. 309 * After a failed call to mbedtls_ctr_drbg_seed(), 310 * you must call mbedtls_ctr_drbg_free(). 311 * \param f_entropy The entropy callback, taking as arguments the 312 * \p p_entropy context, the buffer to fill, and the 313 * length of the buffer. 314 * \p f_entropy is always called with a buffer size 315 * less than or equal to the entropy length. 316 * \param p_entropy The entropy context to pass to \p f_entropy. 317 * \param custom The personalization string. 318 * This can be \c NULL, in which case the personalization 319 * string is empty regardless of the value of \p len. 320 * \param len The length of the personalization string. 321 * This must be at most 322 * #MBEDTLS_CTR_DRBG_MAX_SEED_INPUT 323 * - #MBEDTLS_CTR_DRBG_ENTROPY_LEN. 324 * 325 * \return \c 0 on success. 326 * \return #MBEDTLS_ERR_CTR_DRBG_ENTROPY_SOURCE_FAILED on failure. 327 */ 328 int mbedtls_ctr_drbg_seed(mbedtls_ctr_drbg_context *ctx, 329 int (*f_entropy)(void *, unsigned char *, size_t), 330 void *p_entropy, 331 const unsigned char *custom, 332 size_t len); 333 334 /** 335 * \brief This function resets CTR_DRBG context to the state immediately 336 * after initial call of mbedtls_ctr_drbg_init(). 337 * 338 * \param ctx The CTR_DRBG context to clear. 339 */ 340 void mbedtls_ctr_drbg_free(mbedtls_ctr_drbg_context *ctx); 341 342 /** 343 * \brief This function turns prediction resistance on or off. 344 * The default value is off. 345 * 346 * \note If enabled, entropy is gathered at the beginning of 347 * every call to mbedtls_ctr_drbg_random_with_add() 348 * or mbedtls_ctr_drbg_random(). 349 * Only use this if your entropy source has sufficient 350 * throughput. 351 * 352 * \param ctx The CTR_DRBG context. 353 * \param resistance #MBEDTLS_CTR_DRBG_PR_ON or #MBEDTLS_CTR_DRBG_PR_OFF. 354 */ 355 void mbedtls_ctr_drbg_set_prediction_resistance(mbedtls_ctr_drbg_context *ctx, 356 int resistance); 357 358 /** 359 * \brief This function sets the amount of entropy grabbed on each 360 * seed or reseed. 361 * 362 * The default value is #MBEDTLS_CTR_DRBG_ENTROPY_LEN. 363 * 364 * \note The security strength of CTR_DRBG is bounded by the 365 * entropy length. Thus: 366 * - When using AES-256 367 * (\c MBEDTLS_CTR_DRBG_USE_128_BIT_KEY is disabled, 368 * which is the default), 369 * \p len must be at least 32 (in bytes) 370 * to achieve a 256-bit strength. 371 * - When using AES-128 372 * (\c MBEDTLS_CTR_DRBG_USE_128_BIT_KEY is enabled) 373 * \p len must be at least 16 (in bytes) 374 * to achieve a 128-bit strength. 375 * 376 * \param ctx The CTR_DRBG context. 377 * \param len The amount of entropy to grab, in bytes. 378 * This must be at most #MBEDTLS_CTR_DRBG_MAX_SEED_INPUT 379 * and at most the maximum length accepted by the 380 * entropy function that is set in the context. 381 */ 382 void mbedtls_ctr_drbg_set_entropy_len(mbedtls_ctr_drbg_context *ctx, 383 size_t len); 384 385 /** 386 * \brief This function sets the amount of entropy grabbed 387 * as a nonce for the initial seeding. 388 * 389 * Call this function before calling mbedtls_ctr_drbg_seed() to read 390 * a nonce from the entropy source during the initial seeding. 391 * 392 * \param ctx The CTR_DRBG context. 393 * \param len The amount of entropy to grab for the nonce, in bytes. 394 * This must be at most #MBEDTLS_CTR_DRBG_MAX_SEED_INPUT 395 * and at most the maximum length accepted by the 396 * entropy function that is set in the context. 397 * 398 * \return \c 0 on success. 399 * \return #MBEDTLS_ERR_CTR_DRBG_INPUT_TOO_BIG if \p len is 400 * more than #MBEDTLS_CTR_DRBG_MAX_SEED_INPUT. 401 * \return #MBEDTLS_ERR_CTR_DRBG_ENTROPY_SOURCE_FAILED 402 * if the initial seeding has already taken place. 403 */ 404 int mbedtls_ctr_drbg_set_nonce_len(mbedtls_ctr_drbg_context *ctx, 405 size_t len); 406 407 /** 408 * \brief This function sets the reseed interval. 409 * 410 * The reseed interval is the number of calls to mbedtls_ctr_drbg_random() 411 * or mbedtls_ctr_drbg_random_with_add() after which the entropy function 412 * is called again. 413 * 414 * The default value is #MBEDTLS_CTR_DRBG_RESEED_INTERVAL. 415 * 416 * \param ctx The CTR_DRBG context. 417 * \param interval The reseed interval. 418 */ 419 void mbedtls_ctr_drbg_set_reseed_interval(mbedtls_ctr_drbg_context *ctx, 420 int interval); 421 422 /** 423 * \brief This function reseeds the CTR_DRBG context, that is 424 * extracts data from the entropy source. 425 * 426 * \note This function is not thread-safe. It is not safe 427 * to call this function if another thread might be 428 * concurrently obtaining random numbers from the same 429 * context or updating or reseeding the same context. 430 * 431 * \param ctx The CTR_DRBG context. 432 * \param additional Additional data to add to the state. Can be \c NULL. 433 * \param len The length of the additional data. 434 * This must be less than 435 * #MBEDTLS_CTR_DRBG_MAX_SEED_INPUT - \c entropy_len 436 * where \c entropy_len is the entropy length 437 * configured for the context. 438 * 439 * \return \c 0 on success. 440 * \return #MBEDTLS_ERR_CTR_DRBG_ENTROPY_SOURCE_FAILED on failure. 441 */ 442 int mbedtls_ctr_drbg_reseed(mbedtls_ctr_drbg_context *ctx, 443 const unsigned char *additional, size_t len); 444 445 /** 446 * \brief This function updates the state of the CTR_DRBG context. 447 * 448 * \note This function is not thread-safe. It is not safe 449 * to call this function if another thread might be 450 * concurrently obtaining random numbers from the same 451 * context or updating or reseeding the same context. 452 * 453 * \param ctx The CTR_DRBG context. 454 * \param additional The data to update the state with. This must not be 455 * \c NULL unless \p add_len is \c 0. 456 * \param add_len Length of \p additional in bytes. This must be at 457 * most #MBEDTLS_CTR_DRBG_MAX_SEED_INPUT. 458 * 459 * \return \c 0 on success. 460 * \return #MBEDTLS_ERR_CTR_DRBG_INPUT_TOO_BIG if 461 * \p add_len is more than 462 * #MBEDTLS_CTR_DRBG_MAX_SEED_INPUT. 463 * \return An error from the underlying AES cipher on failure. 464 */ 465 int mbedtls_ctr_drbg_update(mbedtls_ctr_drbg_context *ctx, 466 const unsigned char *additional, 467 size_t add_len); 468 469 /** 470 * \brief This function updates a CTR_DRBG instance with additional 471 * data and uses it to generate random data. 472 * 473 * This function automatically reseeds if the reseed counter is exceeded 474 * or prediction resistance is enabled. 475 * 476 * \note This function is not thread-safe. It is not safe 477 * to call this function if another thread might be 478 * concurrently obtaining random numbers from the same 479 * context or updating or reseeding the same context. 480 * 481 * \param p_rng The CTR_DRBG context. This must be a pointer to a 482 * #mbedtls_ctr_drbg_context structure. 483 * \param output The buffer to fill. 484 * \param output_len The length of the buffer in bytes. 485 * \param additional Additional data to update. Can be \c NULL, in which 486 * case the additional data is empty regardless of 487 * the value of \p add_len. 488 * \param add_len The length of the additional data 489 * if \p additional is not \c NULL. 490 * This must be less than #MBEDTLS_CTR_DRBG_MAX_INPUT 491 * and less than 492 * #MBEDTLS_CTR_DRBG_MAX_SEED_INPUT - \c entropy_len 493 * where \c entropy_len is the entropy length 494 * configured for the context. 495 * 496 * \return \c 0 on success. 497 * \return #MBEDTLS_ERR_CTR_DRBG_ENTROPY_SOURCE_FAILED or 498 * #MBEDTLS_ERR_CTR_DRBG_REQUEST_TOO_BIG on failure. 499 */ 500 int mbedtls_ctr_drbg_random_with_add(void *p_rng, 501 unsigned char *output, size_t output_len, 502 const unsigned char *additional, size_t add_len); 503 504 /** 505 * \brief This function uses CTR_DRBG to generate random data. 506 * 507 * This function automatically reseeds if the reseed counter is exceeded 508 * or prediction resistance is enabled. 509 */ 510 #if defined(MBEDTLS_THREADING_C) 511 /** 512 * \note When Mbed TLS is built with threading support, 513 * it is safe to call mbedtls_ctr_drbg_random() 514 * from multiple threads. Other operations, including 515 * reseeding, are not thread-safe. 516 */ 517 #endif /* MBEDTLS_THREADING_C */ 518 /** 519 * \param p_rng The CTR_DRBG context. This must be a pointer to a 520 * #mbedtls_ctr_drbg_context structure. 521 * \param output The buffer to fill. 522 * \param output_len The length of the buffer in bytes. 523 * 524 * \return \c 0 on success. 525 * \return #MBEDTLS_ERR_CTR_DRBG_ENTROPY_SOURCE_FAILED or 526 * #MBEDTLS_ERR_CTR_DRBG_REQUEST_TOO_BIG on failure. 527 */ 528 int mbedtls_ctr_drbg_random(void *p_rng, 529 unsigned char *output, size_t output_len); 530 531 #if defined(MBEDTLS_FS_IO) 532 /** 533 * \brief This function writes a seed file. 534 * 535 * \param ctx The CTR_DRBG context. 536 * \param path The name of the file. 537 * 538 * \return \c 0 on success. 539 * \return #MBEDTLS_ERR_CTR_DRBG_FILE_IO_ERROR on file error. 540 * \return #MBEDTLS_ERR_CTR_DRBG_ENTROPY_SOURCE_FAILED on reseed 541 * failure. 542 */ 543 int mbedtls_ctr_drbg_write_seed_file(mbedtls_ctr_drbg_context *ctx, const char *path); 544 545 /** 546 * \brief This function reads and updates a seed file. The seed 547 * is added to this instance. 548 * 549 * \param ctx The CTR_DRBG context. 550 * \param path The name of the file. 551 * 552 * \return \c 0 on success. 553 * \return #MBEDTLS_ERR_CTR_DRBG_FILE_IO_ERROR on file error. 554 * \return #MBEDTLS_ERR_CTR_DRBG_ENTROPY_SOURCE_FAILED on 555 * reseed failure. 556 * \return #MBEDTLS_ERR_CTR_DRBG_INPUT_TOO_BIG if the existing 557 * seed file is too large. 558 */ 559 int mbedtls_ctr_drbg_update_seed_file(mbedtls_ctr_drbg_context *ctx, const char *path); 560 #endif /* MBEDTLS_FS_IO */ 561 562 #if defined(MBEDTLS_SELF_TEST) 563 564 /** 565 * \brief The CTR_DRBG checkup routine. 566 * 567 * \return \c 0 on success. 568 * \return \c 1 on failure. 569 */ 570 int mbedtls_ctr_drbg_self_test(int verbose); 571 572 #endif /* MBEDTLS_SELF_TEST */ 573 574 #ifdef __cplusplus 575 } 576 #endif 577 578 #endif /* ctr_drbg.h */ 579