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Diffstat (limited to 'include/mbedtls/ctr_drbg.h')
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diff --git a/include/mbedtls/ctr_drbg.h b/include/mbedtls/ctr_drbg.h new file mode 100644 index 000000000..2b66b534a --- /dev/null +++ b/include/mbedtls/ctr_drbg.h @@ -0,0 +1,579 @@ +/** + * \file ctr_drbg.h + * + * \brief This file contains definitions and functions for the + * CTR_DRBG pseudorandom generator. + * + * CTR_DRBG is a standardized way of building a PRNG from a block-cipher + * in counter mode operation, as defined in <em>NIST SP 800-90A: + * Recommendation for Random Number Generation Using Deterministic Random + * Bit Generators</em>. + * + * The Mbed TLS implementation of CTR_DRBG uses AES-256 (default) or AES-128 + * (if \c MBEDTLS_CTR_DRBG_USE_128_BIT_KEY is enabled at compile time) + * as the underlying block cipher, with a derivation function. + * + * The security strength as defined in NIST SP 800-90A is + * 128 bits when AES-128 is used (\c MBEDTLS_CTR_DRBG_USE_128_BIT_KEY enabled) + * and 256 bits otherwise, provided that #MBEDTLS_CTR_DRBG_ENTROPY_LEN is + * kept at its default value (and not overridden in mbedtls_config.h) and that the + * DRBG instance is set up with default parameters. + * See the documentation of mbedtls_ctr_drbg_seed() for more + * information. + */ +/* + * Copyright The Mbed TLS Contributors + * SPDX-License-Identifier: Apache-2.0 + * + * Licensed under the Apache License, Version 2.0 (the "License"); you may + * not use this file except in compliance with the License. + * You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT + * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + * See the License for the specific language governing permissions and + * limitations under the License. + */ + +#ifndef MBEDTLS_CTR_DRBG_H +#define MBEDTLS_CTR_DRBG_H +#include "mbedtls/private_access.h" + +#include "mbedtls/build_info.h" + +#include "mbedtls/aes.h" + +#if defined(MBEDTLS_THREADING_C) +#include "mbedtls/threading.h" +#endif + +/** The entropy source failed. */ +#define MBEDTLS_ERR_CTR_DRBG_ENTROPY_SOURCE_FAILED -0x0034 +/** The requested random buffer length is too big. */ +#define MBEDTLS_ERR_CTR_DRBG_REQUEST_TOO_BIG -0x0036 +/** The input (entropy + additional data) is too large. */ +#define MBEDTLS_ERR_CTR_DRBG_INPUT_TOO_BIG -0x0038 +/** Read or write error in file. */ +#define MBEDTLS_ERR_CTR_DRBG_FILE_IO_ERROR -0x003A + +#define MBEDTLS_CTR_DRBG_BLOCKSIZE 16 /**< The block size used by the cipher. */ + +#if defined(MBEDTLS_CTR_DRBG_USE_128_BIT_KEY) +#define MBEDTLS_CTR_DRBG_KEYSIZE 16 +/**< The key size in bytes used by the cipher. + * + * Compile-time choice: 16 bytes (128 bits) + * because #MBEDTLS_CTR_DRBG_USE_128_BIT_KEY is enabled. + */ +#else +#define MBEDTLS_CTR_DRBG_KEYSIZE 32 +/**< The key size in bytes used by the cipher. + * + * Compile-time choice: 32 bytes (256 bits) + * because \c MBEDTLS_CTR_DRBG_USE_128_BIT_KEY is disabled. + */ +#endif + +#define MBEDTLS_CTR_DRBG_KEYBITS ( MBEDTLS_CTR_DRBG_KEYSIZE * 8 ) /**< The key size for the DRBG operation, in bits. */ +#define MBEDTLS_CTR_DRBG_SEEDLEN ( MBEDTLS_CTR_DRBG_KEYSIZE + MBEDTLS_CTR_DRBG_BLOCKSIZE ) /**< The seed length, calculated as (counter + AES key). */ + +/** + * \name SECTION: Module settings + * + * The configuration options you can set for this module are in this section. + * Either change them in mbedtls_config.h or define them using the compiler command + * line. + * \{ + */ + +/** \def MBEDTLS_CTR_DRBG_ENTROPY_LEN + * + * \brief The amount of entropy used per seed by default, in bytes. + */ +#if !defined(MBEDTLS_CTR_DRBG_ENTROPY_LEN) +#if defined(MBEDTLS_SHA512_C) && !defined(MBEDTLS_ENTROPY_FORCE_SHA256) +/** This is 48 bytes because the entropy module uses SHA-512 + * (\c MBEDTLS_ENTROPY_FORCE_SHA256 is disabled). + */ +#define MBEDTLS_CTR_DRBG_ENTROPY_LEN 48 + +#else /* defined(MBEDTLS_SHA512_C) && !defined(MBEDTLS_ENTROPY_FORCE_SHA256) */ + +/** This is 32 bytes because the entropy module uses SHA-256 + * (the SHA512 module is disabled or + * \c MBEDTLS_ENTROPY_FORCE_SHA256 is enabled). + */ +#if !defined(MBEDTLS_CTR_DRBG_USE_128_BIT_KEY) +/** \warning To achieve a 256-bit security strength, you must pass a nonce + * to mbedtls_ctr_drbg_seed(). + */ +#endif /* !defined(MBEDTLS_CTR_DRBG_USE_128_BIT_KEY) */ +#define MBEDTLS_CTR_DRBG_ENTROPY_LEN 32 +#endif /* defined(MBEDTLS_SHA512_C) && !defined(MBEDTLS_ENTROPY_FORCE_SHA256) */ +#endif /* !defined(MBEDTLS_CTR_DRBG_ENTROPY_LEN) */ + +#if !defined(MBEDTLS_CTR_DRBG_RESEED_INTERVAL) +#define MBEDTLS_CTR_DRBG_RESEED_INTERVAL 10000 +/**< The interval before reseed is performed by default. */ +#endif + +#if !defined(MBEDTLS_CTR_DRBG_MAX_INPUT) +#define MBEDTLS_CTR_DRBG_MAX_INPUT 256 +/**< The maximum number of additional input Bytes. */ +#endif + +#if !defined(MBEDTLS_CTR_DRBG_MAX_REQUEST) +#define MBEDTLS_CTR_DRBG_MAX_REQUEST 1024 +/**< The maximum number of requested Bytes per call. */ +#endif + +#if !defined(MBEDTLS_CTR_DRBG_MAX_SEED_INPUT) +#define MBEDTLS_CTR_DRBG_MAX_SEED_INPUT 384 +/**< The maximum size of seed or reseed buffer in bytes. */ +#endif + +/** \} name SECTION: Module settings */ + +#define MBEDTLS_CTR_DRBG_PR_OFF 0 +/**< Prediction resistance is disabled. */ +#define MBEDTLS_CTR_DRBG_PR_ON 1 +/**< Prediction resistance is enabled. */ + +#ifdef __cplusplus +extern "C" { +#endif + +#if MBEDTLS_CTR_DRBG_ENTROPY_LEN >= MBEDTLS_CTR_DRBG_KEYSIZE * 3 / 2 +/** The default length of the nonce read from the entropy source. + * + * This is \c 0 because a single read from the entropy source is sufficient + * to include a nonce. + * See the documentation of mbedtls_ctr_drbg_seed() for more information. + */ +#define MBEDTLS_CTR_DRBG_ENTROPY_NONCE_LEN 0 +#else +/** The default length of the nonce read from the entropy source. + * + * This is half of the default entropy length because a single read from + * the entropy source does not provide enough material to form a nonce. + * See the documentation of mbedtls_ctr_drbg_seed() for more information. + */ +#define MBEDTLS_CTR_DRBG_ENTROPY_NONCE_LEN ( MBEDTLS_CTR_DRBG_ENTROPY_LEN + 1 ) / 2 +#endif + +/** + * \brief The CTR_DRBG context structure. + */ +typedef struct mbedtls_ctr_drbg_context +{ + unsigned char MBEDTLS_PRIVATE(counter)[16]; /*!< The counter (V). */ + int MBEDTLS_PRIVATE(reseed_counter); /*!< The reseed counter. + * This is the number of requests that have + * been made since the last (re)seeding, + * minus one. + * Before the initial seeding, this field + * contains the amount of entropy in bytes + * to use as a nonce for the initial seeding, + * or -1 if no nonce length has been explicitly + * set (see mbedtls_ctr_drbg_set_nonce_len()). + */ + int MBEDTLS_PRIVATE(prediction_resistance); /*!< This determines whether prediction + resistance is enabled, that is + whether to systematically reseed before + each random generation. */ + size_t MBEDTLS_PRIVATE(entropy_len); /*!< The amount of entropy grabbed on each + seed or reseed operation, in bytes. */ + int MBEDTLS_PRIVATE(reseed_interval); /*!< The reseed interval. + * This is the maximum number of requests + * that can be made between reseedings. */ + + mbedtls_aes_context MBEDTLS_PRIVATE(aes_ctx); /*!< The AES context. */ + + /* + * Callbacks (Entropy) + */ + int (*MBEDTLS_PRIVATE(f_entropy))(void *, unsigned char *, size_t); + /*!< The entropy callback function. */ + + void *MBEDTLS_PRIVATE(p_entropy); /*!< The context for the entropy function. */ + +#if defined(MBEDTLS_THREADING_C) + /* Invariant: the mutex is initialized if and only if f_entropy != NULL. + * This means that the mutex is initialized during the initial seeding + * in mbedtls_ctr_drbg_seed() and freed in mbedtls_ctr_drbg_free(). + * + * Note that this invariant may change without notice. Do not rely on it + * and do not access the mutex directly in application code. + */ + mbedtls_threading_mutex_t MBEDTLS_PRIVATE(mutex); +#endif +} +mbedtls_ctr_drbg_context; + +/** + * \brief This function initializes the CTR_DRBG context, + * and prepares it for mbedtls_ctr_drbg_seed() + * or mbedtls_ctr_drbg_free(). + * + * \note The reseed interval is + * #MBEDTLS_CTR_DRBG_RESEED_INTERVAL by default. + * You can override it by calling + * mbedtls_ctr_drbg_set_reseed_interval(). + * + * \param ctx The CTR_DRBG context to initialize. + */ +void mbedtls_ctr_drbg_init( mbedtls_ctr_drbg_context *ctx ); + +/** + * \brief This function seeds and sets up the CTR_DRBG + * 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). + * + * The entropy length is #MBEDTLS_CTR_DRBG_ENTROPY_LEN by default. + * You can override it by calling mbedtls_ctr_drbg_set_entropy_len(). + * + * The entropy nonce length is: + * - \c 0 if the entropy length is at least 3/2 times the entropy length, + * which guarantees that the security strength is the maximum permitted + * by the key size and entropy length according to NIST SP 800-90A §10.2.1; + * - Half the entropy length otherwise. + * You can override it by calling mbedtls_ctr_drbg_set_nonce_len(). + * With the default entropy length, the entropy nonce length is + * #MBEDTLS_CTR_DRBG_ENTROPY_NONCE_LEN. + * + * You can provide a nonce and personalization string in addition to the + * entropy source, to make this instantiation as unique as possible. + * See SP 800-90A §8.6.7 for more details about nonces. + * + * The _seed_material_ value passed to the derivation function in + * the CTR_DRBG Instantiate Process described in NIST SP 800-90A §10.2.1.3.2 + * is the concatenation of the following strings: + * - A string obtained by calling \p f_entropy function for the entropy + * length. + */ +#if MBEDTLS_CTR_DRBG_ENTROPY_NONCE_LEN == 0 +/** + * - If mbedtls_ctr_drbg_set_nonce_len() has been called, a string + * obtained by calling \p f_entropy function for the specified length. + */ +#else +/** + * - A string obtained by calling \p f_entropy function for the entropy nonce + * length. If the entropy nonce length is \c 0, this function does not + * make a second call to \p f_entropy. + */ +#endif +#if defined(MBEDTLS_THREADING_C) +/** + * \note When Mbed TLS is built with threading support, + * after this function returns successfully, + * it is safe to call mbedtls_ctr_drbg_random() + * from multiple threads. Other operations, including + * reseeding, are not thread-safe. + */ +#endif /* MBEDTLS_THREADING_C */ +/** + * - The \p custom string. + * + * \note To achieve the nominal security strength permitted + * by CTR_DRBG, the entropy length must be: + * - at least 16 bytes for a 128-bit strength + * (maximum achievable strength when using AES-128); + * - at least 32 bytes for a 256-bit strength + * (maximum achievable strength when using AES-256). + * + * In addition, if you do not pass a nonce in \p custom, + * the sum of the entropy length + * and the entropy nonce length must be: + * - at least 24 bytes for a 128-bit strength + * (maximum achievable strength when using AES-128); + * - at least 48 bytes for a 256-bit strength + * (maximum achievable strength when using AES-256). + * + * \param ctx The CTR_DRBG context to seed. + * It must have been initialized with + * mbedtls_ctr_drbg_init(). + * After a successful call to mbedtls_ctr_drbg_seed(), + * you may not call mbedtls_ctr_drbg_seed() again on + * the same context unless you call + * mbedtls_ctr_drbg_free() and mbedtls_ctr_drbg_init() + * again first. + * After a failed call to mbedtls_ctr_drbg_seed(), + * you must call mbedtls_ctr_drbg_free(). + * \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 buffer size + * 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_CTR_DRBG_MAX_SEED_INPUT + * - #MBEDTLS_CTR_DRBG_ENTROPY_LEN. + * + * \return \c 0 on success. + * \return #MBEDTLS_ERR_CTR_DRBG_ENTROPY_SOURCE_FAILED on failure. + */ +int mbedtls_ctr_drbg_seed( mbedtls_ctr_drbg_context *ctx, + int (*f_entropy)(void *, unsigned char *, size_t), + void *p_entropy, + const unsigned char *custom, + size_t len ); + +/** + * \brief This function resets CTR_DRBG context to the state immediately + * after initial call of mbedtls_ctr_drbg_init(). + * + * \param ctx The CTR_DRBG context to clear. + */ +void mbedtls_ctr_drbg_free( mbedtls_ctr_drbg_context *ctx ); + +/** + * \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_ctr_drbg_random_with_add() + * or mbedtls_ctr_drbg_random(). + * Only use this if your entropy source has sufficient + * throughput. + * + * \param ctx The CTR_DRBG context. + * \param resistance #MBEDTLS_CTR_DRBG_PR_ON or #MBEDTLS_CTR_DRBG_PR_OFF. + */ +void mbedtls_ctr_drbg_set_prediction_resistance( mbedtls_ctr_drbg_context *ctx, + int resistance ); + +/** + * \brief This function sets the amount of entropy grabbed on each + * seed or reseed. + * + * The default value is #MBEDTLS_CTR_DRBG_ENTROPY_LEN. + * + * \note The security strength of CTR_DRBG is bounded by the + * entropy length. Thus: + * - When using AES-256 + * (\c MBEDTLS_CTR_DRBG_USE_128_BIT_KEY is disabled, + * which is the default), + * \p len must be at least 32 (in bytes) + * to achieve a 256-bit strength. + * - When using AES-128 + * (\c MBEDTLS_CTR_DRBG_USE_128_BIT_KEY is enabled) + * \p len must be at least 16 (in bytes) + * to achieve a 128-bit strength. + * + * \param ctx The CTR_DRBG context. + * \param len The amount of entropy to grab, in bytes. + * This must be at most #MBEDTLS_CTR_DRBG_MAX_SEED_INPUT + * and at most the maximum length accepted by the + * entropy function that is set in the context. + */ +void mbedtls_ctr_drbg_set_entropy_len( mbedtls_ctr_drbg_context *ctx, + size_t len ); + +/** + * \brief This function sets the amount of entropy grabbed + * as a nonce for the initial seeding. + * + * Call this function before calling mbedtls_ctr_drbg_seed() to read + * a nonce from the entropy source during the initial seeding. + * + * \param ctx The CTR_DRBG context. + * \param len The amount of entropy to grab for the nonce, in bytes. + * This must be at most #MBEDTLS_CTR_DRBG_MAX_SEED_INPUT + * and at most the maximum length accepted by the + * entropy function that is set in the context. + * + * \return \c 0 on success. + * \return #MBEDTLS_ERR_CTR_DRBG_INPUT_TOO_BIG if \p len is + * more than #MBEDTLS_CTR_DRBG_MAX_SEED_INPUT. + * \return #MBEDTLS_ERR_CTR_DRBG_ENTROPY_SOURCE_FAILED + * if the initial seeding has already taken place. + */ +int mbedtls_ctr_drbg_set_nonce_len( mbedtls_ctr_drbg_context *ctx, + size_t len ); + +/** + * \brief This function sets the reseed interval. + * + * The reseed interval is the number of calls to mbedtls_ctr_drbg_random() + * or mbedtls_ctr_drbg_random_with_add() after which the entropy function + * is called again. + * + * The default value is #MBEDTLS_CTR_DRBG_RESEED_INTERVAL. + * + * \param ctx The CTR_DRBG context. + * \param interval The reseed interval. + */ +void mbedtls_ctr_drbg_set_reseed_interval( mbedtls_ctr_drbg_context *ctx, + int interval ); + +/** + * \brief This function reseeds the CTR_DRBG context, that is + * extracts data from the entropy source. + * + * \note This function is not thread-safe. It is not safe + * to call this function if another thread might be + * concurrently obtaining random numbers from the same + * context or updating or reseeding the same context. + * + * \param ctx The CTR_DRBG context. + * \param additional Additional data to add to the state. Can be \c NULL. + * \param len The length of the additional data. + * This must be less than + * #MBEDTLS_CTR_DRBG_MAX_SEED_INPUT - \c entropy_len + * where \c entropy_len is the entropy length + * configured for the context. + * + * \return \c 0 on success. + * \return #MBEDTLS_ERR_CTR_DRBG_ENTROPY_SOURCE_FAILED on failure. + */ +int mbedtls_ctr_drbg_reseed( mbedtls_ctr_drbg_context *ctx, + const unsigned char *additional, size_t len ); + +/** + * \brief This function updates the state of the CTR_DRBG context. + * + * \note This function is not thread-safe. It is not safe + * to call this function if another thread might be + * concurrently obtaining random numbers from the same + * context or updating or reseeding the same context. + * + * \param ctx The CTR_DRBG context. + * \param additional The data to update the state with. This must not be + * \c NULL unless \p add_len is \c 0. + * \param add_len Length of \p additional in bytes. This must be at + * most #MBEDTLS_CTR_DRBG_MAX_SEED_INPUT. + * + * \return \c 0 on success. + * \return #MBEDTLS_ERR_CTR_DRBG_INPUT_TOO_BIG if + * \p add_len is more than + * #MBEDTLS_CTR_DRBG_MAX_SEED_INPUT. + * \return An error from the underlying AES cipher on failure. + */ +int mbedtls_ctr_drbg_update( mbedtls_ctr_drbg_context *ctx, + const unsigned char *additional, + size_t add_len ); + +/** + * \brief This function updates a CTR_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. + * + * \note This function is not thread-safe. It is not safe + * to call this function if another thread might be + * concurrently obtaining random numbers from the same + * context or updating or reseeding the same context. + * + * \param p_rng The CTR_DRBG context. This must be a pointer to a + * #mbedtls_ctr_drbg_context structure. + * \param output The buffer to fill. + * \param output_len The length of the buffer in bytes. + * \param additional Additional data to update. Can be \c NULL, in which + * case the additional data is empty regardless of + * the value of \p add_len. + * \param add_len The length of the additional data + * if \p additional is not \c NULL. + * This must be less than #MBEDTLS_CTR_DRBG_MAX_INPUT + * and less than + * #MBEDTLS_CTR_DRBG_MAX_SEED_INPUT - \c entropy_len + * where \c entropy_len is the entropy length + * configured for the context. + * + * \return \c 0 on success. + * \return #MBEDTLS_ERR_CTR_DRBG_ENTROPY_SOURCE_FAILED or + * #MBEDTLS_ERR_CTR_DRBG_REQUEST_TOO_BIG on failure. + */ +int mbedtls_ctr_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 CTR_DRBG to generate random data. + * + * This function automatically reseeds if the reseed counter is exceeded + * or prediction resistance is enabled. + */ +#if defined(MBEDTLS_THREADING_C) +/** + * \note When Mbed TLS is built with threading support, + * it is safe to call mbedtls_ctr_drbg_random() + * from multiple threads. Other operations, including + * reseeding, are not thread-safe. + */ +#endif /* MBEDTLS_THREADING_C */ +/** + * \param p_rng The CTR_DRBG context. This must be a pointer to a + * #mbedtls_ctr_drbg_context structure. + * \param output The buffer to fill. + * \param output_len The length of the buffer in bytes. + * + * \return \c 0 on success. + * \return #MBEDTLS_ERR_CTR_DRBG_ENTROPY_SOURCE_FAILED or + * #MBEDTLS_ERR_CTR_DRBG_REQUEST_TOO_BIG on failure. + */ +int mbedtls_ctr_drbg_random( void *p_rng, + unsigned char *output, size_t output_len ); + +#if defined(MBEDTLS_FS_IO) +/** + * \brief This function writes a seed file. + * + * \param ctx The CTR_DRBG context. + * \param path The name of the file. + * + * \return \c 0 on success. + * \return #MBEDTLS_ERR_CTR_DRBG_FILE_IO_ERROR on file error. + * \return #MBEDTLS_ERR_CTR_DRBG_ENTROPY_SOURCE_FAILED on reseed + * failure. + */ +int mbedtls_ctr_drbg_write_seed_file( mbedtls_ctr_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 CTR_DRBG context. + * \param path The name of the file. + * + * \return \c 0 on success. + * \return #MBEDTLS_ERR_CTR_DRBG_FILE_IO_ERROR on file error. + * \return #MBEDTLS_ERR_CTR_DRBG_ENTROPY_SOURCE_FAILED on + * reseed failure. + * \return #MBEDTLS_ERR_CTR_DRBG_INPUT_TOO_BIG if the existing + * seed file is too large. + */ +int mbedtls_ctr_drbg_update_seed_file( mbedtls_ctr_drbg_context *ctx, const char *path ); +#endif /* MBEDTLS_FS_IO */ + +#if defined(MBEDTLS_SELF_TEST) + +/** + * \brief The CTR_DRBG checkup routine. + * + * \return \c 0 on success. + * \return \c 1 on failure. + */ +int mbedtls_ctr_drbg_self_test( int verbose ); + +#endif /* MBEDTLS_SELF_TEST */ + +#ifdef __cplusplus +} +#endif + +#endif /* ctr_drbg.h */ |