/** \file psa_crypto_random_impl.h * * \brief PSA crypto random generator implementation abstraction. * * The definitions here need to be consistent with the declarations * in include/psa_util_internal.h. This file contains some redundant * declarations to increase the chance that a compiler will detect * inconsistencies if one file is changed without updating the other, * but not all potential inconsistencies can be enforced, so make sure * to check the public declarations and contracts in * include/psa_util_internal.h if you modify this file. */ /* * 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 PSA_CRYPTO_RANDOM_IMPL_H #define PSA_CRYPTO_RANDOM_IMPL_H #include "psa_util_internal.h" #if defined(MBEDTLS_PSA_CRYPTO_EXTERNAL_RNG) #include #include // only for error codes #include typedef mbedtls_psa_external_random_context_t mbedtls_psa_random_context_t; /* Trivial wrapper around psa_generate_random(). */ int mbedtls_psa_get_random(void *p_rng, unsigned char *output, size_t output_size); /* The PSA RNG API doesn't need any externally maintained state. */ #define MBEDTLS_PSA_RANDOM_STATE NULL #else /* MBEDTLS_PSA_CRYPTO_EXTERNAL_RNG */ /* Choose a DRBG based on configuration and availability */ #if defined(MBEDTLS_PSA_HMAC_DRBG_MD_TYPE) #include "mbedtls/hmac_drbg.h" #elif defined(MBEDTLS_CTR_DRBG_C) #include "mbedtls/ctr_drbg.h" #elif defined(MBEDTLS_HMAC_DRBG_C) #include "mbedtls/hmac_drbg.h" #if defined(MBEDTLS_MD_CAN_SHA512) && defined(MBEDTLS_MD_CAN_SHA256) #include #if SIZE_MAX > 0xffffffff /* Looks like a 64-bit system, so prefer SHA-512. */ #define MBEDTLS_PSA_HMAC_DRBG_MD_TYPE MBEDTLS_MD_SHA512 #else /* Looks like a 32-bit system, so prefer SHA-256. */ #define MBEDTLS_PSA_HMAC_DRBG_MD_TYPE MBEDTLS_MD_SHA256 #endif #elif defined(MBEDTLS_MD_CAN_SHA512) #define MBEDTLS_PSA_HMAC_DRBG_MD_TYPE MBEDTLS_MD_SHA512 #elif defined(MBEDTLS_MD_CAN_SHA256) #define MBEDTLS_PSA_HMAC_DRBG_MD_TYPE MBEDTLS_MD_SHA256 #else #error "No hash algorithm available for HMAC_DBRG." #endif #else #error "No DRBG module available for the psa_crypto module." #endif #include "mbedtls/entropy.h" /** Initialize the PSA DRBG. * * \param p_rng Pointer to the Mbed TLS DRBG state. */ static inline void mbedtls_psa_drbg_init(mbedtls_psa_drbg_context_t *p_rng) { #if defined(MBEDTLS_CTR_DRBG_C) mbedtls_ctr_drbg_init(p_rng); #elif defined(MBEDTLS_HMAC_DRBG_C) mbedtls_hmac_drbg_init(p_rng); #endif } /** Deinitialize the PSA DRBG. * * \param p_rng Pointer to the Mbed TLS DRBG state. */ static inline void mbedtls_psa_drbg_free(mbedtls_psa_drbg_context_t *p_rng) { #if defined(MBEDTLS_CTR_DRBG_C) mbedtls_ctr_drbg_free(p_rng); #elif defined(MBEDTLS_HMAC_DRBG_C) mbedtls_hmac_drbg_free(p_rng); #endif } /** The type of the PSA random generator context. * * The random generator context is composed of an entropy context and * a DRBG context. */ typedef struct { void (* entropy_init)(mbedtls_entropy_context *ctx); void (* entropy_free)(mbedtls_entropy_context *ctx); mbedtls_entropy_context entropy; mbedtls_psa_drbg_context_t drbg; } mbedtls_psa_random_context_t; /* Defined in include/psa_util_internal.h so that it's visible to * application code. The declaration here is redundant, but included * as a safety net to make it more likely that a future change that * accidentally causes the implementation to diverge from the interface * will be noticed. */ /* Do not include the declaration under MSVC because it doesn't accept it * ("error C2370: 'mbedtls_psa_get_random' : redefinition; different storage class"). * Observed with Visual Studio 2013. A known bug apparently: * https://stackoverflow.com/questions/8146541/duplicate-external-static-declarations-not-allowed-in-visual-studio */ #if !defined(_MSC_VER) static mbedtls_f_rng_t *const mbedtls_psa_get_random; #endif /** The maximum number of bytes that mbedtls_psa_get_random() is expected to * return. */ #if defined(MBEDTLS_CTR_DRBG_C) #define MBEDTLS_PSA_RANDOM_MAX_REQUEST MBEDTLS_CTR_DRBG_MAX_REQUEST #elif defined(MBEDTLS_HMAC_DRBG_C) #define MBEDTLS_PSA_RANDOM_MAX_REQUEST MBEDTLS_HMAC_DRBG_MAX_REQUEST #endif /** A pointer to the PSA DRBG state. * * This variable is only intended to be used through the macro * #MBEDTLS_PSA_RANDOM_STATE. */ /* psa_crypto.c sets this variable to a pointer to the DRBG state in the * global PSA crypto state. */ /* The type `mbedtls_psa_drbg_context_t` is defined in * include/psa_util_internal.h so that `mbedtls_psa_random_state` can be * declared there and be visible to application code. */ extern mbedtls_psa_drbg_context_t *const mbedtls_psa_random_state; /** A pointer to the PSA DRBG state. * * This macro expands to an expression that is suitable as the \c p_rng * parameter to pass to mbedtls_psa_get_random(). * * This macro exists in all configurations where the psa_crypto module is * enabled. Its expansion depends on the configuration. */ #define MBEDTLS_PSA_RANDOM_STATE mbedtls_psa_random_state /** Seed the PSA DRBG. * * \param entropy An entropy context to read the seed from. * \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. * * \return \c 0 on success. * \return An Mbed TLS error code (\c MBEDTLS_ERR_xxx) on failure. */ static inline int mbedtls_psa_drbg_seed( mbedtls_entropy_context *entropy, const unsigned char *custom, size_t len) { #if defined(MBEDTLS_CTR_DRBG_C) return mbedtls_ctr_drbg_seed(MBEDTLS_PSA_RANDOM_STATE, mbedtls_entropy_func, entropy, custom, len); #elif defined(MBEDTLS_HMAC_DRBG_C) const mbedtls_md_info_t *md_info = mbedtls_md_info_from_type(MBEDTLS_PSA_HMAC_DRBG_MD_TYPE); return mbedtls_hmac_drbg_seed(MBEDTLS_PSA_RANDOM_STATE, md_info, mbedtls_entropy_func, entropy, custom, len); #endif } #endif /* MBEDTLS_PSA_CRYPTO_EXTERNAL_RNG */ #endif /* PSA_CRYPTO_RANDOM_IMPL_H */