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/** \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/mbedtls/psa_util.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/mbedtls/psa_util.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 <mbedtls/psa_util.h>
#if defined(MBEDTLS_PSA_CRYPTO_EXTERNAL_RNG)
#include <string.h>
#include <mbedtls/entropy.h> // only for error codes
#include <psa/crypto.h>
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_SHA512_C) && defined(MBEDTLS_SHA256_C)
#include <limits.h>
#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_SHA512_C)
#define MBEDTLS_PSA_HMAC_DRBG_MD_TYPE MBEDTLS_MD_SHA512
#elif defined(MBEDTLS_SHA256_C)
#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/mbedtls/psa_util.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/mbedtls/psa_util.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 */
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