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e3ed802138
Expose whatever RNG the PSA subsystem uses to applications using the mbedtls_xxx API. Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
219 lines
7.2 KiB
C
219 lines
7.2 KiB
C
/** \file psa_crypto_random_impl.h
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*
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* \brief PSA crypto random generator implementation abstraction.
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*
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* The definitions here need to be consistent with the declarations
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* in include/mbedtls/psa_util.h.
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*/
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/*
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* Copyright The Mbed TLS Contributors
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* SPDX-License-Identifier: Apache-2.0
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*
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* Licensed under the Apache License, Version 2.0 (the "License"); you may
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* not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#ifndef PSA_CRYPTO_RANDOM_IMPL_H
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#define PSA_CRYPTO_RANDOM_IMPL_H
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#if defined(MBEDTLS_PSA_CRYPTO_EXTERNAL_RNG)
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#include <string.h>
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#include <mbedtls/entropy.h> // only for error codes
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#include <psa/crypto.h>
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typedef mbedtls_psa_external_random_context_t mbedtls_psa_random_context_t;
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/* Trivial wrapper around psa_generate_random(). */
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int mbedtls_psa_get_random( void *p_rng,
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unsigned char *output,
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size_t output_size );
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/* The PSA RNG API doesn't need any externally maintained state. */
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#define MBEDTLS_PSA_RANDOM_STATE NULL
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#else /* MBEDTLS_PSA_CRYPTO_EXTERNAL_RNG */
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/* Choose a DRBG based on configuration and availability */
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#if defined(MBEDTLS_PSA_HMAC_DRBG_MD_TYPE)
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#include "mbedtls/hmac_drbg.h"
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#elif defined(MBEDTLS_CTR_DRBG_C)
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#include "mbedtls/ctr_drbg.h"
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#elif defined(MBEDTLS_HMAC_DRBG_C)
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#include "mbedtls/hmac_drbg.h"
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#if defined(MBEDTLS_SHA512_C) && defined(MBEDTLS_SHA256_C)
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#include <limits.h>
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#if SIZE_MAX > 0xffffffff
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/* Looks like a 64-bit system, so prefer SHA-512. */
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#define MBEDTLS_PSA_HMAC_DRBG_MD_TYPE MBEDTLS_MD_SHA512
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#else
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/* Looks like a 32-bit system, so prefer SHA-256. */
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#define MBEDTLS_PSA_HMAC_DRBG_MD_TYPE MBEDTLS_MD_SHA256
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#endif
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#elif defined(MBEDTLS_SHA512_C)
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#define MBEDTLS_PSA_HMAC_DRBG_MD_TYPE MBEDTLS_MD_SHA512
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#elif defined(MBEDTLS_SHA256_C)
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#define MBEDTLS_PSA_HMAC_DRBG_MD_TYPE MBEDTLS_MD_SHA256
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#else
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#error "No hash algorithm available for HMAC_DBRG."
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#endif
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#else
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#error "No DRBG module available for the psa_crypto module."
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#endif
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#include "mbedtls/entropy.h"
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/** The type of the PSA DRBG context.
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*/
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#if defined(MBEDTLS_CTR_DRBG_C)
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typedef mbedtls_ctr_drbg_context mbedtls_psa_drbg_context_t;
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#elif defined(MBEDTLS_HMAC_DRBG_C)
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typedef mbedtls_hmac_drbg_context mbedtls_psa_drbg_context_t;
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#endif
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/** Initialize the PSA DRBG.
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*
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* \param p_rng Pointer to the Mbed TLS DRBG state.
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*/
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static inline void mbedtls_psa_drbg_init( mbedtls_psa_drbg_context_t *p_rng )
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{
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#if defined(MBEDTLS_CTR_DRBG_C)
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mbedtls_ctr_drbg_init( p_rng );
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#elif defined(MBEDTLS_HMAC_DRBG_C)
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mbedtls_hmac_drbg_init( p_rng );
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#endif
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}
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/** Deinitialize the PSA DRBG.
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*
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* \param p_rng Pointer to the Mbed TLS DRBG state.
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*/
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static inline void mbedtls_psa_drbg_free( mbedtls_psa_drbg_context_t *p_rng )
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{
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#if defined(MBEDTLS_CTR_DRBG_C)
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mbedtls_ctr_drbg_free( p_rng );
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#elif defined(MBEDTLS_HMAC_DRBG_C)
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mbedtls_hmac_drbg_free( p_rng );
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#endif
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}
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/** The type of the PSA random generator context.
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*
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* The random generator context is composed of an entropy context and
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* a DRBG context.
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*/
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typedef struct
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{
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void (* entropy_init )( mbedtls_entropy_context *ctx );
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void (* entropy_free )( mbedtls_entropy_context *ctx );
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mbedtls_entropy_context entropy;
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mbedtls_psa_drbg_context_t drbg;
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} mbedtls_psa_random_context_t;
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/* The type of an Mbed TLS random generator function. This should be
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* part of the public API instead of repeating the type everywhere.
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* For the time being, declare it here. Declaring a type is necessary
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* to define mbedtls_psa_get_random as a variable of a function pointer
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* type without incurring the wrath of check-names.sh. */
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typedef int mbedtls_f_rng_t( void *p_rng, unsigned char *output, size_t output_size );
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/** Return random data.
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*
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* This function is suitable as the \p f_rng parameter to Mbed TLS functions
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* that require a random generator. Use #MBEDTLS_PSA_RANDOM_STATE to
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* obtain the \p p_rng parameter.
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*
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* \param p_rng The DRBG context. This must be
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* #MBEDTLS_PSA_RANDOM_STATE.
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* \param output The buffer to fill.
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* \param output_len The length of the buffer in bytes.
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* It must be at most #MBEDTLS_PSA_RANDOM_MAX_REQUEST.
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*
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* \retval \c 0 on success.
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* \return \c MBEDTLS_ERR_xxx_DRBG_xxx or
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* \c MBEDTLS_ERR_PLATFORM_xxx on failure.
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*/
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#if defined(MBEDTLS_CTR_DRBG_C)
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static mbedtls_f_rng_t *const mbedtls_psa_get_random = mbedtls_ctr_drbg_random;
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#elif defined(MBEDTLS_HMAC_DRBG_C)
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static mbedtls_f_rng_t *const mbedtls_psa_get_random = mbedtls_hmac_drbg_random;
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#endif
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/** The maximum number of bytes that mbedtls_psa_get_random() is expected to
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* return.
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*/
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#if defined(MBEDTLS_CTR_DRBG_C)
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#define MBEDTLS_PSA_RANDOM_MAX_REQUEST MBEDTLS_CTR_DRBG_MAX_REQUEST
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#elif defined(MBEDTLS_HMAC_DRBG_C)
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#define MBEDTLS_PSA_RANDOM_MAX_REQUEST MBEDTLS_HMAC_DRBG_MAX_REQUEST
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#endif
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/** A pointer to the PSA DRBG state.
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*
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* This variable is only intended to be used through the macro
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* #MBEDTLS_PSA_RANDOM_STATE.
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*/
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/* psa_crypto.c sets this variable to a pointer to the DRBG state in the
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* global PSA crypto state. */
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extern mbedtls_psa_drbg_context_t *const mbedtls_psa_random_state;
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/** A pointer to the PSA DRBG state.
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*
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* This macro expands to an expression that is suitable as the \c p_rng
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* parameter to pass to mbedtls_psa_get_random().
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*
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* This macro exists in all configurations where the psa_crypto module is
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* enabled. Its expansion depends on the configuration.
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*/
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#define MBEDTLS_PSA_RANDOM_STATE mbedtls_psa_random_state
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/** Seed the PSA DRBG.
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*
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* \param entropy An entropy context to read the seed from.
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* \param custom The personalization string.
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* This can be \c NULL, in which case the personalization
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* string is empty regardless of the value of \p len.
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* \param len The length of the personalization string.
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*
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* \return \c 0 on success.
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* \return An Mbed TLS error code (\c MBEDTLS_ERR_xxx) on failure.
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*/
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static inline int mbedtls_psa_drbg_seed(
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mbedtls_entropy_context *entropy,
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const unsigned char *custom, size_t len )
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{
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#if defined(MBEDTLS_CTR_DRBG_C)
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return( mbedtls_ctr_drbg_seed( MBEDTLS_PSA_RANDOM_STATE,
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mbedtls_entropy_func,
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entropy,
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custom, len ) );
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#elif defined(MBEDTLS_HMAC_DRBG_C)
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const mbedtls_md_info_t *md_info =
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mbedtls_md_info_from_type( MBEDTLS_PSA_HMAC_DRBG_MD_TYPE );
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return( mbedtls_hmac_drbg_seed( MBEDTLS_PSA_RANDOM_STATE,
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md_info,
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mbedtls_entropy_func,
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entropy,
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custom, len ) );
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#endif
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}
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#endif /* MBEDTLS_PSA_CRYPTO_EXTERNAL_RNG */
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#endif /* PSA_CRYPTO_RANDOM_IMPL_H */
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