192 lines
6.4 KiB
C
192 lines
6.4 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/psa_util_internal.h. This file contains some redundant
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* declarations to increase the chance that a compiler will detect
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* inconsistencies if one file is changed without updating the other,
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* but not all potential inconsistencies can be enforced, so make sure
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* to check the public declarations and contracts in
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* include/psa_util_internal.h if you modify this file.
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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 OR GPL-2.0-or-later
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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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#include "psa_util_internal.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_MD_CAN_SHA512) && defined(MBEDTLS_MD_CAN_SHA256)
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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_MD_CAN_SHA512)
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#define MBEDTLS_PSA_HMAC_DRBG_MD_TYPE MBEDTLS_MD_SHA512
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#elif defined(MBEDTLS_MD_CAN_SHA256)
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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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/** 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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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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/* Defined in include/psa_util_internal.h so that it's visible to
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* application code. The declaration here is redundant, but included
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* as a safety net to make it more likely that a future change that
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* accidentally causes the implementation to diverge from the interface
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* will be noticed. */
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/* Do not include the declaration under MSVC because it doesn't accept it
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* ("error C2370: 'mbedtls_psa_get_random' : redefinition; different storage class").
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* Observed with Visual Studio 2013. A known bug apparently:
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* https://stackoverflow.com/questions/8146541/duplicate-external-static-declarations-not-allowed-in-visual-studio
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*/
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#if !defined(_MSC_VER)
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static mbedtls_f_rng_t *const mbedtls_psa_get_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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/* The type `mbedtls_psa_drbg_context_t` is defined in
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* include/psa_util_internal.h so that `mbedtls_psa_random_state` can be
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* declared there and be visible to application code. */
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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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