Rename psa_crypto_random.h to psa_crypto_random_impl.h
Make it clear that this is an abstraction of the random generator
abstraction, and not an abstraction of the PSA random generator.
mbedtls_psa_get_random and MBEDTLS_PSA_RANDOM_STATE are public-facing
definitions and will be moved in a subsequent commit.
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
diff --git a/library/psa_crypto_random_impl.h b/library/psa_crypto_random_impl.h
new file mode 100644
index 0000000..6b445c6
--- /dev/null
+++ b/library/psa_crypto_random_impl.h
@@ -0,0 +1,208 @@
+/** \file psa_crypto_random_impl.h
+ *
+ * \brief PSA crypto random generator implementation abstraction.
+ */
+/*
+ * 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
+
+#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;
+
+int mbedtls_psa_get_random( void *p_rng,
+ unsigned char *output,
+ size_t output_size );
+
+#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"
+
+/** The type of the PSA DRBG context.
+ */
+#if defined(MBEDTLS_CTR_DRBG_C)
+typedef mbedtls_ctr_drbg_context mbedtls_psa_drbg_context_t;
+#elif defined(MBEDTLS_HMAC_DRBG_C)
+typedef mbedtls_hmac_drbg_context mbedtls_psa_drbg_context_t;
+#endif
+
+/** 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;
+
+/** Return random data.
+ *
+ * This function is suitable as the \p f_rng parameter to Mbed TLS functions
+ * that require a random generator. Use #MBEDTLS_PSA_RANDOM_STATE to
+ * obtain the \p p_rng parameter.
+ *
+ * \param p_rng The DRBG context. This must be
+ * #MBEDTLS_PSA_RANDOM_STATE.
+ * \param output The buffer to fill.
+ * \param output_len The length of the buffer in bytes.
+ * It must be at most #MBEDTLS_PSA_RANDOM_MAX_REQUEST.
+ *
+ * \retval \c 0 on success.
+ * \return \c MBEDTLS_ERR_xxx_DRBG_xxx or
+ * \c MBEDTLS_ERR_PLATFORM_xxx on failure.
+ */
+#if defined(MBEDTLS_CTR_DRBG_C)
+static int ( *const mbedtls_psa_get_random )(
+ void *p_rng, unsigned char *output, size_t output_size ) =
+ mbedtls_ctr_drbg_random;
+#elif defined(MBEDTLS_HMAC_DRBG_C)
+static int ( *const mbedtls_psa_get_random )(
+ void *p_rng, unsigned char *output, size_t output_size ) =
+ mbedtls_hmac_drbg_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.
+ */
+extern mbedtls_psa_drbg_context_t *const mbedtls_psa_random_state;
+
+/** A pointer to the PSA DRBG state.
+ *
+ * This macro expnds 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 */