New header crypto_sizes.h

This header will contain macros that calculate buffer sizes, whose
semantics are standardized but whose definitions are
implementation-specific because they depend on the available algorithms
and on some permitted buffer size tolerances.

Move size macros from crypto_struct.h to crypto_sizes.h, because these
definitions need to be available both in the frontend and in the
backend, whereas structures have different contents.

include/psa/crypto.h

@@ -2070,6 +2070,10 @@ psa_status_t psa_generate_key(psa_key_slot_t key,
 }
 #endif
 
+/* The file "crypto_sizes.h" contains definitions for size calculation
+ * macros whose definitions are implementation-specific. */
+#include "crypto_sizes.h"
+
 /* The file "crypto_struct.h" contains definitions for
  * implementation-specific structs that are declared above. */
 #include "crypto_struct.h"

include/psa/crypto_sizes.h

@@ -0,0 +1,50 @@
+/**
+ * \file psa/crypto_sizes.h
+ *
+ * \brief PSA cryptography module: Mbed TLS buffer size macros
+ *
+ * This file contains the definitions of macros that are useful to
+ * compute buffer sizes. The signatures and semantics of these macros
+ * are standardized, but the definitions are not, because they depend on
+ * the available algorithms and, in some cases, on permitted tolerances
+ * on buffer sizes.
+ */
+/*
+ *  Copyright (C) 2018, ARM Limited, All Rights Reserved
+ *  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.
+ *
+ *  This file is part of mbed TLS (https://tls.mbed.org)
+ */
+
+#ifndef PSA_CRYPTO_SIZES_H
+#define PSA_CRYPTO_SIZES_H
+
+/* Include the Mbed TLS configuration file, the way Mbed TLS does it
+ * in each of its header files. */
+#if !defined(MBEDTLS_CONFIG_FILE)
+#include "../mbedtls/config.h"
+#else
+#include MBEDTLS_CONFIG_FILE
+#endif
+
+#if defined(MBEDTLS_SHA512_C)
+#define PSA_HASH_MAX_SIZE 64
+#define PSA_HMAC_MAX_HASH_BLOCK_SIZE 128
+#else
+#define PSA_HASH_MAX_SIZE 32
+#define PSA_HMAC_MAX_HASH_BLOCK_SIZE 64
+#endif
+
+#endif /* PSA_CRYPTO_SIZES_H */

include/psa/crypto_struct.h

@@ -45,14 +45,6 @@
 #include "mbedtls/sha256.h"
 #include "mbedtls/sha512.h"
 
-#if defined(MBEDTLS_SHA512_C)
-#define PSA_HASH_MAX_SIZE 64
-#define PSA_HMAC_MAX_HASH_BLOCK_SIZE 128
-#else
-#define PSA_HASH_MAX_SIZE 32
-#define PSA_HMAC_MAX_HASH_BLOCK_SIZE 64
-#endif
-
 struct psa_hash_operation_s
 {
     psa_algorithm_t alg;