SHA-256 Hash example on mbed OS

Diff: main.cpp

Revision:

0:faef56ba465f

Child:

45:9152ca3b575e

diff -r 000000000000 -r faef56ba465f main.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/main.cpp	Wed Jul 27 14:30:35 2016 +0100
@@ -0,0 +1,159 @@
+/*
+ *  Hello world example of using the hashing functions of mbed TLS
+ *
+ *  Copyright (C) 2016, 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 program illustrates various ways of hashing a buffer.
+ * You normally need only one of these two includes.
+ */
+#include "mbed.h"
+#include "mbedtls/sha256.h" /* SHA-256 only */
+#include "mbedtls/md.h"     /* generic interface */
+
+#if DEBUG_LEVEL > 0
+#include "mbedtls/debug.h"
+#endif
+
+#include "mbedtls/platform.h"
+
+#include <string.h>
+
+static void print_hex(const char *title, const unsigned char buf[], size_t len)
+{
+    mbedtls_printf("%s: ", title);
+
+    for (size_t i = 0; i < len; i++)
+        mbedtls_printf("%02x", buf[i]);
+
+    mbedtls_printf("\r\n");
+}
+
+static const char hello_str[] = "Hello, world!";
+static const unsigned char *hello_buffer = (const unsigned char *) hello_str;
+static const size_t hello_len = strlen(hello_str);
+
+static int example(void)
+{
+    mbedtls_printf("\r\n\r\n");
+
+    /*
+     * Method 1: use all-in-one function of a specific SHA-xxx module
+     */
+    unsigned char output1[32]; /* SHA-256 outputs 32 bytes */
+
+    /* 0 here means use the full SHA-256, not the SHA-224 variant */
+    mbedtls_sha256(hello_buffer, hello_len, output1, 0);
+
+    print_hex("Method 1", output1, sizeof output1);
+
+
+    /*
+     * Method 2: use the streaming interface of a specific SHA-xxx module
+     * This is useful if we get our input piecewise.
+     */
+    unsigned char output2[32];
+    mbedtls_sha256_context ctx2;
+
+    mbedtls_sha256_init(&ctx2);
+    mbedtls_sha256_starts(&ctx2, 0); /* SHA-256, not 224 */
+
+    /* Simulating multiple fragments */
+    mbedtls_sha256_update(&ctx2, hello_buffer, 1);
+    mbedtls_sha256_update(&ctx2, hello_buffer + 1, 1);
+    mbedtls_sha256_update(&ctx2, hello_buffer + 2, hello_len - 2);
+
+    mbedtls_sha256_finish(&ctx2, output2);
+    print_hex("Method 2", output2, sizeof output2);
+
+    /* Or you could re-use the context by doing mbedtls_sha256_starts() again */
+    mbedtls_sha256_free(&ctx2);
+
+    /*
+     * Method 3: use all-in-one function of the generice interface
+     */
+    unsigned char output3[MBEDTLS_MD_MAX_SIZE]; /* Enough for any hash */
+
+    /* Can easily pick any hash you want, by identifier */
+    const mbedtls_md_info_t *md_info3 = mbedtls_md_info_from_type(MBEDTLS_MD_SHA256);
+
+    if (md_info3 == NULL)
+    {
+        mbedtls_printf("SHA256 not available\r\n");
+        return 1;
+    }
+
+    int ret3 = mbedtls_md(md_info3, hello_buffer, hello_len, output3);
+
+    if (ret3 != 0)
+    {
+        mbedtls_printf("md() returned -0x%04X\r\n", -ret3);
+        return 1;
+    }
+
+    print_hex("Method 3", output3, mbedtls_md_get_size(md_info3));
+
+
+    /*
+     * Method 4: streaming & generic interface
+     */
+    unsigned char output4[MBEDTLS_MD_MAX_SIZE]; /* Enough for any hash */
+
+    const mbedtls_md_info_t *md_info4 = mbedtls_md_info_from_type(MBEDTLS_MD_SHA256);
+
+    if (md_info4 == NULL)
+    {
+        mbedtls_printf("SHA256 not available\r\n");
+        return 1;
+    }
+
+    mbedtls_md_context_t ctx4;
+
+    mbedtls_md_init(&ctx4);
+
+    int ret4 = mbedtls_md_init_ctx(&ctx4, md_info4);
+    if (ret4 != 0)
+    {
+        mbedtls_printf("md_init_ctx() returned -0x%04X\r\n", -ret4);
+        return 1;
+    }
+
+    mbedtls_md_starts(&ctx4);
+
+    /* Simulating multiple fragments */
+    mbedtls_md_update(&ctx4, hello_buffer, 1);
+    mbedtls_md_update(&ctx4, hello_buffer + 1, 1);
+    mbedtls_md_update(&ctx4, hello_buffer + 2, hello_len - 2);
+
+    mbedtls_md_finish(&ctx4, output4);
+    print_hex("Method 4", output4, mbedtls_md_get_size(md_info4));
+
+    /* Or you could re-use the context by doing mbedtls_md_starts() again */
+    mbedtls_md_free(&ctx4);
+
+
+    mbedtls_printf("\r\nDONE\r\n");
+
+    return 0;
+}
+
+int main() {
+    int ret = example();
+    if (ret != 0) {
+        mbedtls_printf("Example failed with error %d\r\n", ret);
+    }
+}