Diff: source/EntropySource/nRFEntropySource/nRFEntropySource.cpp

Revision:

0:1c7da5f83647

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/source/EntropySource/nRFEntropySource/nRFEntropySource.cpp	Tue Nov 29 06:29:10 2016 +0000
@@ -0,0 +1,67 @@
+/* mbed Microcontroller Library
+ * Copyright (c) 2006-2015 ARM Limited
+ *
+ * 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.
+ */
+#include "../EntropySource.h"
+
+#if defined(TARGET_NRF51822) || defined(TARGET_MCU_NRF52832) /* Persistent storage supported on nrf51 platforms */
+
+#include "nrf_soc.h"
+#include "nrf_error.h"
+#include "mbed.h"
+#include <mbedtls/entropy.h>
+
+/*
+ * nRF51 has a TRNG that we can access using SoftDevice.
+ */
+int eddystoneEntropyPoll(void *data, unsigned char *output, size_t len, size_t *olen)
+{
+    uint8_t bytes_available = 0;
+
+    // get the number of random bytes available
+    if (sd_rand_application_bytes_available_get(&bytes_available) != NRF_SUCCESS) {
+        return MBEDTLS_ERR_ENTROPY_SOURCE_FAILED;
+    }
+
+    // if there is more bytes available that what is requested,
+    // truncate the number of bytes in output to len, otherwise use the total
+    // of bytes available.
+    const uint8_t output_len = bytes_available > len ? len : bytes_available;
+
+    if (output_len) {
+        // transfer "output_len" random bytes to output.
+        if (sd_rand_application_vector_get(output, output_len) != NRF_SUCCESS) {
+            return MBEDTLS_ERR_ENTROPY_SOURCE_FAILED;
+        }
+    }
+
+    // Everything went fine, commit the output_len to the output parameter
+    *olen = output_len;
+    return 0;
+}
+
+int eddystoneRegisterEntropySource(	mbedtls_entropy_context* ctx) {
+    uint8_t pool_capacity;
+    sd_rand_application_pool_capacity_get(&pool_capacity);
+
+    return mbedtls_entropy_add_source(
+        ctx,
+        eddystoneEntropyPoll, // entropy source function
+        NULL,                 // entropy source data, NULL in this case
+        pool_capacity,        //  minimum number of bytes the entropy pool should wait on from this callback before releasing entropy
+        MBEDTLS_ENTROPY_SOURCE_STRONG
+    );
+}
+
+#endif /* #ifdef TARGET_NRF51822 */