Diff: mbedtls/source/entropy_hardware_poll.c

Revision:

12:0071cb144c7a

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mbedtls/source/entropy_hardware_poll.c	Tue Nov 01 14:22:56 2016 +0000
@@ -0,0 +1,88 @@
+/*
+ *  Hardware entropy collector for the K64F, using Freescale's RNGA
+ *
+ *  Copyright (C) 2006-2015, 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)
+ */
+
+/*
+ * WARNING: this is temporary!
+ * This should be in a separate yotta module which would be a target
+ * dependency of mbedtls (see IOTSSL-313)
+ */
+
+#if defined(TARGET_LIKE_K64F)
+
+/*
+ * Reference: "K64 Sub-Family Reference Manual, Rev. 2", chapter 34
+ */
+
+#include "fsl_clock_manager.h"
+
+/*
+ * Get one byte of entropy from the RNG, assuming it is up and running.
+ * As recommended (34.1.1), get only one bit of each output.
+ */
+static void rng_get_byte( unsigned char *byte )
+{
+    size_t bit;
+
+    /* 34.5 Steps 3-4-5: poll SR and read from OR when ready */
+    for( bit = 0; bit < 8; bit++ )
+    {
+        while( ( RNG->SR & RNG_SR_OREG_LVL_MASK ) == 0 );
+        *byte |= ( RNG->OR & 1 ) << bit;
+    }
+}
+
+/*
+ * Get len bytes of entropy from the hardware RNG.
+ */
+int mbedtls_hardware_poll( void *data,
+                    unsigned char *output, size_t len, size_t *olen )
+{
+    size_t i;
+    int ret;
+    ((void) data);
+
+    CLOCK_SYS_EnableRngaClock( 0 );
+
+    /* Set "Interrupt Mask", "High Assurance" and "Go",
+     * unset "Clear interrupt" and "Sleep" */
+    RNG->CR = RNG_CR_INTM_MASK | RNG_CR_HA_MASK | RNG_CR_GO_MASK;
+
+    for( i = 0; i < len; i++ )
+        rng_get_byte( output + i );
+
+    /* Just be extra sure that we didn't do it wrong */
+    if( ( RNG->SR & RNG_SR_SECV_MASK ) != 0 )
+    {
+        ret = -1;
+        goto cleanup;
+    }
+
+    *olen = len;
+    ret = 0;
+
+cleanup:
+    /* Disable clock to save power - assume we're the only users of RNG */
+    CLOCK_SYS_DisableRngaClock( 0 );
+
+    return( ret );
+}
+
+#endif