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89 lines
2.3 KiB
C
89 lines
2.3 KiB
C
/*
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* Hardware entropy collector for the K64F, using Freescale's RNGA
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*
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* Copyright (C) 2006-2015, ARM Limited, All Rights Reserved
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* SPDX-License-Identifier: Apache-2.0
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*
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* Licensed under the Apache License, Version 2.0 (the "License"); you may
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* not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*
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* This file is part of mbed TLS (https://tls.mbed.org)
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*/
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/*
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* WARNING: this is temporary!
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* This should be in a separate yotta module which would be a target
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* dependency of mbedtls (see IOTSSL-313)
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*/
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#if defined(TARGET_LIKE_K64F)
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/*
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* Reference: "K64 Sub-Family Reference Manual, Rev. 2", chapter 34
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*/
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#include "fsl_clock_manager.h"
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/*
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* Get one byte of entropy from the RNG, assuming it is up and running.
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* As recommended (34.1.1), get only one bit of each output.
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*/
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static void rng_get_byte( unsigned char *byte )
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{
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size_t bit;
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/* 34.5 Steps 3-4-5: poll SR and read from OR when ready */
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for( bit = 0; bit < 8; bit++ )
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{
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while( ( RNG->SR & RNG_SR_OREG_LVL_MASK ) == 0 );
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*byte |= ( RNG->OR & 1 ) << bit;
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}
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}
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/*
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* Get len bytes of entropy from the hardware RNG.
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*/
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int mbedtls_hardware_poll( void *data,
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unsigned char *output, size_t len, size_t *olen )
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{
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size_t i;
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int ret;
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((void) data);
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CLOCK_SYS_EnableRngaClock( 0 );
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/* Set "Interrupt Mask", "High Assurance" and "Go",
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* unset "Clear interrupt" and "Sleep" */
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RNG->CR = RNG_CR_INTM_MASK | RNG_CR_HA_MASK | RNG_CR_GO_MASK;
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for( i = 0; i < len; i++ )
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rng_get_byte( output + i );
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/* Just be extra sure that we didn't do it wrong */
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if( ( RNG->SR & RNG_SR_SECV_MASK ) != 0 )
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{
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ret = -1;
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goto cleanup;
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}
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*olen = len;
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ret = 0;
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cleanup:
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/* Disable clock to save power - assume we're the only users of RNG */
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CLOCK_SYS_DisableRngaClock( 0 );
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return( ret );
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}
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#endif
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