1 /*
2 * Hardware entropy collector for the K64F, using Freescale's RNGA
3 *
4 * Copyright (C) 2006-2015, ARM Limited, All Rights Reserved
5 * SPDX-License-Identifier: Apache-2.0
6 *
7 * Licensed under the Apache License, Version 2.0 (the "License"); you may
8 * not use this file except in compliance with the License.
9 * You may obtain a copy of the License at
10 *
11 * http://www.apache.org/licenses/LICENSE-2.0
12 *
13 * Unless required by applicable law or agreed to in writing, software
14 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
15 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
16 * See the License for the specific language governing permissions and
17 * limitations under the License.
18 *
19 * This file is part of mbed TLS (https://tls.mbed.org)
20 */
21
22 /*
23 * WARNING: this is temporary!
24 * This should be in a separate yotta module which would be a target
25 * dependency of mbedtls (see IOTSSL-313)
26 */
27
28 #if defined(TARGET_LIKE_K64F)
29
30 /*
31 * Reference: "K64 Sub-Family Reference Manual, Rev. 2", chapter 34
32 */
33
34 #include "fsl_clock_manager.h"
35
36 /*
37 * Get one byte of entropy from the RNG, assuming it is up and running.
38 * As recommended (34.1.1), get only one bit of each output.
39 */
rng_get_byte(unsigned char * byte)40 static void rng_get_byte( unsigned char *byte )
41 {
42 size_t bit;
43
44 /* 34.5 Steps 3-4-5: poll SR and read from OR when ready */
45 for( bit = 0; bit < 8; bit++ )
46 {
47 while( ( RNG->SR & RNG_SR_OREG_LVL_MASK ) == 0 );
48 *byte |= ( RNG->OR & 1 ) << bit;
49 }
50 }
51
52 /*
53 * Get len bytes of entropy from the hardware RNG.
54 */
mbedtls_hardware_poll(void * data,unsigned char * output,size_t len,size_t * olen)55 int mbedtls_hardware_poll( void *data,
56 unsigned char *output, size_t len, size_t *olen )
57 {
58 size_t i;
59 int ret;
60 ((void) data);
61
62 CLOCK_SYS_EnableRngaClock( 0 );
63
64 /* Set "Interrupt Mask", "High Assurance" and "Go",
65 * unset "Clear interrupt" and "Sleep" */
66 RNG->CR = RNG_CR_INTM_MASK | RNG_CR_HA_MASK | RNG_CR_GO_MASK;
67
68 for( i = 0; i < len; i++ )
69 rng_get_byte( output + i );
70
71 /* Just be extra sure that we didn't do it wrong */
72 if( ( RNG->SR & RNG_SR_SECV_MASK ) != 0 )
73 {
74 ret = -1;
75 goto cleanup;
76 }
77
78 *olen = len;
79 ret = 0;
80
81 cleanup:
82 /* Disable clock to save power - assume we're the only users of RNG */
83 CLOCK_SYS_DisableRngaClock( 0 );
84
85 return( ret );
86 }
87
88 #endif
89
