1 /*
2 * Copyright (c) 2019, NXP
3 *
4 * SPDX-License-Identifier: Apache-2.0
5 */
6
7 #include <zephyr/init.h>
8 #include <zephyr/device.h>
9 #include <zephyr/drivers/entropy.h>
10 #include <zephyr/kernel.h>
11 #include <string.h>
12
13 #if !defined(CONFIG_MBEDTLS_CFG_FILE)
14 #include "mbedtls/config.h"
15 #else
16 #include CONFIG_MBEDTLS_CFG_FILE
17 #endif /* CONFIG_MBEDTLS_CFG_FILE */
18 #include <mbedtls/ctr_drbg.h>
19
20 /*
21 * entropy_dev is initialized at runtime to allow first time initialization
22 * of the ctr_drbg engine.
23 */
24 static const struct device *entropy_dev;
25 static const unsigned char drbg_seed[] = CONFIG_CS_CTR_DRBG_PERSONALIZATION;
26 static bool ctr_initialised;
27 static struct k_mutex ctr_lock;
28
29 static mbedtls_ctr_drbg_context ctr_ctx;
30
ctr_drbg_entropy_func(void * ctx,unsigned char * buf,size_t len)31 static int ctr_drbg_entropy_func(void *ctx, unsigned char *buf, size_t len)
32 {
33 return entropy_get_entropy(entropy_dev, (void *)buf, len);
34 }
35
ctr_drbg_initialize(void)36 static int ctr_drbg_initialize(void)
37 {
38 int ret;
39
40 entropy_dev = DEVICE_DT_GET(DT_CHOSEN(zephyr_entropy));
41
42 if (!device_is_ready(entropy_dev)) {
43 __ASSERT(0, "Entropy device %s not ready", entropy_dev->name);
44 return -ENODEV;
45 }
46
47 mbedtls_ctr_drbg_init(&ctr_ctx);
48
49 ret = mbedtls_ctr_drbg_seed(&ctr_ctx,
50 ctr_drbg_entropy_func,
51 NULL,
52 drbg_seed,
53 sizeof(drbg_seed));
54
55 if (ret != 0) {
56 mbedtls_ctr_drbg_free(&ctr_ctx);
57 return -EIO;
58 }
59
60 ctr_initialised = true;
61 return 0;
62 }
63
64
z_impl_sys_csrand_get(void * dst,uint32_t outlen)65 int z_impl_sys_csrand_get(void *dst, uint32_t outlen)
66 {
67 int ret;
68
69 k_mutex_lock(&ctr_lock, K_FOREVER);
70
71 if (unlikely(!ctr_initialised)) {
72 ret = ctr_drbg_initialize();
73 if (ret != 0) {
74 ret = -EIO;
75 goto end;
76 }
77 }
78
79 ret = mbedtls_ctr_drbg_random(&ctr_ctx, (unsigned char *)dst, outlen);
80
81 end:
82 k_mutex_unlock(&ctr_lock);
83
84 return ret;
85 }
86
