libcoap  4.3.1
coap_prng.c
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1 /*
2  * coap_prng.c -- random number generation
3  *
4  * Copyright (C) 2020 Olaf Bergmann <bergmann@tzi.org>
5  *
6  * SPDX-License-Identifier: BSD-2-Clause
7  *
8  * This file is part of the CoAP library libcoap. Please see README
9  * for terms of use.
10  */
11 
17 #include "coap3/coap_internal.h"
18 
19 #ifdef HAVE_GETRANDOM
20 #include <sys/random.h>
21 #else /* !HAVE_GETRANDOM */
22 #include <stdlib.h>
23 #endif /* !HAVE_GETRANDOM */
24 
25 #if defined(MBEDTLS_ENTROPY_HARDWARE_ALT)
26 #include <entropy_poll.h>
27 #endif /* MBEDTLS_ENTROPY_HARDWARE_ALT */
28 
29 #if defined(_WIN32)
30 
31 errno_t __cdecl rand_s( _Out_ unsigned int* _RandomValue );
38 coap_prng_impl( unsigned char *buf, size_t len ) {
39  while ( len != 0 ) {
40  uint32_t r = 0;
41  size_t i;
42  if ( rand_s( &r ) != 0 )
43  return 0;
44  for ( i = 0; i < len && i < 4; i++ ) {
45  *buf++ = (uint8_t)r;
46  r >>= 8;
47  }
48  len -= i;
49  }
50  return 1;
51 }
52 
53 #endif /* _WIN32 */
54 
55 /*
56  * This, or any user provided alternative, function is expected to
57  * return 0 on failure and 1 on success.
58  */
59 static int
60 coap_prng_default(void *buf, size_t len) {
61 #if defined(MBEDTLS_ENTROPY_HARDWARE_ALT)
62  /* mbedtls_hardware_poll() returns 0 on success */
63  return (mbedtls_hardware_poll(NULL, buf, len, NULL) ? 0 : 1);
64 #else /* !MBEDTLS_ENTROPY_HARDWARE_ALT */
65 #ifdef HAVE_GETRANDOM
66  return (getrandom(buf, len, 0) > 0) ? 1 : 0;
67 #else /* !HAVE_GETRANDOM */
68 #if defined(_WIN32)
69  return coap_prng_impl(buf,len);
70 #else /* !_WIN32 */
71  unsigned char *dst = (unsigned char *)buf;
72  while (len--)
73  *dst++ = rand() & 0xFF;
74  return 1;
75 #endif /* !_WIN32 */
76 #endif /* !HAVE_GETRANDOM */
77 #endif /* !MBEDTLS_ENTROPY_HARDWARE_ALT */
78 }
79 
81 
82 #if defined(WITH_CONTIKI)
83 
84 #elif defined(WITH_LWIP) && defined(LWIP_RAND)
85 
86 #else
87 
88 void
90  rand_func = rng;
91 }
92 
93 void
94 coap_prng_init(unsigned int seed) {
95 #ifdef HAVE_GETRANDOM
96  /* No seed to seed the random source if getrandom() is used,
97  * see dtls_prng(). */
98  (void)seed;
99 #else /* !HAVE_GETRANDOM */
100  srand(seed);
101 #endif /* !HAVE_GETRANDOM */
102 }
103 
104 int
105 coap_prng(void *buf, size_t len) {
106  if (!rand_func) {
107  return 0;
108  }
109 
110  return rand_func(buf, len);
111 }
112 
113 #endif
Pulls together all the internal only header files.
static int coap_prng_default(void *buf, size_t len)
Definition: coap_prng.c:60
static coap_rand_func_t rand_func
Definition: coap_prng.c:80
int(* coap_rand_func_t)(void *out, size_t len)
Data type for random number generator function.
Definition: coap_prng.h:78
void coap_set_prng(coap_rand_func_t rng)
Replaces the current random number generation function with the default function rng.
Definition: coap_prng.c:89
int coap_prng(void *buf, size_t len)
Fills buf with len random bytes using the default pseudo random number generator.
Definition: coap_prng.c:105
void coap_prng_init(unsigned int seed)
Seeds the default random number generation function with the given seed.
Definition: coap_prng.c:94
#define COAP_STATIC_INLINE
Definition: libcoap.h:45