libcoap  4.3.0
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 
12 #include "coap3/coap_internal.h"
13 
14 #ifdef HAVE_GETRANDOM
15 #include <sys/random.h>
16 #else /* !HAVE_GETRANDOM */
17 #include <stdlib.h>
18 #endif /* !HAVE_GETRANDOM */
19 
20 #if defined(_WIN32)
21 
22 errno_t __cdecl rand_s( _Out_ unsigned int* _RandomValue );
29 coap_prng_impl( unsigned char *buf, size_t len ) {
30  while ( len != 0 ) {
31  uint32_t r = 0;
32  size_t i;
33  if ( rand_s( &r ) != 0 )
34  return 0;
35  for ( i = 0; i < len && i < 4; i++ ) {
36  *buf++ = (uint8_t)r;
37  r >>= 8;
38  }
39  len -= i;
40  }
41  return 1;
42 }
43 
44 #endif /* _WIN32 */
45 
46 static int
47 coap_prng_default(void *buf, size_t len) {
48 #ifdef HAVE_GETRANDOM
49  return getrandom(buf, len, 0);
50 #else /* !HAVE_GETRANDOM */
51 #if defined(_WIN32)
52  return coap_prng_impl(buf,len);
53 #else /* !_WIN32 */
54  unsigned char *dst = (unsigned char *)buf;
55  while (len--)
56  *dst++ = rand() & 0xFF;
57  return 1;
58 #endif /* !_WIN32 */
59 #endif /* !HAVE_GETRANDOM */
60 }
61 
63 
64 #if defined(WITH_CONTIKI)
65 
66 #elif defined(WITH_LWIP) && defined(LWIP_RAND)
67 
68 #else
69 
70 void
72  rand_func = rng;
73 }
74 
75 void
76 coap_prng_init(unsigned int seed) {
77 #ifdef HAVE_GETRANDOM
78  /* No seed to seed the random source if getrandom() is used,
79  * see dtls_prng(). */
80  (void)seed;
81 #else /* !HAVE_GETRANDOM */
82  srand(seed);
83 #endif /* !HAVE_GETRANDOM */
84 }
85 
86 int
87 coap_prng(void *buf, size_t len) {
88  if (!rand_func) {
89  return 0;
90  }
91 
92  rand_func(buf, len);
93  return 1;
94 }
95 
96 #endif
Pulls together all the internal only header files.
static int coap_prng_default(void *buf, size_t len)
Definition: coap_prng.c:47
static coap_rand_func_t rand_func
Definition: coap_prng.c:62
int(* coap_rand_func_t)(void *out, size_t len)
Data type for random number generator function.
Definition: coap_prng.h:77
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:71
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:87
void coap_prng_init(unsigned int seed)
Seeds the default random number generation function with the given seed.
Definition: coap_prng.c:76
#define COAP_STATIC_INLINE
Definition: libcoap.h:40