Bitcoin Core  24.99.0
P2P Digital Currency
random.h
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1 /*************************************************************************
2  * Copyright (c) 2020-2021 Elichai Turkel *
3  * Distributed under the CC0 software license, see the accompanying file *
4  * EXAMPLES_COPYING or https://creativecommons.org/publicdomain/zero/1.0 *
5  *************************************************************************/
6 
7 /*
8  * This file is an attempt at collecting best practice methods for obtaining randomness with different operating systems.
9  * It may be out-of-date. Consult the documentation of the operating system before considering to use the methods below.
10  *
11  * Platform randomness sources:
12  * Linux -> `getrandom(2)`(`sys/random.h`), if not available `/dev/urandom` should be used. http://man7.org/linux/man-pages/man2/getrandom.2.html, https://linux.die.net/man/4/urandom
13  * macOS -> `getentropy(2)`(`sys/random.h`), if not available `/dev/urandom` should be used. https://www.unix.com/man-page/mojave/2/getentropy, https://opensource.apple.com/source/xnu/xnu-517.12.7/bsd/man/man4/random.4.auto.html
14  * FreeBSD -> `getrandom(2)`(`sys/random.h`), if not available `kern.arandom` should be used. https://www.freebsd.org/cgi/man.cgi?query=getrandom, https://www.freebsd.org/cgi/man.cgi?query=random&sektion=4
15  * OpenBSD -> `getentropy(2)`(`unistd.h`), if not available `/dev/urandom` should be used. https://man.openbsd.org/getentropy, https://man.openbsd.org/urandom
16  * Windows -> `BCryptGenRandom`(`bcrypt.h`). https://docs.microsoft.com/en-us/windows/win32/api/bcrypt/nf-bcrypt-bcryptgenrandom
17  */
18 
19 #if defined(_WIN32)
20 #include <windows.h>
21 #include <ntstatus.h>
22 #include <bcrypt.h>
23 #elif defined(__linux__) || defined(__APPLE__) || defined(__FreeBSD__)
24 #include <sys/random.h>
25 #elif defined(__OpenBSD__)
26 #include <unistd.h>
27 #else
28 #error "Couldn't identify the OS"
29 #endif
30 
31 #include <stddef.h>
32 #include <limits.h>
33 #include <stdio.h>
34 
35 
36 /* Returns 1 on success, and 0 on failure. */
37 static int fill_random(unsigned char* data, size_t size) {
38 #if defined(_WIN32)
39  NTSTATUS res = BCryptGenRandom(NULL, data, size, BCRYPT_USE_SYSTEM_PREFERRED_RNG);
40  if (res != STATUS_SUCCESS || size > ULONG_MAX) {
41  return 0;
42  } else {
43  return 1;
44  }
45 #elif defined(__linux__) || defined(__FreeBSD__)
46  /* If `getrandom(2)` is not available you should fallback to /dev/urandom */
47  ssize_t res = getrandom(data, size, 0);
48  if (res < 0 || (size_t)res != size ) {
49  return 0;
50  } else {
51  return 1;
52  }
53 #elif defined(__APPLE__) || defined(__OpenBSD__)
54  /* If `getentropy(2)` is not available you should fallback to either
55  * `SecRandomCopyBytes` or /dev/urandom */
56  int res = getentropy(data, size);
57  if (res == 0) {
58  return 1;
59  } else {
60  return 0;
61  }
62 #endif
63  return 0;
64 }
65 
66 static void print_hex(unsigned char* data, size_t size) {
67  size_t i;
68  printf("0x");
69  for (i = 0; i < size; i++) {
70  printf("%02x", data[i]);
71  }
72  printf("\n");
73 }
void printf(const char *fmt, const Args &... args)
Format list of arguments to std::cout, according to the given format string.
Definition: tinyformat.h:1079
static int fill_random(unsigned char *data, size_t size)
Definition: random.h:37
static void print_hex(unsigned char *data, size_t size)
Definition: random.h:66