1//===----------------------------------------------------------------------===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8
9#include <__config>
10
11#if defined(_LIBCPP_USING_WIN32_RANDOM)
12// Must be defined before including stdlib.h to enable rand_s().
13# define _CRT_RAND_S
14#endif // defined(_LIBCPP_USING_WIN32_RANDOM)
15
16#include <__system_error/throw_system_error.h>
17#include <limits>
18#include <random>
19#include <string>
20
21#include <errno.h>
22#include <stdio.h>
23#include <stdlib.h>
24
25#if defined(_LIBCPP_USING_GETENTROPY)
26# include <sys/random.h>
27#elif defined(_LIBCPP_USING_DEV_RANDOM)
28# include <fcntl.h>
29# include <unistd.h>
30# if __has_include(<sys/ioctl.h>) && __has_include(<linux/random.h>)
31# include <linux/random.h>
32# include <sys/ioctl.h>
33# endif
34#elif defined(_LIBCPP_USING_FUCHSIA_CPRNG)
35# include <zircon/syscalls.h>
36#endif
37
38_LIBCPP_BEGIN_NAMESPACE_STD
39_LIBCPP_BEGIN_EXPLICIT_ABI_ANNOTATIONS
40
41#if defined(_LIBCPP_USING_GETENTROPY)
42
43random_device::random_device(const string& __token) {
44 if (__token != "/dev/urandom")
45 std::__throw_system_error(ENOENT, ("random device not supported " + __token).c_str());
46}
47
48random_device::~random_device() {}
49
50unsigned random_device::operator()() {
51 unsigned r;
52 size_t n = sizeof(r);
53 int err = getentropy(&r, n);
54 if (err)
55 std::__throw_system_error(errno, "random_device getentropy failed");
56 return r;
57}
58
59#elif defined(_LIBCPP_USING_ARC4_RANDOM)
60
61random_device::random_device(const string&) {}
62
63random_device::~random_device() {}
64
65unsigned random_device::operator()() { return arc4random(); }
66
67#elif defined(_LIBCPP_USING_DEV_RANDOM)
68
69random_device::random_device(const string& __token) : __f_(open(file: __token.c_str(), O_RDONLY)) {
70 if (__f_ < 0)
71 std::__throw_system_error(errno, what_arg: ("random_device failed to open " + __token).c_str());
72}
73
74random_device::~random_device() { close(fd: __f_); }
75
76unsigned random_device::operator()() {
77 unsigned r;
78 size_t n = sizeof(r);
79 char* p = reinterpret_cast<char*>(&r);
80 while (n > 0) {
81 ssize_t s = read(fd: __f_, buf: p, nbytes: n);
82 if (s == 0)
83 std::__throw_system_error(ENOMSG, what_arg: "random_device got EOF");
84 if (s == -1) {
85 if (errno != EINTR)
86 std::__throw_system_error(errno, what_arg: "random_device got an unexpected error");
87 continue;
88 }
89 n -= static_cast<size_t>(s);
90 p += static_cast<size_t>(s);
91 }
92 return r;
93}
94
95#elif defined(_LIBCPP_USING_WIN32_RANDOM)
96
97random_device::random_device(const string& __token) {
98 if (__token != "/dev/urandom")
99 std::__throw_system_error(ENOENT, ("random device not supported " + __token).c_str());
100}
101
102random_device::~random_device() {}
103
104unsigned random_device::operator()() {
105 unsigned r;
106 errno_t err = rand_s(&r);
107 if (err)
108 std::__throw_system_error(err, "random_device rand_s failed.");
109 return r;
110}
111
112#elif defined(_LIBCPP_USING_FUCHSIA_CPRNG)
113
114random_device::random_device(const string& __token) {
115 if (__token != "/dev/urandom")
116 std::__throw_system_error(ENOENT, ("random device not supported " + __token).c_str());
117}
118
119random_device::~random_device() {}
120
121unsigned random_device::operator()() {
122 // Implicitly link against the vDSO system call ABI without
123 // requiring the final link to specify -lzircon explicitly when
124 // statically linking libc++.
125# pragma comment(lib, "zircon")
126
127 // The system call cannot fail. It returns only when the bits are ready.
128 unsigned r;
129 _zx_cprng_draw(&r, sizeof(r));
130 return r;
131}
132
133#else
134# error "Random device not implemented for this architecture"
135#endif
136
137double random_device::entropy() const noexcept {
138#if defined(_LIBCPP_USING_DEV_RANDOM) && defined(RNDGETENTCNT)
139 int ent;
140 if (::ioctl(fd: __f_, RNDGETENTCNT, &ent) < 0)
141 return 0;
142
143 if (ent < 0)
144 return 0;
145
146 if (ent > std::numeric_limits<result_type>::digits)
147 return std::numeric_limits<result_type>::digits;
148
149 return ent;
150#elif defined(_LIBCPP_USING_ARC4_RANDOM) || defined(_LIBCPP_USING_FUCHSIA_CPRNG)
151 return std::numeric_limits<result_type>::digits;
152#else
153 return 0;
154#endif
155}
156
157_LIBCPP_END_EXPLICIT_ABI_ANNOTATIONS
158_LIBCPP_END_NAMESPACE_STD
159