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
40#if defined(_LIBCPP_USING_GETENTROPY)
41
42random_device::random_device(const string& __token) {
43 if (__token != "/dev/urandom")
44 std::__throw_system_error(ENOENT, ("random device not supported " + __token).c_str());
45}
46
47random_device::~random_device() {}
48
49unsigned random_device::operator()() {
50 unsigned r;
51 size_t n = sizeof(r);
52 int err = getentropy(&r, n);
53 if (err)
54 std::__throw_system_error(errno, "random_device getentropy failed");
55 return r;
56}
57
58#elif defined(_LIBCPP_USING_ARC4_RANDOM)
59
60random_device::random_device(const string&) {}
61
62random_device::~random_device() {}
63
64unsigned random_device::operator()() { return arc4random(); }
65
66#elif defined(_LIBCPP_USING_DEV_RANDOM)
67
68random_device::random_device(const string& __token) : __f_(open(file: __token.c_str(), O_RDONLY)) {
69 if (__f_ < 0)
70 std::__throw_system_error(errno, what_arg: ("random_device failed to open " + __token).c_str());
71}
72
73random_device::~random_device() { close(fd: __f_); }
74
75unsigned random_device::operator()() {
76 unsigned r;
77 size_t n = sizeof(r);
78 char* p = reinterpret_cast<char*>(&r);
79 while (n > 0) {
80 ssize_t s = read(fd: __f_, buf: p, nbytes: n);
81 if (s == 0)
82 std::__throw_system_error(ENOMSG, what_arg: "random_device got EOF");
83 if (s == -1) {
84 if (errno != EINTR)
85 std::__throw_system_error(errno, what_arg: "random_device got an unexpected error");
86 continue;
87 }
88 n -= static_cast<size_t>(s);
89 p += static_cast<size_t>(s);
90 }
91 return r;
92}
93
94#elif defined(_LIBCPP_USING_WIN32_RANDOM)
95
96random_device::random_device(const string& __token) {
97 if (__token != "/dev/urandom")
98 std::__throw_system_error(ENOENT, ("random device not supported " + __token).c_str());
99}
100
101random_device::~random_device() {}
102
103unsigned random_device::operator()() {
104 unsigned r;
105 errno_t err = rand_s(&r);
106 if (err)
107 std::__throw_system_error(err, "random_device rand_s failed.");
108 return r;
109}
110
111#elif defined(_LIBCPP_USING_FUCHSIA_CPRNG)
112
113random_device::random_device(const string& __token) {
114 if (__token != "/dev/urandom")
115 std::__throw_system_error(ENOENT, ("random device not supported " + __token).c_str());
116}
117
118random_device::~random_device() {}
119
120unsigned random_device::operator()() {
121 // Implicitly link against the vDSO system call ABI without
122 // requiring the final link to specify -lzircon explicitly when
123 // statically linking libc++.
124# pragma comment(lib, "zircon")
125
126 // The system call cannot fail. It returns only when the bits are ready.
127 unsigned r;
128 _zx_cprng_draw(&r, sizeof(r));
129 return r;
130}
131
132#else
133# error "Random device not implemented for this architecture"
134#endif
135
136double random_device::entropy() const noexcept {
137#if defined(_LIBCPP_USING_DEV_RANDOM) && defined(RNDGETENTCNT)
138 int ent;
139 if (::ioctl(fd: __f_, RNDGETENTCNT, &ent) < 0)
140 return 0;
141
142 if (ent < 0)
143 return 0;
144
145 if (ent > std::numeric_limits<result_type>::digits)
146 return std::numeric_limits<result_type>::digits;
147
148 return ent;
149#elif defined(_LIBCPP_USING_ARC4_RANDOM) || defined(_LIBCPP_USING_FUCHSIA_CPRNG)
150 return std::numeric_limits<result_type>::digits;
151#else
152 return 0;
153#endif
154}
155
156_LIBCPP_END_NAMESPACE_STD
157