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_NACL_RANDOM)
35# include <nacl/nacl_random.h>
36#elif defined(_LIBCPP_USING_FUCHSIA_CPRNG)
37# include <zircon/syscalls.h>
38#endif
39
40_LIBCPP_BEGIN_NAMESPACE_STD
41
42#if defined(_LIBCPP_USING_GETENTROPY)
43
44random_device::random_device(const string& __token) {
45 if (__token != "/dev/urandom")
46 std::__throw_system_error(ENOENT, ("random device not supported " + __token).c_str());
47}
48
49random_device::~random_device() {}
50
51unsigned random_device::operator()() {
52 unsigned r;
53 size_t n = sizeof(r);
54 int err = getentropy(&r, n);
55 if (err)
56 std::__throw_system_error(errno, "random_device getentropy failed");
57 return r;
58}
59
60#elif defined(_LIBCPP_USING_ARC4_RANDOM)
61
62random_device::random_device(const string&) {}
63
64random_device::~random_device() {}
65
66unsigned random_device::operator()() { return arc4random(); }
67
68#elif defined(_LIBCPP_USING_DEV_RANDOM)
69
70random_device::random_device(const string& __token) : __f_(open(file: __token.c_str(), O_RDONLY)) {
71 if (__f_ < 0)
72 std::__throw_system_error(errno, what_arg: ("random_device failed to open " + __token).c_str());
73}
74
75random_device::~random_device() { close(fd: __f_); }
76
77unsigned random_device::operator()() {
78 unsigned r;
79 size_t n = sizeof(r);
80 char* p = reinterpret_cast<char*>(&r);
81 while (n > 0) {
82 ssize_t s = read(fd: __f_, buf: p, nbytes: n);
83 if (s == 0)
84 std::__throw_system_error(ENOMSG, what_arg: "random_device got EOF");
85 if (s == -1) {
86 if (errno != EINTR)
87 std::__throw_system_error(errno, what_arg: "random_device got an unexpected error");
88 continue;
89 }
90 n -= static_cast<size_t>(s);
91 p += static_cast<size_t>(s);
92 }
93 return r;
94}
95
96#elif defined(_LIBCPP_USING_NACL_RANDOM)
97
98random_device::random_device(const string& __token) {
99 if (__token != "/dev/urandom")
100 std::__throw_system_error(ENOENT, ("random device not supported " + __token).c_str());
101 int error = nacl_secure_random_init();
102 if (error)
103 std::__throw_system_error(error, ("random device failed to open " + __token).c_str());
104}
105
106random_device::~random_device() {}
107
108unsigned random_device::operator()() {
109 unsigned r;
110 size_t n = sizeof(r);
111 size_t bytes_written;
112 int error = nacl_secure_random(&r, n, &bytes_written);
113 if (error != 0)
114 std::__throw_system_error(error, "random_device failed getting bytes");
115 else if (bytes_written != n)
116 std::__throw_runtime_error("random_device failed to obtain enough bytes");
117 return r;
118}
119
120#elif defined(_LIBCPP_USING_WIN32_RANDOM)
121
122random_device::random_device(const string& __token) {
123 if (__token != "/dev/urandom")
124 std::__throw_system_error(ENOENT, ("random device not supported " + __token).c_str());
125}
126
127random_device::~random_device() {}
128
129unsigned random_device::operator()() {
130 unsigned r;
131 errno_t err = rand_s(&r);
132 if (err)
133 std::__throw_system_error(err, "random_device rand_s failed.");
134 return r;
135}
136
137#elif defined(_LIBCPP_USING_FUCHSIA_CPRNG)
138
139random_device::random_device(const string& __token) {
140 if (__token != "/dev/urandom")
141 std::__throw_system_error(ENOENT, ("random device not supported " + __token).c_str());
142}
143
144random_device::~random_device() {}
145
146unsigned random_device::operator()() {
147 // Implicitly link against the vDSO system call ABI without
148 // requiring the final link to specify -lzircon explicitly when
149 // statically linking libc++.
150# pragma comment(lib, "zircon")
151
152 // The system call cannot fail. It returns only when the bits are ready.
153 unsigned r;
154 _zx_cprng_draw(&r, sizeof(r));
155 return r;
156}
157
158#else
159# error "Random device not implemented for this architecture"
160#endif
161
162double random_device::entropy() const noexcept {
163#if defined(_LIBCPP_USING_DEV_RANDOM) && defined(RNDGETENTCNT)
164 int ent;
165 if (::ioctl(fd: __f_, RNDGETENTCNT, &ent) < 0)
166 return 0;
167
168 if (ent < 0)
169 return 0;
170
171 if (ent > std::numeric_limits<result_type>::digits)
172 return std::numeric_limits<result_type>::digits;
173
174 return ent;
175#elif defined(_LIBCPP_USING_ARC4_RANDOM) || defined(_LIBCPP_USING_FUCHSIA_CPRNG)
176 return std::numeric_limits<result_type>::digits;
177#else
178 return 0;
179#endif
180}
181
182_LIBCPP_END_NAMESPACE_STD
183