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/system_error.h>
17#include <limits>
18#include <random>
19
20#include <errno.h>
21#include <stdio.h>
22#include <stdlib.h>
23
24#if defined(_LIBCPP_USING_GETENTROPY)
25# include <sys/random.h>
26#elif defined(_LIBCPP_USING_DEV_RANDOM)
27# include <fcntl.h>
28# include <unistd.h>
29# if __has_include(<sys/ioctl.h>) && __has_include(<linux/random.h>)
30# include <linux/random.h>
31# include <sys/ioctl.h>
32# endif
33#elif defined(_LIBCPP_USING_NACL_RANDOM)
34# include <nacl/nacl_random.h>
35#elif defined(_LIBCPP_USING_FUCHSIA_CPRNG)
36# include <zircon/syscalls.h>
37#endif
38
39_LIBCPP_BEGIN_NAMESPACE_STD
40
41#if defined(_LIBCPP_USING_GETENTROPY)
42
43random_device::random_device(const string& __token) {
44 if (__token != "/dev/urandom")
45 __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 __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(__token.c_str(), O_RDONLY)) {
70 if (__f_ < 0)
71 __throw_system_error(errno, ("random_device failed to open " + __token).c_str());
72}
73
74random_device::~random_device() { close(__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(__f_, p, n);
82 if (s == 0)
83 __throw_system_error(ENOMSG, "random_device got EOF");
84 if (s == -1) {
85 if (errno != EINTR)
86 __throw_system_error(errno, "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_NACL_RANDOM)
96
97random_device::random_device(const string& __token) {
98 if (__token != "/dev/urandom")
99 __throw_system_error(ENOENT, ("random device not supported " + __token).c_str());
100 int error = nacl_secure_random_init();
101 if (error)
102 __throw_system_error(error, ("random device failed to open " + __token).c_str());
103}
104
105random_device::~random_device() {}
106
107unsigned random_device::operator()() {
108 unsigned r;
109 size_t n = sizeof(r);
110 size_t bytes_written;
111 int error = nacl_secure_random(&r, n, &bytes_written);
112 if (error != 0)
113 __throw_system_error(error, "random_device failed getting bytes");
114 else if (bytes_written != n)
115 __throw_runtime_error("random_device failed to obtain enough bytes");
116 return r;
117}
118
119#elif defined(_LIBCPP_USING_WIN32_RANDOM)
120
121random_device::random_device(const string& __token) {
122 if (__token != "/dev/urandom")
123 __throw_system_error(ENOENT, ("random device not supported " + __token).c_str());
124}
125
126random_device::~random_device() {}
127
128unsigned random_device::operator()() {
129 unsigned r;
130 errno_t err = rand_s(&r);
131 if (err)
132 __throw_system_error(err, "random_device rand_s failed.");
133 return r;
134}
135
136#elif defined(_LIBCPP_USING_FUCHSIA_CPRNG)
137
138random_device::random_device(const string& __token) {
139 if (__token != "/dev/urandom")
140 __throw_system_error(ENOENT, ("random device not supported " + __token).c_str());
141}
142
143random_device::~random_device() {}
144
145unsigned random_device::operator()() {
146 // Implicitly link against the vDSO system call ABI without
147 // requiring the final link to specify -lzircon explicitly when
148 // statically linking libc++.
149# pragma comment(lib, "zircon")
150
151 // The system call cannot fail. It returns only when the bits are ready.
152 unsigned r;
153 _zx_cprng_draw(&r, sizeof(r));
154 return r;
155}
156
157#else
158# error "Random device not implemented for this architecture"
159#endif
160
161double random_device::entropy() const noexcept {
162#if defined(_LIBCPP_USING_DEV_RANDOM) && defined(RNDGETENTCNT)
163 int ent;
164 if (::ioctl(__f_, RNDGETENTCNT, &ent) < 0)
165 return 0;
166
167 if (ent < 0)
168 return 0;
169
170 if (ent > std::numeric_limits<result_type>::digits)
171 return std::numeric_limits<result_type>::digits;
172
173 return ent;
174#elif defined(_LIBCPP_USING_ARC4_RANDOM) || defined(_LIBCPP_USING_FUCHSIA_CPRNG)
175 return std::numeric_limits<result_type>::digits;
176#else
177 return 0;
178#endif
179}
180
181_LIBCPP_END_NAMESPACE_STD
182