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 
43 random_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 
48 random_device::~random_device() {}
49 
50 unsigned 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 
61 random_device::random_device(const string&) {}
62 
63 random_device::~random_device() {}
64 
65 unsigned random_device::operator()() { return arc4random(); }
66 
67 #elif defined(_LIBCPP_USING_DEV_RANDOM)
68 
69 random_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 
74 random_device::~random_device() { close(__f_); }
75 
76 unsigned 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(ENODATA, "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 
97 random_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 
105 random_device::~random_device() {}
106 
107 unsigned 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 
121 random_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 
126 random_device::~random_device() {}
127 
128 unsigned 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 
138 random_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 
143 random_device::~random_device() {}
144 
145 unsigned 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 
161 double 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