xref: /freebsd/contrib/llvm-project/libcxx/src/random.cpp (revision 924226fba12cc9a228c73b956e1b7fa24c60b055)
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 "limits"
17 #include "random"
18 #include "system_error"
19 
20 #if defined(__sun__)
21 #   define rename solaris_headers_are_broken
22 #endif // defined(__sun__)
23 
24 #include <errno.h>
25 #include <stdio.h>
26 #include <stdlib.h>
27 
28 #if defined(_LIBCPP_USING_GETENTROPY)
29 #   include <sys/random.h>
30 #elif defined(_LIBCPP_USING_DEV_RANDOM)
31 #   include <fcntl.h>
32 #   include <unistd.h>
33 #   if __has_include(<sys/ioctl.h>) && __has_include(<linux/random.h>)
34 #       include <sys/ioctl.h>
35 #       include <linux/random.h>
36 #   endif
37 #elif defined(_LIBCPP_USING_NACL_RANDOM)
38 #   include <nacl/nacl_random.h>
39 #elif defined(_LIBCPP_USING_FUCHSIA_CPRNG)
40 #  include <zircon/syscalls.h>
41 #endif
42 
43 
44 _LIBCPP_BEGIN_NAMESPACE_STD
45 
46 #if defined(_LIBCPP_USING_GETENTROPY)
47 
48 random_device::random_device(const string& __token)
49 {
50     if (__token != "/dev/urandom")
51         __throw_system_error(ENOENT, ("random device not supported " + __token).c_str());
52 }
53 
54 random_device::~random_device()
55 {
56 }
57 
58 unsigned
59 random_device::operator()()
60 {
61     unsigned r;
62     size_t n = sizeof(r);
63     int err = getentropy(&r, n);
64     if (err)
65         __throw_system_error(errno, "random_device getentropy failed");
66     return r;
67 }
68 
69 #elif defined(_LIBCPP_USING_ARC4_RANDOM)
70 
71 random_device::random_device(const string&)
72 {
73 }
74 
75 random_device::~random_device()
76 {
77 }
78 
79 unsigned
80 random_device::operator()()
81 {
82     return arc4random();
83 }
84 
85 #elif defined(_LIBCPP_USING_DEV_RANDOM)
86 
87 random_device::random_device(const string& __token)
88     : __f_(open(__token.c_str(), O_RDONLY))
89 {
90     if (__f_ < 0)
91         __throw_system_error(errno, ("random_device failed to open " + __token).c_str());
92 }
93 
94 random_device::~random_device()
95 {
96     close(__f_);
97 }
98 
99 unsigned
100 random_device::operator()()
101 {
102     unsigned r;
103     size_t n = sizeof(r);
104     char* p = reinterpret_cast<char*>(&r);
105     while (n > 0)
106     {
107         ssize_t s = read(__f_, p, n);
108         if (s == 0)
109             __throw_system_error(ENODATA, "random_device got EOF");
110         if (s == -1)
111         {
112             if (errno != EINTR)
113                 __throw_system_error(errno, "random_device got an unexpected error");
114             continue;
115         }
116         n -= static_cast<size_t>(s);
117         p += static_cast<size_t>(s);
118     }
119     return r;
120 }
121 
122 #elif defined(_LIBCPP_USING_NACL_RANDOM)
123 
124 random_device::random_device(const string& __token)
125 {
126     if (__token != "/dev/urandom")
127         __throw_system_error(ENOENT, ("random device not supported " + __token).c_str());
128     int error = nacl_secure_random_init();
129     if (error)
130         __throw_system_error(error, ("random device failed to open " + __token).c_str());
131 }
132 
133 random_device::~random_device()
134 {
135 }
136 
137 unsigned
138 random_device::operator()()
139 {
140     unsigned r;
141     size_t n = sizeof(r);
142     size_t bytes_written;
143     int error = nacl_secure_random(&r, n, &bytes_written);
144     if (error != 0)
145         __throw_system_error(error, "random_device failed getting bytes");
146     else if (bytes_written != n)
147         __throw_runtime_error("random_device failed to obtain enough bytes");
148     return r;
149 }
150 
151 #elif defined(_LIBCPP_USING_WIN32_RANDOM)
152 
153 random_device::random_device(const string& __token)
154 {
155     if (__token != "/dev/urandom")
156         __throw_system_error(ENOENT, ("random device not supported " + __token).c_str());
157 }
158 
159 random_device::~random_device()
160 {
161 }
162 
163 unsigned
164 random_device::operator()()
165 {
166     unsigned r;
167     errno_t err = rand_s(&r);
168     if (err)
169         __throw_system_error(err, "random_device rand_s failed.");
170     return r;
171 }
172 
173 #elif defined(_LIBCPP_USING_FUCHSIA_CPRNG)
174 
175 random_device::random_device(const string& __token) {
176   if (__token != "/dev/urandom")
177     __throw_system_error(ENOENT, ("random device not supported " + __token).c_str());
178 }
179 
180 random_device::~random_device() {}
181 
182 unsigned random_device::operator()() {
183   // Implicitly link against the vDSO system call ABI without
184   // requiring the final link to specify -lzircon explicitly when
185   // statically linking libc++.
186 #  pragma comment(lib, "zircon")
187 
188   // The system call cannot fail.  It returns only when the bits are ready.
189   unsigned r;
190   _zx_cprng_draw(&r, sizeof(r));
191   return r;
192 }
193 
194 #else
195 #error "Random device not implemented for this architecture"
196 #endif
197 
198 double
199 random_device::entropy() const noexcept
200 {
201 #if defined(_LIBCPP_USING_DEV_RANDOM) && defined(RNDGETENTCNT)
202   int ent;
203   if (::ioctl(__f_, RNDGETENTCNT, &ent) < 0)
204     return 0;
205 
206   if (ent < 0)
207     return 0;
208 
209   if (ent > std::numeric_limits<result_type>::digits)
210     return std::numeric_limits<result_type>::digits;
211 
212   return ent;
213 #elif defined(_LIBCPP_USING_ARC4_RANDOM) || defined(_LIBCPP_USING_FUCHSIA_CPRNG)
214   return std::numeric_limits<result_type>::digits;
215 #else
216   return 0;
217 #endif
218 }
219 
220 _LIBCPP_END_NAMESPACE_STD
221