1 /*
2 * random_seed.c
3 *
4 * Copyright (c) 2013 Metaparadigm Pte. Ltd.
5 * Michael Clark <michael@metaparadigm.com>
6 *
7 * This library is free software; you can redistribute it and/or modify
8 * it under the terms of the MIT license. See COPYING for details.
9 *
10 */
11
12 #include <stdio.h>
13 #include "config.h"
14
15 #define DEBUG_SEED(s)
16
17
18 #if defined ENABLE_RDRAND
19
20 /* cpuid */
21
22 #if defined __GNUC__ && (defined __i386__ || defined __x86_64__)
23 #define HAS_X86_CPUID 1
24
do_cpuid(int regs[],int h)25 static void do_cpuid(int regs[], int h)
26 {
27 __asm__ __volatile__(
28 #if defined __x86_64__
29 "pushq %%rbx;\n"
30 #else
31 "pushl %%ebx;\n"
32 #endif
33 "cpuid;\n"
34 #if defined __x86_64__
35 "popq %%rbx;\n"
36 #else
37 "popl %%ebx;\n"
38 #endif
39 : "=a"(regs[0]), [ebx] "=r"(regs[1]), "=c"(regs[2]), "=d"(regs[3])
40 : "a"(h));
41 }
42
43 #elif defined _MSC_VER
44
45 #define HAS_X86_CPUID 1
46 #define do_cpuid __cpuid
47
48 #endif
49
50 /* has_rdrand */
51
52 #if HAS_X86_CPUID
53
has_rdrand()54 static int has_rdrand()
55 {
56 // CPUID.01H:ECX.RDRAND[bit 30] == 1
57 int regs[4];
58 do_cpuid(regs, 1);
59 return (regs[2] & (1 << 30)) != 0;
60 }
61
62 #endif
63
64 /* get_rdrand_seed - GCC x86 and X64 */
65
66 #if defined __GNUC__ && (defined __i386__ || defined __x86_64__)
67
68 #define HAVE_RDRAND 1
69
get_rdrand_seed()70 static int get_rdrand_seed()
71 {
72 DEBUG_SEED("get_rdrand_seed");
73 int _eax;
74 // rdrand eax
75 __asm__ __volatile__("1: .byte 0x0F\n"
76 " .byte 0xC7\n"
77 " .byte 0xF0\n"
78 " jnc 1b;\n"
79 : "=a" (_eax));
80 return _eax;
81 }
82
83 #endif
84
85 #if defined _MSC_VER
86
87 #if _MSC_VER >= 1700
88 #define HAVE_RDRAND 1
89
90 /* get_rdrand_seed - Visual Studio 2012 and above */
91
get_rdrand_seed()92 static int get_rdrand_seed()
93 {
94 DEBUG_SEED("get_rdrand_seed");
95 int r;
96 while (_rdrand32_step(&r) == 0);
97 return r;
98 }
99
100 #elif defined _M_IX86
101 #define HAVE_RDRAND 1
102
103 /* get_rdrand_seed - Visual Studio 2010 and below - x86 only */
104
get_rdrand_seed()105 static int get_rdrand_seed()
106 {
107 DEBUG_SEED("get_rdrand_seed");
108 int _eax;
109 retry:
110 // rdrand eax
111 __asm _emit 0x0F __asm _emit 0xC7 __asm _emit 0xF0
112 __asm jnc retry
113 __asm mov _eax, eax
114 return _eax;
115 }
116
117 #endif
118 #endif
119
120 #endif /* defined ENABLE_RDRAND */
121
122
123 /* has_dev_urandom */
124
125 #if defined (__APPLE__) || defined(__unix__) || defined(__linux__)
126
127 #include <string.h>
128 #include <fcntl.h>
129 #include <unistd.h>
130 #include <errno.h>
131 #include <stdlib.h>
132 #include <sys/stat.h>
133
134 #define HAVE_DEV_RANDOM 1
135
136 static const char *dev_random_file = "/dev/urandom";
137
has_dev_urandom()138 static int has_dev_urandom()
139 {
140 struct stat buf;
141 if (stat(dev_random_file, &buf)) {
142 return 0;
143 }
144 return ((buf.st_mode & S_IFCHR) != 0);
145 }
146
147
148 /* get_dev_random_seed */
149
get_dev_random_seed()150 static int get_dev_random_seed()
151 {
152 DEBUG_SEED("get_dev_random_seed");
153
154 int fd = open(dev_random_file, O_RDONLY);
155 if (fd < 0) {
156 fprintf(stderr, "error opening %s: %s", dev_random_file, strerror(errno));
157 exit(1);
158 }
159
160 int r;
161 ssize_t nread = read(fd, &r, sizeof(r));
162 if (nread != sizeof(r)) {
163 fprintf(stderr, "error short read %s: %s", dev_random_file, strerror(errno));
164 exit(1);
165 }
166
167 close(fd);
168 return r;
169 }
170
171 #endif
172
173
174 /* get_cryptgenrandom_seed */
175
176 #ifdef WIN32
177
178 #define HAVE_CRYPTGENRANDOM 1
179
180 #include <windows.h>
181 #include <wincrypt.h>
182 #ifndef __GNUC__
183 #pragma comment(lib, "advapi32.lib")
184 #endif
185
get_cryptgenrandom_seed()186 static int get_cryptgenrandom_seed()
187 {
188 DEBUG_SEED("get_cryptgenrandom_seed");
189
190 HCRYPTPROV hProvider = 0;
191 int r;
192
193 if (!CryptAcquireContextW(&hProvider, 0, 0, PROV_RSA_FULL, CRYPT_VERIFYCONTEXT | CRYPT_SILENT)) {
194 fprintf(stderr, "error CryptAcquireContextW");
195 exit(1);
196 }
197
198 if (!CryptGenRandom(hProvider, sizeof(r), (BYTE*)&r)) {
199 fprintf(stderr, "error CryptGenRandom");
200 exit(1);
201 }
202
203 CryptReleaseContext(hProvider, 0);
204
205 return r;
206 }
207
208 #endif
209
210
211 /* get_time_seed */
212
213 #include <time.h>
214
get_time_seed()215 static int get_time_seed()
216 {
217 DEBUG_SEED("get_time_seed");
218
219 return (int)time(NULL) * 433494437;
220 }
221
222
223 /* json_c_get_random_seed */
224
json_c_get_random_seed()225 int json_c_get_random_seed()
226 {
227 #if HAVE_RDRAND
228 if (has_rdrand()) return get_rdrand_seed();
229 #endif
230 #if HAVE_DEV_RANDOM
231 if (has_dev_urandom()) return get_dev_random_seed();
232 #endif
233 #if HAVE_CRYPTGENRANDOM
234 return get_cryptgenrandom_seed();
235 #endif
236 return get_time_seed();
237 }
238