Michael Clark | 64e3690 | 2014-04-09 13:48:21 +0800 | [diff] [blame] | 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 | |
| 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 | |
| 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 | |
| 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 | |
| 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 | |
| 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 | |
| 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 | |
| 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)) { |
Alexandru Costache | 4841c48 | 2014-07-04 11:58:14 +0300 | [diff] [blame] | 163 | fprintf(stderr, "error short read %s: %s", dev_random_file, strerror(errno)); |
Michael Clark | 64e3690 | 2014-04-09 13:48:21 +0800 | [diff] [blame] | 164 | exit(1); |
| 165 | } |
Alexandru Costache | 4841c48 | 2014-07-04 11:58:14 +0300 | [diff] [blame] | 166 | |
Michael Clark | 64e3690 | 2014-04-09 13:48:21 +0800 | [diff] [blame] | 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> |
Andrew Stubbs | ca0ebe0 | 2014-08-04 11:44:25 +0100 | [diff] [blame] | 181 | #include <wincrypt.h> |
| 182 | #ifndef __GNUC__ |
Michael Clark | 64e3690 | 2014-04-09 13:48:21 +0800 | [diff] [blame] | 183 | #pragma comment(lib, "advapi32.lib") |
Andrew Stubbs | ca0ebe0 | 2014-08-04 11:44:25 +0100 | [diff] [blame] | 184 | #endif |
Michael Clark | 64e3690 | 2014-04-09 13:48:21 +0800 | [diff] [blame] | 185 | |
| 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 | |
| 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 | |
| 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 | } |