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 25static 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 54static 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 70static 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 92static 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 105static int get_rdrand_seed() 106{ 107 DEBUG_SEED("get_rdrand_seed"); 108 int _eax; 109retry: 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 136static const char *dev_random_file = "/dev/urandom"; 137 138static 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 150static 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 read %s: %s", dev_random_file, strerror(errno)); 164 exit(1); 165 } 166 else if (nread != sizeof(r)) { 167 fprintf(stderr, "error short read %s", dev_random_file); 168 exit(1); 169 } 170 close(fd); 171 return r; 172} 173 174#endif 175 176 177/* get_cryptgenrandom_seed */ 178 179#ifdef WIN32 180 181#define HAVE_CRYPTGENRANDOM 1 182 183#include <windows.h> 184#pragma comment(lib, "advapi32.lib") 185 186static 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 215static 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 225int 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