release/src/router/libjson-c/random_seed.c

   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)) {
 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
 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 }