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238 lines
4.3 KiB
238 lines
4.3 KiB
/*
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* random_seed.c
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*
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* Copyright (c) 2013 Metaparadigm Pte. Ltd.
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* Michael Clark <michael@metaparadigm.com>
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*
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* This library is free software; you can redistribute it and/or modify
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* it under the terms of the MIT license. See COPYING for details.
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*
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*/
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#include <stdio.h>
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#include "config.h"
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#define DEBUG_SEED(s)
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#if defined ENABLE_RDRAND
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/* cpuid */
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#if defined __GNUC__ && (defined __i386__ || defined __x86_64__)
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#define HAS_X86_CPUID 1
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static void do_cpuid(int regs[], int h)
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{
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__asm__ __volatile__(
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#if defined __x86_64__
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"pushq %%rbx;\n"
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#else
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"pushl %%ebx;\n"
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#endif
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"cpuid;\n"
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#if defined __x86_64__
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"popq %%rbx;\n"
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#else
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"popl %%ebx;\n"
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#endif
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: "=a"(regs[0]), [ebx] "=r"(regs[1]), "=c"(regs[2]), "=d"(regs[3])
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: "a"(h));
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}
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#elif defined _MSC_VER
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#define HAS_X86_CPUID 1
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#define do_cpuid __cpuid
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#endif
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/* has_rdrand */
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#if HAS_X86_CPUID
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static int has_rdrand()
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{
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// CPUID.01H:ECX.RDRAND[bit 30] == 1
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int regs[4];
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do_cpuid(regs, 1);
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return (regs[2] & (1 << 30)) != 0;
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}
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#endif
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/* get_rdrand_seed - GCC x86 and X64 */
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#if defined __GNUC__ && (defined __i386__ || defined __x86_64__)
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#define HAVE_RDRAND 1
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static int get_rdrand_seed()
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{
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DEBUG_SEED("get_rdrand_seed");
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int _eax;
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// rdrand eax
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__asm__ __volatile__("1: .byte 0x0F\n"
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" .byte 0xC7\n"
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" .byte 0xF0\n"
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" jnc 1b;\n"
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: "=a" (_eax));
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return _eax;
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}
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#endif
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#if defined _MSC_VER
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#if _MSC_VER >= 1700
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#define HAVE_RDRAND 1
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/* get_rdrand_seed - Visual Studio 2012 and above */
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static int get_rdrand_seed()
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{
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DEBUG_SEED("get_rdrand_seed");
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int r;
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while (_rdrand32_step(&r) == 0);
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return r;
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}
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#elif defined _M_IX86
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#define HAVE_RDRAND 1
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/* get_rdrand_seed - Visual Studio 2010 and below - x86 only */
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static int get_rdrand_seed()
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{
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DEBUG_SEED("get_rdrand_seed");
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int _eax;
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retry:
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// rdrand eax
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__asm _emit 0x0F __asm _emit 0xC7 __asm _emit 0xF0
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__asm jnc retry
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__asm mov _eax, eax
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return _eax;
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}
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#endif
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#endif
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#endif /* defined ENABLE_RDRAND */
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/* has_dev_urandom */
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#if defined (__APPLE__) || defined(__unix__) || defined(__linux__)
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#include <string.h>
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#include <fcntl.h>
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#include <unistd.h>
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#include <errno.h>
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#include <stdlib.h>
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#include <sys/stat.h>
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#define HAVE_DEV_RANDOM 1
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static const char *dev_random_file = "/dev/urandom";
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static int has_dev_urandom()
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{
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struct stat buf;
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if (stat(dev_random_file, &buf)) {
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return 0;
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}
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return ((buf.st_mode & S_IFCHR) != 0);
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}
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/* get_dev_random_seed */
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static int get_dev_random_seed()
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{
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DEBUG_SEED("get_dev_random_seed");
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int fd = open(dev_random_file, O_RDONLY);
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if (fd < 0) {
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fprintf(stderr, "error opening %s: %s", dev_random_file, strerror(errno));
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exit(1);
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}
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int r;
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ssize_t nread = read(fd, &r, sizeof(r));
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if (nread != sizeof(r)) {
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fprintf(stderr, "error short read %s: %s", dev_random_file, strerror(errno));
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exit(1);
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}
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close(fd);
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return r;
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}
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#endif
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/* get_cryptgenrandom_seed */
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#ifdef WIN32
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#define HAVE_CRYPTGENRANDOM 1
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#include <windows.h>
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#include <wincrypt.h>
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#ifndef __GNUC__
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#pragma comment(lib, "advapi32.lib")
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#endif
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static int get_cryptgenrandom_seed()
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{
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DEBUG_SEED("get_cryptgenrandom_seed");
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HCRYPTPROV hProvider = 0;
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int r;
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if (!CryptAcquireContextW(&hProvider, 0, 0, PROV_RSA_FULL, CRYPT_VERIFYCONTEXT | CRYPT_SILENT)) {
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fprintf(stderr, "error CryptAcquireContextW");
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exit(1);
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}
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if (!CryptGenRandom(hProvider, sizeof(r), (BYTE*)&r)) {
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fprintf(stderr, "error CryptGenRandom");
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exit(1);
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}
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CryptReleaseContext(hProvider, 0);
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return r;
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}
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#endif
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/* get_time_seed */
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#include <time.h>
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static int get_time_seed()
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{
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DEBUG_SEED("get_time_seed");
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return (int)time(NULL) * 433494437;
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}
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/* json_c_get_random_seed */
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int json_c_get_random_seed()
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{
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#if HAVE_RDRAND
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if (has_rdrand()) return get_rdrand_seed();
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#endif
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#if HAVE_DEV_RANDOM
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if (has_dev_urandom()) return get_dev_random_seed();
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#endif
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#if HAVE_CRYPTGENRANDOM
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return get_cryptgenrandom_seed();
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#endif
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return get_time_seed();
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}
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