Портирование существующего генератора случайных чисел, для C

Question

Я заметил, что двигатель JavaScript (SpiderMonkey) в Mozilla Firefox, имеет надежный генератор случайных чисел, используя «Math.random()» функция

Поэтому я хочу взять/реализовать код за функцией «Math.random()» javascript (из проекта SpiderMonkey) в мою программу на C. Это возможно/законно? Или лучше создать собственную реализацию генератора случайных чисел?

IE: https://www.securecoding.cert.org/confluence/display/seccode/MSC30-C.+Do+not+use+the+rand%28%29+function+for+generating+pseudorandom+numbers

Answer 1

Есть BSD-лицензированные реализации C по Вихрь Мерсенна ПСЧ там. Статья Википедии о Mersenne может направить вас дальше (http://en.m.wikipedia.org/wiki/Mersenne_twister), а также реализации авторами алгоритма (http://www.math.sci.hiroshima-u.ac.jp/~m-mat/MT/MT2002/emt19937ar.html).

Answer 2

Если вы собираетесь использовать свой код на Linux, вы можете просто прочитать либо/dev/random (который может блокировать), либо/dev/urandom, который гарантированно не будет блокироваться. На вашей машине Linux вы можете получить дополнительную информацию, просмотрев справочную страницу для urandom.

Или .....

Вот реализация arc4random нашел here. Возможно, вам придется немного поработать с ним для компиляции/ссылки в вашей системе.

/* Portable arc4random.c based on arc4random.c from OpenBSD. 
* Portable version by Chris Davis, adapted for Libevent by Nick Mathewson 
* Copyright (c) 2010 Chris Davis, Niels Provos, and Nick Mathewson 
* Copyright (c) 2010-2012 Niels Provos and Nick Mathewson 
* 
* Note that in Libevent, this file isn't compiled directly. Instead, 
* it's included from evutil_rand.c 
*/ 

/* 
* Copyright (c) 1996, David Mazieres <dm@uun.org> 
* Copyright (c) 2008, Damien Miller <djm@openbsd.org> 
* 
* Permission to use, copy, modify, and distribute this software for any 
* purpose with or without fee is hereby granted, provided that the above 
* copyright notice and this permission notice appear in all copies. 
* 
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES 
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF 
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR 
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES 
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN 
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF 
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. 
*/ 

/* 
* Arc4 random number generator for OpenBSD. 
* 
* This code is derived from section 17.1 of Applied Cryptography, 
* second edition, which describes a stream cipher allegedly 
* compatible with RSA Labs "RC4" cipher (the actual description of 
* which is a trade secret). The same algorithm is used as a stream 
* cipher called "arcfour" in Tatu Ylonen's ssh package. 
* 
* Here the stream cipher has been modified always to include the time 
* when initializing the state. That makes it impossible to 
* regenerate the same random sequence twice, so this can't be used 
* for encryption, but will generate good random numbers. 
* 
* RC4 is a registered trademark of RSA Laboratories. 
*/ 

#ifndef ARC4RANDOM_EXPORT 
#define ARC4RANDOM_EXPORT 
#endif 

#ifndef ARC4RANDOM_UINT32 
#define ARC4RANDOM_UINT32 uint32_t 
#endif 

#ifndef ARC4RANDOM_NO_INCLUDES 
#include "evconfig-private.h" 
#ifdef _WIN32 
#include <wincrypt.h> 
#include <process.h> 
#else 
#include <fcntl.h> 
#include <unistd.h> 
#include <sys/param.h> 
#include <sys/time.h> 
#ifdef EVENT__HAVE_SYS_SYSCTL_H 
#include <sys/sysctl.h> 
#endif 
#endif 
#include <limits.h> 
#include <stdlib.h> 
#include <string.h> 
#endif 

/* Add platform entropy 32 bytes (256 bits) at a time. */ 
#define ADD_ENTROPY 32 

/* Re-seed from the platform RNG after generating this many bytes. */ 
#define BYTES_BEFORE_RESEED 1600000 

struct arc4_stream { 
    unsigned char i; 
    unsigned char j; 
    unsigned char s[256]; 
}; 

#ifdef _WIN32 
#define getpid _getpid 
#define pid_t int 
#endif 

static int rs_initialized; 
static struct arc4_stream rs; 
static pid_t arc4_stir_pid; 
static int arc4_count; 
static int arc4_seeded_ok; 

static inline unsigned char arc4_getbyte(void); 

static inline void 
arc4_init(void) 
{ 
    int  n; 

    for (n = 0; n < 256; n++) 
     rs.s[n] = n; 
    rs.i = 0; 
    rs.j = 0; 
} 

static inline void 
arc4_addrandom(const unsigned char *dat, int datlen) 
{ 
    int  n; 
    unsigned char si; 

    rs.i--; 
    for (n = 0; n < 256; n++) { 
     rs.i = (rs.i + 1); 
     si = rs.s[rs.i]; 
     rs.j = (rs.j + si + dat[n % datlen]); 
     rs.s[rs.i] = rs.s[rs.j]; 
     rs.s[rs.j] = si; 
    } 
    rs.j = rs.i; 
} 

#ifndef _WIN32 
static ssize_t 
read_all(int fd, unsigned char *buf, size_t count) 
{ 
    size_t numread = 0; 
    ssize_t result; 

    while (numread < count) { 
     result = read(fd, buf+numread, count-numread); 
     if (result<0) 
      return -1; 
     else if (result == 0) 
      break; 
     numread += result; 
    } 

    return (ssize_t)numread; 
} 
#endif 

#ifdef _WIN32 
#define TRY_SEED_WIN32 
static int 
arc4_seed_win32(void) 
{ 
    /* This is adapted from Tor's crypto_seed_rng() */ 
    static int provider_set = 0; 
    static HCRYPTPROV provider; 
    unsigned char buf[ADD_ENTROPY]; 

    if (!provider_set) { 
     if (!CryptAcquireContext(&provider, NULL, NULL, PROV_RSA_FULL, 
      CRYPT_VERIFYCONTEXT)) { 
      if (GetLastError() != (DWORD)NTE_BAD_KEYSET) 
       return -1; 
     } 
     provider_set = 1; 
    } 
    if (!CryptGenRandom(provider, sizeof(buf), buf)) 
     return -1; 
    arc4_addrandom(buf, sizeof(buf)); 
    evutil_memclear_(buf, sizeof(buf)); 
    arc4_seeded_ok = 1; 
    return 0; 
} 
#endif 

#if defined(EVENT__HAVE_SYS_SYSCTL_H) && defined(EVENT__HAVE_SYSCTL) 
#if EVENT__HAVE_DECL_CTL_KERN && EVENT__HAVE_DECL_KERN_RANDOM && EVENT__HAVE_DECL_RANDOM_UUID 
#define TRY_SEED_SYSCTL_LINUX 
static int 
arc4_seed_sysctl_linux(void) 
{ 
    /* Based on code by William Ahern, this function tries to use the 
    * RANDOM_UUID sysctl to get entropy from the kernel. This can work 
    * even if /dev/urandom is inaccessible for some reason (e.g., we're 
    * running in a chroot). */ 
    int mib[] = { CTL_KERN, KERN_RANDOM, RANDOM_UUID }; 
    unsigned char buf[ADD_ENTROPY]; 
    size_t len, n; 
    unsigned i; 
    int any_set; 

    memset(buf, 0, sizeof(buf)); 

    for (len = 0; len < sizeof(buf); len += n) { 
     n = sizeof(buf) - len; 

     if (0 != sysctl(mib, 3, &buf[len], &n, NULL, 0)) 
      return -1; 
    } 
    /* make sure that the buffer actually got set. */ 
    for (i=0,any_set=0; i<sizeof(buf); ++i) { 
     any_set |= buf[i]; 
    } 
    if (!any_set) 
     return -1; 

    arc4_addrandom(buf, sizeof(buf)); 
    evutil_memclear_(buf, sizeof(buf)); 
    arc4_seeded_ok = 1; 
    return 0; 
} 
#endif 

#if EVENT__HAVE_DECL_CTL_KERN && EVENT__HAVE_DECL_KERN_ARND 
#define TRY_SEED_SYSCTL_BSD 
static int 
arc4_seed_sysctl_bsd(void) 
{ 
    /* Based on code from William Ahern and from OpenBSD, this function 
    * tries to use the KERN_ARND syscall to get entropy from the kernel. 
    * This can work even if /dev/urandom is inaccessible for some reason 
    * (e.g., we're running in a chroot). */ 
    int mib[] = { CTL_KERN, KERN_ARND }; 
    unsigned char buf[ADD_ENTROPY]; 
    size_t len, n; 
    int i, any_set; 

    memset(buf, 0, sizeof(buf)); 

    len = sizeof(buf); 
    if (sysctl(mib, 2, buf, &len, NULL, 0) == -1) { 
     for (len = 0; len < sizeof(buf); len += sizeof(unsigned)) { 
      n = sizeof(unsigned); 
      if (n + len > sizeof(buf)) 
       n = len - sizeof(buf); 
      if (sysctl(mib, 2, &buf[len], &n, NULL, 0) == -1) 
       return -1; 
     } 
    } 
    /* make sure that the buffer actually got set. */ 
    for (i=any_set=0; i<sizeof(buf); ++i) { 
     any_set |= buf[i]; 
    } 
    if (!any_set) 
     return -1; 

    arc4_addrandom(buf, sizeof(buf)); 
    evutil_memclear_(buf, sizeof(buf)); 
    arc4_seeded_ok = 1; 
    return 0; 
} 
#endif 
#endif /* defined(EVENT__HAVE_SYS_SYSCTL_H) */ 

#ifdef __linux__ 
#define TRY_SEED_PROC_SYS_KERNEL_RANDOM_UUID 
static int 
arc4_seed_proc_sys_kernel_random_uuid(void) 
{ 
    /* Occasionally, somebody will make /proc/sys accessible in a chroot, 
    * but not /dev/urandom. Let's try /proc/sys/kernel/random/uuid. 
    * Its format is stupid, so we need to decode it from hex. 
    */ 
    int fd; 
    char buf[128]; 
    unsigned char entropy[64]; 
    int bytes, n, i, nybbles; 
    for (bytes = 0; bytes<ADD_ENTROPY;) { 
     fd = evutil_open_closeonexec_("/proc/sys/kernel/random/uuid", O_RDONLY, 0); 
     if (fd < 0) 
      return -1; 
     n = read(fd, buf, sizeof(buf)); 
     close(fd); 
     if (n<=0) 
      return -1; 
     memset(entropy, 0, sizeof(entropy)); 
     for (i=nybbles=0; i<n; ++i) { 
      if (EVUTIL_ISXDIGIT_(buf[i])) { 
       int nyb = evutil_hex_char_to_int_(buf[i]); 
       if (nybbles & 1) { 
        entropy[nybbles/2] |= nyb; 
       } else { 
        entropy[nybbles/2] |= nyb<<4; 
       } 
       ++nybbles; 
      } 
     } 
     if (nybbles < 2) 
      return -1; 
     arc4_addrandom(entropy, nybbles/2); 
     bytes += nybbles/2; 
    } 
    evutil_memclear_(entropy, sizeof(entropy)); 
    evutil_memclear_(buf, sizeof(buf)); 
    arc4_seeded_ok = 1; 
    return 0; 
} 
#endif 

#ifndef _WIN32 
#define TRY_SEED_URANDOM 
static char *arc4random_urandom_filename = NULL; 

static int arc4_seed_urandom_helper_(const char *fname) 
{ 
    unsigned char buf[ADD_ENTROPY]; 
    int fd; 
    size_t n; 

    fd = evutil_open_closeonexec_(fname, O_RDONLY, 0); 
    if (fd<0) 
     return -1; 
    n = read_all(fd, buf, sizeof(buf)); 
    close(fd); 
    if (n != sizeof(buf)) 
     return -1; 
    arc4_addrandom(buf, sizeof(buf)); 
    evutil_memclear_(buf, sizeof(buf)); 
    arc4_seeded_ok = 1; 
    return 0; 
} 

static int 
arc4_seed_urandom(void) 
{ 
    /* This is adapted from Tor's crypto_seed_rng() */ 
    static const char *filenames[] = { 
     "/dev/srandom", "/dev/urandom", "/dev/random", NULL 
    }; 
    int i; 
    if (arc4random_urandom_filename) 
     return arc4_seed_urandom_helper_(arc4random_urandom_filename); 

    for (i = 0; filenames[i]; ++i) { 
     if (arc4_seed_urandom_helper_(filenames[i]) == 0) { 
      return 0; 
     } 
    } 

    return -1; 
} 
#endif 

static int 
arc4_seed(void) 
{ 
    int ok = 0; 
    /* We try every method that might work, and don't give up even if one 
    * does seem to work. There's no real harm in over-seeding, and if 
    * one of these sources turns out to be broken, that would be bad. */ 
#ifdef TRY_SEED_WIN32 
    if (0 == arc4_seed_win32()) 
     ok = 1; 
#endif 
#ifdef TRY_SEED_URANDOM 
    if (0 == arc4_seed_urandom()) 
     ok = 1; 
#endif 
#ifdef TRY_SEED_PROC_SYS_KERNEL_RANDOM_UUID 
    if (arc4random_urandom_filename == NULL && 
     0 == arc4_seed_proc_sys_kernel_random_uuid()) 
     ok = 1; 
#endif 
#ifdef TRY_SEED_SYSCTL_LINUX 
    /* Apparently Linux is deprecating sysctl, and spewing warning 
    * messages when you try to use it. */ 
    if (!ok && 0 == arc4_seed_sysctl_linux()) 
     ok = 1; 
#endif 
#ifdef TRY_SEED_SYSCTL_BSD 
    if (0 == arc4_seed_sysctl_bsd()) 
     ok = 1; 
#endif 
    return ok ? 0 : -1; 
} 

static int 
arc4_stir(void) 
{ 
    int  i; 

    if (!rs_initialized) { 
     arc4_init(); 
     rs_initialized = 1; 
    } 

    arc4_seed(); 
    if (!arc4_seeded_ok) 
     return -1; 

    /* 
    * Discard early keystream, as per recommendations in 
    * "Weaknesses in the Key Scheduling Algorithm of RC4" by 
    * Scott Fluhrer, Itsik Mantin, and Adi Shamir. 
    * http://www.wisdom.weizmann.ac.il/~itsik/RC4/Papers/Rc4_ksa.ps 
    * 
    * Ilya Mironov's "(Not So) Random Shuffles of RC4" suggests that 
    * we drop at least 2*256 bytes, with 12*256 as a conservative 
    * value. 
    * 
    * RFC4345 says to drop 6*256. 
    * 
    * At least some versions of this code drop 4*256, in a mistaken 
    * belief that "words" in the Fluhrer/Mantin/Shamir paper refers 
    * to processor words. 
    * 
    * We add another sect to the cargo cult, and choose 12*256. 
    */ 
    for (i = 0; i < 12*256; i++) 
     (void)arc4_getbyte(); 

    arc4_count = BYTES_BEFORE_RESEED; 

    return 0; 
} 


static void 
arc4_stir_if_needed(void) 
{ 
    pid_t pid = getpid(); 

    if (arc4_count <= 0 || !rs_initialized || arc4_stir_pid != pid) 
    { 
     arc4_stir_pid = pid; 
     arc4_stir(); 
    } 
} 

static inline unsigned char 
arc4_getbyte(void) 
{ 
    unsigned char si, sj; 

    rs.i = (rs.i + 1); 
    si = rs.s[rs.i]; 
    rs.j = (rs.j + si); 
    sj = rs.s[rs.j]; 
    rs.s[rs.i] = sj; 
    rs.s[rs.j] = si; 
    return (rs.s[(si + sj) & 0xff]); 
} 

static inline unsigned int 
arc4_getword(void) 
{ 
    unsigned int val; 

    val = arc4_getbyte() << 24; 
    val |= arc4_getbyte() << 16; 
    val |= arc4_getbyte() << 8; 
    val |= arc4_getbyte(); 

    return val; 
} 

#ifndef ARC4RANDOM_NOSTIR 
ARC4RANDOM_EXPORT int 
arc4random_stir(void) 
{ 
    int val; 
    ARC4_LOCK_(); 
    val = arc4_stir(); 
    ARC4_UNLOCK_(); 
    return val; 
} 
#endif 

#ifndef ARC4RANDOM_NOADDRANDOM 
ARC4RANDOM_EXPORT void 
arc4random_addrandom(const unsigned char *dat, int datlen) 
{ 
    int j; 
    ARC4_LOCK_(); 
    if (!rs_initialized) 
     arc4_stir(); 
    for (j = 0; j < datlen; j += 256) { 
     /* arc4_addrandom() ignores all but the first 256 bytes of 
     * its input. We want to make sure to look at ALL the 
     * data in 'dat', just in case the user is doing something 
     * crazy like passing us all the files in /var/log. */ 
     arc4_addrandom(dat + j, datlen - j); 
    } 
    ARC4_UNLOCK_(); 
} 
#endif 

#ifndef ARC4RANDOM_NORANDOM 
ARC4RANDOM_EXPORT ARC4RANDOM_UINT32 
arc4random(void) 
{ 
    ARC4RANDOM_UINT32 val; 
    ARC4_LOCK_(); 
    arc4_count -= 4; 
    arc4_stir_if_needed(); 
    val = arc4_getword(); 
    ARC4_UNLOCK_(); 
    return val; 
} 
#endif 

ARC4RANDOM_EXPORT void 
arc4random_buf(void *buf_, size_t n) 
{ 
    unsigned char *buf = buf_; 
    ARC4_LOCK_(); 
    arc4_stir_if_needed(); 
    while (n--) { 
     if (--arc4_count <= 0) 
      arc4_stir(); 
     buf[n] = arc4_getbyte(); 
    } 
    ARC4_UNLOCK_(); 
} 

#ifndef ARC4RANDOM_NOUNIFORM 
/* 
* Calculate a uniformly distributed random number less than upper_bound 
* avoiding "modulo bias". 
* 
* Uniformity is achieved by generating new random numbers until the one 
* returned is outside the range [0, 2**32 % upper_bound). This 
* guarantees the selected random number will be inside 
* [2**32 % upper_bound, 2**32) which maps back to [0, upper_bound) 
* after reduction modulo upper_bound. 
*/ 
ARC4RANDOM_EXPORT unsigned int 
arc4random_uniform(unsigned int upper_bound) 
{ 
    ARC4RANDOM_UINT32 r, min; 

    if (upper_bound < 2) 
     return 0; 

#if (UINT_MAX > 0xffffffffUL) 
    min = 0x100000000UL % upper_bound; 
#else 
    /* Calculate (2**32 % upper_bound) avoiding 64-bit math */ 
    if (upper_bound > 0x80000000) 
     min = 1 + ~upper_bound;  /* 2**32 - upper_bound */ 
    else { 
     /* (2**32 - (x * 2)) % x == 2**32 % x when x <= 2**31 */ 
     min = ((0xffffffff - (upper_bound * 2)) + 1) % upper_bound; 
    } 
#endif 

    /* 
    * This could theoretically loop forever but each retry has 
    * p > 0.5 (worst case, usually far better) of selecting a 
    * number inside the range we need, so it should rarely need 
    * to re-roll. 
    */ 
    for (;;) { 
     r = arc4random(); 
     if (r >= min) 
      break; 
    } 

    return r % upper_bound; 
} 
#endif