view libtommath/bn_mp_rand.c @ 1663:c795520269f9

Fallback for key gen without hard link support (#89) Add a non-atomic fallback for key generation on platforms where link() is not permitted (such as most stock Android installs) or on filesystems without hard link support (such as FAT).
author Matt Robinson <git@nerdoftheherd.com>
date Sat, 14 Mar 2020 14:37:35 +0000
parents f52919ffd3b1
children 1051e4eea25a
line wrap: on
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#include "tommath_private.h"
#ifdef BN_MP_RAND_C
/* LibTomMath, multiple-precision integer library -- Tom St Denis
 *
 * LibTomMath is a library that provides multiple-precision
 * integer arithmetic as well as number theoretic functionality.
 *
 * The library was designed directly after the MPI library by
 * Michael Fromberger but has been written from scratch with
 * additional optimizations in place.
 *
 * SPDX-License-Identifier: Unlicense
 */

/* First the OS-specific special cases
 * - *BSD
 * - Windows
 */
#if defined(__FreeBSD__) || defined(__OpenBSD__) || defined(__NetBSD__) || defined(__DragonFly__)
#define MP_ARC4RANDOM
#define MP_GEN_RANDOM_MAX     0xffffffffu
#define MP_GEN_RANDOM_SHIFT   32

static int s_read_arc4random(mp_digit *p)
{
   mp_digit d = 0, msk = 0;
   do {
      d <<= MP_GEN_RANDOM_SHIFT;
      d |= ((mp_digit) arc4random());
      msk <<= MP_GEN_RANDOM_SHIFT;
      msk |= (MP_MASK & MP_GEN_RANDOM_MAX);
   } while ((MP_MASK & msk) != MP_MASK);
   *p = d;
   return MP_OKAY;
}
#endif

#if defined(_WIN32) || defined(_WIN32_WCE)
#define MP_WIN_CSP

#ifndef _WIN32_WINNT
#define _WIN32_WINNT 0x0400
#endif
#ifdef _WIN32_WCE
#define UNDER_CE
#define ARM
#endif

#define WIN32_LEAN_AND_MEAN
#include <windows.h>
#include <wincrypt.h>

static HCRYPTPROV hProv = 0;

static void s_cleanup_win_csp(void)
{
   CryptReleaseContext(hProv, 0);
   hProv = 0;
}

static int s_read_win_csp(mp_digit *p)
{
   int ret = -1;
   if (hProv == 0) {
      if (!CryptAcquireContext(&hProv, NULL, MS_DEF_PROV, PROV_RSA_FULL,
                               (CRYPT_VERIFYCONTEXT | CRYPT_MACHINE_KEYSET)) &&
          !CryptAcquireContext(&hProv, NULL, MS_DEF_PROV, PROV_RSA_FULL,
                               CRYPT_VERIFYCONTEXT | CRYPT_MACHINE_KEYSET | CRYPT_NEWKEYSET)) {
         hProv = 0;
         return ret;
      }
      atexit(s_cleanup_win_csp);
   }
   if (CryptGenRandom(hProv, sizeof(*p), (void *)p) == TRUE) {
      ret = MP_OKAY;
   }
   return ret;
}
#endif /* WIN32 */

#if !defined(MP_WIN_CSP) && defined(__linux__) && defined(__GLIBC_PREREQ)
#if __GLIBC_PREREQ(2, 25)
#define MP_GETRANDOM
#include <sys/random.h>
#include <errno.h>

static int s_read_getrandom(mp_digit *p)
{
   int ret;
   do {
      ret = getrandom(p, sizeof(*p), 0);
   } while ((ret == -1) && (errno == EINTR));
   if (ret == sizeof(*p)) return MP_OKAY;
   return -1;
}
#endif
#endif

/* We assume all platforms besides windows provide "/dev/urandom".
 * In case yours doesn't, define MP_NO_DEV_URANDOM at compile-time.
 */
#if !defined(MP_WIN_CSP) && !defined(MP_NO_DEV_URANDOM)
#ifndef MP_DEV_URANDOM
#define MP_DEV_URANDOM "/dev/urandom"
#endif
#include <fcntl.h>
#include <errno.h>
#include <unistd.h>

static int s_read_dev_urandom(mp_digit *p)
{
   ssize_t r;
   int fd;
   do {
      fd = open(MP_DEV_URANDOM, O_RDONLY);
   } while ((fd == -1) && (errno == EINTR));
   if (fd == -1) return -1;
   do {
      r = read(fd, p, sizeof(*p));
   } while ((r == -1) && (errno == EINTR));
   close(fd);
   if (r != sizeof(*p)) return -1;
   return MP_OKAY;
}
#endif

#if defined(MP_PRNG_ENABLE_LTM_RNG)
unsigned long (*ltm_rng)(unsigned char *out, unsigned long outlen, void (*callback)(void));
void (*ltm_rng_callback)(void);

static int s_read_ltm_rng(mp_digit *p)
{
   unsigned long ret;
   if (ltm_rng == NULL) return -1;
   ret = ltm_rng((void *)p, sizeof(*p), ltm_rng_callback);
   if (ret != sizeof(*p)) return -1;
   return MP_OKAY;
}
#endif

static int s_rand_digit(mp_digit *p)
{
   int ret = -1;

#if defined(MP_ARC4RANDOM)
   ret = s_read_arc4random(p);
   if (ret == MP_OKAY) return ret;
#endif

#if defined(MP_WIN_CSP)
   ret = s_read_win_csp(p);
   if (ret == MP_OKAY) return ret;
#else

#if defined(MP_GETRANDOM)
   ret = s_read_getrandom(p);
   if (ret == MP_OKAY) return ret;
#endif
#if defined(MP_DEV_URANDOM)
   ret = s_read_dev_urandom(p);
   if (ret == MP_OKAY) return ret;
#endif

#endif /* MP_WIN_CSP */

#if defined(MP_PRNG_ENABLE_LTM_RNG)
   ret = s_read_ltm_rng(p);
   if (ret == MP_OKAY) return ret;
#endif

   return ret;
}

/* makes a pseudo-random int of a given size */
int mp_rand_digit(mp_digit *r)
{
   int ret = s_rand_digit(r);
   *r &= MP_MASK;
   return ret;
}

int mp_rand(mp_int *a, int digits)
{
   int     res;
   mp_digit d;

   mp_zero(a);
   if (digits <= 0) {
      return MP_OKAY;
   }

   /* first place a random non-zero digit */
   do {
      if (mp_rand_digit(&d) != MP_OKAY) {
         return MP_VAL;
      }
   } while (d == 0u);

   if ((res = mp_add_d(a, d, a)) != MP_OKAY) {
      return res;
   }

   while (--digits > 0) {
      if ((res = mp_lshd(a, 1)) != MP_OKAY) {
         return res;
      }

      if (mp_rand_digit(&d) != MP_OKAY) {
         return MP_VAL;
      }
      if ((res = mp_add_d(a, d, a)) != MP_OKAY) {
         return res;
      }
   }

   return MP_OKAY;
}
#endif

/* ref:         HEAD -> master, tag: v1.1.0 */
/* git commit:  08549ad6bc8b0cede0b357a9c341c5c6473a9c55 */
/* commit time: 2019-01-28 20:32:32 +0100 */