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Merged
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May 1, 2018
Merged

Fix #103 #105

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186 changes: 164 additions & 22 deletions bn_mp_rand.c
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Original file line number Diff line number Diff line change
Expand Up @@ -13,34 +13,171 @@
* guarantee it works.
*/

#if defined(MP_8BIT) || defined(MP_16BIT)
#define MP_GEN_RANDOM_SHIFT DIGIT_BIT
#else
#if MP_GEN_RANDOM_MAX == 0xffffffffu
#define MP_GEN_RANDOM_SHIFT 32
#elif MP_GEN_RANDOM_MAX == 32767
/* SHRT_MAX */
#define MP_GEN_RANDOM_SHIFT 15
#elif MP_GEN_RANDOM_MAX == 2147483647
/* INT_MAX */
#define MP_GEN_RANDOM_SHIFT 31
#elif !defined(MP_GEN_RANDOM_SHIFT)
#error Thou shalt define their own valid MP_GEN_RANDOM_SHIFT
#endif
#endif
/* 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

/* makes a pseudo-random int of a given size */
static mp_digit s_gen_random(void)
static int s_read_arc4random(mp_digit* p)
{
mp_digit d = 0, msk = 0;
do {
d <<= MP_GEN_RANDOM_SHIFT;
d |= ((mp_digit) MP_GEN_RANDOM());
d |= ((mp_digit) arc4random());
msk <<= MP_GEN_RANDOM_SHIFT;
msk |= (MP_MASK & MP_GEN_RANDOM_MAX);
} while ((MP_MASK & msk) != MP_MASK);
d &= MP_MASK;
return d;
*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));
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@sebastianas sebastianas Apr 14, 2018 •
edited by sjaeckel
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-   return ret;
+   if (ret == sizeof(*p))
+          return MP_OKAY;
+   return -1;

otherwise you do this and fallback to /dev/urandom because getrandom returns the number of random bytes.

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done

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 */
static int s_gen_random(mp_digit *r)
{
int ret = s_rand_digit(r);
*r &= MP_MASK;
return ret;
}

int mp_rand(mp_int *a, int digits)
Expand All @@ -55,7 +192,9 @@ int mp_rand(mp_int *a, int digits)

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

if ((res = mp_add_d(a, d, a)) != MP_OKAY) {
Expand All @@ -67,7 +206,10 @@ int mp_rand(mp_int *a, int digits)
return res;
}

if ((res = mp_add_d(a, s_gen_random(), a)) != MP_OKAY) {
if (s_gen_random(&d) != MP_OKAY) {
return MP_VAL;
}
if ((res = mp_add_d(a, d, a)) != MP_OKAY) {
return res;
}
}
Expand Down
20 changes: 8 additions & 12 deletions tommath.h
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Original file line number Diff line number Diff line change
Expand Up @@ -100,18 +100,6 @@ typedef uint_least32_t mp_min_u32;
typedef mp_digit mp_min_u32;
#endif

/* use arc4random on platforms that support it */
#if defined(__FreeBSD__) || defined(__OpenBSD__) || defined(__NetBSD__) || defined(__DragonFly__)
# define MP_GEN_RANDOM() arc4random()
# define MP_GEN_RANDOM_MAX 0xffffffffu
#endif

/* use rand() as fall-back if there's no better rand function */
#ifndef MP_GEN_RANDOM
# define MP_GEN_RANDOM() rand()
# define MP_GEN_RANDOM_MAX RAND_MAX
#endif

#define MP_DIGIT_BIT DIGIT_BIT
#define MP_MASK ((((mp_digit)1)<<((mp_digit)DIGIT_BIT))-((mp_digit)1))
#define MP_DIGIT_MAX MP_MASK
Expand Down Expand Up @@ -287,6 +275,14 @@ int mp_cnt_lsb(const mp_int *a);
/* makes a pseudo-random int of a given size */
int mp_rand(mp_int *a, int digits);

#ifdef MP_PRNG_ENABLE_LTM_RNG
/* as last resort we will fall back to libtomcrypt's rng_get_bytes()
* in case you don't use libtomcrypt or use it w/o rng_get_bytes()
* you have to implement it somewhere else, as it's required */
extern unsigned long (*ltm_rng)(unsigned char *out, unsigned long outlen, void (*callback)(void));
extern void (*ltm_rng_callback)(void);
#endif

/* ---> binary operations <--- */
/* c = a XOR b */
int mp_xor(const mp_int *a, const mp_int *b, mp_int *c);
Expand Down