Commit d5b0f1e993f3a9ed915ec875bfa5c47b380162b4
2016-04-10T13:55:42
loop&shift until enough random data has been read
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54
diff --git a/bn_mp_rand.c b/bn_mp_rand.c
index 6f300c0..fc98e52 100644
--- a/bn_mp_rand.c
+++ b/bn_mp_rand.c
@@ -15,15 +15,28 @@
* Tom St Denis, tstdenis82@gmail.com, http://libtom.org
*/
+#if MP_GEN_RANDOM_MAX == 0xffffffff
+ #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
+
/* makes a pseudo-random int of a given size */
static mp_digit mp_gen_random(void)
{
- mp_digit d;
- d = ((mp_digit) abs (MP_GEN_RANDOM()));
-#if MP_DIGIT_BIT > 32
- d <<= 32;
- d |= ((mp_digit) abs (MP_GEN_RANDOM()));
-#endif
+ mp_digit d = 0, msk = 0;
+ do {
+ d <<= MP_GEN_RANDOM_SHIFT;
+ d |= ((mp_digit) MP_GEN_RANDOM());
+ msk <<= MP_GEN_RANDOM_SHIFT;
+ msk |= MP_GEN_RANDOM_MAX;
+ } while ((MP_MASK & msk) != MP_MASK);
d &= MP_MASK;
return d;
}
diff --git a/tommath.h b/tommath.h
index cec3722..b1a97af 100644
--- a/tommath.h
+++ b/tommath.h
@@ -102,8 +102,10 @@ extern "C" {
/* use arc4random on platforms that support it */
#ifdef MP_USE_ALT_RAND
#define MP_GEN_RANDOM() arc4random()
+ #define MP_GEN_RANDOM_MAX 0xffffffff
#else
#define MP_GEN_RANDOM() rand()
+ #define MP_GEN_RANDOM_MAX RAND_MAX
#endif
#define MP_DIGIT_BIT DIGIT_BIT