Merge pull request #206 from carbin/arc4random

use arc4random on platforms that support it

Author: FROGGS

3rdparty/libtommath/bn_mp_rand.c

@@ -29,7 +29,7 @@ mp_rand (mp_int * a, int digits)
 
   /* first place a random non-zero digit */
   do {
-    d = ((mp_digit) abs (rand ())) & MP_MASK;
+    d = ((mp_digit) abs (MP_GEN_RANDOM())) & MP_MASK;
   } while (d == 0);
 
   if ((res = mp_add_d (a, d, a)) != MP_OKAY) {
@@ -41,7 +41,7 @@ mp_rand (mp_int * a, int digits)
       return res;
     }
 
-    if ((res = mp_add_d (a, ((mp_digit) abs (rand ())), a)) != MP_OKAY) {
+    if ((res = mp_add_d (a, ((mp_digit) abs (MP_GEN_RANDOM())), a)) != MP_OKAY) {
       return res;
     }
   }

3rdparty/libtommath/tommath.h

@@ -127,6 +127,18 @@ extern "C" {
    #define DIGIT_BIT     ((int)((CHAR_BIT * sizeof(mp_digit) - 1)))  /* bits per digit */
 #endif
 
+/* platforms that can use a better rand function */
+#if defined(__FreeBSD__) || defined(__OpenBSD__) || defined(__NetBSD__) || defined(__DragonFly__)
+    #define MP_USE_ALT_RAND 1
+#endif
+
+/* use arc4random on platforms that support it */
+#ifdef MP_USE_ALT_RAND
+    #define MP_GEN_RANDOM()    arc4random()
+#else
+    #define MP_GEN_RANDOM()    rand()
+#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