X-Git-Url: https://git.librecmc.org/?a=blobdiff_plain;f=src%2Futil%2Fcrypto_random.c;h=25ba4db2a81ac94c9172c82c428590288ca7e474;hb=0ea8e006d5f5ef84e31e000607bd24a23f8fc1ed;hp=b56523a4685a3810eb67f4584ccb5cf1449cce1f;hpb=c2d3d24cd9b4f552d7ca8ad6283f9819c1cfefc7;p=oweals%2Fgnunet.git

diff --git a/src/util/crypto_random.c b/src/util/crypto_random.c
index b56523a46..25ba4db2a 100644
--- a/src/util/crypto_random.c
+++ b/src/util/crypto_random.c
@@ -30,16 +30,32 @@
 #include <gcrypt.h>
 
 /**
+ * Create a cryptographically weak pseudo-random number in the interval of 0 to 1.
+ * 
+ * @return number between 0 and 1.
+ */
+static double
+weak_random ()
+{
+  return ((double) RANDOM () / RAND_MAX);
+}
+
+
+/**
+ * Produce a random value.
+ *
+ * @param mode desired quality of the random number
+ * @param i the upper limit (exclusive) for the random number
  * @return a random value in the interval [0,i[.
  */
 uint32_t
-GNUNET_CRYPTO_random_u32 (enum GNUNET_CRYPTO_Quality mode, 
-			  uint32_t i)
+GNUNET_CRYPTO_random_u32 (enum GNUNET_CRYPTO_Quality mode, uint32_t i)
 {
 #ifdef gcry_fast_random_poll
   static unsigned int invokeCount;
 #endif
   uint32_t ret;
+  uint32_t ul;
 
   GNUNET_assert (i > 0);
 
@@ -50,14 +66,18 @@ GNUNET_CRYPTO_random_u32 (enum GNUNET_CRYPTO_Quality mode,
       if ((invokeCount++ % 256) == 0)
         gcry_fast_random_poll ();
 #endif
-      gcry_randomize ((unsigned char *) &ret,
-                      sizeof (uint32_t),
-		      GCRY_STRONG_RANDOM);
+      ul = UINT32_MAX - (UINT32_MAX % i);
+      do
+	{
+	  gcry_randomize ((unsigned char *) &ret,
+			  sizeof (uint32_t), GCRY_STRONG_RANDOM);
+	}
+      while (ret >= ul);
       return ret % i;
     }
   else
     {
-      ret = i * ((double) RANDOM () / RAND_MAX);
+      ret = i * weak_random ();
       if (ret >= i)
         ret = i - 1;
       return ret;
@@ -85,9 +105,9 @@ GNUNET_CRYPTO_random_permute (enum GNUNET_CRYPTO_Quality mode, unsigned int n)
   ret = GNUNET_malloc (n * sizeof (unsigned int));
   for (i = 0; i < n; i++)
     ret[i] = i;
-  for (i = 0; i < n; i++)
+  for (i = n - 1; i > 0; i--)
     {
-      x = GNUNET_CRYPTO_random_u32 (mode, n);
+      x = GNUNET_CRYPTO_random_u32 (mode, i+1);
       tmp = ret[x];
       ret[x] = ret[i];
       ret[i] = tmp;
@@ -97,26 +117,35 @@ GNUNET_CRYPTO_random_permute (enum GNUNET_CRYPTO_Quality mode, unsigned int n)
 
 /**
  * Random on unsigned 64-bit values.
+ *
+ *
+ * @param mode desired quality of the random number
+ * @param max value returned will be in range [0,max) (exclusive)
+ * @return random 64-bit number
  */
 uint64_t
-GNUNET_CRYPTO_random_u64 (enum GNUNET_CRYPTO_Quality mode,
-                          uint64_t u)
+GNUNET_CRYPTO_random_u64 (enum GNUNET_CRYPTO_Quality mode, uint64_t max)
 {
   uint64_t ret;
+  uint64_t ul;
 
-  GNUNET_assert (u > 0);
+  GNUNET_assert (max > 0);
   if (mode == GNUNET_CRYPTO_QUALITY_STRONG)
     {
-      gcry_randomize ((unsigned char *) &ret,
-                      sizeof (uint64_t),
-		      GCRY_STRONG_RANDOM);
-      return ret % u;
+      ul = UINT64_MAX - (UINT64_MAX % max);
+      do
+	{
+	  gcry_randomize ((unsigned char *) &ret,
+			  sizeof (uint64_t), GCRY_STRONG_RANDOM);
+	}
+      while (ret >= ul);
+      return ret % max;
     }
   else
     {
-      ret = u * ((double) RANDOM () / RAND_MAX);
-      if (ret >= u)
-        ret = u - 1;
+      ret = max * weak_random ();
+      if (ret >= max)
+        ret = max - 1;
       return ret;
     }
 }
@@ -135,8 +164,7 @@ GNUNET_CRYPTO_random_disable_entropy_gathering ()
 /**
  * Initializer
  */
-void __attribute__ ((constructor))
-GNUNET_util_random_init()
+void __attribute__ ((constructor)) GNUNET_util_random_init ()
 {
   SRANDOM (time (NULL));
 }