X-Git-Url: https://git.librecmc.org/?a=blobdiff_plain;f=src%2Futil%2Fcrypto_random.c;h=25ba4db2a81ac94c9172c82c428590288ca7e474;hb=0ea8e006d5f5ef84e31e000607bd24a23f8fc1ed;hp=5d85d1daa1376d5b2f96b5f2ba146acd69e8664a;hpb=652e89b59ed2207c2c12172fdabcd6e659995c81;p=oweals%2Fgnunet.git

diff --git a/src/util/crypto_random.c b/src/util/crypto_random.c
index 5d85d1daa..25ba4db2a 100644
--- a/src/util/crypto_random.c
+++ b/src/util/crypto_random.c
@@ -29,6 +29,18 @@
 #include "gnunet_crypto_lib.h"
 #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.
  *
@@ -43,6 +55,7 @@ GNUNET_CRYPTO_random_u32 (enum GNUNET_CRYPTO_Quality mode, uint32_t i)
   static unsigned int invokeCount;
 #endif
   uint32_t ret;
+  uint32_t ul;
 
   GNUNET_assert (i > 0);
 
@@ -53,13 +66,18 @@ GNUNET_CRYPTO_random_u32 (enum GNUNET_CRYPTO_Quality mode, uint32_t i)
       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;
@@ -87,9 +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;
@@ -109,17 +127,23 @@ uint64_t
 GNUNET_CRYPTO_random_u64 (enum GNUNET_CRYPTO_Quality mode, uint64_t max)
 {
   uint64_t ret;
+  uint64_t ul;
 
   GNUNET_assert (max > 0);
   if (mode == GNUNET_CRYPTO_QUALITY_STRONG)
     {
-      gcry_randomize ((unsigned char *) &ret,
-                      sizeof (uint64_t), GCRY_STRONG_RANDOM);
+      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 = max * ((double) RANDOM () / RAND_MAX);
+      ret = max * weak_random ();
       if (ret >= max)
         ret = max - 1;
       return ret;