Merge remote-tracking branch 'public/bug15745_027_03'

1 files changed, 20 insertions, 1 deletions

diff --git a/src/common/crypto.c b/src/common/crypto.c
index 1b45639a7c..e723f3d5d2 100644
--- a/src/common/crypto.c
+++ b/src/common/crypto.c
@@ -2317,6 +2317,25 @@ crypto_rand_int(unsigned int max)
   }
 }
 
+/** Return a pseudorandom integer, chosen uniformly from the values <i>i</i>
+ * such that <b>min</b> &lt;= <i>i</i> &lt <b>max</b>.
+ *
+ * <b>min</b> MUST be in range [0, <b>max</b>).
+ * <b>max</b> MUST be in range (min, INT_MAX].
+ */
+int
+crypto_rand_int_range(unsigned int min, unsigned int max)
+{
+  tor_assert(min < max);
+  tor_assert(max <= INT_MAX);
+
+  /* The overflow is avoided here because crypto_rand_int() returns a value
+   * between 0 and (max - min - 1) with max being <= INT_MAX and min <= max.
+   * This is why we add 1 to the maximum value so we can actually get max as
+   * a return value. */
+  return min + crypto_rand_int(max - min);
+}
+
 /** Return a pseudorandom 64-bit integer, chosen uniformly from the values
  * between 0 and <b>max</b>-1. */
 uint64_t
@@ -2379,7 +2398,7 @@ crypto_random_hostname(int min_rand_len, int max_rand_len, const char *prefix,
   if (min_rand_len > max_rand_len)
     min_rand_len = max_rand_len;
 
-  randlen = min_rand_len + crypto_rand_int(max_rand_len - min_rand_len + 1);
+  randlen = crypto_rand_int_range(min_rand_len, max_rand_len+1);
 
   prefixlen = strlen(prefix);
   resultlen = prefixlen + strlen(suffix) + randlen + 16;