clarify comment

diff --git a/crypto/rand/md_rand.c b/crypto/rand/md_rand.c
index 4e581f3917318c982de9f34b6f2f34d99fdedcbf..943c936483bb2d087215964ff19f10a65e3df09a 100644 (file)
--- a/crypto/rand/md_rand.c
+++ b/crypto/rand/md_rand.c
@@ -492,12 +492,15 @@ static int ssleay_rand_bytes(unsigned char *buf, int num)
                        goto err;
 
 #ifndef PURIFY /* purify complains */
                        goto err;
 
 #ifndef PURIFY /* purify complains */

-               /* DO NOT REMOVE THE FOLLOWING CALL TO MD_Update()! */
+               /* The following line uses the supplied buffer as a small
+                * source of entropy: since this buffer is often uninitialised
+                * it may cause programs such as purify or valgrind to
+                * complain. So for those builds it is not used: the removal
+                * of such a small source of entropy has negligible impact on
+                * security.
+                */

                if (!MD_Update(&m,buf,j))
                        goto err;
                if (!MD_Update(&m,buf,j))
                        goto err;

-               /* We know that line may cause programs such as
-                  purify and valgrind to complain about use of
-                  uninitialized data.  */

 #endif
 
                k=(st_idx+MD_DIGEST_LENGTH/2)-st_num;
 #endif
 
                k=(st_idx+MD_DIGEST_LENGTH/2)-st_num;