Return if ssleay_rand_add called with zero num.

Treat a zero length passed to ssleay_rand_add a no op: the existing logic zeroes the md value which is very bad. OpenSSL itself never does this internally and the actual call doesn't make sense as it would be passing zero bytes of entropy. Thanks to Marcus Meissner <meissner@suse.de> for reporting this bug.
openssl · Apr 7, 2014 · 5be1ae2 · 5be1ae2
1 parent 96db902
commit 5be1ae2
Showing 1 changed file with 3 additions and 0 deletions.
diff --git a/crypto/rand/md_rand.c b/crypto/rand/md_rand.c
@@ -198,6 +198,9 @@ static void ssleay_rand_add(const void *buf, int num, double add)
 	EVP_MD_CTX m;
 	int do_not_lock;
 
+	if (!num)
+		return;
+
 	/*
 	 * (Based on the rand(3) manpage)
 	 *