From dd48c825ed2d298209c4c596a8b193d0afe97835 Mon Sep 17 00:00:00 2001
From: Sean Parkinson <sean@wolfssl.com>
Date: Fri, 9 Aug 2019 11:50:07 -0600
Subject: [PATCH] Constant compare the HMAC result when using NULL cipher and
 TLS 1.3

---
 src/tls13.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/tls13.c b/src/tls13.c
index 234623601..1c4123b92 100644
--- a/src/tls13.c
+++ b/src/tls13.c
@@ -1935,7 +1935,7 @@ static int Tls13IntegrityOnly_Decrypt(WOLFSSL* ssl, byte* output,
     if (ret == 0)
         ret = wc_HmacFinal(ssl->decrypt.hmac, hmac);
     /* Check authentication tag matches */
-    if (ret == 0 && XMEMCMP(tagIn, hmac, ssl->specs.hash_size) != 0)
+    if (ret == 0 && ConstantCompare(tagIn, hmac, ssl->specs.hash_size) != 0)
         ret = DECRYPT_ERROR;
     /* Copy the input to output if not the same buffer */
     if (ret == 0 && output != input)