From 38f916a798c3c0592bdca296855248d5eea19a68 Mon Sep 17 00:00:00 2001
From: Jacob Barthelmeh <jacob@wolfssl.com>
Date: Mon, 18 Jun 2018 15:50:44 -0600
Subject: [PATCH] sanity check on hashing size

---
 src/internal.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/src/internal.c b/src/internal.c
index 739c730b0..574040b77 100644
--- a/src/internal.c
+++ b/src/internal.c
@@ -12242,6 +12242,11 @@ static INLINE int VerifyMac(WOLFSSL* ssl, const byte* input, word32 msgSz,
         padByte = 1;
 
         if (ssl->options.tls) {
+            /* Sanity check for underflow, TimingPadVerify performs hash on size
+             * (msgSz - ivExtra) - digestSz - pad - 1 */
+            if (digestSz + pad + 1 > (msgSz - ivExtra)) {
+                return BUFFER_E;
+            }
             ret = TimingPadVerify(ssl, input, pad, digestSz, msgSz - ivExtra,
                                   content);
             if (ret != 0)