From 55d485cc457d80e5bb3a44503b9c0e84661bf7b0 Mon Sep 17 00:00:00 2001
From: Sean Parkinson <sean@wolfssl.com>
Date: Wed, 22 Jan 2020 09:37:45 -0800
Subject: [PATCH] Fix masking of 16 bits

---
 wolfcrypt/src/misc.c     | 12 +++++++++++-
 wolfssl/wolfcrypt/misc.h |  2 ++
 2 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/wolfcrypt/src/misc.c b/wolfcrypt/src/misc.c
index 6e1f41a55..7f779dc24 100644
--- a/wolfcrypt/src/misc.c
+++ b/wolfcrypt/src/misc.c
@@ -356,9 +356,19 @@ WC_STATIC WC_INLINE byte ctMaskEq(int a, int b)
     return (~ctMaskGT(a, b)) & (~ctMaskLT(a, b));
 }
 
+WC_STATIC WC_INLINE word16 ctMask16GT(int a, int b)
+{
+    return (((word32)a - b - 1) >> 31) - 1;
+}
+
+WC_STATIC WC_INLINE word16 ctMask16LT(int a, int b)
+{
+    return (((word32)a - b - 1) >> 31) - 1;
+}
+
 WC_STATIC WC_INLINE word16 ctMask16Eq(int a, int b)
 {
-    return (~ctMaskGT(a, b)) & (~ctMaskLT(a, b));
+    return (~ctMask16GT(a, b)) & (~ctMask16LT(a, b));
 }
 
 /* Constant time - mask set when a != b. */
diff --git a/wolfssl/wolfcrypt/misc.h b/wolfssl/wolfcrypt/misc.h
index 45fa699af..d5237dec0 100644
--- a/wolfssl/wolfcrypt/misc.h
+++ b/wolfssl/wolfcrypt/misc.h
@@ -98,6 +98,8 @@ WOLFSSL_LOCAL int  ctMaskIntGTE(int a, int b);
 WOLFSSL_LOCAL byte ctMaskLT(int a, int b);
 WOLFSSL_LOCAL byte ctMaskLTE(int a, int b);
 WOLFSSL_LOCAL byte ctMaskEq(int a, int b);
+WOLFSSL_LOCAL word16 ctMask16GT(int a, int b);
+WOLFSSL_LOCAL word16 ctMask16LT(int a, int b);
 WOLFSSL_LOCAL word16 ctMask16Eq(int a, int b);
 WOLFSSL_LOCAL byte ctMaskNotEq(int a, int b);
 WOLFSSL_LOCAL byte ctMaskSel(byte m, byte a, byte b);