From e3277c19b7f484e260306afc2bc9e58afffa7e21 Mon Sep 17 00:00:00 2001
From: Jacob Barthelmeh <jacob@wolfssl.com>
Date: Tue, 10 Jan 2017 15:00:00 -0700
Subject: [PATCH] fix location in tfm.c that could result in potential cache
 attack

---
 wolfcrypt/src/tfm.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/wolfcrypt/src/tfm.c b/wolfcrypt/src/tfm.c
index 499c6a6c0..cfb647fb1 100644
--- a/wolfcrypt/src/tfm.c
+++ b/wolfcrypt/src/tfm.c
@@ -480,12 +480,11 @@ void fp_mul_comba(fp_int *A, fp_int *B, fp_int *C)
       pa = FP_SIZE-1;
    }
 
-   if (A == C || B == C) {
+   /* Always take branch to use tmp variable. This avoids a cache attack for
+    * determining if C equals A */
+   if (1) {
       fp_init(&tmp);
       dst = &tmp;
-   } else {
-      fp_zero(C);
-      dst = C;
    }
 
    for (ix = 0; ix < pa; ix++) {