From a3d46bee324c8742bafda43e66bfc65475ec6fc1 Mon Sep 17 00:00:00 2001
From: Sean Parkinson <sean@wolfssl.com>
Date: Tue, 30 Nov 2021 09:46:11 +1000
Subject: [PATCH] SP math all: div handling of length of dividend

Fail when dividend is maximum size as we may be shifting left and
overflow when divisor is not on a word boundary.
---
 wolfcrypt/src/sp_int.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/wolfcrypt/src/sp_int.c b/wolfcrypt/src/sp_int.c
index 049759827..fce360d13 100644
--- a/wolfcrypt/src/sp_int.c
+++ b/wolfcrypt/src/sp_int.c
@@ -4614,6 +4614,10 @@ int sp_div(sp_int* a, sp_int* d, sp_int* r, sp_int* rem)
     if ((err == MP_OKAY) && (rem != NULL) && (rem->size < a->used + 1)) {
         err = MP_VAL;
     }
+    /* May need to shift number being divided left into a new word. */
+    if ((err == MP_OKAY) && (a->used == SP_INT_DIGITS)) {
+        err = MP_VAL;
+    }
 
     #if 0
     if (err == MP_OKAY) {