From a7e585b63dff0836d5623d273e4a8196212f3332 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Moise=CC=81s=20Guimara=CC=83es?=
 <moisesguimaraesm@gmail.com>
Date: Fri, 17 Oct 2014 16:31:09 -0300
Subject: [PATCH] internal.c: refactoring BuildMessage to reduce stack usage:
 --- variable hmac moved to the heap (up to 64 bytes saved)

---
 src/internal.c | 19 +++++++++++++++++--
 1 file changed, 17 insertions(+), 2 deletions(-)

diff --git a/src/internal.c b/src/internal.c
index 4546c143d..4ccda921a 100644
--- a/src/internal.c
+++ b/src/internal.c
@@ -6928,11 +6928,26 @@ static int BuildMessage(CYASSL* ssl, byte* output, int outSz,
         if (ssl->specs.cipher_type != aead) {
 #ifdef HAVE_TRUNCATED_HMAC
             if (ssl->truncated_hmac && ssl->specs.hash_size > digestSz) {
-                byte hmac[MAX_DIGEST_SIZE];
+            #ifdef CYASSL_SMALL_STACK
+                byte* hmac = NULL;
+            #else
+                byte  hmac[MAX_DIGEST_SIZE];
+            #endif
+
+            #ifdef CYASSL_SMALL_STACK
+                hmac = (byte*)XMALLOC(MAX_DIGEST_SIZE, NULL,
+                                                       DYNAMIC_TYPE_TMP_BUFFER);
+                if (hmac == NULL)
+                    return MEMORY_E;
+            #endif
 
                 ret = ssl->hmac(ssl, hmac, output + headerSz + ivSz, inSz,
-                                type, 0);
+                                                                       type, 0);
                 XMEMCPY(output + idx, hmac, digestSz);
+
+            #ifdef CYASSL_SMALL_STACK
+                XFREE(hmac, NULL, DYNAMIC_TYPE_TMP_BUFFER);
+            #endif
             } else
 #endif
                 ret = ssl->hmac(ssl, output+idx, output + headerSz + ivSz, inSz,