Restore SHA256 via bearSSL

Loses 2KB of flash compared with 46aa5f6 but it's surely faster

Author: facchinm

src/tls/bearssl/dec32be.c

@@ -23,7 +23,7 @@
  */
 
 #include <AIoTC_Config.h>
-#ifdef BOARD_HAS_ECCX08
+#if defined(BOARD_HAS_ECCX08) || defined(BOARD_HAS_OFFLOADED_ECCX08)
 
 #include "inner.h"
 

src/tls/bearssl/enc32be.c

@@ -23,7 +23,7 @@
  */
 
 #include <AIoTC_Config.h>
-#ifdef BOARD_HAS_ECCX08
+#if defined(BOARD_HAS_ECCX08) || defined(BOARD_HAS_OFFLOADED_ECCX08)
 
 #include "inner.h"
 

src/tls/bearssl/sha2small.c

@@ -23,7 +23,7 @@
  */
 
 #include <AIoTC_Config.h>
-#ifdef BOARD_HAS_ECCX08
+#if defined(BOARD_HAS_ECCX08) || defined(BOARD_HAS_OFFLOADED_ECCX08)
 
 #include "inner.h"
 

src/tls/utility/SHA256.cpp

@@ -33,21 +33,15 @@ constexpr size_t SHA256::HASH_SIZE;
 
 void SHA256::begin()
 {
-  spare_len = 0;
-  ECCX08.beginSHA256();
+  br_sha256_init(&_ctx);
 }
 
 void SHA256::update(uint8_t const * data, size_t const len)
 {
-  if (len == 64) {
-    ECCX08.updateSHA256(data);
-  } else {
-    memcpy(spare_buf, data, len);
-    spare_len = len;
-  }
+  br_sha256_update(&_ctx, data, len);
 }
 
 void SHA256::finalize(uint8_t * hash)
 {
-  ECCX08.endSHA256(spare_buf, spare_len, hash);
+  br_sha256_out(&_ctx, hash);
 }

src/tls/utility/SHA256.h

@@ -22,7 +22,7 @@
  * INCLUDE
  ******************************************************************************/
 
-#include "ArduinoECCX08.h"
+#include "../bearssl/bearssl_hash.h"
 
 /******************************************************************************
  * CLASS DECLARATION
@@ -40,8 +40,9 @@ class SHA256
   void finalize(uint8_t * hash);
 
 private:
-  uint8_t spare_buf[64];
-  size_t spare_len = 0;
+
+  br_sha256_context _ctx;
+
 };
 
 #endif /* ARDUINO_TLS_UTILITY_SHA256_H_ */