- Generalize CryptoInterface.

- Add more HMAC and hash functions to CryptoInterface.

- Add MeshCryptoInterface as a holder of mesh specific crypto functionality.

- Rename broadcastMetadataDelimiter to metadataDelimiter in FloodingMesh since it is not just used for broadcasts, and to save some typing.

libraries/ESP8266WiFiMesh/src/MeshCryptoInterface.cpp

@@ -0,0 +1,42 @@
+/*
+ * Copyright (C) 2019 Anders Löfgren
+ *
+ * License (MIT license):
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+#include "MeshCryptoInterface.h"
+
+namespace MeshCryptoInterface 
+{
+  String createMeshHmac(const String &message, const void *hashKey, const size_t hashKeyLength, const size_t hmacLength)
+  {
+    return CryptoInterface::sha256Hmac(message, hashKey, hashKeyLength, hmacLength);
+  }
+
+  bool verifyMeshHmac(const String &message, const String &messageHmac, const uint8_t *hashKey, uint8_t hashKeyLength)
+  {
+    String generatedHmac = createMeshHmac(message, hashKey, hashKeyLength, messageHmac.length()/2); // We know that each HMAC byte should become 2 String characters due to uint8ArrayToHexString.
+    if(generatedHmac == messageHmac)
+      return true;
+    else
+      return false;
+  }
+}