Check hash of firmware

Author: qistoph

src/AsyncElegantOTA.h

@@ -91,6 +91,15 @@ class AsyncElegantOtaClass{
                 }
 
                 if (!index) {
+                    if(request->hasParam("MD5", true)) {
+                        return request->send(400, "text/plain", "MD5 parameter missing");
+                    }
+
+                    const String sentMd5 = request->getParam("MD5", true)->value();
+                    if(!Update.setMD5(sentMd5.c_str())) {
+                        return request->send(400, "text/plain", "MD5 parameter invalid");
+                    }
+
                     #if defined(ESP8266)
                         int cmd = (filename == "filesystem") ? U_FS : U_FLASH;
                         Update.runAsync(true);