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app.js

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+
+const secureSend = require('./secureSendClient.js');
+
+const options = {
+    hmacKey: 'supersecure',
+    hashByteLength: 32,
+    randDataLength: 100,
+    port: 777,
+    ip: '192.168.0.6',
+
+    onConnect: () => {
+        console.log('Connected');
+    }
+}
+
+const cmds = {
+    getGateState:{
+        cmd: 0,
+        responses: [0x00, 0x01, 0x02] /* 0: Closed  1: Open  2: Middle */
+    },
+    switchGate: {
+        cmd: 1,
+        responses: [0x00] /* 0: Cmd received */
+    },
+    switchLight: {
+        cmd: 2,
+        responses: [0x00, 0x01] /* 0: now closed  1: now Open */
+    }
+};
+
+secureSend(options, cmds.switchGate)
+    .then(res => {
+        console.log('The response ->');
+        console.log(res);
+    })
+    .catch(err => {
+        console.log('Catched Error ->');
+        console.log(err);
+    });
+
+setTimeout(()=>{},6000);

secureSendClient.js

@@ -0,0 +1,118 @@
+
+const net = require('net');
+var crypto = require('crypto');
+
+
+function secureSend(options, cmdSend, cb){
+    const promise = new Promise(function(resolve, reject){
+        
+        let reqHash = crypto.createHmac('sha256', options.hmacKey);
+        reqHash.setEncoding('binary');
+        
+        let resHash = Buffer.allocUnsafe(options.hashByteLength);
+        let gotBytes = Buffer.allocUnsafe(options.randDataLength);
+        let gotBytesNum = 0;
+
+        let res = null;    // The final analyzed response
+
+        var client = new net.Socket();
+        client.connect(options.port, options.ip, ()=>{
+            gotBytesNum = 0;
+            if(typeof options.onConnect === 'function') options.onConnect();
+            client.write('X'); //necessary for the arduino ethernet library
+        });
+
+        client.on('error', (err) => {
+            reject(err);
+        });
+
+        client.on('close', function() {
+            if(res === null) reject(new Error('Connection closed before the response was sent.'));
+            else resolve(res);
+        });
+
+        client.on('data', (data) => {
+            gotBytesNum += data.length;
+
+            if(gotBytesNum <= options.randDataLength){
+                reqHash.update(Buffer.from(data), 'binary');
+                for(i=0; i<data.length; i++){
+                    gotBytes[gotBytesNum - data.length + i] = data[i];
+                }
+            }
+
+            if(gotBytesNum == options.randDataLength){
+
+                reqHash.update(Buffer.from([cmdSend.cmd]), 'binary');
+                reqHash.end(); // very important! You cannot read from the stream until you have called end()
+
+                var sha256sum = reqHash.read();
+                client.write(sha256sum, 'binary');
+                //printHash(sha256sum);
+            }
+
+            if(gotBytesNum > options.randDataLength){
+                if (gotBytesNum > (options.randDataLength + options.hashByteLength)) reject(new Error('Server returned more bytes than expeced'));
+                
+                for(i=0; i<data.length; i++)
+                    resHash[gotBytesNum - options.randDataLength - data.length + i] = data[i];
+
+                if (gotBytesNum == (options.randDataLength + options.hashByteLength)){
+                    res = analyzeResponse(options.hmacKey, cmdSend, gotBytes, resHash);
+                    client.destroy(); // kill client after server's response       
+                }
+            }
+        });
+
+    });
+
+    if (cb && typeof cb == 'function'){
+        promise.then(cb.bind(null, null), cb);
+    }
+    return promise;
+}
+
+
+function analyzeResponse(hmacKey, cmdSend, gotBytes, resHash){
+    for(i=0; i<cmdSend.responses.length; i++){
+        let testHash = Buffer.from(getHash(gotBytes, hmacKey, [cmdSend.responses[i]]), 'binary');
+        if (hashesAreTheSame(resHash, testHash)){
+            return cmdSend.responses[i];
+        }
+    }
+    return undefined;
+}
+
+function getHash(data, key, additionalData){
+    let checkHash = crypto.createHmac('sha256', key);
+    checkHash.setEncoding('binary');
+    checkHash.update(data, 'binary');
+
+    checkHash.update(Buffer.from(additionalData));
+
+    checkHash.end();
+    return checkHash.read();
+}
+
+function hashesAreTheSame(hash1, hash2){
+    if (hash1.length != hash2.length) return false;
+    for (j=0; j<hash1.length; j++) if(hash1[j] != hash2[j]) return false;
+    return true;
+}
+
+// function printHash(hash){
+//     let str = '';
+//     for (i=0; i<hash.length; i++)
+//         str += hash.charCodeAt(i).toString(16);
+//     console.log(str);  
+// }
+
+// function toHexString(byteArray) {
+//     return Array.from(byteArray, function(byte) {
+//         return ('0' + (byte & 0xFF).toString(16)).slice(-2);
+//     }).join('');
+// }
+
+
+module.exports = secureSend;
+