Node.js tlsSocket.getFinished() Method

The tlsSocket.getFinished() is an inbuilt application programming interface of class TLSSocket within tls module which is used to return a latest Finished message that has been sent to the socket as part of a SSL/TLS handshake, or undefined if no Finished message has been sent yet.

Syntax:

const tlsSocket.getFinished()

Parameters: This method does not accept any parameter.

Return Value: This method returns an buffer object containing message digests of the complete handshake. 

How to generate private key and public certificate?

1. Private key: Open notepad and copy paste the following key:

   -----BEGIN RSA PRIVATE KEY-----
   MIICXQIBAAKBgQC38R9wXcUbhOd44FavgmE5R3K4JeYOHLnI7dUq1B8/Gv7l3SOg
   JKef/m9gM1KvUx951mapXGtcWgwB08J3vUE2YOZ4tWJArrVZES0BI/RmFAyhQFP5
   HcWl3LSM9LRihP98F33oIkKaCxA5LxOrkgpV4HrUzIKTABDYah7RPex1WQIDAQAB
   AoGBAIXR71xxa9gUfc5L7+TqBs+EMmrUb6Vusp8CoGXzQvRHMJCMrMFySV0131Nu
   o0YYRDsAh1nJefYLMNcXd1BjqI+qY8IeRsxaY+9CB2KKGVVDO2uLdurdC2ZdlWXT
   Vwr3dDoyR0trnXJMmH2ijTeO6bush8HuXxvxJBjvEllM5QYxAkEA3jwny9JP+RFu
   0rkqPBe/wi5pXpPl7PUtdNAGrh6S5958wUoR4f9bvwmTBv1nQzExKWu4EIp+7vjJ
   fBeRZhnBvQJBANPjjge8418PS9zAFyKlITq6cxmM4gOWeveQZwXVNvav0NH+OKdQ
   sZnnDiG26JWmnD/B8Audu97LcxjxcWI8Jc0CQEYA5PhLU229lA9EzI0JXhoozIBC
   TlcKFDuLm88VSmlHqDyqvF9YNOpEdc/p2rFLuZS2ndB4D+vu6mjwc5iZ3HECQCxy
   GBHRclQ3Ti9w76lpv+2kvI4IekRMZWDWnnWfwta+DGxwCgw2pfpleBZkWqdBepb5
   JFQbcxQJ0wvRYXo8qaUCQQCgTvWswBj6OTP7LTvBlU1teAN2Lnrk/N5AYHZIXW6m
   nUG9lYvH7DztWDTioXMrruPF7bdXfZOVJD8t0I4OUzvC
   -----END RSA PRIVATE KEY-----

   Save file as private-key.pem

2. Public certificate: Open notepad and copy paste the following key:

   -----BEGIN CERTIFICATE-----
   MIICfzCCAegCCQDxxeXw914Y2DANBgkqhkiG9w0BAQsFADCBgzELMAkGA1UEBhMC
   SU4xEzARBgNVBAgMCldlc3RiZW5nYWwxEDAOBgNVBAcMB0tvbGthdGExFDASBgNV
   BAoMC1BhbmNvLCBJbmMuMRUwEwYDVQQDDAxSb2hpdCBQcmFzYWQxIDAeBgkqhkiG
   9w0BCQEWEXJvZm9mb2ZAZ21haWwuY29tMB4XDTIwMDkwOTA1NTExN1oXDTIwMTAw
   OTA1NTExN1owgYMxCzAJBgNVBAYTAklOMRMwEQYDVQQIDApXZXN0YmVuZ2FsMRAw
   DgYDVQQHDAdLb2xrYXRhMRQwEgYDVQQKDAtQYW5jbywgSW5jLjEVMBMGA1UEAwwM
   Um9oaXQgUHJhc2FkMSAwHgYJKoZIhvcNAQkBFhFyb2ZvZm9mQGdtYWlsLmNvbTCB
   nzANBgkqhkiG9w0BAQEFAAOBjQAwgYkCgYEAt/EfcF3FG4TneOBWr4JhOUdyuCXm
   Dhy5yO3VKtQfPxr+5d0joCSnn/5vYDNSr1MfedZmqVxrXFoMAdPCd71BNmDmeLVi
   QK61WREtASP0ZhQMoUBT+R3Fpdy0jPS0YoT/fBd96CJCmgsQOS8Tq5IKVeB61MyC
   kwAQ2Goe0T3sdVkCAwEAATANBgkqhkiG9w0BAQsFAAOBgQATe6ixdAjoV7BSHgRX
   bXM2+IZLq8kq3s7ck0EZrRVhsivutcaZwDXRCCinB+OlPedbzXwNZGvVX0nwPYHG
   BfiXwdiuZeVJ88ni6Fm6RhoPtu2QF1UExfBvSXuMBgR+evp+e3QadNpGx6Ppl1aC
   hWF6W2H9+MAlU7yvtmCQQuZmfQ==
   -----END CERTIFICATE-----

   Save file as public-cert.pem

Example 1: Filename: index.js

// Node.js program to demonstrate the
// tlsSocket.getFinished() method

var tls = require('tls'),
    fs = require('fs'),

// Port and host address for server
PORT = 1337,
HOST = '127.0.0.1',
value =null;

// Private key and public certificate for access
var options = {
  key: fs.readFileSync('private-key.pem'),
  cert: fs.readFileSync('public-cert.pem'),
  rejectUnauthorized: false
};

// Creating and initializing server
var server = tls.createServer(options, function(socket) {

  // Print the data that we received
  socket.on('data', function(data) {
     console.log('\nReceived: %s ',
     data.toString().replace(/(\n)/gm, ""));
  });

  // Stopping the server
  // by using the close() method
  server.close(() => {
     console.log("Server closed successfully");
  });
});

// Start listening on a specific port and address
// by using listen() method
server.listen(PORT, HOST, function() {
  console.log("I'm listening at %s, on port %s", HOST, PORT);
});

// Creating and initializing client
var client = tls.connect(PORT, HOST, options, function() {

  // Getting finished message digest
  // by using tlsSocket.getFinished() method
  value = client.getFinished();

  client.write("Finisher message : " + value.toJSON().data);

  client.end(() => {
     console.log("Client closed successfully");
  });
});

Run the index.js file using the following command:

node index.js

Output:

I’m listening at 127.0.0.1, on port 1337
Client closed successfully

Received: Finisher message : 94, 70, 57, 175, 148, 249, 68, 105, 31, 68, 140, 250, 69, 62, 43, 163, 23, 102, 77, 110, 31, 208, 216, 84, 58, 52, 150, 169, 151, 237, 253, 44, 21, 240, 151, 114, 100, 227, 211, 77, 192, 144, 163, 118, 199, 174, 88, 190
Server closed successfully

Example 2: Filename: index.js

// Node.js program to demonstrate the
// tlsSocket.getFinished()  API
var tls = require('tls'),
    fs = require('fs'),

// Port and host address for server
PORT = 1337,
HOST = '127.0.0.1';

// Private key and public certificate for access
var options = {
  key: fs.readFileSync('private-key.pem'),
  cert: fs.readFileSync('public-cert.pem'),
  rejectUnauthorized: false
};

// Creating and initializing server
var server = tls.createServer(options, function(socket) {

  // Getting finished message digest
  // by using tlsSocket.getFinished() method
  value = socket.getFinished();

  socket.write("Finisher message : " + value.toJSON().data);

  // Stopping the server
  // by using the close() method
  server.close(() => {
    console.log("Server closed successfully")
  });
});

// Start listening on a specific port and address
// by using listen() method
server.listen(PORT, HOST, function() {
  console.log("I'm listening at %s, on port %s", HOST, PORT);
});

// Creating and initializing client
var client = tls.connect(PORT, HOST, options, function() {
   console.log("client is connected");
});

client.on("data", function(data) {

  console.log('Received: %s',
  data.toString().replace(/(\n)/gm, ""));

  // Close the connection after receiving the message
  client.end(() => {
    console.log("client closed successfully")
  });
});

Run the index.js file using the following command:

node index.js

Output:

I’m listening at 127.0.0.1, on port 1337
client is connected
Received: Finisher message : 154, 53, 171, 177, 191, 48, 163, 116, 36, 25, 186, 97, 168, 169, 65, 145, 207, 125, 254, 4, 245, 250, 159, 172, 216, 131, 25, 98, 45, 70, 209, 245, 162, 85, 97, 220, 178, 79, 106, 33, 13, 179, 182, 14, 186, 87, 46, 118
client closed successfully
Server closed successfully

Reference: https://nodejs.org/dist/latest-v12.x/docs/api/tls.html#tls_tlssocket_getfinished