From 0cf5761579b0217c0f0a4c3f2edfff8a96b0e56a Mon Sep 17 00:00:00 2001
From: Tom Pusateri <pusateri@bangj.com>
Date: Tue, 27 Mar 2018 16:06:14 -0400
Subject: [PATCH] Add TLS example and fix TCP example. (#31)

* Add TLS example and fix TCP buffer management.
Allow all examples to run from examples directory.

* Inspect response data decoding length, not request.

Simplify package require().
---
 examples/tcp.js | 36 +++++++++++++++++++++++------
 examples/tls.js | 61 +++++++++++++++++++++++++++++++++++++++++++++++++
 examples/udp.js |  9 ++++++--
 3 files changed, 97 insertions(+), 9 deletions(-)
 create mode 100644 examples/tls.js

diff --git a/examples/tcp.js b/examples/tcp.js
index 25e69c8..27d1fcc 100644
--- a/examples/tcp.js
+++ b/examples/tcp.js
@@ -1,11 +1,18 @@
 'use strict'
 
-const packet = require('./')
+const packet = require('..')
 const net = require('net')
 
-const buf = packet.streamEncode({
+var response = null
+var expected_length = 0
+
+function getRandomInt(min, max) {
+  return Math.floor(Math.random() * (max - min + 1)) + min;
+}
+
+const encodedPacket = packet.streamEncode({
   type: 'query',
-  id: 0xdead,
+  id: getRandomInt(1, 65534),
   flags: packet.RECURSION_DESIRED,
   questions: [{
     type: 'A',
@@ -16,13 +23,28 @@ const buf = packet.streamEncode({
 const client = new net.Socket()
 client.connect(53, '8.8.8.8', function () {
   console.log('Connected')
-  client.write(buf)
+  client.write(encodedPacket)
 })
 
 client.on('data', function (data) {
-  console.log('Received response')
-  console.log(packet.streamDecode(data))
-  client.destroy() // kill client after server's response
+  console.log('Received response: %d bytes', data.byteLength)
+  if (response == null) {
+    if (data.byteLength > 1) {
+      const plen = data.readUInt16BE(0)
+      expected_length = plen
+      if (plen < 12) {
+        throw new Error('below DNS minimum packet length')
+      }
+      response = Buffer.from(data)
+    }
+  } else {
+    response = Buffer.concat([response, data])
+  }
+
+  if (response.byteLength >= expected_length) {
+    console.log(packet.streamDecode(response))
+    client.destroy()
+  }
 })
 
 client.on('close', function () {
diff --git a/examples/tls.js b/examples/tls.js
new file mode 100644
index 0000000..58fc9d3
--- /dev/null
+++ b/examples/tls.js
@@ -0,0 +1,61 @@
+'use strict'
+
+const tls = require('tls')
+const packet = require('..')
+
+var response = null
+var expected_length = 0
+
+function getRandomInt(min, max) {
+  return Math.floor(Math.random() * (max - min + 1)) + min;
+}
+
+const encodedPacket = packet.streamEncode({
+  type: 'query',
+  id: getRandomInt(1, 65534),
+  flags: packet.RECURSION_DESIRED,
+  questions: [{
+    type: 'A',
+    name: 'google.com'
+  }]
+})
+
+const context = tls.createSecureContext({
+  secureProtocol: 'TLSv1_2_method'
+})
+
+const options = {
+  port: 853,
+  host: 'getdnsapi.net',
+  secureContext: context
+}
+
+const client = tls.connect(options, () => {
+  console.log('client connected')
+  client.write(encodedPacket)
+})
+
+client.on('data', function (data) {
+  console.log('Received response: %d bytes', data.byteLength)
+  if (response == null) {
+    if (data.byteLength > 1) {
+      const plen = data.readUInt16BE(0)
+      expected_length = plen
+      if (plen < 12) {
+        throw new Error('below DNS minimum packet length')
+      }
+      response = Buffer.from(data)
+    }
+  } else {
+    response = Buffer.concat([response, data])
+  }
+
+  if (response.byteLength >= expected_length) {
+    console.log(packet.streamDecode(response))
+    client.destroy()
+  }
+})
+
+client.on('end', () => {
+  console.log('Connection ended')
+})
diff --git a/examples/udp.js b/examples/udp.js
index 0b96397..dcf50f9 100644
--- a/examples/udp.js
+++ b/examples/udp.js
@@ -1,13 +1,17 @@
 'use strict'
 
-const packet = require('./')
+const packet = require('..')
 const dgram = require('dgram')
 
 const socket = dgram.createSocket('udp4')
 
+function getRandomInt(min, max) {
+  return Math.floor(Math.random() * (max - min + 1)) + min;
+}
+
 const buf = packet.encode({
   type: 'query',
-  id: 1,
+  id: getRandomInt(1, 65534),
   flags: packet.RECURSION_DESIRED,
   questions: [{
     type: 'A',
@@ -18,6 +22,7 @@ const buf = packet.encode({
 socket.on('message', function (message, rinfo) {
   console.log(rinfo)
   console.log(packet.decode(message)) // prints out a response from google dns
+  socket.close()
 })
 
 socket.send(buf, 0, buf.length, 53, '8.8.8.8')