Intro

transparent-proxy extends the native net.createServer and it acts as a real transparent http-proxy.

This module was built on top of TCP-level to avoid header-stripping problem of nodejs http(s)-modules.

It allows to upstream client-request dynamically to other proxies, or to certain iFace, to spoof requests and more...

It supports Basic Proxy-Authentication.

Quick Start

Install

``bash
npm i transparent-proxy
`

Use

`javascript
const ProxyServer = require('transparent-proxy');

//init ProxyServer
const server = new ProxyServer();

//starting server on port 8080
server.listen(8080, '0.0.0.0', function () {
console.log('TCP-Proxy-Server started!', server.address());
});
`

Options Object

| Param | Type | Description |
| ------ | ------------------- | ------------ |
|options | Object | The options object. |
|[options.auth] | Function | Activate/Handle Proxy-Authentication. Returns or solves to Boolean. |
|[options.upstream] | Function | The proxy to be used to upstreaming requests. Returns String. |
|[options.tcpOutgoingAddress] | Function | The localAddress to use while sending requests. Returns String |
|[options.injectData] | Function | The edited data to upstream. Returns Buffer or string |
|[options.injectResponse] | Function | The edited response to return to connected client. Returns Buffer or string |
|[options.keys] | Function | The keys to use while handshake. It will work only if intercept is true. Returns Object or false |
|[options.verbose] | Boolean | Activate verbose mode. |
|[options.intercept] | Boolean | Activate interception of encrypted communications. False as default. |
|[options.logger] | Logger | Must be an object implementing log(args[]) and error(args[]). Defaults to the inbuilt logger writing to the console if verbose is true.|
|[options.handleSni] | Function | Pass SNICallback to be added to the server. See SNICallback tls.createServer options |

upstream, tcpOutgoingAddress, injectData & injectResponse Options

The options are functions having follow parameters:

| Param | Type | Description |
| ------ | ------------------- | ------------ |
|data | Buffer | The received data. |
|session | Session | Object containing info/data about Tunnel |


- upstream-Function need to return/resolve a String with format -> IP:PORT or USER:PWD@IP:PORT of used http-proxy. If 'localhost' is returned/resolved, then the host-self will be used as proxy.
- tcpOutgoingAddress-Function need to return a String with format -> IP.

Note: These functions will be executed before first tcp-socket-connection is established.


- injectData-Function need to return a String or buffer for the new spoofed data. This will be upstreamed as request.
- injectResponse-Function need to return a String or buffer for the new received data.

Upstream to other proxies

If you don't want to use the host of active instance self, then you need to upstream connections to another http-proxy.
This can be done with upstream attribute.

`javascript
const ProxyServer = require('transparent-proxy');

const server = new ProxyServer({
upstream: function () {
return 'x.x.x.x:3128'; // upstream to other proxy
}
});

//starting server on port 8080
server.listen(8080, '0.0.0.0', function () {
console.log('TCP-Proxy-Server started!', server.address());
});
`

You can also use an async function to upstream your requests:

`javascript
const ProxyServer = require('transparent-proxy');

const server = new ProxyServer({
upstream: async function () {
//make some async task before
return 'x.x.x.x:3128'; // upstream to other proxy
}
});

//starting server on port 8080
server.listen(8080, '0.0.0.0', function () {
console.log('TCP-Proxy-Server started!', server.address());
});
`

The auth Function

This activate basic authorization mechanism.
The Auth-function will be executed while handling Proxy-Authentications.



| Param | Type | Description |
| ------ | ------------------- | ------------ |
|username | String | The client username. |
|password | String | The client password |
|session | Session | Object containing info/data about Tunnel |

Note: It needs to return True/False or a Promise that resolves to boolean (isAuthenticated).


`javascript
const ProxyServer = require('transparent-proxy');

const server = new ProxyServer({
auth: function (username, password) {
return username === 'bar' && password === 'foo';
}
});

//starting server on port 8080
server.listen(8080, '0.0.0.0', function () {
console.log('TCP-Proxy-Server started!', server.address());
});
`

Interception

The callbacks injectData & injectResponse could be used to intercept/spoof communication.
These functions are executed with the data and session arguments.

#### Intercepting HTTPS

The boolean attribute intercept allows to break SSL-Communication between Source & Destination.

This will activate Security-Alarm by most used browsers.


`javascript
const switchWith = 'My Super Spoofed UA!';
const server = new ProxyServer({
intercept: true,
verbose: true,
injectData: (data, session) => {
if (session.isHttps) {
const modifiedData = data.toString()
.replace(session.request.headers['user-agent'], switchWith); //replacing UA-Header-Value

return Buffer.from(modifiedData);
}
return data;
}
});
`

`bash
curl -x localhost:8080 -k http://ifconfig.io/ua
curl/7.83.1

curl -x localhost:8080 -k https://ifconfig.me/ua
My Super Spoofed UA!
`

The keys Function

This function will work only if intercept is set to true.

If activated needs to return an Object {key:'String', cert:'String'} like native tls_connect_options.key & tls_connect_options.cert or false statement.

If no object is returned, then default keys will be used to update communication.


| Param | Type | Description |
| ------ | ------------------- | ------------ |
|session | Session | Object containing info/data about Tunnel |

Note: This function will be executed before TLS-Handshake.

The handleSNI Function

If passed a function, the proxy will call it to obtain the TLS secure context instead of using keys.

From tls.createServer
Two arguments will be passed when called: servername and callback. callback is an error-first callback that takes two optional arguments: error and ctx. ctx, if provided, is a SecureContext instance. tls.createSecureContext() can be used to get a proper SecureContext. If callback is called with a falsy ctx argument, the default secure context of the server will be used.

#### Session-Instance

The Session-Instance is an Object containing info/data about Tunnel.
It has following useful attributes and methods:

- isHttps - Is session encrypted.
- request - The Request-Object containing info about current request.
- response - The Response-Object containing info about current response.

- getTunnelStats() - Get Stats for this tunnel
- getId() - Get Own ID-Session
- isAuthenticated() - Is the session authenticated by user or not.

.getBridgedConnections()

`javascript
const ProxyServer = require('transparent-proxy');
const server = new ProxyServer();

//starting server on port 8080
server.listen(8080, '0.0.0.0', function () {
console.log('Proxy-Server started!', server.address());
});

setInterval(function showOpenSockets() {
const bridgedConnections = server.getBridgedConnections();
console.log([new Date()], 'OPEN =>', Object.keys(bridgedConnections).length)
}, 2000);
`

Examples

This example upstreams only requests for ifconfig.me to another proxy, for all other requests will be used localhost.

`javascript
const ProxyServer = require('transparent-proxy');

const server = new ProxyServer({
upstream: function (data, session) {
if (~(data.toString().indexOf('ifconfig.me'))) {
return 'x.x.x.x:3128'; // upstream to other proxy
} else {
return 'localhost'; //upstream to localhost
}
},
});

//starting server on port 8080
server.listen(8080, '0.0.0.0', function () {
console.log('TCP-Proxy-Server started!', server.address());
});
`

Testing with curl:

`bash
curl -x 127.0.0.1:8080 https://ifconfig.me
x.x.x.x
`
`bash
curl -x 127.0.0.1:8080 https://ifconfig.co
y.y.y.y
``

For more examples look here.