proxy-tamper

A HTTP proxy library for node.js that allows for selective requests to be tampered.

Installation

Either install via npm:

npm install proxy-tamper

Or via a git clone:

cd node_modules
git clone git://github.com/tsyd/proxy-tamper.git
npm link

Example

The following example demonstrates proxy-tamper abilities:

var proxy = require('proxy-tamper').start({port: 8080});

// block all URLs that contain 'block' in them
proxy.tamper(/block/, 'This content is blocked!');

// disallow Google 
proxy.tamper(/google/, function (request) {
  request.url = request.url.replace(/google/g, 'bing'); 
});

// replace all instances of 'Apple' with 'Orange' in TechCrunch articles
proxy.tamper(/techcrunch.com.*\/$/, function (request) {
  // gzip encoding is not supported when tampering the body
  delete request.headers['accept-encoding'];

  request.onResponse(function (response) {
    // tamper the body
    response.body = response.body.replace(/Apple/g, 'Orange');
    response.headers['server'] = 'proxy-tamper 1337';

    // complete the response
    response.complete();
  }); 
});

To tamper HTTP requests with a string or result of a function call, specify a regular expression for the URL and a string or function:

proxy.tamper(/block/, 'This content is blocked!');

The response body of all URLs that contain block in them will be `This content is blocked!'.

It is possible to manipulate the original request before it's executed over the proxy. The request object has access to request.url, request.headers, and request.method:

proxy.tamper(/google/, function (request) {
  request.url = request.url.replace(/google/g, 'bing'); 
});

It is also possible to modify the response before proxying it back to the original request by specifying an onResponse handler:

// replace all instances of 'Apple' with 'Orange' in TechCrunch articles
proxy.tamper(/techcrunch.com.*\/$/, function (request) {
  // gzip encoding is not supported when tampering the body
  delete request.headers['accept-encoding'];

  request.onResponse(function (response) {
    // tamper the body
    response.body = response.body.replace(/Apple/g, 'Orange');
    response.headers['server'] = 'proxy-tamper 1337';

    // complete the response
    response.complete();
  }); 
});

The onResponse handler has read and write access to a subset of the http.ClientResponse response object, namely: response.headers, response.statusCode, and response.url. The onResponse handler may also modfiy the string representation of the response body by accessing response.body.

Usage

To test the example application, simply run:

node example.js

Then set your browser to use 127.0.0.1:8080 as the HTTP proxy, and visit the following URLs:

• http://google.com/block/
• http://techcrunch.com/tag/apple/

License

(The MIT License)

Copyright (c) 2011 Thomas Sydorowski

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the 'Software'), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED 'AS IS', WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.