HTTP MITM Proxy

HTTP Man In The Middle (MITM) Proxy written in node.js. Supports capturing and modifying the request and response data.

Example

This example will modify any search results coming from google and replace all the result titles with "Pwned!".

var Proxy = require('http-mitm-proxy');
var proxy = Proxy();

proxy.onError(function(ctx, err) {
  console.error('proxy error:', err);
});

proxy.onRequest(function(ctx, callback) {
  if (ctx.clientToProxyRequest.headers.host == 'www.google.com'
    && ctx.clientToProxyRequest.url.indexOf('/search') == 0) {
    ctx.use(Proxy.gunzip);

    ctx.onResponseData(function(ctx, chunk, callback) {
      chunk = new Buffer(chunk.toString().replace(/<h3.*?<\/h3>/g, '<h3>Pwned!</h3>'));
      return callback(null, chunk);
    });
  }
  return callback();
});

proxy.listen(8081);

SSL

Create a CA

cd ~/.http-mitm-proxy
openssl genrsa -out ca/ca.key 1024
openssl req -new -x509 -days 3650 -extensions v3_ca -keyout ca/cakey.pem -out ca/cacert.pem -config /etc/ssl/openssl.cnf
echo "02" > ca/cacert.srl

openssl genrsa -out www.google.com-key.pem 1024
openssl req -new -key www.google.com-key.pem -out www.google.com.pem
openssl x509 -req -days 3650 -CA ca/cacert.pem -CAkey ca/cakey.pem -in www.google.com.csr -out www.google.com-cert.pem

Import ca/cacert.pem into the browser.

API

Proxy

• listen
• onError
• onRequest
• onRequestData
• onResponse
• onResponseData
• use

Context

Context functions only effect the current request/response. For example you may only want to gunzip requests made to a particular host.

• onError
• onRequest
• onRequestData
• addRequestFilter
• onResponse
• onResponseData
• addResponseFilter
• use

## Proxy ### proxy.listen

Starts the proxy listening on the given port.

Arguments

• port - The port to listen on.

Example

proxy.listen(80);

### proxy.onError(fn) or ctx.onError(fn)

Adds a function to the list of functions to get called if an error occures.

Arguments

• fn(ctx, err) - The function to be called on an error.

Example

proxy.onError(function(ctx, err) {
  console.error('error in proxy for url:', ctx.clientToProxyRequest.url, err);
});

### proxy.onRequest(fn) or ctx.onRequest(fn)

Adds a function to get called at the beginning of a request.

Arguments

• fn(ctx, callback) - The function that gets called on each request.

Example

proxy.onRequest(function(ctx, callback) {
  console.log('REQUEST:', ctx.clientToProxyRequest.url);
  return callback();
});

### proxy.onRequestData(fn) or ctx.onRequestData(fn)

Adds a function to get called for each request data chunk (the body).

Arguments

• fn(ctx, chunk, callback) - The function that gets called for each data chunk.

Example

proxy.onRequestData(function(ctx, chunk, callback) {
  console.log('REQUEST DATA:', chunk.toString());
  return callback(null, chunk);
});

### proxy.onResponse(fn) or ctx.onResponse(fn)

Adds a function to get called at the beginning of the response.

Arguments

• fn(ctx, callback) - The function that gets called on each response.

Example

proxy.onResponse(function(ctx, callback) {
  console.log('BEGIN RESPONSE');
  return callback();
});

### proxy.onResponseData(fn) or ctx.onResponseData(fn)

Adds a function to get called for each response data chunk (the body).

Arguments

• fn(ctx, chunk, callback) - The function that gets called for each data chunk.

Example

proxy.onResponseData(function(ctx, chunk, callback) {
  console.log('RESPONSE DATA:', chunk.toString());
  return callback(null, chunk);
});

### proxy.use(module) or ctx.use(module)

Adds a module into the proxy. Modules encapsulate multiple life cycle processing functions into one object.

Arguments

• module - The module to add. Modules contain a hash of functions to add.

Example

proxy.use({
  onError: function(ctx, err) { },
  onRequest: function(ctx, callback) { return callback(); },
  onRequestData: function(ctx, chunk, callback) { return callback(null, chunk); },
  onResponse: function(ctx, callback) { return callback(); },
  onResponseData: function(ctx, chunk, callback) { return callback(null, chunk); }
});

## Context ### ctx.addRequestFilter(stream)

Adds a stream into the request body stream.

Arguments

• stream - The read/write stream to add in the request body stream.

Example

ctx.addRequestFilter(zlib.createGunzip());

### ctx.addResponseFilter(stream)

Adds a stream into the response body stream.

Arguments

• stream - The read/write stream to add in the response body stream.

Example

ctx.addResponseFilter(zlib.createGunzip());