middlefiddle v0.3.3
MiddleFiddle
MiddleFiddle is an outbound local proxy which lets to modify your outbound request and responses via Connect middleware. It support HTTP and HTTPS, the latter through a hijacking of the request with locally generated SSL certs.
Installtion
npm install -g middlefiddle
Installation via Github
# Depends on Node 0.6.x
git clone git://github.com/mdp/middlefiddle.git
cd middlefiddle
npm install
npm link #If you want to use it globally
Usage
Basic usage
By default middlefiddle will start logging traffic and modifying requests based on site specific middleware found in '.middlefiddle/sites'
You can find an example in .middlefiddle/sites
# Start middlefiddle with default options
middlefiddle
# Proxy will be at port 8080
# and the web logger will be open at port 8411
Using the logger
middlefiddle logger
# Now open http://localhost:8411
# Only log for a certain URL
middlefiddle logger --url google.com
# Only log certain statuses
middlefiddle logger --status 404
# Only log responses containing text
middlefiddle logger --grep "setTimeout"
# Also work with regex
middlefiddle logger -r --grep "Mark(Percival)?"
# And case insensitive
middlefiddle logger -ri --grep "m@mdp\.im"
Site specific middleware
MiddleFiddle can alter requests based on the host name. You'll find some examples in .middlefiddle/sites
Simple add the middleware to your ~/.middlefiddle/sites directory, with the appropriate hostname. For example, ~/.middlefiddle/sites/github.com.coffee' would get injected on any request to github.com
MiddleFiddle middleware is connect compatible. Anything you can do with Connect, you can do with middlefiddle middleware.
Examples
Saving any mp3's from a site
For example, lets say you want to save all the streamed mp3's from Soundcloud.com
Found in soundcloud.com.coffee
fs = require 'fs'
module.exports = (Mf) ->
(req, res, next) ->
res.on 'body', ->
if res.headers["content-type"] == 'audio/mpeg'
fileName = req.path.replace(/^[a-zA-Z]/, '').split('.')[0]
path = "#{process.env["HOME"]}/Downloads/soundcloud#{fileName}.mp3"
fs.writeFile path, res.body, ->
console.log "Saved #{res.body.length} bytes to #{path}"
next()
Find and replace any text
In this case we used the MiddleFiddle helper 'replace'
Found in github.com.coffee
module.exports = (Mf) ->
replacement = (string, req, res) ->
contentType = res.headers['content-type'] || ''
if contentType.search(/html/) >= 0
string.replace(/repositories/ig, "suppositories")
else
false
return Mf.replace(replacement)
Modify outbound request headers
Here we are going to change the user agent to GoogleBot
Found in ft.com.coffee
module.exports = (Mf) ->
# I'm the Google, let me in!
(req, res, next) ->
req.headers['user-agent'] = "GoogleBot"
next()
Web Logging
By default MiddleFiddle logs all outbound traffic to a web based logger on localhost:8411
Configuration
MiddleFiddle looks for a .middlefiddle directory in the current working directory, or at ~/.middlefiddle.
Inside you'll find a config.coffee file, https certs, and a sites directory.
You'll need to add the https certs to you keychain if you want to avoid the browser warning. The certs are generated on the first launch of middlefiddle and are therefor unique to each machine.
HTTPS Hijacking
When an HTTPS request is first seen, MiddleFiddle generates a certificate for that domain, signs it with it's own generated root cert, and stores the cert for future use in ~/.middlefiddle/certs
In order to make this look legit to your browser, you'll need to add the generated root cert in ~/.middlefiddle/ca.crt to your keychain. This cert is auto generated just for your machine, so you won't be compromising your browser security.
Things to note
Connect typically doesn't have a simple way to hijack downstream responses, so middlefiddle emits events on the response along with writing to the stream.
You've also got a couple helper properties:
- req.fullUrl #=> The full requested URL, including the schema
- req.isSecure #=> Did it come via SSL?
Testing
Tests can be run from within the repo
npm install
npm test
TODO
- Clean up cert generation
- Expand logging
- Add more middleware
Want to contribute
Criticism is gladly accepted as long as it's in the form of a pull request.
Development
MiddleFiddle is written in CoffeeScript. It's set
up with a Cakefile for building files in src/
to lib/
and running
tests with nodeunit. There's also a docs
task that generates Docco
documentation from the source in src/
.
Released under the MIT license.
Mark Percival m@mdp.im