proxychannel

Package proxychannel is a customizable HTTP proxy framework in Golang.

It accepts regular HTTP and CONNECT(for HTTPS) requests, and hijacks HTTPS connections as a "man in the middle"(only works under NormalMode).

The framework starts a proxy server(net/http server) and an extension manager, does something according to Delegate, and handles the graceful shutdown and logging of them. To use it, just offer some configuration, and implement the Delegate and Extensions that you need.

It has 2 modes(NormalMode and ConnPoolMode) for different scenarios and supports request-wise parent proxy selection.

Install

go get github.com/spritesprite/proxychannel

Conception & Features

• Delegate: An interface that defines some manipulation on requests or responses in defferent stages of the proxying process.

• Extension: An interface that provides certain functionality. All extensions are under extension manager's controll, and they basically serve for Delegate.

• Context: The information of each request, including the timestamps, response size, error type, user-defined data member, etc.

• NormalMode: proxychannel forwards requests to parent proxy, and returns whatever it gets from parent proxy back to requestor.

• ConnPoolMode: proxychannel chooses a TCP connection by given probability from the ConnPool, which is specified by p.delegate.GetConnPool(). If proxychannel fails to connect parent proxy or gets a response body in JSON format that has an "ErrType" of "PROXY_CHANNEL_INTERNAL_ERR"(when the parent proxy is also a proxychannel instance), it retries the request using another proxy chosen from ConnPool by given probability. The retry goes on until any parent proxy returns a 200 response code or every connection has been tried.

Usage

Get it Started

To start a basic HTTP proxy that listens on localhost:8080, try:

go run examples/main.go

Now check if the proxy works properly:

curl -x localhost:8080 https://www.google.com/
curl -x localhost:8080 http://www.google.com/

To try the "Man in the middle" functionality, install certification authority(CA) cert/mitm_proxy.crt first(if you happen to use CentOS, just use cert/centos_cert_install.sh to install CA), and run:

curl -x localhost:8080 https://www.google.com/ -H "MITM:Enabled" -v

The "Man in the middle" feature is functioning properly, if you could find in verbose output of curl something like: issuer: CN=go-mitm-proxy.

Customize your proxychannel

• Customize Delegate

According to the definition of Delegate, implement the methods you need.

type Delegate interface {
	GetExtensionManager() *ExtensionManager
	SetExtensionManager(*ExtensionManager)
	Connect(ctx *Context, rw http.ResponseWriter)
	Auth(ctx *Context, rw http.ResponseWriter)
	BeforeRequest(ctx *Context)
	BeforeResponse(ctx *Context, i interface{})
	ParentProxy(ctx *Context, i interface{}) (*url.URL, error)
	DuringResponse(ctx *Context, i interface{})
	Finish(ctx *Context, rw http.ResponseWriter)
	GetConnPool(ctx *Context) ([]randutil.Choice, error)
}

For example, this Finish method generates some logs for each request:

func (d *YourDelegate) Finish(ctx *proxychannel.Context, rw http.ResponseWriter) {
    GenerateLog(ctx) // generate log based on the information stored in ctx
}

• Customize Extension

To add an extension, just implement the Setup() and Cleanup() methods. For example, if your proxy needs some information stored, you may add a redis extension with Setup() building a connection pool to redis server and Cleanup() closing the pool.