An HTTP proxy library for Go

Evan Cordell aa519ddbe4 WebSocket Support (#1) 3 years ago
certs c4fc26588b fixes #208, fixes #188, new CA for goproxy, with file that generates new ones 2 years ago
examples aa519ddbe4 WebSocket Support (#1) 2 months ago
ext b01cf922cb Add go.mod to ext/ pkg, run go mod tidy 8 months ago
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LICENSE 6b09cc8b07 by @ancientlore email request, adding LICENSE file 6 years ago
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actions.go 33be580eb8 fix minor typo in docs 5 years ago
all.bash ceca68a249 move regret buffer to package, improve 6 years ago
ca.pem e18c7b8430 Update the certificate files to match the contents of certs.go. 2 years ago
certs.go c4fc26588b fixes #208, fixes #188, new CA for goproxy, with file that generates new ones 2 years ago
chunked.go 623bafc29d gofmt 6 years ago
counterecryptor.go 6125c262ff Add support for signing with ecdsa keys 5 months ago
counterecryptor_test.go 6125c262ff Add support for signing with ecdsa keys 5 months ago
ctx.go 8a57b51e51 Switch CertStorage interface to single function 8 months ago
dispatcher.go b2f0a315f3 Allow SrcIpIs to accept multiple parameters. 4 years ago
doc.go f1e96bc0f4 Update return response example to follow current API 5 months ago
go.mod aaf7bbee77 Update module info (go mod tidy) 3 months ago
go.sum aaf7bbee77 Update module info (go mod tidy) 3 months ago
https.go aa519ddbe4 WebSocket Support (#1) 2 months ago
key.pem e18c7b8430 Update the certificate files to match the contents of certs.go. 2 years ago
logger.go 8c38eb266c added logger interface to allow usage of custom loggers 10 months ago
proxy.go aa519ddbe4 WebSocket Support (#1) 2 months ago
proxy_test.go 2719e7a533 Issue: #345 - fixes resp == nil: 5 months ago
responses.go 9b700f7984 Add status text based on status code on new HTTP responses 1 year ago
signer.go ecfe977594 Use random numbers for certificate serials 3 months ago
signer_test.go 6125c262ff Add support for signing with ecdsa keys 5 months ago
websocket.go aa519ddbe4 WebSocket Support (#1) 2 months ago

README.md

Introduction

GoDoc

Package goproxy provides a customizable HTTP proxy library for Go (golang),

It supports regular HTTP proxy, HTTPS through CONNECT, and "hijacking" HTTPS connection using "Man in the Middle" style attack.

The intent of the proxy is to be usable with reasonable amount of traffic, yet customizable and programmable.

The proxy itself is simply a net/http handler.

In order to use goproxy, one should set their browser to use goproxy as an HTTP proxy. Here is how you do that in Chrome and in Firefox.

For example, the URL you should use as proxy when running ./bin/basic is localhost:8080, as this is the default binding for the basic proxy.

Mailing List

New features will be discussed on the mailing list before their development.

Latest Stable Release

Get the latest goproxy from gopkg.in/elazarl/goproxy.v1.

Why not Fiddler2?

Fiddler is an excellent software with similar intent. However, Fiddler is not as customizable as goproxy intends to be. The main difference is, Fiddler is not intended to be used as a real proxy.

A possible use case that suits goproxy but not Fiddler, is gathering statistics on page load times for a certain website over a week. With goproxy you could ask all your users to set their proxy to a dedicated machine running a goproxy server. Fiddler is a GUI app not designed to be run like a server for multiple users.

A taste of goproxy

To get a taste of goproxy, a basic HTTP/HTTPS transparent proxy

package main

import (
    "github.com/elazarl/goproxy"
    "log"
    "net/http"
)

func main() {
    proxy := goproxy.NewProxyHttpServer()
    proxy.Verbose = true
    log.Fatal(http.ListenAndServe(":8080", proxy))
}

This line will add X-GoProxy: yxorPoG-X header to all requests sent through the proxy

proxy.OnRequest().DoFunc(
    func(r *http.Request,ctx *goproxy.ProxyCtx)(*http.Request,*http.Response) {
        r.Header.Set("X-GoProxy","yxorPoG-X")
        return r,nil
    })

DoFunc will process all incoming requests to the proxy. It will add a header to the request and return it. The proxy will send the modified request.

Note that we returned nil value as the response. Had we returned a response, goproxy would have discarded the request and sent the new response to the client.

In order to refuse connections to reddit at work time

proxy.OnRequest(goproxy.DstHostIs("www.reddit.com")).DoFunc(
    func(r *http.Request,ctx *goproxy.ProxyCtx)(*http.Request,*http.Response) {
        if h,_,_ := time.Now().Clock(); h >= 8 && h <= 17 {
            return r,goproxy.NewResponse(r,
                    goproxy.ContentTypeText,http.StatusForbidden,
                    "Don't waste your time!")
        }
        return r,nil
})

DstHostIs returns a ReqCondition, that is a function receiving a Request and returning a boolean. We will only process requests that match the condition. DstHostIs("www.reddit.com") will return a ReqCondition accepting only requests directed to "www.reddit.com".

DoFunc will receive a function that will preprocess the request. We can change the request, or return a response. If the time is between 8:00am and 17:00pm, we will reject the request, and return a precanned text response saying "do not waste your time".

See additional examples in the examples directory.

Type of handlers for manipulating connect/req/resp behavior

There are 3 kinds of useful handlers to manipulate the behavior, as follows:

// handler called after receiving HTTP CONNECT from the client, and before proxy establish connection 
// with destination host
httpsHandlers   []HttpsHandler
    
// handler called before proxy send HTTP request to destination host
reqHandlers     []ReqHandler 
    
// handler called after proxy receives HTTP Response from destination host, and before proxy forward 
// the Response to the client.
respHandlers    []RespHandler 

Depending on what you want to manipulate, the ways to add handlers to each handler list are:

// Add handlers to httpsHandlers 
proxy.OnRequest(Some ReqConditions).HandleConnect(YourHandlerFunc())

// Add handlers to reqHandlers
proxy.OnRequest(Some ReqConditions).Do(YourReqHandlerFunc())

// Add handlers to respHandlers
proxy.OnResponse(Some RespConditions).Do(YourRespHandlerFunc())

For example:

// This rejects the HTTPS request to *.reddit.com during HTTP CONNECT phase
proxy.OnRequest(goproxy.ReqHostMatches(regexp.MustCompile("reddit.*:443$"))).HandleConnect(goproxy.RejectConnect)

// This will NOT reject the HTTPS request with URL ending with gif, due to the fact that proxy 
// only got the URL.Hostname and URL.Port during the HTTP CONNECT phase if the scheme is HTTPS, which is
// quiet common these days.
proxy.OnRequest(goproxy.UrlMatches(regexp.MustCompile(`.*gif$`))).HandleConnect(goproxy.RejectConnect)

// The correct way to manipulate the HTTP request using URL.Path as condition is:
proxy.OnRequest(goproxy.UrlMatches(regexp.MustCompile(`.*gif$`))).Do(YourReqHandlerFunc())

What's New

  1. Ability to Hijack CONNECT requests. See the eavesdropper example
  2. Transparent proxy support for http/https including MITM certificate generation for TLS. See the transparent example.

License

I put the software temporarily under the Go-compatible BSD license. If this prevents someone from using the software, do let me know and I'll consider changing it.

At any rate, user feedback is very important for me, so I'll be delighted to know if you're using this package.

Beta Software

I've received positive feedback from a few people who use goproxy in production settings. I believe it is good enough for usage.

I'll try to keep reasonable backwards compatibility. In case of a major API change, I'll change the import path.