Proxy Server

A flexible HTTP/HTTPS and SOCKS5 proxy server for Go, supporting request filtering, upstream chaining, and configurable headers.

Features

• HTTP & HTTPS Support: Handles standard HTTP requests and HTTPS tunneling (via CONNECT).
• Configurable Headers:
  • Via Header: Optional Via header support (appends if exists).
• Request Filtering:
  • Multiple Filters: Chainable request filters using ApplyFilter.
  • Custom Logic: Easily implement things like X-Forwarded-For or custom header manipulation.
• Proxy Chaining:
  • Upstream Proxy: Forward requests to another proxy (HTTP forwarding and HTTPS tunneling).
  • Validation: Enforces valid http:// or https:// schemes for upstream URLs.
• SOCKS5 Support:
  • Upstream: Connect to socks5:// upstream proxies.
  • Server: Act as a SOCKS5 server using ServeSOCKS5. Supports transparent HTTP/HTTPS filtering over SOCKS5.
• Configuration:
  • Load from environment variables, .env files, or JSON.

Installation

go get github.com/patiee/proxy

Configuration

Configuration can be loaded from environment variables or a JSON file.

Environment Variables

Variable	Description	Required	Example
PROXY_PORT	Port to listen on	Yes	8080
PROXY_VIA	Value for Via header	No	proxy-server-v1.0.0 [IP_ADDRESS]:[PORT]
PROXY_UPSTREAM_URL	Upstream proxy URL (specific)	No	http://localhost:9090
PROXY_UPSTREAM_TIMEOUT	Upstream timeout in seconds	No	10

JSON Configuration

{
  "port": "8080",
  "via": "proxy-server-v1.0.0 [IP_ADDRESS]:[PORT]",
  "upstream": {
    "url": "http://localhost:9090",
    "timeout": 10
  }
}

Usage

Basic Usage

package main

import (
	"log"
	"net/http"

	"github.com/patiee/proxy/config"
	"github.com/patiee/proxy/proxy"
)

func main() {
	// Load config
	conf, err := config.LoadConfig() // or LoadConfigJson(bytes)
	if err != nil {
		log.Fatal(err)
	}

	// Create proxy server
	srv, err := server.NewProxyServer(conf.Port, conf.Via, conf.Upstream)
	if err != nil {
		log.Fatal(err)
	}

	log.Printf("Starting proxy on :%s", conf.Port)
	if err := http.ListenAndServe(":"+conf.Port, srv); err != nil {
		log.Fatal(err)
	}
}

Adding Filters (e.g., X-Forwarded-For)

X-Forwarded-For is not added by default. You can add it using a filter:

// Define filter
func xffFilter(r *http.Request) {
    // ... implementation ...
    r.Header.Set("X-Forwarded-For", clientIP)
}

// Apply filter
srv.ApplyFilter(xffFilter)

See examples/request-filter/main.go for a complete example.

Proxy Chaining

To chain to an upstream proxy, configure the upstream field. You can specify a URL string (defaults to 10s timeout) or an object:

{
  "port": "8082",
  "upstream": {
    "url": "http://localhost:8081",
    "timeout": 15
  }
}

See examples/proxychain/main.go for a complete example.

SOCKS5 Support

Upstream SOCKS5 Proxy chaining

To usage an upstream SOCKS5 proxy, set the upstream URL scheme to socks5://. You can also configure authentication and timeouts.

JSON Configuration:

{
  "port": "8080",
  "upstream": {
    "url": "socks5://internal-proxy:1080",
    "timeout": 10
  },
  "socks5": {
    "user": "myuser",
    "password": "mypassword",
    "timeout": 30
  }
}

Environment Variables:

• PROXY_UPSTREAM_URL: socks5://internal-proxy:1080
• PROXY_SOCKS5_USER: SOCKS5 username
• PROXY_SOCKS5_PASSWORD: SOCKS5 password
• PROXY_SOCKS5_TIMEOUT: SOCKS5 connection/handshake timeout in seconds (default: 10s)

SOCKS5 Server

The proxy can also act as a SOCKS5 server, accepting SOCKS5 connections from clients and forwarding them (potentially via another upstream proxy).

Configuration:

Simply configure the SOCKS5 credentials in the socks5 section (or via env vars). If configured, the server will accept SOCKS5 connections on the main port.

Note: The server auto-detects the protocol (HTTP/HTTPS/SOCKS5) on the same port.

{
  "port": "1080",
  "socks5": {
    "user": "server-user",
    "password": "server-password",
    "timeout": 30
  }
}

• timeout: Takes effect for the initial SOCKS5 handshake deadline.

Examples

Check the examples/ directory for ready-to-run examples:

• examples/request-filter: Demonstrates adding X-Forwarded-For.
• examples/proxychain: Demonstrates proxy chaining (HTTP/HTTPS).
• examples/socks5: Demonstrates SOCKS5 server usage.