simple https proxy on golang

https_socket_proxy.go

package main

import (
	"bufio"
	"crypto/tls"
	"fmt"
	"io"
	"log"
	"net"
	"strings"
)

// generate keys
// openssl req -x509 -newkey rsa:4096 -keyout server.key -out server.crt -days 365 -nodes

func main() {
	// Загрузка сертификата и ключа
	cert, err := tls.LoadX509KeyPair("server.crt", "server.key")
	if err != nil {
		log.Fatal("Failed to load certificate:", err)
	}

	// Конфигурация TLS
	config := &tls.Config{
		Certificates: []tls.Certificate{cert},
	}

	// Запуск HTTPS сервера
	listener, err := tls.Listen("tcp", ":8443", config)
	if err != nil {
		log.Fatal("Failed to start HTTPS server:", err)
	}
	defer listener.Close()

	fmt.Println("HTTPS Proxy server listening on :8443")

	for {
		conn, err := listener.Accept()
		if err != nil {
			log.Println("Failed to accept connection:", err)
			continue
		}
		go handleConnection(conn)
	}
}

func handleConnection(clientConn net.Conn) {
	defer clientConn.Close()

	reader := bufio.NewReader(clientConn)
	requestLine, err := reader.ReadString('\n')
	if err != nil {
		log.Println("Error reading request:", err)
		return
	}

	parts := strings.Split(strings.TrimSpace(requestLine), " ")
	if len(parts) != 3 {
		log.Println("Invalid request line:", requestLine)
		return
	}

	method, host, version := parts[0], parts[1], parts[2]

	if method == "CONNECT" {
		handleHTTPS(clientConn, host)
	} else {
		handleHTTP(clientConn, method, host, version, reader)
	}
}

func handleHTTP(clientConn net.Conn, method, host, version string, reader *bufio.Reader) {
	if !strings.HasPrefix(host, "http://") {
		host = "http://" + host
	}

	targetConn, err := net.Dial("tcp", host[7:])
	if err != nil {
		log.Println("Failed to connect to target:", err)
		return
	}
	defer targetConn.Close()

	fmt.Fprintf(targetConn, "%s %s %s\r\n", method, host, version)
	go io.Copy(targetConn, reader)
	io.Copy(clientConn, targetConn)
}

func handleHTTPS(clientConn net.Conn, host string) {
	targetConn, err := net.Dial("tcp", host)
	if err != nil {
		log.Println("Failed to connect to target:", err)
		clientConn.Write([]byte("HTTP/1.1 502 Bad Gateway\r\n\r\n"))
		return
	}
	defer targetConn.Close()

	clientConn.Write([]byte("HTTP/1.1 200 Connection Established\r\n\r\n"))

	go io.Copy(targetConn, clientConn)
	io.Copy(clientConn, targetConn)
}