TLS proxy example with both ends being clients

gistfile1.go

package main

import(
	"fmt"
	"net"
	"path/filepath"
	"crypto/tls"
	"time"
	"sync"
)

func main(){
	dir := "/tmp/certs"
	certFile1, keyFile1 := filepath.Join(dir, "cert1.pem"), filepath.Join(dir, "key1.pem")
	certFile2, keyFile2 := filepath.Join(dir, "cert2.pem"), filepath.Join(dir, "key2.pem")

	cert1, err := tls.LoadX509KeyPair(certFile1, keyFile1)
	if err != nil {
		panic(err)
	}
	cert2, err := tls.LoadX509KeyPair(certFile2, keyFile2)
	if err != nil {
		panic(err)
	}

	go relay()

	time.Sleep(time.Millisecond)

	c1, err := net.Dial("tcp", "127.0.0.1:2428")
	if err != nil {
		panic(err)
	}
	c2, err := net.Dial("tcp", "127.0.0.1:2428")
	if err != nil {
		panic(err)
	}

	c1c := &tls.Config{
		Certificates:           []tls.Certificate{cert1},
		NextProtos:             []string{"test"},
		ClientAuth:             tls.RequestClientCert,
		SessionTicketsDisabled: true,
		InsecureSkipVerify:     true,
		MinVersion:             tls.VersionTLS12,
		CipherSuites: []uint16{
			tls.TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256,
			tls.TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256,
			tls.TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA,
			tls.TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA,
			tls.TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA,
			tls.TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA,
		},
	}

	c2c := &tls.Config{
		Certificates:           []tls.Certificate{cert2},
		NextProtos:             []string{"test"},
		ClientAuth:             tls.RequestClientCert,
		SessionTicketsDisabled: true,
		InsecureSkipVerify:     true,
		MinVersion:             tls.VersionTLS12,
		CipherSuites: []uint16{
			tls.TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256,
			tls.TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256,
			tls.TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA,
			tls.TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA,
			tls.TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA,
			tls.TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA,
		},
	}

	t1 := tls.Client(c1, c1c)
	t2 := tls.Server(c2, c2c)

	wg := sync.WaitGroup{}

	wg.Add(2)

	go func() {
		err = t1.Handshake()
		if err != nil {
			panic(err)
		}
		wg.Done()
	}()

	go func() {
		err = t2.Handshake()
		if err != nil {
			panic(err)
		}
		wg.Done()
	}()

	wg.Wait()



	_, err = t1.Write([]byte("test"))
	if err != nil {
		panic(err)
	}

	buf := make([]byte, 1042)

	n, err := t2.Read(buf)
	if err != nil {
		panic(err)
	}

	fmt.Println("All good", string(buf[:n]))
}


func relay() {
	sock, err := net.Listen("tcp", ":2428")
	if err != nil {
		panic(err)
	}

	for {
		c1, err := sock.Accept()
		if err != nil {
			panic(err)
		}

		c2, err := sock.Accept()
		if err != nil {
			panic(err)
		}

		go proxy(c1, c2)
		go proxy(c2, c1)
	}
}

func proxy(c1, c2 net.Conn) {
	for {
		buf := make([]byte, 1024)
		n, err := c1.Read(buf)
		if err != nil {
			panic(err)
		}
		_, err = c2.Write(buf[:n])
		if err != nil {
			panic(err)
		}
	}
}