th5/_dev/tls_examples/ems_client.go

package main

import (
	"bufio"
	"crypto/tls"
	"flag"
	"fmt"
	"io"
	"net/http"
	"net/url"
	"os"
)

var tlsVersionToName = map[string]uint16{
	"tls10": tls.VersionTLS10,
	"tls11": tls.VersionTLS11,
	"tls12": tls.VersionTLS12,
	"tls13": tls.VersionTLS13,
}

// Usage client args host:port
func main() {
	var version string
	var addr string
	var enableEMS bool
	var resume bool
	var config tls.Config
	var cache tls.ClientSessionCache
	cache = tls.NewLRUClientSessionCache(0)
	flag.StringVar(&version, "version", "tls12", "Version of TLS to use")
	flag.BoolVar(&enableEMS, "m", false, "Enable EMS")
	flag.BoolVar(&resume, "r", false, "Attempt Resumption")
	flag.Parse()
	config.MinVersion = tlsVersionToName[version]
	config.MaxVersion = tlsVersionToName[version]
	config.InsecureSkipVerify = true
	config.UseExtendedMasterSecret = !enableEMS
	config.ClientSessionCache = cache
	var iters int
	if resume {
		iters = 2
	} else {
		iters = 1
	}
	addr = flag.Arg(0)
	for ; iters > 0; iters-- {
		conn, err := tls.Dial("tcp", addr, &config)
		if err != nil {
			fmt.Println("Error %s", err)
			os.Exit(1)
		}
		var req http.Request
		var response *http.Response
		req.Method = "GET"
		req.URL, err = url.Parse("https://" + addr + "/")
		if err != nil {
			fmt.Println("Failed to parse url")
			os.Exit(1)
		}
		req.Write(conn)
		reader := bufio.NewReader(conn)
		response, err = http.ReadResponse(reader, nil)
		if err != nil {
			fmt.Println("HTTP problem")
			fmt.Println(err)
			os.Exit(1)
		}
		io.Copy(os.Stdout, response.Body)
		conn.Close()
		if resume && iters == 2 {
			fmt.Println("Attempting resumption")
		}
	}
	os.Exit(0)
}