Debug tls versions

gistfile1.txt

package main

import (
	"crypto/tls"
	"crypto/x509"
	"fmt"
	"io/ioutil"
	"log"
	"net"
	"os"
	"time"
)

func main() {
	var tlsConfig *tls.Config
	addr := os.Args[1]
	for tlsVersionStr, tlsVersion := range map[string]uint16{"sslv3": tls.VersionSSL30, "tls1": tls.VersionTLS10, "tls1.1": tls.VersionTLS11, "tls1.2": tls.VersionTLS12} {
		fmt.Println("trying", tlsVersionStr)
		if len(os.Args) > 2 {
			caCertFile := os.Args[2]
			caCert, err := ioutil.ReadFile(caCertFile)
			if err != nil {
				log.Fatal(err)
			}
			caCertPool := x509.NewCertPool()
			caCertPool.AppendCertsFromPEM(caCert)
			tlsConfig = &tls.Config{
				RootCAs:    caCertPool,
				MinVersion: tlsVersion,
				MaxVersion: tlsVersion,
			}
			tlsConfig.BuildNameToCertificate()
		}

		dialer := &net.Dialer{Timeout: 2 * time.Second}
		conn, err := tls.DialWithDialer(dialer, "tcp", addr, tlsConfig)
		if err != nil {
			log.Println(err)
			continue
		}
		conn.Close()
	}
}