golang使用ssl/tls加密tcp（不是https）

参考：https://www.jianshu.com/p/f88f1f3b23a1

1.创建证书

1.创建根证书私钥长度为2048
openssl genrsa -out ca.key 2048

2.利用私钥创建根证书按照提示一路输入：
openssl req -new -x509 -days 36500 -key ca.key -out ca.crt

3.创建长度为2048的SSL证书私匙
openssl genrsa -out server.key 2048

4.利用刚才的私匙建立SSL证书请求一路向下：
openssl req -new -key server.key -out server.csr

5.当前文件夹下运行如下命令创建所需目录：
mkdir dir demoCA &&cd demoCA&&mkdir newcerts&&echo '10' > serial &&touch index.txt&&cd ..

6.用CA根证书签署SSL自建证书：
openssl ca -in server.csr -out server.crt -cert ca.crt -keyfile ca.key

7.查看证书
openssl x509 -in server.crt -noout -text

2.代码编写

服务端：

package main

import (
    "crypto/rand"
    "crypto/tls"
    "fmt"
    "log"
    "net"
    "time"
)

func HandleClientConnect(conn net.Conn) {
    defer conn.Close()
    fmt.Println("Receive Connect Request From ", conn.RemoteAddr().String())
    buffer := make([]byte, 1024)
    for {
        len, err := conn.Read(buffer)
        if err != nil {
            log.Println(err.Error())
            break
        }
        fmt.Printf("Receive Data: %s\n", string(buffer[:len]))
        //发送给客户端
        _, err = conn.Write([]byte("服务器收到数据:" + string(buffer[:len])))
        if err != nil {
            break
        }
    }
    fmt.Println("Client " + conn.RemoteAddr().String() + " Connection Closed.....")
}

func main() {
    crt, err := tls.LoadX509KeyPair("server.crt", "server.key")
    if err != nil {
        log.Fatalln(err.Error())
    }
    tlsConfig := &tls.Config{}
    tlsConfig.Certificates = []tls.Certificate{crt}
    // Time returns the current time as the number of seconds since the epoch.
    // If Time is nil, TLS uses time.Now.
    tlsConfig.Time = time.Now
    // Rand provides the source of entropy for nonces and RSA blinding.
    // If Rand is nil, TLS uses the cryptographic random reader in package
    // crypto/rand.
    // The Reader must be safe for use by multiple goroutines.
    tlsConfig.Rand = rand.Reader
    l, err := tls.Listen("tcp", ":8888", tlsConfig)
    if err != nil {
        log.Fatalln(err.Error())
    }
    for {
        conn, err := l.Accept()
        if err != nil {
            fmt.Println(err.Error())
            continue
        } else {
            go HandleClientConnect(conn)
        }
    }

}

客户端:

package main

import (
    "crypto/tls"
    "fmt"
    "io"
    "time"
    "log"
)

func main() {
    conf := &tls.Config{
        InsecureSkipVerify: true, //这里是跳过证书验证，因为证书签发机构的CA证书是不被认证的
    }
    //注意这里要使用证书中包含的主机名称
    conn, err := tls.Dial("tcp", "127.0.0.1:8888", conf)
    if err != nil {
        log.Fatalln(err.Error())
    }
    defer conn.Close()
    log.Println("Client Connect To ", conn.RemoteAddr())
    status := conn.ConnectionState()
    fmt.Printf("%#v\n", status)
    buf := make([]byte, 1024)
    ticker := time.NewTicker(1 * time.Millisecond * 500)
    for {
        select {
        case <-ticker.C:
            {
                _, err = io.WriteString(conn, "hello")
                if err != nil {
                    log.Fatalln(err.Error())
                }
                len, err := conn.Read(buf)
                if err != nil {
                    fmt.Println(err.Error())
                } else {
                    fmt.Println("Receive From Server:", string(buf[:len]))
                }
            }
        }
    }

}

上述客户端配置了InsecureSkipVerify参数，该参数表示客户端跳过对证书链的校验，因为CA证书是不是计算机内置的。那如果我们希望完整的验证过程，那么我们可以把CA证书也发给客户端，客户端代码修改为

// gohttps/6-dual-verify-certs/client.go

package main
import (
    "crypto/tls"
    "crypto/x509"
    "fmt"
    "io/ioutil"
    "net/http"
)

func main() {
    pool := x509.NewCertPool()
    caCertPath := "ca.crt"

    caCrt, err := ioutil.ReadFile(caCertPath)
    if err != nil {
        fmt.Println("ReadFile err:", err)
        return
    }
    pool.AppendCertsFromPEM(caCrt)

    cliCrt, err := tls.LoadX509KeyPair("client.crt", "client.key")
    if err != nil {
        fmt.Println("Loadx509keypair err:", err)
        return
    }

    tr := &http.Transport{
        TLSClientConfig: &tls.Config{
            RootCAs:      pool,
            Certificates: []tls.Certificate{cliCrt},
        },
    }
    client := &http.Client{Transport: tr}
    resp, err := client.Get("https://localhost:8081")
    if err != nil {
        fmt.Println("Get error:", err)
        return
    }
    defer resp.Body.Close()
    body, err := ioutil.ReadAll(resp.Body)
    fmt.Println(string(body))
}