在k8s的源码里看的，记录一下

package main

import (
	"bytes"
	cryptorand "crypto/rand"
	"crypto/rsa"
	"crypto/x509"
	"crypto/x509/pkix"
	"encoding/pem"
	"fmt"
	"math/big"
	"net"
	"time"
)

func main() {
	ip := []byte("192.168.100.1")
	alternateDNS := []string{"kubernetes.default.svc", "kubernetes.default", "kubernetes", "localhost"}
	cert, key, _ := GenerateSelfSignedCertKey("10.10.10.10", []net.IP{ip}, alternateDNS)
	fmt.Println(string(cert), string(key))

}

func GenerateSelfSignedCertKey(host string, alternateIPs []net.IP, alternateDNS []string) ([]byte, []byte, error) {
	priv, err := rsa.GenerateKey(cryptorand.Reader, 2048)
	if err != nil {
		return nil, nil, err
	}

	template := x509.Certificate{
		SerialNumber: big.NewInt(1),
		Subject: pkix.Name{
			CommonName: fmt.Sprintf("%s@%d", host, time.Now().Unix()),
		},
		NotBefore: time.Now(),
		NotAfter:  time.Now().Add(time.Hour * 24 * 365),

		KeyUsage:              x509.KeyUsageKeyEncipherment | x509.KeyUsageDigitalSignature | x509.KeyUsageCertSign,
		ExtKeyUsage:           []x509.ExtKeyUsage{x509.ExtKeyUsageServerAuth},
		BasicConstraintsValid: true,
		IsCA: true,
	}

	if ip := net.ParseIP(host); ip != nil {
		template.IPAddresses = append(template.IPAddresses, ip)
	} else {
		template.DNSNames = append(template.DNSNames, host)
	}

	template.IPAddresses = append(template.IPAddresses, alternateIPs...)
	template.DNSNames = append(template.DNSNames, alternateDNS...)

	derBytes, err := x509.CreateCertificate(cryptorand.Reader, &template, &template, &priv.PublicKey, priv)
	if err != nil {
		return nil, nil, err
	}

	// Generate cert
	certBuffer := bytes.Buffer{}
	if err := pem.Encode(&certBuffer, &pem.Block{Type: "CERTIFICATE", Bytes: derBytes}); err != nil {
		return nil, nil, err
	}

	// Generate key
	keyBuffer := bytes.Buffer{}
	if err := pem.Encode(&keyBuffer, &pem.Block{Type: "RSA PRIVATE KEY", Bytes: x509.MarshalPKCS1PrivateKey(priv)}); err != nil {
		return nil, nil, err
	}

	return certBuffer.Bytes(), keyBuffer.Bytes(), nil
}