kubernetes-course/mutatingwebhook/main.go

package main

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

func main() {

	// setup certs
	fmt.Printf("Initializing certificates...\n")
	serverTLSConf, clientTLSConf, caPEM, err := certsetup()
	if err != nil {
		panic(err)
	}

	s := Server{
		ServerTLSConf: serverTLSConf,
		ClientTLSConf: clientTLSConf,
		CaPEM:         caPEM,
	}

	go func() {
		handler := http.NewServeMux()

		handler.HandleFunc("/ca.pem", s.getCA)
		fmt.Printf("Starting localhost http server on :8080 with ca.pem endpoint\n")
		err = http.ListenAndServe("localhost:8080", handler)

		if err != nil {
			log.Fatal(err)
		}
	}()

	// start TLS server
	fmt.Printf("Starting TLS server on :8443\n")
	handler := http.NewServeMux()
	handler.HandleFunc("/webhook", s.postWebhook)

	https := &http.Server{
		Addr:      ":8443",
		TLSConfig: serverTLSConf,
		Handler:   handler,
	}

	log.Fatal(https.ListenAndServeTLS("", ""))

}

// certsetup adapted from https://gist.github.com/shaneutt/5e1995295cff6721c89a71d13a71c251
func certsetup() (serverTLSConf *tls.Config, clientTLSConf *tls.Config, caPEMBytes []byte, err error) {
	// set up our CA certificate
	ca := &x509.Certificate{
		SerialNumber: big.NewInt(2019),
		Subject: pkix.Name{
			Organization:  []string{"Company, INC."},
			Country:       []string{"US"},
			Province:      []string{""},
			Locality:      []string{"San Francisco"},
			StreetAddress: []string{"Golden Gate Bridge"},
			PostalCode:    []string{"94016"},
		},
		NotBefore:             time.Now(),
		NotAfter:              time.Now().AddDate(10, 0, 0),
		IsCA:                  true,
		ExtKeyUsage:           []x509.ExtKeyUsage{x509.ExtKeyUsageClientAuth, x509.ExtKeyUsageServerAuth},
		KeyUsage:              x509.KeyUsageDigitalSignature | x509.KeyUsageCertSign,
		BasicConstraintsValid: true,
	}

	// create our private and public key
	caPrivKey, err := rsa.GenerateKey(rand.Reader, 4096)
	if err != nil {
		return nil, nil, []byte{}, err
	}

	// create the CA
	caBytes, err := x509.CreateCertificate(rand.Reader, ca, ca, &caPrivKey.PublicKey, caPrivKey)
	if err != nil {
		return nil, nil, []byte{}, err
	}

	// pem encode
	caPEM := new(bytes.Buffer)
	pem.Encode(caPEM, &pem.Block{
		Type:  "CERTIFICATE",
		Bytes: caBytes,
	})

	caPrivKeyPEM := new(bytes.Buffer)
	pem.Encode(caPrivKeyPEM, &pem.Block{
		Type:  "RSA PRIVATE KEY",
		Bytes: x509.MarshalPKCS1PrivateKey(caPrivKey),
	})

	// set up our server certificate
	cert := &x509.Certificate{
		SerialNumber: big.NewInt(2019),
		Subject: pkix.Name{
			Organization:  []string{"Company, INC."},
			Country:       []string{"US"},
			Province:      []string{""},
			Locality:      []string{"San Francisco"},
			StreetAddress: []string{"Golden Gate Bridge"},
			PostalCode:    []string{"94016"},
		},
		IPAddresses:  []net.IP{net.IPv4(127, 0, 0, 1), net.IPv6loopback},
		NotBefore:    time.Now(),
		NotAfter:     time.Now().AddDate(10, 0, 0),
		SubjectKeyId: []byte{1, 2, 3, 4, 6},
		ExtKeyUsage:  []x509.ExtKeyUsage{x509.ExtKeyUsageClientAuth, x509.ExtKeyUsageServerAuth},
		KeyUsage:     x509.KeyUsageDigitalSignature,
		DNSNames:     []string{"mutatingwebhook.mutatingwebhook.svc"},
	}

	certPrivKey, err := rsa.GenerateKey(rand.Reader, 4096)
	if err != nil {
		return nil, nil, []byte{}, err
	}

	certBytes, err := x509.CreateCertificate(rand.Reader, cert, ca, &certPrivKey.PublicKey, caPrivKey)
	if err != nil {
		return nil, nil, []byte{}, err
	}

	certPEM := new(bytes.Buffer)
	pem.Encode(certPEM, &pem.Block{
		Type:  "CERTIFICATE",
		Bytes: certBytes,
	})

	certPrivKeyPEM := new(bytes.Buffer)
	pem.Encode(certPrivKeyPEM, &pem.Block{
		Type:  "RSA PRIVATE KEY",
		Bytes: x509.MarshalPKCS1PrivateKey(certPrivKey),
	})

	serverCert, err := tls.X509KeyPair(certPEM.Bytes(), certPrivKeyPEM.Bytes())
	if err != nil {
		return nil, nil, []byte{}, err
	}

	serverTLSConf = &tls.Config{
		Certificates: []tls.Certificate{serverCert},
	}

	certpool := x509.NewCertPool()
	certpool.AppendCertsFromPEM(caPEM.Bytes())
	clientTLSConf = &tls.Config{
		RootCAs: certpool,
	}

	caPEMBytes = caPEM.Bytes()

	return
}