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init.go
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init.go
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/*
Copyright 2018 The kube-fledged authors.
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/
package app
import (
"bytes"
"context"
cryptorand "crypto/rand"
"crypto/rsa"
"crypto/x509"
"crypto/x509/pkix"
"encoding/pem"
"math/big"
"os"
"time"
"github.com/golang/glog"
metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
"k8s.io/client-go/kubernetes"
"k8s.io/client-go/rest"
)
// InitWebhookServer initialises kube-fledged webhook server:-
// - generates cert/key pair
// - patched CA bundle to validatingwebhookconfiguration
func InitWebhookServer() error {
var caPEM, serverCertPEM, serverPrivKeyPEM *bytes.Buffer
webhookServerService := os.Getenv("WEBHOOK_SERVER_SERVICE")
webhookServerNameSpace := os.Getenv("KUBEFLEDGED_NAMESPACE")
certKeyPath := os.Getenv("CERT_KEY_PATH")
validatingWebhookConfig := os.Getenv("VALIDATING_WEBHOOK_CONFIG")
// CA config
caConf := &x509.Certificate{
SerialNumber: big.NewInt(2021),
Subject: pkix.Name{
Organization: []string{"kubefledged.io"},
},
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,
}
// CA private key
caPrivKey, err := rsa.GenerateKey(cryptorand.Reader, 4096)
if err != nil {
glog.Errorf("error in generating CA private key: %v", err)
return err
}
glog.Info("success: ca private key created")
// Self signed CA certificate
caBytes, err := x509.CreateCertificate(cryptorand.Reader, caConf, caConf, &caPrivKey.PublicKey, caPrivKey)
if err != nil {
glog.Errorf("error in generating CA certificate: %v", err)
return err
}
glog.Info("success: self-signed ca certificate created")
// PEM encode CA cert
caPEM = new(bytes.Buffer)
_ = pem.Encode(caPEM, &pem.Block{
Type: "CERTIFICATE",
Bytes: caBytes,
})
glog.Info("success: ca certificate encoded to pem format")
dnsNames := []string{
webhookServerService,
webhookServerService + "." + webhookServerNameSpace,
webhookServerService + "." + webhookServerNameSpace + ".svc",
webhookServerService + "." + webhookServerNameSpace + ".svc.cluster"}
commonName := webhookServerService + "." + webhookServerNameSpace + ".svc"
// server cert config
certConf := &x509.Certificate{
DNSNames: dnsNames,
SerialNumber: big.NewInt(1658),
Subject: pkix.Name{
CommonName: commonName,
Organization: []string{"kubefledged.io"},
},
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,
}
// server private key
serverPrivKey, err := rsa.GenerateKey(cryptorand.Reader, 4096)
if err != nil {
glog.Errorf("error in generating server private key: %v", err)
return err
}
glog.Info("success: server private key created")
// sign the server cert
serverCertBytes, err := x509.CreateCertificate(cryptorand.Reader, certConf, caConf, &serverPrivKey.PublicKey, caPrivKey)
if err != nil {
glog.Errorf("error in generating server certificate: %v", err)
return err
}
glog.Info("success: server certificate created")
// PEM encode the server cert and key
serverCertPEM = new(bytes.Buffer)
_ = pem.Encode(serverCertPEM, &pem.Block{
Type: "CERTIFICATE",
Bytes: serverCertBytes,
})
glog.Info("success: server certificate encoded to pem format")
serverPrivKeyPEM = new(bytes.Buffer)
_ = pem.Encode(serverPrivKeyPEM, &pem.Block{
Type: "RSA PRIVATE KEY",
Bytes: x509.MarshalPKCS1PrivateKey(serverPrivKey),
})
glog.Info("success: server private key encoded to pem format")
err = os.MkdirAll(certKeyPath, 0666)
if err != nil {
glog.Errorf("error in creating directory %s: %v", certKeyPath, err)
return err
}
err = writeFile(certKeyPath+"tls.crt", serverCertPEM)
if err != nil {
glog.Errorf("error in writing tls.crt: %v", err)
return err
}
glog.Infof("success: server cert (tls.crt) copied to %s", certKeyPath)
err = writeFile(certKeyPath+"tls.key", serverPrivKeyPEM)
if err != nil {
glog.Errorf("error in writing tls.key: %v", err)
return err
}
glog.Infof("success: server key (tls.key) copied to %s", certKeyPath)
err = updateValidatingWebhookConfig(caPEM, validatingWebhookConfig)
if err != nil {
return err
}
glog.Infof("success: validatingwebhookconfiguration %s updated", validatingWebhookConfig)
return nil
}
// writeFile writes data in the file at the given path
func writeFile(filepath string, sCert *bytes.Buffer) error {
f, err := os.Create(filepath)
if err != nil {
return err
}
defer f.Close()
_, err = f.Write(sCert.Bytes())
if err != nil {
return err
}
return nil
}
func updateValidatingWebhookConfig(caPEM *bytes.Buffer, validatingWebhookConfig string) error {
cfg, err := rest.InClusterConfig()
if err != nil {
glog.Fatalf("Error building kubeconfig: %s", err.Error())
return err
}
kubeClient, err := kubernetes.NewForConfig(cfg)
if err != nil {
glog.Fatalf("Error building kubernetes clientset: %s", err.Error())
return err
}
vwc, err := kubeClient.AdmissionregistrationV1().ValidatingWebhookConfigurations().Get(
context.TODO(), validatingWebhookConfig, metav1.GetOptions{})
if err != nil {
glog.Errorf("Error in getting validatingwebhookconfig: %s", err.Error())
return err
}
vwc.Webhooks[0].ClientConfig.CABundle = caPEM.Bytes()
_, err = kubeClient.AdmissionregistrationV1().ValidatingWebhookConfigurations().Update(
context.TODO(), vwc, metav1.UpdateOptions{})
if err != nil {
glog.Errorf("Error in updating validatingwebhookconfig: %s", err.Error())
return err
}
return nil
}