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rotator.go
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rotator.go
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package mtls
import (
"bytes"
"context"
"crypto/rand"
"crypto/rsa"
"crypto/tls"
"crypto/x509"
"crypto/x509/pkix"
"encoding/pem"
"fmt"
"math/big"
"os"
"sync"
"time"
"github.com/pkg/errors"
infrav1 "github.com/weaveworks/tf-controller/api/v1alpha1"
corev1 "k8s.io/api/core/v1"
"k8s.io/apimachinery/pkg/api/meta"
metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
"k8s.io/apimachinery/pkg/runtime"
"k8s.io/client-go/rest"
"sigs.k8s.io/controller-runtime/pkg/client"
logf "sigs.k8s.io/controller-runtime/pkg/log"
"sigs.k8s.io/controller-runtime/pkg/manager"
)
const (
certName = "tls.crt"
keyName = "tls.key"
caCertName = "ca.crt"
caKeyName = "ca.key"
)
var crLog = logf.Log.WithName("cert-rotation")
var _ manager.Runnable = &CertRotator{}
/*
// SyncingReader is a reader that needs syncing prior to being usable.
type SyncingReader interface {
client.Reader
WaitForCacheSync(ctx context.Context) bool
}*/
// PartialManager is a subset of the manager.Manager interface that is used by the CertRotator.
type PartialManager interface {
GetConfig() *rest.Config
GetScheme() *runtime.Scheme
GetRESTMapper() meta.RESTMapper
Elected() <-chan struct{}
}
// KeyPairArtifacts stores cert artifacts.
type KeyPairArtifacts struct {
Cert *x509.Certificate
Key *rsa.PrivateKey
CertPEM []byte
KeyPEM []byte
validUntil time.Time
}
type artifact struct {
ca *KeyPairArtifacts
certSecret *corev1.Secret
}
type TriggerResult struct {
Secret *corev1.Secret
Err error
}
type Trigger struct {
Namespace string
Ready chan *TriggerResult
}
// CertRotator contains cert artifacts and a channel to close when the certs are ready.
type CertRotator struct {
writer client.Client
mgr manager.Manager
extKeyUsages *[]x509.ExtKeyUsage
Ready chan struct{}
CAName string
CAOrganization string
DNSName string
CAValidityDuration time.Duration
// CertValidityDuration time.Duration
RotationCheckFrequency time.Duration
LookaheadInterval time.Duration
TriggerCARotation chan Trigger // trigger the CA rotation
TriggerNamespaceTLSGeneration chan Trigger // trigger namespace TLS generation
artifactCaches []*artifact
knownNamespaceTLSMap map[string]*TriggerResult
knownNamespaceTLSMapMu sync.Mutex
}
func (cr *CertRotator) GetTLSGenerationResult(namespace string) (*corev1.Secret, error) {
cr.knownNamespaceTLSMapMu.Lock()
defer cr.knownNamespaceTLSMapMu.Unlock()
result := cr.knownNamespaceTLSMap[namespace]
if result == nil {
return nil, errors.New("no TLS generation result")
}
return result.Secret, result.Err
}
// AddRotator adds the CertRotator and ReconcileWH to the manager.
func AddRotator(ctx context.Context, mgr manager.Manager, cr *CertRotator) error {
if mgr == nil || cr == nil {
return fmt.Errorf("nil arguments")
}
cr.writer = mgr.GetClient() // TODO make overrideable
cr.mgr = mgr
cr.knownNamespaceTLSMap = make(map[string]*TriggerResult)
if err := mgr.Add(cr); err != nil {
return err
}
return nil
}
// IsCAValid checks that the CA[n-1] is valid.
func (cr *CertRotator) IsCAValid() (bool, error) {
n := len(cr.artifactCaches)
if n == 0 {
return false, errors.New("no CA in the cache")
}
validUntil := cr.artifactCaches[n-1].ca.validUntil
if validUntil.Before(cr.lookaheadTime()) {
return true, nil
}
return false, nil
}
// Start starts the CertRotator runnable to rotate certs and ensure the certs are ready.
func (cr *CertRotator) Start(ctx context.Context) error {
// Only the leader do cert rotation.
// if we're not, we're blocked here and don't do any cert rotation until we becomes the leader.
<-cr.mgr.Elected()
cr.extKeyUsages = &[]x509.ExtKeyUsage{x509.ExtKeyUsageServerAuth, x509.ExtKeyUsageClientAuth}
// explicitly rotate on the first round so that the certificate
// can be bootstrapped, otherwise mgr exits before a cert can be written
crLog.Info("starting cert rotator controller")
defer crLog.Info("stopping cert rotator controller")
if err := cr.refreshCertsInMemory(); err != nil {
crLog.Error(err, "could not refresh cert on startup")
return err
}
close(cr.Ready)
// TODO implement GC for getting rid of old certs
ticker := time.NewTicker(cr.RotationCheckFrequency)
tickerLoop:
for {
select {
case trigger := <-cr.TriggerCARotation:
if err := cr.refreshCACertsIfNeeded(); err != nil {
crLog.Error(err, "could not refresh cert")
}
// if no channel passing it, skip
if trigger.Ready != nil {
n := len(cr.artifactCaches)
secret := cr.artifactCaches[n-1].certSecret
trigger.Ready <- &TriggerResult{Secret: secret, Err: nil}
}
case <-ticker.C:
if err := cr.refreshCACertsIfNeeded(); err != nil {
crLog.Error(err, "could not refresh cert")
}
// GC: garbage collect the old CA artifacts
for {
if len(cr.artifactCaches) == 0 {
break
}
validUntil := cr.artifactCaches[0].ca.validUntil
// we must NOT use cr.lookaheadTime() here
if validUntil.Before(time.Now()) {
cr.artifactCaches = cr.artifactCaches[1:]
for namespace := range cr.knownNamespaceTLSMap {
err := cr.writer.Delete(context.TODO(), &corev1.Secret{
ObjectMeta: metav1.ObjectMeta{
Namespace: namespace,
Name: fmt.Sprintf("%s-%d", infrav1.RunnerTLSSecretName, validUntil.Unix()),
},
}, client.PropagationPolicy(metav1.DeletePropagationBackground))
if err != nil {
crLog.Error(err, "could not delete old CA artifact")
}
}
} else {
break
}
}
case trigger := <-cr.TriggerNamespaceTLSGeneration:
namespace := trigger.Namespace
if _, ok := cr.knownNamespaceTLSMap[namespace]; !ok {
secret, err := cr.generateNamespaceTLS(namespace)
if err != nil {
crLog.Error(err, "error generating TLS for ", "namespace", namespace)
}
cr.knownNamespaceTLSMap[namespace] = &TriggerResult{Secret: secret, Err: err}
} else {
crLog.Info("TLS already generated for ", "namespace", namespace)
}
trigger.Ready <- cr.knownNamespaceTLSMap[namespace]
case <-ctx.Done():
break tickerLoop
}
}
ticker.Stop()
//close(cr.TriggerCARotation)
//close(cr.TriggerNamespaceTLSGeneration)
return nil
}
func (cr *CertRotator) refreshCACertsIfNeeded() error {
needRegeneration := false
// if there is no CA artifact, refresh certs
n := len(cr.artifactCaches)
if n == 0 {
crLog.Info("no CA in the cache")
if err := cr.refreshCertsInMemory(); err != nil {
return err
} else {
needRegeneration = true
}
} else if n > 0 {
validUntil := cr.artifactCaches[n-1].ca.validUntil
if validUntil.Before(cr.lookaheadTime()) {
if err := cr.refreshCertsInMemory(); err != nil {
return err
} else {
needRegeneration = true
}
}
}
if needRegeneration {
// generate new certs for all namespaces
for namespace := range cr.knownNamespaceTLSMap {
secret, err := cr.generateNamespaceTLS(namespace)
if err != nil {
crLog.Error(err, "could not generate TLS for namespace")
}
cr.knownNamespaceTLSMap[namespace] = &TriggerResult{Secret: secret, Err: err}
}
}
return nil
}
// GetRunnerTLSSecretName returns the name of the TLS Secret.
// It is used by the controller to tell the runner the name of TLS.
func (cr *CertRotator) GetRunnerTLSSecretName() (string, error) {
n := len(cr.artifactCaches)
if n == 0 {
return "", errors.New("no CA in the cache")
}
caArtifacts := cr.artifactCaches[n-1].ca
return fmt.Sprintf("%s-%d", infrav1.RunnerTLSSecretName, caArtifacts.validUntil.Unix()), nil
}
func (cr *CertRotator) refreshCertsInMemory() error {
var caArtifacts *KeyPairArtifacts
now := time.Now()
begin := now.Add(-1 * time.Hour)
end := now.Add(cr.CAValidityDuration)
var err error
caArtifacts, err = cr.createCACert(begin, end)
if err != nil {
return err
}
// create controller-side certificate
cert, key, err := cr.createCertPEM(caArtifacts, cr.DNSName, begin, end)
if err != nil {
return err
}
secret := &corev1.Secret{
Data: map[string][]byte{
caCertName: caArtifacts.CertPEM,
caKeyName: caArtifacts.KeyPEM,
certName: cert,
keyName: key,
},
}
cr.artifactCaches = append(cr.artifactCaches, &artifact{
ca: caArtifacts,
certSecret: secret,
})
return nil
}
func buildArtifactsFromSecret(secret *corev1.Secret) (caArtifacts *KeyPairArtifacts, certArtifacts *KeyPairArtifacts, err error) {
caArtifacts, err = parseArtifacts(caCertName, caKeyName, secret)
if err != nil {
return nil, nil, err
}
certArtifacts, err = parseArtifacts(certName, keyName, secret)
if err != nil {
return nil, nil, err
}
return caArtifacts, certArtifacts, nil
}
func parseArtifacts(certName, keyName string, secret *corev1.Secret) (*KeyPairArtifacts, error) {
certPem, ok := secret.Data[certName]
if !ok {
return nil, errors.New(fmt.Sprintf("Cert Secret is not well-formed, missing %s", caCertName))
}
keyPem, ok := secret.Data[keyName]
if !ok {
return nil, errors.New(fmt.Sprintf("Cert Secret is not well-formed, missing %s", caKeyName))
}
certDer, _ := pem.Decode(certPem)
if certDer == nil {
return nil, errors.New("bad cert")
}
cert, err := x509.ParseCertificate(certDer.Bytes)
if err != nil {
return nil, errors.Wrap(err, "while parsing CA cert")
}
keyDer, _ := pem.Decode(keyPem)
if keyDer == nil {
return nil, errors.New("bad cert")
}
key, err := x509.ParsePKCS1PrivateKey(keyDer.Bytes)
if err != nil {
return nil, errors.Wrap(err, "while parsing key")
}
return &KeyPairArtifacts{
Cert: cert,
CertPEM: certPem,
KeyPEM: keyPem,
Key: key,
}, nil
}
// createCACert creates the self-signed CA cert and private key that will
// be used to sign the server certificate
func (cr *CertRotator) createCACert(begin, end time.Time) (*KeyPairArtifacts, error) {
certTemplate := &x509.Certificate{
SerialNumber: big.NewInt(0),
Subject: pkix.Name{
CommonName: cr.CAName,
Organization: []string{cr.CAOrganization},
},
DNSNames: []string{
cr.CAName,
},
NotBefore: begin,
NotAfter: end,
KeyUsage: x509.KeyUsageDigitalSignature | x509.KeyUsageKeyEncipherment | x509.KeyUsageCertSign,
BasicConstraintsValid: true,
IsCA: true,
}
key, err := rsa.GenerateKey(rand.Reader, 2048)
if err != nil {
return nil, errors.Wrap(err, "generating key")
}
der, err := x509.CreateCertificate(rand.Reader, certTemplate, certTemplate, key.Public(), key)
if err != nil {
return nil, errors.Wrap(err, "creating certificate")
}
certPEM, keyPEM, err := pemEncode(der, key)
if err != nil {
return nil, errors.Wrap(err, "encoding PEM")
}
cert, err := x509.ParseCertificate(der)
if err != nil {
return nil, errors.Wrap(err, "parsing certificate")
}
return &KeyPairArtifacts{Cert: cert, Key: key, CertPEM: certPEM, KeyPEM: keyPEM, validUntil: end}, nil
}
// createCertPEM takes the results of createCACert and uses it to create the
// PEM-encoded public certificate and private key, respectively.
func (cr *CertRotator) createCertPEM(ca *KeyPairArtifacts, hostname string, begin, end time.Time) ([]byte, []byte, error) {
dnsNames := []string{hostname}
if os.Getenv("INSECURE_LOCAL_RUNNER") == "1" {
dnsNames = append(dnsNames, "localhost")
}
certTemplate := &x509.Certificate{
SerialNumber: big.NewInt(1),
Subject: pkix.Name{
CommonName: cr.DNSName,
},
DNSNames: dnsNames,
NotBefore: begin,
NotAfter: end,
KeyUsage: x509.KeyUsageDigitalSignature | x509.KeyUsageKeyEncipherment,
ExtKeyUsage: []x509.ExtKeyUsage{x509.ExtKeyUsageServerAuth, x509.ExtKeyUsageClientAuth},
BasicConstraintsValid: true,
}
key, err := rsa.GenerateKey(rand.Reader, 2048)
if err != nil {
return nil, nil, errors.Wrap(err, "generating key")
}
der, err := x509.CreateCertificate(rand.Reader, certTemplate, ca.Cert, key.Public(), ca.Key)
if err != nil {
return nil, nil, errors.Wrap(err, "creating certificate")
}
certPEM, keyPEM, err := pemEncode(der, key)
if err != nil {
return nil, nil, errors.Wrap(err, "encoding PEM")
}
return certPEM, keyPEM, nil
}
// pemEncode takes a certificate and encodes it as PEM
func pemEncode(certificateDER []byte, key *rsa.PrivateKey) ([]byte, []byte, error) {
certBuf := &bytes.Buffer{}
if err := pem.Encode(certBuf, &pem.Block{Type: "CERTIFICATE", Bytes: certificateDER}); err != nil {
return nil, nil, errors.Wrap(err, "encoding cert")
}
keyBuf := &bytes.Buffer{}
if err := pem.Encode(keyBuf, &pem.Block{Type: "RSA PRIVATE KEY", Bytes: x509.MarshalPKCS1PrivateKey(key)}); err != nil {
return nil, nil, errors.Wrap(err, "encoding key")
}
return certBuf.Bytes(), keyBuf.Bytes(), nil
}
func (cr *CertRotator) lookaheadTime() time.Time {
return time.Now().Add(cr.LookaheadInterval)
}
func (cr *CertRotator) validServerCert(caCert, cert, key []byte) bool {
valid, err := ValidCert(caCert, cert, key, cr.DNSName, cr.extKeyUsages, cr.lookaheadTime())
if err != nil {
return false
}
return valid
}
func (cr *CertRotator) validCACert(cert, key []byte) bool {
valid, err := ValidCert(cert, cert, key, cr.CAName, nil, cr.lookaheadTime())
if err != nil {
return false
}
return valid
}
func (cr *CertRotator) generateNamespaceTLS(namespace string) (*corev1.Secret, error) {
n := len(cr.artifactCaches)
// get last artifact cache
artifactCache := cr.artifactCaches[n-1]
caArtifacts := artifactCache.ca
hostname := fmt.Sprintf("*.%s.pod.cluster.local", namespace)
cert, key, err := cr.createCertPEM(caArtifacts, hostname, time.Now().Add(-1*time.Hour), caArtifacts.validUntil)
if err != nil {
return nil, err
}
name := fmt.Sprintf("%s-%d", infrav1.RunnerTLSSecretName, caArtifacts.validUntil.Unix())
tlsCertSecret := &corev1.Secret{
ObjectMeta: metav1.ObjectMeta{
Namespace: namespace,
Name: name,
Labels: map[string]string{
infrav1.RunnerLabel: "true",
},
},
Type: corev1.SecretTypeTLS,
Data: map[string][]byte{
caCertName: caArtifacts.CertPEM,
caKeyName: caArtifacts.KeyPEM,
certName: cert,
keyName: key,
},
}
if err := cr.writer.Create(context.TODO(), tlsCertSecret); err != nil {
return nil, err
}
return tlsCertSecret, nil
}
func (cr *CertRotator) ResetCACache() {
cr.artifactCaches = []*artifact{}
}
func ValidCert(caCert, cert, key []byte, dnsName string, keyUsages *[]x509.ExtKeyUsage, at time.Time) (bool, error) {
if len(caCert) == 0 || len(cert) == 0 || len(key) == 0 {
return false, errors.New("empty cert")
}
pool := x509.NewCertPool()
caDer, _ := pem.Decode(caCert)
if caDer == nil {
return false, errors.New("bad CA cert")
}
cac, err := x509.ParseCertificate(caDer.Bytes)
if err != nil {
return false, errors.Wrap(err, "parsing CA cert")
}
pool.AddCert(cac)
_, err = tls.X509KeyPair(cert, key)
if err != nil {
return false, errors.Wrap(err, "building key pair")
}
b, _ := pem.Decode(cert)
if b == nil {
return false, errors.New("bad private key")
}
crt, err := x509.ParseCertificate(b.Bytes)
if err != nil {
return false, errors.Wrap(err, "parsing cert")
}
opt := x509.VerifyOptions{
DNSName: dnsName,
Roots: pool,
CurrentTime: at,
}
if keyUsages != nil {
opt.KeyUsages = *keyUsages
}
_, err = crt.Verify(opt)
if err != nil {
return false, errors.Wrap(err, "verifying cert")
}
return true, nil
}