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keyholder.go
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keyholder.go
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// Copyright 2017 The Kubernetes 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 jwe
import (
"crypto/rand"
"crypto/rsa"
"log"
"sync"
authApi "github.com/kubernetes/dashboard/src/app/backend/auth/api"
syncApi "github.com/kubernetes/dashboard/src/app/backend/sync/api"
jose "gopkg.in/square/go-jose.v2"
"k8s.io/api/core/v1"
k8sErrors "k8s.io/apimachinery/pkg/api/errors"
metaV1 "k8s.io/apimachinery/pkg/apis/meta/v1"
"k8s.io/apimachinery/pkg/runtime"
"k8s.io/apimachinery/pkg/watch"
)
// Entries held by resource used to synchronize encryption key data.
const (
holderMapKeyEntry = "priv"
holderMapCertEntry = "pub"
)
// KeyHolder is responsible for generating, storing and synchronizing encryption key used for token
// generation/decryption.
type KeyHolder interface {
// Returns encrypter instance that can be used to encrypt data.
Encrypter() jose.Encrypter
// Returns encryption key that can be used to decrypt data.
Key() *rsa.PrivateKey
// Forces refresh of encryption key synchronized with kubernetes resource (secret).
Refresh()
}
// Implements KeyHolder interface
type rsaKeyHolder struct {
// 256-byte random RSA key pair. Synced with a key saved in a secret.
key *rsa.PrivateKey
synchronizer syncApi.Synchronizer
mux sync.Mutex
}
// Encrypter implements key holder interface. See KeyHolder for more information.
// Used encryption algorithms:
// - Content encryption: AES-GCM (256)
// - Key management: RSA-OAEP-SHA256
func (self *rsaKeyHolder) Encrypter() jose.Encrypter {
publicKey := &self.Key().PublicKey
encrypter, err := jose.NewEncrypter(jose.A256GCM, jose.Recipient{Algorithm: jose.RSA_OAEP_256, Key: publicKey}, nil)
if err != nil {
panic(err)
}
return encrypter
}
// Key implements key holder interface. See KeyHolder for more information.
func (self *rsaKeyHolder) Key() *rsa.PrivateKey {
self.mux.Lock()
defer self.mux.Unlock()
return self.key
}
// Refresh implements key holder interface. See KeyHolder for more information.
func (self *rsaKeyHolder) Refresh() {
self.synchronizer.Refresh()
self.update(self.synchronizer.Get())
}
// Handler function executed by synchronizer used to store encryption key. It is called whenever watched object
// is created or updated.
func (self *rsaKeyHolder) update(obj runtime.Object) {
secret := obj.(*v1.Secret)
priv, err := ParseRSAKey(string(secret.Data[holderMapKeyEntry]), string(secret.Data[holderMapCertEntry]))
if err != nil {
// Secret was probably tampered with. Update it based on local key.
err := self.synchronizer.Update(self.getEncryptionKeyHolder())
if err != nil {
panic(err)
}
return
}
self.mux.Lock()
defer self.mux.Unlock()
self.key = priv
}
// Handler function executed by synchronizer used to store encryption key. It is called whenever watched object
// is gets deleted. It is then recreated based on local key.
func (self *rsaKeyHolder) recreate(obj runtime.Object) {
secret := obj.(*v1.Secret)
log.Printf("Synchronized secret %s has been deleted. Recreating.", secret.Name)
self.synchronizer.Create(self.getEncryptionKeyHolder())
}
func (self *rsaKeyHolder) init() {
self.initEncryptionKey()
// Register event handlers
self.synchronizer.RegisterActionHandler(self.update, watch.Added, watch.Modified)
self.synchronizer.RegisterActionHandler(self.recreate, watch.Deleted)
// Try to init key from synchronized object
if obj := self.synchronizer.Get(); obj != nil {
log.Print("Initializing JWE encryption key from synchronized object")
self.update(obj)
return
}
// Try to save generated key in a secret
log.Printf("Storing encryption key in a secret")
err := self.synchronizer.Create(self.getEncryptionKeyHolder())
if err != nil && !k8sErrors.IsAlreadyExists(err) {
panic(err)
}
}
func (self *rsaKeyHolder) getEncryptionKeyHolder() runtime.Object {
priv, pub := ExportRSAKeyOrDie(self.Key())
return &v1.Secret{
ObjectMeta: metaV1.ObjectMeta{
Namespace: authApi.EncryptionKeyHolderNamespace,
Name: authApi.EncryptionKeyHolderName,
},
Data: map[string][]byte{
holderMapKeyEntry: []byte(priv),
holderMapCertEntry: []byte(pub),
},
}
}
// Generates encryption key used to encrypt token payload.
func (self *rsaKeyHolder) initEncryptionKey() {
log.Print("Generating JWE encryption key")
self.mux.Lock()
defer self.mux.Unlock()
privateKey, err := rsa.GenerateKey(rand.Reader, 2048)
if err != nil {
panic(err)
}
self.key = privateKey
}
// NewRSAKeyHolder creates new KeyHolder instance.
func NewRSAKeyHolder(synchronizer syncApi.Synchronizer) KeyHolder {
holder := &rsaKeyHolder{
synchronizer: synchronizer,
}
holder.init()
return holder
}