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jwt.go
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jwt.go
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/*
Copyright 2014 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 serviceaccount
import (
"bytes"
"crypto/ecdsa"
"crypto/elliptic"
"crypto/rsa"
"encoding/pem"
"errors"
"fmt"
"io/ioutil"
"k8s.io/apiserver/pkg/authentication/authenticator"
apiserverserviceaccount "k8s.io/apiserver/pkg/authentication/serviceaccount"
"k8s.io/apiserver/pkg/authentication/user"
"k8s.io/client-go/util/cert"
"k8s.io/kubernetes/pkg/api/v1"
jwt "github.com/dgrijalva/jwt-go"
"github.com/golang/glog"
)
const (
Issuer = "kubernetes/serviceaccount"
SubjectClaim = "sub"
IssuerClaim = "iss"
ServiceAccountNameClaim = "kubernetes.io/serviceaccount/service-account.name"
ServiceAccountUIDClaim = "kubernetes.io/serviceaccount/service-account.uid"
SecretNameClaim = "kubernetes.io/serviceaccount/secret.name"
NamespaceClaim = "kubernetes.io/serviceaccount/namespace"
)
// ServiceAccountTokenGetter defines functions to retrieve a named service account and secret
type ServiceAccountTokenGetter interface {
GetServiceAccount(namespace, name string) (*v1.ServiceAccount, error)
GetSecret(namespace, name string) (*v1.Secret, error)
}
type TokenGenerator interface {
// GenerateToken generates a token which will identify the given ServiceAccount.
// The returned token will be stored in the given (and yet-unpersisted) Secret.
GenerateToken(serviceAccount v1.ServiceAccount, secret v1.Secret) (string, error)
}
// ReadPrivateKey is a helper function for reading a private key from a PEM-encoded file
func ReadPrivateKey(file string) (interface{}, error) {
data, err := ioutil.ReadFile(file)
if err != nil {
return nil, err
}
key, err := cert.ParsePrivateKeyPEM(data)
if err != nil {
return nil, fmt.Errorf("error reading private key file %s: %v", file, err)
}
return key, nil
}
// ReadPublicKeys is a helper function for reading an array of rsa.PublicKey or ecdsa.PublicKey from a PEM-encoded file.
// Reads public keys from both public and private key files.
func ReadPublicKeys(file string) ([]interface{}, error) {
data, err := ioutil.ReadFile(file)
if err != nil {
return nil, err
}
keys, err := ReadPublicKeysFromPEM(data)
if err != nil {
return nil, fmt.Errorf("error reading public key file %s: %v", file, err)
}
return keys, nil
}
// ReadPublicKeysFromPEM is a helper function for reading an array of rsa.PublicKey or ecdsa.PublicKey from a PEM-encoded byte array.
// Reads public keys from both public and private key files.
func ReadPublicKeysFromPEM(data []byte) ([]interface{}, error) {
var block *pem.Block
keys := []interface{}{}
for {
// read the next block
block, data = pem.Decode(data)
if block == nil {
break
}
// get PEM bytes for just this block
blockData := pem.EncodeToMemory(block)
if privateKey, err := jwt.ParseRSAPrivateKeyFromPEM(blockData); err == nil {
keys = append(keys, &privateKey.PublicKey)
continue
}
if publicKey, err := jwt.ParseRSAPublicKeyFromPEM(blockData); err == nil {
keys = append(keys, publicKey)
continue
}
if privateKey, err := jwt.ParseECPrivateKeyFromPEM(blockData); err == nil {
keys = append(keys, &privateKey.PublicKey)
continue
}
if publicKey, err := jwt.ParseECPublicKeyFromPEM(blockData); err == nil {
keys = append(keys, publicKey)
continue
}
// tolerate non-key PEM blocks for backwards compatibility
// originally, only the first PEM block was parsed and expected to be a key block
}
if len(keys) == 0 {
return nil, fmt.Errorf("data does not contain a valid RSA or ECDSA key")
}
return keys, nil
}
// JWTTokenGenerator returns a TokenGenerator that generates signed JWT tokens, using the given privateKey.
// privateKey is a PEM-encoded byte array of a private RSA key.
// JWTTokenAuthenticator()
func JWTTokenGenerator(privateKey interface{}) TokenGenerator {
return &jwtTokenGenerator{privateKey}
}
type jwtTokenGenerator struct {
privateKey interface{}
}
func (j *jwtTokenGenerator) GenerateToken(serviceAccount v1.ServiceAccount, secret v1.Secret) (string, error) {
var method jwt.SigningMethod
switch privateKey := j.privateKey.(type) {
case *rsa.PrivateKey:
method = jwt.SigningMethodRS256
case *ecdsa.PrivateKey:
switch privateKey.Curve {
case elliptic.P256():
method = jwt.SigningMethodES256
case elliptic.P384():
method = jwt.SigningMethodES384
case elliptic.P521():
method = jwt.SigningMethodES512
default:
return "", fmt.Errorf("unknown private key curve, must be 256, 384, or 521")
}
default:
return "", fmt.Errorf("unknown private key type %T, must be *rsa.PrivateKey or *ecdsa.PrivateKey", j.privateKey)
}
token := jwt.New(method)
claims, _ := token.Claims.(jwt.MapClaims)
// Identify the issuer
claims[IssuerClaim] = Issuer
// Username
claims[SubjectClaim] = apiserverserviceaccount.MakeUsername(serviceAccount.Namespace, serviceAccount.Name)
// Persist enough structured info for the authenticator to be able to look up the service account and secret
claims[NamespaceClaim] = serviceAccount.Namespace
claims[ServiceAccountNameClaim] = serviceAccount.Name
claims[ServiceAccountUIDClaim] = serviceAccount.UID
claims[SecretNameClaim] = secret.Name
// Sign and get the complete encoded token as a string
return token.SignedString(j.privateKey)
}
// JWTTokenAuthenticator authenticates tokens as JWT tokens produced by JWTTokenGenerator
// Token signatures are verified using each of the given public keys until one works (allowing key rotation)
// If lookup is true, the service account and secret referenced as claims inside the token are retrieved and verified with the provided ServiceAccountTokenGetter
func JWTTokenAuthenticator(keys []interface{}, lookup bool, getter ServiceAccountTokenGetter) authenticator.Token {
return &jwtTokenAuthenticator{keys, lookup, getter}
}
type jwtTokenAuthenticator struct {
keys []interface{}
lookup bool
getter ServiceAccountTokenGetter
}
var errMismatchedSigningMethod = errors.New("invalid signing method")
func (j *jwtTokenAuthenticator) AuthenticateToken(token string) (user.Info, bool, error) {
var validationError error
for i, key := range j.keys {
// Attempt to verify with each key until we find one that works
parsedToken, err := jwt.Parse(token, func(token *jwt.Token) (interface{}, error) {
switch token.Method.(type) {
case *jwt.SigningMethodRSA:
if _, ok := key.(*rsa.PublicKey); ok {
return key, nil
}
return nil, errMismatchedSigningMethod
case *jwt.SigningMethodECDSA:
if _, ok := key.(*ecdsa.PublicKey); ok {
return key, nil
}
return nil, errMismatchedSigningMethod
default:
return nil, fmt.Errorf("Unexpected signing method: %v", token.Header["alg"])
}
})
if err != nil {
switch err := err.(type) {
case *jwt.ValidationError:
if (err.Errors & jwt.ValidationErrorMalformed) != 0 {
// Not a JWT, no point in continuing
return nil, false, nil
}
if (err.Errors & jwt.ValidationErrorSignatureInvalid) != 0 {
// Signature error, perhaps one of the other keys will verify the signature
// If not, we want to return this error
glog.V(4).Infof("Signature error (key %d): %v", i, err)
validationError = err
continue
}
// This key doesn't apply to the given signature type
// Perhaps one of the other keys will verify the signature
// If not, we want to return this error
if err.Inner == errMismatchedSigningMethod {
glog.V(4).Infof("Mismatched key type (key %d): %v", i, err)
validationError = err
continue
}
}
// Other errors should just return as errors
return nil, false, err
}
// If we get here, we have a token with a recognized signature
claims, _ := parsedToken.Claims.(jwt.MapClaims)
// Make sure we issued the token
iss, _ := claims[IssuerClaim].(string)
if iss != Issuer {
return nil, false, nil
}
// Make sure the claims we need exist
sub, _ := claims[SubjectClaim].(string)
if len(sub) == 0 {
return nil, false, errors.New("sub claim is missing")
}
namespace, _ := claims[NamespaceClaim].(string)
if len(namespace) == 0 {
return nil, false, errors.New("namespace claim is missing")
}
secretName, _ := claims[SecretNameClaim].(string)
if len(namespace) == 0 {
return nil, false, errors.New("secretName claim is missing")
}
serviceAccountName, _ := claims[ServiceAccountNameClaim].(string)
if len(serviceAccountName) == 0 {
return nil, false, errors.New("serviceAccountName claim is missing")
}
serviceAccountUID, _ := claims[ServiceAccountUIDClaim].(string)
if len(serviceAccountUID) == 0 {
return nil, false, errors.New("serviceAccountUID claim is missing")
}
subjectNamespace, subjectName, err := apiserverserviceaccount.SplitUsername(sub)
if err != nil || subjectNamespace != namespace || subjectName != serviceAccountName {
return nil, false, errors.New("sub claim is invalid")
}
if j.lookup {
// Make sure token hasn't been invalidated by deletion of the secret
secret, err := j.getter.GetSecret(namespace, secretName)
if err != nil {
glog.V(4).Infof("Could not retrieve token %s/%s for service account %s/%s: %v", namespace, secretName, namespace, serviceAccountName, err)
return nil, false, errors.New("Token has been invalidated")
}
if bytes.Compare(secret.Data[v1.ServiceAccountTokenKey], []byte(token)) != 0 {
glog.V(4).Infof("Token contents no longer matches %s/%s for service account %s/%s", namespace, secretName, namespace, serviceAccountName)
return nil, false, errors.New("Token does not match server's copy")
}
// Make sure service account still exists (name and UID)
serviceAccount, err := j.getter.GetServiceAccount(namespace, serviceAccountName)
if err != nil {
glog.V(4).Infof("Could not retrieve service account %s/%s: %v", namespace, serviceAccountName, err)
return nil, false, err
}
if string(serviceAccount.UID) != serviceAccountUID {
glog.V(4).Infof("Service account UID no longer matches %s/%s: %q != %q", namespace, serviceAccountName, string(serviceAccount.UID), serviceAccountUID)
return nil, false, fmt.Errorf("ServiceAccount UID (%s) does not match claim (%s)", serviceAccount.UID, serviceAccountUID)
}
}
return UserInfo(namespace, serviceAccountName, serviceAccountUID), true, nil
}
return nil, false, validationError
}