Use JWKSet to get the GCP keys.

authority/provisioner/gcp.go

@@ -47,7 +47,7 @@ type GCP struct {
 	ServiceAccounts []string `json:"serviceAccounts"`
 	Claims          *Claims  `json:"claims,omitempty"`
 	claimer         *Claimer
-	certStore       *keyStore
+	keyStore        *keyStore
 }
 
 // GetID returns the provisioner unique identifier. The name should uniquely
@@ -103,8 +103,8 @@ func (p *GCP) Init(config Config) error {
 	if p.claimer, err = NewClaimer(p.Claims, config.Claims); err != nil {
 		return err
 	}
-	// Initialize certificate store
-	p.certStore, err = newCertificateStore("https://www.googleapis.com/oauth2/v1/certs")
+	// Initialize key store
+	p.keyStore, err = newKeyStore("https://www.googleapis.com/oauth2/v3/certs")
 	if err != nil {
 		return err
 	}
@@ -185,15 +185,19 @@ func (p *GCP) authorizeToken(token string) (*gcpPayload, error) {
 	if len(jwt.Headers) == 0 {
 		return nil, errors.New("error parsing token: header is missing")
 	}
-	kid := jwt.Headers[0].KeyID
-	cert := p.certStore.GetCertificate(kid)
-	if cert == nil {
-		return nil, errors.Errorf("failed to validate payload: cannot find certificate for kid %s", kid)
-	}
 
+	var found bool
 	var claims gcpPayload
-	if err = jwt.Claims(cert.PublicKey, &claims); err != nil {
-		return nil, errors.Wrap(err, "error parsing claims")
+	kid := jwt.Headers[0].KeyID
+	keys := p.keyStore.Get(kid)
+	for _, key := range keys {
+		if err := jwt.Claims(key, &claims); err == nil {
+			found = true
+			break
+		}
+	}
+	if !found {
+		return nil, errors.Errorf("failed to validate payload: cannot find certificate for kid %s", kid)
 	}
 
 	// According to "rfc7519 JSON Web Token" acceptable skew should be no

authority/provisioner/keystore.go

@@ -1,9 +1,7 @@
 package provisioner
 
 import (
-	"crypto/x509"
 	"encoding/json"
-	"encoding/pem"
 	"math/rand"
 	"net/http"
 	"regexp"
@@ -22,29 +20,10 @@ const (
 
 var maxAgeRegex = regexp.MustCompile("max-age=([0-9]*)")
 
-type oauth2Certificate struct {
-	ID          string
-	Certificate *x509.Certificate
-}
-
-type oauth2CertificateSet struct {
-	Certificates []oauth2Certificate
-}
-
-func (s oauth2CertificateSet) Get(id string) *x509.Certificate {
-	for _, c := range s.Certificates {
-		if c.ID == id {
-			return c.Certificate
-		}
-	}
-	return nil
-}
-
 type keyStore struct {
 	sync.RWMutex
 	uri    string
 	keySet jose.JSONWebKeySet
-	certSet oauth2CertificateSet
 	timer  *time.Timer
 	expiry time.Time
 	jitter time.Duration
@@ -66,22 +45,6 @@ func newKeyStore(uri string) (*keyStore, error) {
 	return ks, nil
 }
 
-func newCertificateStore(uri string) (*keyStore, error) {
-	certs, age, err := getOauth2Certificates(uri)
-	if err != nil {
-		return nil, err
-	}
-	ks := &keyStore{
-		uri:     uri,
-		certSet: certs,
-		expiry:  getExpirationTime(age),
-		jitter:  getCacheJitter(age),
-	}
-	next := ks.nextReloadDuration(age)
-	ks.timer = time.AfterFunc(next, ks.reloadCertificates)
-	return ks, nil
-}
-
 func (ks *keyStore) Close() {
 	ks.timer.Stop()
 }
@@ -99,19 +62,6 @@ func (ks *keyStore) Get(kid string) (keys []jose.JSONWebKey) {
 	return
 }
 
-func (ks *keyStore) GetCertificate(kid string) (cert *x509.Certificate) {
-	ks.RLock()
-	// Force reload if expiration has passed
-	if time.Now().After(ks.expiry) {
-		ks.RUnlock()
-		ks.reloadCertificates()
-		ks.RLock()
-	}
-	cert = ks.certSet.Get(kid)
-	ks.RUnlock()
-	return
-}
-
 func (ks *keyStore) reload() {
 	var next time.Duration
 	keys, age, err := getKeysFromJWKsURI(ks.uri)
@@ -131,25 +81,6 @@ func (ks *keyStore) reload() {
 	ks.Unlock()
 }
 
-func (ks *keyStore) reloadCertificates() {
-	var next time.Duration
-	certs, age, err := getOauth2Certificates(ks.uri)
-	if err != nil {
-		next = ks.nextReloadDuration(ks.jitter / 2)
-	} else {
-		ks.Lock()
-		ks.certSet = certs
-		ks.expiry = getExpirationTime(age)
-		ks.jitter = getCacheJitter(age)
-		next = ks.nextReloadDuration(age)
-		ks.Unlock()
-	}
-
-	ks.Lock()
-	ks.timer.Reset(next)
-	ks.Unlock()
-}
-
 func (ks *keyStore) nextReloadDuration(age time.Duration) time.Duration {
 	n := rand.Int63n(int64(ks.jitter))
 	age -= time.Duration(n)
@@ -172,34 +103,6 @@ func getKeysFromJWKsURI(uri string) (jose.JSONWebKeySet, time.Duration, error) {
 	return keys, getCacheAge(resp.Header.Get("cache-control")), nil
 }
 
-func getOauth2Certificates(uri string) (oauth2CertificateSet, time.Duration, error) {
-	var certs oauth2CertificateSet
-	resp, err := http.Get(uri)
-	if err != nil {
-		return certs, 0, errors.Wrapf(err, "failed to connect to %s", uri)
-	}
-	defer resp.Body.Close()
-	m := make(map[string]string)
-	if err := json.NewDecoder(resp.Body).Decode(&m); err != nil {
-		return certs, 0, errors.Wrapf(err, "error reading %s", uri)
-	}
-	for k, v := range m {
-		block, _ := pem.Decode([]byte(v))
-		if block == nil || block.Type != "CERTIFICATE" {
-			return certs, 0, errors.Wrapf(err, "error parsing certificate %s from %s", k, uri)
-		}
-		cert, err := x509.ParseCertificate(block.Bytes)
-		if err != nil {
-			return certs, 0, errors.Wrapf(err, "error parsing certificate %s from %s", k, uri)
-		}
-		certs.Certificates = append(certs.Certificates, oauth2Certificate{
-			ID:          k,
-			Certificate: cert,
-		})
-	}
-	return certs, getCacheAge(resp.Header.Get("cache-control")), nil
-}
-
 func getCacheAge(cacheControl string) time.Duration {
 	age := defaultCacheAge
 	if len(cacheControl) > 0 {