patch webhook authenticator to support token review with arbitrary audiences

pkg/kubeapiserver/authenticator/config.go

@@ -179,7 +179,7 @@ func (config Config) New() (authenticator.Request, *spec.SecurityDefinitions, er
 		tokenAuthenticators = append(tokenAuthenticators, oidcAuth)
 	}
 	if len(config.WebhookTokenAuthnConfigFile) > 0 {
-		webhookTokenAuth, err := newWebhookTokenAuthenticator(config.WebhookTokenAuthnConfigFile, config.WebhookTokenAuthnCacheTTL)
+		webhookTokenAuth, err := newWebhookTokenAuthenticator(config.WebhookTokenAuthnConfigFile, config.WebhookTokenAuthnCacheTTL, config.APIAudiences)
 		if err != nil {
 			return nil, nil, err
 		}
@@ -318,8 +318,8 @@ func newAuthenticatorFromClientCAFile(clientCAFile string) (authenticator.Reques
 	return x509.New(opts, x509.CommonNameUserConversion), nil
 }
 
-func newWebhookTokenAuthenticator(webhookConfigFile string, ttl time.Duration) (authenticator.Token, error) {
-	webhookTokenAuthenticator, err := webhook.New(webhookConfigFile)
+func newWebhookTokenAuthenticator(webhookConfigFile string, ttl time.Duration, implicitAuds authenticator.Audiences) (authenticator.Token, error) {
+	webhookTokenAuthenticator, err := webhook.New(webhookConfigFile, implicitAuds)
 	if err != nil {
 		return nil, err
 	}

staging/src/k8s.io/apiserver/pkg/authentication/authenticatorfactory/delegating.go

@@ -51,6 +51,8 @@ type DelegatingAuthenticatorConfig struct {
 	// ClientCAFile is the CA bundle file used to authenticate client certificates
 	ClientCAFile string
 
+	APIAudiences authenticator.Audiences
+
 	RequestHeaderConfig *RequestHeaderConfig
 }
 
@@ -86,7 +88,7 @@ func (c DelegatingAuthenticatorConfig) New() (authenticator.Request, *spec.Secur
 	}
 
 	if c.TokenAccessReviewClient != nil {
-		tokenAuth, err := webhooktoken.NewFromInterface(c.TokenAccessReviewClient)
+		tokenAuth, err := webhooktoken.NewFromInterface(c.TokenAccessReviewClient, c.APIAudiences)
 		if err != nil {
 			return nil, nil, err
 		}

staging/src/k8s.io/apiserver/plugin/pkg/authenticator/token/webhook/webhook.go

@@ -21,8 +21,6 @@ import (
 	"context"
 	"time"
 
-	"k8s.io/klog"
-
 	authentication "k8s.io/api/authentication/v1beta1"
 	"k8s.io/apimachinery/pkg/runtime"
 	"k8s.io/apimachinery/pkg/runtime/schema"
@@ -31,6 +29,7 @@ import (
 	"k8s.io/apiserver/pkg/util/webhook"
 	"k8s.io/client-go/kubernetes/scheme"
 	authenticationclient "k8s.io/client-go/kubernetes/typed/authentication/v1beta1"
+	"k8s.io/klog"
 )
 
 var (
@@ -45,38 +44,58 @@ var _ authenticator.Token = (*WebhookTokenAuthenticator)(nil)
 type WebhookTokenAuthenticator struct {
 	tokenReview    authenticationclient.TokenReviewInterface
 	initialBackoff time.Duration
+	implicitAuds   authenticator.Audiences
 }
 
 // NewFromInterface creates a webhook authenticator using the given tokenReview
 // client. It is recommend to wrap this authenticator with the token cache
 // authenticator implemented in
 // k8s.io/apiserver/pkg/authentication/token/cache.
-func NewFromInterface(tokenReview authenticationclient.TokenReviewInterface) (*WebhookTokenAuthenticator, error) {
-	return newWithBackoff(tokenReview, retryBackoff)
+func NewFromInterface(tokenReview authenticationclient.TokenReviewInterface, implicitAuds authenticator.Audiences) (*WebhookTokenAuthenticator, error) {
+	return newWithBackoff(tokenReview, retryBackoff, implicitAuds)
 }
 
-// New creates a new WebhookTokenAuthenticator from the provided kubeconfig file.
-func New(kubeConfigFile string) (*WebhookTokenAuthenticator, error) {
+// New creates a new WebhookTokenAuthenticator from the provided kubeconfig
+// file. It is recommend to wrap this authenticator with the token cache
+// authenticator implemented in
+// k8s.io/apiserver/pkg/authentication/token/cache.
+func New(kubeConfigFile string, implicitAuds authenticator.Audiences) (*WebhookTokenAuthenticator, error) {
 	tokenReview, err := tokenReviewInterfaceFromKubeconfig(kubeConfigFile)
 	if err != nil {
 		return nil, err
 	}
-	return newWithBackoff(tokenReview, retryBackoff)
+	return newWithBackoff(tokenReview, retryBackoff, implicitAuds)
 }
 
 // newWithBackoff allows tests to skip the sleep.
-func newWithBackoff(tokenReview authenticationclient.TokenReviewInterface, initialBackoff time.Duration) (*WebhookTokenAuthenticator, error) {
-	return &WebhookTokenAuthenticator{tokenReview, initialBackoff}, nil
+func newWithBackoff(tokenReview authenticationclient.TokenReviewInterface, initialBackoff time.Duration, implicitAuds authenticator.Audiences) (*WebhookTokenAuthenticator, error) {
+	return &WebhookTokenAuthenticator{tokenReview, initialBackoff, implicitAuds}, nil
 }
 
 // AuthenticateToken implements the authenticator.Token interface.
 func (w *WebhookTokenAuthenticator) AuthenticateToken(ctx context.Context, token string) (*authenticator.Response, bool, error) {
+	// We take implicit audiences of the API server at WebhookTokenAuthenticator
+	// construction time. The outline of how we validate audience here is:
+	//
+	// * if the ctx is not audience limited, don't do any audience validation.
+	// * if ctx is audience-limited, add the audiences to the tokenreview spec
+	//   * if the tokenreview returns with audiences in the status that intersect
+	//     with the audiences in the ctx, copy into the response and return success
+	//   * if the tokenreview returns without an audience in the status, ensure
+	//     the ctx audiences intersect with the implicit audiences, and set the
+	//     intersection in the response.
+	//   * otherwise return unauthenticated.
+	wantAuds, checkAuds := authenticator.AudiencesFrom(ctx)
 	r := &authentication.TokenReview{
-		Spec: authentication.TokenReviewSpec{Token: token},
+		Spec: authentication.TokenReviewSpec{
+			Token:     token,
+			Audiences: wantAuds,
+		},
 	}
 	var (
 		result *authentication.TokenReview
 		err    error
+		auds   authenticator.Audiences
 	)
 	webhook.WithExponentialBackoff(w.initialBackoff, func() error {
 		result, err = w.tokenReview.Create(r)
@@ -87,6 +106,18 @@ func (w *WebhookTokenAuthenticator) AuthenticateToken(ctx context.Context, token
 		klog.Errorf("Failed to make webhook authenticator request: %v", err)
 		return nil, false, err
 	}
+
+	if checkAuds {
+		gotAuds := w.implicitAuds
+		if len(result.Status.Audiences) > 0 {
+			gotAuds = result.Status.Audiences
+		}
+		auds = wantAuds.Intersect(gotAuds)
+		if len(auds) == 0 {
+			return nil, false, nil
+		}
+	}
+
 	r.Status = result.Status
 	if !r.Status.Authenticated {
 		return nil, false, nil
@@ -107,6 +138,7 @@ func (w *WebhookTokenAuthenticator) AuthenticateToken(ctx context.Context, token
 			Groups: r.Status.User.Groups,
 			Extra:  extra,
 		},
+		Audiences: auds,
 	}, true, nil
 }
 

staging/src/k8s.io/apiserver/plugin/pkg/authenticator/token/webhook/webhook_test.go

@@ -39,6 +39,8 @@ import (
 	"k8s.io/client-go/tools/clientcmd/api/v1"
 )
 
+var apiAuds = authenticator.Audiences{"api"}
+
 // Service mocks a remote authentication service.
 type Service interface {
 	// Review looks at the TokenReviewSpec and provides an authentication
@@ -105,6 +107,7 @@ func NewTestServer(s Service, cert, key, caCert []byte) (*httptest.Server, error
 		type status struct {
 			Authenticated bool     `json:"authenticated"`
 			User          userInfo `json:"user"`
+			Audiences     []string `json:"audiences"`
 		}
 
 		var extra map[string][]string
@@ -130,6 +133,7 @@ func NewTestServer(s Service, cert, key, caCert []byte) (*httptest.Server, error
 					Groups:   review.Status.User.Groups,
 					Extra:    extra,
 				},
+				review.Status.Audiences,
 			},
 		}
 		w.Header().Set("Content-Type", "application/json")
@@ -168,7 +172,7 @@ func (m *mockService) HTTPStatusCode() int { return m.statusCode }
 
 // newTokenAuthenticator creates a temporary kubeconfig file from the provided
 // arguments and attempts to load a new WebhookTokenAuthenticator from it.
-func newTokenAuthenticator(serverURL string, clientCert, clientKey, ca []byte, cacheTime time.Duration) (authenticator.Token, error) {
+func newTokenAuthenticator(serverURL string, clientCert, clientKey, ca []byte, cacheTime time.Duration, implicitAuds authenticator.Audiences) (authenticator.Token, error) {
 	tempfile, err := ioutil.TempFile("", "")
 	if err != nil {
 		return nil, err
@@ -196,7 +200,7 @@ func newTokenAuthenticator(serverURL string, clientCert, clientKey, ca []byte, c
 		return nil, err
 	}
 
-	authn, err := newWithBackoff(c, 0)
+	authn, err := newWithBackoff(c, 0, implicitAuds)
 	if err != nil {
 		return nil, err
 	}
@@ -257,7 +261,7 @@ func TestTLSConfig(t *testing.T) {
 			}
 			defer server.Close()
 
-			wh, err := newTokenAuthenticator(server.URL, tt.clientCert, tt.clientKey, tt.clientCA, 0)
+			wh, err := newTokenAuthenticator(server.URL, tt.clientCert, tt.clientKey, tt.clientCA, 0, nil)
 			if err != nil {
 				t.Errorf("%s: failed to create client: %v", tt.test, err)
 				return
@@ -312,23 +316,21 @@ func TestWebhookTokenAuthenticator(t *testing.T) {
 	}
 	defer s.Close()
 
-	wh, err := newTokenAuthenticator(s.URL, clientCert, clientKey, caCert, 0)
-	if err != nil {
-		t.Fatal(err)
-	}
-
 	expTypeMeta := metav1.TypeMeta{
 		APIVersion: "authentication.k8s.io/v1beta1",
 		Kind:       "TokenReview",
 	}
 
 	tests := []struct {
+		description           string
+		implicitAuds, reqAuds authenticator.Audiences
 		serverResponse        v1beta1.TokenReviewStatus
 		expectedAuthenticated bool
 		expectedUser          *user.DefaultInfo
+		expectedAuds          authenticator.Audiences
 	}{
-		// Successful response should pass through all user info.
 		{
+			description: "successful response should pass through all user info.",
 			serverResponse: v1beta1.TokenReviewStatus{
 				Authenticated: true,
 				User: v1beta1.UserInfo{
@@ -341,6 +343,7 @@ func TestWebhookTokenAuthenticator(t *testing.T) {
 			},
 		},
 		{
+			description: "successful response should pass through all user info.",
 			serverResponse: v1beta1.TokenReviewStatus{
 				Authenticated: true,
 				User: v1beta1.UserInfo{
@@ -358,8 +361,8 @@ func TestWebhookTokenAuthenticator(t *testing.T) {
 				Extra:  map[string][]string{"foo": {"bar", "baz"}},
 			},
 		},
-		// Unauthenticated shouldn't even include extra provided info.
 		{
+			description: "unauthenticated shouldn't even include extra provided info.",
 			serverResponse: v1beta1.TokenReviewStatus{
 				Authenticated: false,
 				User: v1beta1.UserInfo{
@@ -372,37 +375,151 @@ func TestWebhookTokenAuthenticator(t *testing.T) {
 			expectedUser:          nil,
 		},
 		{
+			description: "unauthenticated shouldn't even include extra provided info.",
 			serverResponse: v1beta1.TokenReviewStatus{
 				Authenticated: false,
 			},
 			expectedAuthenticated: false,
 			expectedUser:          nil,
 		},
+		{
+			description:  "good audience",
+			implicitAuds: apiAuds,
+			reqAuds:      apiAuds,
+			serverResponse: v1beta1.TokenReviewStatus{
+				Authenticated: true,
+				User: v1beta1.UserInfo{
+					Username: "somebody",
+				},
+			},
+			expectedAuthenticated: true,
+			expectedUser: &user.DefaultInfo{
+				Name: "somebody",
+			},
+			expectedAuds: apiAuds,
+		},
+		{
+			description:  "good audience",
+			implicitAuds: append(apiAuds, "other"),
+			reqAuds:      apiAuds,
+			serverResponse: v1beta1.TokenReviewStatus{
+				Authenticated: true,
+				User: v1beta1.UserInfo{
+					Username: "somebody",
+				},
+			},
+			expectedAuthenticated: true,
+			expectedUser: &user.DefaultInfo{
+				Name: "somebody",
+			},
+			expectedAuds: apiAuds,
+		},
+		{
+			description:  "bad audiences",
+			implicitAuds: apiAuds,
+			reqAuds:      authenticator.Audiences{"other"},
+			serverResponse: v1beta1.TokenReviewStatus{
+				Authenticated: false,
+			},
+			expectedAuthenticated: false,
+		},
+		{
+			description:  "bad audiences",
+			implicitAuds: apiAuds,
+			reqAuds:      authenticator.Audiences{"other"},
+			// webhook authenticator hasn't been upgraded to support audience.
+			serverResponse: v1beta1.TokenReviewStatus{
+				Authenticated: true,
+				User: v1beta1.UserInfo{
+					Username: "somebody",
+				},
+			},
+			expectedAuthenticated: false,
+		},
+		{
+			description:  "audience aware backend",
+			implicitAuds: apiAuds,
+			reqAuds:      apiAuds,
+			serverResponse: v1beta1.TokenReviewStatus{
+				Authenticated: true,
+				User: v1beta1.UserInfo{
+					Username: "somebody",
+				},
+				Audiences: []string(apiAuds),
+			},
+			expectedAuthenticated: true,
+			expectedUser: &user.DefaultInfo{
+				Name: "somebody",
+			},
+			expectedAuds: apiAuds,
+		},
+		{
+			description: "audience aware backend",
+			serverResponse: v1beta1.TokenReviewStatus{
+				Authenticated: true,
+				User: v1beta1.UserInfo{
+					Username: "somebody",
+				},
+				Audiences: []string(apiAuds),
+			},
+			expectedAuthenticated: true,
+			expectedUser: &user.DefaultInfo{
+				Name: "somebody",
+			},
+		},
+		{
+			description:  "audience aware backend",
+			implicitAuds: apiAuds,
+			reqAuds:      apiAuds,
+			serverResponse: v1beta1.TokenReviewStatus{
+				Authenticated: true,
+				User: v1beta1.UserInfo{
+					Username: "somebody",
+				},
+				Audiences: []string{"other"},
+			},
+			expectedAuthenticated: false,
+		},
 	}
 	token := "my-s3cr3t-t0ken"
-	for i, tt := range tests {
-		serv.response = tt.serverResponse
-		resp, authenticated, err := wh.AuthenticateToken(context.Background(), token)
-		if err != nil {
-			t.Errorf("case %d: authentication failed: %v", i, err)
-			continue
-		}
-		if serv.lastRequest.Spec.Token != token {
-			t.Errorf("case %d: Server did not see correct token. Got %q, expected %q.",
-				i, serv.lastRequest.Spec.Token, token)
-		}
-		if !reflect.DeepEqual(serv.lastRequest.TypeMeta, expTypeMeta) {
-			t.Errorf("case %d: Server did not see correct TypeMeta. Got %v, expected %v",
-				i, serv.lastRequest.TypeMeta, expTypeMeta)
-		}
-		if authenticated != tt.expectedAuthenticated {
-			t.Errorf("case %d: Plugin returned incorrect authentication response. Got %t, expected %t.",
-				i, authenticated, tt.expectedAuthenticated)
-		}
-		if resp != nil && tt.expectedUser != nil && !reflect.DeepEqual(resp.User, tt.expectedUser) {
-			t.Errorf("case %d: Plugin returned incorrect user. Got %#v, expected %#v",
-				i, resp.User, tt.expectedUser)
-		}
+	for _, tt := range tests {
+		t.Run(tt.description, func(t *testing.T) {
+			wh, err := newTokenAuthenticator(s.URL, clientCert, clientKey, caCert, 0, tt.implicitAuds)
+			if err != nil {
+				t.Fatal(err)
+			}
+
+			ctx := context.Background()
+			if tt.reqAuds != nil {
+				ctx = authenticator.WithAudiences(ctx, tt.reqAuds)
+			}
+
+			serv.response = tt.serverResponse
+			resp, authenticated, err := wh.AuthenticateToken(ctx, token)
+			if err != nil {
+				t.Fatalf("authentication failed: %v", err)
+			}
+			if serv.lastRequest.Spec.Token != token {
+				t.Errorf("Server did not see correct token. Got %q, expected %q.",
+					serv.lastRequest.Spec.Token, token)
+			}
+			if !reflect.DeepEqual(serv.lastRequest.TypeMeta, expTypeMeta) {
+				t.Errorf("Server did not see correct TypeMeta. Got %v, expected %v",
+					serv.lastRequest.TypeMeta, expTypeMeta)
+			}
+			if authenticated != tt.expectedAuthenticated {
+				t.Errorf("Plugin returned incorrect authentication response. Got %t, expected %t.",
+					authenticated, tt.expectedAuthenticated)
+			}
+			if resp != nil && tt.expectedUser != nil && !reflect.DeepEqual(resp.User, tt.expectedUser) {
+				t.Errorf("Plugin returned incorrect user. Got %#v, expected %#v",
+					resp.User, tt.expectedUser)
+			}
+			if resp != nil && tt.expectedAuds != nil && !reflect.DeepEqual(resp.Audiences, tt.expectedAuds) {
+				t.Errorf("Plugin returned incorrect audiences. Got %#v, expected %#v",
+					resp.Audiences, tt.expectedAuds)
+			}
+		})
 	}
 }
 
@@ -440,7 +557,7 @@ func TestWebhookCacheAndRetry(t *testing.T) {
 	defer s.Close()
 
 	// Create an authenticator that caches successful responses "forever" (100 days).
-	wh, err := newTokenAuthenticator(s.URL, clientCert, clientKey, caCert, 2400*time.Hour)
+	wh, err := newTokenAuthenticator(s.URL, clientCert, clientKey, caCert, 2400*time.Hour, nil)
 	if err != nil {
 		t.Fatal(err)
 	}

test/integration/auth/auth_test.go

@@ -85,7 +85,7 @@ func getTestWebhookTokenAuth(serverURL string) (authenticator.Request, error) {
 	if err := json.NewEncoder(kubecfgFile).Encode(config); err != nil {
 		return nil, err
 	}
-	webhookTokenAuth, err := webhook.New(kubecfgFile.Name())
+	webhookTokenAuth, err := webhook.New(kubecfgFile.Name(), nil)
 	if err != nil {
 		return nil, err
 	}