Use duration and renewBefore to control API cert rotation

These configuration knobs are much more human-understandable than the
previous percentage-based threshold flag.

We now allow users to set the lifetime of the serving cert via a ConfigMap.
Previously this was hardcoded to 1 year.

Signed-off-by: Andrew Keesler <akeesler@vmware.com>

internal/controller/apicerts/certs_expirer.go

@@ -28,24 +28,20 @@ type certsExpirerController struct {
 	k8sClient      kubernetes.Interface
 	secretInformer corev1informers.SecretInformer
 
-	// ageThreshold is a percentage (i.e., a real number between 0 and 1,
-	// inclusive) indicating the point in a certificate's lifetime where this
-	// controller will start to try to rotate it.
-	//
-	// Said another way, once ageThreshold % of a certificate's lifetime has
-	// passed, this controller will try to delete it to force a new certificate
-	// to be created.
-	ageThreshold float32
+	// renewBefore is the amount of time after the cert's issuance where
+	// this controller will start to try to rotate it.
+	renewBefore time.Duration
 }
 
 // NewCertsExpirerController returns a controller.Controller that will delete a
-// CA once it gets within some threshold of its expiration time.
+// certificate secret once it gets within some threshold of its expiration time. The
+// deletion forces rotation of the secret with the help of other controllers.
 func NewCertsExpirerController(
 	namespace string,
 	k8sClient kubernetes.Interface,
 	secretInformer corev1informers.SecretInformer,
 	withInformer pinnipedcontroller.WithInformerOptionFunc,
-	ageThreshold float32,
+	renewBefore time.Duration,
 ) controller.Controller {
 	return controller.New(
 		controller.Config{
@@ -54,7 +50,7 @@ func NewCertsExpirerController(
 				namespace:      namespace,
 				k8sClient:      k8sClient,
 				secretInformer: secretInformer,
-				ageThreshold:   ageThreshold,
+				renewBefore:    renewBefore,
 			},
 		},
 		withInformer(
@@ -77,20 +73,19 @@ func (c *certsExpirerController) Sync(ctx controller.Context) error {
 		return nil
 	}
 
-	notBefore, notAfter, err := getCABounds(secret)
+	notBefore, notAfter, err := getCertBounds(secret)
 	if err != nil {
-		// If we can't get the CA, then really all we can do is log something, since
-		// if we returned an error then the controller lib would just call us again
-		// and again, which would probably yield the same results.
+		// If we can't read the cert, then really all we can do is log something,
+		// since if we returned an error then the controller lib would just call us
+		// again and again, which would probably yield the same results.
 		klog.Warningf("certsExpirerController Sync() found that the secret is malformed: %s", err.Error())
 		return nil
 	}
 
-	caLifetime := notAfter.Sub(notBefore)
-	caAge := time.Since(notBefore)
-	thresholdDelta := (float32(caAge) / float32(caLifetime)) - c.ageThreshold
-	klog.Infof("certsExpirerController Sync() found a CA age threshold delta of %.9g", thresholdDelta)
-	if thresholdDelta > 0 {
+	certAge := time.Since(notBefore)
+	renewDelta := certAge - c.renewBefore
+	klog.Infof("certsExpirerController Sync() found a renew delta of %s", renewDelta)
+	if renewDelta >= 0 || time.Now().After(notAfter) {
 		err := c.k8sClient.
 			CoreV1().
 			Secrets(c.namespace).
@@ -105,24 +100,25 @@ func (c *certsExpirerController) Sync(ctx controller.Context) error {
 	return nil
 }
 
-// getCABounds returns the NotBefore and NotAfter fields of the CA certificate
-// in the provided secret, or an error. Not that it expects the provided secret
-// to contain the well-known data keys from this package (see certs_manager.go).
-func getCABounds(secret *corev1.Secret) (time.Time, time.Time, error) {
-	caPEM := secret.Data[caCertificateSecretKey]
-	if caPEM == nil {
-		return time.Time{}, time.Time{}, constable.Error("failed to find CA")
+// getCertBounds returns the NotBefore and NotAfter fields of the TLS
+// certificate in the provided secret, or an error. Not that it expects the
+// provided secret to contain the well-known data keys from this package (see
+// certs_manager.go).
+func getCertBounds(secret *corev1.Secret) (time.Time, time.Time, error) {
+	certPEM := secret.Data[tlsCertificateChainSecretKey]
+	if certPEM == nil {
+		return time.Time{}, time.Time{}, constable.Error("failed to find certificate")
 	}
 
-	caBlock, _ := pem.Decode(caPEM)
-	if caBlock == nil {
-		return time.Time{}, time.Time{}, constable.Error("failed to decode CA PEM")
+	certBlock, _ := pem.Decode(certPEM)
+	if certBlock == nil {
+		return time.Time{}, time.Time{}, constable.Error("failed to decode certificate PEM")
 	}
 
-	caCrt, err := x509.ParseCertificate(caBlock.Bytes)
+	cert, err := x509.ParseCertificate(certBlock.Bytes)
 	if err != nil {
-		return time.Time{}, time.Time{}, fmt.Errorf("failed to parse CA: %w", err)
+		return time.Time{}, time.Time{}, fmt.Errorf("failed to parse certificate: %w", err)
 	}
 
-	return caCrt.NotBefore, caCrt.NotAfter, nil
+	return cert.NotBefore, cert.NotAfter, nil
 }

internal/controller/apicerts/certs_expirer_test.go

@@ -96,7 +96,7 @@ func TestExpirerControllerFilters(t *testing.T) {
 				nil, // k8sClient, not needed
 				secretsInformer,
 				withInformer.WithInformer,
-				0, // ageThreshold, not needed
+				0, // renewBefore, not needed
 			)
 
 			unrelated := corev1.Secret{}
@@ -114,7 +114,7 @@ func TestExpirerControllerSync(t *testing.T) {
 
 	tests := []struct {
 		name                string
-		ageThreshold        float32
+		renewBefore         time.Duration
 		fillSecretData      func(*testing.T, map[string][]byte)
 		configKubeAPIClient func(*kubernetesfake.Clientset)
 		wantDelete          bool
@@ -131,46 +131,61 @@ func TestExpirerControllerSync(t *testing.T) {
 		},
 		{
 			name:        "lifetime below threshold",
-			ageThreshold: 0.7,
+			renewBefore: 7 * time.Hour,
 			fillSecretData: func(t *testing.T, m map[string][]byte) {
-				caPEM, err := testutil.CreateCertificate(
+				certPEM, err := testutil.CreateCertificate(
 					time.Now().Add(-5*time.Hour),
 					time.Now().Add(5*time.Hour),
 				)
 				require.NoError(t, err)
 
-				// See cert_manager.go for this constant.
-				m["caCertificate"] = caPEM
+				// See certs_manager.go for this constant.
+				m["tlsCertificateChain"] = certPEM
 			},
 			wantDelete: false,
 		},
 		{
 			name:        "lifetime above threshold",
-			ageThreshold: 0.3,
+			renewBefore: 3 * time.Hour,
 			fillSecretData: func(t *testing.T, m map[string][]byte) {
-				caPEM, err := testutil.CreateCertificate(
+				certPEM, err := testutil.CreateCertificate(
 					time.Now().Add(-5*time.Hour),
 					time.Now().Add(5*time.Hour),
 				)
 				require.NoError(t, err)
 
-				// See cert_manager.go for this constant.
-				m["caCertificate"] = caPEM
+				// See certs_manager.go for this constant.
+				m["tlsCertificateChain"] = certPEM
+			},
+			wantDelete: true,
+		},
+		{
+			name:        "cert expired",
+			renewBefore: 3 * time.Hour,
+			fillSecretData: func(t *testing.T, m map[string][]byte) {
+				certPEM, err := testutil.CreateCertificate(
+					time.Now().Add(-2*time.Hour),
+					time.Now().Add(-1*time.Hour),
+				)
+				require.NoError(t, err)
+
+				// See certs_manager.go for this constant.
+				m["tlsCertificateChain"] = certPEM
 			},
 			wantDelete: true,
 		},
 		{
 			name:        "delete failure",
-			ageThreshold: 0.3,
+			renewBefore: 3 * time.Hour,
 			fillSecretData: func(t *testing.T, m map[string][]byte) {
-				caPEM, err := testutil.CreateCertificate(
+				certPEM, err := testutil.CreateCertificate(
 					time.Now().Add(-5*time.Hour),
 					time.Now().Add(5*time.Hour),
 				)
 				require.NoError(t, err)
 
-				// See cert_manager.go for this constant.
-				m["caCertificate"] = caPEM
+				// See certs_manager.go for this constant.
+				m["tlsCertificateChain"] = certPEM
 			},
 			configKubeAPIClient: func(c *kubernetesfake.Clientset) {
 				c.PrependReactor("delete", "secrets", func(_ kubetesting.Action) (bool, runtime.Object, error) {
@@ -185,8 +200,8 @@ func TestExpirerControllerSync(t *testing.T) {
 				privateKey, err := rsa.GenerateKey(rand.Reader, 2048)
 				require.NoError(t, err)
 
-				// See cert_manager.go for this constant.
-				m["caCertificate"] = x509.MarshalPKCS1PrivateKey(privateKey)
+				// See certs_manager.go for this constant.
+				m["tlsCertificateChain"] = x509.MarshalPKCS1PrivateKey(privateKey)
 			},
 			wantDelete: false,
 		},
@@ -205,7 +220,7 @@ func TestExpirerControllerSync(t *testing.T) {
 			}
 
 			kubeInformerClient := kubernetesfake.NewSimpleClientset()
-			name := "api-serving-cert" // See cert_manager.go.
+			name := "api-serving-cert" // See certs_manager.go.
 			namespace := "some-namespace"
 			if test.fillSecretData != nil {
 				secret := &corev1.Secret{
@@ -231,7 +246,7 @@ func TestExpirerControllerSync(t *testing.T) {
 				kubeAPIClient,
 				kubeInformers.Core().V1().Secrets(),
 				controller.WithInformer,
-				test.ageThreshold,
+				test.renewBefore,
 			)
 
 			// Must start informers before calling TestRunSynchronously().

internal/controller/apicerts/certs_manager.go

@@ -36,6 +36,10 @@ type certsManagerController struct {
 	k8sClient        kubernetes.Interface
 	aggregatorClient aggregatorclient.Interface
 	secretInformer   corev1informers.SecretInformer
+
+	// certDuration is the lifetime of the serving certificate that this
+	// controller will use when issuing the serving certificate.
+	certDuration time.Duration
 }
 
 func NewCertsManagerController(
@@ -45,6 +49,7 @@ func NewCertsManagerController(
 	secretInformer corev1informers.SecretInformer,
 	withInformer pinnipedcontroller.WithInformerOptionFunc,
 	withInitialEvent pinnipedcontroller.WithInitialEventOptionFunc,
+	certDuration time.Duration,
 ) controller.Controller {
 	return controller.New(
 		controller.Config{
@@ -54,6 +59,7 @@ func NewCertsManagerController(
 				k8sClient:        k8sClient,
 				aggregatorClient: aggregatorClient,
 				secretInformer:   secretInformer,
+				certDuration:     certDuration,
 			},
 		},
 		withInformer(
@@ -95,7 +101,7 @@ func (c *certsManagerController) Sync(ctx controller.Context) error {
 	aggregatedAPIServerTLSCert, err := aggregatedAPIServerCA.Issue(
 		pkix.Name{CommonName: serviceEndpoint},
 		[]string{serviceEndpoint},
-		24*365*time.Hour,
+		c.certDuration,
 	)
 	if err != nil {
 		return fmt.Errorf("could not issue serving certificate: %w", err)

internal/controller/apicerts/certs_manager_test.go

@@ -50,6 +50,7 @@ func TestManagerControllerOptions(t *testing.T) {
 				secretsInformer,
 				observableWithInformerOption.WithInformer,         // make it possible to observe the behavior of the Filters
 				observableWithInitialEventOption.WithInitialEvent, // make it possible to observe the behavior of the initial event
+				0, // certDuration, not needed for this test
 			)
 			secretsInformerFilter = observableWithInformerOption.GetFilterForInformer(secretsInformer)
 		})
@@ -116,6 +117,7 @@ func TestManagerControllerOptions(t *testing.T) {
 func TestManagerControllerSync(t *testing.T) {
 	spec.Run(t, "Sync", func(t *testing.T, when spec.G, it spec.S) {
 		const installedInNamespace = "some-namespace"
+		const certDuration = 12345678 * time.Second
 
 		var r *require.Assertions
 
@@ -139,6 +141,7 @@ func TestManagerControllerSync(t *testing.T) {
 				kubeInformers.Core().V1().Secrets(),
 				controller.WithInformer,
 				controller.WithInitialEvent,
+				certDuration,
 			)
 
 			// Set this at the last second to support calling subject.Name().
@@ -221,7 +224,7 @@ func TestManagerControllerSync(t *testing.T) {
 					// Validate the created cert using the CA, and also validate the cert's hostname
 					validCert := testutil.ValidateCertificate(t, actualCACert, actualCertChain)
 					validCert.RequireDNSName("pinniped-api." + installedInNamespace + ".svc")
-					validCert.RequireLifetime(time.Now(), time.Now().Add(24*365*time.Hour), 2*time.Minute)
+					validCert.RequireLifetime(time.Now(), time.Now().Add(certDuration), 2*time.Minute)
 					validCert.RequireMatchesPrivateKey(actualPrivateKey)
 
 					// Make sure we updated the APIService caBundle and left it otherwise unchanged

internal/controllermanager/prepare_controllers.go

@@ -34,7 +34,8 @@ func PrepareControllers(
 	serverInstallationNamespace string,
 	discoveryURLOverride *string,
 	dynamicCertProvider provider.DynamicTLSServingCertProvider,
-	servingCertRotationThreshold float32,
+	servingCertDuration time.Duration,
+	servingCertRenewBefore time.Duration,
 ) (func(ctx context.Context), error) {
 	// Create k8s clients.
 	k8sClient, aggregatorClient, pinnipedClient, err := createClients()
@@ -68,6 +69,7 @@ func PrepareControllers(
 				installationNamespaceK8sInformers.Core().V1().Secrets(),
 				controller.WithInformer,
 				controller.WithInitialEvent,
+				servingCertDuration,
 			),
 			singletonWorker,
 		).
@@ -86,7 +88,7 @@ func PrepareControllers(
 				k8sClient,
 				installationNamespaceK8sInformers.Core().V1().Secrets(),
 				controller.WithInformer,
-				servingCertRotationThreshold,
+				servingCertRenewBefore,
 			),
 			singletonWorker,
 		)

internal/server/server.go

@@ -10,11 +10,9 @@ import (
 	"context"
 	"fmt"
 	"io"
-	"strconv"
 	"time"
 
 	"github.com/spf13/cobra"
-	"github.com/spf13/pflag"
 	genericapiserver "k8s.io/apiserver/pkg/server"
 	genericoptions "k8s.io/apiserver/pkg/server/options"
 	"k8s.io/apiserver/plugin/pkg/authenticator/token/webhook"
@@ -23,7 +21,6 @@ import (
 
 	"github.com/suzerain-io/pinniped/internal/apiserver"
 	"github.com/suzerain-io/pinniped/internal/certauthority/kubecertauthority"
-	"github.com/suzerain-io/pinniped/internal/constable"
 	"github.com/suzerain-io/pinniped/internal/controllermanager"
 	"github.com/suzerain-io/pinniped/internal/downward"
 	"github.com/suzerain-io/pinniped/internal/provider"
@@ -32,31 +29,6 @@ import (
 	"github.com/suzerain-io/pinniped/pkg/config"
 )
 
-type percentageValue struct {
-	percentage float32
-}
-
-var _ pflag.Value = &percentageValue{}
-
-func (p *percentageValue) String() string {
-	return fmt.Sprintf("%.2f%%", p.percentage*100)
-}
-
-func (p *percentageValue) Set(s string) error {
-	f, err := strconv.ParseFloat(s, 32)
-	if err != nil || f < 0 || f > 1 {
-		return constable.Error("must pass real number between 0 and 1")
-	}
-
-	p.percentage = float32(f)
-
-	return nil
-}
-
-func (p *percentageValue) Type() string {
-	return "percentage"
-}
-
 // App is an object that represents the pinniped-server application.
 type App struct {
 	cmd *cobra.Command
@@ -64,7 +36,6 @@ type App struct {
 	// CLI flags
 	configPath      string
 	downwardAPIPath string
-	servingCertRotationThreshold percentageValue
 }
 
 // This is ignored for now because we turn off etcd storage below, but this is
@@ -118,13 +89,6 @@ func addCommandlineFlagsToCommand(cmd *cobra.Command, app *App) {
 		"/etc/podinfo",
 		"path to Downward API volume mount",
 	)
-
-	app.servingCertRotationThreshold.percentage = .70 // default
-	cmd.Flags().Var(
-		&app.servingCertRotationThreshold,
-		"serving-cert-rotation-threshold",
-		"real number between 0 and 1 indicating percentage of lifetime before rotation of serving cert",
-	)
 }
 
 // Boot the aggregated API server, which will in turn boot the controllers.
@@ -168,7 +132,8 @@ func (a *App) runServer(ctx context.Context) error {
 		serverInstallationNamespace,
 		cfg.DiscoveryInfo.URL,
 		dynamicCertProvider,
-		a.servingCertRotationThreshold.percentage,
+		time.Duration(*cfg.APIConfig.ServingCertificateConfig.DurationSeconds)*time.Second,
+		time.Duration(*cfg.APIConfig.ServingCertificateConfig.RenewBeforeSeconds)*time.Second,
 	)
 	if err != nil {
 		return fmt.Errorf("could not prepare controllers: %w", err)

internal/server/server_test.go

@@ -29,7 +29,6 @@ Flags:
       --downward-api-path string       path to Downward API volume mount (default "/etc/podinfo")
   -h, --help                           help for pinniped-server
       --log-flush-frequency duration   Maximum number of seconds between log flushes (default 5s)
-      --serving-cert-rotation-threshold percentage   real number between 0 and 1 indicating percentage of lifetime before rotation of serving cert (default 70.00%)
 `
 
 func TestCommand(t *testing.T) {
@@ -69,30 +68,6 @@ func TestCommand(t *testing.T) {
 			},
 			wantErr: `unknown command "tuna" for "pinniped-server"`,
 		},
-		{
-			name: "PercentageIsNotRealNumber",
-			args: []string{
-				"--config", "some/path/to/config.yaml",
-				"--serving-cert-rotation-threshold", "tuna",
-			},
-			wantErr: `invalid argument "tuna" for "--serving-cert-rotation-threshold" flag: must pass real number between 0 and 1`,
-		},
-		{
-			name: "PercentageIsTooSmall",
-			args: []string{
-				"--config", "some/path/to/config.yaml",
-				"--serving-cert-rotation-threshold", "-1",
-			},
-			wantErr: `invalid argument "-1" for "--serving-cert-rotation-threshold" flag: must pass real number between 0 and 1`,
-		},
-		{
-			name: "PercentageIsTooLarge",
-			args: []string{
-				"--config", "some/path/to/config.yaml",
-				"--serving-cert-rotation-threshold", "75",
-			},
-			wantErr: `invalid argument "75" for "--serving-cert-rotation-threshold" flag: must pass real number between 0 and 1`,
-		},
 	}
 	for _, test := range tests {
 		test := test

pkg/config/api/types.go

@@ -9,9 +9,10 @@ package api
 type Config struct {
 	WebhookConfig WebhookConfigSpec `json:"webhook"`
 	DiscoveryInfo DiscoveryInfoSpec `json:"discovery"`
+	APIConfig     APIConfigSpec     `json:"api"`
 }
 
-// WebhookConfig contains configuration knobs specific to Pinniped's use
+// WebhookConfig contains configuration knobs specific to pinniped's use
 // of a webhook for token validation.
 type WebhookConfigSpec struct {
 	// URL contains the URL of the webhook that pinniped will use
@@ -31,3 +32,26 @@ type DiscoveryInfoSpec struct {
 	// URL contains the URL at which pinniped can be contacted.
 	URL *string `json:"url,omitempty"`
 }
+
+// APIConfigSpec contains configuration knobs for the pinniped API.
+//nolint: golint
+type APIConfigSpec struct {
+	ServingCertificateConfig ServingCertificateConfigSpec `json:"servingCertificate"`
+}
+
+// ServingCertificateConfigSpec contains the configuration knobs for the API's
+// serving certificate, i.e., the x509 certificate that it uses for the server
+// certificate in inbound TLS connections.
+type ServingCertificateConfigSpec struct {
+	// DurationSeconds is the validity period, in seconds, of the API serving
+	// certificate. By default, the serving certificate is issued for 31536000
+	// seconds (1 year).
+	DurationSeconds *int64 `json:"durationSeconds,omitempty"`
+
+	// RenewBeforeSeconds is the period of time, in seconds, that pinniped will
+	// wait before rotating the serving certificate. This period of time starts
+	// upon issuance of the serving certificate. This must be less than
+	// DurationSeconds. By default, pinniped begins rotation after 23328000
+	// seconds (about 9 months).
+	RenewBeforeSeconds *int64 `json:"renewBeforeSeconds,omitempty"`
+}

pkg/config/config.go

@@ -13,10 +13,18 @@ import (
 
 	"sigs.k8s.io/yaml"
 
+	"github.com/suzerain-io/pinniped/internal/constable"
 	"github.com/suzerain-io/pinniped/pkg/config/api"
 )
 
-// FromPath loads an api.Config from a provided local file path.
+const (
+	aboutAYear   = 60 * 60 * 24 * 365
+	about9Months = 60 * 60 * 24 * 30 * 9
+)
+
+// FromPath loads an api.Config from a provided local file path, inserts any
+// defaults (from the api.Config documentation), and verifies that the config is
+// valid (per the api.Config documentation).
 //
 // Note! The api.Config file should contain base64-encoded WebhookCABundle data.
 // This function will decode that base64-encoded data to PEM bytes to be stored
@@ -32,5 +40,33 @@ func FromPath(path string) (*api.Config, error) {
 		return nil, fmt.Errorf("decode yaml: %w", err)
 	}
 
+	maybeSetAPIDefaults(&config.APIConfig)
+
+	if err := validateAPI(&config.APIConfig); err != nil {
+		return nil, fmt.Errorf("validate api: %w", err)
+	}
+
 	return &config, nil
 }
+
+func maybeSetAPIDefaults(apiConfig *api.APIConfigSpec) {
+	if apiConfig.ServingCertificateConfig.DurationSeconds == nil {
+		apiConfig.ServingCertificateConfig.DurationSeconds = int64Ptr(aboutAYear)
+	}
+
+	if apiConfig.ServingCertificateConfig.RenewBeforeSeconds == nil {
+		apiConfig.ServingCertificateConfig.RenewBeforeSeconds = int64Ptr(about9Months)
+	}
+}
+
+func validateAPI(apiConfig *api.APIConfigSpec) error {
+	if *apiConfig.ServingCertificateConfig.DurationSeconds < *apiConfig.ServingCertificateConfig.RenewBeforeSeconds {
+		return constable.Error("durationSeconds cannot be smaller than renewBeforeSeconds")
+	}
+
+	return nil
+}
+
+func int64Ptr(i int64) *int64 {
+	return &i
+}

pkg/config/config_test.go

@@ -18,6 +18,7 @@ func TestFromPath(t *testing.T) {
 		name       string
 		path       string
 		wantConfig *api.Config
+		wantError  string
 	}{
 		{
 			name: "Happy",
@@ -30,11 +31,17 @@ func TestFromPath(t *testing.T) {
 					URL:      "https://tuna.com/fish?marlin",
 					CABundle: []byte("-----BEGIN CERTIFICATE-----..."),
 				},
+				APIConfig: api.APIConfigSpec{
+					ServingCertificateConfig: api.ServingCertificateConfigSpec{
+						DurationSeconds:    int64Ptr(3600),
+						RenewBeforeSeconds: int64Ptr(2400),
+					},
+				},
 			},
 		},
 		{
-			name: "NoDiscovery",
-			path: "testdata/no-discovery.yaml",
+			name: "Default",
+			path: "testdata/default.yaml",
 			wantConfig: &api.Config{
 				DiscoveryInfo: api.DiscoveryInfoSpec{
 					URL: nil,
@@ -43,21 +50,34 @@ func TestFromPath(t *testing.T) {
 					URL:      "https://tuna.com/fish?marlin",
 					CABundle: []byte("-----BEGIN CERTIFICATE-----..."),
 				},
+				APIConfig: api.APIConfigSpec{
+					ServingCertificateConfig: api.ServingCertificateConfigSpec{
+						DurationSeconds:    int64Ptr(60 * 60 * 24 * 365),    // about a year
+						RenewBeforeSeconds: int64Ptr(60 * 60 * 24 * 30 * 9), // about 9 months
 					},
 				},
+			},
+		},
+		{
+			name:      "InvalidDurationRenewBefore",
+			path:      "testdata/invalid-duration-renew-before.yaml",
+			wantError: "validate api: durationSeconds cannot be smaller than renewBeforeSeconds",
+		},
 	}
 	for _, test := range tests {
 		test := test
 		t.Run(test.name, func(t *testing.T) {
 			config, err := FromPath(test.path)
+			if test.wantError != "" {
+				require.EqualError(t, err, test.wantError)
+			} else {
 				require.NoError(t, err)
 				require.Equal(t, test.wantConfig, config)
+			}
 		})
 	}
 }
 
 func stringPtr(s string) *string {
-	sPtr := new(string)
-	*sPtr = s
-	return sPtr
+	return &s
 }

pkg/config/testdata/happy.yaml

@@ -4,3 +4,7 @@ discovery:
 webhook:
   url: https://tuna.com/fish?marlin
   caBundle: LS0tLS1CRUdJTiBDRVJUSUZJQ0FURS0tLS0tLi4u
+api:
+  servingCertificate:
+    durationSeconds: 3600
+    renewBeforeSeconds: 2400

pkg/config/testdata/invalid-duration-renew-before.yaml

@@ -0,0 +1,8 @@
+---
+webhook:
+  url: https://tuna.com/fish?marlin
+  caBundle: LS0tLS1CRUdJTiBDRVJUSUZJQ0FURS0tLS0tLi4u
+api:
+  servingCertificate:
+    durationSeconds: 2400
+    renewBeforeSeconds: 3600

test/integration/api_serving_certs_test.go

@@ -58,7 +58,7 @@ func TestAPIServingCertificateAutoCreationAndRotation(t *testing.T) {
 					return err
 				}
 
-				secret.Data["caCertificate"], err = createExpiredCertificate()
+				secret.Data["tlsCertificateChain"], err = createExpiredCertificate()
 				if err != nil {
 					return err
 				}