Add upstream TLS trust from CM bundles

pkg/activator/certificate/cache.go

@@ -26,11 +26,16 @@ import (
 
 	"go.uber.org/zap"
 	corev1 "k8s.io/api/core/v1"
+	"k8s.io/apimachinery/pkg/labels"
+	"k8s.io/apimachinery/pkg/selection"
 	v1 "k8s.io/client-go/informers/core/v1"
 	"k8s.io/client-go/tools/cache"
+	"knative.dev/networking/pkg/apis/networking"
+	"knative.dev/pkg/reconciler"
 
 	"knative.dev/networking/pkg/certificates"
 	netcfg "knative.dev/networking/pkg/config"
+	configmapinformer "knative.dev/pkg/client/injection/kube/informers/core/v1/configmap"
 	"knative.dev/pkg/controller"
 	secretinformer "knative.dev/pkg/injection/clients/namespacedkube/informers/core/v1/secret"
 	"knative.dev/pkg/logging"
@@ -39,8 +44,9 @@ import (
 
 // CertCache caches certificates and CA pool.
 type CertCache struct {
-	secretInformer v1.SecretInformer
-	logger         *zap.SugaredLogger
+	secretInformer    v1.SecretInformer
+	configmapInformer v1.ConfigMapInformer
+	logger            *zap.SugaredLogger
 
 	certificate *tls.Certificate
 	TLSConf     tls.Config
@@ -51,10 +57,12 @@ type CertCache struct {
 // NewCertCache creates and starts the certificate cache that watches Activators certificate.
 func NewCertCache(ctx context.Context) (*CertCache, error) {
 	secretInformer := secretinformer.Get(ctx)
+	configmapInformer := configmapinformer.Get(ctx)
 
 	cr := &CertCache{
-		secretInformer: secretInformer,
-		logger:         logging.FromContext(ctx),
+		secretInformer:    secretInformer,
+		configmapInformer: configmapInformer,
+		logger:            logging.FromContext(ctx),
 	}
 
 	secret, err := cr.secretInformer.Lister().Secrets(system.Namespace()).Get(netcfg.ServingRoutingCertName)
@@ -63,7 +71,8 @@ func NewCertCache(ctx context.Context) (*CertCache, error) {
 			system.Namespace(), netcfg.ServingRoutingCertName, err)
 	}
 
-	cr.updateCache(secret)
+	cr.updateCertificate(secret)
+	cr.updateTrustPool()
 
 	secretInformer.Informer().AddEventHandler(cache.FilteringResourceEventHandler{
 		FilterFunc: controller.FilterWithNameAndNamespace(system.Namespace(), netcfg.ServingRoutingCertName),
@@ -73,45 +82,112 @@ func NewCertCache(ctx context.Context) (*CertCache, error) {
 		},
 	})
 
+	configmapInformer.Informer().AddEventHandler(cache.FilteringResourceEventHandler{
+		FilterFunc: reconciler.ChainFilterFuncs(
+			reconciler.LabelExistsFilterFunc(networking.TrustBundleLabelKey),
+		),
+		Handler: controller.HandleAll(func(obj interface{}) {
+			cr.updateTrustPool()
+		}),
+	})
+
 	return cr, nil
 }
 
 func (cr *CertCache) handleCertificateAdd(added interface{}) {
 	if secret, ok := added.(*corev1.Secret); ok {
-		cr.updateCache(secret)
+		cr.updateCertificate(secret)
+		cr.updateTrustPool()
 	}
 }
 
-func (cr *CertCache) updateCache(secret *corev1.Secret) {
+func (cr *CertCache) handleCertificateUpdate(_, new interface{}) {
+	cr.handleCertificateAdd(new)
+	cr.updateTrustPool()
+}
+
+func (cr *CertCache) updateCertificate(secret *corev1.Secret) {
 	cr.certificatesMux.Lock()
 	defer cr.certificatesMux.Unlock()
 
 	cert, err := tls.X509KeyPair(secret.Data[certificates.CertName], secret.Data[certificates.PrivateKeyName])
 	if err != nil {
-		cr.logger.Warnw("failed to parse secret", zap.Error(err))
+		cr.logger.Warnf("failed to parse certificate in secret %s/%s: %v", secret.Namespace, secret.Name, zap.Error(err))
 		return
 	}
 	cr.certificate = &cert
+}
 
+// CA can optionally be in `ca.crt` in the `routing-serving-certs` secret
+// and/or configured using a trust-bundle via ConfigMap that has the defined label `knative-ca-trust-bundle`.
+func (cr *CertCache) updateTrustPool() {
 	pool := x509.NewCertPool()
-	block, _ := pem.Decode(secret.Data[certificates.CaCertName])
-	ca, err := x509.ParseCertificate(block.Bytes)
-	if err != nil {
-		cr.logger.Warnw("failed to parse CA", zap.Error(err))
-		return
-	}
-	pool.AddCert(ca)
+
+	cr.addSecretCAIfPresent(pool)
+	cr.addTrustBundles(pool)
+
+	// Use the trust pool in upstream TLS context
+	cr.certificatesMux.Lock()
+	defer cr.certificatesMux.Unlock()
 
 	cr.TLSConf.RootCAs = pool
 	cr.TLSConf.ServerName = certificates.LegacyFakeDnsName
 	cr.TLSConf.MinVersion = tls.VersionTLS13
 }
 
-func (cr *CertCache) handleCertificateUpdate(_, new interface{}) {
-	cr.handleCertificateAdd(new)
+func (cr *CertCache) addSecretCAIfPresent(pool *x509.CertPool) {
+	secret, err := cr.secretInformer.Lister().Secrets(system.Namespace()).Get(netcfg.ServingRoutingCertName)
+	if err != nil {
+		cr.logger.Warnf("Failed to get secret %s/%s: %v", system.Namespace(), netcfg.ServingRoutingCertName, zap.Error(err))
+		return
+	}
+	if len(secret.Data[certificates.CaCertName]) > 0 {
+		block, _ := pem.Decode(secret.Data[certificates.CaCertName])
+		ca, err := x509.ParseCertificate(block.Bytes)
+		if err != nil {
+			cr.logger.Warnf("CA from Secret %s/%s[%s] is invalid and will be ignored: %v",
+				system.Namespace(), netcfg.ServingRoutingCertName, certificates.CaCertName, err)
+		} else {
+			pool.AddCert(ca)
+		}
+	}
+}
+
+func (cr *CertCache) addTrustBundles(pool *x509.CertPool) {
+	selector, err := getLabelSelector(networking.TrustBundleLabelKey)
+	if err != nil {
+		cr.logger.Error("Failed to get label selector", zap.Error(err))
+		return
+	}
+	cms, err := cr.configmapInformer.Lister().ConfigMaps(system.Namespace()).List(selector)
+	if err != nil {
+		cr.logger.Warnf("Failed to get ConfigMaps %s/%s with label %s: %v", system.Namespace(),
+			netcfg.ServingRoutingCertName, networking.TrustBundleLabelKey, zap.Error(err))
+		return
+	}
+
+	for _, cm := range cms {
+		for _, bundle := range cm.Data {
+			ok := pool.AppendCertsFromPEM([]byte(bundle))
+			if !ok {
+				cr.logger.Warnf("Failed to add CA bundle from ConfigMaps %s/%s as it contains invalid certificates. Bundle: %s", system.Namespace(),
+					cm.Name, bundle)
+			}
+		}
+	}
 }
 
 // GetCertificate returns the cached certificates.
 func (cr *CertCache) GetCertificate(_ *tls.ClientHelloInfo) (*tls.Certificate, error) {
 	return cr.certificate, nil
 }
+
+func getLabelSelector(label string) (labels.Selector, error) {
+	selector := labels.NewSelector()
+	req, err := labels.NewRequirement(label, selection.Exists, make([]string, 0))
+	if err != nil {
+		return nil, err
+	}
+	selector = selector.Add(*req)
+	return selector, nil
+}