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✨ ClusterCache: Deprecate GetClientCertificatePrivateKey and stop using it in KCP #12846

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Merged
merged 1 commit into from
Oct 13, 2025
Merged

✨ ClusterCache: Deprecate GetClientCertificatePrivateKey and stop using it in KCP #12846

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3 changes: 3 additions & 0 deletions controllers/clustercache/cluster_cache.go
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Original file line number Diff line number Diff line change
Expand Up @@ -147,6 +147,9 @@ type ClusterCache interface {
// cert to communicate with etcd.
// This private key is stored and cached in the ClusterCache because it's expensive to generate a new
// private key in every single Reconcile.
//
// Deprecated: This method is deprecated and will be removed in a future release as caching a rsa.PrivateKey
// is outside the scope of the ClusterCache.
GetClientCertificatePrivateKey(ctx context.Context, cluster client.ObjectKey) (*rsa.PrivateKey, error)

// Watch watches a workload cluster for events.
Expand Down
33 changes: 25 additions & 8 deletions controlplane/kubeadm/internal/cluster.go
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Expand Up @@ -32,6 +32,7 @@ import (

clusterv1 "sigs.k8s.io/cluster-api/api/core/v1beta2"
"sigs.k8s.io/cluster-api/controllers/clustercache"
"sigs.k8s.io/cluster-api/util/cache"
"sigs.k8s.io/cluster-api/util/collections"
"sigs.k8s.io/cluster-api/util/secret"
)
Expand All @@ -53,6 +54,18 @@ type Management struct {
EtcdDialTimeout time.Duration
EtcdCallTimeout time.Duration
EtcdLogger *zap.Logger
ClientCertCache cache.Cache[ClientCertEntry]
}

// ClientCertEntry is an Entry for the Cache that stores the client cert.
type ClientCertEntry struct {
Cluster client.ObjectKey
ClientCert *tls.Certificate
}

// Key returns the cache key of a ClientCertEntry.
func (r ClientCertEntry) Key() string {
return r.Cluster.String()
}

// RemoteClusterConnectionError represents a failure to connect to a remote cluster.
Expand Down Expand Up @@ -126,14 +139,18 @@ func (m *Management) GetWorkloadCluster(ctx context.Context, clusterKey client.O
// TODO: consider if we can detect if we are using external etcd in a more explicit way (e.g. looking at the config instead of deriving from the existing certificates)
var clientCert tls.Certificate
if keyData != nil {
clientKey, err := m.ClusterCache.GetClientCertificatePrivateKey(ctx, clusterKey)
if err != nil {
return nil, err
}

clientCert, err = generateClientCert(crtData, keyData, clientKey)
if err != nil {
return nil, err
// Get client cert from cache if possible, otherwise generate it and add it to the cache.
// TODO: When we implement ClusterConfiguration.EncryptionAlgorithm we should add it to
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@sbueringer sbueringer Oct 10, 2025

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Will be done as part of #10077 (comment)

// the ClientCertEntries and make it part of the key.
if entry, ok := m.ClientCertCache.Has(ClientCertEntry{Cluster: clusterKey}.Key()); ok {
clientCert = *entry.ClientCert
} else {
// The client cert expires after 10 years, but that's okay as the cache has a TTL of 1 day.
clientCert, err = generateClientCert(crtData, keyData)
if err != nil {
return nil, err
}
m.ClientCertCache.Add(ClientCertEntry{Cluster: clusterKey, ClientCert: &clientCert})
}
} else {
clientCert, err = m.getAPIServerEtcdClientCert(ctx, clusterKey)
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2 changes: 2 additions & 0 deletions controlplane/kubeadm/internal/cluster_test.go
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Expand Up @@ -42,6 +42,7 @@ import (
clusterv1 "sigs.k8s.io/cluster-api/api/core/v1beta2"
"sigs.k8s.io/cluster-api/controllers/clustercache"
"sigs.k8s.io/cluster-api/controllers/remote"
"sigs.k8s.io/cluster-api/util/cache"
"sigs.k8s.io/cluster-api/util/certs"
"sigs.k8s.io/cluster-api/util/collections"
"sigs.k8s.io/cluster-api/util/kubeconfig"
Expand Down Expand Up @@ -239,6 +240,7 @@ func TestGetWorkloadCluster(t *testing.T) {
Client: env.GetClient(),
SecretCachingClient: secretCachingClient,
ClusterCache: clusterCache,
ClientCertCache: cache.New[ClientCertEntry](24 * time.Hour),
}

// Ensure the ClusterCache reconciled at least once (and if possible created a clusterAccessor).
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2 changes: 2 additions & 0 deletions controlplane/kubeadm/internal/controllers/controller.go
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Expand Up @@ -50,6 +50,7 @@ import (
"sigs.k8s.io/cluster-api/internal/contract"
"sigs.k8s.io/cluster-api/internal/util/ssa"
"sigs.k8s.io/cluster-api/util"
"sigs.k8s.io/cluster-api/util/cache"
"sigs.k8s.io/cluster-api/util/collections"
"sigs.k8s.io/cluster-api/util/conditions"
v1beta1conditions "sigs.k8s.io/cluster-api/util/conditions/deprecated/v1beta1"
Expand Down Expand Up @@ -149,6 +150,7 @@ func (r *KubeadmControlPlaneReconciler) SetupWithManager(ctx context.Context, mg
EtcdDialTimeout: r.EtcdDialTimeout,
EtcdCallTimeout: r.EtcdCallTimeout,
EtcdLogger: r.EtcdLogger,
ClientCertCache: cache.New[internal.ClientCertEntry](24 * time.Hour),
}
}

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6 changes: 5 additions & 1 deletion controlplane/kubeadm/internal/workload_cluster.go
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Expand Up @@ -347,7 +347,7 @@ func calculateAPIServerPort(config *bootstrapv1.KubeadmConfig) int32 {
return 6443
}

func generateClientCert(caCertEncoded, caKeyEncoded []byte, clientKey *rsa.PrivateKey) (tls.Certificate, error) {
func generateClientCert(caCertEncoded, caKeyEncoded []byte) (tls.Certificate, error) {
caCert, err := certs.DecodeCertPEM(caCertEncoded)
if err != nil {
return tls.Certificate{}, err
Expand All @@ -356,6 +356,10 @@ func generateClientCert(caCertEncoded, caKeyEncoded []byte, clientKey *rsa.Priva
if err != nil {
return tls.Certificate{}, err
}
clientKey, err := certs.NewPrivateKey()
if err != nil {
return tls.Certificate{}, err
}
x509Cert, err := newClientCert(caCert, clientKey, caKey)
if err != nil {
return tls.Certificate{}, err
Expand Down