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kubelet request certificates if at least one IP exist

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A Kubernetes Node requires to have at minimum one IP address
because those are used on the Pods field HostIPs and in some cases,
when pods uses hostNetwork: true, as PodIPs.
Nodes that use IP addresses as Hostname are interpreted as an IP
address, so it is possible that are nodes that don't hane any DNSname.

The feature gate AllowDNSOnlyNodeCSR will allow user to opt-in for
the old behavior.

Change-Id: I094531d87246f1e7a5ef4fe57bd5d9840cb1375d
This commit is contained in:
Antonio Ojea
2024-06-30 14:50:46 +00:00
parent 29e4f5a893
commit bc63c412b9
3 changed files with 183 additions and 15 deletions
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44
pkg/kubelet/certificate/kubelet.go
View File

@@ -32,16 +32,44 @@ import (
v1 "k8s.io/api/core/v1"
"k8s.io/apimachinery/pkg/types"
"k8s.io/apiserver/pkg/server/dynamiccertificates"
utilfeature "k8s.io/apiserver/pkg/util/feature"
clientset "k8s.io/client-go/kubernetes"
"k8s.io/client-go/util/certificate"
compbasemetrics "k8s.io/component-base/metrics"
"k8s.io/component-base/metrics/legacyregistry"
"k8s.io/klog/v2"
"k8s.io/kubernetes/pkg/features"
kubeletconfig "k8s.io/kubernetes/pkg/kubelet/apis/config"
"k8s.io/kubernetes/pkg/kubelet/metrics"
netutils "k8s.io/utils/net"
)
func newGetTemplateFn(nodeName types.NodeName, getAddresses func() []v1.NodeAddress) func() *x509.CertificateRequest {
return func() *x509.CertificateRequest {
hostnames, ips := addressesToHostnamesAndIPs(getAddresses())
// by default, require at least one IP before requesting a serving certificate
hasRequiredAddresses := len(ips) > 0
// optionally allow requesting a serving certificate with just a DNS name
if utilfeature.DefaultFeatureGate.Enabled(features.AllowDNSOnlyNodeCSR) {
hasRequiredAddresses = hasRequiredAddresses || len(hostnames) > 0
}
// don't return a template if we have no addresses to request for
if !hasRequiredAddresses {
return nil
}
return &x509.CertificateRequest{
Subject: pkix.Name{
CommonName: fmt.Sprintf("system:node:%s", nodeName),
Organization: []string{"system:nodes"},
},
DNSNames: hostnames,
IPAddresses: ips,
}
}
}
// NewKubeletServerCertificateManager creates a certificate manager for the kubelet when retrieving a server certificate
// or returns an error.
func NewKubeletServerCertificateManager(kubeClient clientset.Interface, kubeCfg *kubeletconfig.KubeletConfiguration, nodeName types.NodeName, getAddresses func() []v1.NodeAddress, certDirectory string) (certificate.Manager, error) {
@@ -92,21 +120,7 @@ func NewKubeletServerCertificateManager(kubeClient clientset.Interface, kubeCfg
)
legacyregistry.MustRegister(certificateRotationAge)
getTemplate := func() *x509.CertificateRequest {
hostnames, ips := addressesToHostnamesAndIPs(getAddresses())
// don't return a template if we have no addresses to request for
if len(hostnames) == 0 && len(ips) == 0 {
return nil
}
return &x509.CertificateRequest{
Subject: pkix.Name{
CommonName: fmt.Sprintf("system:node:%s", nodeName),
Organization: []string{"system:nodes"},
},
DNSNames: hostnames,
IPAddresses: ips,
}
}
getTemplate := newGetTemplateFn(nodeName, getAddresses)
m, err := certificate.NewManager(&certificate.Config{
ClientsetFn: clientsetFn,