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Enable Kubelet Server Certificate Rotation

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Risk Level: Medium (should be achieved)

Ensure that Kubelet server certificates are automatically rotated by setting the "RotateKubeletServerCertificate" parameter to true in order to enhance availability by preventing downtime caused by expired certificates. This setting enables the Kubelet to automatically request new serving certificates from the API server as the current ones approach expiration, provided the necessary "CertificateSigningRequest" objects are approved.

Security

Enabling Kubelet server certificate rotation ensures that the Kubelet automatically requests new serving credentials from the API server as existing ones near expiration, preventing downtime due to expired certificates and supporting the availability pillar of the CIA security triad. This rotation mechanism requires setting the "RotateKubeletServerCertificate" feature gate to true when Kubelets bootstrap their credentials through the API server.

Audit

To determine if Kubelet server certificate rotation is enabled, perform the following operations:

Using OCI Console

  1. Sign in to your Oracle Cloud Infrastructure (OCI) account.

  2. Navigate to Kubernetes Clusters (OKE) console available at https://cloud.oracle.com/containers/clusters.

  3. For Applied filters, choose an OCI compartment from the Compartment dropdown menu, to list the OCI Kubernetes Engine (OKE) clusters provisioned in the selected compartment.

  4. Click on the name (link) of the OCI Kubernetes Engine (OKE) cluster that you want to examine, listed in the Name column.

  5. Select the Node pools tab and click on the name (link) of the node pool that you want to examine.

  6. Select the Nodes tab and click on the name (link) of the node (instance) that you want to examine.

  7. Select the Details tab and choose Copy next to Public IP address, in the Instance access section, to get the public IP address of your OKE cluster node.

  8. Use your preferred method to open an SSH connection to the selected cluster node. For the public IP address, use the IP address copied in the previous step. The default username is opc for Oracle Linux and Red Hat Enterprise Linux compatible images, as well as Windows platform images. For Ubuntu images, the default username is ubuntu. See Connecting to an Instance for more details.

  9. Once connected to your OKE cluster worker node, run the commands listed below to determine if the "RotateKubeletServerCertificate" parameter is set to true in the Kubelet config file:

    1. Run the following command to determine if the Kubelet service is running: 
      sudo systemctl status kubelet
    2. The output should return Active: active (running).
    3. Run the following command to find the kubelet-config.json file for your node: 
      find / -name kubelet-config.json
    4. The command output should return the location of the kubelet-config.json file, such as /etc/kubernetes/kubelet/kubelet-config.json.
    5. Run the following command to describe the contents of the kubelet-config.json file: 
      sudo more /etc/kubernetes/kubelet/kubelet-config.json
    6. The command output should return the Kubelet config file contents: 
      {
	"kind": "KubeletConfiguration",
	"apiVersion": "kubelet.config.k8s.io/v1beta1",
	"address": "0.0.0.0",
	"tlsCertFile": "/etc/kubernetes/kubelet/pki/kubelet.crt",
	"tlsPrivateKeyFile": "/etc/kubernetes/kubelet/pki/kubelet.key",
	"rotateCertificates": true,
	"authentication": {
		"anonymous": {
			"enabled": true
		},
		"webhook": {
			"cacheTTL": "2m0s",
			"enabled": true
		},
		"x509": {
			"clientCAFile": "/etc/kubernetes/pki/ca.crt"
		}
	},
	"authorization": {
	"mode": "Webhook",
		"webhook": {
			"cacheAuthorizedTTL": "5m0s",
			"cacheUnauthorizedTTL": "30s"
		}
	},
	"clusterDomain": "cluster.local",
	"hairpinMode": "hairpin-veth",
	"readOnlyPort": 0,
	"cgroupDriver": "cgroupfs",
	"cgroupRoot": "/",
	"featureGates": {
		"RotateKubeletServerCertificate": false
	},
	"makeIPTablesUtilChains": false,
	"iptablesMasqueradeBit": 14,
	"iptablesDropBit": 15,
	"protectKernelDefaults": true,
	"serializeImagePulls": false,
	"serverTLSBootstrap": true,
	"tlsCipherSuites": ["TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256", "TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256", "TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305", "TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384", "TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305", "TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384", "TLS_RSA_WITH_AES_256_GCM_SHA384", "TLS_RSA_WITH_AES_128_GCM_SHA256"]
}

      To determine if Kubelet server certificate rotation is enabled, check the value of the "RotateKubeletServerCertificate" property. If "RotateKubeletServerCertificate" is not set to true, as shown in the example above, Kubelet server certificate rotation is not enabled.

  10. Repeat steps no. 6 - 9 for each worker node running within the selected node pool.

  11. Repeat steps no. 5 - 10 for each node pool created for the selected OKE cluster.

Using OCI CLI

  1. Run iam compartment list command (Windows/macOS/Linux) with output query filters to list the ID of each compartment available in your Oracle Cloud Infrastructure (OCI) account:

    oci iam compartment list
	--all
	--include-root
	--query 'data[]."id"'

  2. The command output should return the requested OCI compartment identifiers (OCIDs):

    [
	"ocid1.tenancy.oc1..aaaabbbbccccddddabcd1234abcd1234abcd1234abcd1234abcd1234abcd",
	"ocid1.compartment.oc1..abcd1234abcd1234abcd1234abcd1234abcd1234abcd1234abcd1234abcd"
]

  3. Run ce cluster list command (Windows/macOS/Linux) with the ID of the OCI compartment that you want to examine as the identifier parameter, to list the ID of each OCI Kubernetes Engine (OKE) cluster available in the selected OCI compartment:

    oci ce cluster list
	--compartment-id 'ocid1.tenancy.oc1..aaaabbbbccccddddabcd1234abcd1234abcd1234abcd1234abcd1234abcd'
	--all
	--query 'data[]."id"'

  4. The command output should return the requested OKE cluster IDs:

    [
	"ocid1.cluster.oc1.ap-sydney-1.aaaabbbbccccddddabcd1234abcd1234abcd1234abcd1234abcd1234abcd",
	"ocid1.cluster.oc1.ap-sydney-1.abcd1234abcd1234abcd1234abcd1234abcd1234abcd1234abcd1234abcd"
]

  5. Run ce node-pool list command (Windows/macOS/Linux) with the ID of the OKE cluster that you want to examine as the identifier parameter, to list the ID of each node pool created for your OKE cluster:

    oci ce node-pool list
	--compartment-id 'ocid1.tenancy.oc1..aaaabbbbccccddddabcd1234abcd1234abcd1234abcd1234abcd1234abcd'
	--cluster-id 'ocid1.cluster.oc1.ap-sydney-1.aaaabbbbccccddddabcd1234abcd1234abcd1234abcd1234abcd1234abcd'
	--query 'data[]."id"'

  6. The command output should return the OKE node pool IDs:

    [
	"ocid1.nodepool.oc1.ap-sydney-1.abcd1234abcd1234abcd1234abcd1234abcd1234abcd1234abcd1234abcd",
	"ocid1.nodepool.oc1.ap-sydney-1.aaaabbbbccccddddabcd1234abcd1234abcd1234abcd1234abcd1234abcd"
]

  7. Run ce node-pool get command (Windows/macOS/Linux) to describe the public IP address of each worker node running within the selected OKE node pool:

    oci ce node-pool get
	--node-pool-id 'ocid1.nodepool.oc1.ap-sydney-1.abcd1234abcd1234abcd1234abcd1234abcd1234abcd1234abcd1234abcd'
	--query 'data.nodes[]."public-ip"'

  8. The command output should return the public IP address of each OKE cluster worker node (instance):

    [
	"<public-ip-node-1>",
	"<public-ip-node-2>",
	"<public-ip-node-3>"
]

  9. Use your preferred method to open an SSH connection to your OKE cluster worker node. For the public IP address, use the IP address returned in the previous step. The default username is opc for Oracle Linux and Red Hat Enterprise Linux compatible images, as well as Windows platform images. For Ubuntu images, the default username is ubuntu. See Connecting to an Instance for more details.

  10. Once connected to your OKE cluster worker node, run the commands listed below to determine if the "RotateKubeletServerCertificate" parameter is set to true in the Kubelet config file:

    1. Run the following command to determine if the Kubelet service is running: 
      sudo systemctl status kubelet
    2. The output should return Active: active (running).
    3. Run the following command to find the kubelet-config.json file for your node: 
      find / -name kubelet-config.json
    4. The command output should return the location of the kubelet-config.json file, such as /etc/kubernetes/kubelet/kubelet-config.json.
    5. Run the following command to describe the contents of the kubelet-config.json file: 
      sudo more /etc/kubernetes/kubelet/kubelet-config.json
    6. The command output should return the Kubelet config file contents: 
      {
	"kind": "KubeletConfiguration",
	"apiVersion": "kubelet.config.k8s.io/v1beta1",
	"address": "0.0.0.0","tlsCertFile": "/etc/kubernetes/kubelet/pki/kubelet.crt",
	"tlsPrivateKeyFile": "/etc/kubernetes/kubelet/pki/kubelet.key",
	"rotateCertificates": true,
	"authentication": {
	"anonymous": {
		"enabled": true
	},
	"webhook": {
		"cacheTTL": "2m0s",
		"enabled": true
	},
	"x509": {
		"clientCAFile": "/etc/kubernetes/pki/ca.crt"
	}
	},
	"authorization": {
		"mode": "Webhook",
		"webhook": {
			"cacheAuthorizedTTL": "5m0s",
			"cacheUnauthorizedTTL": "30s"
		}
	},
	"clusterDomain": "cluster.local",
	"hairpinMode": "hairpin-veth",
	"readOnlyPort": 0,
	"cgroupDriver": "cgroupfs",
	"cgroupRoot": "/",
	"featureGates": {
		"RotateKubeletServerCertificate": false
	},
	"makeIPTablesUtilChains": false,
	"iptablesMasqueradeBit": 14,
	"iptablesDropBit": 15,
	"protectKernelDefaults": true,
	"serializeImagePulls": false,
	"serverTLSBootstrap": true,
	"tlsCipherSuites": ["TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256", "TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256", "TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305", "TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384", "TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305", "TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384", "TLS_RSA_WITH_AES_256_GCM_SHA384", "TLS_RSA_WITH_AES_128_GCM_SHA256"]
}

      To determine if Kubelet server certificate rotation is enabled, check the value of the "RotateKubeletServerCertificate" property. If "RotateKubeletServerCertificate" is not set to true, as shown in the example above, Kubelet server certificate rotation is not enabled.

  11. Repeat steps no. 9 and 10 for each worker node running within the selected node pool.

  12. Repeat steps no. 7 - 11 for each node pool created for the selected OKE cluster.

Remediation / Resolution

To ensure that Kubelet server certificate rotation is enabled, perform the following operations:

Using OCI Console

  1. Sign in to your Oracle Cloud Infrastructure (OCI) account.

  2. Navigate to Kubernetes Clusters (OKE) console available at https://cloud.oracle.com/containers/clusters.

  3. For Applied filters, choose an OCI compartment from the Compartment dropdown menu, to list the OCI Kubernetes Engine (OKE) clusters provisioned in the selected compartment.

  4. Click on the name (link) of the OCI Kubernetes Engine (OKE) cluster that you want to configure, listed in the Name column.

  5. Select the Node pools tab and click on the name (link) of the node pool that you want to access.

  6. Select the Nodes tab and click on the name (link) of the node (instance) that you want to configure.

  7. Select the Details tab and choose Copy next to Public IP address, in the Instance access section, to get the public IP address of your OKE cluster node.

  8. Use your preferred method to open an SSH connection to the selected cluster node. For the public IP address, use the IP address copied in the previous step. The default username is opc for Oracle Linux and Red Hat Enterprise Linux compatible images, as well as Windows platform images. For Ubuntu images, the default username is ubuntu. See Connecting to an Instance for more details.

  9. Once connected to your OKE cluster worker node, edit the kubelet-config.json file for your Kubelet server, to set the "RotateKubeletServerCertificate" configuration parameter to true, as shown in the example below, to enable Kubelet server certificate rotation:

    {
	"kind": "KubeletConfiguration",
	"apiVersion": "kubelet.config.k8s.io/v1beta1",
	"address": "0.0.0.0",
	"tlsCertFile": "/etc/kubernetes/kubelet/pki/kubelet.crt",
	"tlsPrivateKeyFile": "/etc/kubernetes/kubelet/pki/kubelet.key",
	"rotateCertificates": true,
	"authentication": {
		"anonymous": {
			"enabled": false
		},
		"webhook": {
			"cacheTTL": "2m0s",
			"enabled": true
		},
		"x509": {
			"clientCAFile": "/etc/kubernetes/pki/ca.crt"
		}
	},
	"authorization": {
		"mode": "Webhook",
		"webhook": {
			"cacheAuthorizedTTL": "5m0s",
			"cacheUnauthorizedTTL": "30s"
		}
	},
	"clusterDomain": "cluster.local",
	"hairpinMode": "hairpin-veth",
	"readOnlyPort": 0,
	"cgroupDriver": "cgroupfs",
	"cgroupRoot": "/",
	"featureGates": {
		"RotateKubeletServerCertificate": true
	},
	"makeIPTablesUtilChains": true,
	"iptablesMasqueradeBit": 14,
	"iptablesDropBit": 15,
	"protectKernelDefaults": true,
	"serializeImagePulls": false,
	"serverTLSBootstrap": true,
	"tlsCipherSuites": ["TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256", "TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256", "TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305", "TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384", "TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305", "TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384", "TLS_RSA_WITH_AES_256_GCM_SHA384", "TLS_RSA_WITH_AES_128_GCM_SHA256"]
}

  10. Run the following commands to reload systemd and restart the Kubelet service, forcing it to read the updated configuration file:

    sudo systemctl daemon-reload
sudo systemctl restart kubelet

  11. After the restart, run the following command to check the Kubelet service status in order to ensure it came back up successfully and loaded the new configuration:

    sudo systemctl status kubelet

  12. Repeat steps no. 6 - 11 for each worker node running within the selected node pool.

  13. Repeat steps no. 5 - 12 for each node pool deployed for the selected OKE cluster.

Using OCI CLI

  1. Run iam compartment list command (Windows/macOS/Linux) with output query filters to list the ID of each compartment available in your Oracle Cloud Infrastructure (OCI) account:

    oci iam compartment list
	--all
	--include-root
	--query 'data[]."id"'

  2. The command output should return the requested OCI compartment identifiers (OCIDs):

    [
	"ocid1.tenancy.oc1..aaaabbbbccccddddabcd1234abcd1234abcd1234abcd1234abcd1234abcd",
	"ocid1.compartment.oc1..abcd1234abcd1234abcd1234abcd1234abcd1234abcd1234abcd1234abcd"
]

  3. Run ce cluster list command (Windows/macOS/Linux) with the ID of the OCI compartment that you want to examine as the identifier parameter, to list the ID of each OCI Kubernetes Engine (OKE) cluster available in the selected OCI compartment:

    oci ce cluster list
	--compartment-id 'ocid1.tenancy.oc1..aaaabbbbccccddddabcd1234abcd1234abcd1234abcd1234abcd1234abcd'
	--all
	--query 'data[]."id"'

  4. The command output should return the requested OKE cluster IDs:

    [
	"ocid1.cluster.oc1.ap-sydney-1.aaaabbbbccccddddabcd1234abcd1234abcd1234abcd1234abcd1234abcd",
	"ocid1.cluster.oc1.ap-sydney-1.abcd1234abcd1234abcd1234abcd1234abcd1234abcd1234abcd1234abcd"
]

  5. Run ce node-pool list command (Windows/macOS/Linux) with the ID of the OKE cluster that you want to examine as the identifier parameter, to list the ID of each node pool created for your OKE cluster:

    oci ce node-pool list
	--compartment-id 'ocid1.tenancy.oc1..aaaabbbbccccddddabcd1234abcd1234abcd1234abcd1234abcd1234abcd'
	--cluster-id 'ocid1.cluster.oc1.ap-sydney-1.aaaabbbbccccddddabcd1234abcd1234abcd1234abcd1234abcd1234abcd'
	--query 'data[]."id"'

  6. The command output should return the OKE node pool IDs:

    [
	"ocid1.nodepool.oc1.ap-sydney-1.abcd1234abcd1234abcd1234abcd1234abcd1234abcd1234abcd1234abcd",
	"ocid1.nodepool.oc1.ap-sydney-1.aaaabbbbccccddddabcd1234abcd1234abcd1234abcd1234abcd1234abcd"
]

  7. Run ce node-pool get command (Windows/macOS/Linux) to describe the public IP address of each worker node running within the selected OKE node pool:

    oci ce node-pool get
	--node-pool-id 'ocid1.nodepool.oc1.ap-sydney-1.abcd1234abcd1234abcd1234abcd1234abcd1234abcd1234abcd1234abcd'
	--query 'data.nodes[]."public-ip"'

  8. The command output should return the public IP address of each OKE cluster worker node (instance):

    [
	"<public-ip-node-1>",
	"<public-ip-node-2>",
	"<public-ip-node-3>"
]

  9. Use your preferred method to open an SSH connection to your OKE cluster worker node. For the public IP address, use the IP address returned in the previous step. The default username is opc for Oracle Linux and Red Hat Enterprise Linux compatible images, as well as Windows platform images. For Ubuntu images, the default username is ubuntu. See Connecting to an Instance for more details.

  10. Once connected to your OKE cluster worker node, edit the kubelet-config.json file for your Kubelet server, to set the "RotateKubeletServerCertificate" configuration parameter to true, as shown in the example below, to enable Kubelet server certificate rotation:

    {
	"kind": "KubeletConfiguration",
	"apiVersion": "kubelet.config.k8s.io/v1beta1",
	"address": "0.0.0.0",
	"tlsCertFile": "/etc/kubernetes/kubelet/pki/kubelet.crt",
	"tlsPrivateKeyFile": "/etc/kubernetes/kubelet/pki/kubelet.key",
	"rotateCertificates": true,
	"authentication": {
		"anonymous": {
			"enabled": false
		},
		"webhook": {
			"cacheTTL": "2m0s",
			"enabled": true
		},
		"x509": {
			"clientCAFile": "/etc/kubernetes/pki/ca.crt"
		}
	},
	"authorization": {
	"mode": "Webhook",
	"webhook": {
		"cacheAuthorizedTTL": "5m0s",
		"cacheUnauthorizedTTL": "30s"
	}
	},
	"clusterDomain": "cluster.local",
	"hairpinMode": "hairpin-veth",
	"readOnlyPort": 0,
	"cgroupDriver": "cgroupfs",
	"cgroupRoot": "/",
	"featureGates": {
		"RotateKubeletServerCertificate": true
	},
	"makeIPTablesUtilChains": true,
	"iptablesMasqueradeBit": 14,
	"iptablesDropBit": 15,
	"protectKernelDefaults": true,
	"serializeImagePulls": false,
	"serverTLSBootstrap": true,
	"tlsCipherSuites": ["TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256", "TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256", "TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305", "TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384", "TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305", "TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384", "TLS_RSA_WITH_AES_256_GCM_SHA384", "TLS_RSA_WITH_AES_128_GCM_SHA256"]
}

  11. Run the following commands to reload systemd and restart the Kubelet service, forcing it to read the updated configuration file:

    sudo systemctl daemon-reload
sudo systemctl restart kubelet

  12. After the restart, run the following command to check the Kubelet service status in order to ensure it came back up successfully and loaded the new configuration:

    sudo systemctl status kubelet

  13. Repeat steps no. 9 - 12 for each worker node running within the selected node pool.

  14. Repeat steps no. 7 - 13 for each node pool deployed for the selected OKE cluster.

References

Publication date Dec 1, 2025

Related OCI-OKE rules