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- Oracle Cloud Infrastructure
- OCI Kubernetes Engine
- Check for Streaming Connection Idle Timeout
Ensure that the "streamingConnectionIdleTimeout" parameter is not set to 0 (zero) in order to automatically close idle streaming connections after a set duration, thus preventing resource exhaustion and ensuring the overall stability of the Kubelet server. The default 4-hour maximum duration for all connections to the Kubelet server may be too long for your specific environment's security and resource requirements. Setting an appropriate value for the streaming connection timeout ensures these connections are terminated promptly after legitimate use, preventing prolonged resource occupation. For environments with high-security or resource constraints, it's recommended to set the "streamingConnectionIdleTimeout" parameter to a duration between 5 minutes ("5m0s") and 30 minutes ("30m0s").
efficiency
Setting the "streamingConnectionIdleTimeout" parameter to 0 (no timeout) is risky because it allows idle streaming connections (such as exec, port-forward, and attach sessions) to remain open indefinitely. This can lead to resource exhaustion, hung or abandoned sessions, and an increased attack surface, thus reducing cluster stability and security.
Audit
To determine the streaming connection idle timeout for the Kubelet server, perform the following operations:
Using OCI Console
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Sign in to your Oracle Cloud Infrastructure (OCI) account.
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Navigate to Kubernetes Clusters (OKE) console available at https://cloud.oracle.com/containers/clusters.
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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.
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Click on the name (link) of the OCI Kubernetes Engine (OKE) cluster that you want to examine, listed in the Name column.
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Select the Node pools tab and click on the name (link) of the node pool that you want to examine.
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Select the Nodes tab and click on the name (link) of the node (instance) that you want to examine.
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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.
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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.
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Once connected to your OKE cluster worker node, run the commands listed below to determine the "streamingConnectionIdleTimeout" parameter value in the Kubelet config file:
- Run the following command to determine if the Kubelet service is running:
sudo systemctl status kubelet
- The output should return Active: active (running).
- Run the following command to find the kubelet-config.json file for your node:
find / -name kubelet-config.json
- The command output should return the location of the kubelet-config.json file, such as /etc/kubernetes/kubelet/kubelet-config.json.
- Run the following command to describe the contents of the kubelet-config.json file:
sudo more /etc/kubernetes/kubelet/kubelet-config.json
- The command output should return the Kubelet config file contents:
{ "kind": "KubeletConfiguration", "apiVersion": "kubelet.config.k8s.io/v1beta1", "address": "0.0.0.0", "authentication": { "anonymous": { "enabled": false }, "webhook": { "cacheTTL": "2m0s", "enabled": true }, "x509": { "clientCAFile": "/etc/kubernetes/pki/ca.crt" } }, "authorization": { "mode": "Webhook", "webhook": { "cacheAuthorizedTTL": "5m0s", "cacheUnauthorizedTTL": "30s" } }, "streamingConnectionIdleTimeout": 0, "clusterDomain": "cluster.local", "hairpinMode": "hairpin-veth", "readOnlyPort": 10255, "cgroupDriver": "cgroupfs", "cgroupRoot": "/", "featureGates": { "RotateKubeletServerCertificate": true }, "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"] }Check the "streamingConnectionIdleTimeout" configuration property value to determine the streaming connection idle timeout. If "streamingConnectionIdleTimeout" is set to 0 (zero), as shown in the example above, the timeout for streaming connections to the Kubelet server is disabled.
- Run the following command to determine if the Kubelet service is running:
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Repeat steps no. 6 - 9 for each worker node running within the selected node pool.
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Repeat steps no. 5 - 10 for each node pool created for the selected OKE cluster.
Using OCI CLI
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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"'
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The command output should return the requested OCI compartment identifiers (OCIDs):
[ "ocid1.tenancy.oc1..aaaabbbbccccddddabcd1234abcd1234abcd1234abcd1234abcd1234abcd", "ocid1.compartment.oc1..abcd1234abcd1234abcd1234abcd1234abcd1234abcd1234abcd1234abcd" ]
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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"'
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The command output should return the requested OKE cluster IDs:
[ "ocid1.cluster.oc1.ap-sydney-1.aaaabbbbccccddddabcd1234abcd1234abcd1234abcd1234abcd1234abcd", "ocid1.cluster.oc1.ap-sydney-1.abcd1234abcd1234abcd1234abcd1234abcd1234abcd1234abcd1234abcd" ]
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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"'
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The command output should return the OKE node pool IDs:
[ "ocid1.nodepool.oc1.ap-sydney-1.abcd1234abcd1234abcd1234abcd1234abcd1234abcd1234abcd1234abcd", "ocid1.nodepool.oc1.ap-sydney-1.aaaabbbbccccddddabcd1234abcd1234abcd1234abcd1234abcd1234abcd" ]
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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"'
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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>" ]
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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.
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Once connected to your OKE cluster worker node, run the commands listed below to determine the "streamingConnectionIdleTimeout" parameter value in the Kubelet config file:
- Run the following command to determine if the Kubelet service is running:
sudo systemctl status kubelet
- The output should return Active: active (running).
- Run the following command to find the kubelet-config.json file for your node:
find / -name kubelet-config.json
- The command output should return the location of the kubelet-config.json file, such as /etc/kubernetes/kubelet/kubelet-config.json.
- Run the following command to describe the contents of the kubelet-config.json file:
sudo more /etc/kubernetes/kubelet/kubelet-config.json
- The command output should return the Kubelet config file contents:
{ "kind": "KubeletConfiguration", "apiVersion": "kubelet.config.k8s.io/v1beta1", "address": "0.0.0.0", "authentication": { "anonymous": { "enabled": false }, "webhook": { "cacheTTL": "2m0s", "enabled": true }, "x509": { "clientCAFile": "/etc/kubernetes/pki/ca.crt" } }, "authorization": { "mode": "Webhook", "webhook": { "cacheAuthorizedTTL": "5m0s", "cacheUnauthorizedTTL": "30s" } }, "streamingConnectionIdleTimeout": 0, "clusterDomain": "cluster.local", "hairpinMode": "hairpin-veth", "readOnlyPort": 10255, "cgroupDriver": "cgroupfs", "cgroupRoot": "/", "featureGates": { "RotateKubeletServerCertificate": true }, "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"] }Check the "streamingConnectionIdleTimeout" configuration property value to determine the streaming connection idle timeout. If "streamingConnectionIdleTimeout" is set to 0 (zero), as shown in the example above, the timeout for streaming connections to the Kubelet server is disabled.
- Run the following command to determine if the Kubelet service is running:
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Repeat steps no. 9 and 10 for each worker node running within the selected node pool.
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Repeat steps no. 7 - 11 for each node pool created for the selected OKE cluster.
Remediation / Resolution
"streamingConnectionIdleTimeout": 0 indicates no timeout. To ensure that the timeout for streaming connections to the Kubelet server is not disabled, set the "streamingConnectionIdleTimeout" parameter to a positive value by performing the following operations:
Using OCI Console
-
Sign in to your Oracle Cloud Infrastructure (OCI) account.
-
Navigate to Kubernetes Clusters (OKE) console available at https://cloud.oracle.com/containers/clusters.
-
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.
-
Click on the name (link) of the OCI Kubernetes Engine (OKE) cluster that you want to configure, listed in the Name column.
-
Select the Node pools tab and click on the name (link) of the node pool that you want to access.
-
Select the Nodes tab and click on the name (link) of the node (instance) that you want to configure.
-
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.
-
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.
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Once connected to your OKE cluster worker node, edit the kubelet-config.json file for your Kubelet server, to configure the "streamingConnectionIdleTimeout" configuration parameter. You can set the "streamingConnectionIdleTimeout" parameter to a duration between 5 ("5m0s") and 30 minutes ("30m0s"), recommended for high-security or resource-constrained environments, as shown in the example below:
{ "kind": "KubeletConfiguration", "apiVersion": "kubelet.config.k8s.io/v1beta1", "address": "0.0.0.0", "authentication": { "anonymous": { "enabled": false }, "webhook": { "cacheTTL": "2m0s", "enabled": true }, "x509": { "clientCAFile": "/etc/kubernetes/pki/ca.crt" } }, "authorization": { "mode": "Webhook", "webhook": { "cacheAuthorizedTTL": "5m0s", "cacheUnauthorizedTTL": "30s" } }, "streamingConnectionIdleTimeout": "5m0s", "clusterDomain": "cluster.local", "hairpinMode": "hairpin-veth", "readOnlyPort": 0, "cgroupDriver": "cgroupfs", "cgroupRoot": "/", "featureGates": { "RotateKubeletServerCertificate": true }, "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"] } -
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
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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
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Repeat steps no. 6 - 11 for each worker node running within the selected node pool.
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Repeat steps no. 5 - 12 for each node pool deployed for the selected OKE cluster.
Using OCI CLI
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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"'
-
The command output should return the requested OCI compartment identifiers (OCIDs):
[ "ocid1.tenancy.oc1..aaaabbbbccccddddabcd1234abcd1234abcd1234abcd1234abcd1234abcd", "ocid1.compartment.oc1..abcd1234abcd1234abcd1234abcd1234abcd1234abcd1234abcd1234abcd" ]
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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"'
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The command output should return the requested OKE cluster IDs:
[ "ocid1.cluster.oc1.ap-sydney-1.aaaabbbbccccddddabcd1234abcd1234abcd1234abcd1234abcd1234abcd", "ocid1.cluster.oc1.ap-sydney-1.abcd1234abcd1234abcd1234abcd1234abcd1234abcd1234abcd1234abcd" ]
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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"'
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The command output should return the OKE node pool IDs:
[ "ocid1.nodepool.oc1.ap-sydney-1.abcd1234abcd1234abcd1234abcd1234abcd1234abcd1234abcd1234abcd", "ocid1.nodepool.oc1.ap-sydney-1.aaaabbbbccccddddabcd1234abcd1234abcd1234abcd1234abcd1234abcd" ]
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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"'
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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>" ]
-
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.
-
Once connected to your OKE cluster worker node, edit the kubelet-config.json file for your Kubelet server, to configure the "streamingConnectionIdleTimeout" configuration parameter. You can set the "streamingConnectionIdleTimeout" parameter to a duration between 5 ("5m0s") and 30 minutes ("30m0s"), recommended for high-security or resource-constrained environments, as shown in the example below:
{ "kind": "KubeletConfiguration", "apiVersion": "kubelet.config.k8s.io/v1beta1", "address": "0.0.0.0", "authentication": { "anonymous": { "enabled": false }, "webhook": { "cacheTTL": "2m0s", "enabled": true }, "x509": { "clientCAFile": "/etc/kubernetes/pki/ca.crt" } }, "authorization": { "mode": "Webhook", "webhook": { "cacheAuthorizedTTL": "5m0s", "cacheUnauthorizedTTL": "30s" } }, "streamingConnectionIdleTimeout": "5m0s", "clusterDomain": "cluster.local", "hairpinMode": "hairpin-veth", "readOnlyPort": 0, "cgroupDriver": "cgroupfs", "cgroupRoot": "/", "featureGates": { "RotateKubeletServerCertificate": true }, "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"] } -
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
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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
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Repeat steps no. 9 - 12 for each worker node running within the selected node pool.
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Repeat steps no. 7 - 13 for each node pool deployed for the selected OKE cluster.
References
- Oracle Cloud Infrastructure Documentation
- Overview of Kubernetes Engine (OKE)
- Managing Kubernetes Clusters
- Connecting to an Instance
- Oracle Cloud Infrastructure CLI Documentation
- compartment list
- cluster list
- node-pool list
- node-pool get
- Kubernetes Documentation
- kubelet
- Set Kubelet Parameters Via A Configuration File