Cis Aks V170 3.2.5

3.2.5 Ensure that the --streaming-connection-idle-timeout argument is not set to 0 (Automated)

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• Level 1

Description

Do not disable timeouts on streaming connections.

Rationale

Setting idle timeouts ensures that you are protected against Denial-of-Service attacks, inactive connections and running out of ephemeral ports.

Note: By default, --streaming-connection-idle-timeout is set to 4 hours which might be too high for your environment. Setting this as appropriate would additionally ensure that such streaming connections are timed out after serving legitimate use cases.

Impact

Long-lived connections could be interrupted.

Audit Procedure

Audit Method 1:

First, SSH to the relevant node:

Run the following command on each node to find the running kubelet process:

ps -ef | grep kubelet

If the command line for the process includes the argument streaming-connection-idle-timeout verify that it is not set to 0.

If the streaming-connection-idle-timeout argument is not present in the output of the above command, refer instead to the config argument that specifies the location of the Kubelet config file e.g. --config /etc/kubernetes/kubelet/kubelet-config.json.

Open the Kubelet config file:

cat /etc/kubernetes/kubelet/kubelet-config.json

Verify that the streamingConnectionIdleTimeout argument is not set to 0.

Audit Method 2:

If using the api configz endpoint consider searching for the status of "streamingConnectionIdleTimeout":"4h0m0s" by extracting the live configuration from the nodes running kubelet.

Set the local proxy port and the following variables and provide proxy port number and node name; HOSTNAME_PORT="localhost-and-port-number" NODE_NAME="The-Name-Of-Node-To-Extract-Configuration" from the output of kubectl get nodes

kubectl proxy --port=8001 &

export HOSTNAME_PORT=localhost:8001 (example host and port number)
export NODE_NAME=ip-192.168.31.226.aks.internal (example node name from "kubectl get nodes")

curl -sSL "http://${HOSTNAME_PORT}/api/v1/nodes/${NODE_NAME}/proxy/configz"

Remediation

Remediation Method 1:

If modifying the Kubelet config file, edit the kubelet-config.json file /etc/kubernetes/kubelet/kubelet-config.json and set the below parameter to a non-zero value in the format of #h#m#s:

"streamingConnectionIdleTimeout": "4h0m0s"

You should ensure that the kubelet service file /etc/systemd/system/kubelet.service.d/10-kubelet-args.conf does not specify a --streaming-connection-idle-timeout argument because it would override the Kubelet config file.

Remediation Method 2:

If using executable arguments, edit the kubelet service file /etc/systemd/system/kubelet.service.d/10-kubelet-args.conf on each worker node and add the below parameter at the end of the KUBELET_ARGS variable string.

--streaming-connection-idle-timeout=4h0m0s

Remediation Method 3:

If using the api configz endpoint consider searching for the status of "streamingConnectionIdleTimeout": by extracting the live configuration from the nodes running kubelet.

**See detailed step-by-step configmap procedures in Reconfigure a Node's Kubelet in a Live Cluster, and then rerun the curl statement from audit process to check for kubelet configuration changes.

For all three remediations: Based on your system, restart the kubelet service and check status:

systemctl daemon-reload
systemctl restart kubelet.service
systemctl status kubelet -l

Default Value

See the Azure AKS documentation for the default value.

References

1. https://kubernetes.io/docs/admin/kubelet/
2. https://github.com/kubernetes/kubernetes/pull/18552
3. https://docs.microsoft.com/security/benchmark/azure/security-controls-v2-posture-vulnerability-management#pv-3-establish-secure-configurations-for-compute-resources

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