Profile Applicability:

  • Level 1

Description:
 The kube-proxy service is responsible for maintaining network rules for pod communication. This check ensures that the kube-proxy metrics service is bound to localhost (127.0.0.1) rather than being exposed on an external network interface. Binding the metrics service to localhost ensures that sensitive metrics data is only accessible from within the Kubernetes cluster and prevents external access.

Rationale:
 By binding the kube-proxy metrics service to localhost, you reduce the risk of exposing sensitive cluster performance and diagnostic data to external sources. Metrics can be sensitive, and if exposed publicly or on untrusted networks, they could provide valuable information to attackers, such as resource usage, network latency, and other diagnostic data. Binding it to localhost limits access to cluster administrators and monitoring systems within the cluster.

Impact:

  • Pros:

    • Reduces the risk of sensitive metrics data being exposed to unauthorized users or external networks.

    • Improves the security posture by ensuring that diagnostic information is only accessible from within the cluster.

  • Cons:

    • May require additional configuration if external monitoring tools need to access kube-proxy metrics.

    • Potentially introduces operational overhead in ensuring that metrics can still be accessed for monitoring or alerting purposes, but only from trusted sources.

Default Value:
 By default, kube-proxy metrics may be bound to all interfaces, potentially exposing the data externally if not properly configured.

Pre-requisites:
 Ensure that kube-proxy is properly configured and running with appropriate permissions. Make sure any monitoring tools or systems that need access to kube-proxy metrics can access it from localhost.

Test Plan:

Using Azure Console:

  1. Navigate to the Azure portal and access your Azure Kubernetes Service (AKS) cluster.

  2. Review the kube-proxy configuration to ensure that the metrics service is bound to localhost.

  3. Verify that external access to kube-proxy metrics is restricted, and ensure it is accessible only from within the cluster or by trusted users.

Using Azure CLI:

1. Verify the kube-proxy metrics configuration by checking the kube-proxy settings:

kubectl get configmap kube-proxy -n kube-system -o yaml

2. Check if the metricsBindAddress setting is configured to 127.0.0.1 (localhost):

kubectl describe configmap kube-proxy -n kube-system | grep metricsBindAddress

3. If the metricsBindAddress is not set to localhost, it may indicate an insecure configuration.

Implementation Plan:

Using Azure Console:

  1. In the Azure portal, navigate to your AKS cluster and access the kube-proxy configuration.

  2. Modify the kube-proxy settings to bind the metrics service to localhost by setting the metricsBindAddress configuration to 127.0.0.1.

3. Apply the updated configuration to ensure kube-proxy binds the metrics service to localhost


Using Azure CLI:

1. Modify the kube-proxy DaemonSet to bind the metrics service to localhost:

kubectl set env daemonset/kube-proxy -n kube-system METRICS_BIND_ADDRESS="127.0.0.1"

2. Alternatively, directly edit the kube-proxy DaemonSet configuration and apply the changes:

kubectl edit daemonset kube-proxy -n kube-system

3. In the editor, modify the --metrics-bind-address parameter to 127.0.0.1.

4. Verify that the metricsBindAddress is set to localhost by running the following command:

kubectl get configmap kube-proxy -n kube-system -o yaml | grep metricsBindAddress

Backout Plan:

Using Azure Console:

  1. If restricting the metrics service to localhost causes issues, revert the changes by modifying the kube-proxy configuration to allow external access (e.g., setting metricsBindAddress to 0.0.0.0).

Using Azure CLI:

1. Revert the kube-proxy configuration to allow external access by setting the metricsBindAddress back to the desired IP address (e.g., 0.0.0.0).

kubectl set env daemonset/kube-proxy -n kube-system METRICS_BIND_ADDRESS="0.0.0.0"

2. Apply the changes and verify that the kube-proxy metrics service is accessible externally if necessary.

References:

  1. Kubernetes Kube-Proxy Documentation

  2. Azure Kubernetes Service (AKS) Configuration

  3. Kube-Proxy Metrics Bind Address Configuration