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kubernetes

API server pod has --etcd-certfile and --etcd-keyfile configured for etcd TLS

apiserver_etcd_tls_config
Service: apiserverSeverity: critical
OfficialBuilt-inVerified
Categories:encryptioncluster-security
Resource Type:Pod

Kubernetes API server uses TLS for its etcd client connection, signaled by --etcd-certfile and --etcd-keyfile in the API server pod arguments.

This evaluates whether client-certificate authentication is configured between the API server and etcd.

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Risk

Without TLS and client certs, API server-etcd traffic can be intercepted or altered, compromising confidentiality (Secrets, tokens), integrity (state tampering), and availability (control-plane instability). Attackers could perform MITM, exfiltrate data, or inject state to seize cluster control.

Run this check with Prowler

Run in Prowler Cloud
Run
prowler kubernetes --checks apiserver_etcd_tls_config

Recommendation

Enforce mutual TLS between API server and etcd with trusted CAs and unique client certificates. Restrict etcd network access to control-plane nodes, rotate keys, and monitor certificate expiry. Apply least privilege and defense in depth using private networking and firewall policies.

Remediation

Other

1SSH to each control plane node
2Edit /etc/kubernetes/manifests/kube-apiserver.yaml
3In spec.containers[0].command add:
4- --etcd-certfile=<path/to/client-certificate-file>
5- --etcd-keyfile=<path/to/client-key-file>
6Save the file; the kubelet will restart the API server with the new flags

Check Code

from prowler.lib.check.models import Check, Check_Report_Kubernetes
from prowler.providers.kubernetes.services.apiserver.apiserver_client import (
    apiserver_client,
)


class apiserver_etcd_tls_config(Check):
    def execute(self) -> Check_Report_Kubernetes:
        findings = []
        for pod in apiserver_client.apiserver_pods:
            report = Check_Report_Kubernetes(metadata=self.metadata(), resource=pod)
            report.status = "PASS"
            report.status_extended = (
                f"TLS configuration for etcd is set appropriately in pod {pod.name}."
            )
            etcd_tls_config_set = True
            for container in pod.containers.values():
                # Check if "--etcd-certfile" and "--etcd-keyfile" are set
                if "--etcd-certfile" not in str(
                    container.command
                ) and "--etcd-keyfile" not in str(container.command):
                    etcd_tls_config_set = False
                    break

            if not etcd_tls_config_set:
                report.status = "FAIL"
                report.status_extended = (
                    f"TLS configuration for etcd is not set in pod {pod.name}."
                )

            findings.append(report)
        return findings

References