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kubernetes

Etcd pod does not use automatically generated self-signed certificates for peer TLS connections

etcd_no_peer_auto_tls
Service: etcdSeverity: high
OfficialBuilt-inVerified
Categories:encryptioncluster-security
Resource Type:Pod

Etcd peer TLS configuration is evaluated by checking etcd containers for the --peer-auto-tls flag. Presence of --peer-auto-tls indicates peers use automatically generated self-signed certificates for inter-peer connections.

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Risk

With --peer-auto-tls, traffic is encrypted but peer identity isn't verified, enabling:

  • MITM on peer links
  • Rogue member joins to read/modify data
  • Quorum disruption

This degrades confidentiality, integrity, and availability of control-plane state replicated in etcd.

Run this check with Prowler

Run in Prowler Cloud
Run
prowler kubernetes --checks etcd_no_peer_auto_tls

Recommendation

Disable --peer-auto-tls and use mTLS with a trusted CA issuing unique per-member peer certificates. Enforce SAN validation and, where supported, peer certificate authentication. Apply least privilege, separate CAs for peers/clients, rotate keys, and monitor certificate expiry and peer membership.

Remediation

Other

1SSH to the control-plane node running etcd
2Open /etc/kubernetes/manifests/etcd.yaml
3In the etcd container args/command, remove any entry that starts with --peer-auto-tls
4Save the file; the kubelet will restart etcd automatically

Check Code

from prowler.lib.check.models import Check, Check_Report_Kubernetes
from prowler.providers.kubernetes.services.etcd.etcd_client import etcd_client


class etcd_no_peer_auto_tls(Check):
    def execute(self) -> Check_Report_Kubernetes:
        findings = []
        for pod in etcd_client.etcd_pods:
            report = Check_Report_Kubernetes(metadata=self.metadata(), resource=pod)
            report.status = "PASS"
            report.status_extended = f"Etcd is not using automatically generated self-signed certificates for peer TLS connections in pod {pod.name}."
            for container in pod.containers.values():
                if "--peer-auto-tls" in str(
                    container.command
                ) or "--peer-auto-tls=true" in str(container.command):
                    report.status = "FAIL"
                    report.status_extended = f"Etcd is using automatically generated self-signed certificates for TLS connections in pod {pod.name}."
                    break
            findings.append(report)
        return findings

References