SV-242418r1043178: The Kubernetes API server must use approved cipher suites. | Kubernetes STIG SCAP Benchmark

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Assessment Title

Rule Text

The Kubernetes API server must use approved cipher suites.

Description

Discussion Text

The Kubernetes API server communicates to the kubelet service on the nodes to deploy, update, and delete resources. If an attacker were able to get between this communication and modify the request, the Kubernetes cluster could be compromised. Using approved cypher suites for the communication ensures the protection of the transmitted information, confidentiality, and integrity so that the attacker cannot read or alter this communication.

How this relates to the STIG checklist: STIG vs SCAP benchmark.

IA Controls

NIST SP 800-53

Not mappedCCI-001184

References

DPMS Target Kubernetes DISA DPMS Target Kubernetes 5376

Checks

DISA STIG (Manual Reference)

Change to the /etc/kubernetes/manifests/ directory on the Kubernetes Control Plane. Run the command:
grep -i tls-cipher-suites *

If the setting feature tls-cipher-suites is not set in the Kubernetes API server manifest file or contains no value or does not contain TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256,TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256,TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384,TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384, this is a finding.

SCC Automation Reference

The reconstructed evaluation script behind this rule's OVAL check(s) — every module a compound check combines, with this rule's own concrete values and DISA's SCC tool's real per-module mechanism curated from static teardown of SCC releases.

#!/bin/bash
# Reconstructed from oval:mil.disa.stig.kubernetes:def:242418
# The Kubernetes API server must use approved cipher suites.
# Per-module read mechanism curated from static teardown of DISA's SCC tool
# (SCAP Compliance Checker) -- see the SCC Automation Reference above.

# Check /etc/kubernetes/manifests/kube-apiserver.yaml for tls-cipher-suites and that it is defined
# textfilecontent54_object (textfilecontent54_test)
test_1() {
  (sed -En 's/^(?i)[ -]*tls-cipher-suites=([\S]+)[ ]*$/\1/p' '/etc/kubernetes/manifests/kube-apiserver.yaml') | grep -qxF 'TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256,TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256,TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384,TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384'
}

if test_1; then
  echo "PASS"
else
  echo "FAIL"
fi

Remediation

Edit the Kubernetes API Server manifest file in the /etc/kubernetes/manifests directory on the Kubernetes Control Plane. 

Set the value of "--tls-cipher-suites" to:
"TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256,TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256,TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384,TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384"