SV-242424r1043178: Kubernetes Kubelet must enable tlsPrivateKeyFile for client authentication to secure service. | Kubernetes STIG SCAP Benchmark

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Assessment Title

Rule Text

Kubernetes Kubelet must enable tlsPrivateKeyFile for client authentication to secure service.

Description

Discussion Text

Kubernetes container and pod configuration are maintained by Kubelet. Kubelet agents register nodes with the API Server, mount volume storage, and perform health checks for containers and pods. Anyone who gains access to Kubelet agents can effectively control applications within the pods and containers. Using authenticity protection, the communication can be protected against man-in-the-middle attacks/session hijacking and the insertion of false information into sessions. The communication session is protected by utilizing transport encryption protocols such as TLS. TLS provides the Kubernetes API Server with a means to authenticate sessions and encrypt traffic. To enable encrypted communication for Kubelet, the tlsPrivateKeyFile must be set. This parameter gives the location of the SSL Certificate Authority file used to secure Kubelet 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)

On the Control Plane, run the command:
ps -ef | grep kubelet

If the "--tls-private-key-file" option exists, this is a finding. 

Note the path to the config file (identified by --config).

Run the command:
grep -i tlsPrivateKeyFile <path_to_config_file>

If the setting "tlsPrivateKeyFile" is not set or contains no value, 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:242424
# Kubernetes Kubelet must enable tlsPrivateKeyFile for client authentication to secure service.
# Per-module read mechanism curated from static teardown of DISA's SCC tool
# (SCAP Compliance Checker) -- see the SCC Automation Reference above.

# textfilecontent54_object (textfilecontent54_test)
test_1() {
  grep -P '^[^#\n]*\btlsPrivateKeyFile:[ ]*\S+'  &>/dev/null
}
# process58_object (process58_test)
test_2() {
  ! ( ps -eo args | grep -P '/usr/bin/kubelet\b.*--tls-private-key-file\b' &>/dev/null )
}

if ( test_1 && test_2 ); then
  echo "PASS"
else
  echo "FAIL"
fi

Remediation

On the Control Plane, run the command:
ps -ef | grep kubelet

Remove the "--tls-private-key-file" option if present.

Note the path to the config file (identified by --config).

Edit the Kubernetes Kubelet config file: 
Set "tlsPrivateKeyFile" to  a path containing the appropriate private key. 

Restart the kubelet service using the following command:
systemctl daemon-reload && systemctl restart kubelet