cis-ocp-v190-4.2.12

DevOps & Security

Ensure that the Kubelet only makes use of Strong Cryptographic Ciphers (Manual)

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CIS Red Hat OpenShift Container Platform Benchmark v1.9.0 - Control 4.2.12

Profile Applicability

Level: 1

Description

Ensure that the Kubelet is configured to only use strong cryptographic ciphers.

Rationale

TLS ciphers have had a number of known vulnerabilities and weaknesses, which can reduce the protection provided by them. By default Kubernetes supports a number of TLS ciphersuites including some that have security concerns, weakening the protection provided.

Impact

Kubelet clients that cannot support modern cryptographic ciphers will not be able to make connections to the Kubelet API.

Audit Procedure

The set of cryptographic ciphers currently considered secure is the following:

TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256
TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256
TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305
TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384
TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305
TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384
TLS_RSA_WITH_AES_256_GCM_SHA384
TLS_RSA_WITH_AES_128_GCM_SHA256

Ciphers for the API servers, authentication and the ingress controller can be configured using the tlsSecurityProfile parameter as of OpenShift 4.3. The ingress controller provides external access to the API server. There are four TLS security profile types:

Old
Intermediate
Modern
Custom

Only the Old, Intermediate and Custom profiles are supported at this time for the Ingress controller. Custom provides the ability to specify individual TLS security profile parameters. Follow the steps in the documentation to configure the cipher suite for Ingress, API server and Authentication.

Run the following commands to verify the cipher suite and minTLSversion for the ingress operator, authentication operator, cliconfig, OpenShift APIserver and Kube APIserver.

Use the following command to verify the available ciphers:

oc get --namespace=openshift-ingress-operator ingresscontroller/default -ojson | jq .status.tlsProfile.ciphers

Verify the ciphers used by the Kubernetes API server:

oc get kubeapiservers.operator.openshift.io cluster -ojson | jq .spec.observedConfig.servingInfo.cipherSuites

Verify the ciphers used by the OpenShift API server:

oc get openshiftapiservers.operator.openshift.io cluster -ojson | jq .spec.observedConfig.servingInfo.cipherSuites

Verify the ciphers used by OpenShift authentication:

oc get cm -n openshift-authentication v4-0-config-system-cliconfig -o jsonpath='{.data.v4\-0\-config\-system\-cliconfig}' | jq .servingInfo.cipherSuites

Verify tlsSecurityProfile is using the default value:

oc get kubeapiservers.operator.openshift.io cluster -ojson | jq .spec.tlsSecurityProfile

Verify that the cipher suites are appropriate.

Verify that the tlsSecurityProfile is set to the value you chose, or using the default of Intermediate.

Note: The HAProxy Ingress controller image does not support TLS 1.3 and because the Modern profile requires TLS 1.3, it is not supported. The Ingress Operator converts the Modern profile to Intermediate. The Ingress Operator also converts the TLS 1.0 of an Old or Custom profile to 1.1, and TLS 1.3 of a Custom profile to 1.2.

Remediation

Follow the directions above and in the OpenShift documentation to configure the tlsSecurityProfile. Configuring Ingress.

Please reference the OpenShift TLS security profile documentation for more detail on each profile.

Default Value

By default the Kubernetes API server supports a wide range of TLS ciphers.

CIS Controls

Controls Version	Control	IG 1	IG 2	IG 3
v8	5.2 Use Unique Passwords	*	*	*
v7	1.8 Utilize Client Certificates to Authenticate Hardware Assets			*
v7	2.6 Address unapproved software	*	*	*

MITRE ATT&CK Mappings

Techniques / Sub-techniques	Tactics	Mitigations

Profile

Level 1 (Manual)