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Configuring TLS security profiles

To enforce secure cryptographic libraries for the OpenShift Container Platform components, cluster administrators can configure TLS security profiles to control cipher usage when the client connects to the Ingress Controller, the control plane, or the kubelet.

The control plane includes the following components:

  • Kubernetes API server
  • Kubernetes controller manager
  • Kubernetes scheduler
  • OpenShift API server
  • OpenShift OAuth API server
  • OpenShift OAuth server
  • etcd
  • Machine Config Operator
  • Machine Config Server.

Understand TLS security profiles

You can use a TLS (Transport Layer Security) security profile, as described in this section, to define which TLS ciphers are required by various OpenShift Container Platform components.

The OpenShift Container Platform TLS security profiles are based on Mozilla recommended configurations.

You can specify one of the following TLS security profiles for each component:

TLS security profiles

Profile Description
Old This profile is intended for use with legacy clients or libraries. The profile is based on the Old backward compatibility recommended configuration.

The Old profile requires a minimum TLS version of 1.0.

Note

For the Ingress Controller, the minimum TLS version is converted from 1.0 to 1.1.
Intermediate This profile is the default TLS security profile for the Ingress Controller, kubelet, and control plane. The profile is based on the Intermediate compatibility recommended configuration.

The Intermediate profile requires a minimum TLS version of 1.2.

Note

This profile is the recommended configuration for the majority of clients.
Modern This profile is intended for use with modern clients that have no need for backwards compatibility. This profile is based on the Modern compatibility recommended configuration.

The Modern profile requires a minimum TLS version of 1.3.
Custom This profile allows you to define the TLS version and ciphers to use.

Warning

Use caution when using a Custom profile, because invalid configurations can cause problems.

Note

When using one of the predefined profile types, the effective profile configuration is subject to change between releases. For example, given a specification to use the Intermediate profile deployed on release X.Y.Z, an upgrade to release X.Y.Z+1 might cause a new profile configuration to be applied, resulting in a rollout.

View TLS security profile details

To check the minimum TLS version and ciphers that a security profile applies in OpenShift Container Platform, you can inspect the profile configuration for the Ingress Controller, control plane, or kubelet. Use the oc explain command to display settings for a predefined or custom profile.

Warning

The effective configuration of minimum TLS version and list of ciphers for a profile might differ between components.

Procedure

  • View details for a specific TLS security profile:

    $ oc explain <component>.spec.tlsSecurityProfile.<profile>

  • For <component>, specify ingresscontroller, apiserver, or kubeletconfig. For <profile>, specify old, intermediate, or custom.

    For example, to check the ciphers included for the intermediate profile for the control plane:

    $ oc explain apiserver.spec.tlsSecurityProfile.intermediate
    Example output
    KIND:     APIServer
VERSION:  config.openshift.io/v1

DESCRIPTION:
    intermediate is a TLS security profile based on:
    https://wiki.mozilla.org/Security/Server_Side_TLS#Intermediate_compatibility_.28recommended.29
    and looks like this (yaml):
    ciphers: - TLS_AES_128_GCM_SHA256 - TLS_AES_256_GCM_SHA384 -
    TLS_CHACHA20_POLY1305_SHA256 - ECDHE-ECDSA-AES128-GCM-SHA256 -
    ECDHE-RSA-AES128-GCM-SHA256 - ECDHE-ECDSA-AES256-GCM-SHA384 -
    ECDHE-RSA-AES256-GCM-SHA384 - ECDHE-ECDSA-CHACHA20-POLY1305 -
    ECDHE-RSA-CHACHA20-POLY1305 - DHE-RSA-AES128-GCM-SHA256 -
    DHE-RSA-AES256-GCM-SHA384 minTLSVersion: TLSv1.2

  • View all details for the tlsSecurityProfile field of a component:

    $ oc explain <component>.spec.tlsSecurityProfile

  • For <component>, specify ingresscontroller, apiserver, or kubeletconfig.

    For example, to check all details for the tlsSecurityProfile field for the Ingress Controller:

    $ oc explain ingresscontroller.spec.tlsSecurityProfile
    Example output
    KIND:     IngressController
VERSION:  operator.openshift.io/v1

RESOURCE: tlsSecurityProfile <Object>

DESCRIPTION:
     ...

FIELDS:
   custom   <>
     custom is a user-defined TLS security profile. Be extremely careful using a
     custom profile as invalid configurations can be catastrophic. An example
     custom profile looks like this:
     ciphers: - ECDHE-ECDSA-CHACHA20-POLY1305 - ECDHE-RSA-CHACHA20-POLY1305 -
     ECDHE-RSA-AES128-GCM-SHA256 - ECDHE-ECDSA-AES128-GCM-SHA256 minTLSVersion:
     TLSv1.1

   intermediate <>
     intermediate is a TLS security profile based on:
     https://wiki.mozilla.org/Security/Server_Side_TLS#Intermediate_compatibility_.28recommended.29
     and looks like this (yaml):
     (A list of ciphers and the minimum version for the intermediate profile opens here.)

   modern   <>
     modern is a TLS security profile based on:
     https://wiki.mozilla.org/Security/Server_Side_TLS#Modern_compatibility and
     looks like this (yaml):
     (A list of ciphers and the minimum version for the modern profile opens here.)
     NOTE: Currently unsupported.

   old  <>
     old is a TLS security profile based on:
     https://wiki.mozilla.org/Security/Server_Side_TLS#Old_backward_compatibility
     and looks like this (yaml):
     (A list of ciphers and the minimum version for the old profile opens here.)

   type <string>
     ...

Configure the TLS security profile for the Ingress Controller

To configure a TLS security profile for an Ingress Controller, edit the IngressController custom resource (CR) to specify a predefined or custom TLS security profile.

If a TLS security profile is not configured, the default value is based on the TLS security profile set for the API server, as shown in the following example:

apiVersion: operator.openshift.io/v1
kind: IngressController
 ...
spec:
  tlsSecurityProfile:
    old: {}
    type: Old

The TLS security profile defines the minimum TLS version and the TLS ciphers for TLS connections for Ingress Controllers.

You can see the ciphers and the minimum TLS version of the configured TLS security profile in the IngressController custom resource (CR) under Status.Tls Profile and the configured TLS security profile under Spec.Tls Security Profile. For the Custom TLS security profile, the specific ciphers and minimum TLS version are listed under both parameters.

Note

The HAProxy Ingress Controller image supports TLS 1.3 and the Modern profile.

The Ingress Operator also converts the TLS 1.0 of an Old or Custom profile to 1.1.

Prerequisites

  • You have access to the cluster as a user with the cluster-admin role.

Procedure

  1. Edit the IngressController CR in the openshift-ingress-operator project to configure the TLS security profile:

    $ oc edit IngressController default -n openshift-ingress-operator.

  2. Add the spec.tlsSecurityProfile field:

    Sample IngressController CR for a Custom profile
    apiVersion: operator.openshift.io/v1
kind: IngressController
 ...
spec:
  tlsSecurityProfile:
    type: Custom
    custom:
      ciphers:
      - ECDHE-ECDSA-CHACHA20-POLY1305
      - ECDHE-RSA-CHACHA20-POLY1305
      - ECDHE-RSA-AES128-GCM-SHA256
      - ECDHE-ECDSA-AES128-GCM-SHA256
      minTLSVersion: VersionTLS11
 ...
    • Specify the value for the spec.tlsSecurityProfile parameter. The TLS security profile types are Old, Intermediate, or Custom. The default type is Intermediate.
    • Specify the appropriate field for the selected spec.tlsSecurityProfile.type. The fields are old: {}, intermediate: {}, modern: {}, or custom:.
    • For the custom type, specify a list of TLS ciphers and the minimum accepted TLS version.

  3. Save the file to apply the changes.

Verification

  • Verify that the profile is set in the IngressController CR:

    $ oc describe IngressController default -n openshift-ingress-operator
    Example output
    Name:         default
Namespace:    openshift-ingress-operator
Labels:       <none>
Annotations:  <none>
API Version:  operator.openshift.io/v1
Kind:         IngressController
 ...
Spec:
 ...
  Tls Security Profile:
    Custom:
      Ciphers:
        ECDHE-ECDSA-CHACHA20-POLY1305
        ECDHE-RSA-CHACHA20-POLY1305
        ECDHE-RSA-AES128-GCM-SHA256
        ECDHE-ECDSA-AES128-GCM-SHA256
      Min TLS Version:  VersionTLS11
    Type:               Custom
 ...

Configure the TLS security profile for the control plane

To configure a TLS security profile for the control plane, edit the APIServer custom resource (CR) to specify a predefined or custom TLS security profile.

Setting the TLS security profile in the APIServer CR propagates the setting to the following control plane components:

  • Kubernetes API server
  • Kubernetes controller manager
  • Kubernetes scheduler
  • OpenShift API server
  • OpenShift OAuth API server
  • OpenShift OAuth server
  • etcd
  • Machine Config Operator
  • Machine Config Server

Note

The default TLS security profile for the Ingress Controller is based on the TLS security profile set for the API server.

If a TLS security profile is not configured, the default TLS security profile is Intermediate.

The following YAML is a sample APIServer CR that configures the Old TLS security profile.

apiVersion: config.openshift.io/v1
kind: APIServer
 ...
spec:
  tlsSecurityProfile:
    old: {}
    type: Old
 ...

The TLS security profile defines the minimum TLS version and the TLS ciphers required to communicate with the control plane components.

You can see the configured TLS security profile in the APIServer custom resource (CR) under Spec.Tls Security Profile. For the Custom TLS security profile, the specific ciphers and minimum TLS version are listed.

Prerequisites

  • You have access to the cluster as a user with the cluster-admin role.

Procedure

  1. Edit the default APIServer CR to configure the TLS security profile:

    $ oc edit APIServer cluster

  2. Add the spec.tlsSecurityProfile field:

    Sample APIServer CR for a Custom profile
    apiVersion: config.openshift.io/v1
kind: APIServer
metadata:
  name: cluster
spec:
  tlsSecurityProfile:
    type: Custom
    custom:
      ciphers:
      - ECDHE-ECDSA-CHACHA20-POLY1305
      - ECDHE-RSA-CHACHA20-POLY1305
      - ECDHE-RSA-AES128-GCM-SHA256
      - ECDHE-ECDSA-AES128-GCM-SHA256
      minTLSVersion: VersionTLS11
    • Specify the value for the spec.tlsSecurityProfile.type parameter. The TLS security profile types are Old, Intermediate, or Custom. The default type is Intermediate.
    • Specify the appropriate field for the selected spec.tlsSecurityProfile. The fields are old: {}, intermediate: {}, modern: {}, or custom:.
    • For the custom type, specify a list of TLS ciphers and the minimum accepted TLS version.

  3. Save the file to apply the changes.

Verification

  1. Verify that the TLS security profile is set in the APIServer CR:

    $ oc describe apiserver cluster
    Example output
    Name:         cluster
Namespace:
 ...
API Version:  config.openshift.io/v1
Kind:         APIServer
 ...
Spec:
  Audit:
    Profile:  Default
  Tls Security Profile:
    Custom:
      Ciphers:
        ECDHE-ECDSA-CHACHA20-POLY1305
        ECDHE-RSA-CHACHA20-POLY1305
        ECDHE-RSA-AES128-GCM-SHA256
        ECDHE-ECDSA-AES128-GCM-SHA256
      Min TLS Version:  VersionTLS11
    Type:               Custom
 ...

  2. Verify that the TLS security profile is set in the etcd CR:

    $ oc describe etcd cluster
    Example output
    Name:         cluster
Namespace:
 ...
API Version:  operator.openshift.io/v1
Kind:         Etcd
 ...
Spec:
  Log Level:         Normal
  Management State:  Managed
  Observed Config:
    Serving Info:
      Cipher Suites:
        TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256
        TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256
        TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384
        TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384
        TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305_SHA256
        TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305_SHA256
      Min TLS Version:           VersionTLS12
 ...

  3. Verify that the TLS security profile is set in the Machine Config Server pod:

    $ oc logs machine-config-server-5msdv -n openshift-machine-config-operator
    Example output
    # ...
I0905 13:48:36.968688       1 start.go:51] Launching server with tls min version: VersionTLS12 & cipher suites [TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256 TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384 TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305_SHA256 TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305_SHA256]
# ...

Configure the TLS security profile for the kubelet

To configure TLS ciphers and minimum versions for the kubelet HTTP server in OpenShift Container Platform, apply a predefined or custom TLS security profile through a KubeletConfig custom resource (CR). Without a custom profile, the kubelet defaults to the Intermediate profile.

  • The kubelet uses its HTTP/GRPC server to communicate with the Kubernetes API server, which sends commands to pods, gathers logs, and run exec commands on pods through the kubelet.

The following example is a KubeletConfig CR that configures the Old TLS security profile on worker nodes:

apiVersion: machineconfiguration.openshift.io/v1
kind: KubeletConfig
# ...
spec:
  tlsSecurityProfile:
    old: {}
    type: Old
  machineConfigPoolSelector:
    matchLabels:
      pools.operator.machineconfiguration.openshift.io/worker: ""
# ...

You can see the ciphers and the minimum TLS version of the configured TLS security profile in the kubelet.conf file on a configured node.

Prerequisites

  • You are logged in to OpenShift Container Platform as a user with the cluster-admin role.

Procedure

  1. Create a KubeletConfig CR to configure the TLS security profile:

    Sample KubeletConfig CR for a Custom profile
    apiVersion: machineconfiguration.openshift.io/v1
kind: KubeletConfig
metadata:
  name: set-kubelet-tls-security-profile
spec:
  tlsSecurityProfile:
    type: Custom
    custom:
      ciphers:
      - ECDHE-ECDSA-CHACHA20-POLY1305
      - ECDHE-RSA-CHACHA20-POLY1305
      - ECDHE-RSA-AES128-GCM-SHA256
      - ECDHE-ECDSA-AES128-GCM-SHA256
      minTLSVersion: VersionTLS11
  machineConfigPoolSelector:
    matchLabels:
      pools.operator.machineconfiguration.openshift.io/worker: ""
#...

    where:

    spec.tlsSecurityProfile.type
    Specifies the TLS security profile type (Old, Intermediate, or Custom). The default is Intermediate.
    spec.tlsSecurityProfile.type.custom
    Specifies the appropriate field for the selected type: * old: {} * intermediate: {} * modern: {} * custom:
    spec.tlsSecurityProfile.type.custom
    For the custom type, specifies a list of TLS ciphers and the minimum accepted TLS version.
    spec.machineConfigPoolSelector.matchLabels.custom
    Specifies the machine config pool label for the nodes you want to apply the TLS security profile. This parameter is optional.

  2. Create the KubeletConfig object:

    $ oc create -f <filename>

    Depending on the number of worker nodes in the cluster, wait for the configured nodes to be rebooted one by one.

Verification

To verify that the profile is set, perform the following steps after the nodes are in the Ready state:

  1. Start a debug session for a configured node:

    $ oc debug node/<node_name>

  2. Set /host as the root directory within the debug shell:

    sh-4.4# chroot /host

  3. View the kubelet.conf file:

    sh-4.4# cat /etc/kubernetes/kubelet.conf
    Example output
      "kind": "KubeletConfiguration",
  "apiVersion": "kubelet.config.k8s.io/v1beta1",
#...
  "tlsCipherSuites": [
    "TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256",
    "TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256",
    "TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384",
    "TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384",
    "TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305_SHA256",
    "TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305_SHA256"
  ],
  "tlsMinVersion": "VersionTLS12",
#...