Configuring TLS security profiles

TLS security profiles provide a way for servers to regulate which ciphers a client can use when connecting to the server. This ensures that OpenShift Container Platform components use cryptographic libraries that do not allow known insecure protocols, ciphers, or algorithms.

Cluster administrators can choose which TLS security profile to use for each of the following components:

the Ingress Controller
the control plane

This includes the Kubernetes API server, Kubernetes controller manager, Kubernetes scheduler, OpenShift API server, OpenShift OAuth API server, OpenShift OAuth server, etcd, the Machine Config Operator, and the Machine Config Server.
the kubelet, when it acts as an HTTP server for the Kubernetes API server

Understanding 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:

Table 1. 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.

Viewing TLS security profile details

You can view the minimum TLS version and ciphers for the predefined TLS security profiles for each of the following components: Ingress Controller, control plane, and kubelet.

Important

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):
     ... 

   modern	<>
     modern is a TLS security profile based on:
     https://wiki.mozilla.org/Security/Server_Side_TLS#Modern_compatibility and
     looks like this (yaml):
     ... 
     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):
     ... 

   type	<string>
     ...

Lists ciphers and minimum version for the intermediate profile here.
Lists ciphers and minimum version for the modern profile here.
Lists ciphers and minimum version for the old profile here.

Configuring 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.

Sample IngressController CR that configures the Old TLS security profile

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

Edit the IngressController CR in the openshift-ingress-operator project to configure the TLS security profile:
```
$ oc edit IngressController default -n openshift-ingress-operator
```

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 TLS security profile type (Old, Intermediate, or Custom). The default is Intermediate.
Specify the appropriate field for the selected type:
- old: {}
- intermediate: {}
- modern: {}
- custom:
For the custom type, specify a list of TLS ciphers and minimum accepted TLS version.

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
 ...

Configuring 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

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

Note

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

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

Edit the default APIServer CR to configure the TLS security profile:
```
$ oc edit APIServer cluster
```

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 TLS security profile type (Old, Intermediate, or Custom). The default is Intermediate.
Specify the appropriate field for the selected type:
- old: {}
- intermediate: {}
- modern: {}
- custom:
For the custom type, specify a list of TLS ciphers and minimum accepted TLS version.

Save the file to apply the changes.

Verification

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
 ...

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
 ...

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]
# ...

Configuring the TLS security profile for the kubelet

You can configure a TLS security profile for the kubelet when it is acting as an HTTP server by creating a KubeletConfig custom resource (CR) to specify a predefined or custom TLS security profile for specific nodes.

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

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.

Sample 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

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.
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:

Start a debug session for a configured node:
```
$ oc debug node/<node_name>
```
Set /host as the root directory within the debug shell:
```
sh-4.4# chroot /host
```

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",
#...