Linux Foundation CKS Exam Questions & Answers

Correct Answer: A

Create a PSP that will prevent the creation of privileged pods in the namespace. $ cat clusterrole-use-privileged.yaml apiVersion: rbac.authorization.k8s.io/v1

kind: ClusterRole metadata: name: use-privileged-psp rules:

-apiGroups: ['policy']

resources: ['podsecuritypolicies']

verbs: ['use']

resourceNames:

-default-psp

apiVersion: rbac.authorization.k8s.io/v1 kind: RoleBinding metadata: name: privileged-role-bind namespace: psp-test roleRef: apiGroup: rbac.authorization.k8s.io kind: ClusterRole name: use-privileged-psp subjects:

-kind: ServiceAccount name: privileged-sa $ kubectl -n psp-test apply -f clusterrole-use-privileged.yaml

After a few moments, the privileged Pod should be created.

Create a new PodSecurityPolicy named prevent-privileged-policy which prevents the creation of privileged pods.

apiVersion: policy/v1beta1

kind: PodSecurityPolicy

metadata:

name: example

spec:

privileged: false # Don't allow privileged pods!

# The rest fills in some required fields.

seLinux:

rule: RunAsAny

supplementalGroups:

rule: RunAsAny

runAsUser:

rule: RunAsAny

fsGroup:

rule: RunAsAny

volumes:

-'*'

And create it with kubectl:

kubectl-admin create -f example-psp.yaml

Now, as the unprivileged user, try to create a simple pod:

kubectl-user create -f- <

apiVersion: v1

kind: Pod

metadata:

name: pause

spec:

containers:

-name: pause

image: k8s.gcr.io/pause

EOF

The output is similar to this:

Error from server (Forbidden): error when creating "STDIN": pods "pause" is forbidden:

unable to validate against any pod security policy: []

Create a new ServiceAccount named psp-sa in the namespace default.

$ cat clusterrole-use-privileged.yaml

apiVersion: rbac.authorization.k8s.io/v1 kind: ClusterRole metadata: name: use-privileged-psp rules:

-apiGroups: ['policy']

resources: ['podsecuritypolicies']

verbs: ['use']

resourceNames:

-default-psp

apiVersion: rbac.authorization.k8s.io/v1 kind: RoleBinding metadata: name: privileged-role-bind namespace: psp-test roleRef: apiGroup: rbac.authorization.k8s.io kind: ClusterRole name: use-privileged-psp subjects:

-kind: ServiceAccount name: privileged-sa $ kubectl -n psp-test apply -f clusterrole-use-privileged.yaml After a few moments, the privileged Pod should be created.

Create a new ClusterRole named prevent-role, which uses the newly created Pod Security Policy prevent-privileged-policy.

apiVersion: policy/v1beta1

kind: PodSecurityPolicy

metadata:

name: example

spec:

privileged: false # Don't allow privileged pods!

# The rest fills in some required fields.

seLinux:

rule: RunAsAny

supplementalGroups:

rule: RunAsAny

runAsUser:

rule: RunAsAny

fsGroup:

rule: RunAsAny

volumes:

-'*'

And create it with kubectl:

kubectl-admin create -f example-psp.yaml

Now, as the unprivileged user, try to create a simple pod:

kubectl-user create -f- <

apiVersion: v1

kind: Pod

metadata:

name: pause

spec:

containers:

-name: pause

image: k8s.gcr.io/pause

EOF

The output is similar to this:

Error from server (Forbidden): error when creating "STDIN": pods "pause" is forbidden:

unable to validate against any pod security policy: []

Create a new ClusterRoleBinding named prevent-role-binding, which binds the created ClusterRole prevent-role to the created SA psp-sa.

apiVersion: rbac.authorization.k8s.io/v1

# This role binding allows "jane" to read pods in the "default" namespace. # You need to already have a Role named "pod-reader" in that namespace.

kind: RoleBinding

metadata:

name: read-pods

namespace: default

subjects:

# You can specify more than one "subject"

-kind: User name: jane # "name" is case sensitive apiGroup: rbac.authorization.k8s.io roleRef: # "roleRef" specifies the binding to a Role / ClusterRole kind: Role #this must be Role or ClusterRole name: pod-reader # this must match the name of the Role or ClusterRole you wish to bind to apiGroup: rbac.authorization.k8s.io

apiVersion: rbac.authorization.k8s.io/v1 kind: Role metadata: namespace: default name: pod-reader rules:

-apiGroups: [""] # "" indicates the core API group resources: ["pods"] verbs: ["get", "watch", "list"]

Correct Answer: A

API server:

Ensure the --authorization-mode argument includes RBAC

Turn on Role Based Access Control.Role Based Access Control (RBAC) allows fine- grained control over the operations that different entities can perform on different objects in the cluster. It is recommended to use the RBAC authorization

mode.

Fix - BuildtimeKubernetesapiVersion: v1

kind: Pod

metadata:

creationTimestamp: null

labels:

component: kube-apiserver

tier: control-plane

name: kube-apiserver

namespace: kube-system

spec:

containers:

-command: + - kube-apiserver + - --authorization-mode=RBAC,Node image: gcr.io/google_containers/kube-apiserver-amd64:v1.6.0 livenessProbe: failureThreshold: 8 httpGet: host: 127.0.0.1 path: /healthz port: 6443 scheme: HTTPS initialDelaySeconds: 15 timeoutSeconds: 15 name: kube-apiserver-should-pass resources: requests: cpu: 250m volumeMounts:

-

mountPath: /etc/kubernetes/ name: k8s readOnly: true

-

mountPath: /etc/ssl/certs name: certs

-

mountPath: /etc/pki name: pki hostNetwork: true volumes:

-

hostPath: path: /etc/kubernetes name: k8s

-

hostPath: path: /etc/ssl/certs name: certs

-

hostPath: path: /etc/pki name: pki

Ensure the --authorization-mode argument includes Node

Remediation: Edit the API server pod specification file /etc/kubernetes/manifests/kube- apiserver.yaml on the master node and set the --authorization-mode parameter to a value that includes Node.

--authorization-mode=Node,RBAC

Audit:

/bin/ps -ef | grep kube-apiserver | grep -v grep

Expected result:

'Node,RBAC' has 'Node'

Ensure that the --profiling argument is set to false

Remediation: Edit the API server pod specification file /etc/kubernetes/manifests/kube-apiserver.yaml on the master node and set the below parameter.

--profiling=false

Audit:

/bin/ps -ef | grep kube-apiserver | grep -v grep

Expected result:

'false' is equal to 'false'

Fix all of the following violations that were found against the Kubelet:

uk.co.certification.simulator.questionpool.PList@e3e35a0

Remediation: If using a Kubelet config file, edit the file to set authentication: anonymous:

enabled to false. If using executable arguments, edit the kubelet service file /etc/systemd/system/kubelet.service.d/10-kubeadm.conf on each worker node and set the below parameter in KUBELET_SYSTEM_PODS_ARGS variable.

--anonymous-auth=false

Based on your system, restart the kubelet service. For example:

systemctl daemon-reload

systemctl restart kubelet.service

Audit:

/bin/ps -fC kubelet

Audit Config:

/bin/cat /var/lib/kubelet/config.yaml

Expected result:

'false' is equal to 'false'

2) Ensure that the --authorization-mode argument is set to Webhook.

Audit

docker inspect kubelet | jq -e '.[0].Args[] | match("--authorization- mode=Webhook").string'

Returned Value: --authorization-mode=Webhook

Fix all of the following violations that were found against the ETCD:

a. Ensure that the --auto-tls argument is not set to true

Do not use self-signed certificates for TLS. etcd is a highly-available key value store used by Kubernetes deployments for persistent storage of all of its REST API objects. These objects are sensitive in nature and should not be available to unauthenticated clients. You should enable the client authentication via valid certificates to secure the access to the etcd service.

Fix - BuildtimeKubernetesapiVersion: v1 kind: Pod metadata: annotations: scheduler.alpha.kubernetes.io/critical-pod: "" creationTimestamp: null labels: component: etcd tier: control-plane name: etcd namespace: kube-system spec: containers:

-command:

+ - etcd

+ - --auto-tls=true

image: k8s.gcr.io/etcd-amd64:3.2.18

imagePullPolicy: IfNotPresent

livenessProbe:

exec:

command:

-/bin/sh

- -ec

-ETCDCTL_API=3 etcdctl --endpoints=https://[192.168.22.9]:2379 -- cacert=/etc/kubernetes/pki/etcd/ca.crt

--cert=/etc/kubernetes/pki/etcd/healthcheck-client.crt -- key=/etc/kubernetes/pki/etcd/healthcheck-client.key get foo

failureThreshold: 8

initialDelaySeconds: 15

timeoutSeconds: 15

name: etcd-should-fail

resources: {}

volumeMounts:

-

mountPath: /var/lib/etcd

name: etcd-data

-

mountPath: /etc/kubernetes/pki/etcd

name: etcd-certs

hostNetwork: true

priorityClassName: system-cluster-critical

volumes:

-

hostPath:

path: /var/lib/etcd

type: DirectoryOrCreate

name: etcd-data

-

hostPath:

path: /etc/kubernetes/pki/etcd

type: DirectoryOrCreate

name: etcd-certs

status: {}

Correct Answer: A

se kubectl to create a CSR and approve it.

Get the list of CSRs:

kubectl get csr

Approve the CSR:

kubectl certificate approve myuser

Get the certificateRetrieve the certificate from the CSR:

kubectl get csr/myuser -o yaml

here are the role and role-binding to give john permission to create NEW_CRD resource:

kubectl apply -f roleBindingJohn.yaml --as=john

rolebinding.rbac.authorization.k8s.io/john_external-rosource-rb created

kind: RoleBinding

apiVersion: rbac.authorization.k8s.io/v1

metadata:

name: john_crd

namespace: development-john

subjects:

-kind: User name: john apiGroup: rbac.authorization.k8s.io roleRef: kind: ClusterRole name: crd-creation

kind: ClusterRole apiVersion: rbac.authorization.k8s.io/v1 metadata: name: crd-creation rules:

-apiGroups: ["kubernetes-client.io/v1"] resources: ["NEW_CRD"] verbs: ["create, list, get"]