CKS考试总结

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修改于 2021-12-24 18:06:47

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修改于 2021-12-24 18:06:47

背景

cks考试资格是去年活动时候跟cka一起买的 1200左右大洋吧...考了两次，第一次57分。我考！第二次 62分，竟然还是没有过去....可能冥冥之中自己有所感应，今年活动的时候购买了一次机会备用的........好歹第三次算是过了86分还好......

总结一下15个题吧！

具体可参考昕光xg大佬的博客CKS认证--CKS 2021最新真题考试经验分享--练习题04。顺序记不太清了，就按照昕光xg大佬列的题目记录一下解题思路吧！墙裂推荐大佬的博客。满满的都是干货！

1. RuntimeClass gVisor

根据题目内容创建一个RuntimeClass，然后修改统一namespace下的pod

参照：官方文档https://kubernetes.io/docs/concepts/containers/runtime-class/#usage%3Cbr%3E

vim /home/cloud_user/sandbox.yml
apiVersion: node.k8s.io/v1
kind: RuntimeClass
metadata:
  name: sandbox
handler: runsc
kubectl apply -f /home/xxx/sandbox.yml

修改xxxx namespace下 pod的runtimeClassName: sandbox

kubectl  -n xxx edit deployments.apps work01 # runtimeClassName: sandbox
kubectl  -n xxx edit deployments.apps work02
kubectl  -n xxx edit deployments.apps work03

基本就是这样的修改3个deployments。增加runtimeClassName: sandbox！等待pod重建完成！

如何确定修改成功呢？

kubectl -n xxx exec xxx -- dmesg

or kubectl get deployments xxx -n xxx -o yaml|grep runtime就可以吧？

2. NetworkPolicy, 限制指定pod、ns 访问指定labels的一组pod

这个题貌似一直是没有变的，网上也看了好多的解题方法但是貌似都是有问题的

在development命名空间内，创建名为pod-access的NetworkPolicy作用于名为products-service的Pod，只允许命名空间为test的Pod或者在任何命名空间内有environment:staging标签的Pod来访问。

当然了namespace 和podname networkpolicy的名字会变

重要的是确定pod namespace的labels

kubectl get pods -n development --show-labels
kubectl get ns --show-labels

cat network-policy.yaml

apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
  name: pod-access
  namespace: development
spec:
  podSelector:
    matchLabels:
       environment: staging
  policyTypes:
  - Ingress
  ingress:
  - from: #命名空间有name: testing标签的Pod
    - namespaceSelector:
        matchLabels:
          name: testing
  - from:  #所有命名空间有environment: staging标签的Pod
    - namespaceSelector:
        matchLabels:
      podSelector:
        matchLabels:
           environment: staging

kubectl apply -f network-policy.yaml

官方文档参考：https://kubernetes.io/docs/concepts/services-networking/network-policies/

3. NetworkPolicy，dany all Ingress Egress

考了两次，这个题会变但是无非是创建名为 denynetwork 的 NetworkPolicy，拒绝development命名空间内所有Ingress流量or Egress or Ingress and Egress流量

参照：https://kubernetes.io/docs/concepts/services-networking/network-policies/#default-deny-all-ingress-and-all-egress-traffic

注意审题看题目中的要求！

---
apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
  name: denynetwork 
  namespace： development
spec:
  podSelector: {}
  policyTypes:
  - Ingress

---
apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
  name: denynetwork 
  namespace： development
spec:
  podSelector: {}
  policyTypes:
  - Egress

---
apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
  name: denynetwork 
  namespace： development
spec:
  podSelector: {}
  policyTypes:
  - Ingress
  - Egress

4. trivy 检测镜像

kubectl -n development get pods
kubectl -n development get pods --output=custom-columns="NAME:.metadata.name,IMAGE:.spec.containers[*].image"
NAME       IMAGE
work1      busybox:1.33.1
work2      nginx:1.14.2
work3      amazonlinux:2
work4      amazonlinux:1
work5      centos:7
trivy image -s HIGH,CRITICAL busybox:1.33.1
trivy image -s HIGH,CRITICAL nginx:1.14.2 #HIGH and CRITICAL
trivy image -s HIGH,CRITICAL amazonlinux:2
trivy image -s HIGH,CRITICAL amazonlinux:1
trivy image -s HIGH,CRITICAL centos:7 #HIGH and CRITICAL

我考试题目中是有两个镜像 centos的镜像不符合要求把对应pod删除即可

https://kubernetes.io/zh/docs/reference/kubectl/cheatsheet/#%E6%A0%BC%E5%BC%8F%E5%8C%96%E8%BE%93%E5%87%BA

5. kube-bench，修复不安全项

这个题目也比较稳就是根据bue-bench对master节点进行修复，基本就是老一套。根据题目中提示基本没有什么问题！

kube-apiserver

vim /etc/kubernetes/manifests/kube-apiserver.yaml
- --authorization-mode=Node,RBAC

kubelet

vim /var/lib/kubelet/config.yaml
authentication:
  anonymous:
    enabled: false
  webhook:
    enabled: true
authorization:
  mode: Webhook
protectKernelDefaults: true

systemctl restart kubelet.service
systemctl status kubelet.service

etcd

mv /etc/kubernetes/manifests/etcd.yaml /etc/kubernetes/
vim /etc/kubernetes/etcd.yaml
- --client-cert-auth=true

这个题也很刺激。我进入master节点发现kuberentes环境竟然没有启动...what.我修改了配置文件后还是没有起来...中间我的vpn断网了。然后检查的时候环境竟然好了。莫名其妙的......

6. clusterrole

这里考了两次也都会细微的改变。但是无非是以下三个步骤

修改namespace下role的权限只允许对某一类对象做list list的操作# kubectl -n db get role

NAME       ROLE          AGE
sa-dev-1   Role/role-1   7d16h

# kubectl -n db edit role role-1
apiVersion: rbac.authorization.k8s.io/v1
kind: Role
metadata:
  name: role-1
  namespace: db
  selfLink: /apis/rbac.authorization.k8s.io/v1/namespaces/db/roles/role-1
rules:
- apiGroups:
  - ""
  resources:
  - endpoints  #只允许对endpoints资源list
  verbs:
  - list

kubectl -n db create role role-2 --resource=persistentvolumeclaims --verb=update
kubectl create rolebinding role-2-binding --role=role-2 --serviceaccount=db:service-account-web -n db7. serviceAccount在qa命名空间内创建ServiceAccount frontend-sa，不允许访问任何secrets。创建名为frontend-sa的Pod使用该ServiceAccount。并删除qa命名空间下没有使用的sa
参照：https://kubernetes.io/docs/tasks/configure-pod-container/configure-service-account/apiVersion: v1
kind: ServiceAccount
metadata:
  name: frontend-sa
  namespace： qa
automountServiceAccountToken: false
...apiVersion: v1
kind: Pod
metadata:
  name: my-pod
  namespace: qa 
spec:
  serviceAccountName: frontend-sa
  automountServiceAccountToken: false

...kubectl get sa -n qa 应该是有三个sa frontend-sa default 还有另外一个正常应该是保留frontend-sa 删除另外两个？但是default有必要删除吗？哈哈哈哈这个地方有点徘徊！我貌似8. Dockerfile 和 Pod yaml 检测这个地方也有点郁闷啊。不是每个文件中让修改两处吗？Dockerfile中我是不是要修改三处呢？题目中注明了基础镜像是ubuntu：16.04 但是给的文件中是latest应该是要修改的吧？ Dockerfile: 去掉两处 USER root 设置基础镜像为 ubuntu:16.04 Pod yaml: 注释掉 privileged 那一行的相关配置https://docs.docker.com/develop/develop-images/dockerfile_best-practices/#from9. secretistio-system 命名空间中有一个名称为 db1-test 的 secret，按照要求完成如下内容：

新建一个serviceaccount
创建名为role-2的role，并且通过rolebinding绑定sa-dev-1，只允许对persistentvolumeclaims做update操作。
存储 username 字段到 /home/candidate/user.txt 文件 , password 字段到 /home/candidate/old_pass.txt 文件。用户需要自己创建文件。
创建secret from user password。
将secret挂载到pod中。

在 istio-system 命名空间创建名称为 db2-test 的 secret，其包含如下内容:

pod name secret-pod
namespace istio-system
container name dev-container
image nginx  ###也可能是httpd我考的几次都碰到过
volume name secret-volume
mount path /etc/secret

1. 将secrets base 64写入文件

很多解题都用了kubectl jsonpath的方式个人比较笨就用了传统的方式：

kubectl get secrets -n istio-system db1-test -o yaml
echo "" |base64 -d > /home/candidate/old_pass.txt
echo "" |base64 -d > /home/candidate/user.txt

注意顺序查看secrets的时候貌似password都在上面，个人习惯总是容易先搞username。还是容易搞混的

2. 生成secret

参照：https://kubernetes.io/docs/tasks/configmap-secret/managing-secret-using-kubectl/

kubectl create secret generic db2-test -n istio-system \
--from-literal=username=production-instance \
--from-literal=password=KvLftKgs4aHV

3 . secret 挂载到pod中

apiVersion: v1
kind: Pod
metadata:
  name: secret-pod
  namespace: istio-system
spec:
  containers:
  - name: dev-container
    image: nginx  ###我的是httpd
    volumeMounts:
- name: secret-volume
mountPath: "/etc/secret"
readOnly: true
volumes:
- name: secret-volume
secret:
secretName: db2-test

10. PodSecurityPolicy

基本就是参照官方：

创建名为 restrict-policy的PodSecurityPolicy，阻止创建privileged Podvim restrict-policy.yml

apiVersion: policy/v1beta1
kind: PodSecurityPolicy
metadata:
  name: restrict-policy
spec:
  privileged: false  ###一定要记得这里false吧？
  runAsUser:
    rule: "RunAsAny"
  fsGroup:
    rule: "RunAsAny"
  seLinux:
    rule: "RunAsAny"
  supplementalGroups:
    rule: "RunAsAny"
kubectl apply -f restrict-policy.yml

创建名为 restrict-access-role 的ClusterRole允许使用新创建的名为 restrict-policy 的PodSecurityPolicy。
在staging命名空间中创建名为 psp-denial-sa 的serviceAccount。
创建名为deny-access-bind的clusterRoleBinding，绑定刚刚创建的serviceAccount和ClusterRole。

kubectl create clusterrole restrict-access-role --verb=use --resource=psp --resource-name=restrict-policy
kubectl create sa psp-denial-sa -n staging
kubectl create clusterrolebinding deny-access-bind --clusterrole=restrict-access-role --serviceaccount=staging:psp-denial-sa

注:参考https://kubernetes.io/docs/concepts/policy/pod-security-policy/#volumes-and-file-systems

11. Container(容器)安全 ,删除包含Volumes或privileged 的pod

查看production namespace下所有pod是否有特权 Privileged 或者挂载 volume 的 pod

kubectl get pods NAME -n  production -o jsonpath={.spec.volumes} | jq
kubectl get pods NAME -o yaml -n  production | grep "privi.*: true"

然后删除 Privileged 或者挂载 volume 的 Pod。应该是有3个pod 要删除两个？

12. audit--日志审计

日志审计这个地方很刺激。不知道为什么我改了前两次都没有起来...

现在回想一下我默认的人家写好的都删了这应该是不对的:

basic policy is provided at /etc/kubernetes/logpolicy'sample-policy.yaml . It onlyspecifies what not to log----指定不记录到日志中的内容

namespaces changes at RequestResponse level apiVersion: audit.k8s.io/v1 # This is required.
kind: Policy
omitStages:
  - "RequestReceived"
rules:
  # 保留指定不记录到日志中的内容（原配置文件内容）
  - level: RequestResponse
    resources:
    - group: ""
      resources: ["namespaces"]
  - level: Request
    resources:
    - group: "" 
      resources: ["persistentvolumes"]
    namespaces: ["front-apps"]

  - level: Metadata
    resources:
    - group: "" # core API group
      resources: ["secrets", "configmaps"]
  - level: Metadata
    omitStages:
      - "RequestReceived"kube-apiserver.yaml  配置文件路径，log路径  最大保留天数，保留的审计日志文件的最大数量vim /etc/kubernetes/manifests/kube-apiserver.yaml
- --audit-policy-file=/etc/kubernetes/audit-policy.yaml
- --audit-log-path=/var/log/kubernetes/audit.log
- --audit-log-maxage=10
- --audit-log-maxbackup=1重启服务并验证systemctl restart kubelet
kubectl apply -f xxx.yaml
tail -f /var/log/kubernetes/audit.log注： 修改之前先做好备份！谨记参照官方：https://kubernetes.io/docs/tasks/debug-application-cluster/audit/。文件的挂载环境中已配置好了不用修改添加的。
the request body of persistentwolumes changes inthe namespace front-apps
ConfigMap and Secret changes in all namespaces atthe Metadata levelcat /etc/kubernetes/logpolicy/sample-policy.yaml

13. image policy

参照：https://kubernetes.io/docs/reference/access-authn-authz/admission-controllers/

admission-control.conf or|dmission-control.yaml

vim /etc/kubernetes/admission-control/admission-control.conf
apiVersion: apiserver.config.k8s.io/v1
kind: AdmissionConfiguration
plugins:
- name: ImagePolicyWebhook
  path: imagepolicy.conf

imagepolicy.conf | imagepolicy.json

vim /etc/kubernetes/admission-control/imagepolicy.conf
{
   "imagePolicy": {
      "kubeConfigFile": "/etc/kubernetes/admission-control/imagepolicy_backend.kubeconfig",
      "allowTTL": 50,
      "denyTTL": 50,
      "retryBackoff": 500,
      "defaultAllow": false 
   }
}
注： 只修改了defaultAllow true为false!

imagepolicy_backend.kubeconfig

vim /etc/kubernetes/admission-control/imagepolicy_backend.kubeconfig
apiVersion: v1
kind: Config
clusters:
- name: trivy-k8s-webhook
  cluster:
    certificate-authority: /etc/kubernetes/admission-control/imagepolicywebhook-ca.crt
    server: https://acg.trivy.k8s.webhook:8090/scan
contexts:
- name: trivy-k8s-webhook
  context:
    cluster: trivy-k8s-webhook
    user: api-server
current-context: trivy-k8s-webhook
preferences: {}
users:
- name: api-server
  user:
    client-certificate: /etc/kubernetes/admission-control/api-server-client.crt
    client-key: /etc/kubernetes/admission-control/api-server-client.key
#只在server中增加了相关配置！

kube-apiserver

vim /etc/kubernetes/manifests/kube-apiserver.yaml
- --admission-control-config-file=/etc/kubernetes/admission-control/admission-control.conf
- --enable-admission-plugins=NodeRestriction,ImagePolicyWebhook

验证

systemctl restart kubelet
kubectl apply -f /root/xxx/vulnerable-manifest.yaml
tail -n 10 /var/log/imagepolicy/roadrunner.log

14. api-server 参数调整

这个题没有读懂。没有搞明白只看懂了apiserver中修改了：

- --enable-admission-plugins=AlwaysAdmit
修改为：
- --enable-admission-plugins=NodeRestriction

然后根据题目提示还删除了了一个匿名的clusterrole....接下来就不知道要怎么搞了。正常就是这个题得分应该是没有的

15. AppArmor

注：参照https://kubernetes.io/docs/tutorials/clusters/apparmor/

ssh到work节点

cat /etc/apparmor.d/nginx_apparmor
#include <tunables/global>
profile nginx-profile-3 flags=(attach_disconnected) {
  #include <abstractions/base>
  file,
  # Deny all file writes.
  deny /** w,
}
sudo apparmor_status | grep nginx

sudo -qa /etc/apparmor.d/nginx_apparmor

sudo apparmor_status | grep nginx
   nginx-profile-3

exit work节点回到跳板机：

vim https://github.com/lmtbelmonte/cks-cert
apiVersion: v1
kind: Pod
metadata:
  name: writedeny
  namespace: dev
  annotations:
    container.apparmor.security.beta.kubernetes.io/busybox: localhost/nginx-profile-3
spec:
  containers:
  - name: busybox
    image: busybox:1.33.1

kubecl apply -f ~/nginx-deploy.yml