使用Kube-Bench对Kubernetes进行安全检测

使用Kube-Bench对Kubernetes进行安全检测

1. 工具介绍

Kube-Bench是一个开源的Go语言工具，用于自动化检查Kubernetes集群是否符合CIS Kubernetes基准。这些基准包括一系列关于Kubernetes配置和部署安全性的建议和最佳实践。

Kube-Bench执行了一系列针对Kubernetes组件（如kube-apiserver、etcd、kube-scheduler、kube-controller-manager等）的测试，来检查它们是否按照CIS基准的推荐进行了配置。测试结果会被分类为PASS、FAIL或WARN，以清晰明了地显示哪些地方需要改进。

Kube-Bench是在运行时检查Kubernetes环境的工具，它并不会修改系统。你可以定期运行kube-bench来审计你的Kubernetes环境，确保其保持在最佳的安全状态。

官方仓库：https://github.com/aquasecurity/kube-bench

2. CIS Kubernetes Benchmark支持

在Kubernetes环境中，CIS Kubernetes基准就是一套针对Kubernetes的安全配置最佳实践。例如，CIS Kubernetes基准会涵盖如何配置kubelet，如何限制API服务器上的权限等内容。

进入CIS（Center for Internet Security）官网可以下载Kubernetes Benchmark文件。

Kubernetes Benchmark、kube-bench config和Kubernetes配套关系如下：

最新信息请访问 CIS Kubernetes Benchmark support 查看。

默认配置下，Kube-Bench将根据目标设备上运行的Kubernete版本来确定要运行的测试集。

3. 工具安装

3.1 二进制安装

下载地址：https://github.com/aquasecurity/kube-bench/releases

[root@master1 ~]# wget https://github.com/aquasecurity/kube-bench/releases/download/v0.7.3/kube-bench_0.7.3_linux_amd64.tar.gz
[root@master1 ~]# mkdir /opt/kube-bench
# 将二进制文件解压到创建的目录
[root@master1 ~]# tar xf kube-bench_0.7.3_linux_amd64.tar.gz -C /opt/kube-bench/

# 查看文件内容
[root@master1 ~]# cd /opt/kube-bench/
[root@master1  kube-bench]# ls
cfg  kube-bench
[root@master1  kube-bench]# ls cfg/
ack-1.0   cis-1.24           cis-1.6-k3s  eks-1.0.1                 gke-1.0       k3s-cis-1.7    rke2-cis-1.24  rke-cis-1.7
aks-1.0   cis-1.24-microk8s  cis-1.7      eks-1.1.0                 gke-1.2.0     rh-0.7         rke2-cis-1.7   tkgi-1.2.53
cis-1.20  cis-1.5            cis-1.8      eks-1.2.0                 k3s-cis-1.23  rh-1.0         rke-cis-1.23
cis-1.23  cis-1.6            config.yaml  eks-stig-kubernetes-v1r6  k3s-cis-1.24  rke2-cis-1.23  rke-cis-1.24
[root@master1 cfg]# cd cis-1.8/
# 各个组件yaml文件记录了需要检测的详细信息
[root@master1 cis-1.8]# ls
config.yaml  controlplane.yaml  etcd.yaml  master.yaml  node.yaml  policies.yaml

cfg/config.yaml包含了相关测试组件配置、配置文件路径、K8S版本和CIS标准映射等。如果k8s的某些配置文件自定义到了非默认的目录，修改config.yaml里的相应目录就行。

[root@master1 kube-bench]# cat cfg/config.yaml
---
## Controls Files.
# These are YAML files that hold all the details for running checks.
#
## Uncomment to use different control file paths.
# masterControls: ./cfg/master.yaml
# nodeControls: ./cfg/node.yaml

master:
  components:
    - apiserver
    - scheduler
    - controllermanager
    - etcd
    - flanneld
    # kubernetes is a component to cover the config file /etc/kubernetes/config that is referred to in the benchmark
    - kubernetes
    - kubelet

  kubernetes:
    defaultconf: /etc/kubernetes/config

  apiserver:
    bins:
      - "kube-apiserver"
      - "hyperkube apiserver"
      - "hyperkube kube-apiserver"
      - "apiserver"
      - "openshift start master api"
      - "hypershift openshift-kube-apiserver"
    confs:
      - /etc/kubernetes/manifests/kube-apiserver.yaml
      - /etc/kubernetes/manifests/kube-apiserver.yml
      - /etc/kubernetes/manifests/kube-apiserver.manifest
      - /var/snap/kube-apiserver/current/args
      - /var/snap/microk8s/current/args/kube-apiserver
      - /etc/origin/master/master-config.yaml
      - /etc/kubernetes/manifests/talos-kube-apiserver.yaml
      - /var/lib/rancher/rke2/agent/pod-manifests/kube-apiserver.yaml
    defaultconf: /etc/kubernetes/manifests/kube-apiserver.yaml

  scheduler:
    bins:
      - "kube-scheduler"

...
node:
  components:
    - kubelet
    - proxy
    # kubernetes is a component to cover the config file /etc/kubernetes/config that is referred to in the benchmark
    - kubernetes

  kubernetes:
    defaultconf: "/etc/kubernetes/config"

  kubelet:
    cafile:
      - "/etc/kubernetes/pki/ca.crt"
      - "/etc/kubernetes/certs/ca.crt"
      - "/etc/kubernetes/cert/ca.pem"
      - "/var/snap/microk8s/current/certs/ca.crt"
      - "/var/lib/rancher/rke2/agent/server.crt"
      - "/var/lib/rancher/rke2/agent/client-ca.crt"
      - "/var/lib/rancher/k3s/agent/client-ca.crt"
...

etcd:
  components:
    - etcd

  etcd:
    bins:
      - "etcd"
    datadirs:
      - /var/lib/etcd/default.etcd
      - /var/lib/etcd/data.etcd
    confs:
      - /etc/kubernetes/manifests/etcd.yaml
      - /etc/kubernetes/manifests/etcd.yml
...

controlplane:
  components:
    - apiserver

  apiserver:
    bins:
      - "kube-apiserver"
      - "hyperkube apiserver"
      - "hyperkube kube-apiserver"
      - "apiserver"

policies:
  components: []

managedservices:
  components: []

version_mapping:
  "1.15": "cis-1.5"
  "1.16": "cis-1.6"
...

target_mapping:
  "cis-1.5":
    - "master"
    - "node"
    - "controlplane"
    - "etcd"
    - "policies"
...

3.2 源码安装

工具使用go语言开发，执行如下步骤进行源码安装：

# 安装go
yum install go
# 配置go国内镜像源
go env -w GO111MODULE=on
go env -w GOPROXY=https://goproxy.cn,direct

go install github.com/aquasecurity/kube-bench@latest
#安装成功后位于当前用户的go目录下
/root/go/bin

./kube-bench --help

# Run all checks

./kube-bench

4. 运行kube-bench检测

kube-bench支持etcd组件、master节点、node节点等检测。命令运行语法：

./kube-bench --config-dir <配置目录> --config <配置文件> run --targets=<需要检测的组件>

本文测试的K8S环境如下：

# CPU架构
[root@master1 ~]# lscpu | grep 架构
架构：                           x86_64
  
# K8S集群信息，master节点同时也承担worker节点的角色
[root@master1 ~]# kubectl get nodes
NAME        STATUS   ROLES                  AGE   VERSION
master1   Ready    control-plane,master   44d   v1.27.6
master2   Ready    control-plane,master   44d   v1.27.6
master3   Ready    control-plane,master   44d   v1.27.6
# K8S版本为1.27.6
[root@master1 ~]# kubectl version
WARNING: This version information is deprecated and will be replaced with the output from kubectl version --short.  Use --output=yaml|json to get the full version.
Client Version: version.Info{Major:"1", Minor:"27", GitVersion:"v1.27.6", GitCommit:"741c8db18a52787d734cbe4795f0b4ad860906d6", GitTreeState:"clean", BuildDate:"2023-09-13T09:21:34Z", GoVersion:"go1.20.8", Compiler:"gc", Platform:"linux/amd64"}
Kustomize Version: v5.0.1
Server Version: version.Info{Major:"1", Minor:"27", GitVersion:"v1.27.6", GitCommit:"741c8db18a52787d734cbe4795f0b4ad860906d6", GitTreeState:"clean", BuildDate:"2023-09-13T09:14:09Z", GoVersion:"go1.20.8", Compiler:"gc", Platform:"linux/amd64"}

# 操作系统为openEuler
[root@master1 ~]# cat /etc/openEuler-latest
openeulerversion=openEuler-22.03-LTS
compiletime=2022-03-30-16-23-56
gccversion=10.3.1-10.oe2203
kernelversion=5.10.0-60.18.0.50.oe2203
openjdkversion=1.8.0.312.b07-11.oe2203

4.1 kube-bench检测etcd组件

[root@master1 kube-bench]# ./kube-bench --config-dir ./cfg/ --config ./cfg/config.yaml run --targets=etcd
[INFO] 2 Etcd Node Configuration
[INFO] 2 Etcd Node Configuration
[FAIL] 2.1 Ensure that the --cert-file and --key-file arguments are set as appropriate (Automated)
[FAIL] 2.2 Ensure that the --client-cert-auth argument is set to true (Automated)
[PASS] 2.3 Ensure that the --auto-tls argument is not set to true (Automated)
[FAIL] 2.4 Ensure that the --peer-cert-file and --peer-key-file arguments are set as appropriate (Automated)
[FAIL] 2.5 Ensure that the --peer-client-cert-auth argument is set to true (Automated)
[PASS] 2.6 Ensure that the --peer-auto-tls argument is not set to true (Automated)
[WARN] 2.7 Ensure that a unique Certificate Authority is used for etcd (Manual)

== Remediations etcd ==
2.1 Follow the etcd service documentation and configure TLS encryption.
Then, edit the etcd pod specification file /etc/kubernetes/manifests/etcd.yaml
on the master node and set the below parameters.
--cert-file=</path/to/ca-file>
--key-file=</path/to/key-file>

2.2 Edit the etcd pod specification file /etc/kubernetes/manifests/etcd.yaml on the master
node and set the below parameter.
--client-cert-auth="true"

2.4 Follow the etcd service documentation and configure peer TLS encryption as appropriate
for your etcd cluster.
Then, edit the etcd pod specification file /etc/kubernetes/manifests/etcd.yaml on the
master node and set the below parameters.
--peer-client-file=</path/to/peer-cert-file>
--peer-key-file=</path/to/peer-key-file>

2.5 Edit the etcd pod specification file /etc/kubernetes/manifests/etcd.yaml on the master
node and set the below parameter.
--peer-client-cert-auth=true

2.7 [Manual test]
Follow the etcd documentation and create a dedicated certificate authority setup for the
etcd service.
Then, edit the etcd pod specification file /etc/kubernetes/manifests/etcd.yaml on the
master node and set the below parameter.
--trusted-ca-file=</path/to/ca-file>


== Summary etcd ==
2 checks PASS
4 checks FAIL
1 checks WARN
0 checks INFO

== Summary total ==
2 checks PASS
4 checks FAIL
1 checks WARN
0 checks INFO

根据汇总结果，检测出4个Fail，1个Warn，打印结果给出了相应的详细问题说明和解决方法。

4.2 kube-bench检测master节点

[root@master1 kube-bench]# ./kube-bench --config-dir ./cfg/ --config ./cfg/config.yaml run --targets=master
[INFO] 1 Control Plane Security Configuration
[INFO] 1.1 Control Plane Node Configuration Files
[PASS] 1.1.1 Ensure that the API server pod specification file permissions are set to 600 or more restrictive (Automated)
[PASS] 1.1.2 Ensure that the API server pod specification file ownership is set to root:root (Automated)
[PASS] 1.1.3 Ensure that the controller manager pod specification file permissions are set to 600 or more restrictive (Automated)
[PASS] 1.1.4 Ensure that the controller manager pod specification file ownership is set to root:root (Automated)
[PASS] 1.1.5 Ensure that the scheduler pod specification file permissions are set to 600 or more restrictive (Automated)
[PASS] 1.1.6 Ensure that the scheduler pod specification file ownership is set to root:root (Automated)
[FAIL] 1.1.7 Ensure that the etcd pod specification file permissions are set to 600 or more restrictive (Automated)
[FAIL] 1.1.8 Ensure that the etcd pod specification file ownership is set to root:root (Automated)
[WARN] 1.1.9 Ensure that the Container Network Interface file permissions are set to 600 or more restrictive (Manual)
[WARN] 1.1.10 Ensure that the Container Network Interface file ownership is set to root:root (Manual)
[PASS] 1.1.11 Ensure that the etcd data directory permissions are set to 700 or more restrictive (Automated)
[FAIL] 1.1.12 Ensure that the etcd data directory ownership is set to etcd:etcd (Automated)
[FAIL] 1.1.13 Ensure that the admin.conf file permissions are set to 600 or more restrictive (Automated)
[PASS] 1.1.14 Ensure that the admin.conf file ownership is set to root:root (Automated)
[FAIL] 1.1.15 Ensure that the scheduler.conf file permissions are set to 600 or more restrictive (Automated)
[PASS] 1.1.16 Ensure that the scheduler.conf file ownership is set to root:root (Automated)
[FAIL] 1.1.17 Ensure that the controller-manager.conf file permissions are set to 600 or more restrictive (Automated)
[PASS] 1.1.18 Ensure that the controller-manager.conf file ownership is set to root:root (Automated)
[PASS] 1.1.19 Ensure that the Kubernetes PKI directory and file ownership is set to root:root (Automated)
[WARN] 1.1.20 Ensure that the Kubernetes PKI certificate file permissions are set to 600 or more restrictive (Manual)
[WARN] 1.1.21 Ensure that the Kubernetes PKI key file permissions are set to 600 (Manual)
[INFO] 1.2 API Server
[WARN] 1.2.1 Ensure that the --anonymous-auth argument is set to false (Manual)
[PASS] 1.2.2 Ensure that the --token-auth-file parameter is not set (Automated)
[WARN] 1.2.3 Ensure that the --DenyServiceExternalIPs is set (Manual)
[PASS] 1.2.4 Ensure that the --kubelet-client-certificate and --kubelet-client-key arguments are set as appropriate (Automated)
[FAIL] 1.2.5 Ensure that the --kubelet-certificate-authority argument is set as appropriate (Automated)
[PASS] 1.2.6 Ensure that the --authorization-mode argument is not set to AlwaysAllow (Automated)
[PASS] 1.2.7 Ensure that the --authorization-mode argument includes Node (Automated)
[PASS] 1.2.8 Ensure that the --authorization-mode argument includes RBAC (Automated)
[WARN] 1.2.9 Ensure that the admission control plugin EventRateLimit is set (Manual)
[PASS] 1.2.10 Ensure that the admission control plugin AlwaysAdmit is not set (Automated)
[WARN] 1.2.11 Ensure that the admission control plugin AlwaysPullImages is set (Manual)
[WARN] 1.2.12 Ensure that the admission control plugin SecurityContextDeny is set if PodSecurityPolicy is not used (Manual)
[PASS] 1.2.13 Ensure that the admission control plugin ServiceAccount is set (Automated)
[PASS] 1.2.14 Ensure that the admission control plugin NamespaceLifecycle is set (Automated)
[PASS] 1.2.15 Ensure that the admission control plugin NodeRestriction is set (Automated)
[FAIL] 1.2.16 Ensure that the --profiling argument is set to false (Automated)
[FAIL] 1.2.17 Ensure that the --audit-log-path argument is set (Automated)
[FAIL] 1.2.18 Ensure that the --audit-log-maxage argument is set to 30 or as appropriate (Automated)
[FAIL] 1.2.19 Ensure that the --audit-log-maxbackup argument is set to 10 or as appropriate (Automated)
[FAIL] 1.2.20 Ensure that the --audit-log-maxsize argument is set to 100 or as appropriate (Automated)
[WARN] 1.2.21 Ensure that the --request-timeout argument is set as appropriate (Manual)
[PASS] 1.2.22 Ensure that the --service-account-lookup argument is set to true (Automated)
[PASS] 1.2.23 Ensure that the --service-account-key-file argument is set as appropriate (Automated)
[PASS] 1.2.24 Ensure that the --etcd-certfile and --etcd-keyfile arguments are set as appropriate (Automated)
[PASS] 1.2.25 Ensure that the --tls-cert-file and --tls-private-key-file arguments are set as appropriate (Automated)
[PASS] 1.2.26 Ensure that the --client-ca-file argument is set as appropriate (Automated)
[PASS] 1.2.27 Ensure that the --etcd-cafile argument is set as appropriate (Automated)
[WARN] 1.2.28 Ensure that the --encryption-provider-config argument is set as appropriate (Manual)
[WARN] 1.2.29 Ensure that encryption providers are appropriately configured (Manual)
[PASS] 1.2.30 Ensure that the API Server only makes use of Strong Cryptographic Ciphers (Manual)
[INFO] 1.3 Controller Manager
[WARN] 1.3.1 Ensure that the --terminated-pod-gc-threshold argument is set as appropriate (Manual)
[FAIL] 1.3.2 Ensure that the --profiling argument is set to false (Automated)
[PASS] 1.3.3 Ensure that the --use-service-account-credentials argument is set to true (Automated)
[PASS] 1.3.4 Ensure that the --service-account-private-key-file argument is set as appropriate (Automated)
[PASS] 1.3.5 Ensure that the --root-ca-file argument is set as appropriate (Automated)
[PASS] 1.3.6 Ensure that the RotateKubeletServerCertificate argument is set to true (Automated)
[PASS] 1.3.7 Ensure that the --bind-address argument is set to 127.0.0.1 (Automated)
[INFO] 1.4 Scheduler
[FAIL] 1.4.1 Ensure that the --profiling argument is set to false (Automated)
[PASS] 1.4.2 Ensure that the --bind-address argument is set to 127.0.0.1 (Automated)

== Remediations master ==
1.1.7 Run the below command (based on the file location on your system) on the control plane node.
For example,
chmod 600 /etc/kubernetes/manifests/etcd.yaml

1.1.8 Run the below command (based on the file location on your system) on the control plane node.
For example,
chown root:root /etc/kubernetes/manifests/etcd.yaml

1.1.9 Run the below command (based on the file location on your system) on the control plane node.
For example, chmod 600 <path/to/cni/files>

1.1.10 Run the below command (based on the file location on your system) on the control plane node.
For example,
chown root:root <path/to/cni/files>

1.1.12 On the etcd server node, get the etcd data directory, passed as an argument --data-dir,
from the command 'ps -ef | grep etcd'.
Run the below command (based on the etcd data directory found above).
For example, chown etcd:etcd /var/lib/etcd

1.1.13 Run the below command (based on the file location on your system) on the control plane node.
For example, chmod 600 /etc/kubernetes/admin.conf

1.1.15 Run the below command (based on the file location on your system) on the control plane node.
For example,
chmod 600 /etc/kubernetes/scheduler.conf

1.1.17 Run the below command (based on the file location on your system) on the control plane node.
For example,
chmod 600 /etc/kubernetes/controller-manager.conf

1.1.20 Run the below command (based on the file location on your system) on the control plane node.
For example,
chmod -R 600 /etc/kubernetes/pki/*.crt

1.1.21 Run the below command (based on the file location on your system) on the control plane node.
For example,
chmod -R 600 /etc/kubernetes/pki/*.key

1.2.1 Edit the API server pod specification file /etc/kubernetes/manifests/kube-apiserver.yaml
on the control plane node and set the below parameter.
--anonymous-auth=false

1.2.3 Edit the API server pod specification file /etc/kubernetes/manifests/kube-apiserver.yaml
on the control plane node and remove the `DenyServiceExternalIPs`
from enabled admission plugins.

1.2.5 Follow the Kubernetes documentation and setup the TLS connection between
the apiserver and kubelets. Then, edit the API server pod specification file
/etc/kubernetes/manifests/kube-apiserver.yaml on the control plane node and set the
--kubelet-certificate-authority parameter to the path to the cert file for the certificate authority.
--kubelet-certificate-authority=<ca-string>

1.2.9 Follow the Kubernetes documentation and set the desired limits in a configuration file.
Then, edit the API server pod specification file /etc/kubernetes/manifests/kube-apiserver.yaml
and set the below parameters.
--enable-admission-plugins=...,EventRateLimit,...
--admission-control-config-file=<path/to/configuration/file>

1.2.11 Edit the API server pod specification file /etc/kubernetes/manifests/kube-apiserver.yaml
on the control plane node and set the --enable-admission-plugins parameter to include
AlwaysPullImages.
--enable-admission-plugins=...,AlwaysPullImages,...

1.2.12 Edit the API server pod specification file /etc/kubernetes/manifests/kube-apiserver.yaml
on the control plane node and set the --enable-admission-plugins parameter to include
SecurityContextDeny, unless PodSecurityPolicy is already in place.
--enable-admission-plugins=...,SecurityContextDeny,...

1.2.16 Edit the API server pod specification file /etc/kubernetes/manifests/kube-apiserver.yaml
on the control plane node and set the below parameter.
--profiling=false

1.2.17 Edit the API server pod specification file /etc/kubernetes/manifests/kube-apiserver.yaml
on the control plane node and set the --audit-log-path parameter to a suitable path and
file where you would like audit logs to be written, for example,
--audit-log-path=/var/log/apiserver/audit.log

1.2.18 Edit the API server pod specification file /etc/kubernetes/manifests/kube-apiserver.yaml
on the control plane node and set the --audit-log-maxage parameter to 30
or as an appropriate number of days, for example,
--audit-log-maxage=30

1.2.19 Edit the API server pod specification file /etc/kubernetes/manifests/kube-apiserver.yaml
on the control plane node and set the --audit-log-maxbackup parameter to 10 or to an appropriate
value. For example,
--audit-log-maxbackup=10

1.2.20 Edit the API server pod specification file /etc/kubernetes/manifests/kube-apiserver.yaml
on the control plane node and set the --audit-log-maxsize parameter to an appropriate size in MB.
For example, to set it as 100 MB, --audit-log-maxsize=100

1.2.21 Edit the API server pod specification file /etc/kubernetes/manifests/kube-apiserver.yaml
and set the below parameter as appropriate and if needed.
For example, --request-timeout=300s

1.2.28 Follow the Kubernetes documentation and configure a EncryptionConfig file.
Then, edit the API server pod specification file /etc/kubernetes/manifests/kube-apiserver.yaml
on the control plane node and set the --encryption-provider-config parameter to the path of that file.
For example, --encryption-provider-config=</path/to/EncryptionConfig/File>

1.2.29 Follow the Kubernetes documentation and configure a EncryptionConfig file.
In this file, choose aescbc, kms or secretbox as the encryption provider.

1.3.1 Edit the Controller Manager pod specification file /etc/kubernetes/manifests/kube-controller-manager.yaml
on the control plane node and set the --terminated-pod-gc-threshold to an appropriate threshold,
for example, --terminated-pod-gc-threshold=10

1.3.2 Edit the Controller Manager pod specification file /etc/kubernetes/manifests/kube-controller-manager.yaml
on the control plane node and set the below parameter.
--profiling=false

1.4.1 Edit the Scheduler pod specification file /etc/kubernetes/manifests/kube-scheduler.yaml file
on the control plane node and set the below parameter.
--profiling=false


== Summary master ==
33 checks PASS
14 checks FAIL
13 checks WARN
0 checks INFO

== Summary total ==
33 checks PASS
14 checks FAIL
13 checks WARN
0 checks INFO

检测到14个Fail，可以根据给出的修补方案进行修改。

4.3 kube-bench检测worker节点

[root@master1 kube-bench]# ./kube-bench --config-dir ./cfg/ --config ./cfg/config.yaml run --targets=node
[INFO] 4 Worker Node Security Configuration
[INFO] 4.1 Worker Node Configuration Files
[FAIL] 4.1.1 Ensure that the kubelet service file permissions are set to 600 or more restrictive (Automated)
[PASS] 4.1.2 Ensure that the kubelet service file ownership is set to root:root (Automated)
[WARN] 4.1.3 If proxy kubeconfig file exists ensure permissions are set to 600 or more restrictive (Manual)
[WARN] 4.1.4 If proxy kubeconfig file exists ensure ownership is set to root:root (Manual)
[PASS] 4.1.5 Ensure that the --kubeconfig kubelet.conf file permissions are set to 600 or more restrictive (Automated)
[PASS] 4.1.6 Ensure that the --kubeconfig kubelet.conf file ownership is set to root:root (Automated)
[WARN] 4.1.7 Ensure that the certificate authorities file permissions are set to 600 or more restrictive (Manual)
[PASS] 4.1.8 Ensure that the client certificate authorities file ownership is set to root:root (Manual)
[FAIL] 4.1.9 If the kubelet config.yaml configuration file is being used validate permissions set to 600 or more restrictive (Automated)
[PASS] 4.1.10 If the kubelet config.yaml configuration file is being used validate file ownership is set to root:root (Automated)
[INFO] 4.2 Kubelet
[PASS] 4.2.1 Ensure that the --anonymous-auth argument is set to false (Automated)
[PASS] 4.2.2 Ensure that the --authorization-mode argument is not set to AlwaysAllow (Automated)
[PASS] 4.2.3 Ensure that the --client-ca-file argument is set as appropriate (Automated)
[PASS] 4.2.4 Verify that the --read-only-port argument is set to 0 (Manual)
[PASS] 4.2.5 Ensure that the --streaming-connection-idle-timeout argument is not set to 0 (Manual)
[PASS] 4.2.6 Ensure that the --make-iptables-util-chains argument is set to true (Automated)
[PASS] 4.2.7 Ensure that the --hostname-override argument is not set (Manual)
[PASS] 4.2.8 Ensure that the eventRecordQPS argument is set to a level which ensures appropriate event capture (Manual)
[WARN] 4.2.9 Ensure that the --tls-cert-file and --tls-private-key-file arguments are set as appropriate (Manual)
[PASS] 4.2.10 Ensure that the --rotate-certificates argument is not set to false (Automated)
[PASS] 4.2.11 Verify that the RotateKubeletServerCertificate argument is set to true (Manual)
[WARN] 4.2.12 Ensure that the Kubelet only makes use of Strong Cryptographic Ciphers (Manual)
[WARN] 4.2.13 Ensure that a limit is set on pod PIDs (Manual)

== Remediations node ==
4.1.1 Run the below command (based on the file location on your system) on the each worker node.
For example, chmod 600 /etc/systemd/system/kubelet.service.d/10-kubeadm.conf

4.1.3 Run the below command (based on the file location on your system) on the each worker node.
For example,
chmod 600 /etc/kubernetes/proxy.conf

4.1.4 Run the below command (based on the file location on your system) on the each worker node.
For example, chown root:root /etc/kubernetes/proxy.conf

4.1.7 Run the following command to modify the file permissions of the
--client-ca-file chmod 600 <filename>

4.1.9 Run the following command (using the config file location identified in the Audit step)
chmod 600 /var/lib/kubelet/config.yaml

4.2.9 If using a Kubelet config file, edit the file to set `tlsCertFile` to the location
of the certificate file to use to identify this Kubelet, and `tlsPrivateKeyFile`
to the location of the corresponding private key file.
If using command line arguments, edit the kubelet service file
/etc/systemd/system/kubelet.service.d/10-kubeadm.conf on each worker node and
set the below parameters in KUBELET_CERTIFICATE_ARGS variable.
--tls-cert-file=<path/to/tls-certificate-file>
--tls-private-key-file=<path/to/tls-key-file>
Based on your system, restart the kubelet service. For example,
systemctl daemon-reload
systemctl restart kubelet.service

4.2.12 If using a Kubelet config file, edit the file to set `TLSCipherSuites` to
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
or to a subset of these values.
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 --tls-cipher-suites parameter as follows, or to a subset of these values.
--tls-cipher-suites=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
Based on your system, restart the kubelet service. For example:
systemctl daemon-reload
systemctl restart kubelet.service

4.2.13 Decide on an appropriate level for this parameter and set it,
either via the --pod-max-pids command line parameter or the PodPidsLimit configuration file setting.


== Summary node ==
15 checks PASS
2 checks FAIL
6 checks WARN
0 checks INFO

== Summary total ==
15 checks PASS
2 checks FAIL
6 checks WARN
0 checks INFO

检测到2个Fail，可以根据给出的修补方案进行修改。

4.4 执行全部检测

# 不加targets执行全部检测
[root@master1 kube-bench]# ./kube-bench --config-dir ./cfg/ --config ./cfg/config.yaml run

4.5 手动设置不安全的参数进行检测

可以手动构造不安全的设置，使用工具进行检测：

1. 构造etcd不安全设置，将/etc/kubernetes/manifests/etcd.yaml文件里的client-cert-auth=true改为client-cert-auth=false。

2. 构造kube-apiserver不安全设置，将/etc/kubernetes/manifests/kube-apiserver.yaml文件里的authorization-mode授权模式改为AlwaysAllow。

修改后重启kubelet使配置生效，然后使用kube-bench检测是否能检测到，详细操作查看文末的参考资料。

5. 总结

kube-bench是一款强大的工具，它可以帮助我们发现哪些Kubernetes配置没有遵循CIS的最佳实践，从而改正这些问题，增强我们的Kubernetes集群的安全性。虽然kube-bench不能捕获所有可能的安全问题，但它至少可以帮助我们消除最常见的一些安全漏洞。

6. 问题记录

1. Centos7.9 K8S 环境下面运行kube-bench遇到glibc配套问题，需要更新系统的glibc版本到2.32，由于更新glibc可能造成系统不稳定，改换了系统进行测试。

[root@k8s-master kube-bench]# ./kube-bench --config-dir `pwd`/cfg --config `pwd`/cfg/config.yaml run --targets=etcd
./kube-bench: /lib64/libc.so.6: version `GLIBC_2.32' not found (required by ./kube-bench)
./kube-bench: /lib64/libc.so.6: version `GLIBC_2.34' not found (required by ./kube-bench)

7. 参考资料

https://www.cnblogs.com/renshengdezheli/p/17640119.html