1 Overview
In the development of today's cloud-native applications, Kubernetes has become the standard. However, with the popularity of its use, it also brings security challenges. This article will introduce how to use the kube-bench tool to evaluate and enhance the security of a Kubernetes cluster.
2 Introduction to CIS (Center for Internet Security)
CIS (Center for Internet Security) is a nonprofit organization dedicated to cybersecurity. It provides a set of baseline security standards for various operating systems and applications that are widely recognized as effective means of preventing cyberattacks.
CIS benchmarks are a series of globally recognized best practice standards developed by the Center for Internet Security (CIS) in the United States to protect systems and data from threats. These benchmarks include configuration guidance for various technology platforms and systems, such as operating systems, network equipment, mobile devices, server applications, and more.
CIS benchmarks provide detailed steps to protect specific systems, with clear instructions and recommendations for each step. Additionally, it provides automated tools for assessing system compliance with CIS benchmarks. Following CIS benchmarks can help organizations reduce security risks and enhance compliance.
In the Kubernetes environment, the CIS Kubernetes benchmark is a set of security configuration best practices for Kubernetes. For example, the CIS Kubernetes benchmark covers how to configure kubelet, how to restrict permissions on the API server, etc.
CIS official website is:https://www.cisecurity.org/, CIS Kubernetes The method to download the Benchmark file is as follows:
进入CIS（Center for Internet Security）官网。
Find CIS Benchmarks and click DOWNLOAD LATEST.
What we need is the benchmarks of kubernetes. Find Kubernetes and click DOWNLOAD THE BENCHMARK.
Fill in the information and you can download the kubernetes Benchmark PDF file for free.
The file obtained after downloading is: CIS_Kubernetes_Benchmark_v1.6.0.pdf.
Or go directly to https://downloads.cisecurity.org/#/ to download, find kubernetes, and select the appropriate version to download.
3 What is Kube-Bench?
Kube-Bench is an open source Go language tool used to automatically check whether a Kubernetes cluster complies with the CIS Kubernetes benchmark. These benchmarks include a series of recommendations and best practices for Kubernetes configuration and deployment security.
Kube-Bench performs a series of tests against Kubernetes components (such as kube-apiserver, etcd, kube-scheduler, kube-controller-manager, etc.) to check whether they are configured as recommended by the CIS benchmark. Test results will be classified as PASS, FAIL or WARN to clearly show where improvements are needed.
Kube-Bench is a tool for checking the Kubernetes environment at runtime. It does not modify the system. You can run kube-bench regularly to audit your Kubernetes environment to ensure it remains in optimal security condition.
kube-bench在GitHub的网址为：GitHub - aquasecurity/kube-bench: Checks whether Kubernetes is deployed according to security best practices as defined in the CIS Kubernetes Benchmark
You can download the kube-bench tool at Tags · aquasecurity/kube-bench · GitHub .
Select the version and click Downloads.
Download kube-bench_0.6.17_linux_amd64.tar.gz.
4 Use kube-bench to detect unsafe settings
4.1 Manually setting unsafe parameters
It is a bit troublesome to set up kubernetes cluster security according to the CIS_Kubernetes_Benchmark file. We use the tool kube-bench to detect kubernetes cluster security.
Create a backup directory.
$ mkdir /bakBack up the files under /etc/kubernetes/manifests/. You will need to modify the configuration file later. If the modification is wrong, you can restore it.
$ cd /etc/kubernetes/manifests/
$ ls
etcd.yaml kube-apiserver.yaml kube-controller-manager.yaml kube-scheduler.yaml
#cp -a: 递归复制，复制的数据会保留原有数据的时间戳等信息（具体：时间戳+所有权+复制连结文件属性而非档案本身）
#cp -r: 递归复制，复制的数据会使用新的时间戳等信息
$ cp -a * /bak/The file is now backed up.
$ ls /bak/
etcd.yaml kube-apiserver.yaml kube-controller-manager.yaml kube-scheduler.yamlWe change client-cert-auth=true in the etcd.yaml file to client-cert-auth=false.
$ pwd
/etc/kubernetes/manifests
$ ls
etcd.yaml kube-apiserver.yaml kube-controller-manager.yaml kube-scheduler.yaml
$ vim etcd.yaml
#修改--client-cert-auth=false后保存退出
$ grep client-cert-auth etcd.yaml
- --client-cert-auth=false
- --peer-client-cert-auth=trueWe changed the authorization-mode authorization mode to AlwaysAllow.
$ vim kube-apiserver.yaml
修改 --authorization-mode=AlwaysAllow
$ grep authorization-mode kube-apiserver.yaml
# - --authorization-mode=Node,RBAC
- --authorization-mode=AlwaysAllowRestart kubelet for the configuration to take effect.
$ systemctl restart kubelet
$ systemctl status kubelet
● kubelet.service - kubelet: The Kubernetes Node Agent
Loaded: loaded (/lib/systemd/system/kubelet.service; enabled; vendor preset: enabled)
Drop-In: /etc/systemd/system/kubelet.service.d
└─10-kubeadm.conf
Active: active (running) since Sun 2022-04-17 16:14:24 CST; 9s ago
Docs: https://kubernetes.io/docs/home/
Main PID: 49107 (kubelet)
Tasks: 16 (limit: 3295)
CGroup: /system.slice/kubelet.service4.2 Install kube-bench
We have downloaded kube-bench. If you have not downloaded it, you can download it from this website:https://github.com/aquasecurity/kube-bench/tags .
$ ls
kube-bench_0.6.17_linux_amd64.tar.gzAfter decompressing kube-bench_0.6.7_linux_amd64.tar.gz, you get cfg and kube-bench.
$ tar xf kube-bench_0.6.7_linux_amd64.tar.gz
$ ls
cfg kube-bench kube-bench_0.6.7_linux_amd64.tar.gz
Enter the cfg directory. cfg/config.yaml contains which components the master contains, where the configuration files are placed, where to read the configuration files, etc. If some of the k8s configuration files are customized and placed in a certain directory, modify the config. The corresponding directory in yaml will do.
$ ls cfg/
ack-1.0 aks-1.0 cis-1.20 cis-1.5 cis-1.6 config.yaml eks-1.0.1 gke-1.0 gke-1.2.0 rh-0.7 rh-1.0
$ cd cfg/cis-1.6/
#etcd.yaml文件记录了需要检测etcd的信息
$ ls
config.yaml controlplane.yaml etcd.yaml master.yaml node.yaml policies.yaml4.3 kube-bench detects etcd components
The execution method of kube-bench V0.31 version is: ./kube-bench, ./kube-bench master (detect master settings), ./kube-bench node (detect worker settings), but the new version of kube-bench cannot be executed like this .
$ cd
$ ./kube-bench node
Error: unknown command "node" for "./kube-bench"
Run './kube-bench --help' for usage.
unknown command "node" for "./kube-bench"To execute the new version of kube-bench, you need to specify the configuration directory. The detection syntax is: ./kube-bench --config-dir configuration directory --config configuration file run --targets=components that need to be detected.
$ pwd
/root
$ ls
cfg kube-bench kube-bench_0.6.7_linux_amd64.tar.gz
#--targets=检测的组件就是cfg/cis-1.6/目录下的那些组件
$ ls cfg/cis-1.6/
config.yaml controlplane.yaml etcd.yaml master.yaml node.yaml policies.yamlWe now use kube-bench to start detecting the etcd component. We can see that the etcd component has 6 PASS and 1 FAIL.
$ pwd
/root
$ ls
cfg kube-bench kube-bench_0.6.7_linux_amd64.tar.gz
$ ./kube-bench --config-dir `pwd`/cfg --config `pwd`/cfg/config.yaml run --targets=etcd
Warning: Kubernetes version was not auto-detected because kubectl could not connect to the Kubernetes server. This may be because the kubeconfig information is missing or has credentials that do not match the server. Assuming default version 1.18
Warning: Kubernetes version was not auto-detected because kubectl could not connect to the Kubernetes server. This may be because the kubeconfig information is missing or has credentials that do not match the server. Assuming default version 1.18
[INFO] 2 Etcd Node Configuration
[INFO] 2 Etcd Node Configuration Files
[PASS] 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)
[PASS] 2.4 Ensure that the --peer-cert-file and --peer-key-file arguments are set as appropriate (Automated)
[PASS] 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)
[PASS] 2.7 Ensure that a unique Certificate Authority is used for etcd (Manual)
== Remediations etcd ==
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"
== Summary etcd ==
6 checks PASS
1 checks FAIL
0 checks WARN
0 checks INFO
== Summary total ==
6 checks PASS
1 checks FAIL
0 checks WARN
0 checks INFOAccording to the error message of kube-bench: "[FAIL] 2.2 Ensure that the --client-cert-auth argument is set to true (Automated)", indicating that the --client-cert-auth parameter should be set to true.
Remediations etcdTell us the solution and follow the prompts to modify the --client-cert-auth parameter of /etc/kubernetes/manifests/etcd.yaml.
$ vim /etc/kubernetes/manifests/etcd.yaml
# 修改--client-cert-auth=true。
$ grep client-cert-auth /etc/kubernetes/manifests/etcd.yaml
- --client-cert-auth=true
- --peer-client-cert-auth=trueRestart kubelet for the parameters to take effect.
$ systemctl restart kubelet
$ kubectl get node
NAME STATUS ROLES AGE VERSION
ops-master-1 Ready control-plane,master 24h v1.21.9
ops-worker-1 Ready <none> 24h v1.21.9
ops-worker-2 Ready <none> 24h v1.21.9Use kube-bench to re-detect the etcd component. Now all etcd components are in PASS status, and etcd has no security risks.
$ ./kube-bench --config-dir `pwd`/cfg --config `pwd`/cfg/config.yaml run --targets=etcd
[INFO] 2 Etcd Node Configuration
[INFO] 2 Etcd Node Configuration Files
[PASS] 2.1 Ensure that the --cert-file and --key-file arguments are set as appropriate (Automated)
[PASS] 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)
[PASS] 2.4 Ensure that the --peer-cert-file and --peer-key-file arguments are set as appropriate (Automated)
[PASS] 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)
[PASS] 2.7 Ensure that a unique Certificate Authority is used for etcd (Manual)
== Summary etcd ==
7 checks PASS
0 checks FAIL
0 checks WARN
0 checks INFO
== Summary total ==
7 checks PASS
0 checks FAIL
0 checks WARN
0 checks INFO4.4 kube-bench detects master node
Now detect the master node. The master node has many parameters and too much output information. I deleted the PASS information.
You can see that the master node has 39 PASS, 14 FAIL, and 11 WARN.
$ ./kube-bench --config-dir `pwd`/cfg --config `pwd`/cfg/config.yaml run --targets=master
[INFO] 1 Master Node Security Configuration
[INFO] 1.1 Master Node Configuration Files
[PASS] 1.1.1 Ensure that the API server pod specification file permissions are set to 644 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 644 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 644 or more restrictive (Automated)
[PASS] 1.1.6 Ensure that the scheduler pod specification file ownership is set to root:root (Automated)
[PASS] 1.1.7 Ensure that the etcd pod specification file permissions are set to 644 or more restrictive (Automated)
[PASS] 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 644 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)
[PASS] 1.1.13 Ensure that the admin.conf file permissions are set to 644 or more restrictive (Automated)
[PASS] 1.1.14 Ensure that the admin.conf file ownership is set to root:root (Automated)
[PASS] 1.1.15 Ensure that the scheduler.conf file permissions are set to 644 or more restrictive (Automated)
[PASS] 1.1.16 Ensure that the scheduler.conf file ownership is set to root:root (Automated)
[PASS] 1.1.17 Ensure that the controller-manager.conf file permissions are set to 644 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)
[PASS] 1.1.20 Ensure that the Kubernetes PKI certificate file permissions are set to 644 or more restrictive (Manual)
[PASS] 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)
[PASS] 1.2.3 Ensure that the --kubelet-https argument is set to true (Automated)
[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)
[FAIL] 1.2.6 Ensure that the --authorization-mode argument is not set to AlwaysAllow (Automated)
[FAIL] 1.2.7 Ensure that the --authorization-mode argument includes Node (Automated)
[FAIL] 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)
[FAIL] 1.2.15 Ensure that the admission control plugin PodSecurityPolicy is set (Automated)
[PASS] 1.2.16 Ensure that the admission control plugin NodeRestriction is set (Automated)
[PASS] 1.2.17 Ensure that the --insecure-bind-address argument is not set (Automated)
[PASS] 1.2.18 Ensure that the --insecure-port argument is set to 0 (Automated)
[PASS] 1.2.19 Ensure that the --secure-port argument is not set to 0 (Automated)
[FAIL] 1.2.20 Ensure that the --profiling argument is set to false (Automated)
[FAIL] 1.2.21 Ensure that the --audit-log-path argument is set (Automated)
[FAIL] 1.2.22 Ensure that the --audit-log-maxage argument is set to 30 or as appropriate (Automated)
[FAIL] 1.2.23 Ensure that the --audit-log-maxbackup argument is set to 10 or as appropriate (Automated)
[FAIL] 1.2.24 Ensure that the --audit-log-maxsize argument is set to 100 or as appropriate (Automated)
[WARN] 1.2.25 Ensure that the --request-timeout argument is set as appropriate (Manual)
[PASS] 1.2.26 Ensure that the --service-account-lookup argument is set to true (Automated)
[PASS] 1.2.27 Ensure that the --service-account-key-file argument is set as appropriate (Automated)
[PASS] 1.2.28 Ensure that the --etcd-certfile and --etcd-keyfile arguments are set as appropriate (Automated)
[PASS] 1.2.29 Ensure that the --tls-cert-file and --tls-private-key-file arguments are set as appropriate (Automated)
[PASS] 1.2.30 Ensure that the --client-ca-file argument is set as appropriate (Automated)
[PASS] 1.2.31 Ensure that the --etcd-cafile argument is set as appropriate (Automated)
[WARN] 1.2.32 Ensure that the --encryption-provider-config argument is set as appropriate (Manual)
[WARN] 1.2.33 Ensure that encryption providers are appropriately configured (Manual)
[WARN] 1.2.34 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 ==
1.1.9 Run the below command (based on the file location on your system) on the master node.
For example,
chmod 644 <path/to/cni/files>
1.1.10 Run the below command (based on the file location on your system) on the master 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 below 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
1.2.1 Edit the API server pod specification file /etc/kubernetes/manifests/kube-apiserver.yaml
on the master node and set the below parameter.
--anonymous-auth=false
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 master node and set the
--kubelet-certificate-authority parameter to the path to the cert file for the certificate authority.
--kubelet-certificate-authority=<ca-string>
1.2.6 Edit the API server pod specification file /etc/kubernetes/manifests/kube-apiserver.yaml
on the master node and set the --authorization-mode parameter to values other than AlwaysAllow.
One such example could be as below.
--authorization-mode=RBAC
1.2.7 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
1.2.8 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 RBAC,
for example:
--authorization-mode=Node,RBAC
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 master 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 master node and set the --enable-admission-plugins parameter to include
SecurityContextDeny, unless PodSecurityPolicy is already in place.
--enable-admission-plugins=...,SecurityContextDeny,...
1.2.15 Follow the documentation and create Pod Security Policy objects as per your environment.
Then, edit the API server pod specification file /etc/kubernetes/manifests/kube-apiserver.yaml
on the master node and set the --enable-admission-plugins parameter to a
value that includes PodSecurityPolicy:
--enable-admission-plugins=...,PodSecurityPolicy,...
Then restart the API Server.
1.2.20 Edit the API server pod specification file /etc/kubernetes/manifests/kube-apiserver.yaml
on the master node and set the below parameter.
--profiling=false
1.2.21 Edit the API server pod specification file /etc/kubernetes/manifests/kube-apiserver.yaml
on the master 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
1.2.22 Edit the API server pod specification file /etc/kubernetes/manifests/kube-apiserver.yaml
on the master node and set the --audit-log-maxage parameter to 30 or as an appropriate number of days:
--audit-log-maxage=30
1.2.23 Edit the API server pod specification file /etc/kubernetes/manifests/kube-apiserver.yaml
on the master node and set the --audit-log-maxbackup parameter to 10 or to an appropriate
value.
--audit-log-maxbackup=10
1.2.24 Edit the API server pod specification file /etc/kubernetes/manifests/kube-apiserver.yaml
on the master 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
1.2.25 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
1.2.32 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 master node and set the --encryption-provider-config parameter to the path of that file: --encryption-provider-config=</path/to/EncryptionConfig/File>
1.2.33 Follow the Kubernetes documentation and configure a EncryptionConfig file.
In this file, choose aescbc, kms or secretbox as the encryption provider.
1.2.34 Edit the API server pod specification file /etc/kubernetes/manifests/kube-apiserver.yaml
on the master node and set the below parameter.
--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
1.3.1 Edit the Controller Manager pod specification file /etc/kubernetes/manifests/kube-controller-manager.yaml
on the master 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 master 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 master node and set the below parameter.
--profiling=false
== Summary master ==
40 checks PASS
13 checks FAIL
11 checks WARN
0 checks INFO
== Summary total ==
40 checks PASS
13 checks FAIL
11 checks WARN
0 checks INFOCheck the error message of 1.2.6: "1.2.6 Ensure that the --authorization-mode argument is not set to AlwaysAllow (Automated)", which means that -authorization-mode should not be set to AlwaysAllow, but should be set to --authorization-mode =Node,RBAC, modify according to the prompts:
$ vim /etc/kubernetes/manifests/kube-apiserver.yaml
修改参数：--authorization-mode=Node,RBAC
$ grep authorization-mode /etc/kubernetes/manifests/kube-apiserver.yaml
- --authorization-mode=Node,RBACThe error message of 1.2.20 is: "[FAIL] 1.2.20 Ensure that the --profiling argument is set to false (Automated) ", indicating that the --profiling argument should be set to false.
According to the prompt information: "1.2.20 Edit the API server pod specification file /etc/kubernetes/manifests/kube-apiserver.yaml
on the master node and set the below parameter . --profiling=false". Change parameters.
$ vim /etc/kubernetes/manifests/kube-apiserver.yaml
新增参数：--profiling=false
$ grep profiling /etc/kubernetes/manifests/kube-apiserver.yaml
- --profiling=falseRestart kubelet for the configuration to take effect.
$ systemctl restart kubelet
$ kubectl get node
NAME STATUS ROLES AGE VERSION
ops-master-1 Ready control-plane,master 24h v1.21.9
ops-worker-1 Ready <none> 24h v1.21.9
ops-worker-2 Ready <none> 24h v1.21.9Use kube-bench to recheck the master node. Now there are more passes and fewer FAILs.
$ ./kube-bench --config-dir `pwd`/cfg --config `pwd`/cfg/config.yaml run --targets=master
[INFO] 1 Master Node Security Configuration
[INFO] 1.1 Master Node Configuration Files
[PASS] 1.1.1 Ensure that the API server pod specification file permissions are set to 644 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 644 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 644 or more restrictive (Automated)
[PASS] 1.1.6 Ensure that the scheduler pod specification file ownership is set to root:root (Automated)
[PASS] 1.1.7 Ensure that the etcd pod specification file permissions are set to 644 or more restrictive (Automated)
[PASS] 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 644 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)
[PASS] 1.1.13 Ensure that the admin.conf file permissions are set to 644 or more restrictive (Automated)
[PASS] 1.1.14 Ensure that the admin.conf file ownership is set to root:root (Automated)
[PASS] 1.1.15 Ensure that the scheduler.conf file permissions are set to 644 or more restrictive (Automated)
[PASS] 1.1.16 Ensure that the scheduler.conf file ownership is set to root:root (Automated)
[PASS] 1.1.17 Ensure that the controller-manager.conf file permissions are set to 644 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)
[PASS] 1.1.20 Ensure that the Kubernetes PKI certificate file permissions are set to 644 or more restrictive (Manual)
[PASS] 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)
[PASS] 1.2.3 Ensure that the --kubelet-https argument is set to true (Automated)
[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)
[FAIL] 1.2.15 Ensure that the admission control plugin PodSecurityPolicy is set (Automated)
[PASS] 1.2.16 Ensure that the admission control plugin NodeRestriction is set (Automated)
[PASS] 1.2.17 Ensure that the --insecure-bind-address argument is not set (Automated)
[PASS] 1.2.18 Ensure that the --insecure-port argument is set to 0 (Automated)
[PASS] 1.2.19 Ensure that the --secure-port argument is not set to 0 (Automated)
[PASS] 1.2.20 Ensure that the --profiling argument is set to false (Automated)
[FAIL] 1.2.21 Ensure that the --audit-log-path argument is set (Automated)
[FAIL] 1.2.22 Ensure that the --audit-log-maxage argument is set to 30 or as appropriate (Automated)
[FAIL] 1.2.23 Ensure that the --audit-log-maxbackup argument is set to 10 or as appropriate (Automated)
[FAIL] 1.2.24 Ensure that the --audit-log-maxsize argument is set to 100 or as appropriate (Automated)
[WARN] 1.2.25 Ensure that the --request-timeout argument is set as appropriate (Manual)
[PASS] 1.2.26 Ensure that the --service-account-lookup argument is set to true (Automated)
[PASS] 1.2.27 Ensure that the --service-account-key-file argument is set as appropriate (Automated)
[PASS] 1.2.28 Ensure that the --etcd-certfile and --etcd-keyfile arguments are set as appropriate (Automated)
[PASS] 1.2.29 Ensure that the --tls-cert-file and --tls-private-key-file arguments are set as appropriate (Automated)
[PASS] 1.2.30 Ensure that the --client-ca-file argument is set as appropriate (Automated)
[PASS] 1.2.31 Ensure that the --etcd-cafile argument is set as appropriate (Automated)
[WARN] 1.2.32 Ensure that the --encryption-provider-config argument is set as appropriate (Manual)
[WARN] 1.2.33 Ensure that encryption providers are appropriately configured (Manual)
[WARN] 1.2.34 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 ==
1.1.9 Run the below command (based on the file location on your system) on the master node.
For example,
chmod 644 <path/to/cni/files>
1.1.10 Run the below command (based on the file location on your system) on the master 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 below 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
1.2.1 Edit the API server pod specification file /etc/kubernetes/manifests/kube-apiserver.yaml
on the master node and set the below parameter.
--anonymous-auth=false
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 master 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 master 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 master node and set the --enable-admission-plugins parameter to include
SecurityContextDeny, unless PodSecurityPolicy is already in place.
--enable-admission-plugins=...,SecurityContextDeny,...
1.2.15 Follow the documentation and create Pod Security Policy objects as per your environment.
Then, edit the API server pod specification file /etc/kubernetes/manifests/kube-apiserver.yaml
on the master node and set the --enable-admission-plugins parameter to a
value that includes PodSecurityPolicy:
--enable-admission-plugins=...,PodSecurityPolicy,...
Then restart the API Server.
1.2.21 Edit the API server pod specification file /etc/kubernetes/manifests/kube-apiserver.yaml
on the master 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
1.2.22 Edit the API server pod specification file /etc/kubernetes/manifests/kube-apiserver.yaml
on the master node and set the --audit-log-maxage parameter to 30 or as an appropriate number of days:
--audit-log-maxage=30
1.2.23 Edit the API server pod specification file /etc/kubernetes/manifests/kube-apiserver.yaml
on the master node and set the --audit-log-maxbackup parameter to 10 or to an appropriate
value.
--audit-log-maxbackup=10
1.2.24 Edit the API server pod specification file /etc/kubernetes/manifests/kube-apiserver.yaml
on the master 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
1.2.25 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
1.2.32 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 master node and set the --encryption-provider-config parameter to the path of that file: --encryption-provider-config=</path/to/EncryptionConfig/File>
1.2.33 Follow the Kubernetes documentation and configure a EncryptionConfig file.
In this file, choose aescbc, kms or secretbox as the encryption provider.
1.2.34 Edit the API server pod specification file /etc/kubernetes/manifests/kube-apiserver.yaml
on the master node and set the below parameter.
--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
1.3.1 Edit the Controller Manager pod specification file /etc/kubernetes/manifests/kube-controller-manager.yaml
on the master 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 master 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 master node and set the below parameter.
--profiling=false
== Summary master ==
44 checks PASS
9 checks FAIL
11 checks WARN
0 checks INFO
== Summary total ==
44 checks PASS
9 checks FAIL
11 checks WARN
0 checks INFO4.5 kube-bench detects worker nodes
Copy the kube-bench installation package to the worker node of the kubernetes cluster.
$ scp kube-bench_0.6.7_linux_amd64.tar.gz 10.220.43.204:/homeDecompress.
$ tar -xvf kube-bench_0.6.17_linux_amd64.tar.gz
$ ls
cfg kube-benchUse kube-bench to detect the worker nodes of the kubernetes cluster. You can see 19 PASS, 1 FAIL, and 3 WARN.
$ ./kube-bench --config-dir `pwd`/cfg --config `pwd`/cfg/config.yaml run --targets=node
[INFO] 4 Worker Node Security Configuration
[INFO] 4.1 Worker Node Configuration Files
[PASS] 4.1.1 Ensure that the kubelet service file permissions are set to 644 or more restrictive (Automated)
[PASS] 4.1.2 Ensure that the kubelet service file ownership is set to root:root (Automated)
[PASS] 4.1.3 If proxy kubeconfig file exists ensure permissions are set to 644 or more restrictive (Manual)
[PASS] 4.1.4 Ensure that the proxy kubeconfig file ownership is set to root:root (Manual)
[PASS] 4.1.5 Ensure that the --kubeconfig kubelet.conf file permissions are set to 644 or more restrictive (Automated)
[PASS] 4.1.6 Ensure that the --kubeconfig kubelet.conf file ownership is set to root:root (Manual)
[PASS] 4.1.7 Ensure that the certificate authorities file permissions are set to 644 or more restrictive (Manual)
[PASS] 4.1.8 Ensure that the client certificate authorities file ownership is set to root:root (Manual)
[PASS] 4.1.9 Ensure that the kubelet --config configuration file has permissions set to 644 or more restrictive (Automated)
[PASS] 4.1.10 Ensure that the kubelet --config configuration 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 Ensure 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)
[FAIL] 4.2.6 Ensure that the --protect-kernel-defaults argument is set to true (Automated)
[PASS] 4.2.7 Ensure that the --make-iptables-util-chains argument is set to true (Automated)
[PASS] 4.2.8 Ensure that the --hostname-override argument is not set (Manual)
[WARN] 4.2.9 Ensure that the --event-qps argument is set to 0 or a level which ensures appropriate event capture (Manual)
[WARN] 4.2.10 Ensure that the --tls-cert-file and --tls-private-key-file arguments are set as appropriate (Manual)
[PASS] 4.2.11 Ensure that the --rotate-certificates argument is not set to false (Manual)
[PASS] 4.2.12 Verify that the RotateKubeletServerCertificate argument is set to true (Manual)
[WARN] 4.2.13 Ensure that the Kubelet only makes use of Strong Cryptographic Ciphers (Manual)
== Remediations node ==
4.2.6 If using a Kubelet config file, edit the file to set protectKernelDefaults: true.
If using command line arguments, edit the kubelet service file
/lib/systemd/system/kubelet.service on each worker node and
set the below parameter in KUBELET_SYSTEM_PODS_ARGS variable.
--protect-kernel-defaults=true
Based on your system, restart the kubelet service. For example:
systemctl daemon-reload
systemctl restart kubelet.service
4.2.9 If using a Kubelet config file, edit the file to set eventRecordQPS: to an appropriate level.
If using command line arguments, edit the kubelet service file
/lib/systemd/system/kubelet.service on each worker node and
set the below parameter in KUBELET_SYSTEM_PODS_ARGS variable.
Based on your system, restart the kubelet service. For example:
systemctl daemon-reload
systemctl restart kubelet.service
4.2.10 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
/lib/systemd/system/kubelet.service 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
4.2.13 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
/lib/systemd/system/kubelet.service 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
== Summary node ==
19 checks PASS
1 checks FAIL
3 checks WARN
0 checks INFO
== Summary total ==
19 checks PASS
1 checks FAIL
3 checks WARN
0 checks INFOFollow the prompts to repair the security risks of the worker node.
5 Summary
kube-bench is a powerful tool that can help us discover which Kubernetes configurations do not follow CIS best practices, so we can correct these problems and enhance the security of our Kubernetes clusters. While kube-bench cannot capture every possible security issue, it can at least help us eliminate some of the most common security vulnerabilities.
kube-bench is just a checking tool, it cannot automatically fix the problems found. What it provides is information about which configurations may require your attention. Any possible configuration changes require careful decision-making and manual implementation by a knowledgeable administrator.