kube-bench/README.md

kube-bench is a Go application that checks whether Kubernetes is deployed securely by running the checks documented in the CIS Kubernetes Benchmark.

Tests are configured with YAML files, making this tool easy to update as test specifications evolve.

Please Note

1. kube-bench implements the CIS Kubernetes Benchmark as closely as possible. Please raise issues here if kube-bench is not correctly implementing the test as described in the Benchmark. To report issues in the Benchmark itself (for example, tests that you believe are inappropriate), please join the CIS community.

2. There is not a one-to-one mapping between releases of Kubernetes and releases of the CIS benchmark. See CIS Kubernetes Benchmark support to see which releases of Kubernetes are covered by different releases of the benchmark.

3. It is impossible to inspect the master nodes of managed clusters, e.g. GKE, EKS, AKS and ACK, using kube-bench as one does not have access to such nodes, although it is still possible to use kube-bench to check worker node configuration in these environments.

Table of Contents

• CIS Kubernetes Benchmark support
• Installation
• Running kube-bench
  • Specifying the benchmark or Kubernetes version
  • Specifying Benchmark sections
  • Running inside a container
  • Running in a Kubernetes cluster
  • Running in an AKS cluster
  • Running in an EKS cluster
  • Running on OpenShift
  • Running in an GKE cluster
  • Running in an ACK cluster
  • Installing from a container
  • Download and Install binaries
  • Installing from sources
• Output
• Configuration
• Troubleshooting
• Test config YAML representation
  • Omitting checks
• Roadmap
• Testing locally with kind
• Contributing
  • Bugs
  • Features
  • Pull Requests

CIS Kubernetes Benchmark support

kube-bench supports the tests for Kubernetes as defined in the CIS Kubernetes Benchmarks.

CIS Kubernetes Benchmark	kube-bench config	Kubernetes versions
1.5.1	cis-1.5	1.15-
1.6.0	cis-1.6	1.16-
GKE 1.0.0	gke-1.0	GKE
EKS 1.0.0	eks-1.0	EKS
ACK 1.0.0	ack-1.0	ACK
Red Hat OpenShift hardening guide	rh-0.7	OCP 3.10-3.11

By default, kube-bench will determine the test set to run based on the Kubernetes version running on the machine, but please note that kube-bench does not automatically detect OpenShift and GKE - see the section below on Running kube-bench.

The test files for the various versions of CIS Benchmark can be found in directories with same name as the CIS Benchmark versions under cfg/, for example cfg/cis-1.5.

Installation

You can choose to

• Run kube-bench from inside a container (sharing PID namespace with the host). See Running inside a container for additional details.
• Run a container that installs kube-bench on the host, and then run kube-bench directly on the host. See Installing from a container for additional details.
• install the latest binaries from the Releases page, though please note that you also need to download the config and test files from the cfg directory. See Download and Install binaries for details.
• Compile it from source. See Installing from sources for details.

Running kube-bench

If you run kube-bench directly from the command line you may need to be root / sudo to have access to all the config files.

By default kube-bench attempts to auto-detect the running version of Kubernetes, and map this to the corresponding CIS Benchmark version. For example, Kubernetes version 1.15 is mapped to CIS Benchmark version cis-1.15 which is the benchmark version valid for Kubernetes 1.15.

kube-bench also attempts to identify the components running on the node, and uses this to determine which tests to run (for example, only running the master node tests if the node is running an API server).

Specifying the benchmark or Kubernetes version

kube-bench uses the Kubernetes API, or access to the kubectl or kubelet executables to try to determine the Kubernetes version, and hence which benchmark to run. If you wish to override this, or if none of these methods are available, you can specify either the Kubernetes version or CIS Benchmark as a command line parameter.

You can specify a particular version of Kubernetes by setting the --version flag or with the KUBE_BENCH_VERSION environment variable. The value of --version takes precedence over the value of KUBE_BENCH_VERSION.

For example, run kube-bench using the tests for Kubernetes version 1.13:

kube-bench --version 1.13

You can specify --benchmark to run a specific CIS Benchmark version:

kube-bench --benchmark cis-1.5

Note: It is an error to specify both --version and --benchmark flags together

Specifying Benchmark sections

If you want to run specific CIS Benchmark sections (i.e master, node, etcd, etc...) you can use the run --targets subcommand.

kube-bench run --targets master,node

or

kube-bench run --targets master,node,etcd,policies

Check the contents of the benchmark directory under cfg to see which targets are available for that benchmark. Each file except config.yaml represents a target (also known as a control in other parts of this documentation).

The following table shows the valid targets based on the CIS Benchmark version.

CIS Benchmark	Targets
cis-1.5	master, controlplane, node, etcd, policies
cis-1.6	master, controlplane, node, etcd, policies
gke-1.0	master, controlplane, node, etcd, policies, managedservices
eks-1.0	controlplane, node, policies, managedservices
ack-1.0	master, controlplane, node, etcd, policies, managedservices

If no targets are specified, kube-bench will determine the appropriate targets based on the CIS Benchmark version and the components detected on the node. The detection is done by verifying which components are running, as defined in the config files (see Configuration.

Running inside a container

You can avoid installing kube-bench on the host by running it inside a container using the host PID namespace and mounting the /etc and /var directories where the configuration and other files are located on the host so that kube-bench can check their existence and permissions.

docker run --pid=host -v /etc:/etc:ro -v /var:/var:ro -t aquasec/kube-bench:latest --version 1.13

Note: the tests require either the kubelet or kubectl binary in the path in order to auto-detect the Kubernetes version. You can pass -v $(which kubectl):/usr/local/mount-from-host/bin/kubectl to resolve this. You will also need to pass in kubeconfig credentials. For example:

docker run --pid=host -v /etc:/etc:ro -v /var:/var:ro -v $(which kubectl):/usr/local/mount-from-host/bin/kubectl -v ~/.kube:/.kube -e KUBECONFIG=/.kube/config -t aquasec/kube-bench:latest 

You can use your own configs by mounting them over the default ones in /opt/kube-bench/cfg/

docker run --pid=host -v /etc:/etc:ro -v /var:/var:ro -t -v path/to/my-config.yaml:/opt/kube-bench/cfg/config.yam -v $(which kubectl):/usr/local/mount-from-host/bin/kubectl -v ~/.kube:/.kube -e KUBECONFIG=/.kube/config aquasec/kube-bench:latest

Running in a Kubernetes cluster

You can run kube-bench inside a pod, but it will need access to the host's PID namespace in order to check the running processes, as well as access to some directories on the host where config files and other files are stored.

The supplied job.yaml file can be applied to run the tests as a job. For example:

$ kubectl apply -f job.yaml
job.batch/kube-bench created

$ kubectl get pods
NAME                      READY   STATUS              RESTARTS   AGE
kube-bench-j76s9   0/1     ContainerCreating   0          3s

# Wait for a few seconds for the job to complete
$ kubectl get pods
NAME                      READY   STATUS      RESTARTS   AGE
kube-bench-j76s9   0/1     Completed   0          11s

# The results are held in the pod's logs
kubectl logs kube-bench-j76s9
[INFO] 1 Master Node Security Configuration
[INFO] 1.1 API Server
...

To run tests on the master node, the pod needs to be scheduled on that node. This involves setting a nodeSelector and tolerations in the pod spec.

The default labels applied to master nodes has changed since Kubernetes 1.11, so if you are using an older version you may need to modify the nodeSelector and tolerations to run the job on the master node.

Running in an AKS cluster

1. Create an AKS cluster(e.g. 1.13.7) with RBAC enabled, otherwise there would be 4 failures

2. Use the kubectl-enter plugin to shell into a node kubectl-enter {node-name} or ssh to one agent node could open nsg 22 port and assign a public ip for one agent node (only for testing purpose)

3. Run CIS benchmark to view results:

docker run --rm -v `pwd`:/host aquasec/kube-bench:latest install
./kube-bench 

kube-bench cannot be run on AKS master nodes

Running in an EKS cluster

There is a job-eks.yaml file for running the kube-bench node checks on an EKS cluster. The significant difference on EKS is that it's not possible to schedule jobs onto the master node, so master checks can't be performed

1. To create an EKS Cluster refer to Getting Started with Amazon EKS in the Amazon EKS User Guide

• Information on configuring eksctl, kubectl and the AWS CLI is within

2. Create an Amazon Elastic Container Registry (ECR) repository to host the kube-bench container image

aws ecr create-repository --repository-name k8s/kube-bench --image-tag-mutability MUTABLE

3. Download, build and push the kube-bench container image to your ECR repo

git clone https://github.com/aquasecurity/kube-bench.git
cd kube-bench
aws ecr get-login-password --region <AWS_REGION> | docker login --username AWS --password-stdin <AWS_ACCT_NUMBER>.dkr.ecr.<AWS_REGION>.amazonaws.com
docker build -t k8s/kube-bench .
docker tag k8s/kube-bench:latest <AWS_ACCT_NUMBER>.dkr.ecr.<AWS_REGION>.amazonaws.com/k8s/kube-bench:latest
docker push <AWS_ACCT_NUMBER>.dkr.ecr.<AWS_REGION>.amazonaws.com/k8s/kube-bench:latest

4. Copy the URI of your pushed image, the URI format is like this: <AWS_ACCT_NUMBER>.dkr.ecr.<AWS_REGION>.amazonaws.com/k8s/kube-bench:latest
5. Replace the image value in job-eks.yaml with the URI from Step 4
6. Run the kube-bench job on a Pod in your Cluster: kubectl apply -f job-eks.yaml
7. Find the Pod that was created, it should be in the default namespace: kubectl get pods --all-namespaces
8. Retrieve the value of this Pod and output the report, note the Pod name will vary: kubectl logs kube-bench-<value>

• You can save the report for later reference: kubectl logs kube-bench-<value> > kube-bench-report.txt

Report kube-bench findings to AWS Security Hub

You can configure kube-bench with the --asff option to send findings to AWS Security Hub for any benchmark tests that fail or that generate a warning. See this page for more information on how to enable the kube-bench integration with AWS Security Hub.

Running on OpenShift

OpenShift Hardening Guide	kube-bench config
ocp-3.10	rh-0.7
ocp-3.11	rh-0.7
ocp-4.*	Not supported

kube-bench includes a set of test files for Red Hat's OpenShift hardening guide for OCP 3.10 and 3.11. To run this you will need to specify --benchmark rh-07, or --version ocp-3.10 or --version ocp-3.11

when you run the kube-bench command (either directly or through YAML).

There is work in progress on a CIS Red Hat OpenShift Container Platform Benchmark which we believe should cover OCP 4.* and we intend to add support in kube-bench when it's published.

Running in a GKE cluster

CIS Benchmark	Targets
gke-1.0	master, controlplane, node, etcd, policies, managedservices

kube-bench includes benchmarks for GKE. To run this you will need to specify --benchmark gke-1.0 when you run the kube-bench command.

To run the benchmark as a job in your GKE cluster apply the included job-gke.yaml.

kubectl apply -f job-gke.yaml

Running in a ACK cluster

CIS Benchmark	Targets
ack-1.0	master, controlplane, node, etcd, policies, managedservices

kube-bench includes benchmarks for Alibaba Cloud Container Service For Kubernetes (ACK). To run this you will need to specify --benchmark ack-1.0 when you run the kube-bench command.

To run the benchmark as a job in your ACK cluster apply the included job-ack.yaml.

kubectl apply -f job-ack.yaml

Installing from a container

This command copies the kube-bench binary and configuration files to your host from the Docker container: binaries compiled for linux-x86-64 only (so they won't run on macOS or Windows)

docker run --rm -v `pwd`:/host aquasec/kube-bench:latest install

You can then run ./kube-bench.

Download and Install binaries

It is possible to manually install and run kube-bench release binaries. In order to do that, you must have access to your Kubernetes cluster nodes. Note that if you're using one of the managed Kubernetes services (e.g. EKS, AKS, GKE, ACK), you will not have access to the master nodes of your cluster and you can’t perform any tests on the master nodes.

First, log into one of the nodes using SSH.

Install kube-bench binary for your platform using the commands below. Note that there may be newer releases available. See releases page.

Ubuntu/Debian:

curl -L https://github.com/aquasecurity/kube-bench/releases/download/v0.3.1/kube-bench_0.3.1_linux_amd64.deb -o kube-bench_0.3.1_linux_amd64.deb

sudo apt install ./kube-bench_0.3.1_linux_amd64.deb -f

RHEL:

curl -L https://github.com/aquasecurity/kube-bench/releases/download/v0.3.1/kube-bench_0.3.1_linux_amd64.rpm -o kube-bench_0.3.1_linux_amd64.rpm

sudo yum install kube-bench_0.3.1_linux_amd64.rpm -y

Alternatively, you can manually download and extract the kube-bench binary:

curl -L https://github.com/aquasecurity/kube-bench/releases/download/v0.3.1/kube-bench_0.3.1_linux_amd64.tar.gz -o kube-bench_0.3.1_linux_amd64.tar.gz

tar -xvf kube-bench_0.3.1_linux_amd64.tar.gz

You can then run kube-bench directly:

kube-bench

If you manually downloaded the kube-bench binary (using curl command above), you have to specify the location of configuration directory and file. For example:

./kube-bench --config-dir `pwd`/cfg --config `pwd`/cfg/config.yaml 

See previous section on Running kube-bench for further details on using the kube-bench binary.

Installing from sources

If Go is installed on the target machines, you can simply clone this repository and run as follows (assuming your GOPATH is set):

go get github.com/aquasecurity/kube-bench
cd $GOPATH/src/github.com/aquasecurity/kube-bench
go build -o kube-bench .

# See all supported options
./kube-bench --help

# Run all checks
./kube-bench

Output

There are four output states:

• [PASS] indicates that the test was run successfully, and passed.
• [FAIL] indicates that the test was run successfully, and failed. The remediation output describes how to correct the configuration, or includes an error message describing why the test could not be run.
• [WARN] means this test needs further attention, for example it is a test that needs to be run manually. Check the remediation output for further information.
• [INFO] is informational output that needs no further action.

Note:

• If the test is Manual, this always generates WARN (because the user has to run it manually)
• If the test is Scored, and kube-bench was unable to run the test, this generates FAIL (because the test has not been passed, and as a Scored test, if it doesn't pass then it must be considered a failure).
• If the test is Not Scored, and kube-bench was unable to run the test, this generates WARN.
• If the test is Scored, type is empty, and there are no test_items present, it generates a WARN. This is to highlight tests that appear to be incompletely defined.

Configuration

Kubernetes configuration and binary file locations and names can vary from installation to installation, so these are configurable in the cfg/config.yaml file.

Any settings in the version-specific config file cfg/<version>/config.yaml take precedence over settings in the main cfg/config.yaml file.

You can read more about kube-bench configuration in our documentation.

Troubleshooting

Running kube-bench with the -v 3 parameter will generate debug logs that can be very helpful for debugging problems.

If you are using one of the example job*.yaml files, you will need to edit the command field, for example ["kube-bench", "-v", "3"]. Once the job has run, the logs can be retrieved using kubectl logs on the job's pod.

Test config YAML representation

The tests (or "controls") are represented as YAML documents (installed by default into ./cfg). There are different versions of these test YAML files reflecting different versions of the CIS Kubernetes Benchmark. You will find more information about the test file YAML definitions in our documentation.

Omitting checks

If you decide that a recommendation is not appropriate for your environment, you can choose to omit it by editing the test YAML file to give it the check type skip as in this example:

  checks:
  - id: 2.1.1
    text: "Ensure that the --allow-privileged argument is set to false (Scored)"
    type: "skip"
    scored: true

No tests will be run for this check and the output will be marked [INFO].

Roadmap

Going forward we plan to release updates to kube-bench to add support for new releases of the CIS Benchmark. Note that these are not released as frequently as Kubernetes releases.

We welcome PRs and issue reports.

Testing locally with kind

Our makefile contains targets to test your current version of kube-bench inside a Kind cluster. This can be very handy if you don't want to run a real Kubernetes cluster for development purposes.

First, you'll need to create the cluster using make kind-test-cluster this will create a new cluster if it cannot be found on your machine. By default, the cluster is named kube-bench but you can change the name by using the environment variable KIND_PROFILE.

If kind cannot be found on your system the target will try to install it using go get

Next, you'll have to build the kube-bench docker image using make build-docker, then we will be able to push the docker image to the cluster using make kind-push.

Finally, we can use the make kind-run target to run the current version of kube-bench in the cluster and follow the logs of pods created. (Ctrl+C to exit)

Every time you want to test a change, you'll need to rebuild the docker image and push it to cluster before running it again. ( make build-docker kind-push kind-run )

Contributing

Kindly read Contributing.md before contributing. Some instructions for the common contributions are stated below.

Bugs

If you think you have found a bug please follow the instructions below.

• Please spend a small amount of time giving due diligence to the issue tracker. Your issue might be a duplicate.
• Open a new issue if a duplicate doesn't already exist.
• Note the version of kube-bench you are running (from kube-bench version) and the command line options you are using.
• Note the version of Kubernetes you are running (from kubectl version or oc version for OpenShift).
• Set -v 10 command line option and save the log output. Please paste this into your issue.
• Remember users might be searching for your issue in the future, so please give it a meaningful title to help others.

Features

We also use the GitHub issue tracker to track feature requests. If you have an idea to make kube-bench even more awesome follow the steps below.

• Open a new issue.
• Remember users might be searching for your issue in the future, so please give it a meaningful title to helps others.
• Clearly define the use case, using concrete examples. For example, I type this and kube-bench does that.
• If you would like to include a technical design for your feature please feel free to do so.

Pull Requests

We welcome pull requests!

• Your PR is more likely to be accepted if it focuses on just one change.
• Please include a comment with the results before and after your change.
• Your PR is more likely to be accepted if it includes tests. (We have not historically been very strict about tests, but we would like to improve this!).
• You're welcome to submit a draft PR if you would like early feedback on an idea or an approach.
• Happy coding!