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Security is an important concern for most organizations and people who run Kubernetes clusters. You can find a basic security checklist elsewhere in the Kubernetes documentation.
To learn how to deploy and manage security aspects of Kubernetes, you can follow the tutorials in this section.
Pod Security is an admission controller that carries out checks against the Kubernetes
Pod Security Standards when new pods are
created. It is a feature GA'ed in v1.25.
This tutorial shows you how to enforce the baseline Pod Security
Standard at the cluster level which applies a standard configuration
to all namespaces in a cluster.
To apply Pod Security Standards to specific namespaces, refer to Apply Pod Security Standards at the namespace level.
If you are running a version of Kubernetes other than v1.29, check the documentation for that version.
Install the following on your workstation:
This tutorial demonstrates what you can configure for a Kubernetes cluster that you fully control. If you are learning how to configure Pod Security Admission for a managed cluster where you are not able to configure the control plane, read Apply Pod Security Standards at the namespace level.
Pod Security Admission
lets you apply built-in Pod Security Standards
with the following modes: enforce, audit, and warn.
To gather information that helps you to choose the Pod Security Standards that are most appropriate for your configuration, do the following:
Create a cluster with no Pod Security Standards applied:
kind create cluster --name psa-wo-cluster-pss
The output is similar to:
Creating cluster "psa-wo-cluster-pss" ...
✓ Ensuring node image (kindest/node:v1.29.2) 🖼
✓ Preparing nodes 📦
✓ Writing configuration 📜
✓ Starting control-plane 🕹️
✓ Installing CNI 🔌
✓ Installing StorageClass 💾
Set kubectl context to "kind-psa-wo-cluster-pss"
You can now use your cluster with:
kubectl cluster-info --context kind-psa-wo-cluster-pss
Thanks for using kind! 😊
Set the kubectl context to the new cluster:
kubectl cluster-info --context kind-psa-wo-cluster-pss
The output is similar to this:
Kubernetes control plane is running at https://127.0.0.1:61350
CoreDNS is running at https://127.0.0.1:61350/api/v1/namespaces/kube-system/services/kube-dns:dns/proxy
To further debug and diagnose cluster problems, use 'kubectl cluster-info dump'.
Get a list of namespaces in the cluster:
kubectl get ns
The output is similar to this:
NAME STATUS AGE
default Active 9m30s
kube-node-lease Active 9m32s
kube-public Active 9m32s
kube-system Active 9m32s
local-path-storage Active 9m26s
Use --dry-run=server to understand what happens when different Pod Security Standards
are applied:
Privileged
kubectl label --dry-run=server --overwrite ns --all \
pod-security.kubernetes.io/enforce=privileged
The output is similar to:
namespace/default labeled
namespace/kube-node-lease labeled
namespace/kube-public labeled
namespace/kube-system labeled
namespace/local-path-storage labeled
Baseline
kubectl label --dry-run=server --overwrite ns --all \
pod-security.kubernetes.io/enforce=baseline
The output is similar to:
namespace/default labeled
namespace/kube-node-lease labeled
namespace/kube-public labeled
Warning: existing pods in namespace "kube-system" violate the new PodSecurity enforce level "baseline:latest"
Warning: etcd-psa-wo-cluster-pss-control-plane (and 3 other pods): host namespaces, hostPath volumes
Warning: kindnet-vzj42: non-default capabilities, host namespaces, hostPath volumes
Warning: kube-proxy-m6hwf: host namespaces, hostPath volumes, privileged
namespace/kube-system labeled
namespace/local-path-storage labeled
Restricted
kubectl label --dry-run=server --overwrite ns --all \
pod-security.kubernetes.io/enforce=restricted
The output is similar to:
namespace/default labeled
namespace/kube-node-lease labeled
namespace/kube-public labeled
Warning: existing pods in namespace "kube-system" violate the new PodSecurity enforce level "restricted:latest"
Warning: coredns-7bb9c7b568-hsptc (and 1 other pod): unrestricted capabilities, runAsNonRoot != true, seccompProfile
Warning: etcd-psa-wo-cluster-pss-control-plane (and 3 other pods): host namespaces, hostPath volumes, allowPrivilegeEscalation != false, unrestricted capabilities, restricted volume types, runAsNonRoot != true
Warning: kindnet-vzj42: non-default capabilities, host namespaces, hostPath volumes, allowPrivilegeEscalation != false, unrestricted capabilities, restricted volume types, runAsNonRoot != true, seccompProfile
Warning: kube-proxy-m6hwf: host namespaces, hostPath volumes, privileged, allowPrivilegeEscalation != false, unrestricted capabilities, restricted volume types, runAsNonRoot != true, seccompProfile
namespace/kube-system labeled
Warning: existing pods in namespace "local-path-storage" violate the new PodSecurity enforce level "restricted:latest"
Warning: local-path-provisioner-d6d9f7ffc-lw9lh: allowPrivilegeEscalation != false, unrestricted capabilities, runAsNonRoot != true, seccompProfile
namespace/local-path-storage labeled
From the previous output, you'll notice that applying the privileged Pod Security Standard shows no warnings
for any namespaces. However, baseline and restricted standards both have
warnings, specifically in the kube-system namespace.
In this section, you apply the following Pod Security Standards to the latest version:
baseline standard in enforce mode.restricted standard in warn and audit mode.The baseline Pod Security Standard provides a convenient
middle ground that allows keeping the exemption list short and prevents known
privilege escalations.
Additionally, to prevent pods from failing in kube-system, you'll exempt the namespace
from having Pod Security Standards applied.
When you implement Pod Security Admission in your own environment, consider the following:
Based on the risk posture applied to a cluster, a stricter Pod Security
Standard like restricted might be a better choice.
Exempting the kube-system namespace allows pods to run as
privileged in this namespace. For real world use, the Kubernetes project
strongly recommends that you apply strict RBAC
policies that limit access to kube-system, following the principle of least
privilege.
To implement the preceding standards, do the following:
Create a configuration file that can be consumed by the Pod Security Admission Controller to implement these Pod Security Standards:
mkdir -p /tmp/pss
cat <<EOF > /tmp/pss/cluster-level-pss.yaml
apiVersion: apiserver.config.k8s.io/v1
kind: AdmissionConfiguration
plugins:
- name: PodSecurity
configuration:
apiVersion: pod-security.admission.config.k8s.io/v1
kind: PodSecurityConfiguration
defaults:
enforce: "baseline"
enforce-version: "latest"
audit: "restricted"
audit-version: "latest"
warn: "restricted"
warn-version: "latest"
exemptions:
usernames: []
runtimeClasses: []
namespaces: [kube-system]
EOF
Configure the API server to consume this file during cluster creation:
cat <<EOF > /tmp/pss/cluster-config.yaml
kind: Cluster
apiVersion: kind.x-k8s.io/v1alpha4
nodes:
- role: control-plane
kubeadmConfigPatches:
- |
kind: ClusterConfiguration
apiServer:
extraArgs:
admission-control-config-file: /etc/config/cluster-level-pss.yaml
extraVolumes:
- name: accf
hostPath: /etc/config
mountPath: /etc/config
readOnly: false
pathType: "DirectoryOrCreate"
extraMounts:
- hostPath: /tmp/pss
containerPath: /etc/config
# optional: if set, the mount is read-only.
# default false
readOnly: false
# optional: if set, the mount needs SELinux relabeling.
# default false
selinuxRelabel: false
# optional: set propagation mode (None, HostToContainer or Bidirectional)
# see https://kubernetes.io/docs/concepts/storage/volumes/#mount-propagation
# default None
propagation: None
EOF
/tmp as a Shared Directory under the menu item
Preferences > Resources > File Sharing.
Create a cluster that uses Pod Security Admission to apply these Pod Security Standards:
kind create cluster --name psa-with-cluster-pss --config /tmp/pss/cluster-config.yaml
The output is similar to this:
Creating cluster "psa-with-cluster-pss" ...
✓ Ensuring node image (kindest/node:v1.29.2) 🖼
✓ Preparing nodes 📦
✓ Writing configuration 📜
✓ Starting control-plane 🕹️
✓ Installing CNI 🔌
✓ Installing StorageClass 💾
Set kubectl context to "kind-psa-with-cluster-pss"
You can now use your cluster with:
kubectl cluster-info --context kind-psa-with-cluster-pss
Have a question, bug, or feature request? Let us know! https://kind.sigs.k8s.io/#community 🙂
Point kubectl to the cluster:
kubectl cluster-info --context kind-psa-with-cluster-pss
The output is similar to this:
Kubernetes control plane is running at https://127.0.0.1:63855
CoreDNS is running at https://127.0.0.1:63855/api/v1/namespaces/kube-system/services/kube-dns:dns/proxy
To further debug and diagnose cluster problems, use 'kubectl cluster-info dump'.
Create a Pod in the default namespace:
apiVersion: v1
kind: Pod
metadata:
name: nginx
spec:
containers:
- image: nginx
name: nginx
ports:
- containerPort: 80
kubectl apply -f https://k8s.io/examples/security/example-baseline-pod.yaml
The pod is started normally, but the output includes a warning:
Warning: would violate PodSecurity "restricted:latest": allowPrivilegeEscalation != false (container "nginx" must set securityContext.allowPrivilegeEscalation=false), unrestricted capabilities (container "nginx" must set securityContext.capabilities.drop=["ALL"]), runAsNonRoot != true (pod or container "nginx" must set securityContext.runAsNonRoot=true), seccompProfile (pod or container "nginx" must set securityContext.seccompProfile.type to "RuntimeDefault" or "Localhost")
pod/nginx created
Now delete the clusters which you created above by running the following command:
kind delete cluster --name psa-with-cluster-pss
kind delete cluster --name psa-wo-cluster-pss
Pod Security Admission is an admission controller that applies
Pod Security Standards
when pods are created. It is a feature GA'ed in v1.25.
In this tutorial, you will enforce the baseline Pod Security Standard,
one namespace at a time.
You can also apply Pod Security Standards to multiple namespaces at once at the cluster level. For instructions, refer to Apply Pod Security Standards at the cluster level.
Install the following on your workstation:
Create a kind cluster as follows:
kind create cluster --name psa-ns-level
The output is similar to this:
Creating cluster "psa-ns-level" ...
✓ Ensuring node image (kindest/node:v1.29.2) 🖼
✓ Preparing nodes 📦
✓ Writing configuration 📜
✓ Starting control-plane 🕹️
✓ Installing CNI 🔌
✓ Installing StorageClass 💾
Set kubectl context to "kind-psa-ns-level"
You can now use your cluster with:
kubectl cluster-info --context kind-psa-ns-level
Not sure what to do next? 😅 Check out https://kind.sigs.k8s.io/docs/user/quick-start/
Set the kubectl context to the new cluster:
kubectl cluster-info --context kind-psa-ns-level
The output is similar to this:
Kubernetes control plane is running at https://127.0.0.1:50996
CoreDNS is running at https://127.0.0.1:50996/api/v1/namespaces/kube-system/services/kube-dns:dns/proxy
To further debug and diagnose cluster problems, use 'kubectl cluster-info dump'.
Create a new namespace called example:
kubectl create ns example
The output is similar to this:
namespace/example created
Enable Pod Security Standards on this namespace using labels supported by built-in Pod Security Admission. In this step you will configure a check to warn on Pods that don't meet the latest version of the baseline pod security standard.
kubectl label --overwrite ns example \
pod-security.kubernetes.io/warn=baseline \
pod-security.kubernetes.io/warn-version=latest
You can configure multiple pod security standard checks on any namespace, using labels.
The following command will enforce the baseline Pod Security Standard, but
warn and audit for restricted Pod Security Standards as per the latest
version (default value)
kubectl label --overwrite ns example \
pod-security.kubernetes.io/enforce=baseline \
pod-security.kubernetes.io/enforce-version=latest \
pod-security.kubernetes.io/warn=restricted \
pod-security.kubernetes.io/warn-version=latest \
pod-security.kubernetes.io/audit=restricted \
pod-security.kubernetes.io/audit-version=latest
Create a baseline Pod in the example namespace:
kubectl apply -n example -f https://k8s.io/examples/security/example-baseline-pod.yaml
The Pod does start OK; the output includes a warning. For example:
Warning: would violate PodSecurity "restricted:latest": allowPrivilegeEscalation != false (container "nginx" must set securityContext.allowPrivilegeEscalation=false), unrestricted capabilities (container "nginx" must set securityContext.capabilities.drop=["ALL"]), runAsNonRoot != true (pod or container "nginx" must set securityContext.runAsNonRoot=true), seccompProfile (pod or container "nginx" must set securityContext.seccompProfile.type to "RuntimeDefault" or "Localhost")
pod/nginx created
Create a baseline Pod in the default namespace:
kubectl apply -n default -f https://k8s.io/examples/security/example-baseline-pod.yaml
Output is similar to this:
pod/nginx created
The Pod Security Standards enforcement and warning settings were applied only
to the example namespace. You could create the same Pod in the default
namespace with no warnings.
Now delete the cluster which you created above by running the following command:
kind delete cluster --name psa-ns-level
Run a shell script to perform all the preceding steps all at once.
baseline Pod Security Standard in enforce mode while applying
restricted Pod Security Standard also in warn and audit mode.Kubernetes v1.4 [beta]
AppArmor is a Linux kernel security module that supplements the standard Linux user and group based permissions to confine programs to a limited set of resources. AppArmor can be configured for any application to reduce its potential attack surface and provide greater in-depth defense. It is configured through profiles tuned to allow the access needed by a specific program or container, such as Linux capabilities, network access, file permissions, etc. Each profile can be run in either enforcing mode, which blocks access to disallowed resources, or complain mode, which only reports violations.
On Kubernetes, AppArmor can help you to run a more secure deployment by restricting what containers are allowed to do, and/or provide better auditing through system logs. However, it is important to keep in mind that AppArmor is not a silver bullet and can only do so much to protect against exploits in your application code. It is important to provide good, restrictive profiles, and harden your applications and cluster from other angles as well.
AppArmor is an optional kernel module and Kubernetes feature, so verify it is supported on your Nodes before proceeding:
AppArmor kernel module is enabled -- For the Linux kernel to enforce an AppArmor profile, the
AppArmor kernel module must be installed and enabled. Several distributions enable the module by
default, such as Ubuntu and SUSE, and many others provide optional support. To check whether the
module is enabled, check the /sys/module/apparmor/parameters/enabled file:
cat /sys/module/apparmor/parameters/enabled
Y
The Kubelet verifies that AppArmor is enabled on the host before admitting a pod with AppArmor explicitly configured.
Container runtime supports AppArmor -- All common Kubernetes-supported container runtimes should support AppArmor, including containerd and CRI-O. Please refer to the corresponding runtime documentation and verify that the cluster fulfills the requirements to use AppArmor.
Profile is loaded -- AppArmor is applied to a Pod by specifying an AppArmor profile that each
container should be run with. If any of the specified profiles are not loaded in the
kernel, the Kubelet will reject the Pod. You can view which profiles are loaded on a
node by checking the /sys/kernel/security/apparmor/profiles file. For example:
ssh gke-test-default-pool-239f5d02-gyn2 "sudo cat /sys/kernel/security/apparmor/profiles | sort"
apparmor-test-deny-write (enforce)
apparmor-test-audit-write (enforce)
docker-default (enforce)
k8s-nginx (enforce)
For more details on loading profiles on nodes, see Setting up nodes with profiles.
AppArmor profiles are specified per-container. To specify the AppArmor profile to run a Pod container with, add an annotation to the Pod's metadata:
container.apparmor.security.beta.kubernetes.io/<container_name>: <profile_ref>
Where <container_name> is the name of the container to apply the profile to, and <profile_ref>
specifies the profile to apply. The <profile_ref> can be one of:
runtime/default to apply the runtime's default profilelocalhost/<profile_name> to apply the profile loaded on the host with the name <profile_name>unconfined to indicate that no profiles will be loadedSee the API Reference for the full details on the annotation and profile name formats.
To verify that the profile was applied, you can check that the container's root process is running with the correct profile by examining its proc attr:
kubectl exec <pod_name> -- cat /proc/1/attr/current
The output should look something like this:
k8s-apparmor-example-deny-write (enforce)
This example assumes you have already set up a cluster with AppArmor support.
First, load the profile you want to use onto your Nodes. This profile denies all file writes:
#include <tunables/global>
profile k8s-apparmor-example-deny-write flags=(attach_disconnected) {
#include <abstractions/base>
file,
# Deny all file writes.
deny /** w,
}
The profile needs to loaded onto all nodes, since you don't know where the pod will be scheduled. For this example you can use SSH to install the profiles, but other approaches are discussed in Setting up nodes with profiles.
# This example assumes that node names match host names, and are reachable via SSH.
NODES=($(kubectl get nodes -o name))
for NODE in ${NODES[*]}; do ssh $NODE 'sudo apparmor_parser -q <<EOF
#include <tunables/global>
profile k8s-apparmor-example-deny-write flags=(attach_disconnected) {
#include <abstractions/base>
file,
# Deny all file writes.
deny /** w,
}
EOF'
done
Next, run a simple "Hello AppArmor" Pod with the deny-write profile:
apiVersion: v1
kind: Pod
metadata:
name: hello-apparmor
annotations:
# Tell Kubernetes to apply the AppArmor profile "k8s-apparmor-example-deny-write".
container.apparmor.security.beta.kubernetes.io/hello: localhost/k8s-apparmor-example-deny-write
spec:
containers:
- name: hello
image: busybox:1.28
command: [ "sh", "-c", "echo 'Hello AppArmor!' && sleep 1h" ]
kubectl create -f hello-apparmor.yaml
You can verify that the container is actually running with that profile by checking /proc/1/attr/current:
kubectl exec hello-apparmor -- cat /proc/1/attr/current
The output should be:
k8s-apparmor-example-deny-write (enforce)
Finally, you can see what happens if you violate the profile by writing to a file:
kubectl exec hello-apparmor -- touch /tmp/test
touch: /tmp/test: Permission denied
error: error executing remote command: command terminated with non-zero exit code: Error executing in Docker Container: 1
To wrap up, see what happens if you try to specify a profile that hasn't been loaded:
kubectl create -f /dev/stdin <<EOF
apiVersion: v1
kind: Pod
metadata:
name: hello-apparmor-2
annotations:
container.apparmor.security.beta.kubernetes.io/hello: localhost/k8s-apparmor-example-allow-write
spec:
containers:
- name: hello
image: busybox:1.28
command: [ "sh", "-c", "echo 'Hello AppArmor!' && sleep 1h" ]
EOF
pod/hello-apparmor-2 created
Although the Pod was created successfully, further examination will show that it is stuck in pending:
kubectl describe pod hello-apparmor-2
Name: hello-apparmor-2
Namespace: default
Node: gke-test-default-pool-239f5d02-x1kf/10.128.0.27
Start Time: Tue, 30 Aug 2016 17:58:56 -0700
Labels: <none>
Annotations: container.apparmor.security.beta.kubernetes.io/hello=localhost/k8s-apparmor-example-allow-write
Status: Pending
...
Events:
Type Reason Age From Message
---- ------ ---- ---- -------
Normal Scheduled 10s default-scheduler Successfully assigned default/hello-apparmor to gke-test-default-pool-239f5d02-x1kf
Normal Pulled 8s kubelet Successfully pulled image "busybox:1.28" in 370.157088ms (370.172701ms including waiting)
Normal Pulling 7s (x2 over 9s) kubelet Pulling image "busybox:1.28"
Warning Failed 7s (x2 over 8s) kubelet Error: failed to get container spec opts: failed to generate apparmor spec opts: apparmor profile not found k8s-apparmor-example-allow-write
Normal Pulled 7s kubelet Successfully pulled image "busybox:1.28" in 90.980331ms (91.005869ms including waiting)
An Event provides the error message with the reason, the specific wording is runtime-dependent:
Warning Failed 7s (x2 over 8s) kubelet Error: failed to get container spec opts: failed to generate apparmor spec opts: apparmor profile not found
Kubernetes does not currently provide any built-in mechanisms for loading AppArmor profiles onto Nodes. Profiles can be loaded through custom infrastructure or tools like the Kubernetes Security Profiles Operator.
The scheduler is not aware of which profiles are loaded onto which Node, so the full set of profiles must be loaded onto every Node. An alternative approach is to add a Node label for each profile (or class of profiles) on the Node, and use a node selector to ensure the Pod is run on a Node with the required profile.
Getting AppArmor profiles specified correctly can be a tricky business. Fortunately there are some tools to help with that:
aa-genprof and aa-logprof generate profile rules by monitoring an application's activity and
logs, and admitting the actions it takes. Further instructions are provided by the
AppArmor documentation.To debug problems with AppArmor, you can check the system logs to see what, specifically, was
denied. AppArmor logs verbose messages to dmesg, and errors can usually be found in the system
logs or through journalctl. More information is provided in
AppArmor failures.
Specifying the profile a container will run with:
container.apparmor.security.beta.kubernetes.io/<container_name>
Where <container_name> matches the name of a container in the Pod.
A separate profile can be specified for each container in the Pod.runtime/default: Refers to the default runtime profile.
localhost/<profile_name>: Refers to a profile loaded on the node (localhost) by name.
unconfined: This effectively disables AppArmor on the container.Any other profile reference format is invalid.
Additional resources:
Kubernetes v1.19 [stable]
Seccomp stands for secure computing mode and has been a feature of the Linux kernel since version 2.6.12. It can be used to sandbox the privileges of a process, restricting the calls it is able to make from userspace into the kernel. Kubernetes lets you automatically apply seccomp profiles loaded onto a node to your Pods and containers.
Identifying the privileges required for your workloads can be difficult. In this tutorial, you will go through how to load seccomp profiles into a local Kubernetes cluster, how to apply them to a Pod, and how you can begin to craft profiles that give only the necessary privileges to your container processes.
In order to complete all steps in this tutorial, you must install kind and kubectl.
The commands used in the tutorial assume that you are using
Docker as your container runtime. (The cluster that kind creates may
use a different container runtime internally). You could also use
Podman but in that case, you would have to follow specific
instructions in order to complete the tasks
successfully.
This tutorial shows some examples that are still beta (since v1.25) and others that use only generally available seccomp functionality. You should make sure that your cluster is configured correctly for the version you are using.
The tutorial also uses the curl tool for downloading examples to your computer.
You can adapt the steps to use a different tool if you prefer.
privileged: true set in the container's securityContext. Privileged containers always
run as Unconfined.
The contents of these profiles will be explored later on, but for now go ahead
and download them into a directory named profiles/ so that they can be loaded
into the cluster.
{
"defaultAction": "SCMP_ACT_LOG"
}
{
"defaultAction": "SCMP_ACT_ERRNO"
}
{
"defaultAction": "SCMP_ACT_ERRNO",
"architectures": [
"SCMP_ARCH_X86_64",
"SCMP_ARCH_X86",
"SCMP_ARCH_X32"
],
"syscalls": [
{
"names": [
"accept4",
"epoll_wait",
"pselect6",
"futex",
"madvise",
"epoll_ctl",
"getsockname",
"setsockopt",
"vfork",
"mmap",
"read",
"write",
"close",
"arch_prctl",
"sched_getaffinity",
"munmap",
"brk",
"rt_sigaction",
"rt_sigprocmask",
"sigaltstack",
"gettid",
"clone",
"bind",
"socket",
"openat",
"readlinkat",
"exit_group",
"epoll_create1",
"listen",
"rt_sigreturn",
"sched_yield",
"clock_gettime",
"connect",
"dup2",
"epoll_pwait",
"execve",
"exit",
"fcntl",
"getpid",
"getuid",
"ioctl",
"mprotect",
"nanosleep",
"open",
"poll",
"recvfrom",
"sendto",
"set_tid_address",
"setitimer",
"writev",
"fstatfs",
"getdents64",
"pipe2",
"getrlimit"
],
"action": "SCMP_ACT_ALLOW"
}
]
}Run these commands:
mkdir ./profiles
curl -L -o profiles/audit.json https://k8s.io/examples/pods/security/seccomp/profiles/audit.json
curl -L -o profiles/violation.json https://k8s.io/examples/pods/security/seccomp/profiles/violation.json
curl -L -o profiles/fine-grained.json https://k8s.io/examples/pods/security/seccomp/profiles/fine-grained.json
ls profiles
You should see three profiles listed at the end of the final step:
audit.json fine-grained.json violation.json
For simplicity, kind can be used to create a single node cluster with the seccomp profiles loaded. Kind runs Kubernetes in Docker, so each node of the cluster is a container. This allows for files to be mounted in the filesystem of each container similar to loading files onto a node.
apiVersion: kind.x-k8s.io/v1alpha4
kind: Cluster
nodes:
- role: control-plane
extraMounts:
- hostPath: "./profiles"
containerPath: "/var/lib/kubelet/seccomp/profiles"Download that example kind configuration, and save it to a file named kind.yaml:
curl -L -O https://k8s.io/examples/pods/security/seccomp/kind.yaml
You can set a specific Kubernetes version by setting the node's container image. See Nodes within the kind documentation about configuration for more details on this. This tutorial assumes you are using Kubernetes v1.29.
As a beta feature, you can configure Kubernetes to use the profile that the
container runtime
prefers by default, rather than falling back to Unconfined.
If you want to try that, see
enable the use of RuntimeDefault as the default seccomp profile for all workloads
before you continue.
Once you have a kind configuration in place, create the kind cluster with that configuration:
kind create cluster --config=kind.yaml
After the new Kubernetes cluster is ready, identify the Docker container running as the single node cluster:
docker ps
You should see output indicating that a container is running with name
kind-control-plane. The output is similar to:
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
6a96207fed4b kindest/node:v1.18.2 "/usr/local/bin/entr…" 27 seconds ago Up 24 seconds 127.0.0.1:42223->6443/tcp kind-control-plane
If observing the filesystem of that container, you should see that the
profiles/ directory has been successfully loaded into the default seccomp path
of the kubelet. Use docker exec to run a command in the Pod:
# Change 6a96207fed4b to the container ID you saw from "docker ps"
docker exec -it 6a96207fed4b ls /var/lib/kubelet/seccomp/profiles
audit.json fine-grained.json violation.json
You have verified that these seccomp profiles are available to the kubelet running within kind.
Most container runtimes provide a sane set of default syscalls that are allowed
or not. You can adopt these defaults for your workload by setting the seccomp
type in the security context of a pod or container to RuntimeDefault.
seccompDefault configuration
enabled, then Pods use the RuntimeDefault seccomp profile whenever
no other seccomp profile is specified. Otherwise, the default is Unconfined.
Here's a manifest for a Pod that requests the RuntimeDefault seccomp profile
for all its containers:
apiVersion: v1
kind: Pod
metadata:
name: default-pod
labels:
app: default-pod
spec:
securityContext:
seccompProfile:
type: RuntimeDefault
containers:
- name: test-container
image: hashicorp/http-echo:1.0
args:
- "-text=just made some more syscalls!"
securityContext:
allowPrivilegeEscalation: falseCreate that Pod:
kubectl apply -f https://k8s.io/examples/pods/security/seccomp/ga/default-pod.yaml
kubectl get pod default-pod
The Pod should be showing as having started successfully:
NAME READY STATUS RESTARTS AGE
default-pod 1/1 Running 0 20s
Delete the Pod before moving to the next section:
kubectl delete pod default-pod --wait --now
To start off, apply the audit.json profile, which will log all syscalls of the
process, to a new Pod.
Here's a manifest for that Pod:
apiVersion: v1
kind: Pod
metadata:
name: audit-pod
labels:
app: audit-pod
spec:
securityContext:
seccompProfile:
type: Localhost
localhostProfile: profiles/audit.json
containers:
- name: test-container
image: hashicorp/http-echo:1.0
args:
- "-text=just made some syscalls!"
securityContext:
allowPrivilegeEscalation: false.spec.securityContext to configure seccomp, and this tutorial explains that
approach.
Create the Pod in the cluster:
kubectl apply -f https://k8s.io/examples/pods/security/seccomp/ga/audit-pod.yaml
This profile does not restrict any syscalls, so the Pod should start successfully.
kubectl get pod audit-pod
NAME READY STATUS RESTARTS AGE
audit-pod 1/1 Running 0 30s
In order to be able to interact with this endpoint exposed by this container, create a NodePort Service that allows access to the endpoint from inside the kind control plane container.
kubectl expose pod audit-pod --type NodePort --port 5678
Check what port the Service has been assigned on the node.
kubectl get service audit-pod
The output is similar to:
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
audit-pod NodePort 10.111.36.142 <none> 5678:32373/TCP 72s
Now you can use curl to access that endpoint from inside the kind control plane container,
at the port exposed by this Service. Use docker exec to run the curl command within the
container belonging to that control plane container:
# Change 6a96207fed4b to the control plane container ID and 32373 to the port number you saw from "docker ps"
docker exec -it 6a96207fed4b curl localhost:32373
just made some syscalls!
You can see that the process is running, but what syscalls did it actually make?
Because this Pod is running in a local cluster, you should be able to see those
in /var/log/syslog on your local system. Open up a new terminal window and tail the output for
calls from http-echo:
# The log path on your computer might be different from "/var/log/syslog"
tail -f /var/log/syslog | grep 'http-echo'
You should already see some logs of syscalls made by http-echo, and if you run curl again inside
the control plane container you will see more output written to the log.
For example:
Jul 6 15:37:40 my-machine kernel: [369128.669452] audit: type=1326 audit(1594067860.484:14536): auid=4294967295 uid=0 gid=0 ses=4294967295 pid=29064 comm="http-echo" exe="/http-echo" sig=0 arch=c000003e syscall=51 compat=0 ip=0x46fe1f code=0x7ffc0000
Jul 6 15:37:40 my-machine kernel: [369128.669453] audit: type=1326 audit(1594067860.484:14537): auid=4294967295 uid=0 gid=0 ses=4294967295 pid=29064 comm="http-echo" exe="/http-echo" sig=0 arch=c000003e syscall=54 compat=0 ip=0x46fdba code=0x7ffc0000
Jul 6 15:37:40 my-machine kernel: [369128.669455] audit: type=1326 audit(1594067860.484:14538): auid=4294967295 uid=0 gid=0 ses=4294967295 pid=29064 comm="http-echo" exe="/http-echo" sig=0 arch=c000003e syscall=202 compat=0 ip=0x455e53 code=0x7ffc0000
Jul 6 15:37:40 my-machine kernel: [369128.669456] audit: type=1326 audit(1594067860.484:14539): auid=4294967295 uid=0 gid=0 ses=4294967295 pid=29064 comm="http-echo" exe="/http-echo" sig=0 arch=c000003e syscall=288 compat=0 ip=0x46fdba code=0x7ffc0000
Jul 6 15:37:40 my-machine kernel: [369128.669517] audit: type=1326 audit(1594067860.484:14540): auid=4294967295 uid=0 gid=0 ses=4294967295 pid=29064 comm="http-echo" exe="/http-echo" sig=0 arch=c000003e syscall=0 compat=0 ip=0x46fd44 code=0x7ffc0000
Jul 6 15:37:40 my-machine kernel: [369128.669519] audit: type=1326 audit(1594067860.484:14541): auid=4294967295 uid=0 gid=0 ses=4294967295 pid=29064 comm="http-echo" exe="/http-echo" sig=0 arch=c000003e syscall=270 compat=0 ip=0x4559b1 code=0x7ffc0000
Jul 6 15:38:40 my-machine kernel: [369188.671648] audit: type=1326 audit(1594067920.488:14559): auid=4294967295 uid=0 gid=0 ses=4294967295 pid=29064 comm="http-echo" exe="/http-echo" sig=0 arch=c000003e syscall=270 compat=0 ip=0x4559b1 code=0x7ffc0000
Jul 6 15:38:40 my-machine kernel: [369188.671726] audit: type=1326 audit(1594067920.488:14560): auid=4294967295 uid=0 gid=0 ses=4294967295 pid=29064 comm="http-echo" exe="/http-echo" sig=0 arch=c000003e syscall=202 compat=0 ip=0x455e53 code=0x7ffc0000
You can begin to understand the syscalls required by the http-echo process by
looking at the syscall= entry on each line. While these are unlikely to
encompass all syscalls it uses, it can serve as a basis for a seccomp profile
for this container.
Delete the Service and the Pod before moving to the next section:
kubectl delete service audit-pod --wait
kubectl delete pod audit-pod --wait --now
For demonstration, apply a profile to the Pod that does not allow for any syscalls.
The manifest for this demonstration is:
apiVersion: v1
kind: Pod
metadata:
name: violation-pod
labels:
app: violation-pod
spec:
securityContext:
seccompProfile:
type: Localhost
localhostProfile: profiles/violation.json
containers:
- name: test-container
image: hashicorp/http-echo:1.0
args:
- "-text=just made some syscalls!"
securityContext:
allowPrivilegeEscalation: falseAttempt to create the Pod in the cluster:
kubectl apply -f https://k8s.io/examples/pods/security/seccomp/ga/violation-pod.yaml
The Pod creates, but there is an issue. If you check the status of the Pod, you should see that it failed to start.
kubectl get pod violation-pod
NAME READY STATUS RESTARTS AGE
violation-pod 0/1 CrashLoopBackOff 1 6s
As seen in the previous example, the http-echo process requires quite a few
syscalls. Here seccomp has been instructed to error on any syscall by setting
"defaultAction": "SCMP_ACT_ERRNO". This is extremely secure, but removes the
ability to do anything meaningful. What you really want is to give workloads
only the privileges they need.
Delete the Pod before moving to the next section:
kubectl delete pod violation-pod --wait --now
If you take a look at the fine-grained.json profile, you will notice some of the syscalls
seen in syslog of the first example where the profile set "defaultAction": "SCMP_ACT_LOG". Now the profile is setting "defaultAction": "SCMP_ACT_ERRNO",
but explicitly allowing a set of syscalls in the "action": "SCMP_ACT_ALLOW"
block. Ideally, the container will run successfully and you will see no messages
sent to syslog.
The manifest for this example is:
apiVersion: v1
kind: Pod
metadata:
name: fine-pod
labels:
app: fine-pod
spec:
securityContext:
seccompProfile:
type: Localhost
localhostProfile: profiles/fine-grained.json
containers:
- name: test-container
image: hashicorp/http-echo:1.0
args:
- "-text=just made some syscalls!"
securityContext:
allowPrivilegeEscalation: falseCreate the Pod in your cluster:
kubectl apply -f https://k8s.io/examples/pods/security/seccomp/ga/fine-pod.yaml
kubectl get pod fine-pod
The Pod should be showing as having started successfully:
NAME READY STATUS RESTARTS AGE
fine-pod 1/1 Running 0 30s
Open up a new terminal window and use tail to monitor for log entries that
mention calls from http-echo:
# The log path on your computer might be different from "/var/log/syslog"
tail -f /var/log/syslog | grep 'http-echo'
Next, expose the Pod with a NodePort Service:
kubectl expose pod fine-pod --type NodePort --port 5678
Check what port the Service has been assigned on the node:
kubectl get service fine-pod
The output is similar to:
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
fine-pod NodePort 10.111.36.142 <none> 5678:32373/TCP 72s
Use curl to access that endpoint from inside the kind control plane container:
# Change 6a96207fed4b to the control plane container ID and 32373 to the port number you saw from "docker ps"
docker exec -it 6a96207fed4b curl localhost:32373
just made some syscalls!
You should see no output in the syslog. This is because the profile allowed all
necessary syscalls and specified that an error should occur if one outside of
the list is invoked. This is an ideal situation from a security perspective, but
required some effort in analyzing the program. It would be nice if there was a
simple way to get closer to this security without requiring as much effort.
Delete the Service and the Pod before moving to the next section:
kubectl delete service fine-pod --wait
kubectl delete pod fine-pod --wait --now
RuntimeDefault as the default seccomp profile for all workloadsKubernetes v1.27 [stable]
To use seccomp profile defaulting, you must run the kubelet with the
--seccomp-default
command line flag
enabled for each node where you want to use it.
If enabled, the kubelet will use the RuntimeDefault seccomp profile by default, which is
defined by the container runtime, instead of using the Unconfined (seccomp disabled) mode.
The default profiles aim to provide a strong set
of security defaults while preserving the functionality of the workload. It is
possible that the default profiles differ between container runtimes and their
release versions, for example when comparing those from CRI-O and containerd.
securityContext.seccompProfile API field nor add the deprecated annotations of
the workload. This provides users the possibility to rollback anytime without
actually changing the workload configuration. Tools like
crictl inspect can be used to
verify which seccomp profile is being used by a container.
Some workloads may require a lower amount of syscall restrictions than others.
This means that they can fail during runtime even with the RuntimeDefault
profile. To mitigate such a failure, you can:
Unconfined.SeccompDefault feature for the nodes. Also making sure that
workloads get scheduled on nodes where the feature is disabled.If you were introducing this feature into production-like cluster, the Kubernetes project recommends that you enable this feature gate on a subset of your nodes and then test workload execution before rolling the change out cluster-wide.
You can find more detailed information about a possible upgrade and downgrade strategy in the related Kubernetes Enhancement Proposal (KEP): Enable seccomp by default.
Kubernetes 1.29 lets you configure the seccomp profile that applies when the spec for a Pod doesn't define a specific seccomp profile. However, you still need to enable this defaulting for each node where you would like to use it.
If you are running a Kubernetes 1.29 cluster and want to
enable the feature, either run the kubelet with the --seccomp-default command
line flag, or enable it through the kubelet configuration
file. To enable the
feature gate in kind, ensure that kind provides
the minimum required Kubernetes version and enables the SeccompDefault feature
in the kind configuration:
kind: Cluster
apiVersion: kind.x-k8s.io/v1alpha4
nodes:
- role: control-plane
image: kindest/node:v1.28.0@sha256:9f3ff58f19dcf1a0611d11e8ac989fdb30a28f40f236f59f0bea31fb956ccf5c
kubeadmConfigPatches:
- |
kind: JoinConfiguration
nodeRegistration:
kubeletExtraArgs:
seccomp-default: "true"
- role: worker
image: kindest/node:v1.28.0@sha256:9f3ff58f19dcf1a0611d11e8ac989fdb30a28f40f236f59f0bea31fb956ccf5c
kubeadmConfigPatches:
- |
kind: JoinConfiguration
nodeRegistration:
kubeletExtraArgs:
seccomp-default: "true"
If the cluster is ready, then running a pod:
kubectl run --rm -it --restart=Never --image=alpine alpine -- sh
Should now have the default seccomp profile attached. This can be verified by
using docker exec to run crictl inspect for the container on the kind
worker:
docker exec -it kind-worker bash -c \
'crictl inspect $(crictl ps --name=alpine -q) | jq .info.runtimeSpec.linux.seccomp'
{
"defaultAction": "SCMP_ACT_ERRNO",
"architectures": ["SCMP_ARCH_X86_64", "SCMP_ARCH_X86", "SCMP_ARCH_X32"],
"syscalls": [
{
"names": ["..."]
}
]
}
You can learn more about Linux seccomp: