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Default Seccomp Profile

Default Seccomp Profile and Configuration

This is a short guide describing how to enable the defaulting of seccomp profiles for Gardener managed workloads in the seed.

Default Kubernetes Behavior

The state of Kubernetes in versions < 1.25 is such that all workloads by default run in Unconfined (seccomp disabled) mode. This is undesirable since this is the least restrictive profile. Also, mind that any privileged container will always run as Unconfined. More information about seccomp can be found in this Kubernetes tutorial.

Setting the Seccomp Profile to RuntimeDefault for Seed Clusters

To address the above issue, Gardener provides a webhook that is capable of mutating pods in the seed clusters, explicitly providing them with a seccomp profile type of RuntimeDefault. This profile is defined by the container runtime and represents a set of default syscalls that are allowed or not.

spec:
  securityContext:
    seccompProfile:
      type: RuntimeDefault

A Pod is mutated when all of the following preconditions are fulfilled:

  1. The Pod is created in a Gardener managed namespace.
  2. The Pod is NOT labeled with seccompprofile.resources.gardener.cloud/skip.
  3. The Pod does NOT explicitly specify .spec.securityContext.seccompProfile.type.

How to Configure

To enable this feature, the gardenlet DefaultSeccompProfile feature gate must be set to true.

featureGates:
  DefaultSeccompProfile: true

Please refer to the examples in this yaml file for more information.

Once the feature gate is enabled, the webhook will be registered and configured for the seed cluster. Newly created pods will be mutated to have their seccomp profile set to RuntimeDefault.

Note: Please note that this feature is still in Alpha, so you might see instabilities every now and then.

Setting the Seccomp Profile to RuntimeDefault for Shoot Clusters

For Kubernetes shoot versions >= 1.25, you can enable the use of RuntimeDefault as the default seccomp profile for all workloads. If enabled, the kubelet will use the RuntimeDefault seccomp profile by default, which is defined by the container runtime, instead of using the Unconfined mode. More information for this feature can be found in the Kubernetes documentation.

To use seccomp profile defaulting, you must run the kubelet with the SeccompDefault feature gate enabled (this is the default for k8s versions >= 1.25).

How to Configure

To enable this feature, the kubelet seccompDefault configuration parameter must be set to true in the shoot's spec.

spec:
  kubernetes:
    version: 1.25.0
    kubelet:
      seccompDefault: true

Please refer to the examples in this yaml file for more information.