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Configuring seccomp profiles

An OKD container or a pod runs a single application that performs one or more well-defined tasks. The application usually requires only a small subset of the underlying operating system kernel APIs. Seccomp, secure computing mode, is a Linux kernel feature that can be used to limit the process running in a container to only call a subset of the available system calls. These system calls can be configured by creating a profile that is applied to a container or pod. Seccomp profiles are stored as JSON files on the disk.

OpenShift workloads run unconfined by default, without any seccomp profile applied.

Seccomp profiles cannot be applied to privileged containers.

Enabling the default seccomp profile for all pods

OKD ships with a default seccomp profile that is referenced as runtime/default. You can enable the default seccomp profile for a pod or container workload by creating a custom Security Context Constraint (SCC).

There is a requirement to create a custom SCC. Do not edit the default SCCs. Editing the default SCCs can lead to issues when some of the platform pods deploy or OKD is upgraded. For more information, see the section entitled "Default security context constraints".

Follow these steps to enable the default seccomp profile for all pods:

  1. Export the available restricted SCC to a yaml file:

    $ oc get scc restricted -o yaml > restricted-seccomp.yaml

  2. Edit the created restricted SCC yaml file:

    $ vi restricted-seccomp.yaml

  3. Update as shown in this example:

    kind: SecurityContextConstraints
metadata:
  name: restricted  (1)
<..snip..>
seccompProfiles:    (2)
- runtime/default   (3)
    1 Change to restricted-seccomp
    2 Add seccompProfiles:
    3 Add - runtime/default

  4. Create the custom SCC:

    $ oc create -f restricted-seccomp.yaml
    Expected output
    securitycontextconstraints.security.openshift.io/restricted-seccomp created

  5. Add the custom SCC to the ServiceAccount:

    $ oc adm policy add-scc-to-user restricted-seccomp -z default

    The default service account is the ServiceAccount that is applied unless the user configures a different one. OKD configures the seccomp profile of the pod based on the information in the SCC.
    Expected output
    clusterrole.rbac.authorization.k8s.io/system:openshift:scc:restricted-seccomp added: "default"

In OKD 4.6 the ability to add the pod annotations seccomp.security.alpha.kubernetes.io/pod: runtime/default and container.seccomp.security.alpha.kubernetes.io/<container_name>: runtime/default is deprecated.

Configuring a custom seccomp profile

You can configure a custom seccomp profile, which allows you to update the filters based on the application requirements. This allows cluster administrators to have greater control over the security of workloads running in OpenShift Container Platform.

Setting up the custom seccomp profile

Prerequisite

  • You have cluster administrator permissions.

  • You have created a custom security context constraints (SCC). For more information, see "Additional resources".

  • You have created a custom seccomp profile.

Procedure

  1. Upload your custom seccomp profile to /var/lib/kubelet/seccomp/<custom-name>.json by using the Machine Config. See "Additional resources" for detailed steps.

  2. Update the custom SCC by providing reference to the created custom seccomp profile:

    seccompProfiles:
- localhost/<custom-name>.json (1)
    1 Provide the name of your custom seccomp profile.

Applying the custom seccomp profile to the workload

Prerequisite

  • The cluster administrator has set up the custom seccomp profile. For more details, see "Setting up the custom seccomp profile".

Procedure

  • Apply the seccomp profile to the workload by setting the securityContext.seccompProfile.type field as following:

    Example
    spec:
  securityContext:
    seccompProfile:
      type: Localhost
      localhostProfile: <custom-name>.json (1)
    1 Provide the name of your custom seccomp profile.

    Alternatively, you can use the pod annotations seccomp.security.alpha.kubernetes.io/pod: localhost/<custom-name>.json. However, this method is deprecated in OKD 4.6.

During deployment, the admission controller validates the following:

  • The annotations against the current SCCs allowed by the user role.

  • The SCC, which includes the seccomp profile, is allowed for the pod.

If the SCC is allowed for the pod, the kubelet runs the pod with the specified seccomp profile.

Ensure that the seccomp profile is deployed to all worker nodes.

The custom SCC must have the appropriate priority to be automatically assigned to the pod or meet other conditions required by the pod, such as allowing CAP_NET_ADMIN.

Additional resources