Pod Security Standards

The Pod Security Standards define three different policies to broadly cover the security spectrum. These policies are cumulative and range from highly-permissive to highly-restrictive. This guide outlines the requirements of each policy.

The Privileged policy is purposely-open, and entirely unrestricted. This type of policy is typically aimed at system- and infrastructure-level workloads managed by privileged, trusted users.

The Privileged policy is defined by an absence of restrictions. Allow-by-default mechanisms (such as gatekeeper) may be Privileged by default. In contrast, for a deny-by-default mechanism (such as Pod Security Policy) the Privileged policy should disable all restrictions.

Baseline

The Baseline policy is aimed at ease of adoption for common containerized workloads while preventing known privilege escalations. This policy is targeted at application operators and developers of non-critical applications. The following listed controls should be enforced/disallowed:

Note: In this table, wildcards () indicate all elements in a list. For example, spec.containers[*].securityContext refers to the Security Context object for all defined containers. If any of the listed containers fails to meet the requirements, the entire pod will fail validation.

The Restricted policy is aimed at enforcing current Pod hardening best practices, at the expense of some compatibility. It is targeted at operators and developers of security-critical applications, as well as lower-trust users. The following listed controls should be enforced/disallowed:

Note: In this table, wildcards (*) indicate all elements in a list. For example, spec.containers[*].securityContext refers to the Security Context object for all defined containers. If any of the listed containers fails to meet the requirements, the entire pod will fail validation.

Decoupling policy definition from policy instantiation allows for a common understanding and consistent language of policies across clusters, independent of the underlying enforcement mechanism.

As mechanisms mature, they will be defined below on a per-policy basis. The methods of enforcement of individual policies are not defined here.

• Privileged namespace
• Restricted namespace

Alternatives

Note: This section links to third party projects that provide functionality required by Kubernetes. The Kubernetes project authors aren’t responsible for these projects, which are listed alphabetically. To add a project to this list, read the content guide before submitting a change.

Other alternatives for enforcing policies are being developed in the Kubernetes ecosystem, such as:

• Kubewarden
• OPA Gatekeeper

Kubernetes lets you use nodes that run either Linux or Windows. You can mix both kinds of node in one cluster. Windows in Kubernetes has some limitations and differentiators from Linux-based workloads. Specifically, many of the Pod securityContext fields have no effect on Windows.

Note: Kubelets prior to v1.24 don’t enforce the pod OS field, and if a cluster has nodes on versions earlier than v1.24 the restricted policies should be pinned to a version prior to v1.25.

Another important change, made in Kubernetes v1.25 is that the restricted Pod security has been updated to use the pod.spec.os.name field. Based on the OS name, certain policies that are specific to a particular OS can be relaxed for the other OS.

OS-specific policy controls

Restrictions on the following controls are only required if is not windows:

• Privilege Escalation
• Linux Capabilities

Why isn’t there a profile between privileged and baseline?

The three profiles defined here have a clear linear progression from most secure (restricted) to least secure (privileged), and cover a broad set of workloads. Privileges required above the baseline policy are typically very application specific, so we do not offer a standard profile in this niche. This is not to say that the privileged profile should always be used in this case, but that policies in this space need to be defined on a case-by-case basis.

SIG Auth may reconsider this position in the future, should a clear need for other profiles arise.

Security Contexts configure Pods and Containers at runtime. Security contexts are defined as part of the Pod and container specifications in the Pod manifest, and represent parameters to the container runtime.

Security profiles are control plane mechanisms to enforce specific settings in the Security Context, as well as other related parameters outside the Security Context. As of July 2021, are deprecated in favor of the built-in Pod Security Admission Controller.

What about sandboxed Pods?

There is not currently an API standard that controls whether a Pod is considered sandboxed or not. Sandbox Pods may be identified by the use of a sandboxed runtime (such as gVisor or Kata Containers), but there is no standard definition of what a sandboxed runtime is.

Additionally, the protection of sandboxed workloads is highly dependent on the method of sandboxing. As such, no single recommended profile is recommended for all sandboxed workloads.