PSA (Pod Security Admission)

Mon, 01 Jan 0001 00:00:00 +0000

Pod Security Admission (PSA) is the built-in Kubernetes admission controller that enforces the Pod Security Standards (PSS), a set of predefined security profiles that constrain what a pod is allowed to do. It became stable in Kubernetes 1.25, at which point its predecessor PodSecurityPolicy (PSP) was simultaneously removed. Where PSP was a complex, cluster-scoped object requiring deep RBAC wiring and prone to misconfiguration, PSA is deliberately simpler: it is always enabled, requires no CRDs or RBAC setup, and is configured entirely through namespace labels. The trade-off for that simplicity is that PSA is opinionated and coarse-grained — it enforces fixed profiles rather than arbitrary custom rules, and its granularity is the namespace rather than the individual workload or service account. Teams needing finer-grained policy beyond what PSA offers typically combine it with a policy engine such as Kyverno or OPA Gatekeeper.

SCC (Security Context Constraints)

Mon, 01 Jan 0001 00:00:00 +0000

Security Context Constraints (SCCs) are OpenShift’s mechanism for controlling and enforcing the security posture of pods at admission time. They predate and are more expressive than Kubernetes PSA: where PSA validates a pod spec against a fixed profile and either admits or rejects it, an SCC acts as both a validator and a mutator — it can inject missing fields into the pod spec (a UID from the namespace’s allocated range, an SELinux context, capability drops) so that a pod that did not specify its full security context in its manifest is brought into compliance automatically rather than rejected. SCCs are cluster-scoped resources, and access to them is controlled via RBAC: a service account must be granted use of an SCC through a Role or ClusterRole binding before pods running under that service account can be admitted with the permissions that SCC grants.

Workloads on Le Site de François

PSA (Pod Security Admission)

SCC (Security Context Constraints)