An AdminNetworkPolicy (ANP) is a cluster-scoped custom resource definition (CRD). As a OpenShift Container Platform administrator, you can use ANP to secure your network by creating network policies before creating namespaces. Additionally, you can create network policies on a cluster-scoped level that is non-overridable by NetworkPolicy objects.
The key difference between AdminNetworkPolicy and NetworkPolicy objects are that the former is for administrators and is cluster scoped while the latter is for tenant owners and is namespace scoped.
An ANP allows administrators to specify the following:
-
A priority value that determines the order of its evaluation. The lower the value the higher the precedence.
-
A set of pods that consists of a set of namespaces or namespace on which the policy is applied.
-
A list of ingress rules to be applied for all ingress traffic towards the subject.
-
A list of egress rules to be applied for all egress traffic from the subject.
AdminNetworkPolicy example
Example YAML file for an ANP
apiVersion: policy.networking.k8s.io/v1alpha1
kind: AdminNetworkPolicy
metadata:
name: sample-anp-deny-pass-rules (1)
spec:
priority: 50 (2)
subject:
namespaces:
matchLabels:
kubernetes.io/metadata.name: example.name (3)
ingress: (4)
- name: "deny-all-ingress-tenant-1" (5)
action: "Deny"
from:
- pods:
namespaceSelector:
matchLabels:
custom-anp: tenant-1
podSelector:
matchLabels:
custom-anp: tenant-1 (6)
egress:(7)
- name: "pass-all-egress-to-tenant-1"
action: "Pass"
to:
- pods:
namespaceSelector:
matchLabels:
custom-anp: tenant-1
podSelector:
matchLabels:
custom-anp: tenant-1
| 1 |
Specify a name for your ANP. |
| 2 |
The spec.priority field supports a maximum of 100 ANP in the values of 0-99 in a cluster. The lower the value the higher the precedence. Creating AdminNetworkPolicy with the same priority creates a nondeterministic outcome. |
| 3 |
Specify the namespace to apply the ANP resource. |
| 4 |
ANP have both ingress and egress rules. ANP rules for spec.ingress field accepts values of Pass, Deny, and Allow for the action field. |
| 5 |
Specify a name for the ingress.name. |
| 6 |
Specify podSelector.matchLabels to select pods within the namespaces selected by namespaceSelector.matchLabels as ingress peers. |
| 7 |
ANPs have both ingress and egress rules. ANP rules for spec.egress field accepts values of Pass, Deny, and Allow for the action field. |
AdminNetworkPolicy actions for rules
As an administrator, you can set Allow, Deny, or Pass as the action field for your AdminNetworkPolicy rules. Because OVN-Kubernetes uses a tiered ACLs to evaluate network traffic rules, ANP allow you to set very strong policy rules that can only be changed by an administrator modifying them, deleting the rule, or overriding them by setting a higher priority rule.
AdminNetworkPolicy Allow example
The following ANP that is defined at priority 9 ensures all ingress traffic is allowed from the monitoring namespace towards any tenant (all other namespaces) in the cluster.
Example YAML file for a strong Allow ANP
apiVersion: policy.networking.k8s.io/v1alpha1
kind: AdminNetworkPolicy
metadata:
name: allow-monitoring
spec:
priority: 9
subject:
namespaces: {} # Use the empty selector with caution because it also selects OpenShift namespaces as well.
ingress:
- name: "allow-ingress-from-monitoring"
action: "Allow"
from:
- namespaces:
matchLabels:
kubernetes.io/metadata.name: monitoring
# ...
This is an example of a strong Allow ANP because it is non-overridable by all the parties involved. No tenants can block themselves from being monitored using NetworkPolicy objects and the monitoring tenant also has no say in what it can or cannot monitor.
AdminNetworkPolicy Deny example
The following ANP that is defined at priority 5 ensures all ingress traffic from the monitoring namespace is blocked towards restricted tenants (namespaces that have labels security: restricted).
Example YAML file for a strong Deny ANP
apiVersion: policy.networking.k8s.io/v1alpha1
kind: AdminNetworkPolicy
metadata:
name: block-monitoring
spec:
priority: 5
subject:
namespaces:
matchLabels:
security: restricted
ingress:
- name: "deny-ingress-from-monitoring"
action: "Deny"
from:
- namespaces:
matchLabels:
kubernetes.io/metadata.name: monitoring
# ...
This is a strong Deny ANP that is non-overridable by all the parties involved. The restricted tenant owners cannot authorize themselves to allow monitoring traffic, and the infrastructure’s monitoring service cannot scrape anything from these sensitive namespaces.
When combined with the strong Allow example, the block-monitoring ANP has a lower priority value giving it higher precedence, which ensures restricted tenants are never monitored.
AdminNetworkPolicy Pass example
TThe following ANP that is defined at priority 7 ensures all ingress traffic from the monitoring namespace towards internal infrastructure tenants (namespaces that have labels security: internal) are passed on to tier 2 of the ACLs and evaluated by the namespaces’ NetworkPolicy objects.
Example YAML file for a strong Pass ANP
apiVersion: policy.networking.k8s.io/v1alpha1
kind: AdminNetworkPolicy
metadata:
name: pass-monitoring
spec:
priority: 7
subject:
namespaces:
matchLabels:
security: internal
ingress:
- name: "pass-ingress-from-monitoring"
action: "Pass"
from:
- namespaces:
matchLabels:
kubernetes.io/metadata.name: monitoring
# ...
This example is a strong Pass action ANP because it delegates the decision to NetworkPolicy objects defined by tenant owners. This pass-monitoring ANP allows all tenant owners grouped at security level internal to choose if their metrics should be scraped by the infrastructures' monitoring service using namespace scoped NetworkPolicy objects.
