Access Policy¶

Info

Network policies are only applied in GCP clusters.

However, inbound rules for authorization in the context of TokenX or Azure AD apply to all clusters.

Access Policy¶

Access policies express which applications and services you are able to communicate with, both inbound and outbound. The default policy is to deny all incoming and outgoing traffic for your application, meaning you must be conscious of which services/application you consume, and who your consumers are.

Warning

The Access policies only apply when communicating interally within the cluster with service discovery.

Outbound requests to ingresses are regarded as external hosts, even if these ingresses exist in the same cluster.

Analogously, inbound access policies are thus not enforced for requests coming through exposed ingresses.

Inbound rules¶

Inbound rules specifies what other applications in the same cluster your application receives traffic from.

Receive requests from other app in the same namespace¶

For app app-a to be able to receive incoming requests from app-b in the same cluster and the same namespace, this specification is needed for app-a:

apiVersion: "nais.io/v1alpha1"
kind: "Application"
metadata:
  name: app-a
...
spec:
  ...
  accessPolicy:
    inbound:
      rules:
        - application: app-b

Receive requests from other app in the another namespace¶

For app app-a to be able to receive incoming requests from app-b in the same cluster but another namespace (othernamespace), this specification is needed for app-a:

apiVersion: "nais.io/v1alpha1"
kind: "Application"
metadata:
  name: app-a
...
spec:
  ...
  accessPolicy:
    inbound:
      rules:
        - application: app-b
          namespace: othernamespace

Outbound rules¶

Inbound rules specifies what other applications your application receives traffic from. spec.accessPolicy.outbound.rules specifies which applications in the same cluster to open for. To open for external applications, use the field spec.accessPolicy.outbound.external.

Send requests to other app in the same namespace¶

For app app-a to be able to send requests to app-b in the same cluster and the same namespace, this specification is needed for app-a:

apiVersion: "nais.io/v1alpha1"
kind: "Application"
metadata:
  name: app-a
...
spec:
  ...
  accessPolicy:
    outbound:
      rules:
        - application: app-b

Send requests to other app in the another namespace¶

For app app-a to be able to send requests requests to app-b in the same cluster but in another namespace (othernamespace), this specification is needed for app-a:

apiVersion: "nais.io/v1alpha1"
kind: "Application"
metadata:
  name: app-a
...
spec:
  ...
  accessPolicy:
    outbound:
      rules:
        - application: app-b
          namespace: othernamespace

External services¶

In order to send requests to services outside of the cluster, external.host is needed:

apiVersion: "nais.io/v1alpha1"
kind: "Application"
metadata:
  name: app-a
...
spec:
  ...
  accessPolicy:
    outbound:
      external: 
        - host: www.external-application.com

Global Service Entries

There are some services that are automatically added to the mesh in dev-gcp and prod-gcp (search for global_serviceentries).

Advanced: Resources created by Naiserator¶

The previous application manifest examples will create Kubernetes Network Policies.

Kubernetes Network Policy¶

Default policy

Every app created will have this default network policy that allows traffic to Linkerd and kube-dns. It also allows incoming traffic from the Linkerd control plane and from tap and prometheus in the linkerd-viz namespace. This is what enables monitoring via the linkerd dashboard. These policies will be created for every app, also those who don't have any access policies specified.

apiVersion: extensions/v1beta1
kind: NetworkPolicy
metadata:
  labels:
    app: appname
    team: teamname
  name: appname
  namespace: teamname
spec:
  egress:
    - to:
        - namespaceSelector:
            matchLabels:
              linkerd.io/is-control-plane: "true"
        - namespaceSelector: {}
          podSelector:
            matchLabels:
              k8s-app: kube-dns
        - ipBlock:
            cidr: 0.0.0.0/0
            except:
              - 10.6.0.0/15
              - 172.16.0.0/12
              - 192.168.0.0/16
  ingress:
    - from:
        - namespaceSelector:
            matchLabels:
              linkerd.io/is-control-plane: "true"
    - from:
        - namespaceSelector:
            matchLabels:
              linkerd.io/extension: viz
          podSelector:
            matchLabels:
              component: tap
    - from:
        - namespaceSelector:
            matchLabels:
              linkerd.io/extension: viz
          podSelector:
            matchLabels:
              component: prometheus
  podSelector:
    matchLabels:
      app: appname
  policyTypes:
    - Ingress
    - Egress

Kubernetes network policies

The applications specified in spec.accessPolicy.inbound.rules and spec.accessPolicy.outbound.rules will append these fields to the default Network Policy:

apiVersion: extensions/v1beta1
kind: NetworkPolicy
...
spec:
  egress:
  - to:
    ...
    - namespaceSelector:
        matchLabels:
          name: othernamespace
      podSelector:
        matchLabels:
          app: app-b
    - podSelector:
        matchLabels:
          app: app-b  
  - from:
    - namespaceSelector:
        matchLabels:
          name: othernamespace
      podSelector:
        matchLabels:
          app: app-b
    - podSelector:
        matchLabels:
          app: app-b    
  podSelector:
    matchLabels:
      app: appname
  policyTypes:
  - Egress
  - Ingress

Info

Note that for namespace match labels to work, the namespaces must be labeled with name: namespacename.

kube-system should be labeled accordingly for the default rule that allows traffic to kube-dns, but in GCP, the label is removed by some job in regular intervals...

Last update: 2021-11-01
Created: 2019-10-04