MeshTrafficPermission

Overview

MeshTrafficPermission policy defines which clients are allowed or denied access to services inside a mesh based on their identities. By default, if no policy is present, all requests are denied.

It enables:

• denying all requests by default, or blocking specific clients (by SPIFFE ID) so that no service owner can override them
• allowing groups of clients, such as everything in the observability namespace, to access all services by default, while still letting individual services opt out
• giving service owners control to allow specific clients, and the ability to block abusive ones even if they were previously allowed

Here is a common example:

apiVersion: kuma.io/v1alpha1
kind: MeshTrafficPermission
metadata:
  name: my-app-permissions
  namespace: kuma-system
  labels:
    kuma.io/mesh: my-mesh
spec:
  targetRef:
    kind: Dataplane
    labels:
      app: my-app
  rules:
  - default:
      deny:
      - spiffeID:
          type: Prefix
          value: spiffe://my-mesh.us-east-2.mesh.local/ns/legacy-ns
      - spiffeID:
          type: Exact
          value: spiffe://my-mesh.us-east-2.mesh.local/ns/test/sa/client
      allow:
      - spiffeID:
          type: Prefix
          value: spiffe://my-mesh.us-east-2.mesh.local

type: MeshTrafficPermission
name: my-app-permissions
mesh: my-mesh
spec:
  targetRef:
    kind: Dataplane
    labels:
      app: my-app
  rules:
  - default:
      deny:
      - spiffeID:
          type: Prefix
          value: spiffe://my-mesh.us-east-2.mesh.local/ns/legacy-ns
      - spiffeID:
          type: Exact
          value: spiffe://my-mesh.us-east-2.mesh.local/ns/test/sa/client
      allow:
      - spiffeID:
          type: Prefix
          value: spiffe://my-mesh.us-east-2.mesh.local

With this policy in place, workloads labeled app: my-app will reject connections from identities under the legacy-ns namespace as well as the specific test/client identity, while continuing to accept connections from all other identities within the my-mesh.us-east-2.mesh.local trust domain.

Configuration

MeshTrafficPermission policy provides a way to specify 3 lists:

• deny list – list of matches for clients that must always be denied.
• allow list – list of matchers for clients that are explicitly allowed.
• allowWithShadowDeny list – list of matchers that are allowed, but also logged as if they were denied. Useful for testing a policy to ensure no legitimate clients are denied.

Evaluation rules are:

1. If a request matches at least one deny matcher – DENY.
2. Else, if it matches at least one allow or allowWithShadowDeny matcher – ALLOW.
3. If no matchers apply – DENY (default).

Examples

Denying requests from a group of clients mesh-wide

During the incident, if one of the namespaces is compromised, Mesh Operator can apply the following policy:

apiVersion: kuma.io/v1alpha1
kind: MeshTrafficPermission
metadata:
  name: deny-malicious-ns
  namespace: kuma-system
  labels:
    kuma.io/mesh: my-mesh
spec:
  rules:
  - default:
      deny:
      - spiffeID:
          type: Prefix
          value: spiffe://my-mesh.us-east-2.mesh.local/ns/malicious

type: MeshTrafficPermission
name: deny-malicious-ns
mesh: my-mesh
spec:
  rules:
  - default:
      deny:
      - spiffeID:
          type: Prefix
          value: spiffe://my-mesh.us-east-2.mesh.local/ns/malicious

Such policy when applied globally prevents any service in the mesh my-mesh to receive requests from any client in malicious namespace. There is no way for Service Owner to opt-out from this rule.

Allowing requests from a group of clients mesh-wide

By default, when there are no MeshTrafficPermission policies, all requests are denied. Mesh Operator can apply the following policy mesh-wide:

apiVersion: kuma.io/v1alpha1
kind: MeshTrafficPermission
metadata:
  name: allow-observability-ns
  namespace: kuma-system
  labels:
    kuma.io/mesh: my-mesh
spec:
  rules:
  - default:
      allow:
      - spiffeID:
          type: Prefix
          value: spiffe://my-mesh.us-east-2.mesh.local/ns/observability

type: MeshTrafficPermission
name: allow-observability-ns
mesh: my-mesh
spec:
  rules:
  - default:
      allow:
      - spiffeID:
          type: Prefix
          value: spiffe://my-mesh.us-east-2.mesh.local/ns/observability

This policy allows any client in observability namespace to consume any service in my-mesh. Service Owner can opt-out and deny requests from observability if they need to:

apiVersion: kuma.io/v1alpha1
kind: MeshTrafficPermission
metadata:
  name: deny-observability-ns
  namespace: backend-ns
  labels:
    kuma.io/mesh: my-mesh
spec:
  targetRef:
    kind: Dataplane
    labels:
      app: backend
    sectionName: backend-admin-api
  rules:
  - default:
      deny:
      - spiffeID:
          type: Prefix
          value: spiffe://my-mesh.us-east-2.mesh.local/ns/observability

type: MeshTrafficPermission
name: deny-observability-ns
mesh: my-mesh
spec:
  targetRef:
    kind: Dataplane
    labels:
      app: backend
    sectionName: backend-admin-api
  rules:
  - default:
      deny:
      - spiffeID:
          type: Prefix
          value: spiffe://my-mesh.us-east-2.mesh.local/ns/observability

The following policy overrides the rules specified in allow-observability-ns and denies requests from clients in observability namespace on backend-admin-api port of backend app.

All policy options