Istio Ambient Waypoint Authorization

Configure L7 AuthorizationPolicy in Istio Ambient mode using waypoint proxies.

Table of Contents

• Overview
• Architecture
• Waypoint Gateway Configuration
• Service Configuration
• AuthorizationPolicy with targetRefs
• Complete Example
• Troubleshooting

Overview

In Istio Ambient mode:

• ztunnel: Handles L4 traffic (TCP, mTLS) - cannot evaluate HTTP paths
• Waypoint: Handles L7 traffic (HTTP) - can evaluate paths, methods, headers

To enforce path-based authorization, you need a waypoint proxy.

Architecture

Client -> ztunnel (L4 mTLS) -> Waypoint (L7 HTTP) -> Service
                                    |
                              AuthorizationPolicy
                              (evaluates path, method)

Waypoint Gateway Configuration

Create a waypoint for the service that needs L7 authorization:

apiVersion: gateway.networking.k8s.io/v1
kind: Gateway
metadata:
  name: mlflow-waypoint
  namespace: rossoctl-system
  labels:
    istio.io/waypoint-for: service
spec:
  gatewayClassName: istio-waypoint
  listeners:
    - name: mesh
      port: 15008
      protocol: HBONE

Key points:

• istio.io/waypoint-for: service - This waypoint handles service traffic
• gatewayClassName: istio-waypoint - Uses the Istio waypoint class
• Port 15008 with HBONE protocol is standard for waypoints

Service Configuration

Label the service to use the waypoint:

apiVersion: v1
kind: Service
metadata:
  name: mlflow
  namespace: rossoctl-system
  labels:
    istio.io/use-waypoint: mlflow-waypoint
spec:
  ports:
    - port: 5000
  selector:
    app: mlflow

AuthorizationPolicy with targetRefs

In Ambient mode, use targetRefs instead of selector:

apiVersion: security.istio.io/v1
kind: AuthorizationPolicy
metadata:
  name: mlflow-traces-from-otel
  namespace: rossoctl-system
spec:
  targetRefs:
    - kind: Service
      group: ""
      name: mlflow
  action: ALLOW
  rules:
    - from:
        - source:
            principals:
              - "cluster.local/ns/rossoctl-system/sa/otel-collector"
      to:
        - operation:
            methods: ["POST"]
            paths: ["/v1/traces"]

Key points:

• targetRefs points to the Service, not a selector
• group: "" is required for core Kubernetes resources
• principals uses SPIFFE ID format

Multiple Rules Example

Allow different sources for different paths:

apiVersion: security.istio.io/v1
kind: AuthorizationPolicy
metadata:
  name: mlflow-api-access
  namespace: rossoctl-system
spec:
  targetRefs:
    - kind: Service
      group: ""
      name: mlflow
  action: ALLOW
  rules:
    # OTEL collector can POST traces
    - from:
        - source:
            principals:
              - "cluster.local/ns/rossoctl-system/sa/otel-collector"
      to:
        - operation:
            methods: ["POST"]
            paths: ["/v1/traces"]

    # UI can access all endpoints
    - from:
        - source:
            principals:
              - "cluster.local/ns/rossoctl-system/sa/rossoctl-ui"
      to:
        - operation:
            methods: ["GET", "POST"]
            paths: ["/*"]

Complete Example

Full configuration for MLflow with OAuth2 and Istio authorization:

---
# Waypoint Gateway
apiVersion: gateway.networking.k8s.io/v1
kind: Gateway
metadata:
  name: mlflow-waypoint
  namespace: rossoctl-system
  labels:
    istio.io/waypoint-for: service
spec:
  gatewayClassName: istio-waypoint
  listeners:
    - name: mesh
      port: 15008
      protocol: HBONE
---
# Service with waypoint label
apiVersion: v1
kind: Service
metadata:
  name: mlflow
  namespace: rossoctl-system
  labels:
    istio.io/use-waypoint: mlflow-waypoint
spec:
  ports:
    - port: 5000
  selector:
    app: mlflow
---
# Authorization Policy
apiVersion: security.istio.io/v1
kind: AuthorizationPolicy
metadata:
  name: mlflow-traces-from-otel
  namespace: rossoctl-system
spec:
  targetRefs:
    - kind: Service
      group: ""
      name: mlflow
  action: ALLOW
  rules:
    - from:
        - source:
            principals:
              - "cluster.local/ns/rossoctl-system/sa/otel-collector"
      to:
        - operation:
            methods: ["POST"]
            paths: ["/v1/traces"]

Troubleshooting

Authorization Denied

1. Check waypoint is running:

kubectl get pods -n rossoctl-system -l gateway.networking.k8s.io/gateway-name=mlflow-waypoint

2. Check service has waypoint label:

kubectl get svc mlflow -n rossoctl-system -o yaml | grep waypoint

3. Check principal format:

istioctl proxy-config secret <pod> -n rossoctl-system

Waypoint Not Processing Traffic

1. Verify ambient mode is enabled:

kubectl get namespace rossoctl-system -o yaml | grep ambient

2. Check ztunnel logs:

kubectl logs -n istio-system -l app=ztunnel

Policy Not Evaluated

1. Ensure targetRefs is used (not selector)
2. Verify group: "" for core resources
3. Check policy is in same namespace as service

Sidecar vs Ambient

Feature	Sidecar Mode	Ambient Mode
AuthorizationPolicy target	selector	targetRefs
L7 processing	Automatic	Requires waypoint
Resource overhead	Per-pod sidecar	Shared waypoint

Related Skills

• auth:keycloak-confidential-client
• auth:otel-oauth2-exporter