Introduction

Istio AuthorizationPolicy denies all traffic when rules are too restrictive or misconfigured. This guide provides step-by-step diagnosis and resolution with specific commands and configuration examples.

Symptoms

Typical symptoms and error messages when this issue occurs:

bash
HTTP 403 Forbidden
RBAC: access denied
AuthorizationPolicy denied request

Observable indicators: - Service mesh proxy logs show configuration errors - Control plane reports validation failures - Traffic routing does not match expected behavior

Common Causes

  1. 1.Authorization failures occur when:
  2. 2.AuthorizationPolicy rules are too restrictive
  3. 3.Source or operation conditions do not match
  4. 4.Missing ALLOW policy for legitimate traffic
  5. 5.Policy applied to wrong namespace or workload

Step-by-Step Fix

Step 1: Check Current State

bash
istioctl analyze

Step 2: Identify Root Cause

bash
kubectl get virtualservice,destinationrule,gateway -A

Step 3: Apply Primary Fix

yaml
# Create ALLOW policy for specific service
apiVersion: security.istio.io/v1beta1
kind: AuthorizationPolicy
metadata:
  name: allow-my-service
  namespace: my-namespace
spec:
  selector:
    matchLabels:
      app: my-service
  action: ALLOW
  rules:
  - from:
    - source:
        principals: ["cluster.local/ns/other-ns/sa/other-service"]
    to:
    - operation:
        methods: ["GET", "POST"]
        paths: ["/api/*"]

Apply this configuration:

bash
kubectl apply -f virtualservice.yaml

Step 4: Apply Alternative Fix (If Needed)

```bash # Verify configuration istioctl analyze

# Check proxy status istioctl proxy-status

# View effective configuration istioctl proxy-config all <pod-name> ```

Step 5: Verify the Fix

After applying the fix, verify with:

bash
istioctl analyze && kubectl exec <pod> -c istio-proxy -- curl -s localhost:15000/ready

Expected output should show healthy proxies and correct routing.

Common Pitfalls

  • VirtualService hosts not matching Gateway servers
  • DestinationRule subset labels not matching pod labels
  • TLS Secret in wrong namespace
  • Missing Gateway binding in VirtualService

Best Practices

  • Use istioctl analyze before applying changes
  • Label services with version for subset routing
  • Keep VirtualService and DestinationRule in same namespace as service
  • Use ServiceEntry for external services
  • Istio Gateway TLS Secret Missing
  • Istio Sidecar Injection Disabled
  • Istio Authorization Policy Deny All
  • Istio Circuit Breaker Issues