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Service Account Token Volume Examples
=====================================

This document provides comprehensive examples for configuring Service Account Token Volumes
in the Apache Airflow Helm Chart. These examples demonstrate various security scenarios and
use cases for pod-launching executors.

Overview
--------

Service Account Token Volume configuration allows you to manually control how Kubernetes
service account tokens are mounted into pods launched by Airflow. This feature implements the
**Principle of Least Privilege** by providing tokens only to containers that require Kubernetes API access.

**Container-Specific Security Model:**

- **Scheduler Container**: Receives Service Account Token as it requires API access for pod management
- **Init Container**: No Service Account Token as it only performs database migrations
- **Sidecar Container**: No Service Account Token as it only performs log cleanup operations

**This feature is particularly useful for**:

- Compliance with security policies that restrict automatic token mounting
- Implementation of defense-in-depth security strategies
- Custom token expiration and audience configuration
- Compatibility with security policy engines like Kyverno
- Meeting compliance frameworks that mandate container-specific privilege assignment

Basic Configuration Examples
----------------------------

Default Automatic Token Mounting
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

This is the default behavior that continues to work without any changes:

.. code-block:: yaml
   :caption: values.yaml

   scheduler:
     serviceAccount:
       automountServiceAccountToken: true  # Default value

Manual Token Volume Configuration
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Basic manual configuration that disables automatic mounting and enables manual token volume:

.. code-block:: yaml
   :caption: values.yaml

   scheduler:
     serviceAccount:
       automountServiceAccountToken: false
       serviceAccountTokenVolume:
         enabled: true

This configuration:

- Disables automatic service account token mounting at the ServiceAccount level
- Enables manual token volume mounting at the Pod level
- Uses default values for all other token volume settings

Security-Focused Examples
-------------------------

High-Security Environment
^^^^^^^^^^^^^^^^^^^^^^^^^

For environments requiring enhanced security with shorter token lifetimes:

.. code-block:: yaml
   :caption: values.yaml

   scheduler:
     serviceAccount:
       automountServiceAccountToken: false
       serviceAccountTokenVolume:
         enabled: true
         expirationSeconds: 1800  # 30 minutes instead of default 1 hour
         mountPath: /var/run/secrets/kubernetes.io/serviceaccount
         volumeName: secure-kube-access

**Security Benefits:**

- **Shorter token lifetime** reduces exposure window if compromised
- **Explicit control** over token mounting makes security intentional
- **Container isolation** as only scheduler container receives API access
- **Clear naming** for security auditing and compliance reporting

Kyverno Policy Compliance
^^^^^^^^^^^^^^^^^^^^^^^^^

Configuration that complies with Kyverno policies requiring ``automountServiceAccountToken: false``
(`Restrict Auto-Mount of Service Account Tokens in Service Account`_ and `Restrict Auto-Mount of Service Account Tokens`_):

.. _Restrict Auto-Mount of Service Account Tokens in Service Account: https://kyverno.io/policies/other/restrict-sa-automount-sa-token/restrict-sa-automount-sa-token/
.. _Restrict Auto-Mount of Service Account Tokens: https://kyverno.io/policies/other/restrict-sa-automount-sa-token/restrict-sa-automount-sa-token/

.. code-block:: yaml
   :caption: values.yaml

   scheduler:
     serviceAccount:
       automountServiceAccountToken: false  # Required by Kyverno policy
       serviceAccountTokenVolume:
         enabled: true
         expirationSeconds: 3600
         audience: "https://kubernetes.default.svc.cluster.local"

Custom Mount Path Configuration
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

For applications that expect service account tokens at custom locations:

.. code-block:: yaml
   :caption: values.yaml

   scheduler:
     serviceAccount:
       automountServiceAccountToken: false
       serviceAccountTokenVolume:
         enabled: true
         mountPath: /custom/sa-token
         volumeName: custom-service-account-token
         expirationSeconds: 7200  # 2 hours

This configuration mounts the token at ``/custom/sa-token`` instead of the default location.

Executor-Specific Examples
--------------------------

KubernetesExecutor Configuration
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Optimal configuration for ``KubernetesExecutor`` with security focus:

.. code-block:: yaml
   :caption: values.yaml

   executor: KubernetesExecutor

   scheduler:
     serviceAccount:
       automountServiceAccountToken: false
       serviceAccountTokenVolume:
         enabled: true
         expirationSeconds: 3600
         mountPath: /var/run/secrets/kubernetes.io/serviceaccount
         volumeName: k8s-executor-token

   # Ensure RBAC permissions for KubernetesExecutor
   rbac:
     create: true

Multi-Environment Examples
--------------------------

Development Environment
^^^^^^^^^^^^^^^^^^^^^^^

Relaxed configuration for development with longer token lifetimes:

.. code-block:: yaml
   :caption: values-dev.yaml

   scheduler:
     serviceAccount:
       automountServiceAccountToken: false
       serviceAccountTokenVolume:
         enabled: true
         expirationSeconds: 14400  # 4 hours for development convenience
         mountPath: /var/run/secrets/kubernetes.io/serviceaccount

Production Environment
^^^^^^^^^^^^^^^^^^^^^^

Strict production configuration with enhanced security:

.. code-block:: yaml
   :caption: values-prod.yaml

   # Additional production security settings
   securityContexts:
     pod:
       runAsNonRoot: true
       runAsUser: 50000
       fsGroup: 0
     container:
       allowPrivilegeEscalation: false
       readOnlyRootFilesystem: true
       runAsNonRoot: true

   scheduler:
     serviceAccount:
       automountServiceAccountToken: false
       serviceAccountTokenVolume:
         enabled: true
         expirationSeconds: 1800   # 30 minutes for production security
         audience: "https://kubernetes.default.svc.cluster.local"
         volumeName: prod-airflow-token

.. note::

   Remember that it is a good practice to have the production configuration on the test environment to ensure
   reliable testing before moving changes to production.

Migration Examples
------------------

Gradual Migration from Automatic to Manual
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

1. Test manual configuration alongside automatic (for validation):

   .. code-block:: yaml
      :caption: values-test.yaml

      scheduler:
        serviceAccount:
          automountServiceAccountToken: true   # Keep automatic for now
          serviceAccountTokenVolume:
            enabled: false                     # Disable manual for testing

2. Enable manual configuration while keeping automatic (transition phase):

   .. code-block:: yaml
      :caption: values-transition.yaml

      scheduler:
        serviceAccount:
          automountServiceAccountToken: true   # Still automatic
          serviceAccountTokenVolume:
            enabled: true                      # Test manual mounting
            expirationSeconds: 3600

3. Complete migration to manual-only:

   .. code-block:: yaml
      :caption: values-final.yaml

      scheduler:
        serviceAccount:
          automountServiceAccountToken: false  # Disable automatic
          serviceAccountTokenVolume:
            enabled: true                      # Use manual only
            expirationSeconds: 3600

Troubleshooting Examples
------------------------

Debug Configuration
^^^^^^^^^^^^^^^^^^^

Configuration with extended token lifetime for troubleshooting:

.. code-block:: yaml
   :caption: values-debug.yaml

   scheduler:
     serviceAccount:
       automountServiceAccountToken: false
       serviceAccountTokenVolume:
         enabled: true
         expirationSeconds: 86400  # 24 hours for debugging
         mountPath: /var/run/secrets/kubernetes.io/serviceaccount
         volumeName: debug-sa-token

   # Enable debug logging
   config:
     logging:
       logging_level: DEBUG

Validation Commands
^^^^^^^^^^^^^^^^^^^

Commands to validate the configuration is working correctly:

.. code-block:: bash

   # Check if the service account token is mounted correctly
   kubectl exec -it deployment/airflow-scheduler -- ls -la /var/run/secrets/kubernetes.io/serviceaccount/

   # Verify token content and expiration
   kubectl exec -it deployment/airflow-scheduler -- cat /var/run/secrets/kubernetes.io/serviceaccount/token | base64 -d

   # Check scheduler logs for authentication issues
   kubectl logs deployment/airflow-scheduler | grep -i "auth\|token\|permission"

   # Describe the scheduler pod to see volume mounts
   kubectl describe pod -l component=scheduler

Advanced Configuration Examples
-------------------------------

Custom Audience Configuration
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

For environments requiring specific token audiences:

.. code-block:: yaml
   :caption: values.yaml

   scheduler:
     serviceAccount:
       automountServiceAccountToken: false
       serviceAccountTokenVolume:
         enabled: true
         audience: "https://my-custom-api-server.example.com"
         expirationSeconds: 3600

Multi-Cluster Configuration
^^^^^^^^^^^^^^^^^^^^^^^^^^^

Configuration for multi-cluster deployments:

.. code-block:: yaml
   :caption: values-cluster-a.yaml

   scheduler:
     serviceAccount:
       automountServiceAccountToken: false
       serviceAccountTokenVolume:
         enabled: true
         audience: "https://cluster-a.k8s.example.com"
         volumeName: cluster-a-token
         expirationSeconds: 3600

Integration with External Security Tools
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Configuration compatible with external security scanning and policy tools:

.. code-block:: yaml
   :caption: values-security-compliant.yaml

   # Additional security annotations
   airflowPodAnnotations:
     security.policy/scanned: "true"
     security.policy/compliant: "service-account-token-manual"

   scheduler:
     serviceAccount:
       automountServiceAccountToken: false
       serviceAccountTokenVolume:
         enabled: true
         expirationSeconds: 1800  # Short-lived tokens
         mountPath: /var/run/secrets/kubernetes.io/serviceaccount
         volumeName: security-compliant-token

Best Practices Summary
----------------------

**Container Security:**

1. **Understand container roles**: Only the scheduler container requires Kubernetes API access
2. **Verify token isolation**: Ensure init and sidecar containers operate without service account tokens
3. **Implement least privilege**: Each container should receive only the minimum required permissions

**Configuration Management:**

1. **Always test** manual token configuration in non-production environments first
2. **Use shorter token lifetimes** around 1800-3600 seconds
3. **Set explicit audiences** when integrating with external systems
4. **Use descriptive volume names** for easier troubleshooting and security auditing

**Security Monitoring:**

1. **Monitor logs** for authentication issues after migration
2. **Document your configuration** for security auditing and compliance purposes
3. **Audit container permissions** regularly to ensure compliance with security policies
4. **Combine with other security measures** like Pod Security Standards and network policies

**Migration Strategy:**

1. **Plan gradual migration** from automatic to manual token mounting
2. **Validate functionality** of each container type after configuration changes
3. **Maintain backward compatibility** during transition periods

**Why This Approach is More Secure:**

1. **Reduced attack surface**: Containers without API access cannot be used to compromise the cluster
2. **Clear security boundaries**: Explicit definition of which containers have API privileges
3. **Compliance ready**: Meets requirements for container-specific privilege assignment
4. **Audit friendly**: Clear documentation of security controls for compliance reporting

For more detailed information, see the :doc:`production-guide` section on Service Account Token Volume Configuration.
