Add NGF permissions document

content/ngf/reference/permissions.md

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+---
+title: Permissions
+description: NGINX Gateway Fabric permissions required by components.
+weight: 300
+toc: true
+type: reference
+product: NGF
+---
+
+## Overview
+
+NGINX Gateway Fabric uses a split-plane architecture with three components that require different permissions:
+
+- **Control Plane**: Manages Kubernetes APIs and data plane deployments. Needs broad API access but handles no user traffic.
+- **Data Plane**: Processes user traffic. Requires minimal permissions since configuration comes from control plane via secure gRPC.
+- **Certificate Generator**: One-time job that creates TLS certificates for inter-plane communication.
+
+## Security Context
+
+All components share these security settings:
+
+- **User ID**: 101 (non-root)
+- **Group ID**: 1001  
+- **Capabilities**: All dropped (`drop: ALL`)
+- **Root Filesystem**: Read-only except for specific writable volumes
+- **Seccomp**: Runtime default profile
+
+## Control Plane
+
+Runs as a single container in the `nginx-gateway` deployment.
+
+**Additional Security Settings:**
+- **Privilege Escalation**: Disabled
+
+**Volumes:**
+- Secret mounts for TLS certificates
+
+**RBAC Permissions:**
+- **Secrets, ConfigMaps, Services**: Create, update, delete, list, get, watch
+- **Deployments, DaemonSets**: Create, update, delete, list, get, watch
+- **ServiceAccounts**: Create, update, delete, list, get, watch
+- **Namespaces, Pods**: Get, list, watch
+- **Events**: Create, patch
+- **EndpointSlices**: List, watch
+- **Gateway API resources**: List, watch (read-only) + update status subresources only
+- **NGF Custom resources**: Get, list, watch (read-only) + update status subresources only
+- **Leases**: Create, get, update (for leader election)
+- **CustomResourceDefinitions**: List, watch
+- **TokenReviews**: Create (for authentication)
+
+## Data Plane
+
+NGINX containers managed by the control plane. No RBAC permissions needed since configuration comes via secure gRPC.
+
+**Additional Security Settings:**
+- **Privilege Escalation**: Disabled
+- **Sysctl**: `net.ipv4.ip_unprivileged_port_start=0` (enables binding to ports < 1024)
+
+**Volumes:**
+- EmptyDir volumes for NGINX configuration, runtime files, logs, and cache
+- Secret mounts for TLS certificates
+- Projected token mounts for service account authentication
+
+**Volume Permissions:**
+- **EmptyDir**: Read-write (required for NGINX operation)
+- **Secret/ConfigMap/Projected**: Read-only
+
+## Certificate Generator
+
+Kubernetes Job that creates initial TLS certificates.
+
+**RBAC Permissions:**
+- **Secrets**: Create, update, get (control plane namespace only)
+
+## Platform-Specific Considerations
+
+### OpenShift Compatibility
+
+NGINX Gateway Fabric includes Security Context Constraints (SCCs) for OpenShift:
+
+**Control Plane SCC:**
+- **Privilege Escalation**: Disabled
+- **Host Access**: Disabled (network, IPC, PID, ports)
+- **User ID Range**: 101-101 (fixed)
+- **Group ID Range**: 1001-1001 (fixed)
+- **Volumes**: Secret only
+
+**Data Plane SCC:**
+Same restrictions as control plane, plus additional volume types:
+- **Additional Volumes**: EmptyDir, ConfigMap, Projected
+
+### Linux Capabilities
+
+NGINX Gateway Fabric drops ALL Linux capabilities and adds none, following security best practices.
+
+**How It Works Without Capabilities:**
+- **Process Management**: Standard Unix signals (no elevated privileges needed)
+- **Port Binding**: Uses sysctl `net.ipv4.ip_unprivileged_port_start=0` for ports < 1024
+- **File Operations**: Volume mounts provide necessary write access
+
+
+## Security Features
+
+- **Separation of concerns**: Control plane (API access, no traffic) vs data plane (traffic, no API access)
+- **Non-root execution**: All components run as unprivileged user (UID 101)
+- **Zero capabilities**: All Linux capabilities dropped
+- **Read-only root filesystem**: Prevents runtime modifications
+- **Ephemeral storage**: Temporary volumes only, no persistent storage
+- **Least privilege RBAC**: Minimal required permissions per component
+- **Secure communication**: mTLS-encrypted gRPC (TLS 1.3+) between planes