# Component: Security & Auth

## Purpose

The Security & Auth component handles user authentication via LDAP/Active Directory and enforces role-based authorization across the system. It maps LDAP group memberships to system roles and applies permission checks to all operations.

## Location

Central cluster. Sites do not have user-facing interfaces and do not perform independent authentication.

## Responsibilities

- Authenticate users against LDAP/Active Directory using Windows Integrated Authentication.
- Map LDAP group memberships to system roles.
- Enforce role-based access control on all API and UI operations.
- Support site-scoped permissions for the Deployment role.

## Authentication

- **Mechanism**: The Central UI presents a username/password login form. The app validates credentials by binding to the LDAP/AD server with the provided credentials, then queries the user's group memberships.
- **No local user store**: All identity and group information comes from AD. No credentials are cached locally.
- **No Windows Integrated Authentication**: The app authenticates directly against LDAP/AD, not via Kerberos/NTLM.

## Session Management

### JWT Tokens
- On successful authentication, the app issues a **JWT** signed with a shared symmetric key (HMAC-SHA256). Both central cluster nodes use the same signing key from configuration, so either node can issue and validate tokens.
- **JWT claims**: User display name, username, list of roles (Admin, Design, Deployment), and for site-scoped Deployment, the list of permitted site IDs. All authorization decisions are made from token claims without hitting the database.

### Token Lifecycle
- **JWT expiry**: 15 minutes. On each request, if the token is near expiry, the app re-queries LDAP for current group memberships and issues a fresh token with updated claims. Roles are never more than 15 minutes stale.
- **Idle timeout**: Configurable, default **30 minutes**. If no requests are made within the idle window, the token is not refreshed and the user must re-login. Tracked via a last-activity timestamp in the token.
- **Sliding refresh**: Active users stay logged in indefinitely — the token refreshes every 15 minutes as long as requests are made within the 30-minute idle window.

### Load Balancer Compatibility
- JWT tokens are self-contained — no server-side session state. A load balancer in front of the central cluster can route requests to either node without sticky sessions or a shared session store. Central failover is transparent to users with valid tokens.

## LDAP Connection Failure

- **New logins**: If the LDAP/AD server is unreachable, login attempts **fail**. Users cannot be authenticated without LDAP.
- **Active sessions**: Users with valid (not-yet-expired) JWTs can **continue operating** with their current roles. The token refresh is skipped until LDAP is available again. This avoids disrupting engineers mid-work during a brief LDAP outage.
- **Recovery**: When LDAP becomes reachable again, the next token refresh cycle re-queries group memberships and issues a fresh token with current roles.

## Roles

### Admin
- **Scope**: System-wide (always).
- **Permissions**:
  - Manage site definitions.
  - Manage site-level data connections (define and assign to sites).
  - Manage area definitions per site.
  - Manage LDAP group-to-role mappings.
  - Manage API keys (create, enable/disable, delete).
  - System-level configuration.
  - View audit logs.

### Design
- **Scope**: System-wide (always).
- **Permissions**:
  - Create, edit, delete templates (including attributes, alarms, scripts).
  - Manage shared scripts.
  - Manage external system definitions.
  - Manage database connection definitions.
  - Manage notification lists and SMTP configuration.
  - Manage inbound API method definitions.
  - Run on-demand validation (template flattening, script compilation).

### Deployment
- **Scope**: System-wide or site-scoped.
- **Permissions**:
  - Create and manage instances (overrides, connection bindings, area assignment).
  - Disable, enable, and delete instances.
  - Deploy configurations to instances.
  - Deploy system-wide artifacts (shared scripts, external system definitions, DB connections, notification lists) to all sites.
  - View deployment diffs and status.
  - Use debug view.
  - Manage parked messages.
  - View site event logs.
- **Site scoping**: A user with site-scoped Deployment role can only perform these actions for instances at their permitted sites.

## Multi-Role Support

- A user can hold **multiple roles simultaneously** by being a member of multiple LDAP groups.
- Roles are **independent** — there is no implied hierarchy between roles.
- For example, a user who is a member of both `SCADA-Designers` and `SCADA-Deploy-All` holds both the Design and Deployment roles, allowing them to author templates and also deploy configurations.

## LDAP Group Mapping

- System administrators configure mappings between LDAP groups and roles.
- Examples:
  - `SCADA-Admins` → Admin role
  - `SCADA-Designers` → Design role
  - `SCADA-Deploy-All` → Deployment role (all sites)
  - `SCADA-Deploy-SiteA` → Deployment role (Site A only)
  - `SCADA-Deploy-SiteB` → Deployment role (Site B only)
- A user can be a member of multiple groups, granting multiple independent roles.
- Group mappings are stored in the configuration database and managed via the Central UI (Admin role).

## Permission Enforcement

- Every API endpoint and UI action checks the authenticated user's roles before proceeding.
- Site-scoped checks additionally verify the target site is within the user's permitted sites.
- Unauthorized actions return an appropriate error and are not logged as audit events (only successful changes are audited).

## Dependencies

- **Active Directory / LDAP**: Source of user identity and group memberships.
- **Configuration Database (MS SQL)**: Stores LDAP group-to-role mappings and site scoping rules.
- **Configuration Database (via IAuditService)**: Security/admin changes (role mapping updates) are audit logged.

## Interactions

- **Central UI**: All UI requests pass through authentication and authorization.
- **Template Engine**: Design role enforcement.
- **Deployment Manager**: Deployment role enforcement with site scoping.
- **All central components**: Role checks are a cross-cutting concern applied at the API layer.