scadalink-design/Component-Security.md

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.