Example Architecture - RBAC outline - Mastering Security By Design

This section presents a role-based access control (RBAC) example for a fictitious system, “SkyLink API Gateway”.

It illustrates how an RBAC design can be developed and applied within a real-world system context, providing a practical reference for implementing authorisation controls as part of a Security by Design approach.

Overview¶

SkyLink implements Role-Based Access Control (RBAC) following the Security by Design principle of Least Privilege. Each role has only the minimum permissions required for its function.

Roles¶

Role	Description	Use Case
`aircraft_standard`	Default aircraft role	Basic operations (weather, telemetry write)
`aircraft_premium`	Premium aircraft	Extended access (+ contacts)
`ground_control`	Ground control station	Monitoring operations (read-only)
`maintenance`	Maintenance personnel	Diagnostic access
`admin`	System administrator	Full access

Permissions¶

Permission	Description	Resources
`weather:read`	Access weather data	GET /weather/current
`contacts:read`	Access contacts data	GET /contacts/
`telemetry:write`	Ingest telemetry	POST /telemetry/ingest
`telemetry:read`	Read telemetry	GET /telemetry/events/*
`config:read`	Read configuration	Future endpoint
`config:write`	Modify configuration	Future endpoint
`audit:read`	Read audit logs	Future endpoint

Role-Permission Matrix¶

Role	weather:read	contacts:read	telemetry:write	telemetry:read	config:read	config:write	audit:read
aircraft_standard	✅	❌	✅	❌	❌	❌	❌
aircraft_premium	✅	✅	✅	❌	❌	❌	❌
ground_control	✅	✅	❌	✅	❌	❌	❌
maintenance	✅	❌	✅	✅	✅	❌	❌
admin	✅	✅	✅	✅	✅	✅	✅

Usage¶

Requesting a Token with Role¶

# Default role (aircraft_standard)
curl -X POST http://localhost:8000/auth/token \
  -H "Content-Type: application/json" \
  -d '{"aircraft_id": "550e8400-e29b-41d4-a716-446655440000"}'

# With specific role
curl -X POST http://localhost:8000/auth/token \
  -H "Content-Type: application/json" \
  -d '{
    "aircraft_id": "550e8400-e29b-41d4-a716-446655440000",
    "role": "aircraft_premium"
  }'

JWT Token Structure¶

The JWT token includes the role in its claims:

{
  "sub": "550e8400-e29b-41d4-a716-446655440000",
  "aud": "skylink",
  "iat": 1703174400,
  "exp": 1703175300,
  "role": "aircraft_premium"
}

Error Responses¶

401 Unauthorized¶

Missing or invalid JWT token.

{
  "detail": "Missing Authorization header"
}

403 Forbidden¶

Valid token but insufficient permissions.

{
  "detail": "Permission denied: contacts:read required"
}

Implementation¶

Adding RBAC to an Endpoint¶

from fastapi import APIRouter, Depends
from skylink.rbac import require_permission
from skylink.rbac_roles import Permission

router = APIRouter()

@router.get("/protected")
async def protected_endpoint(
    token: dict = Depends(require_permission(Permission.WEATHER_READ))
):
    # Token is verified and has required permission
    return {"message": "Access granted"}

Checking Multiple Permissions¶

@router.get("/multi-protected")
async def multi_protected(
    token: dict = Depends(require_permission(
        Permission.TELEMETRY_READ,
        Permission.CONFIG_READ
    ))
):
    # Requires BOTH permissions
    return {"message": "Access granted"}

Role-Based Restriction¶

from skylink.rbac import require_role
from skylink.rbac_roles import Role

@router.get("/admin-only")
async def admin_only(
    token: dict = Depends(require_role(Role.ADMIN))
):
    # Only admin role allowed
    return {"message": "Admin access granted"}

Audit Logging¶

All authorization decisions are logged for security audit:

Authorization Success¶

{
  "event_type": "AUTHZ_SUCCESS",
  "event_category": "authorization",
  "severity": "info",
  "actor": {"type": "aircraft", "id": "550e8400..."},
  "details": {
    "role": "aircraft_premium",
    "permission": "contacts:read",
    "endpoint": "/contacts/"
  }
}

Authorization Failure¶

{
  "event_type": "AUTHZ_FAILURE",
  "event_category": "authorization",
  "severity": "warning",
  "actor": {"type": "aircraft", "id": "550e8400..."},
  "details": {
    "role": "aircraft_standard",
    "required_permission": "contacts:read",
    "endpoint": "/contacts/"
  }
}

Security Considerations¶

Default Role: Tokens without explicit role default to aircraft_standard (least privilege).
Invalid Roles: Invalid role values in tokens fall back to aircraft_standard.
Role in Token: Role is embedded in JWT, preventing runtime escalation.
No Role Enumeration: 403 responses don’t reveal which roles would have access.
Authentication vs Authorization:
- 401 = Authentication failure (no/invalid token)
- 403 = Authorization failure (valid token, wrong permissions)

Future Enhancements¶

Role hierarchy (inheritance)
Dynamic role assignment from database
Time-based permissions
Scope-based access (e.g., specific aircraft only)