This deployment is designed for a hostile public internet environment. We assume:

• Perimeter Scans: Automated bots will scan ports 80/443 continuously.
• Credential Stuffing: Attackers will attempt to use breached credentials.
• Container Breakout: A theoretical risk we mitigate via hardening.

We use Docker network isolation to create "air gaps":

• Ingress Layer: Handles TLS termination and request validation.
• Data Layer: internal: true flag prevents the Database and Redis from accessing the internet.

• No New Privileges: security_opt: [no-new-privileges:true] is set on ALL containers. This prevents a compromised process from gaining more privileges (e.g., via sudo or setuid binaries) even if the user is root inside the container.
• ReadOnly Mounts: Sensitive directories are mounted read-only where applicable. The ingress proxy has no direct filesystem access to Nextcloud application or data files.

The bundled Caddy configuration enforces:

• HSTS Preload: Forces browsers to use HTTPS for the domain.
• Permissions Policy: Disables browser API features (Camera, Mic) unless explicitly trusted.
• Path Traversal Blocking: Explicit denial of hidden paths like /.git, /build, or sensitive Nextcloud data.

• Account Security: The setup mandates strong admin passwords during initialization.
• Brute Force Protection: Nextcloud's built-in throttling is effective when configured with Redis (included).

Secrets (DB passwords, Redis passwords) are injected via a .env file at runtime.

• Risk Profile: Acceptable for single-tenant VPS where file permissions (600 on .env) are strictly enforced.
• Mitigation: The .env file is excluded from git (.gitignore).
• Future Path: For multi-node swarms, migration to Docker Secrets (mounted as files in /run/secrets) is the standard upgrade path.

Note: Redis authentication is configured via command-line arguments, which may be visible via container inspection. This is acceptable for a single-tenant VPS but would be replaced with file-based secrets in multi-tenant environments.