# Container isolation

How HexaHost GameCloud isolates Minecraft server workloads on game nodes.

## Model

Each customer server runs as a **non-privileged Docker container** on a dedicated game node. The node-agent creates and manages containers; customers never receive Docker socket access.

```
Control plane (trusted)  ──mTLS──►  Node agent (trusted)  ──►  Game container (untrusted)
```

## Container hardening (target profile)

| Control | Setting |
|---------|---------|
| User | Non-root UID inside container |
| Privileges | `--privileged=false` |
| Capabilities | Drop ALL, add only required (none for vanilla Java) |
| seccomp | Docker default or custom profile (Phase 2) |
| AppArmor | Docker default profile |
| Network | Bridge network per server; no `host` network mode |
| Read-only root | Where compatible with selected software family |
| Memory / CPU | cgroup limits from plan slug |
| PIDs limit | Prevents fork bombs |

## Network isolation

- Game containers reach the internet for Minecraft auth and mod downloads only through controlled egress
- No route to control plane PostgreSQL, Redis, or internal APIs
- Node-agent management port (`9100`) bound to localhost or management VLAN only

See threat T05 and T12 in [threat model](threat-model.md).

## Storage isolation

- Per-server data directory on node disk: `/var/lib/hgc-node/servers/{serverId}/`
- Path traversal prevented server-side; symlinks rejected on archive extract
- Backups uploaded to object storage — not readable by other tenants

## Image policy

- Only catalog-approved runtime images (digest-pinned)
- Customers cannot push custom images
- Periodic image vulnerability scan in CI (Phase 9)

## Multi-tenant on one node

The scheduler enforces RAM and server count limits per node. There is no shared filesystem between server containers except the read-only image layers.

## Operator responsibilities

| Task | Frequency |
|------|-----------|
| Docker security updates on nodes | Monthly |
| Review AppArmor/seccomp profiles after Minecraft/Java major bumps | Per release |
| Audit `docker ps` for unexpected privileged containers | Weekly |

Bootstrap hardening via `deploy/ansible/game-node.yml`.

## Verification

- Attempt cross-container network scan from test server (should fail to reach agent port)
- Confirm `docker inspect` shows `Privileged: false`
- Penetration test before production go-live

## Related

- [Threat model](threat-model.md)
- [Game node operations](../operations/game-node.md)
- [Secrets](secrets.md)