# AirGap Controller Scaffold (Draft) — PREP-AIRGAP-CTL-56-001/002/57-001/57-002/58-001

Status: Draft (2025-11-20)
Owners: AirGap Controller Guild · Observability Guild · AirGap Time Guild · DevOps Guild
Scope: Define the baseline project skeleton, APIs, telemetry, and staleness fields needed to unblock controller tasks 56-001 through 58-001.

## 1) Project layout
- Project: `src/AirGap/StellaOps.AirGap.Controller` (net10.0, minimal API host).
- Tests: `tests/AirGap/StellaOps.AirGap.Controller.Tests` with xunit + deterministic time provider.
- Shared contracts: DTOs under `Endpoints/Contracts`, domain state under `Domain/AirGapState.cs`.
- Persistence: in-memory store by default; Mongo store activates when `AirGap:Mongo:ConnectionString` is set.
- Tests: Mongo2Go-backed store tests live under `tests/AirGap`; see `tests/AirGap/README.md` for OpenSSL shim note.

## 2) State model
- Persistent document `airgap_state` (Mongo):
  - `id` (const `singleton`), `tenant_id`, `sealed` (bool), `policy_hash`, `time_anchor` (nullable), `last_transition_at` (UTC), `staleness_budget_seconds` (int?, optional per bundle), `notes`.
  - Index on `{tenant_id}`; unique on `singleton` within tenant.
- In-memory cache with monotonic timestamp to avoid stale reads; cache invalidated on transitions.

### Mongo wiring (opt‑in)
- Config section:

```json
"AirGap": {
  "Mongo": {
    "ConnectionString": "mongodb://localhost:27017",
    "Database": "stellaops_airgap",
    "Collection": "airgap_state"
  }
}
```

- The DI extension `AddAirGapController` chooses Mongo when `ConnectionString` is present; otherwise falls back to in-memory.
- Collection index: unique on `{tenant_id, id}` to enforce singleton per tenant.

## 3) Endpoints (56-002 baseline)
- `GET /system/airgap/status` → returns current state + staleness summary:
  - `{sealed, policy_hash, time_anchor:{source, anchored_at, drift_seconds}, staleness:{age_seconds, warning_seconds, breach_seconds, seconds_remaining}, last_transition_at}`.
- `POST /system/airgap/seal` → body `{policy_hash, time_anchor?, staleness_budget_seconds?}`; requires Authority scopes `airgap:seal` + `effective:write`.
- `POST /system/airgap/unseal` → requires `airgap:seal`.
- Validation: reject seal if missing `policy_hash` or time anchor when platform requires sealed mode.

## 4) Telemetry (57-002)
- Structured logs: `airgap.sealed`, `airgap.unsealed`, `airgap.status.read` with tenant_id, policy_hash, time_anchor_source, drift_seconds.
- Metrics (Prometheus/OpenTelemetry): counters `airgap_seal_total`, `airgap_unseal_total`, `airgap_startup_blocked_total`; gauges `airgap_time_anchor_age_seconds`, `airgap_staleness_budget_seconds`.
- Timeline events (Observability stream): `airgap.sealed`, `airgap.unsealed` with correlation_id.

### Startup diagnostics wiring (57-001)
- Config section `AirGap:Startup` now drives sealed-mode startup validation:
  - `TenantId` (default `default`).
  - `EgressAllowlist` (array; required when sealed).
  - `Trust:RootJsonPath`, `Trust:SnapshotJsonPath`, `Trust:TimestampJsonPath` (all required when sealed; parsed via TUF validator).
  - `Rotation:ActiveKeys`, `Rotation:PendingKeys`, `Rotation:ApproverIds` (base64-encoded keys; dual approval enforced when pending keys exist).
- Failures raise `sealed-startup-blocked:<reason>` and increment `airgap_startup_blocked_total{reason}`.

## 5) Staleness & time (58-001)
- Staleness computation: `drift_seconds = now_utc - time_anchor.anchored_at`; `seconds_remaining = max(0, staleness_budget_seconds - drift_seconds)`.
- Time anchors accept Roughtime or RFC3161 token parsed via AirGap Time component (imported service).
- Status response includes drift and remaining budget; sealed mode refuses to run if budget exceeded.

## 6) Determinism & offline rules
- No external network calls; time source injected `IClock` seeded in tests.
- All timestamps RFC3339 UTC; responses sorted properties (serializer config).

## 7) Open decisions
- Final scopes list (Authority) for status read vs seal/unseal.
- Whether to require dual authorization for `seal` (two-man rule) in sealed environments.
- Retention/rotation policy for `airgap_state` audit trail (append-only vs mutation).

## 8) Handoff
This document satisfies PREP-AIRGAP-CTL-56-001 through 58-001. Update once Authority scopes and time-anchor token format are finalized; then promote to v1 schema doc and wire tests accordingly.