# Sealed Mode Contract (AIRGAP-57)

**Contract ID:** `CONTRACT-SEALED-MODE-004`
**Version:** 1.0
**Status:** Published
**Last Updated:** 2025-12-05

## Overview

This contract defines the sealed-mode operation contract for air-gapped environments. It covers sealing/unsealing state transitions, staleness detection, time anchoring, and egress policy enforcement.

## Implementation References

- **Controller:** `src/AirGap/StellaOps.AirGap.Controller/`
- **Time:** `src/AirGap/StellaOps.AirGap.Time/`
- **Policy:** `src/AirGap/StellaOps.AirGap.Policy/`
- **Documentation:** `docs/airgap/sealing-and-egress.md`, `docs/airgap/staleness-and-time.md`

## Data Models

### AirGapState

The core sealed-mode state model.

```csharp
public sealed record AirGapState
{
    public string Id { get; init; } = "singleton";
    public string TenantId { get; init; } = "default";
    public bool Sealed { get; init; } = false;
    public string? PolicyHash { get; init; } = null;
    public TimeAnchor TimeAnchor { get; init; } = TimeAnchor.Unknown;
    public DateTimeOffset LastTransitionAt { get; init; }
    public StalenessBudget StalenessBudget { get; init; } = StalenessBudget.Default;
}
```

### JSON Representation

```json
{
  "id": "singleton",
  "tenant_id": "default",
  "sealed": true,
  "policy_hash": "sha256:...",
  "time_anchor": {
    "anchor_time": "2025-12-05T10:00:00Z",
    "source": "roughtime",
    "format": "roughtime",
    "signature_fingerprint": "...",
    "token_digest": "sha256:..."
  },
  "last_transition_at": "2025-12-05T10:00:00Z",
  "staleness_budget": {
    "warning_seconds": 3600,
    "breach_seconds": 7200
  }
}
```

### TimeAnchor

Cryptographically verified time reference.

```json
{
  "anchor_time": "2025-12-05T10:00:00Z",
  "source": "roughtime|rfc3161",
  "format": "roughtime|rfc3161",
  "signature_fingerprint": "sha256:...",
  "token_digest": "sha256:..."
}
```

### StalenessBudget

Defines staleness thresholds.

```json
{
  "warning_seconds": 3600,
  "breach_seconds": 7200
}
```

| Field | Default | Description |
|-------|---------|-------------|
| `warning_seconds` | 3600 | Warning threshold (1 hour) |
| `breach_seconds` | 7200 | Breach threshold (2 hours) |

### StalenessEvaluation

Result of staleness calculation.

```json
{
  "age_seconds": 1800,
  "warning_seconds": 3600,
  "breach_seconds": 7200,
  "is_breached": false,
  "remaining_seconds": 1800
}
```

## API Endpoints

### Seal Environment

```
POST /system/airgap/seal
Content-Type: application/json
Authorization: Bearer <token with airgap:seal scope>

{
  "policy_hash": "sha256:...",
  "time_anchor": { ... },
  "staleness_budget": {
    "warning_seconds": 3600,
    "breach_seconds": 7200
  }
}

Response: 200 OK
{
  "sealed": true,
  "last_transition_at": "2025-12-05T10:00:00Z"
}
```

### Unseal Environment

```
POST /system/airgap/unseal
Authorization: Bearer <token with airgap:seal scope>

Response: 200 OK
{
  "sealed": false,
  "last_transition_at": "2025-12-05T10:00:00Z"
}
```

### Get Status

```
GET /system/airgap/status
Authorization: Bearer <token with airgap:status:read scope>

Response: 200 OK
{
  "sealed": true,
  "tenant_id": "default",
  "staleness": {
    "age_seconds": 1800,
    "is_breached": false,
    "remaining_seconds": 1800
  },
  "time_anchor": { ... },
  "policy_hash": "sha256:..."
}
```

### Verify Bundle

```
POST /system/airgap/verify
Content-Type: application/json
Authorization: Bearer <token with airgap:verify scope>

{
  "bundle_path": "/path/to/bundle.json",
  "trust_roots_path": "/path/to/trust-roots.json"
}

Response: 200 OK
{
  "valid": true,
  "verification_result": {
    "dsse_valid": true,
    "tuf_valid": true,
    "merkle_valid": true
  }
}
```

## Egress Policy

### EgressPolicy Model

```csharp
public sealed class EgressPolicy
{
    public EgressPolicyMode Mode { get; }  // Sealed | Unsealed
    public IReadOnlyList<string> AllowedHosts { get; }
    public bool PermitLoopback { get; }
    public bool PermitPrivateNetworks { get; }
}
```

### EgressRequest / EgressDecision

```json
// Request
{
  "component": "excititor",
  "destination": "https://api.github.com",
  "intent": "fetch_advisories",
  "operation": "GET"
}

// Decision
{
  "allowed": false,
  "reason": "AIRGAP_EGRESS_BLOCKED",
  "remediation": "Add api.github.com to allowlist or unseal environment"
}
```

### Enforcement

When sealed:
- All outbound connections blocked by default
- Only allowlisted destinations permitted
- Loopback and private networks optionally permitted

## Time Verification

### Roughtime Verification

1. Parse Roughtime response
2. Verify Ed25519 signature against trusted public key
3. Extract anchor time from signed response

### RFC 3161 Verification

1. Parse SignedCms structure
2. Validate TSA certificate chain
3. Extract signing time from timestamp token

## Startup Diagnostics

Pre-flight checks when starting in sealed mode:

1. Verify time anchor is present
2. Check staleness budget not breached
3. Validate trust roots are loaded
4. Confirm egress policy is enforced

```
GET /healthz/ready

Response: 200 OK (if healthy)
Response: 503 Service Unavailable (if sealed mode requirements unmet)
```

## Telemetry

### Metrics

| Metric | Type | Description |
|--------|------|-------------|
| `airgap_sealed` | gauge | 1 if sealed, 0 if unsealed |
| `airgap_anchor_drift_seconds` | gauge | Seconds since time anchor |
| `airgap_anchor_expiry_seconds` | gauge | Seconds until staleness breach |
| `airgap_seal_total` | counter | Total seal operations |
| `airgap_unseal_total` | counter | Total unseal operations |
| `airgap_startup_blocked_total` | counter | Blocked startup attempts |

### Structured Logging

```json
{
  "event": "airgap.sealed",
  "tenant_id": "default",
  "policy_hash": "sha256:...",
  "timestamp": "2025-12-05T10:00:00Z"
}
```

## Authority Scopes

| Scope | Description |
|-------|-------------|
| `airgap:seal` | Seal/unseal environment |
| `airgap:status:read` | Read sealed status |
| `airgap:verify` | Verify bundles |
| `airgap:import` | Import bundles |

## Unblocks

This contract unblocks the following tasks:

- POLICY-AIRGAP-57-001
- POLICY-AIRGAP-57-002
- POLICY-AIRGAP-58-001

## Related Contracts

- [Mirror Bundle Contract](./mirror-bundle.md) - Bundle format for sealed import
- [Verification Policy Contract](./verification-policy.md) - Attestation verification