# Offline Bundle Format (.stella.bundle.tgz)

> Sprint: SPRINT_3603_0001_0001  
> Module: ExportCenter

This document describes the `.stella.bundle.tgz` format for portable, signed, verifiable evidence packages.

## Overview

The offline bundle is a self-contained archive containing all evidence and artifacts needed for offline triage of security findings. Bundles are:

- **Portable**: Single file that can be transferred to air-gapped environments
- **Signed**: DSSE-signed manifest for authenticity verification
- **Verifiable**: Content-addressable with SHA-256 hashes for integrity
- **Complete**: Contains all data needed for offline decision-making

## File Format

```
{alert-id}.stella.bundle.tgz
├── manifest.json                    # Bundle manifest (DSSE-signed)
├── metadata/
│   ├── alert.json                   # Alert metadata snapshot
│   └── generation-info.json         # Bundle generation metadata
├── evidence/
│   ├── reachability-proof.json      # Call-graph reachability evidence
│   ├── callstack.json               # Exploitability call stacks
│   └── provenance.json              # Build provenance attestations
├── vex/
│   ├── decisions.ndjson             # VEX decision history (NDJSON)
│   └── current-status.json          # Current VEX status
├── sbom/
│   ├── current.cdx.json             # Current SBOM slice (CycloneDX)
│   └── baseline.cdx.json            # Baseline SBOM for diff
├── diff/
│   └── sbom-delta.json              # SBOM delta changes
└── attestations/
    ├── bundle.dsse.json             # DSSE envelope for bundle
    └── evidence.dsse.json           # Evidence attestation chain
```

## Manifest Schema

The `manifest.json` file follows this schema:

```json
{
  "bundle_format_version": "1.0.0",
  "bundle_id": "abc123def456...",
  "alert_id": "alert-789",
  "created_at": "2024-12-15T10:00:00Z",
  "created_by": "user@example.com",
  "stellaops_version": "1.5.0",
  "entries": [
    {
      "path": "metadata/alert.json",
      "hash": "sha256:...",
      "size": 1234,
      "content_type": "application/json"
    }
  ],
  "root_hash": "sha256:...",
  "signature": {
    "algorithm": "ES256",
    "key_id": "signing-key-001",
    "value": "..."
  }
}
```

### Manifest Fields

| Field | Type | Required | Description |
|-------|------|----------|-------------|
| `bundle_format_version` | string | Yes | Format version (semver) |
| `bundle_id` | string | Yes | Unique bundle identifier |
| `alert_id` | string | Yes | Source alert identifier |
| `created_at` | ISO 8601 | Yes | Bundle creation timestamp (UTC) |
| `created_by` | string | Yes | Actor who created the bundle |
| `stellaops_version` | string | Yes | StellaOps version that created bundle |
| `entries` | array | Yes | List of content entries with hashes |
| `root_hash` | string | Yes | Merkle root of all entry hashes |
| `signature` | object | No | DSSE signature (if signed) |

## Entry Schema

Each entry in the manifest:

```json
{
  "path": "evidence/reachability-proof.json",
  "hash": "sha256:abc123...",
  "size": 2048,
  "content_type": "application/json",
  "compression": null
}
```

## DSSE Signing

Bundles support DSSE (Dead Simple Signing Envelope) signing:

```json
{
  "payloadType": "application/vnd.stellaops.bundle.manifest+json",
  "payload": "<base64-encoded manifest>",
  "signatures": [
    {
      "keyid": "signing-key-001",
      "sig": "<base64-encoded signature>"
    }
  ]
}
```

## Creation

### API Endpoint

```http
GET /v1/alerts/{alertId}/bundle
Authorization: Bearer <token>

Response: application/gzip
Content-Disposition: attachment; filename="alert-123.stella.bundle.tgz"
```

### Programmatic

```csharp
var packager = services.GetRequiredService<IOfflineBundlePackager>();

var result = await packager.CreateBundleAsync(new BundleRequest
{
    AlertId = "alert-123",
    ActorId = "user@example.com",
    IncludeVexHistory = true,
    IncludeSbomSlice = true
});

// result.Content contains the tarball stream
// result.ManifestHash contains the verification hash
```

## Verification

### API Endpoint

```http
POST /v1/alerts/{alertId}/bundle/verify
Content-Type: application/json

{
  "bundle_hash": "sha256:abc123...",
  "signature": "<optional DSSE signature>"
}

Response:
{
  "is_valid": true,
  "hash_valid": true,
  "chain_valid": true,
  "signature_valid": true,
  "verified_at": "2024-12-15T10:00:00Z"
}
```

### Programmatic

```csharp
var verification = await packager.VerifyBundleAsync(
    bundlePath: "/path/to/bundle.stella.bundle.tgz",
    expectedHash: "sha256:abc123...");

if (!verification.IsValid)
{
    Console.WriteLine($"Verification failed: {string.Join(", ", verification.Errors)}");
}
```

## CLI Usage

```bash
# Export bundle
stellaops alert bundle export --alert-id alert-123 --output ./bundles/

# Verify bundle
stellaops alert bundle verify --file ./bundles/alert-123.stella.bundle.tgz

# Import bundle (air-gapped instance)
stellaops alert bundle import --file ./bundles/alert-123.stella.bundle.tgz
```

## Security Considerations

1. **Hash Verification**: Always verify bundle hash before processing
2. **Signature Validation**: Verify DSSE signature if present
3. **Content Validation**: Validate JSON schemas after extraction
4. **Size Limits**: Enforce maximum bundle size limits (default: 100MB)
5. **Path Traversal**: Tarball extraction must prevent path traversal attacks

## Versioning

| Format Version | Changes | Min StellaOps Version |
|----------------|---------|----------------------|
| 1.0.0 | Initial format | 1.0.0 |

## Related Documentation

- [Evidence Bundle Envelope](./evidence-bundle-envelope.md)
- [DSSE Signing Guide](./dsse-signing.md)
- [Offline Kit Guide](../10_OFFLINE_KIT.md)
- [API Reference](../api/evidence-decision-api.openapi.yaml)