# Export Attestation Prep — PREP-EXPORT-ATTEST-74-001

Status: **Ready for implementation** (2025-11-20)
Owners: Attestation Bundle Guild · Exporter Service Guild
Scope: Produce deterministic attestation export bundles for air-gap/offline delivery, leveraging EvidenceLocker DSSE layout and orchestrator events.

## Dependencies
- EvidenceLocker packaging & DSSE conventions: `docs/modules/evidence-locker/bundle-packaging.md`.
- Attestor air-gap guidance: `docs/modules/attestor/airgap.md` (statement + predicate expectations).
- Orchestrator event envelopes (Wave 150/140) for optional timeline/notification mirrors; not required to start packaging.

## Export bundle contract (v1)
- **Input**: attestation record id (`attestationId`) referencing a sealed DSSE statement (e.g., in-toto) stored by EvidenceLocker/Attestor.
- **Packaging**: create deterministic gzip/tar `export-attestation-bundle-v1.tgz` with fixed mtime `2025-01-01T00:00:00Z`, PAX headers, `0644` perms, owner/group `0`.
```
export-attestation-bundle-v1.tgz
├── attestation.dsse.json    # Original DSSE envelope (statement + signature), unchanged
├── statement.json           # Extracted statement/predicate for quick inspection
├── transparency.ndjson      # Optional Rekor/CT entries (one per line, canonical JSON)
├── metadata.json            # exportId, attestationId, subject digests, rootHash, createdAtUtc, sourceUri
├── checksums.txt            # SHA256 hashes (lexical order); first line `root <sha256(export-attestation-bundle-v1.tgz)>`
└── verify-attestation.sh    # POSIX script: checksum, DSSE verify (invokes `stella attest verify` if available)
```
- No re-signing; DSSE envelope is copied bit-for-bit from source.
- `transparency.ndjson` omitted when no log entries exist; maintain deterministic ordering otherwise.

## API surface (ExportCenter)
- `POST /v1/exports/attestations/{attestationId}` → `202 Accepted` with `exportId`, `status=pending`.
- `GET /v1/exports/attestations/{exportId}` → status + metadata (`rootHash`, `downloadUri`, `attestationDigests`).
- `GET /v1/exports/attestations/{exportId}/download` → `application/gzip`, filename `export-attestation-bundle-v1.tgz`, `ETag`=SHA256.
- Auth: `export:write` for POST, `export:read` for GET/Download; tenant scoped.

## Determinism & observability
- All timestamps captured once at export creation (UTC ISO-8601) and reused; archive mtimes/gzip mtime pinned.
- Structured log on completion `{exportId, attestationId, subjectDigests, rootHash}`; counter `export.attest.completed` and histogram `export.attest.duration_ms`.
- Retries for fetch/pack errors use exponential backoff identical to 57-001 portable export.

## Acceptance criteria
- Export archive is byte-identical across replays for the same (`attestationId`,`exportId`).
- DSSE envelope and statement are unchanged relative to source; hashes in `checksums.txt` match download and DSSE payload.
- API responses document 202/404/409/500 paths; `downloadUri` returns sealed artifact with deterministic ETag.
- Verification script runs offline using only `tar` + `sha256sum`/`shasum`; optionally calls `stella attest verify` when present.

## Open items / risks
- Notification/timeline emission pending envelope schema; add once Wave 150/140 lands.
- If attestation format changes (predicate versions), bump `statementVersion` in `metadata.json` and announce.

## Handoff
- Implement in `StellaOps.ExportCenter.Worker` export job + WebService endpoints above.
- Link this document from Sprint 0162 entry P6 and close PREP when endpoints + packaging align.