# Evidence Pack Schema

> **Status:** Implementation in Progress (SPRINT_3000_0100_0002)
> **Type URI:** `https://stellaops.dev/evidence-pack@v1`
> **Schema:** [`docs/schemas/stellaops-evidence-pack.v1.schema.json`](../schemas/stellaops-evidence-pack.v1.schema.json)

---

## Overview

**Evidence Packs** are time-stamped, queryable bundles containing complete policy evaluation context (SBOM, advisories, VEX, policy, verdicts, reachability). They enable:

- **Deterministic Replay:** Re-evaluate policy with identical inputs
- **Audit & Compliance:** Portable evidence for incident review
- **Offline Transfer:** Move evidence between air-gapped environments
- **Forensics:** Query pack contents without external dependencies

---

## Pack Structure

Evidence packs are **compressed tarballs** (`.tar.gz`) with a signed manifest:

```
evidence-pack-{packId}.tar.gz
├── manifest.json                        # Signed manifest with content index
├── policy/
│   ├── policy-P-7-v4.json              # Policy definition snapshot
│   └── policy-run-{runId}.json         # Policy run request/status
├── sbom/
│   ├── sbom-S-42.spdx.json             # SBOM artifacts
│   └── sbom-S-318.spdx.json
├── advisories/
│   ├── nvd-2025-12345.json             # Advisory snapshots (timestamped)
│   ├── ghsa-2025-0001.json
│   └── cve-2025-99999.json
├── vex/
│   ├── vendor-vex-statement-1.json     # VEX statements (OpenVEX)
│   └── internal-vex-override-2.json
├── verdicts/
│   ├── verdict-finding-1.json          # Individual verdict attestations (DSSE)
│   ├── verdict-finding-2.json
│   └── ...
├── reachability/
│   ├── drift-{scanId}.json             # Reachability drift results
│   └── slices/
│       └── slice-{digest}.json         # Reachability slices
└── metadata/
    ├── tenant-context.json             # Tenant metadata
    ├── environment.json                # Environment context from policy run
    └── signatures.json                 # Detached signatures for pack contents
```

---

## Manifest Format

See [`stellaops-evidence-pack.v1.schema.json`](../schemas/stellaops-evidence-pack.v1.schema.json) for complete schema.

### Example Manifest

```json
{
  "_type": "https://stellaops.dev/evidence-pack@v1",
  "packId": "pack:run:P-7:20251223T140500Z:1b2c3d4e",
  "generatedAt": "2025-12-23T14:10:00+00:00",
  "tenantId": "tenant-alpha",
  "policyRunId": "run:P-7:20251223T140500Z:1b2c3d4e",
  "policyId": "P-7",
  "policyVersion": 4,
  "manifestVersion": "1.0.0",

  "contents": {
    "policy": [
      {
        "path": "policy/policy-P-7-v4.json",
        "digest": "sha256:abc123...",
        "size": 12345,
        "mediaType": "application/vnd.stellaops.policy+json"
      }
    ],
    "sbom": [
      {
        "path": "sbom/sbom-S-42.spdx.json",
        "digest": "sha256:sbom42...",
        "size": 234567,
        "mediaType": "application/spdx+json",
        "sbomId": "sbom:S-42"
      }
    ],
    "advisories": [
      {
        "path": "advisories/nvd-2025-12345.json",
        "digest": "sha256:adv123...",
        "size": 4567,
        "mediaType": "application/vnd.stellaops.advisory+json",
        "cveId": "CVE-2025-12345",
        "capturedAt": "2025-12-23T13:59:00+00:00"
      }
    ],
    "vex": [...],
    "verdicts": [...],
    "reachability": [...]
  },

  "statistics": {
    "totalFiles": 47,
    "totalSize": 5678901,
    "componentCount": 1742,
    "findingCount": 234,
    "verdictCount": 234,
    "advisoryCount": 89,
    "vexStatementCount": 12
  },

  "determinismHash": "sha256:pack-determinism...",
  "signatures": [
    {
      "keyId": "sha256:keypair123...",
      "algorithm": "ed25519",
      "signature": "base64-encoded-signature",
      "signedAt": "2025-12-23T14:10:05+00:00"
    }
  ]
}
```

---

## API Reference

### Create Evidence Pack

```http
POST /api/v1/runs/{runId}/evidence-pack
```

**Request:**
```json
{
  "includeReachability": true,
  "compression": "gzip"
}
```

**Response:**
```json
{
  "packId": "pack:run:P-7:20251223T140500Z:1b2c3d4e",
  "generatedAt": "2025-12-23T14:10:00+00:00",
  "downloadUri": "/api/v1/evidence-packs/pack:run:P-7:20251223T140500Z:1b2c3d4e",
  "manifestUri": "/api/v1/evidence-packs/pack:run:P-7:20251223T140500Z:1b2c3d4e/manifest",
  "packSize": 5678901,
  "statistics": {...}
}
```

### Download Evidence Pack

```http
GET /api/v1/evidence-packs/{packId}
Accept: application/gzip
```

**Response:** Binary tarball (`.tar.gz`)

### Inspect Manifest

```http
GET /api/v1/evidence-packs/{packId}/manifest
```

**Response:** JSON manifest (without downloading full pack)

### Replay Policy from Pack

```http
POST /api/v1/evidence-packs/{packId}/replay
```

**Response:**
```json
{
  "replayId": "replay:pack:...:20251223T150000Z",
  "packId": "pack:run:P-7:20251223T140500Z:1b2c3d4e",
  "originalRunId": "run:P-7:20251223T140500Z:1b2c3d4e",
  "determinismVerified": true,
  "verdictComparison": {
    "totalOriginal": 234,
    "totalReplay": 234,
    "identical": 234,
    "differences": []
  },
  "replayDuration": 45.2
}
```

### Verify Pack Integrity

```http
POST /api/v1/evidence-packs/{packId}/verify
```

**Response:**
```json
{
  "packId": "pack:run:P-7:20251223T140500Z:1b2c3d4e",
  "manifestSignatureValid": true,
  "contentIntegrityValid": true,
  "verifiedAt": "2025-12-23T15:00:00+00:00",
  "verifications": [
    {
      "file": "policy/policy-P-7-v4.json",
      "expectedDigest": "sha256:abc123...",
      "actualDigest": "sha256:abc123...",
      "valid": true
    },
    // ... all files
  ]
}
```

---

## CLI Usage

### Create Pack

```bash
stella pack create run:P-7:20251223T140500Z:1b2c3d4e

# Output:
# Assembling evidence pack...
# ✓ Policy definition (12 KB)
# ✓ SBOMs (2 files, 450 KB)
# ✓ Advisories (89 files, 234 KB)
# ✓ VEX statements (12 files, 45 KB)
# ✓ Verdicts (234 files, 567 KB)
# ✓ Reachability data (18 KB)
#
# Pack created: pack:run:P-7:20251223T140500Z:1b2c3d4e
# Size: 5.4 MB (compressed)
# Download: stella pack download pack:run:P-7:20251223T140500Z:1b2c3d4e
```

### Download Pack

```bash
stella pack download pack:run:P-7:20251223T140500Z:1b2c3d4e --output ./evidence-pack.tar.gz

# Output:
# Downloading pack:run:P-7:20251223T140500Z:1b2c3d4e...
# Downloaded 5.4 MB to ./evidence-pack.tar.gz
```

### Inspect Pack

```bash
stella pack inspect evidence-pack.tar.gz

# Output:
# Pack ID: pack:run:P-7:20251223T140500Z:1b2c3d4e
# Generated: 2025-12-23T14:10:00+00:00
# Policy: P-7 (version 4)
# Tenant: tenant-alpha
#
# Contents:
#   Policy: 2 files (12 KB)
#   SBOMs: 2 files (450 KB) - 1,742 components
#   Advisories: 89 files (234 KB)
#   VEX: 12 files (45 KB)
#   Verdicts: 234 files (567 KB)
#   Reachability: 3 files (18 KB)
#
# Total: 342 files, 1.3 MB (5.4 MB compressed)
# Determinism hash: sha256:pack-determinism...
# Signature: ✓ Verified (ed25519)
```

### List Pack Contents

```bash
stella pack list evidence-pack.tar.gz

# Output:
# manifest.json (signed manifest)
# policy/policy-P-7-v4.json
# policy/policy-run-run:P-7:20251223T140500Z:1b2c3d4e.json
# sbom/sbom-S-42.spdx.json
# sbom/sbom-S-318.spdx.json
# advisories/nvd-2025-12345.json
# ...
```

### Extract Artifact

```bash
stella pack export evidence-pack.tar.gz \
  --artifact sbom/sbom-S-42.spdx.json \
  --output ./sbom-S-42.spdx.json

# Output:
# Extracted sbom/sbom-S-42.spdx.json → ./sbom-S-42.spdx.json
```

### Verify Pack

```bash
stella pack verify evidence-pack.tar.gz

# Output:
# Verifying pack:run:P-7:20251223T140500Z:1b2c3d4e...
# ✓ Manifest signature valid
# ✓ Content integrity (342/342 files)
# ✓ Determinism hash matches
#
# Pack is valid and tamper-free
```

### Replay Policy

```bash
stella pack replay evidence-pack.tar.gz

# Output:
# Replaying policy P-7 (version 4)...
# Loading SBOMs (2 files)...
# Loading advisories (89 files)...
# Loading VEX statements (12 files)...
# Evaluating 1,742 components...
#
# Replay completed in 45.2s
# ✓ Determinism verified
# ✓ 234/234 verdicts match original
#
# Original run: run:P-7:20251223T140500Z:1b2c3d4e
# Replay run: replay:pack:...:20251223T150000Z
```

---

## Deterministic Replay

Evidence packs enable **deterministic policy replay**:

### Prerequisites

1. **Complete Context:** Pack contains all inputs (SBOMs, advisories, VEX, policy, environment)
2. **Timestamp Anchoring:** Advisory/VEX snapshots captured at exact cursor timestamps
3. **Canonical Inputs:** All inputs normalized and sorted deterministically

### Replay Process

```
1. Extract Pack → Verify Signature
2. Load Policy Definition (P-7 v4)
3. Load SBOMs (S-42, S-318)
4. Load Advisory Snapshots (at cursor 2025-12-23T13:59:00Z)
5. Load VEX Snapshots (at cursor 2025-12-23T13:58:30Z)
6. Reconstruct Policy Inputs (identical to original run)
7. Execute Policy Evaluation
8. Compare Replay Verdicts to Original Verdicts
9. Report Determinism Status
```

### Determinism Validation

```bash
# Replay and compare
stella pack replay evidence-pack.tar.gz --compare

# Output includes:
# - Total verdicts: 234
# - Matching: 234
# - Differences: 0
# - Determinism hash: sha256:... (matches original)
```

---

## Air-Gap Transfer

Evidence packs support **offline/air-gapped** workflows:

### Export from Online Environment

```bash
# Create pack from policy run
stella pack create run:P-7:20251223T140500Z:1b2c3d4e --output ./pack.tar.gz

# Verify before transfer
stella pack verify ./pack.tar.gz
```

### Transfer

```bash
# Copy to removable media or secure transfer channel
cp ./pack.tar.gz /media/usb-drive/
```

### Import to Air-Gapped Environment

```bash
# Verify pack integrity
stella pack verify /media/usb-drive/pack.tar.gz

# Replay policy (offline, no network)
stella pack replay /media/usb-drive/pack.tar.gz

# Extract artifacts
stella pack export /media/usb-drive/pack.tar.gz \
  --artifact verdicts/verdict-finding-1.json \
  --output ./verdict-1.json
```

---

## Performance

### Pack Assembly Time

| Component Count | Findings | Pack Size | Assembly Time |
|----------------|----------|-----------|---------------|
| 100 | 10 | 500 KB | 2s |
| 1,000 | 100 | 5 MB | 15s |
| 10,000 | 1,000 | 50 MB | 2min |
| 100,000 | 10,000 | 500 MB | 20min |

### Replay Time

Replay time ≈ 90% of original policy run time (overhead from deserialization)

---

## Storage

### Retention Policy

| Age | Storage Tier | Access Pattern |
|-----|--------------|----------------|
| < 7 days | Hot (PostgreSQL + S3 Standard) | Frequent |
| 7-30 days | Warm (S3 Infrequent Access) | Occasional |
| 30-90 days | Cold (S3 Glacier) | Rare |
| > 90 days | Archive (S3 Deep Archive) | Compliance-only |

### Compression Ratios

| Content Type | Uncompressed | Compressed | Ratio |
|--------------|--------------|------------|-------|
| SBOMs (JSON) | 10 MB | 2 MB | 5:1 |
| Advisories (JSON) | 5 MB | 1 MB | 5:1 |
| Verdicts (DSSE) | 15 MB | 4 MB | 3.75:1 |
| **Total Pack** | 30 MB | 7 MB | 4.3:1 |

---

## Security

### Manifest Signing

- **Algorithm:** Ed25519 (default), ECDSA P-256, RSA-PSS
- **Key Storage:** KMS, CryptoPro (GOST), offline signing ceremony
- **Verification:** Public key bundled or fetched from trusted registry

### Content Integrity

- **Per-File Digests:** SHA-256/SHA-384/SHA-512 for each artifact
- **Determinism Hash:** Aggregate hash over sorted content digests
- **Tamper Detection:** Any file modification invalidates manifest signature

### Access Control

- **Pack Creation:** `policy:pack:create` scope
- **Pack Download:** `policy:pack:read` scope
- **Pack Replay:** `policy:replay` scope
- **Tenant Isolation:** Packs scoped by `tenantId`

---

## Troubleshooting

### Pack Assembly Failed

**Symptom:** `POST /api/v1/runs/{runId}/evidence-pack` returns 500

**Causes:**
1. Missing artifacts (SBOM/VEX not found)
2. Object store unavailable
3. Signing key unavailable

**Resolution:**
```bash
# Check policy run completed
stella policy status run:P-7:20251223T140500Z:1b2c3d4e

# Verify all artifacts present
stella pack validate-inputs run:P-7:20251223T140500Z:1b2c3d4e

# Retry pack creation
stella pack create run:P-7:20251223T140500Z:1b2c3d4e
```

### Determinism Failure on Replay

**Symptom:** Replay verdicts differ from original

**Causes:**
1. Advisory/VEX drift (cursor mismatch)
2. Policy definition changed
3. Non-deterministic evaluation logic

**Resolution:**
```bash
# Compare inputs
stella pack diff-inputs evidence-pack.tar.gz --original-run run:...

# Identify divergence
stella pack replay evidence-pack.tar.gz --verbose --diff

# Output shows:
# - Finding X: original=blocked, replay=warned
# - Cause: VEX statement vex:... not found in pack
```

---

## References

- [Policy Replay Workflow](../policy/replay-workflow.md)
- [Verdict Attestations](../policy/verdict-attestations.md)
- [Evidence Locker Architecture](../modules/evidence-locker/architecture.md)
- [SPRINT_3000_0100_0002](../implplan/SPRINT_3000_0100_0002_evidence_packs.md)