# Proof Chain API Reference

> **Version**: 1.0.0  
> **OpenAPI Spec**: [`proofs-openapi.yaml`](./proofs-openapi.yaml)

The Proof Chain API provides endpoints for creating and verifying cryptographic proof bundles that link SBOM entries to vulnerability assessments through attestable DSSE envelopes.

---

## Overview

The proof chain creates an auditable, cryptographically-verifiable trail from vulnerability evidence through policy reasoning to VEX verdicts. Each component is signed with DSSE envelopes and aggregated into a merkle-rooted proof spine.

### Proof Chain Components

| Component | Predicate Type | Purpose |
|-----------|----------------|---------|
| **Evidence** | `evidence.stella/v1` | Raw findings from scanners/feeds |
| **Reasoning** | `reasoning.stella/v1` | Policy evaluation trace |
| **VEX Verdict** | `cdx-vex.stella/v1` | Final VEX status determination |
| **Proof Spine** | `proofspine.stella/v1` | Merkle aggregation of all components |
| **Verdict Receipt** | `verdict.stella/v1` | Human-readable verification receipt |

### Content-Addressed IDs

All proof chain components use content-addressed identifiers:

```
Format: sha256:<64-hex-chars>
Example: sha256:e7f8a9b0c1d2e3f4a5b6c7d8e9f0a1b2c3d4e5f6...
```

IDs are computed by:
1. Canonicalizing the JSON payload (RFC 8785/JCS)
2. Computing SHA-256 hash
3. Prefixing with `sha256:`

---

## Authentication

All endpoints require authentication via:

- **Bearer Token**: Authority-issued OpToken with appropriate scopes
- **mTLS**: Mutual TLS with client certificate (service-to-service)

Required scopes:
- `proofs.read` - Read proof bundles and receipts
- `proofs.write` - Create proof spines
- `anchors.manage` - Manage trust anchors
- `proofs.verify` - Perform verification

---

## Endpoints

### Proofs

#### POST /proofs/{entry}/spine

Create a proof spine for an SBOM entry.

**Parameters:**
- `entry` (path, required): SBOMEntryID in format `sha256:<hash>:pkg:<purl>`

**Request Body:**
```json
{
  "evidenceIds": ["sha256:e7f8a9b0..."],
  "reasoningId": "sha256:f0e1d2c3...",
  "vexVerdictId": "sha256:d4c5b6a7...",
  "policyVersion": "v1.2.3"
}
```

**Response (201 Created):**
```json
{
  "proofBundleId": "sha256:1a2b3c4d...",
  "receiptUrl": "/proofs/sha256:abc:pkg:npm/lodash@4.17.21/receipt"
}
```

**Errors:**
- `400 Bad Request`: Invalid SBOM entry ID format
- `404 Not Found`: Evidence, reasoning, or VEX verdict not found
- `422 Unprocessable Entity`: Validation error

---

#### GET /proofs/{entry}/spine

Get the proof spine for an SBOM entry.

**Parameters:**
- `entry` (path, required): SBOMEntryID

**Response (200 OK):**
```json
{
  "sbomEntryId": "sha256:abc123:pkg:npm/lodash@4.17.21",
  "proofBundleId": "sha256:1a2b3c4d...",
  "evidenceIds": ["sha256:e7f8a9b0..."],
  "reasoningId": "sha256:f0e1d2c3...",
  "vexVerdictId": "sha256:d4c5b6a7...",
  "policyVersion": "v1.2.3",
  "createdAt": "2025-12-17T10:00:00Z"
}
```

---

#### GET /proofs/{entry}/receipt

Get the verification receipt for an SBOM entry's proof spine.

**Response (200 OK):**
```json
{
  "graphRevisionId": "grv_sha256:9f8e7d6c...",
  "findingKey": {
    "sbomEntryId": "sha256:abc123:pkg:npm/lodash@4.17.21",
    "vulnerabilityId": "CVE-2025-1234"
  },
  "rule": {
    "id": "critical-vuln-block",
    "version": "v1.0.0"
  },
  "decision": {
    "verdict": "pass",
    "severity": "none",
    "reasoning": "Not affected - vulnerable code not present"
  },
  "createdAt": "2025-12-17T10:00:00Z",
  "verified": true
}
```

---

#### GET /proofs/{entry}/vex

Get the VEX attestation for an SBOM entry.

**Response (200 OK):**
```json
{
  "sbomEntryId": "sha256:abc123:pkg:npm/lodash@4.17.21",
  "vulnerabilityId": "CVE-2025-1234",
  "status": "not_affected",
  "justification": "vulnerable_code_not_present",
  "policyVersion": "v1.2.3",
  "reasoningId": "sha256:f0e1d2c3...",
  "vexVerdictId": "sha256:d4c5b6a7..."
}
```

---

### Trust Anchors

#### GET /anchors

List all configured trust anchors.

**Response (200 OK):**
```json
{
  "anchors": [
    {
      "id": "anchor-001",
      "keyId": "sha256:abc123...",
      "algorithm": "ECDSA-P256",
      "status": "active",
      "createdAt": "2025-01-01T00:00:00Z"
    }
  ]
}
```

---

#### POST /anchors

Create a new trust anchor.

**Request Body:**
```json
{
  "keyId": "sha256:abc123...",
  "algorithm": "ECDSA-P256",
  "publicKey": "-----BEGIN PUBLIC KEY-----\n..."
}
```

**Response (201 Created):**
```json
{
  "id": "anchor-002",
  "keyId": "sha256:abc123...",
  "algorithm": "ECDSA-P256",
  "status": "active",
  "createdAt": "2025-12-17T10:00:00Z"
}
```

---

#### DELETE /anchors/{anchorId}

Delete (revoke) a trust anchor.

**Response:** `204 No Content`

---

### Verification

#### POST /verify

Perform full verification of a proof bundle.

**Request Body:**
```json
{
  "proofBundleId": "sha256:1a2b3c4d...",
  "checkRekor": true,
  "anchorIds": ["anchor-001"]
}
```

**Response (200 OK):**
```json
{
  "proofBundleId": "sha256:1a2b3c4d...",
  "verified": true,
  "checks": {
    "signatureValid": true,
    "idRecomputed": true,
    "merklePathValid": true,
    "rekorInclusionValid": true
  },
  "errors": [],
  "verifiedAt": "2025-12-17T10:00:00Z"
}
```

**Verification Steps:**
1. **Signature Verification**: Verify DSSE envelope signatures against trust anchors
2. **ID Recomputation**: Recompute content-addressed IDs and compare
3. **Merkle Path Verification**: Verify proof bundle merkle tree construction
4. **Rekor Inclusion**: Verify transparency log inclusion proof (if enabled)

---

#### POST /verify/batch

Verify multiple proof bundles in a single request.

**Request Body:**
```json
{
  "bundles": [
    { "proofBundleId": "sha256:1a2b3c4d...", "checkRekor": true },
    { "proofBundleId": "sha256:5e6f7g8h...", "checkRekor": false }
  ]
}
```

**Response (200 OK):**
```json
{
  "results": [
    { "proofBundleId": "sha256:1a2b3c4d...", "verified": true, "checks": {...} },
    { "proofBundleId": "sha256:5e6f7g8h...", "verified": false, "errors": ["..."] }
  ]
}
```

---

## Error Handling

All errors follow RFC 7807 Problem Details format:

```json
{
  "title": "Validation Error",
  "detail": "Evidence ID sha256:abc... not found",
  "status": 422,
  "errors": {
    "evidenceIds[0]": ["Evidence not found"]
  }
}
```

### Common Error Codes

| Status | Meaning |
|--------|---------|
| 400 | Invalid request format or parameters |
| 401 | Authentication required |
| 403 | Insufficient permissions |
| 404 | Resource not found |
| 409 | Conflict (e.g., anchor already exists) |
| 422 | Validation error |
| 500 | Internal server error |

---

## Offline Verification

For air-gapped environments, verification can be performed without Rekor:

```json
{
  "proofBundleId": "sha256:1a2b3c4d...",
  "checkRekor": false
}
```

This skips Rekor inclusion proof verification but still performs:
- DSSE signature verification
- Content-addressed ID recomputation
- Merkle path verification

---

## Related Documentation

- [Proof Chain Predicates](../modules/attestor/architecture.md#predicate-types) - DSSE predicate type specifications
- [Content-Addressed IDs](../modules/attestor/architecture.md#content-addressed-identifier-formats) - ID generation rules
- [Attestor Architecture](../modules/attestor/architecture.md) - Full attestor module documentation