Agent Supply Chain

# Agent Supply Chain Integrity

Generate and verify integrity manifests for AI agent plugins and tools. Detect tampering, enforce version pinning, and establish supply chain provenance.

## Overview

Agent plugins and MCP servers have the same supply chain risks as npm packages or container images — except the ecosystem has no equivalent of npm provenance, Sigstore, or SLSA. This skill fills that gap.

```
Plugin Directory → Hash All Files (SHA-256) → Generate INTEGRITY.json
                                                    ↓
Later: Plugin Directory → Re-Hash Files → Compare Against INTEGRITY.json
                                                    ↓
                                          Match? VERIFIED : TAMPERED
```

## When to Use

- Before promoting a plugin from development to production
- During code review of plugin PRs
- As a CI step to verify no files were modified after review
- When auditing third-party agent tools or MCP servers
- Building a plugin marketplace with integrity requirements

---

## Pattern 1: Generate Integrity Manifest

Create a deterministic `INTEGRITY.json` with SHA-256 hashes of all plugin files.

```python
import hashlib
import json
from datetime import datetime, timezone
from pathlib import Path

EXCLUDE_DIRS = {".git", "__pycache__", "node_modules", ".venv", ".pytest_cache"}
EXCLUDE_FILES = {".DS_Store", "Thumbs.db", "INTEGRITY.json"}

def hash_file(path: Path) -> str:
    """Compute SHA-256 hex digest of a file."""
    h = hashlib.sha256()
    with open(path, "rb") as f:
        for chunk in iter(lambda: f.read(8192), b""):
            h.update(chunk)
    return h.hexdigest()

def generate_manifest(plugin_dir: str) -> dict:
    """Generate an integrity manifest for a plugin directory."""
    root = Path(plugin_dir)
    files = {}

    for path in sorted(root.rglob("*")):
        if not path.is_file():
            continue
        if path.name in EXCLUDE_FILES:
            continue
        if any(part in EXCLUDE_DIRS for part in path.relative_to(root).parts):
            continue
        rel = path.relative_to(root).as_posix()
        files[rel] = hash_file(path)

    # Chain hash: SHA-256 of all file hashes concatenated in sorted order
    chain = hashlib.sha256()
    for key in sorted(files.keys()):
        chain.update(files[key].encode("ascii"))

    manifest = {
        "plugin_name": root.name,
        "generated_at": datetime.now(timezone.utc).isoformat(),
        "algorithm": "sha256",
        "file_count": len(files),
        "files": files,
        "manifest_hash": chain.hexdigest(),
    }
    return manifest

# Generate and save
manifest = generate_manifest("my-plugin/")
Path("my-plugin/INTEGRITY.json").write_text(
    json.dumps(manifest, indent=2) + "\n"
)
print(f"Generated manifest: {manifest['file_count']} files, "
      f"hash: {manifest['manifest_hash'][:16]}...")
```

**Output (`INTEGRITY.json`):**
```json
{
  "plugin_name": "my-plugin",
  "generated_at": "2026-04-01T03:00:00+00:00",
  "algorithm": "sha256",
  "file_count": 12,
  "files": {
    ".claude-plugin/plugin.json": "a1b2c3d4...",
    "README.md": "e5f6a7b8...",
    "skills/search/SKILL.md": "c9d0e1f2...",
    "agency.json": "3a4b5c6d..."
  },
  "manifest_hash": "7e8f9a0b1c2d3e4f..."
}
```

---

## Pattern 2: Verify Integrity

Check that current files match the manifest.

```