Supply chain advisory

Overview

Supply chain attacks bypass traditional code review by compromising upstream dependencies. This skill provides patterns for detecting, preventing, and responding to compromised packages in Python ecosystems.

When To Use

• After a supply chain advisory is published
• When auditing dependencies for a new or existing project
• During incident response for a suspected compromise
• When adding the SessionStart hook to a project

When NOT To Use

• General CVE triage unrelated to dependency supply chain
• Application-level vulnerability scanning (use a SAST tool)
• License compliance audits (different concern)

Known-Bad Versions Blocklist

The blocklist is at ${CLAUDE_SKILL_DIR}/known-bad-versions.json. It is consumed by:

1. SessionStart hook: warns per-session when compromised versions detected
2. make supply-chain-scan: CI/local scanning target
3. This skill: manual audit guidance

Blocklist Format

{
  "package_name": [{
    "versions": ["x.y.z"],
    "date": "YYYY-MM-DD",
    "description": "What the attack did",
    "indicators": ["files or patterns to search for"],
    "source": "advisory URL",
    "severity": "critical|high|medium"
  }]
}

Adding a New Entry

1. Add the entry to ${CLAUDE_SKILL_DIR}/known-bad-versions.json
2. Add version exclusions (!=x.y.z) to affected pyproject.toml files
3. Document in docs/dependency-audit.md under Supply Chain Incidents
4. Run make supply-chain-scan to verify detection works

Quick Scan Commands

Check all lockfiles on machine for known-bad versions

# Scan uv.lock files for a specific compromised version
grep -r "package_name.*version" --include="uv.lock" /path/to/projects

# Search for malicious artifacts
find /path/to/projects -name "suspicious_file.pth" 2>/dev/null

# Check installed versions in virtualenvs
find /path/to/projects -path "*/.venv/lib/*/PACKAGE*/METADATA" \
  -exec grep "^Version:" {} +

Verify lockfile hash integrity

uv.lock includes SHA256 hashes for every package. If a package is re-published with different content under the same version, uv sync will fail with a hash mismatch. This is your strongest automatic defense.

Defense Layers

Layer	Tool	Catches
Lockfile hashes	uv.lock SHA256	Tampered re-published versions
Version exclusions	pyproject.toml !=	Known-bad versions on fresh resolve
SessionStart hook	sanctum hook	Per-session warning for compromised deps
CI scanning	OSV, Safety	CVE database, and advisory matching
Artifact scanning	make supply-chain-scan	Malicious files (.pth, scripts)

Limitations

• Zero-day supply chain attacks have no prior advisory: lockfile hashes are the only automatic defense during the attack window
• Safety/CVE databases lag behind real-world compromises
• OSV provides broader coverage but is still reactive

Exit Criteria

• ${CLAUDE_SKILL_DIR}/known-bad-versions.json checked against all lockfiles in scope; any match reported with package name, bad version, severity, and advisory URL
• When a new known-bad entry is added: version exclusion (!=x.y.z) added to the affected pyproject.toml, entry documented in docs/dependency-audit.md, and make supply-chain-scan run to confirm detection works
• uv.lock SHA256 hash integrity verified; uv sync failure on hash mismatch surfaces as an explicit supply-chain warning rather than a generic install error
• Artifact scan checks for malicious file patterns (.pth files, unexpected scripts) in virtualenv paths before the session proceeds