GitHub Actions Lint & Security

Static analysis and security checking tools for GitHub Actions workflows. All tools are available via nixpkgs for local use. Each tool covers different checks with no overlap, so using all of them together is recommended.

Tool	Purpose	nixpkgs
actionlint	Workflow syntax checking	nixpkgs#actionlint
pinact	SHA-pin action references	nixpkgs#pinact
ghalint	Security best practices	nixpkgs#ghalint
zizmor	Security vulnerability analysis	nixpkgs#zizmor

---

actionlint

Syntax and type checker for workflow files. Integrates with shellcheck / pyflakes to also inspect inline scripts.

Basic Commands

# Auto-detect and check all files under .github/workflows/
nix run nixpkgs#actionlint

# Check a specific file
nix run nixpkgs#actionlint -- .github/workflows/nix-build.yaml

# JSON output
nix run nixpkgs#actionlint -- -format '{{json .}}'

What It Detects

• Workflow syntax errors (missing required keys, duplicate keys, invalid values)
• Type checking of ${{ }} expressions (undefined context references, etc.)
• Shell script issues via shellcheck
• Python script issues via pyflakes
• Matrix inconsistencies, invalid glob patterns
• Deprecated commands (set-output, etc.)

CI Usage

Use suzuki-shunsuke/actionlint-action (installs actionlint + reviewdog + shellcheck via aqua):

- uses: suzuki-shunsuke/actionlint-action@29e0b7cda52e51a495d15f22759745ef6e19583a # v0.1.1

Or use the official download script:

- name: Install actionlint
  run: bash <(curl https://raw.githubusercontent.com/rhysd/actionlint/main/scripts/download-actionlint.bash)
- name: actionlint
  run: ./actionlint

---

pinact

Converts GitHub Actions version references to commit SHAs. Prevents supply chain attacks via tag rewriting.

Configuration

Place .pinact.yml at the repository root:

# yaml-language-server: $schema=https://raw.githubusercontent.com/suzuki-shunsuke/pinact/refs/heads/main/json-schema/pinact.json
version: 3

Initialize: nix run nixpkgs#pinact -- init

Basic Commands

# Pin all actions under .github/workflows/
nix run nixpkgs#pinact -- run

# Include composite actions etc.
nix run nixpkgs#pinact -- run \
  .github/actions/setup-nix/action.yaml \
  .github/actions/setup-git-bot/action.yaml

# Validate only (no file changes, good for CI)
nix run nixpkgs#pinact -- run --check

# Show diff only
nix run nixpkgs#pinact -- run --diff

# Update to latest versions
nix run nixpkgs#pinact -- run --update

Conversion Format

# Before
- uses: actions/checkout@v4

# After
- uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v4.3.1

• Tags are replaced with SHAs; the original version is appended as a comment
• Files outside .github/workflows/ (composite actions, etc.) must be specified explicitly

Key Options

Option	Description
--check	Non-zero exit if unpinned references exist. No file changes
--verify, -v	Verify SHA and version annotation consistency
--update, -u	Update to latest versions
--diff	Output diff only. No file changes
--include, -i	Filter targets by regex
--exclude, -e	Exclude targets by regex
--min-age, -m	Skip releases newer than N days (use with -u)

CI Usage

Use suzuki-shunsuke/pinact-action:

- uses: suzuki-shunsuke/pinact-action@1081f5ad49ac904b7d977784f338145150a32112 # v1.4.0
  with:
    skip_push: 'true'

---

ghalint

Linter for security best practices in workflow and action definitions.

Basic Commands

# Check workflows
nix run nixpkgs#ghalint -- run

# Check action definitions
nix run nixpkgs#ghalint -- run-action

What It Detects

• Jobs missing explicit permissions
• Action references not pinned to commit SHAs
• actions/checkout without persist-credentials: false
• Other security best practice violations

CI Usage

Install via aqua:

- uses: aquaproj/aqua-installer@11dd79b4e498d471a9385aa9fb7f62bb5f52a73c # v4.0.4
  with:
    aqua_version: v2.56.6
- run: ghalint run
  env:
    GHALINT_LOG_COLOR: always

Requires aqua.yaml in the repository with ghalint registered:

# aqua.yaml
registries:
  - type: standard
    ref: v4.294.0
packages:
  - name: suzuki-shunsuke/ghalint@v1.5.5

---

zizmor

Security vulnerability analyzer for GitHub Actions. Offers 3 personas to tune detection sensitivity.

Basic Commands

# Analyze current repository (auto-detects .github/)
nix run nixpkgs#zizmor -- .

# Check a specific file
nix run nixpkgs#zizmor -- .github/workflows/nix-build.yaml

# Pedantic mode (also detects code smells)
nix run nixpkgs#zizmor -- --pedantic .

# Offline mode (no GitHub API needed)
nix run nixpkgs#zizmor -- --offline .

# SARIF output
nix run nixpkgs#zizmor -- --format sarif .

Personas (Detection Sensitivity)

Persona	Description
regular (default)	Minimizes false positives
pedantic	Also detects code smells
auditor	Comprehensive detection, tolerates false positives

What It Detects

• Excessive permissions settings
• Code injection via template expansion (${{ }})
• Direct use of untrusted inputs
• Potential commit spoofing
• Dangerous use of pull_request_target
• Improper use of self-hosted runners

CI Usage

Use zizmorcore/zizmor-action:

- uses: zizmorcore/zizmor-action@0dce2577a4760a2749d8cfb7a84b7d5585ebcb7d # v0.5.0

With GitHub Advanced Security:

- uses: zizmorcore/zizmor-action@0dce2577a4760a2749d8cfb7a84b7d5585ebcb7d # v0.5.0

Without Advanced Security:

- uses: zizmorcore/zizmor-action@0dce2577a4760a2749d8cfb7a84b7d5585ebcb7d # v0.5.0
  with:
    advanced-security: false

---

CI Integration: All Tools Combined

Example workflow combining all 4 tools using their official actions (no nixpkgs):

name: 'CI: GitHub Actions lint'

on:
  pull_request:
  workflow_dispatch:

concurrency:
  group: ${{ github.workflow }}-${{ github.ref }}
  cancel-in-progress: true

permissions: {}

jobs:
  gha-lint:
    runs-on: ubuntu-24.04-arm
    timeout-minutes: 10
    permissions:
      contents: read
      actions: read
    steps:
      - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
        with:
          persist-credentials: false

      - name: actionlint
        run: |
          bash <(curl https://raw.githubusercontent.com/rhysd/actionlint/main/scripts/download-actionlint.bash)
          ./actionlint

      - uses: suzuki-shunsuke/pinact-action@1081f5ad49ac904b7d977784f338145150a32112 # v1.4.0
        with:
          skip_push: 'true'

      - uses: aquaproj/aqua-installer@11dd79b4e498d471a9385aa9fb7f62bb5f52a73c # v4.0.4
        with:
          aqua_version: v2.56.6
      - name: ghalint
        run: ghalint run
        env:
          GHALINT_LOG_COLOR: always

      - uses: zizmorcore/zizmor-action@0dce2577a4760a2749d8cfb7a84b7d5585ebcb7d # v0.5.0
        with:
          advanced-security: false

---

Workflow: When Adding or Modifying GitHub Actions

1. Edit workflows or composite actions
2. Run all tools locally:

nix run nixpkgs#actionlint
nix run nixpkgs#pinact -- run
nix run nixpkgs#ghalint -- run
nix run nixpkgs#zizmor -- .

3. Review changes and commit:

git diff

4. Open a PR and verify CI passes

Notes

• Setting GITHUB_TOKEN / GH_TOKEN avoids API rate limits (pinact, zizmor)
• actionlint auto-integrates with shellcheck and pyflakes if they're in PATH (nixpkgs version bundles them)
• ghalint's checks partially overlap with pinact (SHA pinning), but ghalint also covers other best practices, so using both is worthwhile