Github Actions

GitHub Actions Command

Structured guidance for designing, hardening, reviewing, and debugging GitHub Actions workflows.

Activation

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/platform-skills:github-actions design    # reusable workflow or job graph design
/platform-skills:github-actions security  # OIDC, SHA pinning, token scoping, secrets hygiene
/platform-skills:github-actions review    # production-readiness checklist for an existing workflow
/platform-skills:github-actions debug     # diagnose a failing workflow or job

Interactive Wizard (fires when no mode is provided)

When invoked with no arguments, ask before proceeding:

Q1 — Mode?

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What do you need?
  1. design    — reusable workflow, job graph, promotion pipeline
  2. security  — OIDC federation, SHA pinning, token scoping, secret hygiene
  3. review    — production-readiness checklist for an existing workflow file
  4. debug     — job failure, permission error, OIDC rejection, missing context

Enter 1–4 or mode name:

Q2 — Context (after mode selected):

• design: Describe what the workflow should do — validate, build, promote, deploy?
• security: Paste the workflow file or describe the auth pattern you are using.
• review: Paste the workflow file or provide the path.
• debug: Paste the error output or describe the failure symptom.

Mode: design

Triggers: design, build workflow, create pipeline, reusable workflow, job graph, promote, deploy flow

Read references/github-actions.md before responding.

Step 1 — Classify the workflow type

Step 2 — Apply the canonical job pattern

Every workflow should follow this job order:

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validate → build → [test] → promote → [deploy]

• validate: lint, format, policy gates, unit checks — fast, no credentials
• build: image or artifact packaging — OIDC to registry
• promote: update version pin or overlay in Git — triggers GitOps reconciler
• deploy: guarded apply only if not using GitOps

Keep jobs small and named by intent. If a job is hard to name, it is doing too much.

Step 3 — Reusable workflow structure

yamlCopy code
# .github/workflows/validate.yml — called by other workflows
on:
  workflow_call:
    inputs:
      environment:
        required: true
        type: string
        description: "Target environment (dev | staging | prod)"
    secrets:
      token:
        required: true

jobs:
  validate:
    runs-on: ubuntu-latest
    permissions:
      contents: read
    steps:
      - uses: actions/checkout@9c091bb21b7c1c1d1991bb908d89e4e9dddfe3e0  # v7.0.0
        with:
          token: ${{ secrets.token }}

Step 4 — Promotion orchestration

Prefer updating Git over imperative deploys:

yamlCopy code
# promote job — updates the version pin in the GitOps repo
promote:
  needs: build
  runs-on: ubuntu-latest
  permissions:
    contents: write
  steps:
    - uses: actions/checkout@9c091bb21b7c1c1d1991bb908d89e4e9dddfe3e0  # v7.0.0
    - name: Update image tag
      env:
        NEW_TAG: ${{ needs.build.outputs.image_tag }}
      run: |
        sed -i "s|image:.*|image: ghcr.io/org/app:${NEW_TAG}|" \
          deploy/overlays/${{ inputs.environment }}/kustomization.yaml
        git config user.email "ci@org.com"
        git config user.name "CI"
        git commit -am "chore: promote app to ${NEW_TAG} in ${{ inputs.environment }}"
        git push

Handoffs:

• Extracting repeated steps → /platform-skills:composite-actions
• Terraform plan/apply in the workflow → /platform-skills:terraform
• GitOps reconciler that picks up the promotion commit → /platform-skills:gitops

Mode: security

Triggers: OIDC, pin, SHA, token, permissions, secrets, secure, harden, federation

Read references/github-actions.md before responding.

Repositories with Kubernetes manifests or Helm charts: the posture gate is /platform-skills:kubescape ci (signature-verified CLI install, fails PRs only on new findings). Do not use kubescape/github-action: its latest release bundles CLI v3.0.21 and its README pins @main.

OIDC federation — AWS

yamlCopy code
permissions:
  id-token: write    # required for OIDC token request
  contents: read

steps:
  - uses: aws-actions/configure-aws-credentials@254c19bd240aabef8777f48595e9d2d7b972184b  # v6.2.1
    with:
      role-to-assume: arn:aws:iam::123456789012:role/github-actions-deploy
      aws-region: eu-north-1

IAM trust policy (scope to repo and branch):

jsonCopy code
{
  "Condition": {
    "StringLike": {
      "token.actions.githubusercontent.com:sub": "repo:org/repo:ref:refs/heads/main"
    }
  }
}

OIDC federation — Azure

yamlCopy code
permissions:
  id-token: write
  contents: read

steps:
  - uses: azure/login@532459ea530d8321f2fb9bb10d1e0bcf23869a43  # v3.0.0
    with:
      client-id: ${{ secrets.AZURE_CLIENT_ID }}
      tenant-id: ${{ secrets.AZURE_TENANT_ID }}
      subscription-id: ${{ secrets.AZURE_SUBSCRIPTION_ID }}

SHA pinning checklist

bashCopy code
# Resolve a tag to its current commit SHA
gh api repos/{owner}/{repo}/git/refs/tags/{tag} \
  --jq '.object.sha'

# For actions that use a commit SHA directly (not a tag ref):
gh api repos/{owner}/{repo}/commits/{tag} --jq '.sha'

Add the version as a comment so reviewers can audit without resolving the SHA manually:

yamlCopy code
uses: actions/checkout@9c091bb21b7c1c1d1991bb908d89e4e9dddfe3e0  # v7.0.0

Token scoping — minimum permissions per job

Set permissions: {} at the workflow level to deny all, then grant per-job:

yamlCopy code
permissions: {}   # deny all at workflow level

jobs:
  build:
    permissions:
      contents: read
      id-token: write
      packages: write

Secret hygiene

• Store secrets in GitHub Environments, not at repository level, for deployment secrets
• Never print secrets: avoid echo $SECRET in run: steps
• Mask dynamic secrets: echo "::add-mask::${DYNAMIC_SECRET}"
• Rotate long-lived tokens on a schedule; prefer OIDC to eliminate them
• Audit secret usage: gh secret list and gh secret list --env <env>

Mode: review

Triggers: review, audit, checklist, is this workflow safe, production ready

Ask the user to paste the workflow file or provide the path. Then evaluate against:

CRITICAL (must fix before merge)

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❌ External `uses:` with mutable tag (@v4, @main, @latest) — supply chain risk; pin to full SHA
❌ `permissions: write-all` or no permissions block — grants all scopes by default
❌ `${{ github.event.*.body }}` or PR title interpolated in run: — script injection risk
❌ Long-lived cloud credentials stored as secrets — replace with OIDC
❌ `pull_request_target` with checkout of the PR head — arbitrary code execution risk

WARNING (should fix)

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⚠️  No concurrency group — parallel runs on same branch can conflict or double-deploy
⚠️  No timeout-minutes on jobs — a hung job blocks runners indefinitely
⚠️  Secrets passed to untrusted third-party actions — scope secrets to first-party or audited actions only
⚠️  Environment protection rules not used for production deploys
⚠️  No required status checks on the branch protection rule this workflow targets

INFORMATIONAL

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ℹ️  No dependabot.yml for github-actions ecosystem — action versions will drift
ℹ️  Reusable workflow could replace copy-pasted job sequence
ℹ️  Job name does not describe intent clearly

Report format:

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## Review: <workflow-name>

### CRITICAL (N findings)
❌ Line 12: uses: actions/checkout@v4 — pin to SHA. Current SHA: <sha>

### WARNING (N findings)
⚠️  No concurrency group defined

### INFORMATIONAL (N findings)
ℹ️  No dependabot.yml for the github-actions ecosystem

### Score: N/15 — Poor | Fair | Good | Excellent

Mode: debug

Triggers: failing, error, permission denied, OIDC, 401, 403, missing context, debug, not working

Identify the failure layer first:

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1. Syntax / parse error          → workflow YAML invalid
2. Permission / auth error       → token scoping, OIDC trust, secret missing
3. Missing context               → expression evaluates to empty, wrong event trigger
4. Action version mismatch       → SHA pinned to a version with a breaking change
5. Runner environment            → tool not available on runner image
6. Downstream service error      → cloud API, registry, or deploy target failing

Diagnosis by error type

Resource not accessible by integration / 403

yamlCopy code
# Check the permissions block — add the missing scope
permissions:
  contents: write       # missing if you get 403 on git push
  pull-requests: write  # missing if you get 403 on PR comment
  id-token: write       # missing if OIDC token request fails

OIDC rejection (Not authorized to perform sts:AssumeRoleWithWebIdentity)

1. Confirm id-token: write is set on the job
2. Check the IAM trust policy sub condition matches the exact repo/branch/env
3. Confirm the workflow is running from the branch/environment specified in the condition
4. For environment-scoped trust: repo:org/repo:environment:production — job must use environment: production

yamlCopy code
# Decode the OIDC token to inspect claims (add a debug step temporarily)
- name: Inspect OIDC token claims
  run: |
    TOKEN=$(curl -sSfL -H "Authorization: bearer $ACTIONS_ID_TOKEN_REQUEST_TOKEN" \
      "${ACTIONS_ID_TOKEN_REQUEST_URL}&audience=sts.amazonaws.com" | jq -r '.value')
    echo "${TOKEN}" | cut -d. -f2 | base64 -d 2>/dev/null | jq

Expression evaluates to empty

yamlCopy code
# Workflow inputs are empty in non-workflow_call events
# Guard with:
- if: ${{ inputs.environment != '' }}

Context access might be invalid

Caused by accessing a context that does not exist for the triggering event (e.g. github.event.pull_request on a push event). Check which contexts are available for the trigger.

Validation command

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# Lint the workflow file locally before pushing — syntax, expressions, shell
actionlint .github/workflows/<workflow>.yml

# Audit the same file for security findings — a valid workflow can still be unsafe
zizmor --strict-collection .github/workflows/<workflow>.yml

# Check recent run failures with full logs
gh run list --workflow <workflow>.yml --limit 10
gh run view <run-id> --log-failed

actionlint and zizmor do not overlap. actionlint answers "is this workflow valid" (syntax, expression types, shellcheck on run:). zizmor answers "is this workflow safe" (template injection, credential persistence, unpinned uses:, over-broad permissions:, impostor commits). Run both. For the full audit catalogue, policy file, and CI gate: /platform-skills:zizmor.

Common mistakes

• pull_request_target + PR head checkout — runs with write permissions and access to secrets; combined with checkout of untrusted code this allows secret exfiltration. Never checkout ${{ github.event.pull_request.head.sha }} in a pull_request_target workflow.
• Mutable action tags — @v4 can be rewritten by the action author; a supply chain compromise silently executes attacker code. Always pin to SHA.
• Over-scoped GITHUB_TOKEN — default permissions can be broad depending on repo settings. Always set an explicit permissions: block.
• Forgetting OIDC requires the job's environment to match the trust policy — if the trust uses environment:production, the job must declare environment: production or the token request is rejected.
• workflow_dispatch with no input validation — inputs are free-text by default. Use type: choice for enum inputs and validate string inputs in the first step.

Reference

Full guidance: references/github-actions.md

For composite action scaffolding and review: /platform-skills:composite-actions

For workflow security auditing with zizmor (audit catalogue, zizmor.yml policy, auto-fix, CI gate, pre-commit): /platform-skills:zizmor

Examples:

• examples/github-actions/terraform-cicd.yml — Terraform plan + apply with OIDC
• examples/github-actions/container-build.yml — Docker build + GHCR push
• examples/github-actions/reusable-workflows/ — reusable workflow patterns