gr2m/github-app-token-action

GitHub Action for creating a GitHub App Installation Access Token

Usage

In order to use this action, you need to:

1. Register new GitHub App
2. Store the App's ID in your repository environment variables (example: APP_ID)
3. Store the App's private key in your repository secrets (example: PRIVATE_KEY)

Minimal usage

on: [issues]

jobs:
  hello-world:
    runs-on: ubuntu-latest
    steps:
      - uses: gr2m/github-app-token-action@v1
        id: app-token
        with:
          app_id: ${{ vars.APP_ID }}
          private_key: ${{ secrets.PRIVATE_KEY }}
      - uses: peter-evans/create-or-update-comment@v3
        with:
          token: ${{ steps.app-token.outputs.token }}
          issue-number: ${{ github.event.issue.number }}
          body: "Hello, World!"

Limit the app's permissions and access to repositories

on: [issues]

jobs:
  with-scoped-token:
    runs-on: ubuntu-latest
    steps:
      - uses: gr2m/github-app-token-action@v1
        id: app-token
        with:
          # required
          app_id: ${{ vars.APP_ID }}
          private_key: ${{ secrets.PRIVATE_KEY }}
      # do something with the token

Use app token with actions/checkout

on: [pull_request]

jobs:
  auto-format:
    runs-on: ubuntu-latest
    steps:
      - uses: gr2m/github-app-token-action@v1
        id: app-token
        with:
          # required
          app_id: ${{ vars.APP_ID }}
          private_key: ${{ secrets.PRIVATE_KEY }}
      - uses: actions/checkout@v3
        with:
          token: ${{ steps.app-token.outputs.token }}
          ref: ${{ github.head_ref }}
          # Make sure the value of GITHUB_TOKEN will not be persisted in repo's config
          persist-credentials: false
      - uses: creyD/prettier_action@v4.3
        with:
          github_token: ${{ steps.app-token.outputs.token }}

Inputs

app_id

Required: GitHub app ID.

private_key

Required: GitHub app private key.

Outputs

token

GitHub installation access token.

How it works

The action creates an installation access token using the POST /app/installations/{installation_id}/access_tokens endpoint. By default,

1. The token is scoped to the current repository
2. The token inherits all the installation's permissions
3. The token is set as output token which can be used in subsequent steps
4. The token is revoked in the post step of the action, which means it cannot be passed to another job.
5. The token is masked, it cannot be logged accidentally. That is not a feature by the action, but by the GitHub Actions runner itself, due to the specific format of GitHub tokens.

Note

Installation permissions can differ from the app's permissions they belong to. Installation permissions are set when an app is installed on an account. When the app adds more permissions after the installation, an account administrator will have to approve the new permissions before they are set on the installation.

License

MIT