cosign-installer GitHub Action

This action enables you to sign and verify container images using cosign. cosign-installer verifies the integrity of the cosign release during installation.

For a quick start guide on the usage of cosign, please refer to https://github.com/sigstore/cosign#quick-start. For available cosign releases, see https://github.com/sigstore/cosign/releases.

Usage

This action currently supports GitHub-provided Linux, macOS and Windows runners (self-hosted runners may not work).

Add the following entry to your Github workflow YAML file:

uses: sigstore/cosign-installer@v3.5.0
with:
  cosign-release: 'v2.2.4' # optional

Example using a pinned version:

jobs:
  example:
    runs-on: ubuntu-latest

    permissions: {}

    name: Install Cosign
    steps:
      - name: Install Cosign
        uses: sigstore/cosign-installer@v3.5.0
        with:
          cosign-release: 'v2.2.4'
      - name: Check install!
        run: cosign version

Example using the default version:

jobs:
  example:
    runs-on: ubuntu-latest

    permissions: {}

    name: Install Cosign
    steps:
      - name: Install Cosign
        uses: sigstore/cosign-installer@v3.5.0
      - name: Check install!
        run: cosign version

If you want to install cosign from its main version by using 'go install' under the hood, you can set 'cosign-release' as 'main'. Once you did that, cosign will be installed via 'go install' which means that please ensure that go is installed.

Example of installing cosign via go install:

jobs:
  example:
    runs-on: ubuntu-latest

    permissions: {}

    name: Install Cosign via go install
    steps:
      - name: Install go
        uses: actions/setup-go@v4
        with:
          go-version: '1.21'
          check-latest: true
      - name: Install Cosign
        uses: sigstore/cosign-installer@v3.5.0
        with:
          cosign-release: main
      - name: Check install!
        run: cosign version

This action does not need any GitHub permission to run, however, if your workflow needs to update, create or perform any action against your repository, then you should change the scope of the permission appropriately.

For example, if you are using the gcr.io as your registry to push the images you will need to give the write permission to the packages scope.

Example of a simple workflow:

jobs:
  build-image:
    runs-on: ubuntu-latest

    permissions:
      contents: read
      packages: write
      id-token: write # needed for signing the images with GitHub OIDC Token

    name: build-image
    steps:
      - uses: actions/checkout@v3.5.2
        with:
          fetch-depth: 1

      - name: Install Cosign
        uses: sigstore/cosign-installer@v3.5.0

      - name: Set up QEMU
        uses: docker/setup-qemu-action@v2.1.0

      - name: Set up Docker Buildx
        uses: docker/setup-buildx-action@v2.5.0

      - name: Login to GitHub Container Registry
        uses: docker/login-action@v2.1.0
        with:
          registry: ghcr.io
          username: ${{ github.actor }}
          password: ${{ secrets.GITHUB_TOKEN }}

      - id: docker_meta
        uses: docker/metadata-action@v4.4.0
        with:
          images: ghcr.io/sigstore/sample-honk
          tags: type=sha,format=long

      - name: Build and Push container images
        uses: docker/build-push-action@v4.0.0
        id: build-and-push
        with:
          platforms: linux/amd64,linux/arm/v7,linux/arm64
          push: true
          tags: ${{ steps.docker_meta.outputs.tags }}

      # https://docs.github.com/en/actions/security-guides/security-hardening-for-github-actions#using-an-intermediate-environment-variable
      - name: Sign image with a key
        run: |
          images=""
          for tag in ${TAGS}; do
            images+="${tag}@${DIGEST} "
          done
          cosign sign --yes --key env://COSIGN_PRIVATE_KEY ${images}
        env:
          TAGS: ${{ steps.docker_meta.outputs.tags }}
          COSIGN_PRIVATE_KEY: ${{ secrets.COSIGN_PRIVATE_KEY }}
          COSIGN_PASSWORD: ${{ secrets.COSIGN_PASSWORD }}
          DIGEST: ${{ steps.build-and-push.outputs.digest }}

      - name: Sign the images with GitHub OIDC Token
        env:
          DIGEST: ${{ steps.build-and-push.outputs.digest }}
          TAGS: ${{ steps.docker_meta.outputs.tags }}
        run: |
          images=""
          for tag in ${TAGS}; do
            images+="${tag}@${DIGEST} "
          done
          cosign sign --yes ${images}

Optional Inputs

The following optional inputs:

Input	Description
cosign-release	cosign version to use instead of the default.
install-dir	directory to place the cosign binary into instead of the default ($HOME/.cosign).
use-sudo	set to true if install-dir location requires sudo privs. Defaults to false.

Security

Should you discover any security issues, please refer to Sigstore's security process