image-deployer.yml

name: Deployment policy evaluator

permissions:
  contents: read

defaults:
  run:
    shell: bash

on:
  workflow_call:
    secrets:
      registry-username:
        description: "Username to log into the container registry."
      registry-password:
        description: "Password to log in the container registry."

    inputs:
      image:
        description: "The OCI image name. This must not include a tag or digest."
        required: true
        type: string
      digest:
        description: "The OCI image digest. The image digest of the form '<algorithm>:<digest>' (e.g. 'sha256:abcdef...')"
        required: true
        type: string
      registry-username:
        description: "Username to log into the container registry."
        type: string
      policy-id:
        description: "The policy ID to evaluate. This is the unique path for the policy file under policies/deployment. Example: servers-dev.json, myproject/mycluster-prod.json, etc."
        type: string
      continue-on-error:
        description: "Prevents a workflow run from failing when a job fails. Set to 'true' to allow a workflow run to pass when a job fails."
        required: false
        type: boolean
        default: false

    outputs:
      outcome:
        description: "The outcome status of the run ('success' or 'failure')."
        value: ${{ jobs.final.outputs.outcome }}

jobs:
  # detect-env detects the reusable workflow's repository and ref for use later
  # in the workflow.
  detect-env:
    outputs:
      outcome: ${{ steps.final.outputs.outcome }}
      repository: ${{ steps.detect.outputs.repository }}
      ref: ${{ steps.detect.outputs.ref }}
    runs-on: ubuntu-latest
    permissions:
      id-token: write # Needed to detect the current reusable repository and ref.
    steps:
      - name: Detect the generator ref
        id: detect
        continue-on-error: true
        uses: slsa-framework/slsa-github-generator/.github/actions/detect-workflow-js@v1.9.0

      - name: Final outcome
        id: final
        env:
          SUCCESS: ${{ steps.detect.outcome != 'failure' }}
        run: |
          set -euo pipefail
          echo "outcome=$([ "$SUCCESS" == "true" ] && echo "success" || echo "failure")" >> "$GITHUB_OUTPUT"

  # evaluate evaluates the publish policy.
  evaluate:
    needs: [detect-env]
    outputs:
      outcome: ${{ steps.final.outputs.outcome }}
    runs-on: ubuntu-latest
    permissions:
      id-token: write # for creating OIDC tokens for signing.
      packages: write # for uploading attestations.
      contents: read # To read the repo.
    steps:
      - name: Checkout this repository
        id: checkout
        continue-on-error: true
        uses: actions/checkout@c85c95e3d7251135ab7dc9ce3241c5835cc595a9 # v3.5.3
        with:
          repository: "${{ needs.detect-env.outputs.repository }}"
          ref: "${{ needs.detect-env.outputs.ref }}"
          token: "${{ github.token }}"
          persist-credentials: false
          fetch-depth: 1
      - name: Log-in the registry
        id: login
        continue-on-error: true
        uses: docker/login-action@49ed152c8eca782a232dede0303416e8f356c37b # v2.0.0
        with:
          # Use docker to simpliy local testing.
          registry: docker.io
          username: ${{ inputs.registry-username || secrets.registry-username }}
          password: ${{ secrets.registry-password }}
      - uses: actions/checkout@c85c95e3d7251135ab7dc9ce3241c5835cc595a9 # v3.5.3
        with:
          repository: "${{ needs.detect-env.outputs.repository }}"
          ref: "${{ needs.detect-env.outputs.ref }}"
          token: "${{ github.token }}"
          persist-credentials: false
          fetch-depth: 1
      - name: Install policy evaluator
        id: install
        continue-on-error: true
        uses: slsa-framework/slsa-policy/actions/installer@v0.0.1
      - id: evaluate
        continue-on-error: true
        env:
          POLICY_ID: ${{ inputs.policy-id }}
          IMAGE: "${{ inputs.image }}@${{ inputs.digest }}"
        working-directory: policies/deployment
        run: |
          set -euo pipefail
          slsa-policy deployment evaluate org.json . "${IMAGE}" "${POLICY_ID}"
          # NOTE: We can verify with:
          # cosign verify-attestation "${IMAGE}" --certificate-oidc-issuer https://token.actions.githubusercontent.com --certificate-identity "${DEPLOYER_ID}" --type https://slsa.dev/deployment/v0.1 | jq -r '.payload' | base64 -d | jq
      - name: Final outcome
        id: final
        env:
          SUCCESS: ${{ steps.checkout.outcome != 'failure' && steps.install.outcome != 'failure' && steps.login.outcome != 'failure' && steps.evaluate.outcome != 'failure' }}
        run: |
          set -euo pipefail
          echo "outcome=$([ "$SUCCESS" == "true" ] && echo "success" || echo "failure")" >> "$GITHUB_OUTPUT"

  # final fails or succeeds based on the value of `inputs.continue-on-error`
  # and the outcome of previous jobs.
  final:
    outputs:
      outcome: ${{ steps.final.outputs.outcome }}
    runs-on: ubuntu-latest
    needs: [detect-env, evaluate]
    # Note: always run even if needed jobs are skipped.
    if: always()
    steps:
      - name: Final outcome
        id: final
        env:
          SUCCESS: ${{ needs.detect-env.outputs.outcome != 'failure' && needs.evaluate.outputs.outcome != 'failure' }}
          CONTINUE: ${{ inputs.continue-on-error }}
        run: |
          set -euo pipefail
          echo "outcome=$([ "$SUCCESS" == "true" ] && echo "success" || echo "failure")" >> "$GITHUB_OUTPUT"
          [ "$CONTINUE" == "true" ] || [ "$SUCCESS" == "true" ] || exit 27