publish-image.yml

name: Publish image

# Builds the reference sandbox image and pushes it to ghcr.
#
# openblox pulls an absent image on create, so publishing is what makes the
# default work on a host that has never seen it. A release tag publishes the
# matching image version; main publishes :edge so the tip is always testable
# without cutting a release.
#
# The digest is printed to the job summary. Pin THAT downstream, not the tag: an
# image is the sandbox's entire userland, and whoever controls the registry can
# repoint a tag.
#
# Every ${{ }} value is passed through env rather than interpolated into a run:
# script — workflow_dispatch inputs are attacker-controlled by anyone who can
# trigger the workflow, and this job holds a registry-write token.

on:
  pull_request:
    paths:
      - 'image/**'
      - '.github/workflows/publish-image.yml'
  push:
    branches: [main]
    paths:
      - 'image/**'
      - '.github/workflows/publish-image.yml'
    tags: ['v*']
  workflow_dispatch:
    inputs:
      tag:
        description: 'Version tag to publish (e.g. 0.1.0). Defaults to :edge.'
        type: string
        required: false

permissions:
  contents: read
  packages: write

concurrency:
  group: publish-image
  cancel-in-progress: false

defaults:
  run:
    shell: bash

jobs:
  # A pull request builds the image and asserts the contract, but never pushes.
  # Without this a broken Dockerfile is only discovered after it reaches main,
  # where the failure is a missing image rather than a red check.
  verify:
    name: Build & Verify
    if: github.event_name == 'pull_request'
    runs-on: ubuntu-latest
    timeout-minutes: 20
    steps:
      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1

      - uses: docker/setup-buildx-action@37fe631027851001ddb9b187196cc803df7f5f0e # v4.3.0

      # Single-platform and loaded into the local daemon: buildx cannot --load a
      # multi-platform manifest, and running the contract check matters more here
      # than proving both architectures build.
      - uses: docker/build-push-action@53b7df96c91f9c12dcc8a07bcb9ccacbed38856a # v7.3.0
        with:
          context: image
          platforms: linux/amd64
          push: false
          load: true
          tags: openblox-sandbox:pr
          cache-from: type=gha
          cache-to: type=gha,mode=max

      - name: Verify the contract
        run: |
          docker run --rm --entrypoint /bin/sh openblox-sandbox:pr -c \
            'command -v bash && command -v python3 && command -v nc && [ "$(id -u)" -ne 0 ]'

  publish:
    name: Build & Push
    if: github.event_name != 'pull_request'
    runs-on: ubuntu-latest
    timeout-minutes: 30
    steps:
      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1

      # Resolve the version BEFORE anything can push. A tag push publishes that
      # version plus :latest; anything else is :edge. A dispatch override is
      # validated, because it reaches a shell holding a write token.
      - name: Resolve tags
        id: meta
        env:
          TAG_INPUT: ${{ inputs.tag }}
          REF_NAME: ${{ github.ref_name }}
          REF_TYPE: ${{ github.ref_type }}
        run: |
          set -euo pipefail
          image="ghcr.io/${GITHUB_REPOSITORY_OWNER,,}/openblox-sandbox"

          version=""
          if [ -n "$TAG_INPUT" ]; then
            version="${TAG_INPUT#v}"
          elif [ "$REF_TYPE" = tag ]; then
            version="${REF_NAME#v}"
          fi

          if [ -n "$version" ]; then
            if ! printf '%s' "$version" | grep -Eq '^[0-9]+\.[0-9]+\.[0-9]+(-[0-9A-Za-z.-]+)?$'; then
              echo "refusing version '$version': expected semver like 1.2.3" >&2
              exit 1
            fi
            printf 'tags=%s:%s,%s:latest\n' "$image" "$version" "$image" >> "$GITHUB_OUTPUT"
          else
            printf 'tags=%s:edge\n' "$image" >> "$GITHUB_OUTPUT"
          fi

      - uses: docker/setup-qemu-action@96fe6ef7f33517b61c61be40b68a1882f3264fb8 # v4.2.0

      - uses: docker/setup-buildx-action@37fe631027851001ddb9b187196cc803df7f5f0e # v4.3.0

      - uses: docker/login-action@dbcb813823bdd20940b903addbd779551569679f # v4.6.0
        with:
          registry: ghcr.io
          username: ${{ github.actor }}
          password: ${{ secrets.GITHUB_TOKEN }}

      - name: Build and push
        id: push
        uses: docker/build-push-action@53b7df96c91f9c12dcc8a07bcb9ccacbed38856a # v7.3.0
        with:
          context: image
          # arm64 as well as amd64: Apple Silicon is where most people will try
          # this first, and emulating the whole sandbox to run a demo is not a
          # first impression worth having.
          platforms: linux/amd64,linux/arm64
          push: true
          tags: ${{ steps.meta.outputs.tags }}
          provenance: true
          sbom: true
          cache-from: type=gha
          cache-to: type=gha,mode=max

      # Smoke-test the published image against the contract the Dockerfile
      # asserts at build time. The build only proves it held on the BUILD
      # platform; this proves the pushed manifest runs.
      - name: Verify the pushed image
        env:
          TAGS: ${{ steps.meta.outputs.tags }}
        run: |
          set -euo pipefail
          ref="${TAGS%%,*}"
          docker pull "$ref"
          docker run --rm --entrypoint /bin/sh "$ref" -c \
            'command -v bash && command -v python3 && command -v nc && [ "$(id -u)" -ne 0 ]'
          echo "contract holds for $ref"

      - name: Report the digest to pin
        env:
          DIGEST: ${{ steps.push.outputs.digest }}
          TAGS: ${{ steps.meta.outputs.tags }}
        run: |
          {
            echo '## Sandbox image published'
            echo
            echo 'Tags:'
            echo
            printf '%s\n' "$TAGS" | tr ',' '\n' | sed 's/^/- `/; s/$/`/'
            echo
            echo 'Pin this digest rather than a tag:'
            echo
            echo '```'
            printf '%s@%s\n' "ghcr.io/${GITHUB_REPOSITORY_OWNER,,}/openblox-sandbox" "$DIGEST"
            echo '```'
          } >> "$GITHUB_STEP_SUMMARY"