name: SLSA Level 3 Provenance

# Generates SLSA Level 3 provenance attestation for release artifacts.
# The attestation (.intoto.jsonl) is uploaded alongside release assets,
# providing cryptographically verifiable build provenance for Series-A
# supply-chain diligence and downstream consumer verification.
#
# SLSA generator pinned to slsa-framework/slsa-github-generator v2.1.0
# commit SHA: f7dd8c54c2067bafc12ca7a55595d5ee9b75204a (2025-02-24)
#
# IMPORTANT: This workflow changes release behavior — it generates a
# provenance attestation for every published release. Founder review
# required before merge.
#
# Verification: consumers can verify with:
#   slsa-verifier verify-artifact <artifact> \
#     --provenance-path <artifact>.intoto.jsonl \
#     --source-uri github.com/szl-holdings/amaru

on:
  release:
    types: [published]

permissions:
  id-token: write    # Required for SLSA provenance signing
  contents: write    # Required to upload attestation to release
  actions: read      # Required by SLSA generator to read workflow

jobs:
  # ---------------------------------------------------------------------------
  # 1. Build the release artifact and compute its hash.
  # ---------------------------------------------------------------------------
  build:
    name: Build release artifact
    runs-on: ubuntu-latest
    outputs:
      artifact-name: ${{ steps.set-output.outputs.artifact-name }}
      artifact-sha256: ${{ steps.hash.outputs.sha256 }}
    steps:
      - name: Checkout
        uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2

      - name: Create release archive
        id: set-output
        run: |
          set -euo pipefail
          ARTIFACT="amaru-${{ github.event.release.tag_name }}.tar.gz"
          # Package the repo source (adjust for language-specific build output)
          git archive --format=tar.gz \
            --prefix="amaru-${{ github.event.release.tag_name }}/" \
            HEAD \
            -o "$ARTIFACT"
          echo "artifact-name=$ARTIFACT" >> "$GITHUB_OUTPUT"

      - name: Compute SHA-256
        id: hash
        run: |
          set -euo pipefail
          ARTIFACT="${{ steps.set-output.outputs.artifact-name }}"
          SHA=$(sha256sum "$ARTIFACT" | awk '{print $1}')
          echo "sha256=$SHA" >> "$GITHUB_OUTPUT"
          echo "Artifact: $ARTIFACT"
          echo "SHA256:   $SHA"

      - name: Upload artifact for provenance job
        uses: actions/upload-artifact@ea165f8d65b6e75b540449e92b4886f43607fa02 # v4
        with:
          name: release-artifact
          path: ${{ steps.set-output.outputs.artifact-name }}
          retention-days: 1
          if-no-files-found: error

  # ---------------------------------------------------------------------------
  # 2. Generate SLSA Level 3 provenance attestation.
  #    This is a reusable workflow call — it runs in a separate job with
  #    hermetic build environment verification.
  # ---------------------------------------------------------------------------
  provenance:
    name: Generate SLSA provenance
    needs: [build]
    permissions:
      id-token: write
      contents: write
      actions: read
    uses: slsa-framework/slsa-github-generator/.github/workflows/generator_generic_slsa3.yml@f7dd8c54c2067bafc12ca7a55595d5ee9b75204a
    with:
      base64-subjects: ${{ needs.build.outputs.artifact-sha256 }}
      upload-assets: true
      provenance-name: amaru-${{ github.event.release.tag_name }}.intoto.jsonl