Use reusuable release workflow in sigstore/sigstore (#729)

Signed-off-by: Kenny Leung <kleung@chainguard.dev>

.github/workflows/cut-release.yml

+name: Cut Release
+
+on:
+  workflow_dispatch:
+    inputs:
+      release_tag:
+        required: true
+        type: string
+        description: 'Release tag'
+      key_ring:
+        required: true
+        type: string
+        description: 'Key ring for cosign key'
+      key_name:
+        required: true
+        type: string
+        description: 'Key name for cosign key'
+
+concurrency: cut-release
+
+jobs:
+  cut-release:
+    name: Cut release
+    uses: sigstore/sigstore/.github/workflows/reusable-release.yml@main
+    permissions:
+      id-token: write
+      contents: read
+    with:
+      release_tag: ${{ github.event.inputs.release_tag }}
+      key_ring: ${{ github.event.inputs.key_ring }}
+      key_name: ${{ github.event.inputs.key_name }}
+      workload_identity_provider: 'projects/498091336538/locations/global/workloadIdentityPools/githubactions/providers/sigstore-rekor'
+      service_account: 'github-actions-rekor@projectsigstore.iam.gserviceaccount.com'
+      repo: 'rekor'

hack/github-oidc-setup.sh

+#!/usr/bin/env bash
+
+# Copyright 2022 The Sigstore Authors
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# Idempotent script.
+#
+# Commands based off of Google blog post
+# https://cloud.google.com/blog/products/identity-security/enabling-keyless-authentication-from-github-actions
+#
+# One addition is the attribute.repository=assertion.repository mapping.
+# This allows it to be pinned to given repo.
+
+set -o errexit
+set -o nounset
+set -o pipefail
+set -o verbose
+set -o xtrace
+
+PROJECT_ID="projectsigstore"
+PROJECT_NUMBER="498091336538"
+POOL_NAME="githubactions"
+PROVIDER_NAME="sigstore-rekor"
+LOCATION="global"
+REPO="sigstore/rekor"
+SERVICE_ACCOUNT_ID="github-actions-rekor"
+SERVICE_ACCOUNT="${SERVICE_ACCOUNT_ID}@${PROJECT_ID}.iam.gserviceaccount.com"
+
+# Create workload identity pool if not present.
+if ! (gcloud iam workload-identity-pools describe "${POOL_NAME}" --location=${LOCATION}); then
+  gcloud iam workload-identity-pools create "${POOL_NAME}" \
+    --project="${PROJECT_ID}" \
+    --location="${LOCATION}" \
+    --display-name="Github Actions Pool"
+fi
+
+# Create workload identity provider if not present.
+if ! (gcloud iam workload-identity-pools providers describe "${PROVIDER_NAME}" --location="${LOCATION}" --workload-identity-pool="${POOL_NAME}"); then
+  gcloud iam workload-identity-pools providers create-oidc "${PROVIDER_NAME}" \
+  --project="${PROJECT_ID}" \
+  --location="${LOCATION}" \
+  --workload-identity-pool="${POOL_NAME}" \
+  --display-name="Github Actions Provider Rekor" \
+  --attribute-mapping="google.subject=assertion.sub,attribute.actor=assertion.actor,attribute.aud=assertion.aud,attribute.repository=assertion.repository" \
+  --issuer-uri="https://token.actions.githubusercontent.com"
+fi
+
+# Create service account if not present.
+if ! (gcloud iam service-accounts describe "${SERVICE_ACCOUNT}"); then
+gcloud iam service-accounts create ${SERVICE_ACCOUNT_ID} \
+  --description="Service account for Github Actions Rekor" \
+  --display-name="Github Actions Rekor"
+fi
+
+# Adding binding is idempotent.
+gcloud iam service-accounts add-iam-policy-binding "${SERVICE_ACCOUNT}" \
+  --project="${PROJECT_ID}" \
+  --role="roles/iam.workloadIdentityUser" \
+  --member="principalSet://iam.googleapis.com/projects/${PROJECT_NUMBER}/locations/${LOCATION}/workloadIdentityPools/${POOL_NAME}/attribute.repository/${REPO}"
+
+# Adding binding is idempotent.
+# Used for kicking off cloud build.
+gcloud projects add-iam-policy-binding "${PROJECT_ID}" \
+  --project="${PROJECT_ID}" \
+  --role="roles/cloudbuild.builds.editor" \
+  --member="serviceAccount:${SERVICE_ACCOUNT}"
+
+# Adding binding is idempotent.
+# Permission needed to run `gcloud builds`
+# https://cloud.google.com/build/docs/securing-builds/configure-access-to-resources#granting_permissions_to_run_gcloud_commands
+gcloud projects add-iam-policy-binding "${PROJECT_ID}" \
+  --project="${PROJECT_ID}" \
+  --role="roles/serviceusage.serviceUsageConsumer" \
+  --member="serviceAccount:${SERVICE_ACCOUNT}"