Makefile: Add update-embedded-root rule (#1301)

* Makefile: Add update-embedded-root rule

This uses the "plumbing" command to ensure the newest root has been
downloaded and verified. Then it copies the newest TUF root and the
trusted_root.json into the sources. The benefit here is that one does
not need to manually find the cache directories when an update should
be done.

This hard codes XDG_DATA_HOME and XDG_CACHE_HOME for simplicity.

We could later add a workflow that runs this on cron and files an
issue if the sources changed as a result.

Signed-off-by: Jussi Kukkonen <jkukkonen@google.com>

* workflows: Create issue if TUF root is not up-to-date

Creates a new issue once a week if
* the embedded TUF root (or trusted_root.json) differs from the
  current one served by root-signing
* and there is no open issue with same label already

This does add a new CI-dependency (github-script) but I believe the
currently used actions do not provide the capabilities needed here.

The "embedded-root-update" label likely needs to be created by a
maintainer manually.

Signed-off-by: Jussi Kukkonen <jkukkonen@google.com>

---------

Signed-off-by: Jussi Kukkonen <jkukkonen@google.com>

Author: jku

.github/workflows/check-embedded-root.yml

@@ -0,0 +1,63 @@
+name: Check embedded root
+
+on:
+  workflow_dispatch:
+  schedule:
+    - cron: '13 13 * * 3'
+
+jobs:
+  check-embedded-root:
+    runs-on: ubuntu-latest
+    permissions:
+      issues: write
+
+    steps:
+      - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
+        with:
+          persist-credentials: false
+
+      - uses: actions/setup-python@42375524e23c412d93fb67b49958b491fce71c38 # v5.4.0
+        with:
+          python-version: "3.x"
+          cache: "pip"
+          cache-dependency-path: pyproject.toml
+
+      - name: Setup environment
+        run: make dev
+
+      - name: Check if embedded root is up-to-date
+        run: |
+          make update-embedded-root
+          git diff --exit-code
+
+
+      - if: failure()
+        name: Create an issue if embedded root is not up-to-date
+        uses: actions/github-script@60a0d83039c74a4aee543508d2ffcb1c3799cdea # v7.0.1
+        with:
+          script: |
+            const repo = context.repo.owner + "/" + context.repo.repo
+            const body = `
+            The Sigstore [TUF repository](https://tuf-repo-cdn.sigstore.dev/) contents have changed: the data embedded
+            in sigstore-python sources can be updated. This is not urgent but will improve cold-cache performance.
+            
+            Run \`make update-embedded-root\` to update the embedded data.
+            
+            This issue was filed by _${context.workflow}_ [workflow run](${context.serverUrl}/${repo}/actions/runs/${context.runId}).
+            `
+
+            const issues = await github.rest.search.issuesAndPullRequests({
+              q: "label:embedded-root-update+state:open+type:issue+repo:" + repo,
+            })
+            if (issues.data.total_count > 0) {
+              console.log("Issue for embedded root update exists already.")
+            } else {
+              github.rest.issues.create({
+                owner: context.repo.owner,
+                repo: context.repo.repo,
+                title: "Embedded TUF root is not up-to-date",
+                labels: ["embedded-root-update"],
+                body: body,
+              })
+              console.log("New issue created.")
+            }

Makefile

@@ -172,3 +172,11 @@ check-readme:
 .PHONY: edit
 edit:
 	$(EDITOR) $(ALL_PY_SRCS)
+
+update-embedded-root: $(VENV)/pyvenv.cfg
+	. $(VENV_BIN)/activate && \
+		python -m sigstore plumbing update-trust-root
+	cp ~/.local/share/sigstore-python/tuf/https%3A%2F%2Ftuf-repo-cdn.sigstore.dev/root.json \
+		sigstore/_store/prod/root.json
+	cp ~/.cache/sigstore-python/tuf/https%3A%2F%2Ftuf-repo-cdn.sigstore.dev/trusted_root.json \
+		sigstore/_store/prod/trusted_root.json