feat: add GitHub Actions workflow to check pinned CA certificate validity

.github/workflows/security-utils-cert-validity.yaml

@@ -0,0 +1,112 @@
+name: Check pinned CA validity
+
+on:
+  schedule:
+    - cron: '0 3 * * *'
+  workflow_dispatch:
+  pull_request:
+    paths:
+      - '.github/workflows/security-utils-cert-validity.yaml'
+      - 'security-utils/certs/*.pem'
+
+permissions:
+  contents: read
+  issues: write
+
+jobs:
+  check-pinned-cas:
+    name: Check pinned CA validity
+    runs-on: ubuntu-24.04
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Check pinned CA certificates
+        id: cert_check
+        run: |
+          set -euo pipefail
+
+          threshold_seconds=$((60 * 24 * 60 * 60))
+          expiring_certs=()
+
+          for cert in security-utils/certs/*.pem; do
+            echo "Checking certificate validity for ${cert}"
+
+            if ! openssl x509 -in "${cert}" -noout >/dev/null; then
+              echo "::error file=${cert}::Invalid certificate format"
+              exit 1
+            fi
+
+            expiration="$(openssl x509 -in "${cert}" -noout -enddate | sed 's/notAfter=//')"
+            echo "${cert} notAfter=${expiration}"
+
+            if ! openssl x509 -in "${cert}" -checkend 0 -noout >/dev/null; then
+              echo "::error file=${cert}::Certificate is expired (notAfter=${expiration})"
+              exit 1
+            fi
+
+            if ! openssl x509 -in "${cert}" -checkend "${threshold_seconds}" -noout >/dev/null; then
+              echo "::error file=${cert}::Certificate expires in less than 60 days (notAfter=${expiration})"
+              expiring_certs+=("${cert} (notAfter=${expiration})")
+            fi
+          done
+
+          if ((${#expiring_certs[@]} > 0)); then
+            {
+              echo 'expiring_certs<<EOF'
+              printf '%s\n' "${expiring_certs[@]}"
+              echo EOF
+            } >>"$GITHUB_OUTPUT"
+
+            exit 1
+          fi
+
+      - name: Notify maintainers via GitHub issue
+        if: failure() && steps.cert_check.outputs.expiring_certs != ''
+        uses: actions/github-script@v7
+        with:
+          script: |
+            const title = 'security-utils pinned CA certificates expire in less than 60 days';
+            const body = [
+              'The nightly pinned CA validity workflow detected certificates expiring within 60 days.',
+              '',
+              'Please rotate affected certificates in `security-utils/certs`.',
+              '',
+              'Affected certificates:',
+              '```',
+              `${{ toJSON(steps.cert_check.outputs.expiring_certs) }}`,
+              '```',
+              '',
+              `Workflow run: ${context.serverUrl}/${context.repo.owner}/${context.repo.repo}/actions/runs/${context.runId}`,
+            ].join('\n');
+
+            const { data: issues } = await github.rest.issues.listForRepo({
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+              state: 'open',
+              creator: 'github-actions[bot]',
+              per_page: 100,
+            });
+
+            const existing = issues.find((issue) => issue.title === title);
+
+            if (existing) {
+              await github.rest.issues.createComment({
+                owner: context.repo.owner,
+                repo: context.repo.repo,
+                issue_number: existing.number,
+                body,
+              });
+              core.info(`Updated existing issue #${existing.number}`);
+              return;
+            }
+
+            const { data: issue } = await github.rest.issues.create({
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+              title,
+              body,
+              labels: ['security'],
+            });
+
+            core.info(`Created issue #${issue.number}`);