sigstore: always set TSA server endpoint to provide trusted timestamping

Signed-off-by: CrazyMax <1951866+crazy-max@users.noreply.github.com>

__tests__/sigstore/sigstore.test.itg.ts

@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-import {describe, expect, it} from '@jest/globals';
+import {describe, expect, jest, it} from '@jest/globals';
 import fs from 'fs';
 import * as path from 'path';
 
@@ -24,6 +24,9 @@ const fixturesDir = path.join(__dirname, '..', '.fixtures');
 
 const maybe = process.env.GITHUB_ACTIONS && process.env.GITHUB_ACTIONS === 'true' && process.env.ACTIONS_ID_TOKEN_REQUEST_URL && process.env.ImageOS && process.env.ImageOS.startsWith('ubuntu') ? describe : describe.skip;
 
+// needs current GitHub repo info
+jest.unmock('@actions/github');
+
 maybe('signProvenanceBlobs', () => {
   it('single platform', async () => {
     const sigstore = new Sigstore();

src/sigstore/sigstore.ts

@@ -18,18 +18,22 @@ import {X509Certificate} from 'crypto';
 import fs from 'fs';
 import path from 'path';
 
-import {signingEndpoints, SigstoreInstance} from '@actions/attest/lib/endpoints';
+import {Endpoints} from '@actions/attest/lib/endpoints';
 import * as core from '@actions/core';
 import {signPayload} from '@actions/attest/lib/sign';
 import {bundleToJSON} from '@sigstore/bundle';
 import {Attestation} from '@actions/attest';
 import {Bundle} from '@sigstore/sign';
 
-import {Subject} from '../types/intoto/intoto';
+import {GitHub} from '../github';
+
+import {MEDIATYPE_PAYLOAD as intotoMediatypePayload, Subject} from '../types/intoto/intoto';
+import {FULCIO_URL, REKOR_URL, SEARCH_URL, TSASERVER_URL} from '../types/sigstore/sigstore';
 
 export interface SignProvenanceBlobsOpts {
   localExportDir: string;
   name?: string;
+  noTransparencyLog?: boolean;
 }
 
 export interface SignProvenanceBlobsResult extends Attestation {
@@ -38,9 +42,6 @@ export interface SignProvenanceBlobsResult extends Attestation {
 }
 
 export class Sigstore {
-  private intotoPayloadType = 'application/vnd.in-toto+json';
-  private searchSigstoreURL = 'https://search.sigstore.dev';
-
   public async signProvenanceBlobs(opts: SignProvenanceBlobsOpts): Promise<Record<string, SignProvenanceBlobsResult>> {
     const result: Record<string, SignProvenanceBlobsResult> = {};
     try {
@@ -48,8 +49,7 @@ export class Sigstore {
         throw new Error('missing "id-token" permission. Please add "permissions: id-token: write" to your workflow.');
       }
 
-      const sigstoreInstance: SigstoreInstance = 'public-good';
+      const endpoints = this.signingEndpoints(opts);
-      const endpoints = signingEndpoints(sigstoreInstance);
       core.info(`Using Sigstore signing endpoint: ${endpoints.fulcioURL}`);
 
       const provenanceBlobs = Sigstore.getProvenanceBlobs(opts);
@@ -65,7 +65,7 @@ export class Sigstore {
           const bundle = await signPayload(
             {
               body: blob,
-              type: this.intotoPayloadType
+              type: intotoMediatypePayload
             },
             endpoints
           );
@@ -76,7 +76,7 @@ export class Sigstore {
             core.info(`  - ${subject.name} (${digestAlg}:${digestValue})`);
           }
           if (attest.tlogID) {
-            core.info(`Attestation signature uploaded to Rekor transparency log: ${this.searchSigstoreURL}?logIndex=${attest.tlogID}`);
+            core.info(`Attestation signature uploaded to Rekor transparency log: ${SEARCH_URL}?logIndex=${attest.tlogID}`);
           }
           core.info(`Writing Sigstore bundle to: ${bundlePath}`);
           fs.writeFileSync(bundlePath, JSON.stringify(attest.bundle, null, 2), {
@@ -95,6 +95,16 @@ export class Sigstore {
     return result;
   }
 
+  private signingEndpoints(opts: SignProvenanceBlobsOpts): Endpoints {
+    const noTransparencyLog = opts.noTransparencyLog ?? GitHub.context.payload.repository?.private;
+    core.info(`Upload to transparency log: ${noTransparencyLog ? 'disabled' : 'enabled'}`);
+    return {
+      fulcioURL: FULCIO_URL,
+      rekorURL: noTransparencyLog ? undefined : REKOR_URL,
+      tsaServerURL: TSASERVER_URL
+    };
+  }
+
   private static getProvenanceBlobs(opts: SignProvenanceBlobsOpts): Record<string, Buffer> {
     // For single platform build
     const singleProvenance = path.join(opts.localExportDir, 'provenance.json');

src/types/sigstore/sigstore.ts

@@ -0,0 +1,20 @@
+/**
+ * Copyright 2025 actions-toolkit 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.
+ */
+
+export const FULCIO_URL = 'https://fulcio.sigstore.dev';
+export const REKOR_URL = 'https://rekor.sigstore.dev';
+export const TSASERVER_URL = 'https://timestamp.sigstore.dev';
+export const SEARCH_URL = 'https://search.sigstore.dev';