feat: Add verify-signature plumbing and Temurin+Microsoft verification support (#1060)

* Add verify-signature plumbing and Temurin verification support

* Rebuild dist after signature verification changes

* Refine signature verification errors and regenerate dist

* refactor: make gpg.ts generic, move Adoptium-specific constant to temurin distribution

* fix: mock renameWinArchive in temurin tests and add signature e2e job

* refactor: bundle Adoptium public key, replace keyserver lookup with local import

* feat: add verify-signature-public-key input to allow custom GPG key override

* refactor: extract Adoptium public key to adoptium-key.ts; tighten gpg.ts cleanup scope

* Add verify-signature plumbing and Temurin verification support

* Potential fix for pull request finding

Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>

* Potential fix for pull request finding

Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>

* Add Microsoft signature verification support

* Regenerate dist bundles for Microsoft signature checks

* Harden Microsoft signature URL handling

* Add setup-java-microsoft-signature-verification e2e job

* chore: regenerate dist files

* Fix e2e-versions: remove duplicate job, update signature jobs to checkout@v7 with env vars

* Fix Prettier formatting in test files

* fix: mock renameWinArchive in microsoft-installer tests to fix Windows CI failure

* fix: use --homedir flag instead of GNUPGHOME env var for Windows GPG compatibility

The Git-bundled GPG on Windows (MSYS2-based) does not automatically convert
Windows-style paths in environment variables like GNUPGHOME. This caused GPG
to fail with exit code 2 when verifying Microsoft JDK signatures on Windows,
because the GNUPGHOME path (D:\a\_temp\...) was not recognized as a valid
POSIX path.

Fix: pass --homedir as an explicit command-line argument to both gpg --import
and gpg --verify. MSYS2 does correctly convert Windows paths in command-line
arguments, so this approach works reliably on Windows, Linux, and macOS.

* fix: convert Windows paths to POSIX format for MSYS2 GPG on Windows

The Git-bundled GPG on Windows (C:\Program Files\Git\usr\bin\gpg.exe) is
an MSYS2-based binary that uses POSIX path conventions internally. When
Windows-style paths with backslashes and drive letters (D:\a\_temp\...)
are passed as arguments, GPG may fail to resolve them correctly, resulting
in a fatal error (exit code 2).

Fix: add a toGpgPath() helper that converts Windows paths to MSYS2 POSIX
format (/d/a/_temp/...) before passing them to any gpg command. On Linux
and macOS the helper is a no-op.

Applied to all four paths used in verifyPackageSignature:
- gpgHome (--homedir argument)
- publicKeyFile (--import argument)
- signaturePath (--verify signature argument)
- archivePath (--verify data argument)

* Fix gpg test formatting

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>
Co-authored-by: Bruno Borges <brborges@microsoft.com>

src/gpg.ts

@@ -2,6 +2,7 @@ import * as fs from 'fs';
 import * as path from 'path';
 import * as io from '@actions/io';
 import * as exec from '@actions/exec';
+import * as tc from '@actions/tool-cache';
 import * as util from './util';
 import {ExecOptions} from '@actions/exec/lib/interfaces';
 
@@ -9,6 +10,17 @@ export const PRIVATE_KEY_FILE = path.join(util.getTempDir(), 'private-key.asc');
 
 const PRIVATE_KEY_FINGERPRINT_REGEX = /\w{40}/;
 
+// Convert a Windows path (D:\a\_temp\...) to a POSIX path (/d/a/_temp/...).
+// The Git-bundled GPG on Windows (MSYS2-based) uses POSIX path conventions
+// internally. Passing Windows paths with backslashes can cause fatal GPG errors
+// (exit code 2), so all paths passed to GPG must be in POSIX format on Windows.
+export function toGpgPath(p: string): string {
+  if (process.platform !== 'win32') return p;
+  return p
+    .replace(/\\/g, '/')
+    .replace(/^([A-Za-z]):\//, (_, drive) => `/${drive.toLowerCase()}/`);
+}
+
 export async function importKey(privateKey: string) {
   fs.writeFileSync(PRIVATE_KEY_FILE, privateKey, {
     encoding: 'utf-8',
@@ -53,3 +65,59 @@ export async function deleteKey(keyFingerprint: string) {
     }
   );
 }
+
+export async function verifyPackageSignature(
+  archivePath: string,
+  signatureUrl: string,
+  publicKeyContent: string
+) {
+  const signaturePath = await tc.downloadTool(signatureUrl);
+  let gpgHome: string;
+  try {
+    gpgHome = fs.mkdtempSync(
+      path.join(util.getTempDir(), 'verify-signature-gpg-home-')
+    );
+  } catch (error) {
+    try {
+      await io.rmRF(signaturePath);
+    } catch {
+      // ignore cleanup failures
+    }
+    throw new Error(
+      `Failed to create temporary GPG home directory for signature verification: ${
+        (error as Error).message
+      }`
+    );
+  }
+  try {
+    const publicKeyFile = path.join(gpgHome, 'public-key.asc');
+    fs.writeFileSync(publicKeyFile, publicKeyContent, {encoding: 'utf-8'});
+    const options: ExecOptions = {silent: true};
+    await exec.exec(
+      'gpg',
+      [
+        '--homedir',
+        toGpgPath(gpgHome),
+        '--batch',
+        '--import',
+        toGpgPath(publicKeyFile)
+      ],
+      options
+    );
+    await exec.exec(
+      'gpg',
+      [
+        '--homedir',
+        toGpgPath(gpgHome),
+        '--batch',
+        '--verify',
+        toGpgPath(signaturePath),
+        toGpgPath(archivePath)
+      ],
+      options
+    );
+  } finally {
+    await io.rmRF(signaturePath);
+    await io.rmRF(gpgHome);
+  }
+}