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/distributions/temurin/installer.ts

@@ -4,7 +4,9 @@ import * as tc from '@actions/tool-cache';
 import fs from 'fs';
 import path from 'path';
 import semver from 'semver';
+import * as gpg from '../../gpg';
 
+import {ADOPTIUM_PUBLIC_KEY} from './adoptium-key';
 import {JavaBase} from '../base-installer';
 import {ITemurinAvailableVersions} from './models';
 import {
@@ -22,6 +24,8 @@ import {
   validatePaginationUrl
 } from '../../util';
 
+export {ADOPTIUM_PUBLIC_KEY} from './adoptium-key';
+
 export enum TemurinImplementation {
   Hotspot = 'Hotspot'
 }
@@ -50,7 +54,8 @@ export class TemurinDistribution extends JavaBase {
           : item.version_data.semver.replace('-beta+', '+');
         return {
           version: formattedVersion,
-          url: item.binaries[0].package.link
+          url: item.binaries[0].package.link,
+          signatureUrl: item.binaries[0].package.signature_link
         } as JavaDownloadRelease;
       });
 
@@ -80,6 +85,28 @@ export class TemurinDistribution extends JavaBase {
     );
     let javaArchivePath = await tc.downloadTool(javaRelease.url);
 
+    if (this.verifySignature) {
+      if (!javaRelease.signatureUrl) {
+        throw new Error(
+          `Input 'verify-signature' is enabled, but no signature URL was found for Temurin version ${javaRelease.version}.`
+        );
+      }
+      core.info(`Verifying Java package signature...`);
+      try {
+        await gpg.verifyPackageSignature(
+          javaArchivePath,
+          javaRelease.signatureUrl,
+          this.verifySignaturePublicKey ?? ADOPTIUM_PUBLIC_KEY
+        );
+      } catch (error) {
+        throw new Error(
+          `Failed to verify signature for Temurin version ${javaRelease.version} from ${javaRelease.signatureUrl}: ${
+            (error as Error).message
+          }`
+        );
+      }
+    }
+
     core.info(`Extracting Java archive...`);
     const extension = getDownloadArchiveExtension();
     if (process.platform === 'win32') {
@@ -105,6 +132,10 @@ export class TemurinDistribution extends JavaBase {
     return super.toolcacheFolderName;
   }
 
+  protected supportsSignatureVerification(): boolean {
+    return true;
+  }
+
   private async getAvailableVersions(): Promise<ITemurinAvailableVersions[]> {
     const platform = this.getPlatformOption();
     const arch = this.distributionArchitecture();