fix(webpush): recover gracefully from corrupted or mismatched VAPID keys

lib/WebPushClient.php

@@ -66,8 +66,14 @@ private function getClient(): WebPush {
 	 */
 	private function getVapid(): array {
 		// Do not use lazy for now
-		$publicKey = $this->appConfig->getAppValueString('webpush_vapid_pubkey');
-		$privateKey = $this->appConfig->getAppValueString('webpush_vapid_privkey');
+		try {
+			$publicKey = $this->appConfig->getAppValueString('webpush_vapid_pubkey');
+			$privateKey = $this->appConfig->getAppValueString('webpush_vapid_privkey');
+		} catch (\Throwable) {
+			// Decryption failed (e.g. mismatched instance secret), regenerate keys
+			$publicKey = '';
+			$privateKey = '';
+		}
 		if ($publicKey === '' || $privateKey === '') {
 			/** @var array{publicKey: string, privateKey: string} $vapid */
 			$vapid = VAPID::createVapidKeys();

tests/Unit/WebPushClientTest.php

@@ -0,0 +1,73 @@
+<?php
+
+declare(strict_types=1);
+
+/**
+ * SPDX-FileCopyrightText: 2026 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+
+namespace OCA\Notifications\Tests\Unit;
+
+use OCA\Notifications\WebPushClient;
+use OCP\AppFramework\Services\IAppConfig;
+use PHPUnit\Framework\MockObject\MockObject;
+use Test\TestCase;
+
+class WebPushClientTest extends TestCase {
+	protected IAppConfig&MockObject $appConfig;
+
+	protected function setUp(): void {
+		parent::setUp();
+		$this->appConfig = $this->createMock(IAppConfig::class);
+	}
+
+	public function testConstructSucceedsWhenVapidKeysAreStored(): void {
+		$this->appConfig->method('getAppValueString')
+			->willReturnMap([
+				['webpush_vapid_pubkey', '', false, 'BCVxsr7N_eNgVRqvHtD0zTZsEc6-VV-JvLexhqUzORcxaOzi6-AYWXvTBHm4bjyPjs7Vd8pZGH6SRpkNtoIAiw'],
+				['webpush_vapid_privkey', '', false, 'test-private-key'],
+			]);
+
+		$this->appConfig->expects($this->never())->method('setAppValueString');
+
+		$client = new WebPushClient($this->appConfig);
+		$this->assertInstanceOf(WebPushClient::class, $client);
+	}
+
+	public function testConstructRegeneratesVapidKeysWhenDecryptionFails(): void {
+		// Simulates the case where the stored VAPID keys were encrypted with a
+		// different instance secret — getAppValueString throws during decryption.
+		$this->appConfig->method('getAppValueString')
+			->willThrowException(new \RuntimeException('HMAC does not match.'));
+
+		$this->appConfig->expects($this->exactly(2))
+			->method('setAppValueString')
+			->with($this->logicalOr(
+				$this->equalTo('webpush_vapid_pubkey'),
+				$this->equalTo('webpush_vapid_privkey'),
+			));
+
+		// Must not throw — corrupted keys should be transparently regenerated
+		$client = new WebPushClient($this->appConfig);
+		$this->assertInstanceOf(WebPushClient::class, $client);
+	}
+
+	public function testConstructRegeneratesVapidKeysWhenMissing(): void {
+		$this->appConfig->method('getAppValueString')
+			->willReturnMap([
+				['webpush_vapid_pubkey', '', false, ''],
+				['webpush_vapid_privkey', '', false, ''],
+			]);
+
+		$this->appConfig->expects($this->exactly(2))
+			->method('setAppValueString')
+			->with($this->logicalOr(
+				$this->equalTo('webpush_vapid_pubkey'),
+				$this->equalTo('webpush_vapid_privkey'),
+			));
+
+		$client = new WebPushClient($this->appConfig);
+		$this->assertInstanceOf(WebPushClient::class, $client);
+	}
+}