fix(imip): set charset for imip attachment

apps/dav/lib/CalDAV/Schedule/IMipPlugin.php

@@ -249,7 +249,6 @@ public function schedule(Message $iTipMessage) {
 		// convert iTip Message to string
 		$itip_msg = $iTipMessage->message->serialize();
 
-		$user = null;
 		$mailService = null;
 
 		try {
@@ -261,8 +260,14 @@ public function schedule(Message $iTipMessage) {
 					$mailService = $this->mailManager->findServiceByAddress($user->getUID(), $sender);
 				}
 			}
+
+			// The display name in Nextcloud can use utf-8.
+			// As the default charset for text/* is us-ascii, it's important to explicitly define it.
+			// See https://www.rfc-editor.org/rfc/rfc6047.html#section-2.4.
+			$contentType = 'text/calendar; method=' . $iTipMessage->method . '; charset="utf-8"';
+
 			// evaluate if a mail service was found and has sending capabilities
-			if ($mailService !== null && $mailService instanceof IMessageSend) {
+			if ($mailService instanceof IMessageSend) {
 				// construct mail message and set required parameters
 				$message = $mailService->initiateMessage();
 				$message->setFrom(
@@ -274,10 +279,12 @@ public function schedule(Message $iTipMessage) {
 				$message->setSubject($template->renderSubject());
 				$message->setBodyPlain($template->renderText());
 				$message->setBodyHtml($template->renderHtml());
+				// Adding name=event.ics is a trick to make the invitation also appear
+				// as a file attachment in mail clients like Thunderbird or Evolution.
 				$message->setAttachments((new Attachment(
 					$itip_msg,
 					null,
-					'text/calendar; name=event.ics; method=' . $iTipMessage->method,
+					$contentType . '; name=event.ics',
 					true
 				)));
 				// send message
@@ -293,10 +300,12 @@ public function schedule(Message $iTipMessage) {
 					(($senderName !== null) ? [$sender => $senderName] : [$sender])
 				);
 				$message->useTemplate($template);
+				// Using a different content type because Symfony Mailer/Mime will append the name to
+				// the content type header and attachInline does not allow null.
 				$message->attachInline(
 					$itip_msg,
 					'event.ics',
-					'text/calendar; method=' . $iTipMessage->method
+					$contentType,
 				);
 				$failed = $this->mailer->send($message);
 			}

apps/dav/tests/unit/CalDAV/Schedule/IMipPluginCharsetTest.php

@@ -0,0 +1,193 @@
+<?php
+
+declare(strict_types=1);
+/**
+ * SPDX-FileCopyrightText: 2025 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+
+namespace OCA\DAV\Tests\unit\CalDAV\Schedule;
+
+use OC\L10N\L10N;
+use OC\URLGenerator;
+use OCA\DAV\CalDAV\EventComparisonService;
+use OCA\DAV\CalDAV\Schedule\IMipPlugin;
+use OCA\DAV\CalDAV\Schedule\IMipService;
+use OCP\AppFramework\Utility\ITimeFactory;
+use OCP\Defaults;
+use OCP\IAppConfig;
+use OCP\IConfig;
+use OCP\IDBConnection;
+use OCP\IURLGenerator;
+use OCP\IUser;
+use OCP\IUserSession;
+use OCP\L10N\IFactory;
+use OCP\Mail\IMailer;
+use OCP\Mail\IMessage;
+use OCP\Mail\Provider\IManager;
+use OCP\Mail\Provider\IMessageSend;
+use OCP\Mail\Provider\IService;
+use OCP\Mail\Provider\Message as MailProviderMessage;
+use OCP\Security\ISecureRandom;
+use PHPUnit\Framework\MockObject\MockObject;
+use Psr\Log\LoggerInterface;
+use Psr\Log\NullLogger;
+use Sabre\VObject\Component\VCalendar;
+use Sabre\VObject\Component\VEvent;
+use Sabre\VObject\ITip\Message;
+use Sabre\VObject\Property\ICalendar\CalAddress;
+use Symfony\Component\Mime\Email;
+use Test\TestCase;
+
+class IMipPluginCharsetTest extends TestCase {
+	// Dependencies
+	private Defaults&MockObject $defaults;
+	private IAppConfig&MockObject $appConfig;
+	private IConfig&MockObject $config;
+	private IDBConnection&MockObject $db;
+	private IFactory $l10nFactory;
+	private IManager&MockObject $mailManager;
+	private IMailer&MockObject $mailer;
+	private ISecureRandom&MockObject $random;
+	private ITimeFactory&MockObject $timeFactory;
+	private IUrlGenerator&MockObject $urlGenerator;
+	private IUserSession&MockObject $userSession;
+	private LoggerInterface $logger;
+
+	// Services
+	private EventComparisonService $eventComparisonService;
+	private IMipPlugin $imipPlugin;
+	private IMipService $imipService;
+
+	// ITip Message
+	private Message $itipMessage;
+
+	protected function setUp(): void {
+		// Used by IMipService and IMipPlugin
+		$today = new \DateTime('2025-06-15 14:30');
+		$this->timeFactory = $this->createMock(ITimeFactory::class);
+		$this->timeFactory->method('getTime')
+			->willReturn($today->getTimestamp());
+		$this->timeFactory->method('getDateTime')
+			->willReturn($today);
+
+		// IMipService
+		$this->urlGenerator = $this->createMock(URLGenerator::class);
+		$this->config = $this->createMock(IConfig::class);
+		$this->db = $this->createMock(IDBConnection::class);
+		$this->random = $this->createMock(ISecureRandom::class);
+		$l10n = $this->createMock(L10N::class);
+		$this->l10nFactory = $this->createMock(IFactory::class);
+		$this->l10nFactory->method('findGenericLanguage')
+			->willReturn('en');
+		$this->l10nFactory->method('findLocale')
+			->willReturn('en_US');
+		$this->l10nFactory->method('get')
+			->willReturn($l10n);
+		$this->imipService = new IMipService(
+			$this->urlGenerator,
+			$this->config,
+			$this->db,
+			$this->random,
+			$this->l10nFactory,
+			$this->timeFactory,
+		);
+
+		// EventComparisonService
+		$this->eventComparisonService = new EventComparisonService();
+
+		// IMipPlugin
+		$this->appConfig = $this->createMock(IAppConfig::class);
+		$message = new \OC\Mail\Message(new Email(), false);
+		$this->mailer = $this->createMock(IMailer::class);
+		$this->mailer->method('createMessage')
+			->willReturn($message);
+		$this->mailer->method('validateMailAddress')
+			->willReturn(true);
+		$this->logger = new NullLogger();
+		$this->defaults = $this->createMock(Defaults::class);
+		$this->defaults->method('getName')
+			->willReturn('Instance Name 123');
+		$user = $this->createMock(IUser::class);
+		$user->method('getUID')
+			->willReturn('luigi');
+		$this->userSession = $this->createMock(IUserSession::class);
+		$this->userSession->method('getUser')
+			->willReturn($user);
+		$this->mailManager = $this->createMock(IManager::class);
+		$this->imipPlugin = new IMipPlugin(
+			$this->appConfig,
+			$this->mailer,
+			$this->logger,
+			$this->timeFactory,
+			$this->defaults,
+			$this->userSession,
+			$this->imipService,
+			$this->eventComparisonService,
+			$this->mailManager,
+		);
+
+		// ITipMessage
+		$calendar = new VCalendar();
+		$event = new VEvent($calendar, 'VEVENT');
+		$event->UID = 'uid-1234';
+		$event->SEQUENCE = 1;
+		$event->SUMMARY = 'Lunch';
+		$event->DTSTART = new \DateTime('2025-06-20 12:30:00');
+		$organizer = new CalAddress($calendar, 'ORGANIZER', 'mailto:luigi@example.org');
+		$event->add($organizer);
+		$attendee = new CalAddress($calendar, 'ATTENDEE', 'mailto:jose@example.org', ['RSVP' => 'TRUE', 'CN' => 'José']);
+		$event->add($attendee);
+		$calendar->add($event);
+		$this->itipMessage = new Message();
+		$this->itipMessage->method = 'REQUEST';
+		$this->itipMessage->message = $calendar;
+		$this->itipMessage->sender = 'mailto:luigi@example.org';
+		$this->itipMessage->senderName = 'Luigi';
+		$this->itipMessage->recipient = 'mailto:' . 'jose@example.org';
+	}
+
+	public function testCharsetMailer(): void {
+		// Arrange
+		$symfonyEmail = null;
+		$this->mailer->expects(self::once())
+			->method('send')
+			->willReturnCallback(function (IMessage $message) use (&$symfonyEmail): array {
+				if ($message instanceof \OC\Mail\Message) {
+					$symfonyEmail = $message->getSymfonyEmail();
+				}
+				return [];
+			});
+
+		// Act
+		$this->imipPlugin->schedule($this->itipMessage);
+
+		// Assert
+		$this->assertNotNull($symfonyEmail);
+		$body = $symfonyEmail->getBody()->toString();
+		$this->assertStringContainsString('Content-Type: text/calendar; method=REQUEST; charset="utf-8"; name=event.ics', $body);
+	}
+
+	public function testCharsetMailProvider(): void {
+		// Arrange
+		$this->appConfig->method('getValueBool')
+			->with('core', 'mail_providers_enabled', true)
+			->willReturn(true);
+		$mailMessage = new MailProviderMessage();
+		$mailService = $this->createStubForIntersectionOfInterfaces([IService::class, IMessageSend::class]);
+		$mailService->method('initiateMessage')
+			->willReturn($mailMessage);
+		$mailService->expects(self::once())
+			->method('sendMessage');
+		$this->mailManager->method('findServiceByAddress')
+			->willReturn($mailService);
+
+		// Act
+		$this->imipPlugin->schedule($this->itipMessage);
+
+		// Assert
+		$attachments = $mailMessage->getAttachments();
+		$this->assertCount(1, $attachments);
+		$this->assertStringContainsString('text/calendar; method=REQUEST; charset="utf-8"; name=event.ics', $attachments[0]->getType());
+	}
+}