Fix/caldav option forgiving by tlilja · Pull Request #62090 · nextcloud/server

tlilja · 2026-07-14T12:23:29Z

Resolves: [Bug]: Parse error: Invalid Mimedir file #45574
Resolves: ICS import fails - OPTION_FORGIVING should handle underscores #16679
May help also in Error when accepting a calendar invite on Thunderbird: Processing message failed. Status: 80004005. #17915

Summary

This is a self-contained PR that adds support for using SabreDAV's OPTION_FORGIVING when dav.forigiving_ical_parser config option is set to allow non-standard ICS events parsed instead of giving error.

For example, Outlook on Mac, under certain conditions, generates ICS events that have invalid key X-ENTOURAGE_UID (underscore should be dash) which get rejected by Nextcloud/SabreDAV's strict parser by default.

This PR requires no changes to SabreDAV unlike the closed PR nextcloud/3rdparty#902 which got subsequently pushed to SabreDAV (sabre-io/dav#1563)

This PR includes unit tests and all DAV tests pass with the changes.

A bit problematic part of this PR is that overriding \Sabre\CalDAV\Plugin::validateICalendar() just to replace the VObject\Reader::read() call which is prone to error if SabreDAV changes their validateICalendar(). A better approach would be to refactor \Sabre\CalDAV\Plugin to allow overriding only the VObject\Reader::read() invocationa arguments with a hook but that would require changes on SabreDAV side whereas this is fully self-contained to Nextcloud.

TODO

Add documentation

Checklist

Code is properly formatted
Sign-off message is added to all commits
Tests (unit, integration, api and/or acceptance) are included
Screenshots before/after for front-end changes
Documentation (manuals or wiki) has been updated or is not required
Backports requested where applicable (ex: critical bugfixes)
Labels added where applicable (ex: bug/enhancement, 3. to review, feature component)
Milestone added for target branch/version (ex: 32.x for stable32)

AI (if applicable)

The content of this PR was partly or fully generated using AI

SebastianKrupinski · 2026-07-14T13:07:22Z

+	private function getReaderOptions(): int {
+		return $this->config->getSystemValueBool('dav.forgiving_ical_parser', false)
+			? Reader::OPTION_FORGIVING
+			: 0;
+	}
 }


This should be an import option, not a system configuration value

Okay, that makes sense, ImportOption is a better approach for andling the ImportService code path, but what about the main problem this PR is addressing, i.e., if I get the non-standard ICS from CalDAV PUT which goes through Plugin::validateICalendar?

Should the IConfig be used for that though?

We'll the issue you linked specifically states that the issue is with importing. Not with general PUT requests from a specific client, so I would not add a plugin to validate the events.

Also there is a PR that will fix a lot of this in the future.

#55178
nextcloud/calendar#8483

SebastianKrupinski · 2026-07-14T13:09:07Z


 		$calendarObjects = array_map(function ($o) use ($options) {
-			$calendarData = Reader::read($o['calendardata']);
+			$calendarData = Reader::read($o['calendardata'], $this->getReaderOptions());


This is not needed, once the data is read the first time with the forgiving flag, it should not need to be read with this flag.

SebastianKrupinski · 2026-07-14T13:09:22Z

 	 */
 	public function getDenormalizedData(string $calendarData): array {
-		$vObject = Reader::read($calendarData);
+		$vObject = Reader::read($calendarData, $this->getReaderOptions());


Same as above

SebastianKrupinski · 2026-07-14T13:14:03Z

@@ -3843,7 +3843,13 @@ public function moveCalendar($uriName, $uriOrigin, $uriDestination, $newUriName
 	 * @return VCalendar
 	 */
 	protected function readCalendarData($objectData) {


Same as above

SebastianKrupinski · 2026-07-14T13:16:24Z

 						$vObject->add(clone $timezones[$zone]);
 					}
 				}
 				yield $vObject;


In general, once the object is read, once, the correct object exists and is serialized back to a proper object, it should not need to be run using the flag.

Fair enough, I should have referred to case #45574 as the main issue instead of #16679 (I just updated the description to reflect this.).

For me, the main problem is that my users receive non-standard ICS invites by email (usually coming from Outlook) and hence the PR.

Fixing the import seemed like a logical thing to do as well, but perhaps I should drop this and open a new PR that addresees just this `CalDAV PUT' and case #45574.

Event updates are not handled by any of the code in this PR. so this would not fix your issue.

Also the most likely issue with Outook invitations is a missing Organizer property. which I already made a work around for.

Can you share one of the non working invitations with me?

test-entourage.ics.txt

I attached an ICS file that gives 415 Unsupported Media Type error when CalDAV PUT is done against master and 201 Created when done against fix/caldav-option-forgiving.

See also the transcript in https://gist.github.com/tlilja/2b3f7a26c816d730cd0d6a260cc77809

Okay, I see the issue the "X-ENTOURAGE_UUID" property has a underscore.

How is the CalDav put done? A import?

I believe the CalDAV PUT handling is done by apps/dav/lib/CalDav/Plugin.php, specifically VObject\Reader::read() call in Plugin.php:65 in this PR.

So the code path is different from Import which, though, invokes the same VObject\Reader::read().

That code in Plugin.php is the validation only.

The actual storing/updating the calendar events to the database is done by two CalDavBackend methods createCalendarObject() and updateCalendarObject() in apps/dav/lib/CalDav/CalDavBackend.php.

…g_ical_parser is set Clients such as Outlook for Mac produce property names with underscores (e.g. X-ENTOURAGE_UUID), which are invalid per RFC 5545 §3.2 and cause sabre to throw a ParseException, resulting in a 415 response. When the system config key dav.forgiving_ical_parser is true, pass Sabre\VObject\Reader::OPTION_FORGIVING to every Reader::read() call site in the CalDAV stack (Plugin::validateICalendar, CalDavBackend, ImportService). Non-conforming property names are then silently ignored rather than rejected. Assisted-by: ClaudeCode:claude-sonnet-4-6 Signed-off-by: Timo Lilja <timo.lilja@iki.fi>

…d and ImportService Assisted-by: ClaudeCode:claude-sonnet-4-6 Signed-off-by: Timo Lilja <timo.lilja@iki.fi>

tlilja requested review from a team, ChristophWurst, SebastianKrupinski and tcitworld as code owners July 14, 2026 12:23

tlilja requested review from Altahrim, ArtificialOwl, icewind1991 and provokateurin and removed request for a team July 14, 2026 12:23

tlilja force-pushed the fix/caldav-option-forgiving branch from a4141cf to dc5b8d5 Compare July 14, 2026 13:08

SebastianKrupinski requested changes Jul 14, 2026

View reviewed changes

Timo Lilja added 2 commits July 14, 2026 16:21

test(dav): add OPTION_FORGIVING tests for CalDAV Plugin, CalDavBacken…

28f91d2

…d and ImportService Assisted-by: ClaudeCode:claude-sonnet-4-6 Signed-off-by: Timo Lilja <timo.lilja@iki.fi>

tlilja force-pushed the fix/caldav-option-forgiving branch from dc5b8d5 to 28f91d2 Compare July 14, 2026 13:21

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tlilja Jul 14, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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tlilja Jul 14, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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tlilja commented Jul 14, 2026 •

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