Skip to content

fix(dav): Strip DTSTAMP before etag comparison in webcal refresh #58193

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Open
Olen wants to merge 2 commits into
base: master
Choose a base branch
from
+74 −2
Open

fix(dav): Strip DTSTAMP before etag comparison in webcal refresh #58193

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
9645a3a
fix(dav): Strip DTSTAMP before etag comparison in RefreshWebcalService
Olen Feb 9, 2026
6d10452
fix(dav): strip DTSTAMP only from etag, preserve in stored data
Olen Feb 9, 2026
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
8 changes: 7 additions & 1 deletion apps/dav/lib/CalDAV/WebcalCaching/RefreshWebcalService.php
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -112,7 +112,13 @@ public function refreshSubscription(string $principalUri, string $uri) {

$sObject = $vObject->serialize();
$uid = $vBase->UID->getValue();
$etag = md5($sObject);
// Strip DTSTAMP lines for etag computation only.
// Many providers (Google Calendar, Outlook, itslearning) set DTSTAMP
// to the current time on every feed request per RFC 5545, causing
// every event to appear modified on every refresh.
// DTSTAMP is kept in the stored data as it is a required property.
$sObjectForEtag = preg_replace('/^DTSTAMP:.*\r?\n/m', '', $sObject);
Copy link
Member

@tcitworld tcitworld Feb 9, 2026

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

There is a risk that the line might be over 75 characters even in this case (for instance if we have a TZID), so I would handle content folding as well in the regex (new line must not be followed by a white-space character).

https://icalendar.org/iCalendar-RFC-5545/3-1-content-lines.html

$etag = md5($sObjectForEtag);

// No existing object with this UID, create it
if (!isset($existingObjects[$uid])) {
Expand Down
68 changes: 67 additions & 1 deletion apps/dav/tests/unit/CalDAV/WebcalCaching/RefreshWebcalServiceTest.php
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -460,9 +460,75 @@ public function testRunCreateCalendarBadRequest(string $body, string $format, st
$refreshWebcalService->refreshSubscription('principals/users/testuser', 'sub123');
}

public function testDtstampChangeDoesNotTriggerUpdate(): void {
$refreshWebcalService = new RefreshWebcalService(
$this->caldavBackend,
$this->logger,
$this->connection,
$this->timeFactory,
$this->importService
);

$this->caldavBackend->expects(self::once())
->method('getSubscriptionsForUser')
->with('principals/users/testuser')
->willReturn([
[
'id' => '42',
'uri' => 'sub123',
RefreshWebcalService::STRIP_TODOS => '1',
RefreshWebcalService::STRIP_ALARMS => '1',
RefreshWebcalService::STRIP_ATTACHMENTS => '1',
'source' => 'webcal://foo.bar/bla2',
'lastmodified' => 0,
],
]);

// Feed body has a new DTSTAMP (as happens on every fetch from Google/Outlook)
$body = "BEGIN:VCALENDAR\r\nVERSION:2.0\r\nPRODID:-//Test//Test//EN\r\nBEGIN:VEVENT\r\nUID:dtstamp-test\r\nDTSTAMP:20260209T120000Z\r\nDTSTART:20260301T100000Z\r\nSUMMARY:Test Event\r\nEND:VEVENT\r\nEND:VCALENDAR\r\n";
$stream = $this->createStreamFromString($body);

$this->connection->expects(self::once())
->method('queryWebcalFeed')
->willReturn(['data' => $stream, 'format' => 'ical']);

// The stored etag was computed from the DTSTAMP-stripped serialization
$existingEtag = md5(preg_replace('/^DTSTAMP:.*\r?\n/m', '', $body));

$this->caldavBackend->expects(self::once())
->method('getLimitedCalendarObjects')
->willReturn([
'dtstamp-test' => [
'id' => 1,
'uid' => 'dtstamp-test',
'etag' => $existingEtag,
'uri' => 'dtstamp-test.ics',
],
]);

$vCalendar = VObject\Reader::read($body);
$generator = function () use ($vCalendar) {
yield $vCalendar;
};

$this->importService->expects(self::once())
->method('importText')
->willReturn($generator());

// DTSTAMP-only change must NOT trigger an update
$this->caldavBackend->expects(self::never())
->method('updateCalendarObject');

$this->caldavBackend->expects(self::never())
->method('createCalendarObject');

$refreshWebcalService->refreshSubscription('principals/users/testuser', 'sub123');
}

public static function identicalDataProvider(): array {
$icalBody = "BEGIN:VCALENDAR\r\nVERSION:2.0\r\nPRODID:-//Sabre//Sabre VObject " . VObject\Version::VERSION . "//EN\r\nCALSCALE:GREGORIAN\r\nBEGIN:VEVENT\r\nUID:12345\r\nDTSTAMP:20160218T133704Z\r\nDTSTART;VALUE=DATE:19000101\r\nDTEND;VALUE=DATE:19000102\r\nRRULE:FREQ=YEARLY\r\nSUMMARY:12345's Birthday (1900)\r\nTRANSP:TRANSPARENT\r\nEND:VEVENT\r\nEND:VCALENDAR\r\n";
$etag = md5($icalBody);
// Etag is computed from DTSTAMP-stripped serialization
$etag = md5(preg_replace('/^DTSTAMP:.*\r?\n/m', '', $icalBody));

return [
[
Expand Down
Loading