Fix handling iTip replies with different address in From: and the iTip (Bifrost#T84315)

plugins/calendar/calendar.php

@@ -3063,14 +3063,17 @@ class calendar extends rcube_plugin
             // try to identify the attendee using the email sender address
             $existing_attendee        = -1;
             $existing_attendee_emails = array();
+
             foreach ($existing['attendees'] as $i => $attendee) {
               $existing_attendee_emails[] = $attendee['email'];
               if ($this->itip->compare_email($attendee['email'], $event['_sender'], $event['_sender_utf'])) {
                 $existing_attendee = $i;
               }
             }
+
             $event_attendee   = null;
             $update_attendees = array();
+
             foreach ($event['attendees'] as $attendee) {
               if ($this->itip->compare_email($attendee['email'], $event['_sender'], $event['_sender_utf'])) {
                 $event_attendee       = $attendee;
@@ -3078,6 +3081,7 @@ class calendar extends rcube_plugin
                 $metadata['fallback'] = $attendee['status'];
                 $metadata['attendee'] = $attendee['email'];
                 $metadata['rsvp']     = $attendee['rsvp'] || $attendee['role'] != 'NON-PARTICIPANT';
+
                 if ($attendee['status'] != 'DELEGATED') {
                   break;
                 }
@@ -3103,6 +3107,23 @@ class calendar extends rcube_plugin
               }
             }
 
+            // Accept sender as a new participant (different email in From: and the iTip)
+            // Use ATTENDEE entry from the iTip with replaced email address
+            if (!$event_attendee) {
+              // remove the organizer
+              $itip_attendees = array_filter($event['attendees'], function($item) { return $item['role'] != 'ORGANIZER'; });
+
+              // there must be only one attendee
+              if (is_array($itip_attendees) && count($itip_attendees) == 1) {
+                $event_attendee          = $itip_attendees[key($itip_attendees)];
+                $event_attendee['email'] = $event['_sender'];
+                $update_attendees[]      = $event_attendee;
+                $metadata['fallback']    = $event_attendee['status'];
+                $metadata['attendee']    = $event_attendee['email'];
+                $metadata['rsvp']        = $event_attendee['rsvp'] || $event_attendee['role'] != 'NON-PARTICIPANT';
+              }
+            }
+
             // found matching attendee entry in both existing and new events
             if ($existing_attendee >= 0 && $event_attendee) {
               $existing['attendees'][$existing_attendee] = $event_attendee;
@@ -3113,6 +3134,9 @@ class calendar extends rcube_plugin
               $existing['attendees'][] = $event_attendee;
               $success = $this->driver->update_attendees($existing, $update_attendees);
             }
+            else if (!$event_attendee) {
+              $error_msg = $this->gettext('errorunknownattendee');
+            }
             else {
               $error_msg = $this->gettext('newerversionexists');
             }

plugins/calendar/localization/en_US.inc

@@ -249,6 +249,7 @@ $labels['nowritecalendarfound'] = 'No calendar found to save the event';
 $labels['importedsuccessfully'] = 'The event was successfully added to \'$calendar\'';
 $labels['updatedsuccessfully'] = 'The event was successfully updated in \'$calendar\'';
 $labels['attendeupdateesuccess'] = 'Successfully updated the participant\'s status';
+$labels['errorunknownattendee'] = 'Failed to find the participant information.';
 $labels['itipsendsuccess'] = 'Invitation sent to participants.';
 $labels['itipresponseerror'] = 'Failed to send the response to this event invitation';
 $labels['itipinvalidrequest'] = 'This invitation is no longer valid';

plugins/libcalendaring/lib/libcalendaring_itip.php

@@ -613,6 +613,20 @@ class libcalendaring_itip
                 }
             }
 
+            // It may happen that sender's address is different in From: and the attached iTip
+            // In such case use the ATTENDEE entry with the address from From: header
+            if (empty($metadata['attendee']) && !empty($event['_sender'])) {
+                // remove the organizer
+                $itip_attendees = array_filter($event['attendees'], function($item) { return $item['role'] != 'ORGANIZER'; });
+
+                // there must be only one attendee
+                if (is_array($itip_attendees) && count($itip_attendees) == 1) {
+                    $event_attendee       = $itip_attendees[key($itip_attendees)];
+                    $metadata['attendee'] = $event['_sender'];
+                    $rsvp_status          = strtoupper($event_attendee['status']);
+                }
+            }
+
             // 1. update the attendee status on our copy
             $update_button = html::tag('input', array(
                 'type' => 'button',