From 7c3e231ee6c124860ebbaa736b62768576825771 Mon Sep 17 00:00:00 2001
From: Trekky12 <thaegi@gmx.de>
Date: Sat, 8 Feb 2025 11:02:49 +0100
Subject: [PATCH] Fix showing owner of shared calendars on iOS

The iOS calendar uses the {DAV:}owner attribute to determine the owner
of a shared calendar.

Therefore this attribute needs to be set as the real owner of the
calendar not the user which whom the calendar is shared.
This "real" owner needs to be set before the ACL plugin can set it.

To determine the name of the owner the iOS calendar queries the principal uri.
Setting a mailto address is not working.

Unfortunatly the principal query is not allowed for other users by the
ACL plugin. It is not easy to determine if the client is trying to
query the principal information of a owner of a shared calendar, so as
workaround all authenticated users are allowed to query the principal information.
---
 lib/CalDAV/Backend/PDO.php      | 10 +++++++---
 lib/CalDAV/Principal/User.php   | 16 ++++++++++++++++
 lib/CalDAV/SharedCalendar.php   | 12 ++++++++++++
 lib/CalDAV/SharingPlugin.php    | 10 +++++++++-
 lib/DAV/Sharing/ISharedNode.php |  9 +++++++++
 5 files changed, 53 insertions(+), 4 deletions(-)

diff --git a/lib/CalDAV/Backend/PDO.php b/lib/CalDAV/Backend/PDO.php
index 91b5da4411..b6d59b1690 100644
--- a/lib/CalDAV/Backend/PDO.php
+++ b/lib/CalDAV/Backend/PDO.php
@@ -192,9 +192,13 @@ public function getCalendarsForUser($principalUri)
             $calendar['share-access'] = (int) $row['access'];
             // 1 = owner, 2 = readonly, 3 = readwrite
             if ($row['access'] > 1) {
-                // We need to find more information about the original owner.
-                //$stmt2 = $this->pdo->prepare('SELECT principaluri FROM ' . $this->calendarInstancesTableName . ' WHERE access = 1 AND id = ?');
-                //$stmt2->execute([$row['id']]);
+                $ownerStmt = $this->pdo->prepare("SELECT principaluri FROM {$this->calendarInstancesTableName} WHERE access = 1 AND calendarid = ?");
+                $ownerStmt->execute([$row['calendarid']]);
+
+                $ownerRow = $ownerStmt->fetch(\PDO::FETCH_ASSOC);
+                if ($ownerRow && is_array($ownerRow) && array_key_exists('principaluri', $ownerRow)) {
+                    $calendar['owner-principal'] = $ownerRow['principaluri'];
+                }
 
                 // read-only is for backwards compatibility. Might go away in
                 // the future.
diff --git a/lib/CalDAV/Principal/User.php b/lib/CalDAV/Principal/User.php
index 88bf4b4f77..3973d56648 100644
--- a/lib/CalDAV/Principal/User.php
+++ b/lib/CalDAV/Principal/User.php
@@ -131,6 +131,22 @@ public function getACL()
             'protected' => true,
         ];
 
+        /**
+         * Members of shared calendars needs to be able to read information about the owner.
+         * 
+         * The Principal has no knowledge about the calendars and therefore it is not 
+         * possible to limit the access to members of a shared calendar 
+         * in DAVACL/Plugin.php getCurrentUserPrivilegeSet.
+         * 
+         * As workaround all authenticated users are getting the read privilege for other users.
+         */
+
+         $acl[] = [
+            'privilege' => '{DAV:}read',
+            'principal' => '{DAV:}authenticated',
+            'protected' => true,
+        ];
+
         return $acl;
     }
 }
diff --git a/lib/CalDAV/SharedCalendar.php b/lib/CalDAV/SharedCalendar.php
index 818392f57c..cd1eefbe92 100644
--- a/lib/CalDAV/SharedCalendar.php
+++ b/lib/CalDAV/SharedCalendar.php
@@ -216,4 +216,16 @@ public function getChildACL()
 
         return $acl;
     }
+
+    /**
+     * Returns the 'original owner principal' for this shared resource.
+     *
+     * This must be a url to a principal, or null if there's no owner
+     *
+     * @return string|null
+     */
+    public function getOwnerPrincipal()
+    {
+        return isset($this->calendarInfo['owner-principal']) ? $this->calendarInfo['owner-principal'] : $this->getOwner();
+    }
 }
diff --git a/lib/CalDAV/SharingPlugin.php b/lib/CalDAV/SharingPlugin.php
index 56962fc14f..cc0bbf8f62 100644
--- a/lib/CalDAV/SharingPlugin.php
+++ b/lib/CalDAV/SharingPlugin.php
@@ -86,7 +86,7 @@ public function initialize(DAV\Server $server)
         $this->server->xml->elementMap['{'.Plugin::NS_CALENDARSERVER.'}share'] = \Sabre\CalDAV\Xml\Request\Share::class;
         $this->server->xml->elementMap['{'.Plugin::NS_CALENDARSERVER.'}invite-reply'] = \Sabre\CalDAV\Xml\Request\InviteReply::class;
 
-        $this->server->on('propFind', [$this, 'propFindEarly']);
+        $this->server->on('propFind', [$this, 'propFindEarly'], 10);
         $this->server->on('propFind', [$this, 'propFindLate'], 150);
         $this->server->on('propPatch', [$this, 'propPatch'], 40);
         $this->server->on('method:POST', [$this, 'httpPost']);
@@ -106,6 +106,14 @@ public function propFindEarly(DAV\PropFind $propFind, DAV\INode $node)
                     $node->getInvites()
                 );
             });
+
+            // Needs to be called before ACL
+            $propFind->handle('{DAV:}owner', function () use ($node) {
+                $shareAccess = $node->getShareAccess();
+                if ($shareAccess > 1) {
+                    return new \Sabre\DAV\Xml\Property\Href($node->getOwnerPrincipal() . '/');
+                }
+            });
         }
     }
 
diff --git a/lib/DAV/Sharing/ISharedNode.php b/lib/DAV/Sharing/ISharedNode.php
index a746ac7535..9d1e261513 100644
--- a/lib/DAV/Sharing/ISharedNode.php
+++ b/lib/DAV/Sharing/ISharedNode.php
@@ -66,4 +66,13 @@ public function updateInvites(array $sharees);
      * @return \Sabre\DAV\Xml\Element\Sharee[]
      */
     public function getInvites();
+
+    /**
+     * Returns the 'original owner principal' for this shared resource.
+     *
+     * This must be a url to a principal, or null if there's no owner
+     *
+     * @return string|null
+     */
+    public function getOwnerPrincipal();
 }