Filter contacts from the local system addressbook - remote share with local users is not allowed

apps/dav/lib/carddav/addressbookimpl.php

@@ -214,6 +214,10 @@ class AddressBookImpl implements IAddressBook {
 		foreach ($vCard->children as $property) {
 			$result[$property->name] = $property->getValue();
 		}
+		if ($this->addressBookInfo['principaluri'] === 'principals/system/system' &&
+			$this->addressBookInfo['uri'] === 'system') {
+			$result['isLocalSystemBook'] = true;
+		}
 		return $result;
 	}
 }

apps/files_sharing/api/sharees.php

@@ -270,6 +270,9 @@ class Sharees {
 		$addressBookContacts = $this->contactsManager->search($search, ['CLOUD', 'FN']);
 		$foundRemoteById = false;
 		foreach ($addressBookContacts as $contact) {
+			if (isset($contact['isLocalSystemBook'])) {
+				continue;
+			}
 			if (isset($contact['CLOUD'])) {
 				$cloudIds = $contact['CLOUD'];
 				if (!is_array($cloudIds)) {