Prevent endless loops and long running feed processing

src/Model/GContact.php

@@ -884,11 +884,11 @@ class GContact
 			$items = $outbox['orderedItems'];
 		} elseif (!empty($outbox['first']['orderedItems'])) {
 			$items = $outbox['first']['orderedItems'];
-		} elseif (!empty($outbox['first']['href'])) {
+		} elseif (!empty($outbox['first']['href']) && ($outbox['first']['href'] != $feed)) {
 			self::updateFromOutbox($outbox['first']['href'], $data);
 			return;
 		} elseif (!empty($outbox['first'])) {
-			if (is_string($outbox['first'])) {
+			if (is_string($outbox['first']) && ($outbox['first'] != $feed)) {
 				self::updateFromOutbox($outbox['first'], $data);
 			} else {
 				Logger::warning('Unexpected data', ['outbox' => $outbox]);

src/Protocol/ActivityPub.php

@@ -231,7 +231,7 @@ class ActivityPub
 			$items = $data['orderedItems'];
 		} elseif (!empty($data['first']['orderedItems'])) {
 			$items = $data['first']['orderedItems'];
-		} elseif (!empty($data['first']) && is_string($data['first'])) {
+		} elseif (!empty($data['first']) && is_string($data['first']) && ($data['first'] != $url)) {
 			return self::fetchItems($data['first'], $uid);
 		} else {
 			$items = [];

src/Protocol/Feed.php

@@ -232,8 +232,16 @@ class Feed {
 		}
 
 		$items = [];
+
+		// Limit the number of items that are about to be fetched
+		$total_items = ($entries->length - 1);
+		$max_items = DI::config()->get('system', 'max_feed_items');
+		if (($max_items > 0) && ($total_items > $max_items)) {
+			$total_items = $max_items;
+		}
+
 		// Importing older entries first
-		for ($i = $entries->length - 1; $i >= 0; --$i) {
+		for ($i = $total_items; $i >= 0; --$i) {
 			$entry = $entries->item($i);
 
 			$item = array_merge($header, $author);

static/defaults.config.php

@@ -273,6 +273,10 @@ return [
 		// Maximum number of queue items for a single contact before subsequent messages are discarded.
 		'max_contact_queue' => 500,
 
+		// max_feed_items (Integer)
+		// Maximum number of feed items that are fetched and processed. For unlimited items set to 0.
+		'max_feed_items' => 10,
+
 		// max_image_length (Integer)
 		// An alternate way of limiting picture upload sizes.
 		// Specify the maximum pixel  length that pictures are allowed to be (for non-square pictures, it will apply to the longest side).