From: Michael <heluecht@pirati.ca>
Date: Tue, 20 Nov 2018 20:40:47 +0000 (+0000)
Subject: AP: Security check against forged "create" activities
X-Git-Url: https://git.mxchange.org/?a=commitdiff_plain;h=5c39779b45005c12962e7e92d3428efd187f279c;p=friendica.git

AP: Security check against forged "create" activities
---

diff --git a/src/Protocol/ActivityPub/Receiver.php b/src/Protocol/ActivityPub/Receiver.php
index 686ac8be32..a101c5335d 100644
--- a/src/Protocol/ActivityPub/Receiver.php
+++ b/src/Protocol/ActivityPub/Receiver.php
@@ -309,6 +309,16 @@ class Receiver
 
 		}
 
+		// Don't trust the source if "actor" differs from "attributedTo". The content could be forged.
+		if ($trust_source && ($type == 'as:Create') && is_array($activity['as:object'])) {
+			$actor = JsonLD::fetchElement($activity, 'as:actor');
+			$attributed_to = JsonLD::fetchElement($activity['as:object'], 'as:attributedTo');
+			$trust_source = ($actor == $attributed_to);
+			if (!$trust_source) {
+				Logger::log('Not trusting actor: ' . $actor . '. It differs from  attributedTo: ' . $attributed_to, Logger::DEBUG);
+			}
+		}
+
 		// $trust_source is called by reference and is set to true if the content was retrieved successfully
 		$object_data = self::prepareObjectData($activity, $uid, $trust_source);
 		if (empty($object_data)) {