Merge pull request #184 from Automattic/fix/127-syndication-loop-prevention

Author: GaryJones

includes/class-syndication-wp-rest-client.php

@@ -25,7 +25,58 @@ function __construct( $site_ID, $port = 80, $timeout = 45 ) {
 	public static function get_client_data() {
 		return array( 'id' => 'WP_REST', 'modes' => array( 'push' ), 'name' => 'WordPress.com REST' );
 	}
-	
+
+	/**
+	 * Check if a post with the given meta key/value exists on the target site.
+	 *
+	 * Used to prevent syndication loops when syndicating back to source.
+	 *
+	 * @since 2.2.0
+	 *
+	 * @param string $meta_key   The meta key to search for.
+	 * @param string $meta_value The meta value to match.
+	 * @return bool True if post exists on target site, false otherwise.
+	 */
+	public function is_source_site_post( $meta_key = '', $meta_value = '' ) {
+
+		// If meta key or value are empty.
+		if ( empty( $meta_key ) || empty( $meta_value ) ) {
+			return false;
+		}
+
+		// Get posts from the target website matching the meta key and value.
+		$url = sprintf(
+			'https://public-api.wordpress.com/rest/v1/sites/%s/posts/?meta_key=%s&meta_value=%s',
+			$this->blog_ID,
+			rawurlencode( $meta_key ),
+			rawurlencode( $meta_value )
+		);
+
+		$response = wp_remote_get(
+			$url,
+			array(
+				'timeout'    => $this->timeout,
+				'user-agent' => $this->useragent,
+				'sslverify'  => false,
+				'headers'    => array(
+					'authorization' => 'Bearer ' . $this->access_token,
+				),
+			)
+		);
+
+		if ( is_wp_error( $response ) ) {
+			return false;
+		}
+
+		$response = json_decode( wp_remote_retrieve_body( $response ) );
+
+		if ( empty( $response->error ) && ! empty( $response->found ) && $response->found > 0 ) {
+			return true;
+		}
+
+		return false;
+	}
+
 	public function new_post( $post_ID ) {
 
 		$post = (array)get_post( $post_ID );

includes/class-syndication-wp-xmlrpc-client.php

@@ -448,6 +448,66 @@ function get_remote_post( $remote_post_id ) {
 		return $this->getResponse();
 	}
 
+	/**
+	 * Check if a post with the given meta key/value exists on the target site.
+	 *
+	 * Used to prevent syndication loops when syndicating back to source.
+	 *
+	 * @since 2.2.0
+	 *
+	 * @param string $meta_key   The meta key to search for.
+	 * @param string $meta_value The meta value to match.
+	 * @return bool True if post exists on target site, false otherwise.
+	 */
+	public function is_source_site_post( $meta_key = '', $meta_value = '' ) {
+
+		// If meta key or value are empty.
+		if ( empty( $meta_key ) || empty( $meta_value ) ) {
+			return false;
+		}
+
+		// Use filter to limit posts returned and request custom_fields.
+		$filter = array(
+			'number' => 100,
+		);
+
+		$result = $this->query(
+			'wp.getPosts',
+			'1',
+			$this->username,
+			$this->password,
+			$filter,
+			array( 'post_id', 'custom_fields' )
+		);
+
+		if ( ! $result ) {
+			return false;
+		}
+
+		$posts_list = $this->getResponse();
+
+		if ( empty( $posts_list ) ) {
+			return false;
+		}
+
+		foreach ( $posts_list as $post ) {
+			if ( empty( $post['custom_fields'] ) ) {
+				continue;
+			}
+
+			foreach ( $post['custom_fields'] as $field ) {
+				if ( isset( $field['key'], $field['value'] ) &&
+					$meta_key === $field['key'] &&
+					$meta_value === $field['value']
+				) {
+					return true;
+				}
+			}
+		}
+
+		return false;
+	}
+
 	public function is_post_exists( $remote_post_id ) {
 		$remote_post = $this->get_remote_post( $remote_post_id );
 

includes/class-wp-push-syndication-server.php

@@ -864,6 +864,10 @@ public function save_syndicate_settings() {
 		$selected_sitegroups = !empty( $_POST['selected_sitegroups'] ) ? array_map( 'sanitize_key', $_POST['selected_sitegroups'] ) : '' ;
 		update_post_meta( $post->ID, '_syn_selected_sitegroups', $selected_sitegroups );
 
+		if ( '' === get_post_meta( $post->ID, 'post_uniqueid', true ) ) {
+			update_post_meta( $post->ID, 'post_uniqueid', uniqid() );
+		}
+
 	}
 
 	public function add_syndication_status_metabox() {
@@ -928,6 +932,15 @@ public function push_content( $sites ) {
 				$client         = Syndication_Client_Factory::get_client( $transport_type  ,$site->ID );
 				$info           = $this->get_site_info( $site->ID, $slave_post_states, $client );
 
+				// Check if post already exists on target to prevent syndication loops.
+				if ( in_array( $transport_type, array( 'WP_REST', 'WP_XMLRPC' ), true ) ) {
+					$unique_id = get_post_meta( $post_ID, 'post_uniqueid', true );
+
+					if ( ! empty( $unique_id ) && $client->is_source_site_post( 'post_uniqueid', $unique_id ) ) {
+						continue;
+					}
+				}
+
 				if( $info['state'] == 'new' || $info['state'] == 'new-error' ) { // states 'new' and 'new-error'
 
 					$push_new_shortcircuit = apply_filters( 'syn_pre_push_new_post_shortcircuit', false, $post_ID, $site, $transport_type, $client, $info );