implemented "follow"

.gitignore

@@ -2,3 +2,4 @@
 /vendor/
 package-lock.json
 composer.lock
+.DS_Store

README.md

@@ -26,10 +26,10 @@ Implemented:
 * profile pages (JSON representation)
 * custom links
 * functional inbox/outbox
+* follow (accept follows)
 
 To implement:
 
-* follow (accept follows)
 * share posts
 * share comments
 
@@ -55,6 +55,10 @@ To implement:
 
 Project maintained on github at [pfefferle/wordpress-activitypub](https://github.com/pfefferle/wordpress-activitypub).
 
+### 0.1.0 ###
+
+* fully functional "follow" activity
+
 ### 0.0.2 ###
 
 * refactorins

activitypub.php

@@ -18,18 +18,31 @@
 function activitypub_init() {
 	require_once dirname( __FILE__ ) . '/includes/class-activitypub-signature.php';
 	require_once dirname( __FILE__ ) . '/includes/class-activitypub-post.php';
+	require_once dirname( __FILE__ ) . '/includes/class-db-activitypub-actor.php';
 	require_once dirname( __FILE__ ) . '/includes/functions.php';
 
 	require_once dirname( __FILE__ ) . '/includes/class-activitypub.php';
 	add_filter( 'template_include', array( 'Activitypub', 'render_json_template' ), 99 );
-	add_action( 'webfinger_user_data', array( 'Activitypub', 'add_webfinger_discovery' ), 10, 3 );
 	add_filter( 'query_vars', array( 'Activitypub', 'add_query_vars' ) );
 	add_action( 'init', array( 'Activitypub', 'add_rewrite_endpoint' ) );
 
-	require_once dirname( __FILE__ ) . '/includes/class-activitypub-outbox.php';
-	require_once dirname( __FILE__ ) . '/includes/class-activitypub-inbox.php';
 	// Configure the REST API route
-	add_action( 'rest_api_init', array( 'Activitypub_Outbox', 'register_routes' ) );
+	require_once dirname( __FILE__ ) . '/includes/class-rest-activitypub-outbox.php';
-	add_action( 'rest_api_init', array( 'Activitypub_Inbox', 'register_routes' ) );
+	add_action( 'rest_api_init', array( 'Rest_Activitypub_Outbox', 'register_routes' ) );
+
+	require_once dirname( __FILE__ ) . '/includes/class-rest-activitypub-inbox.php';
+	add_action( 'rest_api_init', array( 'Rest_Activitypub_Inbox', 'register_routes' ) );
+
+	require_once dirname( __FILE__ ) . '/includes/class-rest-activitypub-followers.php';
+	add_action( 'rest_api_init', array( 'Rest_Activitypub_Followers', 'register_routes' ) );
+
+	require_once dirname( __FILE__ ) . '/includes/class-rest-activitypub-webfinger.php';
+	add_action( 'webfinger_user_data', array( 'Rest_Activitypub_Webfinger', 'add_webfinger_discovery' ), 10, 3 );
+
+	// Configure activities
+	require_once dirname( __FILE__ ) . '/includes/class-activitypub-activities.php';
+	add_action( 'activitypub_inbox_follow', array( 'Activitypub_Activities', 'accept' ), 10, 2 );
+	add_action( 'activitypub_inbox_follow', array( 'Activitypub_Activities', 'follow' ), 10, 2 );
+	add_action( 'activitypub_inbox_unfollow', array( 'Activitypub_Activities', 'unfollow' ), 10, 2 );
 }
 add_action( 'plugins_loaded', 'activitypub_init' );

includes/class-activitypub-activities.php

@@ -0,0 +1,64 @@
+<?php
+
+class Activitypub_Activities {
+
+	/**
+	 * [accept description]
+	 * @param  [type] $data      [description]
+	 * @param  [type] $author_id [description]
+	 * @return [type]            [description]
+	 */
+	public static function accept( $data, $author_id ) {
+		if ( ! array_key_exists( 'actor', $data ) ) {
+			return new WP_Error( 'activitypub_no_actor', __( 'No "Actor" found', 'activitypub' ), $metadata );
+		}
+
+		$inbox = Db_Activitypub_Actor::get_inbox_by_actor( $data['actor'] );
+
+		$activity = wp_json_encode(
+			array(
+				'@context' => array( 'https://www.w3.org/ns/activitystreams' ),
+				'type' => 'Accept',
+				'actor' => get_author_posts_url( $author_id ),
+				'object' => $data,
+				'to' => $data['actor'],
+			)
+		);
+
+		return activitypub_safe_remote_post( $inbox, $activity, $author_id );
+	}
+
+	/**
+	 * [follow description]
+	 * @param  [type] $data      [description]
+	 * @param  [type] $author_id [description]
+	 * @return [type]            [description]
+	 */
+	public static function follow( $data, $author_id ) {
+		if ( ! array_key_exists( 'actor', $data ) ) {
+			return new WP_Error( 'activitypub_no_actor', __( 'No "Actor" found', 'activitypub' ), $metadata );
+		}
+
+		Db_Activitypub_Actor::add_follower( $data['actor'], $author_id );
+	}
+
+	/**
+	 * [unfollow description]
+	 * @param  [type] $data      [description]
+	 * @param  [type] $author_id [description]
+	 * @return [type]            [description]
+	 */
+	public static function unfollow( $data, $author_id ) {
+
+	}
+
+	/**
+	 * [create description]
+	 * @param  [type] $data      [description]
+	 * @param  [type] $author_id [description]
+	 * @return [type]            [description]
+	 */
+	public static function create( $data, $author_id ) {
+
+	}
+}

includes/class-activitypub-signature.php

@@ -1,38 +1,39 @@
 <?php
 
 class Activitypub_Signature {
+
 	/**
-	 * @param int $user_id
+	 * @param int $author_id
 	 *
 	 * @return mixed
 	 */
-	public static function get_public_key( $user_id, $force = false ) {
+	public static function get_public_key( $author_id, $force = false ) {
-		$key = get_user_meta( $user_id, 'magic_sig_public_key' );
+		$key = get_user_meta( $author_id, 'magic_sig_public_key' );
 
 		if ( $key && ! $force ) {
 			return $key[0];
 		}
 
-		self::generate_key_pair( $user_id );
+		self::generate_key_pair( $author_id );
-		$key = get_user_meta( $user_id, 'magic_sig_public_key' );
+		$key = get_user_meta( $author_id, 'magic_sig_public_key' );
 
 		return $key[0];
 	}
 
 	/**
-	 * @param int $user_id
+	 * @param int $author_id
 	 *
 	 * @return mixed
 	 */
-	public static function get_private_key( $user_id, $force = false ) {
+	public static function get_private_key( $author_id, $force = false ) {
-		$key = get_user_meta( $user_id, 'magic_sig_private_key' );
+		$key = get_user_meta( $author_id, 'magic_sig_private_key' );
 
 		if ( $key && ! $force ) {
 			return $key[0];
 		}
 
-		self::generate_key_pair( $user_id );
+		self::generate_key_pair( $author_id );
-		$key = get_user_meta( $user_id, 'magic_sig_private_key' );
+		$key = get_user_meta( $author_id, 'magic_sig_private_key' );
 
 		return $key[0];
 	}
@@ -40,9 +41,9 @@ class Activitypub_Signature {
 	/**
 	 * Generates the pair keys
 	 *
-	 * @param int $user_id
+	 * @param int $author_id
 	 */
-	public static function generate_key_pair( $user_id ) {
+	public static function generate_key_pair( $author_id ) {
 		$config = array(
 			'digest_alg' => 'sha512',
 			'private_key_bits' => 2048,
@@ -55,16 +56,16 @@ class Activitypub_Signature {
 		openssl_pkey_export( $key, $priv_key );
 
 		// private key
-		update_user_meta( $user_id, 'magic_sig_private_key', $priv_key );
+		update_user_meta( $author_id, 'magic_sig_private_key', $priv_key );
 
 		$detail = openssl_pkey_get_details( $key );
 
 		// public key
-		update_user_meta( $user_id, 'magic_sig_public_key', $detail['key'] );
+		update_user_meta( $author_id, 'magic_sig_public_key', $detail['key'] );
 	}
 
-	public static function generate_signature( $user_id, $inbox ) {
+	public static function generate_signature( $author_id, $inbox, $date ) {
-		$key = self::get_private_key( $user_id );
+		$key = self::get_private_key( $author_id );
 
 		$url_parts = wp_parse_url( $inbox );
 
@@ -73,7 +74,7 @@ class Activitypub_Signature {
 
 		// add path
 		if ( ! empty( $url_parts['path'] ) ) {
-			$path .= $url_parts['path'];
+			$path = $url_parts['path'];
 		}
 
 		// add query
@@ -81,11 +82,11 @@ class Activitypub_Signature {
 			$path .= '?' . $url_parts['query'];
 		}
 
-		$date = gmdate( 'D, d M Y H:i:s T' );
 		$signed_string = "(request-target): post $path\nhost: $host\ndate: $date";
 
 		$signature = null;
 		openssl_sign( $signed_string, $signature, $key, OPENSSL_ALGO_SHA256 );
+		$signature = base64_encode( $signature );
 
 		$key_id = get_author_posts_url( $author_id ) . '#main-key';
 

includes/class-activitypub.php

@@ -54,23 +54,6 @@ class Activitypub {
 		return $json_template;
 	}
 
-	/**
-	 * Add WebFinger discovery links
-	 *
-	 * @param array   $array    the jrd array
-	 * @param string  $resource the WebFinger resource
-	 * @param WP_User $user     the WordPress user
-	 */
-	public static function add_webfinger_discovery( $array, $resource, $user ) {
-		$array['links'][] = array(
-			'rel'  => 'self',
-			'type' => 'application/activity+json',
-			'href' => get_author_posts_url( $user->ID ),
-		);
-
-		return $array;
-	}
-
 	/**
 	 * Add the 'photos' query variable so WordPress
 	 * won't mangle it.

includes/class-db-activitypub-actor.php

@@ -0,0 +1,93 @@
+<?php
+
+class Db_Activitypub_Actor {
+	/**
+	 * [get_inbox_by_actor description]
+	 * @param  [type] $actor [description]
+	 * @return [type]        [description]
+	 */
+	public static function get_inbox_by_actor( $actor ) {
+		$metadata = self::get_metadata_by_actor( $actor );
+
+		if ( is_wp_error( $metadata ) ) {
+			return $metadata;
+		}
+
+		if ( array_key_exists( 'inbox', $metadata ) ) {
+			return $metadata['inbox'];
+		}
+
+		return new WP_Error( 'activitypub_no_inbox', __( 'No "Inbox" found', 'activitypub' ), $metadata );
+	}
+
+	/**
+	 * [get_metadata_by_actor description]
+	 * @param  [type] $actor [description]
+	 * @return [type]        [description]
+	 */
+	public static function get_metadata_by_actor( $actor ) {
+		$metadata = get_transient( 'activitypub_' . $actor );
+
+		if ( $metadata ) {
+			return $metadata;
+		}
+
+		if ( ! wp_http_validate_url( $actor ) ) {
+			return new WP_Error( 'activitypub_no_valid_actor_url', __( 'The "actor" is no valid URL', 'activitypub' ), $actor );
+		}
+
+		$wp_version = get_bloginfo( 'version' );
+
+		$user_agent = apply_filters( 'http_headers_useragent', 'WordPress/' . $wp_version . '; ' . get_bloginfo( 'url' ) );
+		$args       = array(
+			'timeout'             => 100,
+			'limit_response_size' => 1048576,
+			'redirection'         => 3,
+			'user-agent'          => "$user_agent; ActivityPub",
+			'headers'             => array( 'accept' => 'application/activity+json' ),
+		);
+
+		$response = wp_safe_remote_get( $actor, $args );
+
+		if ( is_wp_error( $response ) ) {
+			return $response;
+		}
+
+		$metadata = wp_remote_retrieve_body( $response );
+		$metadata = json_decode( $metadata, true );
+
+		if ( ! $metadata ) {
+			return new WP_Error( 'activitypub_invalid_json', __( 'No valid JSON data', 'activitypub' ), $actor );
+		}
+
+		set_transient( 'activitypub_' . $actor, $metadata, WEEK_IN_SECONDS );
+
+		return $metadata;
+	}
+
+	public static function add_follower( $actor, $author_id ) {
+		$followers = get_user_option( 'activitypub_followers', $author_id );
+
+		if ( ! is_array( $followers ) ) {
+			$followers = array( $actor );
+		} else {
+			$followers[] = $actor;
+		}
+
+		$followers = array_unique( $followers );
+
+		update_user_meta( $author_id, 'activitypub_followers', $followers );
+	}
+
+	public static function remove_follower( $actor, $author_id ) {
+		$followers = get_user_option( 'activitypub_followers', $author_id );
+
+		foreach ( $followers as $key => $value ) {
+			if ( $value === $actor) {
+				unset( $followers[$key] );
+			}
+		}
+
+		update_user_meta( $author_id, 'activitypub_followers', $followers );
+	}
+}

includes/class-rest-activitypub-followers.php

@@ -0,0 +1,76 @@
+<?php
+
+class Rest_Activitypub_Followers {
+	/**
+	 * Register routes
+	 */
+	public static function register_routes() {
+		register_rest_route(
+			'activitypub/1.0', '/users/(?P<id>\d+)/followers', array(
+				array(
+					'methods'  => WP_REST_Server::READABLE,
+					'callback' => array( 'Rest_Activitypub_Followers', 'get' ),
+					'args'     => self::request_parameters(),
+				),
+			)
+		);
+	}
+
+	public static function get( $request ) {
+		$author_id = $request->get_param( 'id' );
+		$author    = get_user_by( 'ID', $author_id );
+
+		if ( ! $author ) {
+			return new WP_Error( 'rest_invalid_param', __( 'User not found', 'activitypub' ), array(
+				'status' => 404, 'params' => array(
+					'user_id' => __( 'User not found', 'activitypub' )
+				)
+			) );
+		}
+
+		$page = $request->get_param( 'page', 0 );
+
+		/*
+		 * Action triggerd prior to the ActivityPub profile being created and sent to the client
+		 */
+		do_action( 'activitypub_outbox_pre' );
+
+		$json = new stdClass();
+
+		$json->{'@context'} = get_activitypub_context();
+
+		$followers = get_user_option( 'activitypub_followers', $author_id );
+
+		if ( ! is_array( $followers ) ) {
+			$followers = array();
+		}
+
+		$json->totlaItems = count( $followers );
+		$json->orderedItems = $followers;
+
+		$response = new WP_REST_Response( $json, 200 );
+		$response->header( 'Content-Type', 'application/activity+json' );
+
+		return $response;
+	}
+
+	/**
+	 * The supported parameters
+	 *
+	 * @return array list of parameters
+	 */
+	public static function request_parameters() {
+		$params = array();
+
+		$params['page'] = array(
+			'type' => 'integer',
+		);
+
+		$params['id'] = array(
+			'required' => true,
+			'type' => 'integer',
+		);
+
+		return $params;
+	}
+}

includes/class-rest-activitypub-inbox.php

@@ -4,7 +4,7 @@
  *
  * @author Matthias Pfefferle
  */
-class Activitypub_Inbox {
+class Rest_Activitypub_Inbox {
 	/**
 	 * Register routes
 	 */
@@ -13,7 +13,7 @@ class Activitypub_Inbox {
 			'activitypub/1.0', '/inbox', array(
 				array(
 					'methods'  => WP_REST_Server::EDITABLE,
-					'callback' => array( 'Activitypub_Inbox', 'global_inbox' ),
+					'callback' => array( 'Rest_Activitypub_Inbox', 'global_inbox' ),
 				),
 			)
 		);
@@ -22,7 +22,7 @@ class Activitypub_Inbox {
 			'activitypub/1.0', '/users/(?P<id>\d+)/inbox', array(
 				array(
 					'methods'  => WP_REST_Server::EDITABLE,
-					'callback' => array( 'Activitypub_Inbox', 'user_inbox' ),
+					'callback' => array( 'Rest_Activitypub_Inbox', 'user_inbox' ),
 					'args'     => self::request_parameters(),
 				),
 			)

includes/class-rest-activitypub-outbox.php

@@ -4,7 +4,7 @@
  *
  * @author Matthias Pfefferle
  */
-class Activitypub_Outbox {
+class Rest_Activitypub_Outbox {
 	/**
 	 * Register routes
 	 */
@@ -13,7 +13,7 @@ class Activitypub_Outbox {
 			'activitypub/1.0', '/users/(?P<id>\d+)/outbox', array(
 				array(
 					'methods'  => WP_REST_Server::READABLE,
-					'callback' => array( 'Activitypub_Outbox', 'get' ),
+					'callback' => array( 'Rest_Activitypub_Outbox', 'get' ),
 					'args'     => self::request_parameters(),
 				),
 			)

includes/class-rest-activitypub-webfinger.php

@@ -0,0 +1,20 @@
+<?php
+
+class Rest_Activitypub_Webfinger {
+	/**
+	 * Add WebFinger discovery links
+	 *
+	 * @param array   $array    the jrd array
+	 * @param string  $resource the WebFinger resource
+	 * @param WP_User $user     the WordPress user
+	 */
+	public static function add_webfinger_discovery( $array, $resource, $user ) {
+		$array['links'][] = array(
+			'rel'  => 'self',
+			'type' => 'application/activity+json',
+			'href' => get_author_posts_url( $user->ID ),
+		);
+
+		return $array;
+	}
+}

includes/functions.php

@@ -38,3 +38,51 @@ function get_activitypub_context() {
 
 	return apply_filters( 'activitypub_json_context', $context );
 }
+
+if ( ! function_exists( 'base64_url_encode' ) ) {
+	/**
+	 * Encode data
+	 *
+	 * @param string $input input text
+	 *
+	 * @return string the encoded text
+	 */
+	function base64_url_encode( $input ) {
+		return strtr( base64_encode( $input ), '+/', '-_' );
+	}
+}
+if ( ! function_exists( 'base64_url_decode' ) ) {
+	/**
+	 * Dencode data
+	 *
+	 * @param string $input input text
+	 *
+	 * @return string the decoded text
+	 */
+	function base64_url_decode( $input ) {
+		return base64_decode( strtr( $input, '-_', '+/' ) );
+	}
+}
+
+function activitypub_safe_remote_post( $url, $body, $author_id ) {
+	$date = gmdate( 'D, d M Y H:i:s T' );
+	$signature = Activitypub_Signature::generate_signature( $author_id, $url, $date );
+
+	$wp_version = get_bloginfo( 'version' );
+	$user_agent = apply_filters( 'http_headers_useragent', 'WordPress/' . $wp_version . '; ' . get_bloginfo( 'url' ) );
+	$args = array(
+		'timeout' => 100,
+		'limit_response_size' => 1048576,
+		'redirection' => 3,
+		'user-agent' => "$user_agent; ActivityPub",
+		'headers' => array(
+			'Accept' => 'application/activity+json',
+			'Content-Type' => 'application/activity+json',
+			'Signature' => $signature,
+			'Date' => $date,
+		),
+		'body' => $body,
+	);
+
+	$response = wp_safe_remote_post( $url, $args );
+}

languages/activitypub.pot

@@ -4,7 +4,7 @@ msgid ""
 msgstr ""
 "Project-Id-Version: ActivityPub 0.0.2\n"
 "Report-Msgid-Bugs-To: https://wordpress.org/support/plugin/activitypub\n"
-"POT-Creation-Date: 2018-12-01 20:22:43+00:00\n"
+"POT-Creation-Date: 2018-12-07 23:01:55+00:00\n"
 "MIME-Version: 1.0\n"
 "Content-Type: text/plain; charset=utf-8\n"
 "Content-Transfer-Encoding: 8bit\n"
@@ -13,28 +13,47 @@ msgstr ""
 "Language-Team: LANGUAGE <LL@li.org>\n"
 "X-Generator: grunt-wp-i18n1.0.2\n"
 
-#: includes/class-activitypub-inbox.php:47
+#: includes/class-activitypub-activities.php:13
-msgid "Invalid payload"
+#: includes/class-activitypub-activities.php:39
+msgid "No \"Actor\" found"
 msgstr ""
 
-#: includes/class-activitypub-inbox.php:62
+#: includes/class-db-activitypub-actor.php:20
-msgid "This method is not yet implemented"
+msgid "No \"Inbox\" found"
 msgstr ""
 
-#: includes/class-activitypub-outbox.php:28
+#: includes/class-db-activitypub-actor.php:36
-#: includes/class-activitypub-outbox.php:30
+msgid "The \"actor\" is no valid URL"
+msgstr ""
+
+#: includes/class-db-activitypub-actor.php:60
+msgid "No valid JSON data"
+msgstr ""
+
+#: includes/class-rest-activitypub-followers.php:24
+#: includes/class-rest-activitypub-followers.php:26
+#: includes/class-rest-activitypub-outbox.php:28
+#: includes/class-rest-activitypub-outbox.php:30
 msgid "User not found"
 msgstr ""
 
-#: templates/json-author.php:44
+#: includes/class-rest-activitypub-inbox.php:47
+msgid "Invalid payload"
+msgstr ""
+
+#: includes/class-rest-activitypub-inbox.php:62
+msgid "This method is not yet implemented"
+msgstr ""
+
+#: templates/json-author.php:48
 msgid "Blog"
 msgstr ""
 
-#: templates/json-author.php:50
+#: templates/json-author.php:58
 msgid "Profile"
 msgstr ""
 
-#: templates/json-author.php:57
+#: templates/json-author.php:69
 msgid "Website"
 msgstr ""
 

readme.txt

@@ -26,10 +26,10 @@ Implemented:
 * profile pages (JSON representation)
 * custom links
 * functional inbox/outbox
+* follow (accept follows)
 
 To implement:
 
-* follow (accept follows)
 * share posts
 * share comments
 
@@ -55,6 +55,10 @@ To implement:
 
 Project maintained on github at [pfefferle/wordpress-activitypub](https://github.com/pfefferle/wordpress-activitypub).
 
+= 0.1.0 =
+
+* fully functional "follow" activity
+
 = 0.0.2 =
 
 * refactorins

templates/json-author.php

@@ -7,7 +7,11 @@ $json->{'@context'} = get_activitypub_context();
 $json->id = get_author_posts_url( $author_id );
 $json->type = 'Person';
 $json->name = get_the_author_meta( 'display_name', $author_id );
-$json->summary = esc_html( get_the_author_meta( 'description', $author_id ) );
+$json->summary = html_entity_decode(
+	get_the_author_meta( 'description', $author_id ),
+	ENT_QUOTES,
+	'UTF-8'
+);
 $json->preferredUsername = get_the_author_meta( 'login', $author_id ); // phpcs:ignore
 $json->url = get_author_posts_url( $author_id );
 $json->icon = array(
@@ -42,20 +46,32 @@ $json->attachment = array();
 $json->attachment[] = array(
 	'type' => 'PropertyValue',
 	'name' => __( 'Blog', 'activitypub' ),
-	'value' => esc_html( '<a rel="me" title="' . esc_attr( home_url( '/' ) ) . '" target="_blank" href="' . home_url( '/' ) . '">' . wp_parse_url( home_url( '/' ), PHP_URL_HOST ) . '</a>' ),
+	'value' => html_entity_decode(
+		'<a rel="me" title="' . esc_attr( home_url( '/' ) ) . '" target="_blank" href="' . home_url( '/' ) . '">' . wp_parse_url( home_url( '/' ), PHP_URL_HOST ) . '</a>',
+		ENT_QUOTES,
+		'UTF-8'
+	),
 );
 
 $json->attachment[] = array(
 	'type' => 'PropertyValue',
 	'name' => __( 'Profile', 'activitypub' ),
-	'value' => esc_html( '<a rel="me" title="' . esc_attr( get_author_posts_url( $author_id ) ) . '" target="_blank" href="' . get_author_posts_url( $author_id ) . '">' . wp_parse_url( get_author_posts_url( $author_id ), PHP_URL_HOST ) . '</a>' ),
+	'value' => html_entity_decode(
+		'<a rel="me" title="' . esc_attr( get_author_posts_url( $author_id ) ) . '" target="_blank" href="' . get_author_posts_url( $author_id ) . '">' . wp_parse_url( get_author_posts_url( $author_id ), PHP_URL_HOST ) . '</a>',
+		ENT_QUOTES,
+		'UTF-8'
+	),
 );
 
 if ( get_the_author_meta( 'user_url', $author_id ) ) {
 	$json->attachment[] = array(
 		'type' => 'PropertyValue',
 		'name' => __( 'Website', 'activitypub' ),
-		'value' => esc_html( '<a rel="me" title="' . esc_attr( get_the_author_meta( 'user_url', $author_id ) ) . '" target="_blank" href="' . get_the_author_meta( 'user_url', $author_id ) . '">' . wp_parse_url( get_the_author_meta( 'user_url', $author_id ), PHP_URL_HOST ) . '</a>' ),
+		'value' => html_entity_decode(
+			'<a rel="me" title="' . esc_attr( get_the_author_meta( 'user_url', $author_id ) ) . '" target="_blank" href="' . get_the_author_meta( 'user_url', $author_id ) . '">' . wp_parse_url( get_the_author_meta( 'user_url', $author_id ), PHP_URL_HOST ) . '</a>',
+			ENT_QUOTES,
+			'UTF-8'
+		),
 	);
 }