activitypub / includes / class-webfinger.php

class-webfinger.php in ActivityPub 4.0.2, at includes/class-webfinger.php

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1	<?php
2	/**
3	* WebFinger class file.
4	*
5	* @package Activitypub
6	*/
7
8	namespace Activitypub;
9
10	use WP_Error;
11	use Activitypub\Collection\Users;
12
13	/**
14	* ActivityPub WebFinger Class.
15	*
16	* @author Matthias Pfefferle
17	*
18	* @see https://webfinger.net/
19	*/
20	class Webfinger {
21	/**
22	* Returns a users WebFinger "resource".
23	*
24	* @param int $user_id The WordPress user id.
25	*
26	* @return string The user-resource.
27	*/
28	public static function get_user_resource( $user_id ) {
29	$user = Users::get_by_id( $user_id );
30	if ( ! $user \|\| is_wp_error( $user ) ) {
31	return '';
32	}
33
34	return $user->get_webfinger();
35	}
36
37	/**
38	* Resolve a WebFinger resource.
39	*
40	* @param string $uri The WebFinger Resource.
41	*
42	* @return string\|WP_Error The URL or WP_Error.
43	*/
44	public static function resolve( $uri ) {
45	$data = self::get_data( $uri );
46
47	if ( \is_wp_error( $data ) ) {
48	return $data;
49	}
50
51	if ( ! is_array( $data ) \|\| empty( $data['links'] ) ) {
52	return new WP_Error(
53	'webfinger_missing_links',
54	__( 'No valid Link elements found.', 'activitypub' ),
55	array(
56	'status' => 400,
57	'data' => $data,
58	)
59	);
60	}
61
62	foreach ( $data['links'] as $link ) {
63	if (
64	'self' === $link['rel'] &&
65	(
66	'application/activity+json' === $link['type'] \|\|
67	'application/ld+json; profile="https://www.w3.org/ns/activitystreams"' === $link['type']
68	)
69	) {
70	return $link['href'];
71	}
72	}
73
74	return new WP_Error(
75	'webfinger_url_no_activitypub',
76	__( 'The Site supports WebFinger but not ActivityPub', 'activitypub' ),
77	array(
78	'status' => 400,
79	'data' => $data,
80	)
81	);
82	}
83
84	/**
85	* Transform a URI to an acct <identifier>@<host>.
86	*
87	* @param string $uri The URI (acct:, mailto:, http:, https:).
88	*
89	* @return string\|WP_Error Error or acct URI.
90	*/
91	public static function uri_to_acct( $uri ) {
92	$data = self::get_data( $uri );
93
94	if ( is_wp_error( $data ) ) {
95	return $data;
96	}
97
98	// Check if subject is an acct URI.
99	if (
100	isset( $data['subject'] ) &&
101	\str_starts_with( $data['subject'], 'acct:' )
102	) {
103	return $data['subject'];
104	}
105
106	// Search for an acct URI in the aliases.
107	if ( isset( $data['aliases'] ) ) {
108	foreach ( $data['aliases'] as $alias ) {
109	if ( \str_starts_with( $alias, 'acct:' ) ) {
110	return $alias;
111	}
112	}
113	}
114
115	return new WP_Error(
116	'webfinger_url_no_acct',
117	__( 'No acct URI found.', 'activitypub' ),
118	array(
119	'status' => 400,
120	'data' => $data,
121	)
122	);
123	}
124
125	/**
126	* Convert a URI string to an identifier and its host.
127	* Automatically adds acct: if it's missing.
128	*
129	* @param string $url The URI (acct:, mailto:, http:, https:).
130	*
131	* @return WP_Error\|array Error reaction or array with identifier and host as values.
132	*/
133	public static function get_identifier_and_host( $url ) {
134	if ( ! $url ) {
135	return new WP_Error(
136	'webfinger_invalid_identifier',
137	__( 'Invalid Identifier', 'activitypub' ),
138	array(
139	'status' => 400,
140	'data' => $url,
141	)
142	);
143	}
144
145	// Remove leading @.
146	$url = ltrim( $url, '@' );
147
148	if ( ! preg_match( '/^([a-zA-Z+]+):/', $url, $match ) ) {
149	$identifier = 'acct:' . $url;
150	$scheme = 'acct';
151	} else {
152	$identifier = $url;
153	$scheme = $match[1];
154	}
155
156	$host = null;
157
158	switch ( $scheme ) {
159	case 'acct':
160	case 'mailto':
161	case 'xmpp':
162	if ( strpos( $identifier, '@' ) !== false ) {
163	$host = substr( $identifier, strpos( $identifier, '@' ) + 1 );
164	}
165	break;
166	default:
167	$host = wp_parse_url( $identifier, PHP_URL_HOST );
168	break;
169	}
170
171	if ( empty( $host ) ) {
172	return new WP_Error(
173	'webfinger_invalid_identifier',
174	__( 'Invalid Identifier', 'activitypub' ),
175	array(
176	'status' => 400,
177	'data' => $url,
178	)
179	);
180	}
181
182	return array( $identifier, $host );
183	}
184
185	/**
186	* Get the WebFinger data for a given URI.
187	*
188	* @param string $uri The Identifier: <identifier>@<host> or URI.
189	*
190	* @return WP_Error\|array Error reaction or array with identifier and host as values.
191	*/
192	public static function get_data( $uri ) {
193	$identifier_and_host = self::get_identifier_and_host( $uri );
194
195	if ( is_wp_error( $identifier_and_host ) ) {
196	return $identifier_and_host;
197	}
198
199	$transient_key = self::generate_cache_key( $uri );
200
201	list( $identifier, $host ) = $identifier_and_host;
202
203	$data = \get_transient( $transient_key );
204	if ( $data ) {
205	return $data;
206	}
207
208	$webfinger_url = sprintf(
209	'https://%s/.well-known/webfinger?resource=%s',
210	$host,
211	rawurlencode( $identifier )
212	);
213
214	$response = wp_safe_remote_get(
215	$webfinger_url,
216	array(
217	'headers' => array( 'Accept' => 'application/jrd+json' ),
218	)
219	);
220
221	if ( is_wp_error( $response ) ) {
222	return new WP_Error(
223	'webfinger_url_not_accessible',
224	__( 'The WebFinger Resource is not accessible.', 'activitypub' ),
225	array(
226	'status' => 400,
227	'data' => $webfinger_url,
228	)
229	);
230	}
231
232	$body = wp_remote_retrieve_body( $response );
233	$data = json_decode( $body, true );
234
235	\set_transient( $transient_key, $data, WEEK_IN_SECONDS );
236
237	return $data;
238	}
239
240	/**
241	* Get the Remote-Follow endpoint for a given URI.
242	*
243	* @param string $uri The WebFinger Resource URI.
244	*
245	* @return string\|WP_Error Error or the Remote-Follow endpoint URI.
246	*/
247	public static function get_remote_follow_endpoint( $uri ) {
248	$data = self::get_data( $uri );
249
250	if ( is_wp_error( $data ) ) {
251	return $data;
252	}
253
254	if ( empty( $data['links'] ) ) {
255	return new WP_Error(
256	'webfinger_missing_links',
257	__( 'No valid Link elements found.', 'activitypub' ),
258	array(
259	'status' => 400,
260	'data' => $data,
261	)
262	);
263	}
264
265	foreach ( $data['links'] as $link ) {
266	if ( 'http://ostatus.org/schema/1.0/subscribe' === $link['rel'] ) {
267	return $link['template'];
268	}
269	}
270
271	return new WP_Error(
272	'webfinger_missing_remote_follow_endpoint',
273	__( 'No valid Remote-Follow endpoint found.', 'activitypub' ),
274	array(
275	'status' => 400,
276	'data' => $data,
277	)
278	);
279	}
280
281	/**
282	* Generate a cache key for a given URI.
283	*
284	* @param string $uri A WebFinger Resource URI.
285	*
286	* @return string The cache key.
287	*/
288	public static function generate_cache_key( $uri ) {
289	$uri = ltrim( $uri, '@' );
290
291	if ( filter_var( $uri, FILTER_VALIDATE_EMAIL ) ) {
292	$uri = 'acct:' . $uri;
293	}
294
295	return 'webfinger_' . md5( $uri );
296	}
297	}
298