568 lines
17 KiB
PHP
568 lines
17 KiB
PHP
<?php
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/**
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* Signature class file.
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*
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* @package Activitypub
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*/
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namespace Activitypub;
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use Activitypub\Collection\Actors;
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use Activitypub\Collection\Remote_Actors;
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use Activitypub\Signature\Http_Message_Signature;
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use Activitypub\Signature\Http_Signature_Draft;
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/**
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* ActivityPub Signature Class.
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*
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* @author Matthias Pfefferle
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* @author Django Doucet
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*/
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class Signature {
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/**
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* Initialize the class.
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*/
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public static function init() {
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\add_filter( 'http_request_args', array( self::class, 'sign_request' ), 0, 2 ); // Ahead of all other filters, so signature is set.
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\add_filter( 'http_response', array( self::class, 'maybe_double_knock' ), 10, 3 );
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}
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/**
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* Sign an HTTP Request.
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*
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* @param array $args An array of HTTP request arguments.
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* @param string $url The request URL.
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*
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* @return array Request arguments with signature headers.
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*/
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public static function sign_request( $args, $url ) {
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// Bail if there's nothing to sign with.
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if ( ! isset( $args['key_id'], $args['private_key'] ) ) {
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return $args;
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}
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if ( '1' === \get_option( 'activitypub_rfc9421_signature' ) && self::could_support_rfc9421( $url ) ) {
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$signature = new Http_Message_Signature();
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} else {
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$signature = new Http_Signature_Draft();
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}
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return $signature->sign( $args, $url );
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}
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/**
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* Verifies the http signatures
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*
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* @param \WP_REST_Request|array $request The request object or $_SERVER array.
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*
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* @return bool|\WP_Error A boolean or WP_Error.
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*/
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public static function verify_http_signature( $request ) {
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if ( is_object( $request ) ) { // REST Request object.
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$body = $request->get_body();
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$headers = $request->get_headers();
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$headers['(request-target)'][0] = strtolower( $request->get_method() ) . ' ' . self::get_route( $request );
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} else {
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$headers = self::format_server_request( $request );
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$headers['(request-target)'][0] = strtolower( $headers['request_method'][0] ) . ' ' . $headers['request_uri'][0];
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}
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$signature = isset( $headers['signature_input'] ) ? new Http_Message_Signature() : new Http_Signature_Draft();
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return $signature->verify( $headers, $body ?? null );
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}
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/**
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* If a request with RFC-9421 signature fails, we try again with the Draft Cavage signature.
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*
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* @param array $response HTTP response.
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* @param array $args HTTP request arguments.
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* @param string $url The request URL.
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*
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* @return array The HTTP response.
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*/
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public static function maybe_double_knock( $response, $args, $url ) {
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// Bail if it didn't use an RFC-9421 signature or there's nothing to sign with.
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if ( ! isset( $args['key_id'], $args['private_key'], $args['headers']['Signature-Input'] ) ) {
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return $response;
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}
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$response_code = \wp_remote_retrieve_response_code( $response );
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// Fall back to Draft Cavage signature for any 4xx responses.
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if ( $response_code >= 400 && $response_code < 500 ) {
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unset( $args['headers']['Signature'], $args['headers']['Signature-Input'], $args['headers']['Content-Digest'] );
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self::rfc9421_add_unsupported_host( $url );
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$args = ( new Http_Signature_Draft() )->sign( $args, $url );
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$response = \wp_safe_remote_request( $url, $args );
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}
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return $response;
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}
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/**
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* Formats the $_SERVER to resemble the WP_REST_REQUEST array,
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* for use with verify_http_signature().
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*
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* @param array $server The $_SERVER array.
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*
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* @return array $request The formatted request array.
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*/
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public static function format_server_request( $server ) {
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$headers = array();
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foreach ( $server as $key => $value ) {
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$key = \str_replace( 'http_', '', \strtolower( $key ) );
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$headers[ $key ][] = \wp_unslash( $value );
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}
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return $headers;
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}
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/**
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* Returns route.
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*
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* @param \WP_REST_Request $request The request object.
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*
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* @return string
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*/
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private static function get_route( $request ) {
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// Check if the route starts with "index.php".
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if ( str_starts_with( $request->get_route(), '/index.php' ) || ! rest_get_url_prefix() ) {
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$route = $request->get_route();
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} else {
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$route = '/' . rest_get_url_prefix() . '/' . ltrim( $request->get_route(), '/' );
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}
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// Fix route for subdirectory installations.
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$path = \wp_parse_url( \get_home_url(), PHP_URL_PATH );
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if ( \is_string( $path ) ) {
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$path = trim( $path, '/' );
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}
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if ( $path ) {
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$route = '/' . $path . $route;
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}
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return $route;
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}
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/**
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* Check if RFC-9421 signature could be supported.
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*
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* @param string $url The URL to check.
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*
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* @return bool True, if RFC-9421 signature could be supported, false otherwise.
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*/
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private static function could_support_rfc9421( $url ) {
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$host = \wp_parse_url( $url, \PHP_URL_HOST );
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$list = \get_option( 'activitypub_rfc9421_unsupported', array() );
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if ( isset( $list[ $host ] ) ) {
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if ( $list[ $host ] > \time() ) {
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return false;
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}
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unset( $list[ $host ] );
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\update_option( 'activitypub_rfc9421_unsupported', $list );
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}
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return true;
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}
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/**
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* Set RFC-9421 signature unsupported for a given host.
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*
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* @param string $url The URL to set.
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*/
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private static function rfc9421_add_unsupported_host( $url ) {
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$list = \get_option( 'activitypub_rfc9421_unsupported', array() );
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$host = \wp_parse_url( $url, \PHP_URL_HOST );
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$list[ $host ] = \time() + MONTH_IN_SECONDS;
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\update_option( 'activitypub_rfc9421_unsupported', $list, false );
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}
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/**
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* Return the public key for a given user.
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*
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* @deprecated 7.0.0 Use {@see Actors::get_public_key()}.
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*
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* @param int $user_id The WordPress User ID.
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* @param bool $force Optional. Force the generation of a new key pair. Default false.
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*
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* @return string The public key.
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*/
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public static function get_public_key_for( $user_id, $force = false ) {
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\_deprecated_function( __METHOD__, '7.0.0', 'Activitypub\Collection\Actors::get_public_key' );
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return Actors::get_public_key( $user_id, $force );
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}
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/**
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* Return the private key for a given user.
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*
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* @deprecated 7.0.0 Use {@see Actors::get_private_key()}.
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*
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* @param int $user_id The WordPress User ID.
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* @param bool $force Optional. Force the generation of a new key pair. Default false.
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*
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* @return string The private key.
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*/
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public static function get_private_key_for( $user_id, $force = false ) {
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\_deprecated_function( __METHOD__, '7.0.0', 'Activitypub\Collection\Actors::get_private_key' );
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return Actors::get_private_key( $user_id, $force );
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}
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/**
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* Return the key pair for a given user.
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*
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* @deprecated 7.0.0 Use {@see Actors::get_keypair()}.
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*
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* @param int $user_id The WordPress User ID.
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*
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* @return array The key pair.
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*/
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public static function get_keypair_for( $user_id ) {
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\_deprecated_function( __METHOD__, '7.0.0', 'Activitypub\Collection\Actors::get_keypair' );
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return Actors::get_keypair( $user_id );
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}
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/**
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* Get public key from key_id.
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*
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* @deprecated 7.4.0 Use {@see Remote_Actors::get_public_key()}.
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*
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* @param string $key_id The URL to the public key.
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*
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* @return resource|\WP_Error The public key resource or WP_Error.
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*/
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public static function get_remote_key( $key_id ) {
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\_deprecated_function( __METHOD__, '7.4.0', 'Activitypub\Collection\Remote_Actors::get_public_key()' );
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return Remote_Actors::get_public_key( $key_id );
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}
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/**
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* Generates the Signature for an HTTP Request.
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*
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* @deprecated 7.0.0 Use {@see Signature::sign_request()}.
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*
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* @param int $user_id The WordPress User ID.
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* @param string $http_method The HTTP method.
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* @param string $url The URL to send the request to.
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* @param string $date The date the request is sent.
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* @param string $digest Optional. The digest of the request body. Default null.
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*
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* @return string The signature.
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*/
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public static function generate_signature( $user_id, $http_method, $url, $date, $digest = null ) {
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\_deprecated_function( __METHOD__, '7.0.0', self::class . '::sign_request()' );
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$user = Actors::get_by_id( $user_id );
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$key = Actors::get_private_key( $user_id );
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$url_parts = \wp_parse_url( $url );
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$host = $url_parts['host'];
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$path = '/';
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// Add path.
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if ( ! empty( $url_parts['path'] ) ) {
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$path = $url_parts['path'];
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}
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// Add query.
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if ( ! empty( $url_parts['query'] ) ) {
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$path .= '?' . $url_parts['query'];
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}
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$http_method = \strtolower( $http_method );
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if ( ! empty( $digest ) ) {
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$signed_string = "(request-target): $http_method $path\nhost: $host\ndate: $date\ndigest: $digest";
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} else {
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$signed_string = "(request-target): $http_method $path\nhost: $host\ndate: $date";
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}
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$signature = null;
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\openssl_sign( $signed_string, $signature, $key, \OPENSSL_ALGO_SHA256 );
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$signature = \base64_encode( $signature ); // phpcs:ignore WordPress.PHP.DiscouragedPHPFunctions.obfuscation_base64_encode
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$key_id = $user->get_id() . '#main-key';
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if ( ! empty( $digest ) ) {
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return \sprintf( 'keyId="%s",algorithm="rsa-sha256",headers="(request-target) host date digest",signature="%s"', $key_id, $signature );
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} else {
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return \sprintf( 'keyId="%s",algorithm="rsa-sha256",headers="(request-target) host date",signature="%s"', $key_id, $signature );
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}
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}
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/**
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* Gets the signature algorithm from the signature header.
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*
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* @deprecated 7.0.0 Use {@see Signature::verify()}.
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*
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* @param array $signature_block The signature block.
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*
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* @return string|bool The signature algorithm or false if not found.
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*/
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public static function get_signature_algorithm( $signature_block ) { // phpcs:ignore
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\_deprecated_function( __METHOD__, '7.0.0', self::class . '::verify' );
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if ( ! empty( $signature_block['algorithm'] ) ) {
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switch ( $signature_block['algorithm'] ) {
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case 'rsa-sha-512':
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return 'sha512'; // hs2019 https://datatracker.ietf.org/doc/html/draft-cavage-http-signatures-12.
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default:
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return 'sha256';
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}
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}
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return false;
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}
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/**
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* Parses the Signature header.
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*
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* @deprecated 7.0.0 Use {@see Signature::verify()}.
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*
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* @param string $signature The signature header.
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*
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* @return array Signature parts.
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*/
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public static function parse_signature_header( $signature ) { // phpcs:ignore
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\_deprecated_function( __METHOD__, '7.0.0', self::class . '::verify' );
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$parsed_header = array();
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$matches = array();
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if ( \preg_match( '/keyId="(.*?)"/ism', $signature, $matches ) ) {
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$parsed_header['keyId'] = trim( $matches[1] );
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}
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if ( \preg_match( '/created=["|\']*([0-9]*)["|\']*/ism', $signature, $matches ) ) {
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$parsed_header['(created)'] = trim( $matches[1] );
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}
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if ( \preg_match( '/expires=["|\']*([0-9]*)["|\']*/ism', $signature, $matches ) ) {
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$parsed_header['(expires)'] = trim( $matches[1] );
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}
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if ( \preg_match( '/algorithm="(.*?)"/ism', $signature, $matches ) ) {
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$parsed_header['algorithm'] = trim( $matches[1] );
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}
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if ( \preg_match( '/headers="(.*?)"/ism', $signature, $matches ) ) {
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$parsed_header['headers'] = \explode( ' ', trim( $matches[1] ) );
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}
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if ( \preg_match( '/signature="(.*?)"/ism', $signature, $matches ) ) {
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$parsed_header['signature'] = \base64_decode( preg_replace( '/\s+/', '', trim( $matches[1] ) ) ); // phpcs:ignore WordPress.PHP.DiscouragedPHPFunctions.obfuscation_base64_decode
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}
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if ( empty( $parsed_header['headers'] ) ) {
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$parsed_header['headers'] = array( 'date' );
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}
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return $parsed_header;
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}
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/**
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* Gets the header data from the included pseudo headers.
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*
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* @deprecated 7.0.0 Use {@see Signature::verify()}.
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*
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* @param array $signed_headers The signed headers.
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* @param array $signature_block The signature block.
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* @param array $headers The HTTP headers.
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*
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* @return string signed headers for comparison
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*/
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public static function get_signed_data( $signed_headers, $signature_block, $headers ) { // phpcs:ignore
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\_deprecated_function( __METHOD__, '7.0.0', self::class . '::verify' );
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$signed_data = '';
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// This also verifies time-based values by returning false if any of these are out of range.
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foreach ( $signed_headers as $header ) {
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if ( 'host' === $header ) {
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if ( isset( $headers['x_original_host'] ) ) {
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$signed_data .= $header . ': ' . $headers['x_original_host'][0] . "\n";
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continue;
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}
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}
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if ( '(request-target)' === $header ) {
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$signed_data .= $header . ': ' . $headers[ $header ][0] . "\n";
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continue;
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}
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if ( str_contains( $header, '-' ) ) {
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$signed_data .= $header . ': ' . $headers[ str_replace( '-', '_', $header ) ][0] . "\n";
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continue;
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}
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if ( '(created)' === $header ) {
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if ( ! empty( $signature_block['(created)'] ) && \intval( $signature_block['(created)'] ) > \time() ) {
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// Created in the future.
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return false;
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}
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if ( ! array_key_exists( '(created)', $headers ) ) {
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$signed_data .= $header . ': ' . $signature_block['(created)'] . "\n";
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continue;
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}
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}
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if ( '(expires)' === $header ) {
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if ( ! empty( $signature_block['(expires)'] ) && \intval( $signature_block['(expires)'] ) < \time() ) {
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// Expired in the past.
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return false;
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}
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if ( ! array_key_exists( '(expires)', $headers ) ) {
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$signed_data .= $header . ': ' . $signature_block['(expires)'] . "\n";
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continue;
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}
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}
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if ( 'date' === $header ) {
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// A signed `date` header with no value must fail closed, otherwise the time-window check is skipped.
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if ( empty( $headers[ $header ][0] ) ) {
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return false;
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}
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// date_create() returns false on malformed input; new DateTime() would instead throw.
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$d = \date_create( $headers[ $header ][0], new \DateTimeZone( 'UTC' ) );
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if ( false === $d ) {
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return false;
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}
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$d->setTimeZone( new \DateTimeZone( 'UTC' ) );
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$c = (int) $d->format( 'U' );
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// Match the past-skew of the maintained Http_Signature_Draft verifier (1 hour); use its 5-minute future allowance.
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$now = \time();
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$d_plus = $now + ( 5 * MINUTE_IN_SECONDS );
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$d_minus = $now - HOUR_IN_SECONDS;
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if ( $c > $d_plus || $c < $d_minus ) {
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// Time out of range.
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return false;
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}
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}
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if ( ! empty( $headers[ $header ][0] ) ) {
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$signed_data .= $header . ': ' . $headers[ $header ][0] . "\n";
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}
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}
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return \rtrim( $signed_data, "\n" );
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}
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/**
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* Generates the digest for an HTTP Request.
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*
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* @deprecated 7.0.0 Use {@see Signature::sign_request()}.
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*
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* @param string $body The body of the request.
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*
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* @return string The digest.
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*/
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public static function generate_digest( $body ) {
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\_deprecated_function( __METHOD__, '7.0.0', self::class . '::sign_request' );
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$digest = \base64_encode( \hash( 'sha256', $body, true ) ); // phpcs:ignore WordPress.PHP.DiscouragedPHPFunctions.obfuscation_base64_encode
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return "SHA-256=$digest";
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}
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/**
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* Compute the collection digest for a specific instance.
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*
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* Implements FEP-8fcf: Followers collection synchronization.
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* The digest is created by XORing together the individual SHA256 digests
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* of each follower's ID.
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*
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* @see https://codeberg.org/fediverse/fep/src/branch/main/fep/8fcf/fep-8fcf.md
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*
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* @param array $collection The user ID whose followers to compute.
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*
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* @return string|false The hex-encoded digest, or false if no followers.
|
|
*/
|
|
public static function get_collection_digest( $collection ) {
|
|
if ( empty( $collection ) || ! is_array( $collection ) ) {
|
|
return false;
|
|
}
|
|
|
|
// Initialize with zeros (64 hex chars = 32 bytes = 256 bits).
|
|
$digest = str_repeat( '0', 64 );
|
|
|
|
foreach ( $collection as $item ) {
|
|
// Compute SHA256 hash of the follower ID.
|
|
$hash = hash( 'sha256', $item );
|
|
|
|
// XOR the hash with the running digest.
|
|
$digest = self::xor_hex_strings( $digest, $hash );
|
|
}
|
|
|
|
return $digest;
|
|
}
|
|
|
|
/**
|
|
* XOR two hexadecimal strings.
|
|
*
|
|
* Used for FEP-8fcf digest computation.
|
|
*
|
|
* @param string $hex1 First hex string.
|
|
* @param string $hex2 Second hex string.
|
|
*
|
|
* @return string The XORed result as a hex string.
|
|
*/
|
|
public static function xor_hex_strings( $hex1, $hex2 ) {
|
|
$result = '';
|
|
|
|
// Ensure both strings are the same length (should be 64 chars for SHA256).
|
|
$length = \max( \strlen( $hex1 ), \strlen( $hex2 ) );
|
|
$hex1 = \str_pad( $hex1, $length, '0', STR_PAD_LEFT );
|
|
$hex2 = \str_pad( $hex2, $length, '0', STR_PAD_LEFT );
|
|
|
|
// XOR each pair of hex digits.
|
|
for ( $i = 0; $i < $length; $i += 2 ) {
|
|
$byte1 = \hexdec( \substr( $hex1, $i, 2 ) );
|
|
$byte2 = \hexdec( \substr( $hex2, $i, 2 ) );
|
|
$result .= \str_pad( \dechex( $byte1 ^ $byte2 ), 2, '0', STR_PAD_LEFT );
|
|
}
|
|
|
|
return $result;
|
|
}
|
|
|
|
/**
|
|
* Parse a Collection-Synchronization header (FEP-8fcf).
|
|
*
|
|
* Parses the signature-style format used by the Collection-Synchronization header.
|
|
*
|
|
* @see https://codeberg.org/fediverse/fep/src/branch/main/fep/8fcf/fep-8fcf.md
|
|
*
|
|
* @param string $header The header value.
|
|
*
|
|
* @return array|false Array with parsed parameters (collectionId, url, digest), or false on failure.
|
|
*/
|
|
public static function parse_collection_sync_header( $header ) {
|
|
if ( empty( $header ) ) {
|
|
return false;
|
|
}
|
|
|
|
// Parse the signature-style format: key="value", key="value".
|
|
$params = array();
|
|
|
|
if ( \preg_match_all( '/(\w+)="([^"]*)"/', $header, $matches, PREG_SET_ORDER ) ) {
|
|
foreach ( $matches as $match ) {
|
|
$params[ $match[1] ] = $match[2];
|
|
}
|
|
}
|
|
|
|
// Validate required fields for FEP-8fcf.
|
|
if ( empty( $params['collectionId'] ) || empty( $params['url'] ) || empty( $params['digest'] ) ) {
|
|
return false;
|
|
}
|
|
|
|
return $params;
|
|
}
|
|
}
|