410 lines
12 KiB
PHP
410 lines
12 KiB
PHP
<?php
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namespace Activitypub;
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use WP_Error;
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use DateTime;
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use DateTimeZone;
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use Activitypub\Model\User;
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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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* Return the public key for a given user.
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*
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* @param int $user_id The WordPress User ID.
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* @param bool $force Force the generation of a new key pair.
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*
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* @return mixed The public key.
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*/
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public static function get_public_key( $user_id, $force = false ) {
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if ( $force ) {
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self::generate_key_pair( $user_id );
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}
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if ( User::APPLICATION_USER_ID === $user_id ) {
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$key = \get_option( 'activitypub_magic_sig_public_key' );
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} else {
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$key = \get_user_meta( $user_id, 'magic_sig_public_key', true );
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}
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if ( ! $key ) {
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return self::get_public_key( $user_id, true );
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}
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return $key;
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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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* @param int $user_id The WordPress User ID.
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* @param bool $force Force the generation of a new key pair.
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*
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* @return mixed The private key.
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*/
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public static function get_private_key( $user_id, $force = false ) {
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if ( $force ) {
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self::generate_key_pair( $user_id );
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}
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if ( User::APPLICATION_USER_ID === $user_id ) {
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$key = \get_option( 'activitypub_magic_sig_private_key' );
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} else {
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$key = \get_user_meta( $user_id, 'magic_sig_private_key', true );
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}
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if ( ! $key ) {
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return self::get_private_key( $user_id, true );
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}
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return $key;
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}
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/**
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* Generates the pair keys
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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 void
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*/
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public static function generate_key_pair( $user_id ) {
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$config = array(
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'digest_alg' => 'sha512',
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'private_key_bits' => 2048,
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'private_key_type' => \OPENSSL_KEYTYPE_RSA,
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);
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$key = \openssl_pkey_new( $config );
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$priv_key = null;
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\openssl_pkey_export( $key, $priv_key );
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$detail = \openssl_pkey_get_details( $key );
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if ( User::APPLICATION_USER_ID === $user_id ) {
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// private key
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\update_option( 'activitypub_magic_sig_private_key', $priv_key );
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// public key
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\update_option( 'activitypub_magic_sig_public_key', $detail['key'] );
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} else {
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// private key
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\update_user_meta( $user_id, 'magic_sig_private_key', $priv_key );
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// public key
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\update_user_meta( $user_id, 'magic_sig_public_key', $detail['key'] );
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}
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}
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/**
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* Generates the Signature for a HTTP 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 The digest of the request body.
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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, $digest = null ) {
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$key = self::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
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if ( User::APPLICATION_USER_ID === $user_id ) {
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$key_id = \get_rest_url( null, 'activitypub/1.0/application#main-key' );
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} else {
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$key_id = \get_author_posts_url( $user_id ) . '#main-key';
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}
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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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* Verifies the http signatures
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*
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* @param WP_REQUEST|array $request The request object or $_SERVER array.
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*
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* @return mixed 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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// check if route starts with "index.php"
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if ( str_starts_with( $request->get_route(), 'index.php' ) ) {
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$route = $request->get_route();
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} else {
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$route = rest_get_url_prefix() . '/' . ltrim( $request->get_route(), '/' );
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}
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$headers = $request->get_headers();
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$actor = isset( json_decode( $request->get_body() )->actor ) ? json_decode( $request->get_body() )->actor : '';
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$headers['(request-target)'][0] = strtolower( $request->get_method() ) . ' ' . $route;
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} else {
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$request = self::format_server_request( $request );
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$headers = $request['headers']; // $_SERVER array
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$actor = null;
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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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if ( ! isset( $headers['signature'] ) ) {
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return new WP_Error( 'activitypub_signature', 'Request not signed', array( 'status' => 403 ) );
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}
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if ( array_key_exists( 'signature', $headers ) ) {
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$signature_block = self::parse_signature_header( $headers['signature'] );
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} elseif ( array_key_exists( 'authorization', $headers ) ) {
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$signature_block = self::parse_signature_header( $headers['authorization'] );
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}
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if ( ! isset( $signature_block ) || ! $signature_block ) {
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return new WP_Error( 'activitypub_signature', 'Incompatible request signature. keyId and signature are required', array( 'status' => 403 ) );
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}
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$signed_headers = $signature_block['headers'];
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if ( ! $signed_headers ) {
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$signed_headers = array( 'date' );
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}
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$signed_data = self::get_signed_data( $signed_headers, $signature_block, $headers );
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if ( ! $signed_data ) {
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return new WP_Error( 'activitypub_signature', 'Signed request date outside acceptable time window', array( 'status' => 403 ) );
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}
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$algorithm = self::get_signature_algorithm( $signature_block );
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if ( ! $algorithm ) {
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return new WP_Error( 'activitypub_signature', 'Unsupported signature algorithm (only rsa-sha256 and hs2019 are supported)', array( 'status' => 403 ) );
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}
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if ( \in_array( 'digest', $signed_headers, true ) && isset( $body ) ) {
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if ( is_array( $headers['digest'] ) ) {
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$headers['digest'] = $headers['digest'][0];
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}
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$digest = explode( '=', $headers['digest'], 2 );
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if ( 'SHA-256' === $digest[0] ) {
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$hashalg = 'sha256';
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}
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if ( 'SHA-512' === $digest[0] ) {
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$hashalg = 'sha512';
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}
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if ( \base64_encode( \hash( $hashalg, $body, true ) ) !== $digest[1] ) { // phpcs:ignore
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return new WP_Error( 'activitypub_signature', 'Invalid Digest header', array( 'status' => 403 ) );
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}
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}
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if ( $actor ) {
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$public_key = self::get_remote_key( $actor );
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} else {
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$public_key = self::get_remote_key( $signature_block['keyId'] );
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}
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if ( \is_wp_error( $public_key ) ) {
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return $public_key;
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}
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$verified = \openssl_verify( $signed_data, $signature_block['signature'], $public_key, $algorithm ) > 0;
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if ( ! $verified ) {
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return new WP_Error( 'activitypub_signature', 'Invalid signature', array( 'status' => 403 ) );
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}
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return $verified;
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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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* @param string $key_id
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*
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* @return string $publicKeyPem
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*/
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public static function get_remote_key( $key_id ) { // phpcs:ignore
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$actor = \Activitypub\get_remote_metadata_by_actor( strtok( strip_fragment_from_url( $key_id ), '?' ) ); // phpcs:ignore
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if ( \is_wp_error( $actor ) ) {
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return $actor;
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}
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if ( isset( $actor['publicKey']['publicKeyPem'] ) ) {
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return \rtrim( $actor['publicKey']['publicKeyPem'] ); // phpcs:ignore
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}
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return null;
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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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* @param array $signature_block
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*
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* @return string algorithm
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*/
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public static function get_signature_algorithm( $signature_block ) {
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if ( $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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* @param array $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( $header ) {
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$ret = array();
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$matches = array();
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$h_string = \implode( ',', (array) $header[0] );
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if ( \preg_match( '/keyId="(.*?)"/ism', $h_string, $matches ) ) {
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$ret['keyId'] = $matches[1];
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}
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if ( \preg_match( '/created=([0-9]*)/ism', $h_string, $matches ) ) {
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$ret['(created)'] = $matches[1];
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}
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if ( \preg_match( '/expires=([0-9]*)/ism', $h_string, $matches ) ) {
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$ret['(expires)'] = $matches[1];
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}
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if ( \preg_match( '/algorithm="(.*?)"/ism', $h_string, $matches ) ) {
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$ret['algorithm'] = $matches[1];
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}
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if ( \preg_match( '/headers="(.*?)"/ism', $h_string, $matches ) ) {
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$ret['headers'] = \explode( ' ', $matches[1] );
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}
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if ( \preg_match( '/signature="(.*?)"/ism', $h_string, $matches ) ) {
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$ret['signature'] = \base64_decode( preg_replace( '/\s+/', '', $matches[1] ) ); // phpcs:ignore
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}
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if ( ( $ret['signature'] ) && ( $ret['algorithm'] ) && ( ! $ret['headers'] ) ) {
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$ret['headers'] = array( 'date' );
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}
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return $ret;
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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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* @param array $signed_headers
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* @param array $signature_block (pseudo-headers)
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* @param array $headers (http headers)
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*
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* @return signed headers for comparison
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*/
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public static function get_signed_data( $signed_headers, $signature_block, $headers ) {
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$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 future
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return false;
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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 past
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return false;
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}
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}
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if ( 'date' === $header ) {
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// allow a bit of leeway for misconfigured clocks.
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$d = new DateTime( $headers[ $header ][0] );
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$d->setTimeZone( new DateTimeZone( 'UTC' ) );
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$c = $d->format( 'U' );
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$dplus = time() + ( 3 * HOUR_IN_SECONDS );
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$dminus = time() - ( 3 * HOUR_IN_SECONDS );
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if ( $c > $dplus || $c < $dminus ) {
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// time out of range
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return false;
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}
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}
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$signed_data .= $header . ': ' . $headers[ $header ][0] . "\n";
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}
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return \rtrim( $signed_data, "\n" );
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}
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public static function generate_digest( $body ) {
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$digest = \base64_encode( \hash( 'sha256', $body, true ) ); // phpcs:ignore
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return "SHA-256=$digest";
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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
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*
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* @return array $request
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*/
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public static function format_server_request( $server ) {
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$request = array();
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foreach ( $server as $param_key => $param_val ) {
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$req_param = strtolower( $param_key );
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if ( 'REQUEST_URI' === $req_param ) {
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$request['headers']['route'][] = $param_val;
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} else {
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$header_key = str_replace(
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'http_',
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'',
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$req_param
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);
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$request['headers'][ $header_key ][] = \wp_unslash( $param_val );
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}
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}
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return $request;
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}
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}
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