Make WordPress Core


Ignore:
Timestamp:
09/29/2023 07:45:53 PM (5 months ago)
Author:
westonruter
Message:

Script Loader: Harden removal of script tag wrappers.

  • Add wp_remove_surrounding_empty_script_tags() to more precisely remove script tag wrappers and warn when doing it wrong.
  • Add clarifying comments for XML escaping logic in wp_get_inline_script_tag().
  • Leverage WP_HTML_Tag_Processor in test_remove_frameless_preview_messenger_channel.
  • Reuse assertEqualMarkup in test_blocking_dependent_with_delayed_dependency.
  • Normalize whitespace in parse_markup_fragment for assertEqualMarkup.

Follow-up to [56687].
Props dmsnell, westonruter, flixos90.
See #58664.

File:
1 edited

Legend:

Unmodified
Added
Removed
  • trunk/src/wp-includes/script-loader.php

    r56739 r56748  
    28542854    }
    28552855
    2856     // Ensure markup is XHTML compatible if not HTML5.
     2856    /*
     2857     * XHTML extracts the contents of the SCRIPT element and then the XML parser
     2858     * decodes character references and other syntax elements. This can lead to
     2859     * misinterpretation of the script contents or invalid XHTML documents.
     2860     *
     2861     * Wrapping the contents in a CDATA section instructs the XML parser not to
     2862     * transform the contents of the SCRIPT element before passing them to the
     2863     * JavaScript engine.
     2864     *
     2865     * Example:
     2866     *
     2867     *     <script>console.log('&hellip;');</script>
     2868     *
     2869     *     In an HTML document this would print "&hellip;" to the console,
     2870     *     but in an XHTML document it would print "…" to the console.
     2871     *
     2872     *     <script>console.log('An image is <img> in HTML');</script>
     2873     *
     2874     *     In an HTML document this would print "An image is <img> in HTML",
     2875     *     but it's an invalid XHTML document because it interprets the `<img>`
     2876     *     as an empty tag missing its closing `/`.
     2877     *
     2878     * @see https://www.w3.org/TR/xhtml1/#h-4.8
     2879     */
    28572880    if ( ! $is_html5 ) {
    2858         $javascript = str_replace( ']]>', ']]]]><![CDATA[>', $javascript ); // Escape any existing CDATA section.
     2881        /*
     2882         * If the string `]]>` exists within the JavaScript it would break
     2883         * out of any wrapping CDATA section added here, so to start, it's
     2884         * necessary to escape that sequence which requires splitting the
     2885         * content into two CDATA sections wherever it's found.
     2886         *
     2887         * Note: it's only necessary to escape the closing `]]>` because
     2888         * an additional `<![CDATA[` leaves the contents unchanged.
     2889         */
     2890        $javascript = str_replace( ']]>', ']]]]><![CDATA[>', $javascript );
     2891
     2892        // Wrap the entire escaped script inside a CDATA section.
    28592893        $javascript = sprintf( "/* <![CDATA[ */\n%s\n/* ]]> */", $javascript );
    28602894    }
     
    33003334    return $editor_settings;
    33013335}
     3336
     3337/**
     3338 * Removes leading and trailing _empty_ script tags.
     3339 *
     3340 * This is a helper meant to be used for literal script tag construction
     3341 * within `wp_get_inline_script_tag()` or `wp_print_inline_script_tag()`.
     3342 * It removes the literal values of "<script>" and "</script>" from
     3343 * around an inline script after trimming whitespace. Typlically this
     3344 * is used in conjunction with output buffering, where `ob_get_clean()`
     3345 * is passed as the `$contents` argument.
     3346 *
     3347 * Example:
     3348 *
     3349 *     // Strips exact literal empty SCRIPT tags.
     3350 *     $js = '<script>sayHello();</script>;
     3351 *     'sayHello();' === wp_remove_surrounding_empty_script_tags( $js );
     3352 *
     3353 *     // Otherwise if anything is different it warns in the JS console.
     3354 *     $js = '<script type="text/javascript">console.log( "hi" );</script>';
     3355 *     'console.error( ... )' === wp_remove_surrounding_empty_script_tags( $js );
     3356 *
     3357 * @private
     3358 * @since 6.4.0
     3359 *
     3360 * @see wp_print_inline_script_tag()
     3361 * @see wp_get_inline_script_tag()
     3362 *
     3363 * @param string $contents Script body with manually created SCRIPT tag literals.
     3364 * @return string Script body without surrounding script tag literals, or
     3365 *                original contents if both exact literals aren't present.
     3366 */
     3367function wp_remove_surrounding_empty_script_tags( $contents ) {
     3368    $contents = trim( $contents );
     3369    $opener   = '<SCRIPT>';
     3370    $closer   = '</SCRIPT>';
     3371
     3372    if (
     3373        strlen( $contents ) > strlen( $opener ) + strlen( $closer ) &&
     3374        strtoupper( substr( $contents, 0, strlen( $opener ) ) ) === $opener &&
     3375        strtoupper( substr( $contents, -strlen( $closer ) ) ) === $closer
     3376    ) {
     3377        return substr( $contents, strlen( $opener ), -strlen( $closer ) );
     3378    } else {
     3379        $error_message = __( 'Expected string to start with script tag (without attributes) and end with script tag, with optional whitespace.' );
     3380        _doing_it_wrong( __FUNCTION__, $error_message, '6.4' );
     3381        return sprintf( 'console.error(%s)', wp_json_encode( __( 'Function wp_remove_surrounding_empty_script_tags() used incorrectly in PHP.' ) . ' ' . $error_message ) );
     3382    }
     3383}
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