Filter.ExtractStyleBlocks TYPE: bool VERSION: 3.1.0 DEFAULT: false EXTERNAL: CSSTidy --DESCRIPTION--

This directive turns on the style block extraction filter, which removes style blocks from input HTML, cleans them up with CSSTidy, and places them in the StyleBlocks context variable, for further use by you, usually to be placed in an external stylesheet, or a style block in the head of your document.

Sample usage:


body {color:#F00;} Some text';

    $config = HTMLPurifier_Config::createDefault();
    $config->set('Filter', 'ExtractStyleBlocks', true);
    $purifier = new HTMLPurifier($config);

    $html = $purifier->purify($dirty);

    // This implementation writes the stylesheets to the styles/ directory.
    // You can also echo the styles inside the document, but it's a bit
    // more difficult to make sure they get interpreted properly by
    // browsers; try the usual CSS armoring techniques.
    $styles = $purifier->context->get('StyleBlocks');
    $dir = 'styles/';
    if (!is_dir($dir)) mkdir($dir);
    $hash = sha1($_GET['html']);
    foreach ($styles as $i => $style) {
        file_put_contents($name = $dir . $hash . "_$i");
        echo '';


Warning: It is possible for a user to mount an imagecrash attack using this CSS. Counter-measures are difficult; it is not simply enough to limit the range of CSS lengths (using relative lengths with many nesting levels allows for large values to be attained without actually specifying them in the stylesheet), and the flexible nature of selectors makes it difficult to selectively disable lengths on image tags (HTML Purifier, however, does disable CSS width and height in inline styling). There are probably two effective counter measures: an explicit width and height set to auto in all images in your document (unlikely) or the disabling of width and height (somewhat reasonable). Whether or not these measures should be used is left to the reader.

--# vim: et sw=4 sts=4