htmlpurifier/library/HTMLPurifier/URIScheme/file.php

<?php

/**
 * Validates file as defined by RFC 1630 and RFC 1738.
 */
class HTMLPurifier_URIScheme_file extends HTMLPurifier_URIScheme {

    // Generally file:// URLs are not accessible from most
    // machines, so placing them as an img src is incorrect.
    public $browsable = false;

    // Basically the *only* URI scheme for which this is true, since
    // accessing files on the local machine is very common.  In fact,
    // browsers on some operating systems don't understand the
    // authority, though I hear it is used on Windows to refer to
    // network shares.
    public $may_omit_host = true;

    public function doValidate(&$uri, $config, $context) {
        // Authentication method is not supported
        $uri->userinfo = null;
        // file:// makes no provisions for accessing the resource
        $uri->port     = null;
        // While it seems to work on Firefox, the querystring has
        // no possible effect and is thus stripped.
        $uri->query    = null;
        return true;
    }

}

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