chamilo-lms/main/inc/lib/kses-0.2.2/kses.php

<?php
/**
 * kses 0.2.2 - HTML/XHTML filter that only allows some elements and attributes
 * Copyright (C) 2002, 2003, 2005  Ulf Harnhammar
 *
 * This program is free software and open source software; you can redistribute
 * it and/or modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation; either version 3 of the License,
 * or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
 * more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA  or visit
 * http://www.gnu.org/licenses/gpl.html
 *
 * *** CONTACT INFORMATION ***
 *
 * E-mail:      metaur at users dot sourceforge dot net
 * Web page:    http://sourceforge.net/projects/kses
 * Paper mail:  Ulf Harnhammar
 *              Ymergatan 17 C
 *              753 25  Uppsala
 *              SWEDEN
 *
 * [kses strips evil scripts!]
 *
 * @package   chamilo.kses
 * @copyright Ulf Harnhammar  {@link http://sourceforge.net/projects/kses}
 * @license   http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 */

/**
 * This function makes sure that only the allowed HTML element names, attribute
 * names and attribute values plus only sane HTML entities will occur in
 * $string. You have to remove any slashes from PHP's magic quotes before you
 * call this function.
 *
 * @param string $string
 * @param string $allowed_html
 * @param array $allowed_protocols
 * @return string
 */
function kses($string, $allowed_html, $allowed_protocols =
               array('http', 'https', 'ftp', 'news', 'nntp', 'telnet',
                     'gopher', 'mailto'))
{
    $string = kses_no_null($string);
    $string = kses_js_entities($string);
    $string = kses_normalize_entities($string);
    $string = kses_hook($string);
    $allowed_html_fixed = kses_array_lc($allowed_html);
    return kses_split($string, $allowed_html_fixed, $allowed_protocols);
}


/**
 * You add any kses hooks here.
 *
 * @param string $string
 * @return string
 */
function kses_hook($string)
{
    return $string;
}

/**
 * This function returns kses' version number.
 *
 * @return string
 */
function kses_version()
{
    return '0.2.2';
}


/**
 * This function searches for HTML tags, no matter how malformed.
 * It also matches stray ">" characters.
 *
 * @param string $string
 * @param string $allowed_html
 * @param array $allowed_protocols
 * @return string
 */
function kses_split($string, $allowed_html, $allowed_protocols)
{
    return preg_replace('%(<'.   // EITHER: <
                      '[^>]*'. // things that aren't >
                      '(>|$)'. // > or end of string
                      '|>)%e', // OR: just a >
                      "kses_split2('\\1', \$allowed_html, ".
                      '$allowed_protocols)',
                      $string);
}

/**
 * This function does a lot of work. It rejects some very malformed things
 * like <:::>. It returns an empty string, if the element isn't allowed (look
 * ma, no strip_tags()!). Otherwise it splits the tag into an element and an
 * attribute list.
 *
 * @param string $string
 * @param string $allowed_html
 * @param array $allowed_protocols
 * @return string
 */
function kses_split2($string, $allowed_html, $allowed_protocols)
{
    $string = kses_stripslashes($string);

    if (substr($string, 0, 1) != '<')
        return '&gt;';
    // It matched a ">" character

    if (preg_match('%^<!--(.*?)(-->)?$%', $string, $matches)) {
        $string = str_replace(array('<!--', '-->'), '', $matches[1]);
        while ( $string != $newstring = kses($string, $allowed_html, $allowed_protocols) )
            $string = $newstring;
        if ( $string == '' )
            return '';
        // prevent multiple dashes in comments
        $string = preg_replace('/--+/', '-', $string);
        // prevent three dashes closing a comment
        $string = preg_replace('/-$/', '', $string);
        return "<!--{$string}-->";
    }
    // Allow HTML comments

    if (!preg_match('%^<\s*(/\s*)?([a-zA-Z0-9]+)([^>]*)>?$%', $string, $matches))
        return '';
    // It's seriously malformed

    $slash = trim($matches[1]);
    $elem = $matches[2];
    $attrlist = $matches[3];

    if (!@isset($allowed_html[strtolower($elem)]))
        return '';
    // They are using a not allowed HTML element

    if ($slash != '')
        return "<$slash$elem>";
    // No attributes are allowed for closing elements

    return kses_attr("$slash$elem", $attrlist, $allowed_html,
                   $allowed_protocols);
}

/**
 * This function removes all attributes, if none are allowed for this element.
 * If some are allowed it calls kses_hair() to split them further, and then it
 * builds up new HTML code from the data that kses_hair() returns. It also
 * removes "<" and ">" characters, if there are any left. One more thing it
 * does is to check if the tag has a closing XHTML slash, and if it does,
 * it puts one in the returned code as well.
 *
 * @param string $element
 * @param string $attr
 * @param string $allowed_html
 * @param array $allowed_protocols
 * @return string
 */
function kses_attr($element, $attr, $allowed_html, $allowed_protocols)
{
    // Is there a closing XHTML slash at the end of the attributes?

    $xhtml_slash = '';
    if (preg_match('%\s*/\s*$%', $attr))
        $xhtml_slash = ' /';

    // Are any attributes allowed at all for this element?

    if (@count($allowed_html[strtolower($element)]) == 0)
        return "<$element$xhtml_slash>";

    // Split it

    $attrarr = kses_hair($attr, $allowed_protocols);

    // Go through $attrarr, and save the allowed attributes for this element
    // in $attr2

    $attr2 = '';

    foreach ($attrarr as $arreach)
    {
        if (!@isset($allowed_html[strtolower($element)]
                              [strtolower($arreach['name'])]))
            continue; // the attribute is not allowed

        $current = $allowed_html[strtolower($element)]
                              [strtolower($arreach['name'])];
        if ($current == '')
            continue; // the attribute is not allowed

        if (!is_array($current))
            $attr2 .= ' '.$arreach['whole'];
        // there are no checks

        else
        {
            // there are some checks
            $ok = true;
            foreach ($current as $currkey => $currval)
                if (!kses_check_attr_val($arreach['value'], $arreach['vless'],
                                 $currkey, $currval))
                { $ok = false; break; }

            if ($ok)
                $attr2 .= ' '.$arreach['whole']; // it passed them
        } // if !is_array($current)
    } // foreach

    // Remove any "<" or ">" characters

    $attr2 = preg_replace('/[<>]/', '', $attr2);

    return "<$element$attr2$xhtml_slash>";
}

/**
 * Builds an attribute list from string containing attributes.
 *
 * This function does a lot of work. It parses an attribute list into an array
 * with attribute data, and tries to do the right thing even if it gets weird
 * input. It will add quotes around attribute values that don't have any quotes
 * or apostrophes around them, to make it easier to produce HTML code that will
 * conform to W3C's HTML specification. It will also remove bad URL protocols
 * from attribute values.
 *
 * @param string $attr
 * @param array $allowed_protocols
 * @return array
 */
function kses_hair($attr, $allowed_protocols)
{
    $attrarr = array();
    $mode = 0;
    $attrname = '';

    // Loop through the whole attribute list

    while (strlen($attr) != 0)
    {
        $working = 0; // Was the last operation successful?

        switch ($mode)
        {
            case 0: // attribute name, href for instance

                if (preg_match('/^([-a-zA-Z]+)/', $attr, $match))
                {
                    $attrname = $match[1];
                    $working = $mode = 1;
                    $attr = preg_replace('/^[-a-zA-Z]+/', '', $attr);
                }

                break;

            case 1: // equals sign or valueless ("selected")

                if (preg_match('/^\s*=\s*/', $attr)) // equals sign
                {
                    $working = 1; $mode = 2;
                    $attr = preg_replace('/^\s*=\s*/', '', $attr);
                    break;
                }

                if (preg_match('/^\s+/', $attr)) // valueless
                {
                    $working = 1; $mode = 0;
                    $attrarr[] = array
                        ('name'  => $attrname,
                         'value' => '',
                         'whole' => $attrname,
                         'vless' => 'y');
                    $attr = preg_replace('/^\s+/', '', $attr);
                }

                break;

            case 2: // attribute value, a URL after href= for instance

                if (preg_match('%^"([^"]*)"(\s+|/?$)%', $attr, $match))
                    // "value"
                {
                    // MDL-2684 - kses stripping CSS styles that it thinks look like protocols
                    if ($attrname == 'style') {
                        $thisval = $match[1];
                    } else {
                        $thisval = kses_bad_protocol($match[1], $allowed_protocols);
                    }

                    $attrarr[] = array
                        ('name'  => $attrname,
                         'value' => $thisval,
                         'whole' => "$attrname=\"$thisval\"",
                         'vless' => 'n');
                    $working = 1; $mode = 0;
                    $attr = preg_replace('/^"[^"]*"(\s+|$)/', '', $attr);
                    break;
                }

                if (preg_match("%^'([^']*)'(\s+|/?$)%", $attr, $match))
                    // 'value'
                {
                    $thisval = kses_bad_protocol($match[1], $allowed_protocols);

                    $attrarr[] = array
                        ('name'  => $attrname,
                         'value' => $thisval,
                         'whole' => "$attrname='$thisval'",
                         'vless' => 'n');
                    $working = 1; $mode = 0;
                    $attr = preg_replace("/^'[^']*'(\s+|$)/", '', $attr);
                    break;
                }

                if (preg_match("%^([^\s\"']+)(\s+|/?$)%", $attr, $match))
                    // value
                {
                    $thisval = kses_bad_protocol($match[1], $allowed_protocols);

                    $attrarr[] = array
                        ('name'  => $attrname,
                         'value' => $thisval,
                         'whole' => "$attrname=\"$thisval\"",
                         'vless' => 'n');
                    // We add quotes to conform to W3C's HTML spec.
                    $working = 1; $mode = 0;
                    $attr = preg_replace("%^[^\s\"']+(\s+|$)%", '', $attr);
                }

                break;
        } // switch

        if ($working == 0) // not well formed, remove and try again
        {
            $attr = kses_html_error($attr);
            $mode = 0;
        }
    } // while

    if ($mode == 1)
        // special case, for when the attribute list ends with a valueless
        // attribute like "selected"
        $attrarr[] = array
                  ('name'  => $attrname,
                   'value' => '',
                   'whole' => $attrname,
                   'vless' => 'y');

    return $attrarr;
}

/**
 * This function performs different checks for attribute values. The currently
 * implemented checks are "maxlen", "minlen", "maxval", "minval" and "valueless"
 * with even more checks to come soon.
 *
 * @param string $value
 * @param string $vless
 * @param string $checkname
 * @param string $checkvalue
 * @return bool
 */
function kses_check_attr_val($value, $vless, $checkname, $checkvalue)
{
    $ok = true;

    switch (strtolower($checkname))
    {
        case 'maxlen':
            // The maxlen check makes sure that the attribute value has a length not
            // greater than the given value. This can be used to avoid Buffer Overflows
            // in WWW clients and various Internet servers.

            if (strlen($value) > $checkvalue)
                $ok = false;
            break;

        case 'minlen':
            // The minlen check makes sure that the attribute value has a length not
            // smaller than the given value.

            if (strlen($value) < $checkvalue)
                $ok = false;
            break;

        case 'maxval':
            // The maxval check does two things: it checks that the attribute value is
            // an integer from 0 and up, without an excessive amount of zeroes or
            // whitespace (to avoid Buffer Overflows). It also checks that the attribute
            // value is not greater than the given value.
            // This check can be used to avoid Denial of Service attacks.

            if (!preg_match('/^\s{0,6}[0-9]{1,6}\s{0,6}$/', $value))
                $ok = false;
            if ($value > $checkvalue)
                $ok = false;
            break;

        case 'minval':
            // The minval check checks that the attribute value is a positive integer,
            // and that it is not smaller than the given value.

            if (!preg_match('/^\s{0,6}[0-9]{1,6}\s{0,6}$/', $value))
                $ok = false;
            if ($value < $checkvalue)
                $ok = false;
            break;

        case 'valueless':
            // The valueless check checks if the attribute has a value
            // (like <a href="blah">) or not (<option selected>). If the given value
            // is a "y" or a "Y", the attribute must not have a value.
            // If the given value is an "n" or an "N", the attribute must have one.

            if (strtolower($checkvalue) != $vless)
                $ok = false;
            break;
    } // switch

    return $ok;
}

/**
 * Sanitize string from bad protocols.
 *
 * This function removes all non-allowed protocols from the beginning of
 * $string. It ignores whitespace and the case of the letters, and it does
 * understand HTML entities. It does its work in a while loop, so it won't be
 * fooled by a string like "javascript:javascript:alert(57)".
 *
 * @param string $string
 * @param array $$allowed_protocols
 * @return string
 */
function kses_bad_protocol($string, $allowed_protocols)
{
    $string = kses_no_null($string);
    $string = preg_replace('/([^\xc3-\xcf])\xad+/', '\\1', $string); // deals with Opera "feature" -- moodle utf8 fix
    $string2 = $string.'a';

    while ($string != $string2)
    {
        $string2 = $string;
        $string = kses_bad_protocol_once($string, $allowed_protocols);
    } // while

    return $string;
}

/**
 * This function removes any NULL characters in $string.
 *
 * @param string $string
 * @return string
 */
function kses_no_null($string)
{
    $string = preg_replace('/\0+/', '', $string);
    $string = preg_replace('/(\\\\0)+/', '', $string);

    return $string;
}


/**
 * Strips slashes from in front of quotes.
 *
 * This function changes the character sequence  \"  to just  "
 * It leaves all other slashes alone. It's really weird, but the quoting from
 * preg_replace(//e) seems to require this.
 *
 * @param string $string
 * @return string
 */
function kses_stripslashes($string)
{
    return preg_replace('%\\\\"%', '"', $string);
}


/**
 * This function goes through an array, and changes the keys to all lower case.
 *
 * @param array $inarray
 * @return array
 */
function kses_array_lc($inarray)
{
    $outarray = array();

    foreach ( (array) $inarray as $inkey => $inval)
    {
        $outkey = strtolower($inkey);
        $outarray[$outkey] = array();

        foreach ( (array) $inval as $inkey2 => $inval2)
        {
            $outkey2 = strtolower($inkey2);
            $outarray[$outkey][$outkey2] = $inval2;
        } // foreach $inval
    } // foreach $inarray

    return $outarray;
}

/**
 * This function removes the HTML JavaScript entities found in early versions of Netscape 4.
 *
 * @param string $string
 */
function kses_js_entities($string)
{
    return preg_replace('%&\s*\{[^}]*(\}\s*;?|$)%', '', $string);
}

/**
 * This function deals with parsing errors in kses_hair().
 * The general plan is to remove everything to and including some whitespace,
 * but it deals with quotes and apostrophes as well.
 *
 * @param string $string
 * @return string
 */
function kses_html_error($string)
{
    return preg_replace('/^("[^"]*("|$)|\'[^\']*(\'|$)|\S)*\s*/', '', $string);
}

/**
 * Sanitizes content from bad protocols and other characters.
 *
 * This function searches for URL protocols at the beginning of $string, while
 * handling whitespace and HTML entities.
 *
 * @param string $string
 * @param string $allowed_protocols
 * @return string
 */
function kses_bad_protocol_once($string, $allowed_protocols)
{
    $string2 = preg_split('/:|&#0*58;|&#x0*3a;/i', $string, 2);
    if(isset($string2[1]) && !preg_match('%/\?%',$string2[0]))
    {
        $string = kses_bad_protocol_once2($string2[0],$allowed_protocols).trim($string2[1]);
    }
    return $string;
}

/**
 * Callback for kses_bad_protocol_once() regular expression.
 *
 * This function processes URL protocols, checks to see if they're in the
 * white-list or not, and returns different data depending on the answer.
 *
 * @param string $string
 * @param string $allowed_protocols
 * @return string
 */
function kses_bad_protocol_once2($string, $allowed_protocols)
{
    $string2 = kses_decode_entities($string);
    $string2 = preg_replace('/\s/', '', $string2);
    $string2 = kses_no_null($string2);
    $string2 = preg_replace('/\xad+/', '', $string2); // deals with Opera "feature"
    $string2 = strtolower($string2);

    $allowed = false;
    foreach ( (array) $allowed_protocols as $one_protocol)
        if (strtolower($one_protocol) == $string2)
        {
            $allowed = true;
            break;
        }

    if ($allowed)
        return "$string2:";
    else
        return '';
}

/**
 * Converts and fixes HTML entities.
 *
 * This function normalizes HTML entities. It will convert "AT&T" to the correct
 * "AT&amp;T", "&#00058;" to "&#58;", "&#XYZZY;" to "&amp;#XYZZY;" and so on.
 *
 * @param string $string
 * @return string
 */
function kses_normalize_entities($string)
{
    // Disarm all entities by converting & to &amp;

    $string = str_replace('&', '&amp;', $string);

    // Change back the allowed entities in our entity whitelist

    $string = preg_replace('/&amp;([A-Za-z][A-Za-z0-9]{0,19});/',
                         '&\\1;', $string);
    $string = preg_replace('/&amp;#0*([0-9]{1,5});/e',
                         'kses_normalize_entities2("\\1")', $string);
    $string = preg_replace('/&amp;#([Xx])0*(([0-9A-Fa-f]{2}){1,2});/',
                         '&#\\1\\2;', $string);

    return $string;
}

/**
 * This function helps kses_normalize_entities() to only accept 16 bit values
 * and nothing more for &#number; entities.
 *
 * @param int $i
 * @return string
 */
function kses_normalize_entities2($i)
{
    return (($i > 65535) ? "&amp;#$i;" : "&#$i;");
}

/**
 * This function decodes numeric HTML entities (&#65; and &#x41;). It doesn't
 * do anything with other entities like &auml;, but we don't need them in the
 * URL protocol whitelisting system anyway.
 *
 * @param string $string
 * @return string
 */
function kses_decode_entities($string)
{
    $string = preg_replace('/&#([0-9]+);/e', 'chr("\\1")', $string);
    $string = preg_replace('/&#[Xx]([0-9A-Fa-f]+);/e', 'chr(hexdec("\\1"))',
                         $string);

    return $string;
}

?>