" characters. * * @param string $string Content to filter * @param array $allowed_html Allowed HTML elements * @param array $allowed_protocols Allowed protocols to keep * @return string Content with fixed HTML tags */ function kses_split($string, $allowed_html, $allowed_protocols) { global $pass_allowed_html, $pass_allowed_protocols; $pass_allowed_html = $allowed_html; $pass_allowed_protocols = $allowed_protocols; return preg_replace_callback( '%((|$))|(<[^>]*(>|$)|>))%', '_kses_split_callback', $string ); } /** * Callback for kses_split. * * @access private */ function _kses_split_callback( $match ) { global $pass_allowed_html, $pass_allowed_protocols; return kses_split2( $match[1], $pass_allowed_html, $pass_allowed_protocols ); } /** * Callback for kses_split for fixing malformed HTML tags. * * 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. * * After the tag is split into an element and an attribute list, it is run * through another filter which will remove illegal attributes and once that is * completed, will be returned. * * @access private * @uses kses_attr() * * @param string $string Content to filter * @param array $allowed_html Allowed HTML elements * @param array $allowed_protocols Allowed protocols to keep * @return string Fixed HTML element */ function kses_split2($string, $allowed_html, $allowed_protocols) { $string = kses_stripslashes($string); if (substr($string, 0, 1) != '<') return '>'; // It matched a ">" character if (preg_match('%^)?$%', $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 $string = preg_replace('/-$/', '', $string); return ""; } // Allow HTML comments if (!preg_match('%^<\s*(/\s*)?([a-zA-Z0-9]+)([^>]*)>?$%', $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 HTML element/tag * @param string $attr HTML attributes from HTML element to closing HTML element tag * @param array $allowed_html Allowed HTML elements * @param array $allowed_protocols Allowed protocols to keep * @return string Sanitized HTML element */ function kses_attr($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)) { $ok = false; break; } if ( strtolower($arreach['name']) == 'style' ) { $orig_value = $arreach['value']; $value = kses_safecss_filter_attr($orig_value); if ( empty($value) ) continue; $arreach['value'] = $value; $arreach['whole'] = str_replace($orig_value, $value, $arreach['whole']); } if ($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. * It also reduces duplicate attributes by using the * attribute defined first (foo='bar' foo='baz' will result in foo='bar'). * * @param string $attr Attribute list from HTML element to closing HTML element tag * @param array $allowed_protocols Allowed protocols to keep * @return array List of attributes after parsing */ function kses_hair($attr, $allowed_protocols) { $attrarr = array(); $mode = 0; $attrname = ''; $uris = array('xmlns', 'profile', 'href', 'src', 'cite', 'classid', 'codebase', 'data', 'usemap', 'longdesc', 'action'); // Loop through the whole attribute list while (strlen($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; $mode = 0; if(FALSE === array_key_exists($attrname, $attrarr)) { $attrarr[$attrname] = 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 = $match[1]; if ( in_array(strtolower($attrname), $uris) ) $thisval = kses_bad_protocol($thisval, $allowed_protocols); } if(FALSE === array_key_exists($attrname, $attrarr)) { $attrarr[$attrname] = 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 = $match[1]; if ( in_array(strtolower($attrname), $uris) ) $thisval = kses_bad_protocol($thisval, $allowed_protocols); if(FALSE === array_key_exists($attrname, $attrarr)) { $attrarr[$attrname] = 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 = $match[1]; if ( in_array(strtolower($attrname), $uris) ) $thisval = kses_bad_protocol($thisval, $allowed_protocols); if(FALSE === array_key_exists($attrname, $attrarr)) { $attrarr[$attrname] = 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 && FALSE === array_key_exists($attrname, $attrarr)) // special case, for when the attribute list ends with a valueless // attribute like "selected" $attrarr[$attrname] = 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 Attribute value * @param string $vless Whether the value is valueless. Use 'y' or 'n' * @param string $checkname What $checkvalue is checking for. * @param mixed $checkvalue What constraint the value should pass * @return bool Whether check passes */ function kses_check_attr_val($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) $ok = false; break; case 'valueless': // The valueless check checks if the attribute has a value // (like ) or not (). If the given value // is a "y" or a "Y", the attribute must not have a value. // If the given value is an "n" or an "N", the attribute must have one. if (strtolower($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 Content to filter bad protocols from * @param array $allowed_protocols Allowed protocols to keep * @return string Filtered content */ function kses_bad_protocol($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 $string String to strip slashes * @return string Fixed strings with quoted slashes */ function kses_stripslashes($string) { return preg_replace('%\\\\"%', '"', $string); } /** * This function goes through an array, and changes the keys to all lower case. * * @param array $inarray Unfiltered array * @return array Fixed array with all lowercase keys */ function kses_array_lc($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 $string * @return string */ function kses_js_entities($string) { return preg_replace('%&\s*\{[^}]*(\}\s*;?|$)%', '', $string); } /** * This function handles 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 Content to check for bad protocols * @param string $allowed_protocols Allowed protocols * @return string Sanitized content */ function kses_bad_protocol_once($string, $allowed_protocols) { $string2 = preg_split('/:|�*58;|�*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. * * @access private * * @param string $string URI scheme to check against the whitelist * @param string $allowed_protocols Allowed protocols * @return string Sanitized content */ function kses_bad_protocol_once2($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&T", ":" to ":", "&#XYZZY;" to "&#XYZZY;" and so on. * * @param string $string Content to normalize entities * @return string Content with normalized entities */ function kses_normalize_entities($string) { // Disarm all entities by converting & to & $string = str_replace('&', '&', $string); // Change back the allowed entities in our entity whitelist $string = preg_replace_callback('/&([A-Za-z]{2,8});/', 'kses_named_entities', $string); $string = preg_replace_callback('/&#(0*[0-9]{1,7});/', 'kses_normalize_entities2', $string); $string = preg_replace_callback('/&#[Xx](0*[0-9A-Fa-f]{1,6});/', 'kses_normalize_entities3', $string); return $string; } /** * Callback for kses_normalize_entities() regular expression. * * This function only accepts valid named entity references, which are finite, * case-sensitive, and highly scrutinized by HTML and XML validators. * * @since 3.0.0 * * @param array $matches preg_replace_callback() matches array * @return string Correctly encoded entity */ function kses_named_entities($matches) { global $kses_allowedentitynames; if ( empty($matches[1]) ) return ''; $i = $matches[1]; return ( ( ! in_array($i, $kses_allowedentitynames) ) ? "&$i;" : "&$i;" ); } /** * Callback for kses_normalize_entities() regular expression. * * This function helps kses_normalize_entities() to only accept 16 bit values * and nothing more for &#number; entities. * * @access private * * @param array $matches preg_replace_callback() matches array * @return string Correctly encoded entity */ function kses_normalize_entities2($matches) { if ( empty($matches[1]) ) return ''; $i = $matches[1]; if (kses_valid_unicode($i)) { $i = str_pad(ltrim($i,'0'), 3, '0', STR_PAD_LEFT); $i = "&#$i;"; } else { $i = "&#$i;"; } return $i; } /** * Callback for kses_normalize_entities() for regular expression. * * This function helps kses_normalize_entities() to only accept valid Unicode * numeric entities in hex form. * * @access private * * @param array $matches preg_replace_callback() matches array * @return string Correctly encoded entity */ function kses_normalize_entities3($matches) { if ( empty($matches[1]) ) return ''; $hexchars = $matches[1]; return ( ( ! kses_valid_unicode(hexdec($hexchars)) ) ? "&#x$hexchars;" : '&#x'.ltrim($hexchars,'0').';' ); } /** * Helper function to determine if a Unicode value is valid. * * @param int $i Unicode value * @return bool true if the value was a valid Unicode number */ function kses_valid_unicode($i) { return ( $i == 0x9 || $i == 0xa || $i == 0xd || ($i >= 0x20 && $i <= 0xd7ff) || ($i >= 0xe000 && $i <= 0xfffd) || ($i >= 0x10000 && $i <= 0x10ffff) ); } /** * Convert all entities to their character counterparts. * * This function decodes numeric HTML entities (A and A). It doesn't do * anything with other entities like ä, but we don't need them in the URL * protocol whitelisting system anyway. * * @param string $string Content to change entities * @return string Content after decoded entities */ function kses_decode_entities($string) { $string = preg_replace_callback('/&#([0-9]+);/', '_kses_decode_entities_chr', $string); $string = preg_replace_callback('/&#[Xx]([0-9A-Fa-f]+);/', '_kses_decode_entities_chr_hexdec', $string); return $string; } /** * Regex callback for kses_decode_entities() * * @param array $match preg match * @return string */ function _kses_decode_entities_chr( $match ) { return chr( $match[1] ); } /** * Regex callback for kses_decode_entities() * * @param array $match preg match * @return string */ function _kses_decode_entities_chr_hexdec( $match ) { return chr( hexdec( $match[1] ) ); } /** * Inline CSS filter * */ function kses_safecss_filter_attr( $css ) { $css = kses_no_null($css); $css = str_replace(array("\n","\r","\t"), '', $css); if ( preg_match( '%[\\(&=}]|/\*%', $css ) ) // remove any inline css containing \ ( & } = or comments return ''; $css_array = explode( ';', trim( $css ) ); $allowed_attr = array( 'text-align', 'margin', 'color', 'float', 'border', 'background', 'background-color', 'border-bottom', 'border-bottom-color', 'border-bottom-style', 'border-bottom-width', 'border-collapse', 'border-color', 'border-left', 'border-left-color', 'border-left-style', 'border-left-width', 'border-right', 'border-right-color', 'border-right-style', 'border-right-width', 'border-spacing', 'border-style', 'border-top', 'border-top-color', 'border-top-style', 'border-top-width', 'border-width', 'caption-side', 'clear', 'cursor', 'direction', 'display', 'font', 'font-family', 'font-size', 'font-style', 'font-variant', 'font-weight', 'height', 'letter-spacing', 'line-height', 'margin-bottom', 'margin-left', 'margin-right', 'margin-top', 'overflow', 'padding', 'padding-bottom', 'padding-left', 'padding-right', 'padding-top', 'text-decoration', 'text-indent', 'vertical-align', 'width' ); if ( empty($allowed_attr) ) return $css; $css = ''; foreach ( $css_array as $css_item ) { if ( $css_item == '' ) continue; $css_item = trim( $css_item ); $found = false; if ( strpos( $css_item, ':' ) === false ) { $found = true; } else { $parts = split( ':', $css_item ); if ( in_array( strtolower( trim( $parts[0] ) ), $allowed_attr ) ) $found = true; } if ( $found ) { if( $css != '' ) $css .= ';'; $css .= $css_item; } } return $css; }