<?php
/**
* Validates the HTML attribute style, otherwise known as CSS.
* @note We don't implement the whole CSS specification, so it might be
* difficult to reuse this component in the context of validating
* actual stylesheet declarations.
* @note If we were really serious about validating the CSS, we would
* tokenize the styles and then parse the tokens. Obviously, we
* are not doing that. Doing that could seriously harm performance,
* but would make these components a lot more viable for a CSS
* filtering solution.
*/
class HTMLPurifier_AttrDef_CSS extends HTMLPurifier_AttrDef
{
/**
* @param string $css
* @param HTMLPurifier_Config $config
* @param HTMLPurifier_Context $context
* @return bool|string
*/
public function validate($css, $config, $context)
{
$css = $this->parseCDATA($css);
$definition = $config->getCSSDefinition();
$allow_duplicates = $config->get("CSS.AllowDuplicates");
// According to the CSS2.1 spec, the places where a
// non-delimiting semicolon can appear are in strings
// escape sequences. So here is some dumb hack to
// handle quotes.
$len = strlen($css);
$accum = "";
$declarations = array();
$quoted = false;
for ($i = 0; $i < $len; $i++) {
$c = strcspn($css, ";'\"", $i);
$accum .= substr($css, $i, $c);
$i += $c;
if ($i == $len) break;
$d = $css[$i];
if ($quoted) {
$accum .= $d;
if ($d == $quoted) {
$quoted = false;
}
} else {
if ($d == ";") {
$declarations[] = $accum;
$accum = "";
} else {
$accum .= $d;
$quoted = $d;
}
}
}
if ($accum != "") $declarations[] = $accum;
$propvalues = array();
$new_declarations = '';
/**
* Name of the current CSS property being validated.
*/
$property = false;
$context->register('CurrentCSSProperty', $property);
foreach ($declarations as $declaration) {
if (!$declaration) {
continue;
}
if (!strpos($declaration, ':')) {
continue;
}
list($property, $value) = explode(':', $declaration, 2);
$property = trim($property);
$value = trim($value);
$ok = false;
do {
if (isset($definition->info[$property])) {
$ok = true;
break;
}
if (ctype_lower($property)) {
break;
}
$property = strtolower($property);
if (isset($definition->info[$property])) {
$ok = true;
break;
}
} while (0);
if (!$ok) {
continue;
}
// inefficient call, since the validator will do this again
if (strtolower(trim($value)) !== 'inherit') {
// inherit works for everything (but only on the base property)
$result = $definition->info[$property]->validate(
$value,
$config,
$context
);
} else {
$result = 'inherit';
}
if ($result === false) {
continue;
}
if ($allow_duplicates) {
$new_declarations .= "$property:$result;";
} else {
$propvalues[$property] = $result;
}
}
$context->destroy('CurrentCSSProperty');
// procedure does not write the new CSS simultaneously, so it's
// slightly inefficient, but it's the only way of getting rid of
// duplicates. Perhaps config to optimize it, but not now.
foreach ($propvalues as $prop => $value) {
$new_declarations .= "$prop:$value;";
}
return $new_declarations ? $new_declarations : false;
}
}
// vim: et sw=4 sts=4