Tighter CSS selector validation.

Signed-off-by: Edward Z. Yang <ezyang@mit.edu>

library/HTMLPurifier/AttrDef/CSS/Ident.php

@@ -0,0 +1,24 @@
+<?php
+
+/**
+ * Validates based on {ident} CSS grammar production
+ */
+class HTMLPurifier_AttrDef_CSS_Ident extends HTMLPurifier_AttrDef
+{
+
+    public function validate($string, $config, $context) {
+
+        $string = trim($string);
+
+        // early abort: '' and '0' (strings that convert to false) are invalid
+        if (!$string) return false;
+
+        $pattern = '/^(-?[A-Za-z_][A-Za-z_\-0-9]*)$/';
+        if (!preg_match($pattern, $string)) return false;
+        return $string;
+
+    }
+
+}
+
+// vim: et sw=4 sts=4