Implement %Attr.AllowedClasses and %Attr.ForbiddenClasses.

Signed-off-by: Edward Z. Yang <edwardzyang@thewritingpot.com>

NEWS

@@ -31,6 +31,9 @@ NEWS ( CHANGELOG and HISTORY )                                     HTMLPurifier
   tags that contain non-breaking spaces as well other whitespace. You
   can also modify which tags should have   maintained with
   %AutoFormat.RemoveEmpty.RemoveNbsp.Exceptions.
+! Implement %Attr.AllowedClasses, which allows administrators to restrict
+  classes users can use to a specified finite set of classes, and
+  %Attr.ForbiddenClasses, which is the logical inverse.
 . Created script maintenance/rename-config.php for renaming a configuration
   directive while maintaining its alias.  This script does not change source code.
 

TODO

@@ -17,10 +17,11 @@ afraid to cast your vote for the next feature to be implemented!
 - Incorporate data: support as implemented here:
   http://htmlpurifier.org/phorum/read.php?3,3491,3548
 - Fix ImgRequired to handle data correctly
-- Provide callback/lookup table of allowed class attributes
 - Think about allowing explicit order of operations hooks for transforms
 - Allow more relaxed "class" definition than NMTOKENS for appropriate
   doctypes
+- Lock when configuring Definition objects so we CAN'T access configuration
+  directives outside of what dependency has been registered.
 
 FUTURE VERSIONS
 ---------------

library/HTMLPurifier.includes.php

@@ -98,6 +98,8 @@ require 'HTMLPurifier/AttrDef/CSS/Percentage.php';
 require 'HTMLPurifier/AttrDef/CSS/TextDecoration.php';
 require 'HTMLPurifier/AttrDef/CSS/URI.php';
 require 'HTMLPurifier/AttrDef/HTML/Bool.php';
+require 'HTMLPurifier/AttrDef/HTML/Nmtokens.php';
+require 'HTMLPurifier/AttrDef/HTML/Class.php';
 require 'HTMLPurifier/AttrDef/HTML/Color.php';
 require 'HTMLPurifier/AttrDef/HTML/FrameTarget.php';
 require 'HTMLPurifier/AttrDef/HTML/ID.php';
@@ -105,7 +107,6 @@ require 'HTMLPurifier/AttrDef/HTML/Pixels.php';
 require 'HTMLPurifier/AttrDef/HTML/Length.php';
 require 'HTMLPurifier/AttrDef/HTML/LinkTypes.php';
 require 'HTMLPurifier/AttrDef/HTML/MultiLength.php';
-require 'HTMLPurifier/AttrDef/HTML/Nmtokens.php';
 require 'HTMLPurifier/AttrDef/URI/Email.php';
 require 'HTMLPurifier/AttrDef/URI/Host.php';
 require 'HTMLPurifier/AttrDef/URI/IPv4.php';

library/HTMLPurifier.safe-includes.php

@@ -92,6 +92,8 @@ require_once $__dir . '/HTMLPurifier/AttrDef/CSS/Percentage.php';
 require_once $__dir . '/HTMLPurifier/AttrDef/CSS/TextDecoration.php';
 require_once $__dir . '/HTMLPurifier/AttrDef/CSS/URI.php';
 require_once $__dir . '/HTMLPurifier/AttrDef/HTML/Bool.php';
+require_once $__dir . '/HTMLPurifier/AttrDef/HTML/Nmtokens.php';
+require_once $__dir . '/HTMLPurifier/AttrDef/HTML/Class.php';
 require_once $__dir . '/HTMLPurifier/AttrDef/HTML/Color.php';
 require_once $__dir . '/HTMLPurifier/AttrDef/HTML/FrameTarget.php';
 require_once $__dir . '/HTMLPurifier/AttrDef/HTML/ID.php';
@@ -99,7 +101,6 @@ require_once $__dir . '/HTMLPurifier/AttrDef/HTML/Pixels.php';
 require_once $__dir . '/HTMLPurifier/AttrDef/HTML/Length.php';
 require_once $__dir . '/HTMLPurifier/AttrDef/HTML/LinkTypes.php';
 require_once $__dir . '/HTMLPurifier/AttrDef/HTML/MultiLength.php';
-require_once $__dir . '/HTMLPurifier/AttrDef/HTML/Nmtokens.php';
 require_once $__dir . '/HTMLPurifier/AttrDef/URI/Email.php';
 require_once $__dir . '/HTMLPurifier/AttrDef/URI/Host.php';
 require_once $__dir . '/HTMLPurifier/AttrDef/URI/IPv4.php';

library/HTMLPurifier/AttrDef/HTML/Class.php

@@ -0,0 +1,22 @@
+<?php
+
+/**
+ * Implements special behavior for class attribute (normally NMTOKENS)
+ */
+class HTMLPurifier_AttrDef_HTML_Class extends HTMLPurifier_AttrDef_HTML_Nmtokens
+{
+    protected function filter($tokens, $config, $context) {
+        $allowed = $config->get('Attr.AllowedClasses');
+        $forbidden = $config->get('Attr.ForbiddenClasses');
+        $ret = array();
+        foreach ($tokens as $token) {
+            if (
+                ($allowed === null || isset($allowed[$token])) &&
+                !isset($forbidden[$token])
+            ) {
+                $ret[] = $token;
+            }
+        }
+        return $ret;
+    }
+}

library/HTMLPurifier/AttrDef/HTML/Nmtokens.php

@@ -2,10 +2,6 @@
 
 /**
  * Validates contents based on NMTOKENS attribute type.
- * @note The only current use for this is the class attribute in HTML
- * @note Could have some functionality factored out into Nmtoken class
- * @warning We cannot assume this class will be used only for 'class'
- *          attributes. Not sure how to hook in magic behavior, then.
  */
 class HTMLPurifier_AttrDef_HTML_Nmtokens extends HTMLPurifier_AttrDef
 {
@@ -17,6 +13,17 @@ class HTMLPurifier_AttrDef_HTML_Nmtokens extends HTMLPurifier_AttrDef
         // early abort: '' and '0' (strings that convert to false) are invalid
         if (!$string) return false;
 
+        $tokens = $this->split($string);
+        $tokens = $this->filter($tokens, $config, $context);
+        if (empty($tokens)) return false;
+        return implode(' ', $tokens);
+
+    }
+
+    /**
+     * Splits a space separated list of tokens into its constituent parts.
+     */
+    protected function split($string) {
         // OPTIMIZABLE!
         // do the preg_match, capture all subpatterns for reformulation
 
@@ -24,23 +31,20 @@ class HTMLPurifier_AttrDef_HTML_Nmtokens extends HTMLPurifier_AttrDef
         // escaping because I don't know how to do that with regexps
         // and plus it would complicate optimization efforts (you never
         // see that anyway).
-        $matches = array();
         $pattern = '/(?:(?<=\s)|\A)'. // look behind for space or string start
                    '((?:--|-?[A-Za-z_])[A-Za-z_\-0-9]*)'.
                    '(?:(?=\s)|\z)/'; // look ahead for space or string end
         preg_match_all($pattern, $string, $matches);
-
-        if (empty($matches[1])) return false;
-
-        // reconstruct string
-        $new_string = '';
-        foreach ($matches[1] as $token) {
-            $new_string .= $token . ' ';
+        return $matches[1];
     }
-        $new_string = rtrim($new_string);
-
-        return $new_string;
 
+    /**
+     * Template method for removing certain tokens based on arbitrary criteria.
+     * @note If we wanted to be really functional, we'd do an array_filter
+     *       with a callback. But... we're not.
+     */
+    protected function filter($tokens, $config, $context) {
+        return $tokens;
     }
 
 }

library/HTMLPurifier/AttrTypes.php

@@ -36,6 +36,9 @@ class HTMLPurifier_AttrTypes
         $this->info['Charsets'] = new HTMLPurifier_AttrDef_Text();
         $this->info['Character'] = new HTMLPurifier_AttrDef_Text();
 
+        // "proprietary" types
+        $this->info['Class'] = new HTMLPurifier_AttrDef_HTML_Class();
+
         // number is really a positive integer (one or more digits)
         // FIXME: ^^ not always, see start and value of list items
         $this->info['Number']   = new HTMLPurifier_AttrDef_Integer(false, false, true);

library/HTMLPurifier/ConfigSchema/schema/Attr.AllowedClasses.txt

@@ -0,0 +1,8 @@
+Attr.AllowedClasses
+TYPE: lookup/null
+VERSION: 4.0.0
+DEFAULT: null
+--DESCRIPTION--
+List of allowed class values in the class attribute. By default, this is null,
+which means all classes are allowed.
+--# vim: et sw=4 sts=4

library/HTMLPurifier/ConfigSchema/schema/Attr.ForbiddenClasses.txt

@@ -0,0 +1,8 @@
+Attr.ForbiddenClasses
+TYPE: lookup
+VERSION: 4.0.0
+DEFAULT: array()
+--DESCRIPTION--
+List of forbidden class values in the class attribute. By default, this is
+empty, which means that no classes are forbidden. See also %Attr.AllowedClasses.
+--# vim: et sw=4 sts=4

library/HTMLPurifier/HTMLModule/CommonAttributes.php

@@ -8,7 +8,7 @@ class HTMLPurifier_HTMLModule_CommonAttributes extends HTMLPurifier_HTMLModule
         'Core' => array(
             0 => array('Style'),
             // 'xml:space' => false,
-            'class' => 'NMTOKENS',
+            'class' => 'Class',
             'id' => 'ID',
             'title' => 'CDATA',
         ),
@@ -20,6 +20,7 @@ class HTMLPurifier_HTMLModule_CommonAttributes extends HTMLPurifier_HTMLModule
             0 => array('Core', 'I18N')
         )
     );
+
 }
 
 // vim: et sw=4 sts=4

tests/HTMLPurifier/AttrDef/HTML/ClassTest.php

@@ -0,0 +1,21 @@
+<?php
+
+class HTMLPurifier_AttrDef_HTML_ClassTest extends HTMLPurifier_AttrDef_HTML_NmtokensTest
+{
+    function setUp() {
+        parent::setUp();
+        $this->def = new HTMLPurifier_AttrDef_HTML_Class();
+    }
+    function testAllowedClasses() {
+        $this->config->set('Attr.AllowedClasses', array('foo'));
+        $this->assertDef('foo');
+        $this->assertDef('bar', false);
+        $this->assertDef('foo bar', 'foo');
+    }
+    function testForbiddenClasses() {
+        $this->config->set('Attr.ForbiddenClasses', array('bar'));
+        $this->assertDef('foo');
+        $this->assertDef('bar', false);
+        $this->assertDef('foo bar', 'foo');
+    }
+}

tests/HTMLPurifier/AttrDef/HTML/NmtokensTest.php

@@ -3,9 +3,12 @@
 class HTMLPurifier_AttrDef_HTML_NmtokensTest extends HTMLPurifier_AttrDefHarness
 {
 
-    function testDefault() {
-
+    function setUp() {
+        parent::setUp();
         $this->def = new HTMLPurifier_AttrDef_HTML_Nmtokens();
+    }
+
+    function testDefault() {
 
         $this->assertDef('valid');
         $this->assertDef('a0-_');