Implement data URI scheme.

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

NEWS

@@ -12,6 +12,8 @@ NEWS ( CHANGELOG and HISTORY )                                     HTMLPurifier
 4.1.0, unknown release date
 ! Support proprietary height attribute on table element
 ! Support YouTube slideshows that contain /cp/ in their URL.
+! Support for data: URI scheme; not enabled by default, add it using
+  %URI.AllowedSchemes
 
 4.0.0, released 2009-07-07
 # APIs for ConfigSchema subsystem have substantially changed. See

TODO

@@ -13,12 +13,8 @@ afraid to cast your vote for the next feature to be implemented!
 
 Standing patches:
 
- - Incorporate data: support as implemented here:
-   http://htmlpurifier.org/phorum/read.php?3,3491,3548
  - Incorporate download and resize support as implemented here:
    http://htmlpurifier.org/phorum/read.php?3,2795,3628
- - Incorporate remove <span> tags that don't do anything (no attributes):
-   http://htmlpurifier.org/phorum/read.php?5,2507
 
 Things to do as soon as possible:
 

library/HTMLPurifier.includes.php

@@ -199,6 +199,7 @@ require 'HTMLPurifier/URIFilter/DisableExternalResources.php';
 require 'HTMLPurifier/URIFilter/HostBlacklist.php';
 require 'HTMLPurifier/URIFilter/MakeAbsolute.php';
 require 'HTMLPurifier/URIFilter/Munge.php';
+require 'HTMLPurifier/URIScheme/data.php';
 require 'HTMLPurifier/URIScheme/ftp.php';
 require 'HTMLPurifier/URIScheme/http.php';
 require 'HTMLPurifier/URIScheme/https.php';

library/HTMLPurifier.safe-includes.php

@@ -193,6 +193,7 @@ require_once $__dir . '/HTMLPurifier/URIFilter/DisableExternalResources.php';
 require_once $__dir . '/HTMLPurifier/URIFilter/HostBlacklist.php';
 require_once $__dir . '/HTMLPurifier/URIFilter/MakeAbsolute.php';
 require_once $__dir . '/HTMLPurifier/URIFilter/Munge.php';
+require_once $__dir . '/HTMLPurifier/URIScheme/data.php';
 require_once $__dir . '/HTMLPurifier/URIScheme/ftp.php';
 require_once $__dir . '/HTMLPurifier/URIScheme/http.php';
 require_once $__dir . '/HTMLPurifier/URIScheme/https.php';

library/HTMLPurifier/ConfigSchema/schema/URI.AllowedSchemes.txt

@@ -12,4 +12,6 @@ array (
 --DESCRIPTION--
 Whitelist that defines the schemes that a URI is allowed to have.  This
 prevents XSS attacks from using pseudo-schemes like javascript or mocha.
+There is also support for the <code>data</code> URI scheme, but it is not
+enabled by default.
 --# vim: et sw=4 sts=4

library/HTMLPurifier/URIScheme/data.php

@@ -0,0 +1,93 @@
+<?php
+
+/**
+ * Implements data: URI for base64 encoded images supported by GD.
+ */
+class HTMLPurifier_URIScheme_data extends HTMLPurifier_URIScheme {
+
+    public $browsable = true;
+    public $allowed_types = array(
+        // you better write validation code for other types if you
+        // decide to allow them
+        'image/jpeg' => true,
+        'image/gif' => true,
+        'image/png' => true,
+        );
+
+    public function validate(&$uri, $config, $context) {
+        $result = explode(',', $uri->path, 2);
+        $is_base64 = false;
+        $charset = null;
+        $content_type = null;
+        if (count($result) == 2) {
+            list($metadata, $data) = $result;
+            // do some legwork on the metadata
+            $metas = explode(';', $metadata);
+            while(!empty($metas)) {
+                $cur = array_shift($metas);
+                if ($cur == 'base64') {
+                    $is_base64 = true;
+                    break;
+                }
+                if (substr($cur, 0, 8) == 'charset=') {
+                    // doesn't match if there are arbitrary spaces, but
+                    // whatever dude
+                    if ($charset !== null) continue; // garbage
+                    $charset = substr($cur, 8); // not used
+                } else {
+                    if ($content_type !== null) continue; // garbage
+                    $content_type = $cur;
+                }
+            }
+        } else {
+            $data = $result[0];
+        }
+        if ($content_type !== null && empty($this->allowed_types[$content_type])) {
+            return false;
+        }
+        if ($charset !== null) {
+            // error; we don't allow plaintext stuff
+            $charset = null;
+        }
+        $data = rawurldecode($data);
+        if ($is_base64) {
+            $raw_data = base64_decode($data);
+        } else {
+            $raw_data = $data;
+        }
+        // XXX probably want to refactor this into a general mechanism
+        // for filtering arbitrary content types
+        $file = tempnam("/tmp", "");
+        file_put_contents($file, $raw_data);
+        if (function_exists('exif_imagetype')) {
+            $image_code = exif_imagetype($file);
+        } elseif (function_exists('getimagesize')) {
+            set_error_handler(array($this, 'muteErrorHandler'));
+            $info = getimagesize($file);
+            restore_error_handler();
+            if ($info == false) return false;
+            $image_code = $info[2];
+        } else {
+            trigger_error("could not find exif_imagetype or getimagesize functions", E_USER_ERROR);
+        }
+        $real_content_type = image_type_to_mime_type($image_code);
+        if ($real_content_type != $content_type) {
+            // we're nice guys; if the content type is something else we
+            // support, change it over
+            if (empty($this->allowed_types[$real_content_type])) return false;
+            $content_type = $real_content_type;
+        }
+        // ok, it's kosher, rewrite what we need
+        $uri->userinfo = null;
+        $uri->host = null;
+        $uri->port = null;
+        $uri->fragment = null;
+        $uri->query = null;
+        $uri->path = "$content_type;base64," . base64_encode($raw_data);
+        return true;
+    }
+
+    public function muteErrorHandler($errno, $errstr) {}
+
+}
+

smoketests/dataScheme.php

@@ -0,0 +1,37 @@
+<?php
+
+require_once 'common.php';
+
+echo '<?xml version="1.0" encoding="UTF-8" ?>';
+?><!DOCTYPE html
+     PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
+     "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
+<html xmlns="http://www.w3.org/1999/xhtml">
+<head>
+    <title>HTML Purifier data Scheme Smoketest</title>
+    <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
+</head>
+<body>
+<h1>HTML Purifier data Scheme Smoketest</h1>
+<?php
+
+$string = '<img src="data:image/png;base64,
+iVBORw0KGgoAAAANSUhEUgAAAAoAAAAKCAYAAACNMs+9AAAABGdBTUEAALGP
+C/xhBQAAAAlwSFlzAAALEwAACxMBAJqcGAAAAAd0SU1FB9YGARc5KB0XV+IA
+AAAddEVYdENvbW1lbnQAQ3JlYXRlZCB3aXRoIFRoZSBHSU1Q72QlbgAAAF1J
+REFUGNO9zL0NglAAxPEfdLTs4BZM4DIO4C7OwQg2JoQ9LE1exdlYvBBeZ7jq
+ch9//q1uH4TLzw4d6+ErXMMcXuHWxId3KOETnnXXV6MJpcq2MLaI97CER3N0
+vr4MkhoXe0rZigAAAABJRU5ErkJggg==" alt="Red dot" />';
+
+$purifier = new HTMLPurifier(array('URI.AllowedSchemes' => 'data'));
+
+?>
+<div><?php
+echo $purifier->purify($string);
+?></div>
+
+</body>
+</html>
+<?php
+
+// vim: et sw=4 sts=4

tests/HTMLPurifier/URISchemeTest.php

@@ -6,8 +6,21 @@
 class HTMLPurifier_URISchemeTest extends HTMLPurifier_URIHarness
 {
 
+    private $pngBase64;
+
+    public function __construct() {
+        $this->pngBase64 =
+            'iVBORw0KGgoAAAANSUhEUgAAAAoAAAAKCAYAAACNMs+9AAAABGdBTUEAALGP'.
+            'C/xhBQAAAAlwSFlzAAALEwAACxMBAJqcGAAAAAd0SU1FB9YGARc5KB0XV+IA'.
+            'AAAddEVYdENvbW1lbnQAQ3JlYXRlZCB3aXRoIFRoZSBHSU1Q72QlbgAAAF1J'.
+            'REFUGNO9zL0NglAAxPEfdLTs4BZM4DIO4C7OwQg2JoQ9LE1exdlYvBBeZ7jq'.
+            'ch9//q1uH4TLzw4d6+ErXMMcXuHWxId3KOETnnXXV6MJpcq2MLaI97CER3N0'.
+            'vr4MkhoXe0rZigAAAABJRU5ErkJggg==';
+    }
+
     protected function assertValidation($uri, $expect_uri = true) {
         $this->prepareURI($uri, $expect_uri);
+        $this->config->set('URI.AllowedSchemes', array($uri->scheme));
         // convenience hack: the scheme should be explicitly specified
         $scheme = $uri->getSchemeObj($this->config, $this->context);
         $result = $scheme->validate($uri, $this->config, $this->context);
@@ -132,6 +145,26 @@ class HTMLPurifier_URISchemeTest extends HTMLPurifier_URIHarness
         );
     }
 
+    function test_data_png() {
+        $this->assertValidation(
+            'data:image/png;base64,'.$this->pngBase64
+        );
+    }
+
+    function test_data_malformed() {
+        $this->assertValidation(
+            'data:image/png;base64,vr4MkhoXJRU5ErkJggg==',
+            false
+        );
+    }
+
+    function test_data_implicit() {
+        $this->assertValidation(
+            'data:base64,'.$this->pngBase64,
+            'data:image/png;base64,'.$this->pngBase64
+        );
+    }
+
 }
 
 // vim: et sw=4 sts=4