Merge pull request #10493 from annando/api

[friendica.git] / src / Content / Text / HTML.php

diff --git a/src/Content/Text/HTML.php b/src/Content/Text/HTML.php
index 975be8b1ffadadcb0d64d8785c01daf41e92da26..51515137e56ddd00f3d576e93f4998b7652bf025 100644 (file)
--- a/src/Content/Text/HTML.php
+++ b/src/Content/Text/HTML.php
@@ -1,6 +1,6 @@
 <?php
 /**
- * @copyright Copyright (C) 2020, Friendica
+ * @copyright Copyright (C) 2010-2021, the Friendica project
  *
  * @license GNU AGPL version 3 or any later version
  *
@@ -605,6 +605,10 @@ class HTML
                // Collecting all links
                $urls = self::collectURLs($message);
 
+               if (empty($message)) {
+                       return '';
+               }
+
                @$doc->loadHTML($message, LIBXML_HTML_NODEFDTD);
 
                self::tagToBBCode($doc, 'html', [], '', '');
@@ -961,4 +965,69 @@ class HTML
        {
                return str_replace('&amp;', '&', $s);
        }
+
+       /**
+        * Clean an HTML text for potentially harmful code
+        *
+        * @param string $text
+        * @param array  $allowedIframeDomains List of allowed iframe source domains without the scheme
+        * @return string
+        */
+       public static function purify(string $text, array $allowedIframeDomains = []): string
+       {
+               // Allows cid: URL scheme
+               \HTMLPurifier_URISchemeRegistry::instance()->register('cid', new HTMLPurifier_URIScheme_cid());
+
+               $config = \HTMLPurifier_HTML5Config::createDefault();
+               $config->set('HTML.Doctype', 'HTML5');
+
+               // Used to remove iframe with src attribute filtered out
+               $config->set('AutoFormat.RemoveEmpty', true);
+
+               $config->set('HTML.SafeIframe', true);
+
+               array_walk($allowedIframeDomains, function (&$domain) {
+                       // Allow the domain and all its eventual sub-domains
+                       $domain = '(?:(?!-)[A-Za-z0-9-]{1,63}(?<!-)\.)*' . preg_quote(trim($domain, '/'), '%');
+               });
+
+               $config->set('URI.SafeIframeRegexp',
+                       '%^https://(?:
+                               ' . implode('|', $allowedIframeDomains) . '
+                       )
+                       (?:/|$) # Prevents bogus domains like youtube.com.fake.tld
+                       %xi'
+               );
+
+               $config->set('Attr.AllowedRel', [
+                       'noreferrer' => true,
+                       'noopener' => true,
+               ]);
+               $config->set('Attr.AllowedFrameTargets', [
+                       '_blank' => true,
+               ]);
+
+               $config->set('AutoFormat.RemoveEmpty.Predicate', [
+                       'colgroup' => [],        // |
+                       'th'       => [],        // |
+                       'td'       => [],        // |
+                       'iframe'   => ['src'],   // ↳ Default HTMLPurify values
+                       'i'        => ['class'], // Allows forkawesome icons
+               ]);
+
+               // Uncomment to debug HTMLPurifier behavior
+               //$config->set('Core.CollectErrors', true);
+               //$config->set('Core.MaintainLineNumbers', true);
+
+               $HTMLPurifier = new \HTMLPurifier($config);
+
+               $text = $HTMLPurifier->purify($text);
+
+               /** @var \HTMLPurifier_ErrorCollector $errorCollector */
+               // Uncomment to debug HTML Purifier behavior
+               //$errorCollector = $HTMLPurifier->context->get('ErrorCollector');
+               //var_dump($errorCollector->getRaw());
+
+               return $text;
+       }
 }