Mitigate various SSTI injections

Author: rhukster

CHANGELOG.md

@@ -6,7 +6,8 @@
 1. [](#bugfix)
    * Fixed some multibyte issues in Inflector class [#732](https://github.com/getgrav/grav/issues/732)
    * Fallback to page modified date if Page date provided is invalid and can't be parsed [getgrav/grav-plugin-admin#2394](https://github.com/getgrav/grav-plugin-admin/issues/2394)
-   * Fixed a path traversal vulnerability with file uploads [GHSA-m7hx-hw6h-mqmc](https://github.com/getgrav/grav/security/advisories/GHSA-m7hx-hw6h-mqmc)
+   * Fixed a path traversal vulnerability with file uploads [#GHSA-m7hx-hw6h-mqmc](https://github.com/getgrav/grav/security/advisories/GHSA-m7hx-hw6h-mqmc)
+   * Fixed a security issue with insecure Twig functions be processed [#GHSA-2m7x-c7px-hp58](https://github.com/getgrav/grav/security/advisories/GHSA-2m7x-c7px-hp58) [#GHSA-r6vw-8v8r-pmp4](https://github.com/getgrav/grav/security/advisories/GHSA-r6vw-8v8r-pmp4) [#GHSA-qfv4-q44r-g7rv](https://github.com/getgrav/grav/security/advisories/GHSA-qfv4-q44r-g7rv)
 
 # v1.7.44
 ## 01/05/2024

system/src/Grav/Common/Security.php

@@ -263,4 +263,23 @@ public static function getXssDefaults(): array
             'invalid_protocols' => array_map('trim', $config->get('security.xss_invalid_protocols')),
         ];
     }
+
+    public static function cleanDangerousTwig(string $string): string
+    {
+        if ($string === '') {
+            return $string;
+        }
+
+        $bad_twig = [
+            'twig_array_map',
+            'twig_array_filter',
+            'call_user_func',
+            'registerUndefinedFunctionCallback',
+            'undefined_functions',
+            'twig.getFunction',
+            'core.setEscaper',
+        ];
+        $string = preg_replace('/(({{\s*|{%\s*)[^}]*?(' . implode('|', $bad_twig) . ')[^}]*?(\s*}}|\s*%}))/i', '{# $1 #}', $string);
+        return $string;
+    }
 }

system/src/Grav/Common/Twig/Twig.php

@@ -16,6 +16,7 @@
 use Grav\Common\Language\LanguageCodes;
 use Grav\Common\Page\Interfaces\PageInterface;
 use Grav\Common\Page\Pages;
+use Grav\Common\Security;
 use Grav\Common\Twig\Exception\TwigException;
 use Grav\Common\Twig\Extension\FilesystemExtension;
 use Grav\Common\Twig\Extension\GravExtension;
@@ -319,6 +320,7 @@ public function setTemplate($name, $template)
     public function processPage(PageInterface $item, $content = null)
     {
         $content = $content ?? $item->content();
+        $content = Security::cleanDangerousTwig($content);
 
         // override the twig header vars for local resolution
         $this->grav->fireEvent('onTwigPageVariables', new Event(['page' => $item]));
@@ -392,6 +394,8 @@ public function processString($string, array $vars = [])
         $this->grav->fireEvent('onTwigStringVariables');
         $vars += $this->twig_vars;
 
+        $string = Security::cleanDangerousTwig($string);
+
         $name = '@Var:' . $string;
         $this->setTemplate($name, $string);
 
@@ -418,7 +422,7 @@ public function processSite($format = null, array $vars = [])
         try {
             $grav = $this->grav;
 
-            // set the page now its been processed
+            // set the page now it's been processed
             $grav->fireEvent('onTwigSiteVariables');
 
             /** @var Pages $pages */
@@ -427,13 +431,15 @@ public function processSite($format = null, array $vars = [])
             /** @var PageInterface $page */
             $page = $grav['page'];
 
+            $content = Security::cleanDangerousTwig($page->content());
+
             $twig_vars = $this->twig_vars;
             $twig_vars['theme'] = $grav['config']->get('theme');
             $twig_vars['pages'] = $pages->root();
             $twig_vars['page'] = $page;
             $twig_vars['header'] = $page->header();
             $twig_vars['media'] = $page->media();
-            $twig_vars['content'] = $page->content();
+            $twig_vars['content'] = $content;
 
             // determine if params are set, if so disable twig cache
             $params = $grav['uri']->params(null, true);
@@ -568,4 +574,5 @@ public function setAutoescape($state)
 
         $this->autoescape = (bool) $state;
     }
+
 }