Fix path traversal/injection security bug. Thanks to Steven Frank at panic.com for...

diff --git a/gemini.class.php b/gemini.class.php
index 576d9aaf39b3fbf0e6dc6c8e3cafdb6d2ec6aacc..a27823b2130f0fa6344982499650e7579a2a091f 100644 (file)
--- a/gemini.class.php
+++ b/gemini.class.php
@@ -91,7 +91,8 @@ class Gemini {
 
                // Kristall Browser is adding "__" to the end of the filenames
                // wtf am I missing?
-               $url['path'] = str_replace("__", "", $url['path']);
+               // also removing ".." to mitigate against directory traversal
+               $url['path'] = str_replace(array("..", "__"), "", $url['path']);
                // force an index file to be appended if a filename is missing
                if(empty($url['path'])) {
                        $url['path'] = "/".$this->default_index_file;
@@ -99,7 +100,13 @@ class Gemini {
                        $url['path'] .= $this->default_index_file;
                }
 
-               return $this->data_dir.$hostname.$url['path'];
+               $valid_data_dir = dirname(__FILE__)."/".$this->data_dir;
+               $return_path = $this->data_dir.$hostname.$url['path'];
+               // check the real path is in the data_dir (path traversal sanity check)
+               if(substr(realpath($return_path),0, strlen($valid_data_dir)) == $valid_data_dir) {
+                       return $return_path;
+               }
+               return false;
        }
 
        function log_to_file($ip, $status_code, $meta, $filepath, $filesize) {