CVE-2021-44665 (published 2022-02-24T21:15Z)

A Directory Traversal vulnerability exists in the Xerte Project Xerte through 3.10.3 when downloading a project file via download.php.

Severity: LOW
CVSS v2 base score: 3.5 (AV:N/AC:M/Au:S/C:P/I:N/A:N)
CVSS v3 base score: 6.5, MEDIUM (CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N)

Weakness information:
cwe_id: CWE-22
cwe_name: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')
description: The product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory.
extended_description: 
            Many file operations are intended to take place within a restricted directory. By using special elements such as ".." and "/" separators, attackers can escape outside of the restricted location to access files or directories that are elsewhere on the system. One of the most common special elements is the "../" sequence, which in most modern operating systems is interpreted as the parent directory of the current location. This is referred to as relative path traversal. Path traversal also covers the use of absolute pathnames such as "/usr/local/bin" to access unexpected files. This is referred to as absolute path traversal.
         
         

Fix information:
repo_url: https://github.com/thexerteproject/xerteonlinetoolkits
commit_details: repo_url: https://github.com/thexerteproject/xerteonlinetoolkits
author: Tom Reijnders
author_date: 2021-11-18 16:41:49+01:00
msg: Fix vulnarebility
repository: repo_url: https://github.com/thexerteproject/xerteonlinetoolkits
repo_name: thexerteproject/xerteonlinetoolkits
description: Xerte Online Toolkits
repo_language: JavaScript
owner: thexerteproject
file_changes: filename: getfile.php
change_type: ModificationType.MODIFY
diff: @@ -23,38 +23,45 @@ require $xerte_toolkits_site->php_library_path . "user_library.php";
 require $xerte_toolkits_site->php_library_path . "template_library.php";
 require $xerte_toolkits_site->php_library_path . "template_status.php";
 
-// be slightly paranoid over the path the user is requesting to download.
+// be VERY paranoid over the path the user is requesting to download.
+// Even if the file starts with a correct pattern (old implementation) the user could travers path
+// like 542-tom-Notingham/../database.php or like 542-tom-Notingham/../../../../etc/passwd
 $unsafe_file_path = $_GET['file'];
-if(!preg_match('/^([0-9]+)-([a-z0-9]+)-/', $unsafe_file_path, $matches)) {
-    die("path must start with a number, and then a username - e.g. 20-foobar-");
-}
+$full_unsafe_file_path = $xerte_toolkits_site->root_file_path . $xerte_toolkits_site->users_file_area_short . $unsafe_file_path;
+// This gets the canonical file name, so in case of 542-tom-Notingham/../../../../etc/passwd -> /etc/passwd
+$realpath = realpath($full_unsafe_file_path);
+// Check that is start with root_path/USER-FILES
+if ($realpath !== false && $realpath === $full_unsafe_file_path) {
+    if (!preg_match('/^([0-9]+)-([a-z0-9]+)-/', $unsafe_file_path, $matches)) {
+        die("path must start with a number, and then a username - e.g. 20-foobar-");
+    }
 
-$template_id = $matches[1];
-$username = $matches[2];
+    $template_id = $matches[1];
+    $username = $matches[2];
 
-$has_perms = is_user_admin() || has_rights_to_this_template($template_id,$_SESSION['toolkits_logon_id']);
+    $has_perms = is_user_admin() || has_rights_to_this_template($template_id, $_SESSION['toolkits_logon_id']);
 
-if($has_perms) { 
-    if(is_user_an_editor($template_id,$_SESSION['toolkits_logon_id'])){
-        if($username == $_SESSION['toolkits_logon_username']) { 
-            // they're logged in, and hopefully have access to the media contents.
-            $file = dirname(__FILE__) . '/USER-FILES/' . $unsafe_file_path;
-            if(!is_file($file)) { 
-                die("Fail: file not found on disk"); 
-            }
-            $filename = addslashes(basename($file));
+    if ($has_perms) {
+        if (is_user_an_editor($template_id, $_SESSION['toolkits_logon_id'])) {
+            if ($username == $_SESSION['toolkits_logon_username']) {
+                // they're logged in, and hopefully have access to the media contents.
+                $file = dirname(__FILE__) . '/USER-FILES/' . $unsafe_file_path;
+                if (!is_file($file)) {
+                    die("Fail: file not found on disk");
+                }
+                $filename = addslashes(basename($file));
 
-            header("Cache-Control: public");
-            header("Content-Length: " . filesize($file));
-            header("Content-Description: File Transfer");
-            header("Content-Type: application/force-download"); 
-            header("Content-Disposition: attachment; filename=\"$filename\"");
-            header("Content-Transfer-Encoding: binary");
-            flush();
-            readfile($file);
-            exit(0);
+                header("Cache-Control: public");
+                header("Content-Length: " . filesize($file));
+                header("Content-Description: File Transfer");
+                header("Content-Type: application/force-download");
+                header("Content-Disposition: attachment; filename=\"$filename\"");
+                header("Content-Transfer-Encoding: binary");
+                flush();
+                readfile($file);
+                exit(0);
+            }
         }
     }
 }
-
 echo "You do not appear to have permission to view this resource.";

programming_language: PHP