Incomplete Identification of Uploaded File Variables (PHP)

Opis

The PHP application uses an old method for processing uploaded files by referencing the four global variables that are set for each file (e.g. $varname, $varname_size, $varname_name, $varname_type). These variables could be overwritten by attackers, causing the application to process unauthorized files.

These global variables could be overwritten by POST requests, cookies, or other methods of populating or overwriting these variables. This could be used to read or process arbitrary files by providing values such as "/etc/passwd".

Skutki

• Confidentiality, Integrity

  Read Files or Directories; Modify Files or Directories

Zapobieganie

• Architecture and Design

  Use PHP 4 or later.

• Architecture and Design

  If you must support older PHP versions, write your own version of is_uploaded_file() and run it against $HTTP_POST_FILES['userfile']))

• Implementation

  For later PHP versions, reference uploaded files using the $HTTP_POST_FILES or $_FILES variables, and use is_uploaded_file() or move_uploaded_file() to ensure that you are dealing with an uploaded file.

Przykłady podatności

• CVE-2002-1460 Forum does not properly verify whether a file was uploaded or if the associated variables were set by POST, allowing remote attackers to read arbitrary files.
• CVE-2002-1759 Product doesn't check if the variables for an upload were set by uploading the file, or other methods such as $_POST.
• CVE-2002-1710 Product does not distinguish uploaded file from other files.

Słabość nadrzędna

• CWE-345 Insufficient Verification of Data Authenticity

Pokrewna

• CWE-473 PHP External Variable Modification

Kiedy powstaje

• Implementation

Dotyczy

PHP

Źródła

1. A Study in Scarlet - section 5, "File Upload" — Shaun Clowes