[DBAL-111] MySQL Driver possibly subject to sql injections with PDO::quote()

Sat, 14 May 2011 07:24:48 +0000

Prior to 5.3.6, the MySQL PDO driver ignored the character set parameter to options. Due to MySQL's C api (and MySQLND), this is required for the proper function of mysql_real_escape_string() (the C API call). Since PDO uses the mres() C call for PDO::quote(), this means that the quoted string does not take into account the connection character set.

Starting with 5.3.6, that was fixed. So now if you pass the proper character set to PDO via driver options, sql injection is impossible while using the PDO::quote() api call.

PDO proof of concept

$dsn = 'mysql:dbname=INFORMATION_SCHEMA;host=127.0.0.1;charset=GBK;';
$pdo = new PDO($dsn, $user, $pass);
$pdo->exec('SET NAMES GBK');
$string = chr(0xbf) . chr(0x27) . ' OR 1 = 1; /*';
$sql = "SELECT TABLE_NAME
            FROM INFORMATION_SCHEMA.TABLES
            WHERE TABLE_NAME LIKE ".$pdo->quote($string)." LIMIT 1;";
$stmt = $pdo->query($sql);
var_dump($stmt->rowCount());

Expected Result: `int(0)`.
Actual Result: `int(1)`.

There are 2 issues to fix. First, the documentation does not indicate that you can pass the `charset` option to the MySQL Driver. This should be fixed so that users are given the proper option to set character sets.

Secondly, `Connection::setCharset()` should be modified for MySQL to throw an exception, since the character set is only safely setable using the DSN with PDO. This is a limitation of the driver and could be asked as a feature request for the PHP core. Either that, or a big warning should be put on the documentation of the API to indicate the unsafe character set change

Doctrine Project

[DBAL-111] MySQL Driver possibly subject to sql injections with PDO::quote()