DWVA-关于登陆页面绕过的漏洞详解<Brute Force>

本文是关于漏洞靶场DWVA第一个模块Brute Force的详细解答

LOW等级

 

此为最低等级low等级下的登录页面，先查看下源代码

 1  <?php
 2 
 3 if( isset( $_GET[ 'Login' ] ) ) {
 4     // Get username
 5     $user = $_GET[ 'username' ];
 6 
 7     // Get password
 8     $pass = $_GET[ 'password' ];
 9     $pass = md5( $pass );
10 
11     // Check the database
12     $query  = "SELECT * FROM `users` WHERE user = '$user' AND password = '$pass';";
13     $result = mysqli_query($GLOBALS["___mysqli_ston"],  $query ) or die( '<pre>' . ((is_object($GLOBALS["___mysqli_ston"])) ? mysqli_error($GLOBALS["___mysqli_ston"]) : (($___mysqli_res = mysqli_connect_error()) ? $___mysqli_res : false)) . '</pre>' );
14 
15     if( $result && mysqli_num_rows( $result ) == 1 ) {
16         // Get users details
17         $row    = mysqli_fetch_assoc( $result );
18         $avatar = $row["avatar"];
19 
20         // Login successful
21         echo "<p>Welcome to the password protected area {$user}</p>";
22         echo "<img src=\"{$avatar}\" />";
23     }
24     else {
25         // Login failed
26         echo "<pre><br />Username and/or password incorrect.</pre>";
27     }
28 
29     ((is_null($___mysqli_res = mysqli_close($GLOBALS["___mysqli_ston"]))) ? false : $___mysqli_res);
30 }
31 
32 ?>

查看代码可以发现，此代码中将我们输入的用户名直接带入到sql语句中进行查询，

查询成功将显示  Welcome to the password protected area  和一个图片

查询失败将显示  Username and/or password incorrect.

由于在代码中并未对用户输入进行过滤，因此可以实现绕过。

绕过方法---  用户名‘ #

解读：输入正确的用户名并添加符号’来实现闭合，并用#将后面的字符注释掉，以防止出现闭合问题。

实现方法如图

成功登入效果图：

medium等级

 1  <?php
 2 
 3 if( isset( $_GET[ 'Login' ] ) ) {
 4     // Sanitise username input
 5     $user = $_GET[ 'username' ];
 6     $user = ((isset($GLOBALS["___mysqli_ston"]) && is_object($GLOBALS["___mysqli_ston"])) ? mysqli_real_escape_string($GLOBALS["___mysqli_ston"],  $user ) : ((trigger_error("[MySQLConverterToo] Fix the mysql_escape_string() call! This code does not work.", E_USER_ERROR)) ? "" : ""));
 7 
 8     // Sanitise password input
 9     $pass = $_GET[ 'password' ];
10     $pass = ((isset($GLOBALS["___mysqli_ston"]) && is_object($GLOBALS["___mysqli_ston"])) ? mysqli_real_escape_string($GLOBALS["___mysqli_ston"],  $pass ) : ((trigger_error("[MySQLConverterToo] Fix the mysql_escape_string() call! This code does not work.", E_USER_ERROR)) ? "" : ""));
11     $pass = md5( $pass );
12 
13     // Check the database
14     $query  = "SELECT * FROM `users` WHERE user = '$user' AND password = '$pass';";
15     $result = mysqli_query($GLOBALS["___mysqli_ston"],  $query ) or die( '<pre>' . ((is_object($GLOBALS["___mysqli_ston"])) ? mysqli_error($GLOBALS["___mysqli_ston"]) : (($___mysqli_res = mysqli_connect_error()) ? $___mysqli_res : false)) . '</pre>' );
16 
17     if( $result && mysqli_num_rows( $result ) == 1 ) {
18         // Get users details
19         $row    = mysqli_fetch_assoc( $result );
20         $avatar = $row["avatar"];
21 
22         // Login successful
23         echo "<p>Welcome to the password protected area {$user}</p>";
24         echo "<img src=\"{$avatar}\" />";
25     }
26     else {
27         // Login failed
28         sleep( 2 );
29         echo "<pre><br />Username and/or password incorrect.</pre>";
30     }
31 
32     ((is_null($___mysqli_res = mysqli_close($GLOBALS["___mysqli_ston"]))) ? false : $___mysqli_res);
33 }
34 
35 ?>

Medium级别的代码主要增加了mysql_real_escape_string函数，这个函数会对字符串中的特殊符号（x00，n，r，，’，”，x1a）进行转义

可以用burpsuit抓包进行暴力破解。