Leeyuxun の note

BUPT | SCSS

DVWA Brute Force

发表于 更新于 分类于

前言

暴力破解是利用大量的用户名和字典，去对账号进行暴力破解，弱密码可能是永远都无法防御的点；

DVWA 没模拟验证码缺陷的相关漏洞，在实战中，会遇到很多验证码无效的案例；

LOW

分析

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

分析：

isset()函数在php中用来检测变量是否设置(该函数返回的是布尔类型的值，即true/false)
服务器只是验证了参数Login是否被设置，没有任何的防爆破机制，且对参数username、password没有做任何过滤，存在明显的SQL注入漏洞。

方法一：万能密码（SQL注入）

1
2
3
admin'or '1'='1
admin' -- -
admin' #

方法二：暴力破解

使用BurpSuite载入字典爆破即可；

MEDIUM

分析

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

分析：

对传过来的值，使用了 mysql_real_escape_string() 函数，转义了以下字符：\x00、\n、\r、\、’、”、\x1a

使用 sleep(2) 函数，如果密码错误，则延时两秒响应。

攻击：

SQL注入失效

可以直接进行爆破，只不过速度慢了；

HIGH

分析

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
 <?php
    if( isset( $_GET[ 'Login' ] ) ) {
        // Check Anti-CSRF token
        checkToken( $_REQUEST[ 'user_token' ], $_SESSION[ 'session_token' ], 'index.php' );
        // Sanitise username input
        $user = $_GET[ 'username' ];
        $user = stripslashes( $user );
        $user = ((isset($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)) ? "" : ""));
        // Sanitise password input
        $pass = $_GET[ 'password' ];
        $pass = stripslashes( $pass );
        $pass = ((isset($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)) ? "" : ""));
        $pass = md5( $pass );
        // Check database
        $query  = "SELECT * FROM `users` WHERE user = '$user' AND password = '$pass';";
        $result = mysqli_query($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>' );
        if( $result && mysqli_num_rows( $result ) == 1 ) {
            // Get users details
            $row    = mysqli_fetch_assoc( $result );
            $avatar = $row["avatar"];
            // Login successful
            echo "<p>Welcome to the password protected area {$user}</p>";
            echo "<img src=\"{$avatar}\" />";
        }
        else {
            // Login failed
            sleep( rand( 0, 3 ) );
            echo "<pre><br />Username and/or password incorrect.</pre>";
        }
        ((is_null($___mysqli_res = mysqli_close($GLOBALS["___mysqli_ston"]))) ? false : $___mysqli_res);
    }
    // Generate Anti-CSRF token
    generateSessionToken();
?>

分析：

增加了Ant-CSRF token，抵御CSRF攻击，同时也增加了爆破的难度。不过仍然可以使用BurpSuite进行破解，只需添加一个宏链接到上一个返回到token值即可；（参考：https://www.cnblogs.com/v1vvwv/p/DVWA-Brute-Force.html）

IMPOSSIBLE

分析

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
<?php
    if( isset( $_POST[ 'Login' ] ) && isset ($_POST['username']) && isset ($_POST['password']) ) {
        // Check Anti-CSRF token
        checkToken( $_REQUEST[ 'user_token' ], $_SESSION[ 'session_token' ], 'index.php' );
        // Sanitise username input
        $user = $_POST[ 'username' ];
        $user = stripslashes( $user );
        $user = ((isset($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)) ? "" : ""));
        // Sanitise password input
        $pass = $_POST[ 'password' ];
        $pass = stripslashes( $pass );
        $pass = ((isset($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)) ? "" : ""));
        $pass = md5( $pass );
        // Default values
        $total_failed_login = 3;
        $lockout_time       = 15;
        $account_locked     = false;
        // Check the database (Check user information)
        $data = $db->prepare( 'SELECT failed_login, last_login FROM users WHERE user = (:user) LIMIT 1;' );
        $data->bindParam( ':user', $user, PDO::PARAM_STR );
        $data->execute();
        $row = $data->fetch();
        // Check to see if the user has been locked out.
        if( ( $data->rowCount() == 1 ) && ( $row[ 'failed_login' ] >= $total_failed_login ) )  {
            // User locked out.  Note, using this method would allow for user enumeration!
            //echo "<pre><br />This account has been locked due to too many incorrect logins.</pre>";
            // Calculate when the user would be allowed to login again
            $last_login = strtotime( $row[ 'last_login' ] );
            $timeout    = $last_login + ($lockout_time * 60);
            $timenow    = time();
            /*
            print "The last login was: " . date ("h:i:s", $last_login) . "<br />";
            print "The timenow is: " . date ("h:i:s", $timenow) . "<br />";
            print "The timeout is: " . date ("h:i:s", $timeout) . "<br />";
            */
            // Check to see if enough time has passed, if it hasn't locked the account
            if( $timenow < $timeout ) {
                $account_locked = true;
                // print "The account is locked<br />";
            }
        }
        // Check the database (if username matches the password)
        $data = $db->prepare( 'SELECT * FROM users WHERE user = (:user) AND password = (:password) LIMIT 1;' );
        $data->bindParam( ':user', $user, PDO::PARAM_STR);
        $data->bindParam( ':password', $pass, PDO::PARAM_STR );
        $data->execute();
        $row = $data->fetch();
        // If its a valid login...
        if( ( $data->rowCount() == 1 ) && ( $account_locked == false ) ) {
            // Get users details
            $avatar       = $row[ 'avatar' ];
            $failed_login = $row[ 'failed_login' ];
            $last_login   = $row[ 'last_login' ];
            // Login successful
            echo "<p>Welcome to the password protected area <em>{$user}</em></p>";
            echo "<img src=\"{$avatar}\" />";
            // Had the account been locked out since last login?
            if( $failed_login >= $total_failed_login ) {
                echo "<p><em>Warning</em>: Someone might of been brute forcing your account.</p>";
                echo "<p>Number of login attempts: <em>{$failed_login}</em>.<br />Last login attempt was at: <em>${last_login}</em>.</p>";
            }
            // Reset bad login count
            $data = $db->prepare( 'UPDATE users SET failed_login = "0" WHERE user = (:user) LIMIT 1;' );
            $data->bindParam( ':user', $user, PDO::PARAM_STR );
            $data->execute();
        } else {
            // Login failed
            sleep( rand( 2, 4 ) );
            // Give the user some feedback
            echo "<pre><br />Username and/or password incorrect.<br /><br/>Alternative, the account has been locked because of too many failed logins.<br />If this is the case, <em>please try again in {$lockout_time} minutes</em>.</pre>";
            // Update bad login count
            $data = $db->prepare( 'UPDATE users SET failed_login = (failed_login + 1) WHERE user = (:user) LIMIT 1;' );
            $data->bindParam( ':user', $user, PDO::PARAM_STR );
            $data->execute();
        }
        // Set the last login time
        $data = $db->prepare( 'UPDATE users SET last_login = now() WHERE user = (:user) LIMIT 1;' );
        $data->bindParam( ':user', $user, PDO::PARAM_STR );
        $data->execute();
    }
    // Generate Anti-CSRF token
    generateSessionToken();
?>

分析：

设置错误 3 次，锁定 15 分钟；

如果在实战中遇到这种情况，可以采用爆破用户名；