DVWA下的爆破（高难度） – 作者:fu福lin林-安全小百科

1、提交登录请求，抓包

2、发给Intruder模块进行处理

3、填好攻击payload，进行爆破攻击

爆破失败，状态码全是302，长度都一致，说明之前单纯的思路已经不能解决问题了。仔细观察，可以发现多了一个字段，就是user_token。

user_token主要有两个作用：①：防止表单重复提交 ②：用来作身份验证，每次的请求中的user_token都不一样，会发生变化。强行解释一波就是因为有uesr_token的限制，故每次爆破就不只是那用户名和密码进行枚举就行了，一旦你的身份没有通过验证，就算给你正确的密码一样也会登录失败。

4、返回Intruder模块，选择新的攻击模式

攻击模式换成pitchfork，并且将user_token的值加上$标签

5、Payload1和payload2可以不动，将payload3的模式修改成“Recursive grep”即可

6、在Options里，找到Grep-Extract，添加user_token

还要记住此user_token的值：90c9a29a5f9d6e449e902914acae3ab9

7、回到payloads下，给payload3添加初始值

8、开始爆破，找长度特殊的，得到用户名和密码，然后手工登录验证

9、总结一下

前面低和中难度的，都比较容易，高难度的就不行了，具体原因还得看源代码

<?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 “Welcome to the password protected area {$user}”;
echo “<img src=\”{$avatar}\” />”;
}
else {
// Login failed
sleep( rand( 0, 3 ) );
echo “<pre> Username and/or password incorrect.</pre>”;
}

((is_null($___mysqli_res = mysqli_close($GLOBALS[“___mysqli_ston”]))) ? false : $___mysqli_res);
}

// Generate Anti-CSRF token
generateSessionToken();

?>

High级别的代码使用了Anti-CSRF token来抵御CSRF的攻击，使用了stripslashes函数和mysqli_real_esacpe_string来抵御SQL注入和XSS的攻击。

由于使用了Anti-CSRF token，每次服务器返回的登陆页面中都会包含一个随机的user_token的值，用户每次登录时都要将user_token一起提交。服务器收到请求后，会优先做token的检查，就算用户名密码正确，一样会登录失败。

最后来看看impossible级别的源代码

<?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> 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) . " "; print "The timenow is: " . date ("h:i:s", $timenow) . " "; print "The timeout is: " . date ("h:i:s", $timeout) . " "; */ // 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 "; } } // 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 "<img src=\"{$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 ); $data->execute(); } else { // Login failed sleep( rand( 2, 4 ) ); // Give the user some feedback echo "<pre> Username and/or password incorrect. Alternative, the account has been locked because of too many failed logins. If this is the case, please try again in {$lockout_time} minutes.</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(); ?>