dvwa-Brute Force

brute force指暴力破解，列举出所有可能，并一一进行尝试

爆破用户名和密码，利用了burpsuit的抓包和爆破

burpsuite里intruder的四种攻击模式：https://howiezhao.github.io/2018/05/01/burpsuite-intruder-attack-type/

具体分析：

1、LOW

查看源码如下：

<?php

if( isset( $_GET['Login'] ) ) {

    $user = $_GET['username'];
    
    $pass = $_GET['password'];
    $pass = md5($pass);

    $qry = "SELECT * FROM `users` WHERE user='$user' AND password='$pass';";
    $result = mysql_query( $qry ) or die( '<pre>' . mysql_error() . '</pre>' );

    if( $result && mysql_num_rows( $result ) == 1 ) {
        // Get users details
        $i=0; // Bug fix.
        $avatar = mysql_result( $result, $i, "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>";
    }

    mysql_close();
} 

直接用burpsuite的intruder即可

2、medium

Brute Force Source
<?php

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 );

    $qry = "SELECT * FROM `users` WHERE user='$user' AND password='$pass';";
    $result = mysql_query( $qry ) or die( '<pre>' . mysql_error() . '</pre>' );

    if( $result && mysql_num_rows($result) == 1 ) {
        // Get users details
        $i=0; // Bug fix.
        $avatar = mysql_result( $result, $i, "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>";
    }

    mysql_close();
}

?>

相比low级别，添加了mysqli_real_escape_string函数，对一些特殊字符，例如\,'等，可以防止sql注入和xss注入，关于mysqli_real_escape_string函数：https://www.yuque.com/docs/share/eaca5dfb-cf45-481c-8ff0-6dbbff465125

3、high

 <?php

if( isset( $_GET[ 'Login' ] ) ) {

    // 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 );

    $qry = "SELECT * FROM `users` WHERE user='$user' AND password='$pass';";
    $result = mysql_query($qry) or die('<pre>' . mysql_error() . '</pre>' );

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

        // Login Successful
        echo "<p>Welcome to the password protected area " . $user . "</p>";
        echo '<img src="' . $avatar . '" />';
    } else {
        // Login failed
        sleep(3);
        echo "<pre><br>Username and/or password incorrect.</pre>";
        }

    mysql_close();
}

?> 

相比medium级别添加了stripslashes函数，删除字符串中的反斜杠，可以防止sql注入，而且若失败会等待3秒才可继续下一次，爆破处理时间会更长

4、impossible

其实我的没有，是一篇博客里的

<?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();
?> 

1、generateSessionToken();

每次服务器返回的登陆页面都会包含一个随机生成的session，当服务器收到请求，会优先检测token，所以此处不应该使用burpsuite（没有对session进行相应的改变），可使用python写个脚本进行爆破

该函数最主要的作用是Anti-CSRF token来抵御CSRF的攻击

2、对登录次数进行了限制

3、查询采用PDO(PHP Data Object)防御sql注入

参考链接：

https://blog.csdn.net/qq_36119192/article/details/82938424