DVWA是一个适合新手锻炼的靶机,是由PHP/MySQL组成的 Web应用程序,帮助大家了解web应用的攻击手段
DVWA大致能分成以下几个模块,包含了OWASP Top 10大主流漏洞环境。
Brute Force------暴力破解
Command Injection------命令注入
CSRF------跨站请求伪造
File Inclusion------文件包含
File Upload------文件上传漏洞
Insecure CAPTCHA------不安全的验证
SQL Injection------sql注入
SQL Injection(Blind)------sql注入(盲注)
Weak Session IDs------不安全的SessionID
XSS(DOM)------DOM型XSS
XSS(Reflected)------反射型XSS
XSS(Stored)------存储型XSS
CSP Bypass ------绕过内容安全策略
JavaScript------JS攻击
本文所用dvwa版本为2.3
GitHub - digininja/DVWA: Damn Vulnerable Web Application (DVWA)
可以自行通过phpstudy搭建以供练习
DVWA Security分为四个等级,low,medium,high,impossible,不同的安全等级对应了不同的漏洞等级。
1.low-最低安全等级,无任何安全措施,通过简单毫无安全性的编码展示了安全漏洞。
2.medium-中等安全等级,有安全措施的保护,但是安全性并不强。
3.high-高等安全等级,有安全措施保护,是中等安全等级的加深,这个等级下的安全漏洞可能不允许相同程度的攻击。
4.impossible-最高(不可能)安全等级,存在相当强的安全保护措施,这个级别应能防止所有的漏洞,主要用于比较不同等级下的源代码。
开此篇文章的主要目的是为了对代码进行分析,查看其应对攻击的方法及绕过手法
进入暴力破解的界面,有点基础的都知道,在bp中通过字典,导入用户名和密码进行爆破,这样的操作大家见多了,再写没啥意思,想看的可以去pikachu靶场的暴力破解去了解具体操作,本文主要结合代码进行分析
low等级
php
<?php
if( isset( $_GET[ 'Login' ] ) ) {
// Get username
$user = $_GET[ 'username' ]; //通过get方式获取username
// Get password
$pass = $_GET[ 'password' ]; //通过get方式获取password
$pass = md5( $pass ); //收到密码后进行md5加密
// Check the database
$query = "SELECT * FROM `users` WHERE user = '$user' AND password = '$pass';";
//直接对数据库进行操作,用户名存在万能密码漏洞
$result = mysqli_query($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>' );
//直接将结果输出到界面
if( $result && mysqli_num_rows( $result ) == 1 ) {
//mysqli_num_rows()函数是一个用于获取查询结果中行数的mysqli扩展函数。它接受一个查询结果对象作为参数,并返回该结果集中的行数。通常用于检查查询结果是否包含了符合条件的记录,以便在代码中进行相应的处理。
// 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);
}
?>
以上是一个简单的PHP登录验证功能。当用户提交登录表单时,通过GET方法获取用户名和密码,然后将密码进行MD5加密。接着查询数据库,检查用户名和加密后的密码是否匹配数据库中的记录。如果匹配成功,则显示用户的欢迎信息和头像;如果匹配失败,则显示错误信息。
无任何防护,直接进行暴力破解即可
medium等级
php
<?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);
}
?>
相比于low的代码,这里获取到username和password后,有一段转义的代码
php
$user = ((isset($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)) ? "" : ""));
这行代码是对用户输入的用户名进行转义处理,以防止SQL注入攻击。具体来说,它使用了mysqli_real_escape_string()函数对用户输入的用户名进行转义,确保特殊字符在SQL语句中不会被误解为SQL语句的一部分,从而保护数据库安全。
加了这个转义只是对sql注入进行防范,对暴力破解还是没有起到效果
high等级
php
<?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
$html .= "<p>Welcome to the password protected area {$user}</p>";
$html .= "<img src=\"{$avatar}\" />";
}
else {
// Login failed
sleep( rand( 0, 3 ) );
$html .= "<pre><br />Username and/or password incorrect.</pre>";
}
((is_null($___mysqli_res = mysqli_close($GLOBALS["___mysqli_ston"]))) ? false : $___mysqli_res);
}
// Generate Anti-CSRF token
generateSessionToken();
?>
这一等级开始,登录设置了token
选中这个checktoken函数,跳转到这个函数
php
// Token functions --
function checkToken( $user_token, $session_token, $returnURL ) { # Validate the given (CSRF) token
global $_DVWA;
if (in_array("disable_authentication", $_DVWA) && $_DVWA['disable_authentication']) {
return true;
}
if( $user_token !== $session_token || !isset( $session_token ) ) {
dvwaMessagePush( 'CSRF token is incorrect' );
dvwaRedirect( $returnURL );
}
}
跟进到checkToken方法,设置了三个参数,如果user_token不等于session_token或者session_token为空,调用dvwaRedirect方法。
php
function dvwaRedirect( $pLocation ) {
session_commit();
header( "Location: {$pLocation}" );
exit;
}
这段代码定义了一个名为dvwaRedirect()
的函数,用于实现页面重定向的功能。函数接受一个参数$pLocation
,即要重定向到的目标位置。
在函数内部,首先调用session_commit()
函数来提交并保存当前会话的所有数据。然后通过header()
函数设置HTTP响应头,将浏览器重定向到指定的目标位置。最后使用exit
函数来终止脚本的执行,确保页面重定向的立即生效。
这个函数通常用于在应用程序中需要进行页面跳转的情况,如登录成功后跳转到用户首页,或者在某些条件下需要跳转到其他页面。通过调用这个函数,可以实现简单的页面重定向功能。
可以看到这个提交界面多了一串user_token,并且每次刷新都重新生成,pikachu靶场的那篇文章有演示在前端发现token怎么进行爆破操作
从medium等级开始,登录失败就会延时,提高了暴力破解的成本
impossiable等级
php
<?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();
?>
这是最高难度的代码,它主要采取了以下几种措施来防止暴力破解
POST方式获取用户名密码
设置token
对sql语句进行转义
PDO预编译
设置登录次数,超过次数进行锁定
登录失败后延时
一般来说,这种情况进行爆破是不可能的了,或者说成本过高