DVWA-CSRF

CSRF

Low

观察后端代码，只要password_new等于password_conf就可以修改密码。由于这两个参数是通过GET传递的，所以直接构造payload。

http://192.168.20.156/DVWA/vulnerabilities/csrf/?password_new=pass&password_conf=pass&Change=Change#

这种URL可能会被发现意图，所以我们可以将它转换为短链接。

Medium

观察后端代码，对数据包的HTTP_REFERER（对应http 包头的 Referer 参数的值，当前请求页面的 URL 的来源页面地址），SERVER_NAME（http 包头的 Host 参数，要访服务器主机名）。stripos 函数用于查找一个字符串在另一个字符串中首次出现的位置，不区分大小写。它返回匹配的位置索引，如果没有找到则返回 false。

<?phpif( isset( $_GET[ 'Change' ] ) ) {// Checks to see where the request came fromif( stripos( $_SERVER[ 'HTTP_REFERER' ] ,$_SERVER[ 'SERVER_NAME' ]) !== false ) {// Get input$pass_new  = $_GET[ 'password_new' ];$pass_conf = $_GET[ 'password_conf' ];// Do the passwords match?if( $pass_new == $pass_conf ) {// They do!$pass_new = ((isset($GLOBALS["___mysqli_ston"]) && is_object($GLOBALS["___mysqli_ston"])) ? mysqli_real_escape_string($GLOBALS["___mysqli_ston"],  $pass_new ) : ((trigger_error("[MySQLConverterToo] Fix the mysql_escape_string() call! This code does not work.", E_USER_ERROR)) ? "" : ""));$pass_new = md5( $pass_new );// Update the database$current_user = dvwaCurrentUser();$insert = "UPDATE `users` SET password = '$pass_new' WHERE user = '" . $current_user . "';";$result = mysqli_query($GLOBALS["___mysqli_ston"],  $insert ) or die( '<pre>' . ((is_object($GLOBALS["___mysqli_ston"])) ? mysqli_error($GLOBALS["___mysqli_ston"]) : (($___mysqli_res = mysqli_connect_error()) ? $___mysqli_res : false)) . '</pre>' );// Feedback for the user$html .= "<pre>Password Changed.</pre>";}else {// Issue with passwords matching$html .= "<pre>Passwords did not match.</pre>";}}else {// Didn't come from a trusted source$html .= "<pre>That request didn't look correct.</pre>";}((is_null($___mysqli_res = mysqli_close($GLOBALS["___mysqli_ston"]))) ? false : $___mysqli_res);
}?>

我们发现用Low level的方法的话，burp抓的数据包中没有Referer。根据刚才分析我们只要让Referer中包含host，也就是192.168.20.156即可。
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High

观察后端代码，加入了CSRF token防止csrf攻击。
1.这里讲解一下burp的一个插件CSRF Token Tracker，自动获取 csrf 的 token，对于一些有 csrf 限制的请求，它可以绕过该限制。

<?php$change = false;
$request_type = "html";
$return_message = "Request Failed";if ($_SERVER['REQUEST_METHOD'] == "POST" && array_key_exists ("CONTENT_TYPE", $_SERVER) && $_SERVER['CONTENT_TYPE'] == "application/json") {$data = json_decode(file_get_contents('php://input'), true);$request_type = "json";if (array_key_exists("HTTP_USER_TOKEN", $_SERVER) &&array_key_exists("password_new", $data) &&array_key_exists("password_conf", $data) &&array_key_exists("Change", $data)) {$token = $_SERVER['HTTP_USER_TOKEN'];$pass_new = $data["password_new"];$pass_conf = $data["password_conf"];$change = true;}
} else {if (array_key_exists("user_token", $_REQUEST) &&array_key_exists("password_new", $_REQUEST) &&array_key_exists("password_conf", $_REQUEST) &&array_key_exists("Change", $_REQUEST)) {$token = $_REQUEST["user_token"];$pass_new = $_REQUEST["password_new"];$pass_conf = $_REQUEST["password_conf"];$change = true;}
}if ($change) {// Check Anti-CSRF tokencheckToken( $token, $_SESSION[ 'session_token' ], 'index.php' );// Do the passwords match?if( $pass_new == $pass_conf ) {// They do!$pass_new = mysqli_real_escape_string ($GLOBALS["___mysqli_ston"], $pass_new);$pass_new = md5( $pass_new );// Update the database$current_user = dvwaCurrentUser();$insert = "UPDATE `users` SET password = '" . $pass_new . "' WHERE user = '" . $current_user . "';";$result = mysqli_query($GLOBALS["___mysqli_ston"],  $insert );// Feedback for the user$return_message = "Password Changed.";}else {// Issue with passwords matching$return_message = "Passwords did not match.";}mysqli_close($GLOBALS["___mysqli_ston"]);if ($request_type == "json") {generateSessionToken();header ("Content-Type: application/json");print json_encode (array("Message" =>$return_message));exit;} else {$html .= "<pre>" . $return_message . "</pre>";}
}// Generate Anti-CSRF token
generateSessionToken();?>

在Extensions的BApp Store中，搜素并下载CSRF Token Tracker。之后根据自己参数配置并勾选。
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进行抓包

可以发现CSRF Token Tracker模块已经获取到了token。

之后任意重放都可以拿到token进行修改密码的操作。

2.可以通过XSS(Reflected) High漏洞先拿到token
开启两个页面(为什么这样做后面讲)一个XSS一个CSRF的，在XSS页面拿token

<iframe src="../csrf/" onload=alert(frames[0].document.getElementsByName('user_token')[0].value)>

在这里插入图片描述

拿到的是CSRF页面的token，直接在CSRF的payload中把token加上。
在这里插入图片描述
关于为什么要先打开两个界面，可以查看后端CSRF toekn机制源码

可以发现如果先在XSS页面拿到token，之后再打开CSRF的时候触发generateSessionToken();这个函数的意思是如果存在token则烧毁重新生成新的token，如果存在token则直接验证。
如果现在重新打开CSRF页面，则先把我们拿到的XSStoken进行销毁再重新生成。
如果不重新加载CSRF界面，则直接拿XSStoken进行验证，我们就可以绕过token验证了。

Impossible

观察后端代码，发现修改密码的话需要原密码。

<?phpif( isset( $_GET[ 'Change' ] ) ) {// Check Anti-CSRF tokencheckToken( $_REQUEST[ 'user_token' ], $_SESSION[ 'session_token' ], 'index.php' );// Get input$pass_curr = $_GET[ 'password_current' ];$pass_new  = $_GET[ 'password_new' ];$pass_conf = $_GET[ 'password_conf' ];// Sanitise current password input$pass_curr = stripslashes( $pass_curr );$pass_curr = ((isset($GLOBALS["___mysqli_ston"]) && is_object($GLOBALS["___mysqli_ston"])) ? mysqli_real_escape_string($GLOBALS["___mysqli_ston"],  $pass_curr ) : ((trigger_error("[MySQLConverterToo] Fix the mysql_escape_string() call! This code does not work.", E_USER_ERROR)) ? "" : ""));$pass_curr = md5( $pass_curr );// Check that the current password is correct$data = $db->prepare( 'SELECT password FROM users WHERE user = (:user) AND password = (:password) LIMIT 1;' );$current_user = dvwaCurrentUser();$data->bindParam( ':user', $current_user, PDO::PARAM_STR );$data->bindParam( ':password', $pass_curr, PDO::PARAM_STR );$data->execute();// Do both new passwords match and does the current password match the user?if( ( $pass_new == $pass_conf ) && ( $data->rowCount() == 1 ) ) {// It does!$pass_new = stripslashes( $pass_new );$pass_new = ((isset($GLOBALS["___mysqli_ston"]) && is_object($GLOBALS["___mysqli_ston"])) ? mysqli_real_escape_string($GLOBALS["___mysqli_ston"],  $pass_new ) : ((trigger_error("[MySQLConverterToo] Fix the mysql_escape_string() call! This code does not work.", E_USER_ERROR)) ? "" : ""));$pass_new = md5( $pass_new );// Update database with new password$data = $db->prepare( 'UPDATE users SET password = (:password) WHERE user = (:user);' );$data->bindParam( ':password', $pass_new, PDO::PARAM_STR );$current_user = dvwaCurrentUser();$data->bindParam( ':user', $current_user, PDO::PARAM_STR );$data->execute();// Feedback for the user$html .= "<pre>Password Changed.</pre>";}else {// Issue with passwords matching$html .= "<pre>Passwords did not match or current password incorrect.</pre>";}
}// Generate Anti-CSRF token
generateSessionToken();?>