CSRF

CSRF

CSRF，跨站域请求伪造，通常攻击者会伪造一个场景（例如一条链接），来诱使用户点击，用户一旦点击，黑客的攻击目的也就达到了，他可以盗用你的身份，以你的名义发送恶意请求。CSRF攻击的关键就是利用受害者的cookie向服务器发送伪造请求。

和XSS有什么不同？

CSRF是以用户的权限去做事情，自己本身并没有获取到权限；XSS是直接盗取了用户的权限进行攻击。

LOW级别

源码分析

if( isset( $_GET[ 'Change' ] ) ) {
    // 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"],  $insert ) or die( '
' . ((is_object($GLOBALS["___mysqli_ston"])) ? mysqli_error($GLOBALS["___mysqli_ston"]) : (($___mysqli_res = mysqli_connect_error()) ? $___mysqli_res : false)) . '
' );

        // Feedback for the user
        echo "
Password Changed.
";
    }
    else {
        // Issue with passwords matching
        echo "
Passwords did not match.
";
    }

    ((is_null($___mysqli_res = mysqli_close($GLOBALS["___mysqli_ston"]))) ? false : $___mysqli_res);
}

?> 

发现只是坐了密码比对，并没有其他认证，只需要输入的新密码和确认的新密码保持一致即可

New password：123456

Confirm new password：123456

将地址栏中的两个密码改成123

同样可以修改成功

修改密码的链接过于明显，可以使用一些缩短链接的方法，这样用户更容易上当。

也可以写一个html简单脚本，把img标签隐藏起来

<img src="http://192.168.80.145/dvwa/vulnerabilities/csrf/?password_new=123456&password_conf=123456&Change=Change#" border="0" style="display:none;">
<h1>
    404
h1>
<h2>
    file not found!!
h2>

当用户点击访问这个页面时，会以为访问的页面丢失了，但是当他打开这个页面时，用户的密码已经被修改了！

Medium级别

源码分析

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
            $current_user = dvwaCurrentUser();
            $insert = "UPDATE `users` SET password = '$pass_new' WHERE user = '" . $current_user . "';";
            $result = mysqli_query($GLOBALS["___mysqli_ston"],  $insert ) or die( '
' . ((is_object($GLOBALS["___mysqli_ston"])) ? mysqli_error($GLOBALS["___mysqli_ston"]) : (($___mysqli_res = mysqli_connect_error()) ? $___mysqli_res : false)) . '
' );

            // Feedback for the user
            echo "
Password Changed.
";
        }
        else {
            // Issue with passwords matching
            echo "
Passwords did not match.
";
        }
    }
    else {
        // Didn't come from a trusted source
        echo "
That request didn't look correct.
";
    }

    ((is_null($___mysqli_res = mysqli_close($GLOBALS["___mysqli_ston"]))) ? false : $___mysqli_res);
}

?> 

stripos() 函数查找字符串在另一字符串中第一次出现的位置（不区分大小写）代码检查了保留变量HTTP_REFERER （http包头部的Referer字段的值，表示来源地址）是否包含SERVER_NAME（http包头部的 Host 字段表示要访问的主机名）。

 if( stripos( $_SERVER[ 'HTTP_REFERER' ] ,$_SERVER[ 'SERVER_NAME' ]) !== false )`
这里通过STRIPOS函数对比HTTP_REFERER，SERVER_NAME是否一致
后台的服务器会去检查HTTP_REFERER函数是否包含SERVER_NAME(host参数、主机名等)，用此方法来抵御CSRF攻击
# 方法：
要想通过验证，就必须保证在Http请求中Referer字段中必须包含Host，所以攻击者只需要将文件名改成受害者的Host以及name就可以完美通过验证！

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使用burp suit抓包 发送到Repeater

将Host与Referer修改一致

High级别

$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 token
    checkToken( $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 {
        echo "
" . $return_message . "
";
    }
}

// Generate Anti-CSRF token
generateSessionToken();

?> 

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直接修改cook的安全等级绕过token认证机制

Burp Suite抓包，发送到Repeater

安全等级修改为low

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