Yii2的XSS攻击防范策略分析

本文实例讲述了Yii2的XSS攻击防范策略。分享给大家供大家参考，具体如下：

XSS 漏洞修复

原则：不相信客户输入的数据

注意: 攻击代码不一定在中

① 将重要的cookie标记为http only, 这样的话Javascript 中的document.cookie语句就不能获取到cookie了.

② 只允许用户输入我们期望的数据。 例如：年龄的textbox中，只允许用户输入数字。 而数字之外的字符都过滤掉。

③ 对数据进行Html Encode 处理

④ 过滤或移除特殊的Html标签， 例如: script, iframe , < for <, > for >, " for

⑤ 过滤JavaScript 事件的标签。例如 "onclick=", "onfocus" 等等。

Yii中的XSS防范

<?php echo CHtml::encode($user->name) ?>

此方法的源码：

/**
* Encodes special characters into HTML entities.
* The [[yiibaseApplication::charset|application charset]] will be used for encoding.
* @param string $content the content to be encoded
* @param boolean $doubleEncode whether to encode HTML entities in `$content`. If false,
* HTML entities in `$content` will not be further encoded.
* @return string the encoded content
* @see decode()
* @see http://www.php.net/manual/en/function.htmlspecialchars.php
*/
public static function encode($content, $doubleEncode = true)
{
  return htmlspecialchars($content, ENT_QUOTES | ENT_SUBSTITUTE, Yii::$app->charset, $doubleEncode);
}

htmlspecialchars & htmlentities & urlencode 三者的区别：

http://php.net/manual/zh/function.htmlspecialchars.php

http://php.net/manual/zh/function.htmlentities.php

http://cn2.php.net/manual/zh/function.urlencode.php

Available flags constants

Constant NameDescription

ENT_COMPATWill convert double-quotes and leave single-quotes alone.

ENT_QUOTESWill convert both double and single quotes.

ENT_NOQUOTESWill leave both double and single quotes unconverted.

ENT_IGNORESilently discard invalid code unit sequences instead of returning an empty string. Using this flag is discouraged as it » may have security implications.

ENT_SUBSTITUTEReplace invalid code unit sequences with a Unicode Replacement Character U+FFFD (UTF-8) or &#FFFD; (otherwise) instead of returning an empty string.

ENT_DISALLOWEDReplace invalid code points for the given document type with a Unicode Replacement Character U+FFFD (UTF-8) or &#FFFD; (otherwise) instead of leaving them as is. This may be useful, for instance, to ensure the well-formedness of XML documents with embedded external content.

ENT_HTML401Handle code as HTML 4.01.

ENT_XML1Handle code as XML 1.

ENT_XHTMLHandle code as XHTML.

ENT_HTML5Handle code as HTML 5.

htmlspecialchars

Convert special characters to HTML entities

string htmlspecialchars ( 
      string $string 
      [, int $flags = ENT_COMPAT | ENT_HTML401 
      [, string $encoding = ini_get("default_charset") 
      [, bool $double_encode = true ]
    ]
  ] 
)

The translations performed are:

& (ampersand) becomes &

" (double quote) becomes " when ENT_NOQUOTES is not set.

' (single quote) becomes ' (or ') only when ENT_QUOTES is set.

< (less than) becomes <

> (greater than) becomes >

<?php
$new = htmlspecialchars("Test", ENT_QUOTES);
echo $new; // Test
?>

htmlentities

Convert all applicable characters to HTML entities

string htmlentities ( 
      string $string 
      [, int $flags = ENT_COMPAT | ENT_HTML401 
      [, string $encoding = ini_get("default_charset") 
      [, bool $double_encode = true ]
    ]
  ] 
)

<?php
$str = "A 'quote' is bold";
// Outputs: A 'quote' is bold
echo htmlentities($str);
// Outputs: A 'quote' is bold
echo htmlentities($str, ENT_QUOTES);
?>

urlencode

URL 编码是为了符合url的规范。因为在标准的url规范中中文和很多的字符是不允许出现在url中的。

例如在baidu中搜索"测试汉字"。 URL会变成

http://www.baidu.com/s?wd=%B2%E2%CA%D4%BA%BA%D7%D6&rsv_bp=0&rsv_spt=3&inputT=7477

所谓URL编码就是：把所有非字母数字字符都将被替换成百分号（%）后跟两位十六进制数，空格则编码为加号（+）

此字符串中除了 -_. 之外的所有非字母数字字符都将被替换成百分号（%）后跟两位十六进制数，空格则编码为加号（+）。此编码与 WWW 表单 POST 数据的编码方式是一样的，同时与 application/x-www-form-urlencoded 的媒体类型编码方式一样。由于历史原因，此编码在将空格编码为加号（+）方面与 RFC1738 编码（参见 rawurlencode()）不同。

<?php
echo '';
?>

<?php
$query_string = 'foo=' . urlencode($foo) . '&bar=' . urlencode($bar);
echo '';
?>