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<script></script>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 >, &quot 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 [[\yii\base\Application::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 Name Description
ENT_COMPAT Will convert double-quotes and leave single-quotes alone.
ENT_QUOTES Will convert both double and single quotes.
ENT_NOQUOTES Will leave both double and single quotes unconverted.
ENT_IGNORE Silently discard invalid code unit sequences instead of returning an empty string. Using this flag is discouraged as it » may have security implications.
ENT_SUBSTITUTE Replace invalid code unit sequences with a Unicode Replacement Character U FFFD (UTF-8) or &#FFFD; (otherwise) instead of returning an empty string.
ENT_DISALLOWED Replace 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_HTML401 Handle code as HTML 4.01.
ENT_XML1 Handle code as XML 1.
ENT_XHTML Handle code as XHTML.
ENT_HTML5 Handle 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 &amp;
" (double quote) becomes &quot; when ENT_NOQUOTES is not set.
' (single quote) becomes &#039; (or &apos;) only when ENT_QUOTES is set.
< (less than) becomes &lt;
> (greater than) becomes &gt;

<?php
$new = htmlspecialchars("<a href='test'>Test</a>", ENT_QUOTES);
echo $new; // &lt;a href=&#039;test&#039;&gt;Test&lt;/a&gt;
?>

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
$str = "A 'quote' is <b>bold</b>";
// Outputs: A 'quote' is &lt;b&gt;bold&lt;/b&gt;
echo htmlentities($str);
// Outputs: A &#039;quote&#039; is &lt;b&gt;bold&lt;/b&gt;
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=