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 >, " 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 `$content` will not be further encoded. * @return string the encoded content * @see decode() * @see */ public static function encode($content, $doubleEncode = true) { return htmlspecialchars($content, ENT_QUOTES | ENT_SUBSTITUTE, Yii::$app->charset, $doubleEncode); }
htmlspecialchars & htmlentities & urlencode 三者的区别：
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 &
" (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("<a href='https://www.jb51.net/article/test'>Test</a>", ENT_QUOTES); echo $new; // <a href='test'>Test</a> ?>
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 $str = "A 'quote' is <b>bold</b>"; // Outputs: A 'quote' is <b>bold</b> echo htmlentities($str); // Outputs: A 'quote' is <b>bold</b> echo htmlentities($str, ENT_QUOTES); ?>
urlencode
URL 编码是为了符合url的规范。因为在标准的url规范中中文和很多的字符是不允许出现在url中的。
例如在baidu中搜索"测试汉字"。 URL会变成
?wd=%B2%E2%CA%D4%BA%BA%D7%D6&rsv_bp=0&rsv_spt=3&inputT=7477
所谓URL编码就是： 把所有非字母数字字符都将被替换成百分号（%）后跟两位十六进制数，空格则编码为加号（+）
此字符串中除了 -_. 之外的所有非字母数字字符都将被替换成百分号（%）后跟两位十六进制数，空格则编码为加号（+）。此编码与 WWW 表单 POST 数据的编码方式是一样的，同时与 application/x-www-form-urlencoded 的媒体类型编码方式一样。由于历史原因，此编码在将空格编码为加号（+）方面与 RFC1738 编码（参见 rawurlencode()）不同。
<?php echo '<a href="mycgi?foo=', urlencode($userinput), '">'; ?>
<?php $query_string = 'foo=' . urlencode($foo) . '&bar=' . urlencode($bar); echo '<a href="mycgi?' . htmlentities($query_string) . '">'; ?>