CI框架源码阅览-Security.php

<?php if ( ! defined('BASEPATH')) exit('No direct script access allowed');
/**
 * CodeIgniter
 *
 * An open source application development framework for PHP 5.1.6 or newer
 *
 * @package		CodeIgniter
 * @author		ExpressionEngine Dev Team
 * @copyright	Copyright (c) 2008 - 2011, EllisLab, Inc.
 * @license		http://codeigniter.com/user_guide/license.html
 * @link		http://codeigniter.com
 * @since		Version 1.0
 * @filesource
 */

// ------------------------------------

/**
 * Security Class
 * 本类包含一些方法，能帮助您创建安全的应用程序，对输入的数据进行安全方面的处理。
 * CI官方手册本类的地址：http://codeigniter.org.cn/user_guide/libraries/security.html
 * @package		CodeIgniter
 * @subpackage	Libraries
 * @category	Security
 * @author		ExpressionEngine Dev Team
 * @link		http://codeigniter.com/user_guide/libraries/security.html
 */
class CI_Security {

	/**
	 * Random Hash for protecting URLs
	 * 为保护URL（跨站脚本攻击）的随机hash值
	 * @var string
	 * @access protected
	 */
	protected $_xss_hash			= '';
	/**
	 * Random Hash for Cross Site Request Forgery Protection Cookie
	 * 防止跨站请求伪造cookie的随机hash
	 * @var string
	 * @access protected
	 */
	protected $_csrf_hash			= '';
	/**
	 * Expiration time for Cross Site Request Forgery Protection Cookie
	 * Defaults to two hours (in seconds)
	 * 跨站请求保护Cookie的过期时间，默认是2小时（单位秒）
	 * @var int
	 * @access protected
	 */
	protected $_csrf_expire			= 7200;
	/**
	 * Token name for Cross Site Request Forgery 伪造 Protection Cookie
	 * 跨站请求伪造保护的Cookie令牌名
	 * @var string
	 * @access protected
	 */
	protected $_csrf_token_name		= 'ci_csrf_token';
	/**
	 * Cookie name for Cross Site Request Forgery Protection Cookie
	 * 跨站请求伪造保护的Cookie的Cookie名
	 * @var string
	 * @access protected
	 */
	protected $_csrf_cookie_name	= 'ci_csrf_token';
	/**
	 * List of never allowed strings
	 * 决不允许的字符串的列表
	 * @var array
	 * @access protected
	 */
	protected $_never_allowed_str = array(
		'document.cookie'	=> '[removed]',
		'document.write'	=> '[removed]',
		'.parentNode'		=> '[removed]',
		'.innerHTML'		=> '[removed]',
		'window.location'	=> '[removed]',
		'-moz-binding'		=> '[removed]',
		'<!--'				=> '<!--',
		'-->'				=> '-->',
		' ''			=> '<comment>'
	);

	/* never allowed, regex replacement */
	/**
	 * List of never allowed regex replacement
	 * 不允许的正则替换字符串列表
	 * @var array
	 * @access protected
	 */
	protected $_never_allowed_regex = array(
		'javascript\s*:',
		'expression\s*(\(|&\#40;)', // CSS and IE
		'vbscript\s*:', // IE, surprise!
		'Redirect\s+302',
		"([\"'])?data\s*:[^\\1]*?base64[^\\1]*?,[^\\1]*?\\1?"
	);

	/**
	 * Constructor
	 *
	 * @return	void
	 */
	public function __construct()
	{
		// Is CSRF protection enabled?
		// csrf 是否开启 
		if (config_item('csrf_protection') === TRUE)
		{
			// CSRF config 读取CSRF 配置并赋值给本类下的对应的属性
			foreach (array('csrf_expire', 'csrf_token_name', 'csrf_cookie_name') as $key)
			{
				if (FALSE !== ($val = config_item($key)))
				{
					$this->{'_'.$key} = $val;
				}
			}

			// Append application specific cookie prefix
			// 添加应用指定的cookie前缀
			if (config_item('cookie_prefix'))
			{
				$this->_csrf_cookie_name = config_item('cookie_prefix').$this->_csrf_cookie_name;
			}

			// Set the CSRF hash
			// 设置CSRF hash
			$this->_csrf_set_hash();
		}

		log_message('debug', "Security Class Initialized");
	}

	// --------------------------------

	/**
	 * Verify Cross Site Request Forgery Protection
	 * 验证跨站请求伪造保护
	 * @return	object
	 */
	public function csrf_verify()
	{
		// If it's not a POST request we will set the CSRF cookie
		// 如果不是post请求我们要设置 CSRF cookie
		if (strtoupper($_SERVER['REQUEST_METHOD']) !== 'POST')
		{
			return $this->csrf_set_cookie();
		}

		// Do the tokens exist in both the _POST and _COOKIE arrays?
		// 如果请求令牌不存在，调用csrf_show_error 报错
		if ( ! isset($_POST[$this->_csrf_token_name], $_COOKIE[$this->_csrf_cookie_name]))
		{
			$this->csrf_show_error();
		}

		// Do the tokens match?
		// 如果令牌不对，报错。
		if ($_POST[$this->_csrf_token_name] != $_COOKIE[$this->_csrf_cookie_name])
		{
			$this->csrf_show_error();
		}

		// We kill this since we're done and we don't want to
		// polute the _POST array
		// 销毁领牌子，因为我们不想污染_POST 数组
		unset($_POST[$this->_csrf_token_name]);

		// Nothing should last forever
		// 销毁cookie名 并重新设置hash和cookie
		unset($_COOKIE[$this->_csrf_cookie_name]);
		$this->_csrf_set_hash();
		$this->csrf_set_cookie();

		log_message('debug', 'CSRF token verified');

		return $this;
	}

	// --------------------------------

	/**
	 * Set Cross Site Request Forgery Protection Cookie
	 * 设置伪造cookie保护跨站请求
	 * @return	object
	 */
	public function csrf_set_cookie()
	{
		$expire = time() + $this->_csrf_expire;
		$secure_cookie = (config_item('cookie_secure') === TRUE) ? 1 : 0;

		// 当存在https时设置cookie
		if ($secure_cookie && (empty($_SERVER['HTTPS']) OR strtolower($_SERVER['HTTPS']) === 'off'))
		{
			return FALSE;
		}

		// 设置cookie
		setcookie($this->_csrf_cookie_name, $this->_csrf_hash, $expire, config_item('cookie_path'), config_item('cookie_domain'), $secure_cookie);

		log_message('debug', "CRSF cookie Set");

		return $this;
	}

	// --------------------------------

	/**
	 * Show CSRF Error
	 * 显示CSRF错误
	 * @return	void
	 */
	public function csrf_show_error()
	{
		show_error('The action you have requested is not allowed.');
	}

	// --------------------------------

	/**
	 * Get CSRF Hash
	 * 获取CSRF hash
	 * Getter Method
	 *
	 * @return 	string 	self::_csrf_hash
	 */
	public function get_csrf_hash()
	{
		return $this->_csrf_hash;
	}

	// --------------------------------

	/**
	 * Get CSRF Token Name
	 * 获取CSRF 令排名
	 * Getter Method
	 *
	 * @return 	string 	self::csrf_token_name
	 */
	public function get_csrf_token_name()
	{
		return $this->_csrf_token_name;
	}

	// --------------------------------

	/**
	 * XSS Clean
	 * 
	 * Sanitizes 清理 data so that Cross Site Scripting Hacks can be
	 * prevented.阻止  This function does a fair amount of work but
	 * it is extremely thorough, designed to prevent even the
	 * most obscure XSS attempts 企图.  Nothing is ever 100% foolproof,
	 * of course, but I haven't been able to get anything passed
	 * the filter.
	 * 对数据进行过滤，从而可以防止跨站脚本攻击。这个函数做了一些工作，但是它是非常彻底的，
	 * 甚至可以防止大多数模糊的XSS企图。当然，没有什么是100%安全的，
	 * 但是我们在这个过滤器中已经做了所欲我们所能做想到的了。
	 *
	 * Note: This function should only be used to deal with data
	 * upon submission.  It's not something that should
	 * be used for general runtime processing.
	 * 注意：这个函数只能用来处理已经提交的数据。
	 * 在通常的运行过程中，不应该使用该函数。
	 *
	 * This function was based in part on some code and ideas I
	 * got from Bitflux: http://channel.bitflux.ch/wiki/XSS_Prevention
	 *
	 * To help develop this script I used this great list of
	 * vulnerabilities along with a few other hacks I've
	 * harvested from examining vulnerabilities in other programs:
	 * http://ha.ckers.org/xss.html
	 *
	 * @param	mixed	string or array
	 * @param 	bool
	 * @return	string
	 */
	public function xss_clean($str, $is_image = FALSE)
	{
		/*
		 * Is the string an array?
		 * 需要过滤的字符串是数组吗？
		 *
		 */
		if (is_array($str))
		{
			while (list($key) = each($str))
			{
				$str[$key] = $this->xss_clean($str[$key]);
			}

			return $str;
		}

		/*
		 * Remove Invisible Characters
		 * 移除不可见字符
		 */
		$str = remove_invisible_characters($str);

		// Validate Entities in URLs
		// 验证在URL中的字符实体
		$str = $this->_validate_entities($str);

		/*
		 * URL Decode
		 * URL解码
		 * Just in case stuff like this is submitted:
		 * 防止下面这样的东西提交
		 * <a href="http://%77%77%77%2E%67%6F%6F%67%6C%65%2E%63%6F%6D">Google</a>
		 *
		 * Note: Use rawurldecode() so it does not remove plus signs 
		 * rawurldecode() 不会把加号（'+'）解码为空格，而 urldecode() 可以。
		 *
		 */
		$str = rawurldecode($str);

		/*
		 * Convert character entities to ASCII
		 * 把实体字符转换成ASCII码
		 * 这使得我们下面的测试是可靠的，我们仅仅转换实体内的标签，因为这些是会造成安全问题的实体
		 * This permits our tests below to work reliably.
		 * We only convert entities that are within tags since
		 * these are the ones that will pose security problems.
		 *
		 */

		$str = preg_replace_callback("/[a-z]+=([\'\"]).*?\\1/si", array($this, '_convert_attribute'), $str);

		$str = preg_replace_callback("/|_do_never_allowed($str);

		/*
		 * Makes PHP tags safe
		 * 使PHP标签安全
		 * Note: XML tags are inadvertently replaced too:
		 * 注意： XML标签也会被无意的替换
		 * <?xml *
		 * But it doesn't seem to pose a problem.
		 * 但是它似乎不会构成问题
		 */
		if ($is_image === TRUE)
		{
			// Images have a tendency to have the PHP short opening and
			// closing tags every so often so we skip those and only
			// do the long opening tags.
			$str = preg_replace('/<\?(php)/i', "<?\\1", $str);
		}
		else
		{
			$str = str_replace(array('<?', '?'.'>'),  array('', '?>'), $str);
		}

		/*
		 * Compact any exploded words
		 * 压缩所有分解了的单词
		 * This corrects words like:  j a v a s c r i p t
		 * These words are compacted back to their correct state.
		 */
		$words = array(
			'javascript', 'expression', 'vbscript', 'script', 'base64',
			'applet', 'alert', 'document', 'write', 'cookie', 'window'
		);

		foreach ($words as $word)
		{
			$temp = '';

			for ($i = 0, $wordlen = strlen($word); $i ]*?)(>|$)#si", array($this, '_js_link_removal'), $str);
			}

			if (preg_match("/<img  preg_replace_callback alt=" CI框架源码阅览-Security.php " >]*?)(\s?/?>|$)#si", array($this, '_js_img_removal'), $str);
			}

			if (preg_match("/script/i", $str) OR preg_match("/xss/i", $str))
			{
				$str = preg_replace("##si", '[removed]', $str);
			}
		}
		while($original != $str);

		unset($original);

		// Remove evil attributes such as style, onclick and xmlns
		// 移除有害的属性，比如style ， onclick ， xmlns
		$str = $this->_remove_evil_attributes($str, $is_image);

		/*
		 * Sanitize naughty HTML elements
		 * 清理不适当的HTML元素
		 * If a tag containing any of the words in the list
		 * below is found, the tag gets converted to entities.
		 * 如果一个标签包含任何一个下面列表中的单词，这个标签转换为一个字符实体
		 * So this: <blink>
		 * Becomes: <blink>
		 */
		$naughty = 'alert|applet|audio|basefont|base|behavior|bgsound|blink|body|embed|expression|form|frameset|frame|head|html|ilayer|iframe|input|isindex|layer|link|meta|object|plaintext|style|script|textarea|title|video|xml|xss';
		$str = preg_replace_callback('#_do_never_allowed($str);

		/*
		 * Images are Handled in a Special Way
		 * - Essentially, we want to know that after all of the character
		 * conversion is done whether any unwanted, likely XSS, code was found.
		 * If not, we return TRUE, as the image is clean.
		 * However, if the string post-conversion does not matched the
		 * string post-removal of XSS, then it fails, as there was unwanted XSS
		 * code found and removed/changed during processing.
		 */

		if ($is_image === TRUE)
		{
			return ($str == $converted_string) ? TRUE: FALSE;
		}

		log_message('debug', "XSS Filtering completed");
		return $str;
	}

	// --------------------------------

	/**
	 * Random Hash for protecting URLs
	 * 随即生成一个_xss_hssh
	 * @return	string
	 */
	public function xss_hash()
	{
		if ($this->_xss_hash == '')
		{
			mt_srand();
			$this->_xss_hash = md5(time() + mt_rand(0, 1999999999));
		}

		return $this->_xss_hash;
	}

	// --------------------------------

	/**
	 * HTML Entities Decode
	 * HTML 实体解码
	 * This function is a replacement for html_entity_decode()
	 * 这个函数用来替换 html_entity_decode()函数
	 * The reason we are not using html_entity_decode() by itself is because
	 * while it is not technically技术上 correct to leave out the semicolon
	 * at the end of an entity most browsers will still interpret the entity
	 * correctly.  html_entity_decode() does not convert entities without
	 * semicolons, so we are left with our own little solution here. Bummer.
	 * 当编码字符后没有写；时，大部分浏览器都能够正确的解释代码，但是，html_entity_decode将不会解释它
	 * html_entity_decode()不会转换没有分号的实体，所以使用自己的解决方案
	 * @param	string
	 * @param	string
	 * @return	string
	 */
	public function entity_decode($str, $charset='UTF-8')
	{
		if (stristr($str, '&') === FALSE)
		{
			return $str;
		}

		$str = html_entity_decode($str, ENT_COMPAT, $charset);
		$str = preg_replace('~(0*[0-9a-f]{2,5})~ei', 'chr(hexdec("\\1"))', $str);
		return preg_replace('~([0-9]{2,4})~e', 'chr(\\1)', $str);
	}

	// --------------------------------

	/**
	 * Filename Security
	 * 文件名安全
	 * @param	string
	 * @param 	bool
	 * @return	string
	 */
	public function sanitize_filename($str, $relative_path = FALSE)
	{
		$bad = array(
			"../",
			"<!--",
			"-->",
			"",
			"'",
			'"',
			'&',
			'$',
			'#',
			'{',
			'}',
			'[',
			']',
			'=',
			';',
			'?',
			"%20",
			"%22",
			"%3c",		// 
			"%0e",		// >
			"%28",		// (
			"%29",		// )
			"%2528",	// (
			"%26",		// &
			"%24",		// $
			"%3f",		// ?
			"%3b",		// ;
			"%3d"		// =
		);

		if ( ! $relative_path)
		{
			$bad[] = './';
			$bad[] = '/';
		}

		$str = remove_invisible_characters($str, FALSE);
		return stripslashes(str_replace($bad, '', $str));
	}

	// ----------------------------

	/**
	 * Compact Exploded Words
	 * 压缩搜索到得单词
	 * Callback function for xss_clean() to remove whitespace from
	 * things like j a v a s c r i p t
	 * 回调函数，用于xss_clean()，从类似于 j a v a s c r i p t中移除空格
     * 
	 *
	 * @param	type
	 * @return	type
	 */
	protected function _compact_exploded_words($matches)
	{
		return preg_replace('/\s+/s', '', $matches[1]).$matches[2];
	}

	// --------------------------------

	/*
	 * Remove Evil HTML Attributes (like evenhandlers and style)
	 * 移除有害的html属性，（像事件处理和样式）
	 * It removes the evil attribute and either:
	 * 	- Everything up until a space
	 *		For example, everything between the pipes:
	 *		<a class="link">
	 * 	- Everything inside the quotes
	 *		For example, everything between the pipes:
	 *		</a><a alert class="link">
	 *
	 * @param string $str The string to check
	 * @param boolean $is_image TRUE if this is an image
	 * @return string The string with the evil attributes removed
	 */
	protected function _remove_evil_attributes($str, $is_image)
	{
		// All javascript event handlers (e.g. onload, onclick, onmouseover), style, and xmlns
		// 所有的havascript事件处理器
		$evil_attributes = array('on\w*', 'style', 'xmlns', 'formaction');

		if ($is_image === TRUE)
		{
			/*
			 * Adobe Photoshop puts XML metadata into JFIF images, 
			 * including namespacing, so we have to allow this for images.
			 * Adobe Photoshop在JFIF图片中放入了XML元数据
			 * 包含命名空间，所以我们必须对图片允许这些
			 */
			unset($evil_attributes[array_search('xmlns', $evil_attributes)]);
		}

		do {
			$count = 0;
			$attribs = array();

			// find occurrences of illegal attribute strings without quotes
			// 找出没有加引号的的不合法的属性
			preg_match_all('/('.implode('|', $evil_attributes).')\s*=\s*([^\s>]*)/is', $str, $matches, PREG_SET_ORDER);

			foreach ($matches as $attr)
			{

				$attribs[] = preg_quote($attr[0], '/');
			}

			// find occurrences of illegal 非法 attribute strings with quotes (042 and 047 are octal quotes)
			// 找出没有引号的不合法属性（042，4,0是八进制引号）
			preg_match_all("/(".implode('|', $evil_attributes).")\s*=\s*(\042|\047)([^\\2]*?)(\\2)/is",  $str, $matches, PREG_SET_ORDER);

			foreach ($matches as $attr)
			{
				$attribs[] = preg_quote($attr[0], '/');
			}

			// replace illegal attribute strings that are inside an html tag
			// 替换html标签中的非法属性
			if (count($attribs) > 0)
			{
				$str = preg_replace("/\-])(.*?)(".implode('|', $attribs).")(.*?)([\s>', '', '_filter_attributes(str_replace(array(''), '', $match[1]))
			),
			$match[0]
		);
	}

	// --------------------------------

	/**
	 * JS Image Removal
	 * js图片清理
	 * Callback function for xss_clean() to sanitize image tags
	 * This limits the PCRE backtracks, making it more performance friendly
	 * and prevents PREG_BACKTRACK_LIMIT_ERROR from being triggered in
	 * PHP 5.2+ on image tag heavy strings
	 *
	 * @param	array
	 * @return	string
	 */
	protected function _js_img_removal($match)
	{
		return str_replace(
			$match[1],
			preg_replace(
				'#src=.*?(alert\(|alert&\#40;|javascript\:|livescript\:|mocha\:|charset\=|window\.|document\.|\.cookie|<script>_filter_attributes(str_replace(array('<', '>'), '', $match[1]))
			),
			$match[0]
		);
	}

	// --------------------------------

	/**
	 * Attribute Conversion
	 * 属性转换
	 * Used as a callback for XSS Clean
	 *
	 * @param	array
	 * @return	string
	 */
	protected function _convert_attribute($match)
	{
		return str_replace(array('>', '<', '\\'), array('>', '<', '\\\\'), $match[0]);
	}

	// --------------------------------

	/**
	 * Filter Attributes
	 * 过滤属性
	 * Filters tag attributes for consistency and safety
	 * 为一致性和安全性过滤标签属性
	 * @param	string
	 * @return	string
	 */
	protected function _filter_attributes($str)
	{
		$out = '';

		if (preg_match_all('#\s*[a-z\-]+\s*=\s*(\042|\047)([^\\1]*?)\\1#is', $str, $matches))
		{
			foreach ($matches[0] as $match)
			{
				$out .= preg_replace("#/\*.*?\*/#s", '', $match);
			}
		}

		return $out;
	}

	// --------------------------------

	/**
	 * HTML Entity Decode Callback
	 * html实体解码
	 * Used as a callback for XSS Clean
	 *
	 * @param	array
	 * @return	string
	 */
	protected function _decode_entity($match)
	{
		return $this->entity_decode($match[0], strtoupper(config_item('charset')));
	}

	// --------------------------------

	/**
	 * Validate URL entities
	 * 验证URL字符实体
	 * Called by xss_clean()
	 *
	 * @param 	string
	 * @return 	string
	 */
	protected function _validate_entities($str)
	{
		/*
		 * Protect GET variables in URLs
		 * 保护url中的GET变量
		 */

		 // 901119URL5918AMP18930PROTECT8198

		$str = preg_replace('|\&([a-z\_0-9\-]+)\=([a-z\_0-9\-]+)|i', $this->xss_hash()."\\1=\\2", $str);

		/*
		 * Validate standard character entities
		 * 验证标准字符实体
		 *
		 * Add a semicolon if missing.  We do this to enable
		 * the conversion of entities to ASCII later.
		 * 如果没有的话，添加一个分号。这样做是为了以后允许字符实体到ASCII的转换
		 * 
		 */
		$str = preg_replace('#(&\#?[0-9a-z]{2,})([\x00-\x20])*;?#i', "\\1;\\2", $str);

		/*
		 * Validate UTF16 two byte encoding (x00)
		 * 验证UTF16两个字节的编码（x00）
		 * Just as above, adds a semicolon if missing.
		 * 像上面一样如果不存在添加一个分号。
		 */
		$str = preg_replace('#(&\#x?)([0-9A-F]+);?#i',"\\1\\2;",$str);

		/*
		 * Un-Protect GET variables in URLs
		 * URL中不保护的GET变量
		 */
		$str = str_replace($this->xss_hash(), '&', $str);

		return $str;
	}

	// ----------------------------------

	/**
	 * Do Never Allowed
	 * 移除不允许的字符
	 * A utility function for xss_clean()
	 * 
	 * @param 	string
	 * @return 	string
	 */
	protected function _do_never_allowed($str)
	{
		$str = str_replace(array_keys($this->_never_allowed_str), $this->_never_allowed_str, $str);

		foreach ($this->_never_allowed_regex as $regex)
		{
			$str = preg_replace('#'.$regex.'#is', '[removed]', $str);
		}

		return $str;
	}

	// --------------------------------

	/**
	 * Set Cross Site Request Forgery Protection Cookie
	 * 设置跨站请求保护Cookie
	 * @return	string
	 */
	protected function _csrf_set_hash()
	{
		if ($this->_csrf_hash == '')
		{
			// If the cookie exists we will use it's value.
			// We don't necessarily want to regenerate it with
			// each page load since a page could contain embedded
			// sub-pages causing this feature to fail
			// 如果Cookie存在，我们将使用原先的值
			// 我们不是必须要在每各加载的页面都要更新它，因为当一个页面可能要包含嵌入的子页面时，
			// 嵌入的子页面会造成这个特性的失败
			if (isset($_COOKIE[$this->_csrf_cookie_name]) &&
				preg_match('#^[0-9a-f]{32}$#iS', $_COOKIE[$this->_csrf_cookie_name]) === 1)
			{
				return $this->_csrf_hash = $_COOKIE[$this->_csrf_cookie_name];
			}

			return $this->_csrf_hash = md5(uniqid(rand(), TRUE));
		}

		return $this->_csrf_hash;
	}

}

/* End of file Security.php */
/* Location: ./system/libraries/Security.php */
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