CodeIgniter 核心代码阅读-安全文件Security.php

Security.php--安全过滤文件

<?php if ( ! defined('BASEPATH')) exit('No direct script access allowed');

//安全类
class CI_Security {

	//URL随机哈希值
	protected $_xss_hash			= '';

	//防csrf攻击的cookie标记的哈希值
	protected $_csrf_hash			= '';

	//防csrf攻击的cookie标记的生存时间
	protected $_csrf_expire			= 7200;

	//防csrf攻击的口令名称
	protected $_csrf_token_name		= 'ci_csrf_token';

	//防csrf攻击的cookie名称
	protected $_csrf_cookie_name	= 'ci_csrf_token';

	//不允许出现的字符串数组
	protected $_never_allowed_str = array(
		'document.cookie'	=> '[removed]',
		'document.write'	=> '[removed]',
		'.parentNode'		=> '[removed]',
		'.innerHTML'		=> '[removed]',
		'window.location'	=> '[removed]',
		'-moz-binding'		=> '[removed]',
		'<!--'				=> '<!--',
		'-->'				=> '-->',
		'<![CDATA['			=> '<![CDATA[',
		'<comment>'			=> '<comment>'
	);

	//不允许出现的正则表达式
	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?"
	);

	//构造函数
	public function __construct()
	{
		// Is CSRF protection enabled?
		if (config_item('csrf_protection') === TRUE)
		{
			// CSRF config
			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
			if (config_item('cookie_prefix'))
			{
				$this->_csrf_cookie_name = config_item('cookie_prefix').$this->_csrf_cookie_name;
			}

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

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

	//csrf检查
	public function csrf_verify()
	{
		// If it's not a POST request we will set the CSRF cookie
		if (strtoupper($_SERVER['REQUEST_METHOD']) !== 'POST')
		{
			return $this->csrf_set_cookie();
		}

		// Do the tokens exist in both the _POST and _COOKIE arrays?
		if ( ! isset($_POST[$this->_csrf_token_name], $_COOKIE[$this->_csrf_cookie_name]))
		{
			$this->csrf_show_error();
		}

		// Do the tokens match?
		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
		unset($_POST[$this->_csrf_token_name]);

		// Nothing should last forever
		unset($_COOKIE[$this->_csrf_cookie_name]);
		$this->_csrf_set_hash();
		$this->csrf_set_cookie();

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

		return $this;
	}

	//设置防csrf的cookie
	public function csrf_set_cookie()
	{
		$expire = time() + $this->_csrf_expire;
		$secure_cookie = (config_item('cookie_secure') === TRUE) ? 1 : 0;

		if ($secure_cookie && (empty($_SERVER['HTTPS']) OR strtolower($_SERVER['HTTPS']) === 'off'))
		{
			return FALSE;
		}

		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;
	}

	//显示csrf错误
	public function csrf_show_error()
	{
		show_error('The action you have requested is not allowed.');
	}

	//获取防csrf的哈希值
	public function get_csrf_hash()
	{
		return $this->_csrf_hash;
	}

	//获取防csrf的口令名称
	public function get_csrf_token_name()
	{
		return $this->_csrf_token_name;
	}

	//XSS攻击过滤
	public function xss_clean($str, $is_image = FALSE)
	{
		/*
		 * Is the string an array?
		 *
		 */
		if (is_array($str))
		{
			while (list($key) = each($str))
			{
				$str[$key] = $this->xss_clean($str[$key]);
			}

			return $str;
		}

		/*
		 * Remove Invisible Characters
		 */
		$str = remove_invisible_characters($str);

		// Validate Entities in URLs
		$str = $this->_validate_entities($str);

		/*
		 * URL Decode
		 *
		 * Just in case stuff like this is submitted:
		 *
		 * <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
		 *
		 */
		$str = rawurldecode($str);

		/*
		 * Convert character entities to ASCII
		 *
		 * 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);

		$str = preg_replace_callback("/<\w+.*?(?=>|<|$)/si", array($this, '_decode_entity'), $str);

		/*
		 * Remove Invisible Characters Again!
		 */
		$str = remove_invisible_characters($str);

		/*
		 * Convert all tabs to spaces
		 *
		 * This prevents strings like this: ja	vascript
		 * NOTE: we deal with spaces between characters later.
		 * NOTE: preg_replace was found to be amazingly slow here on
		 * large blocks of data, so we use str_replace.
		 */

		if (strpos($str, "\t") !== FALSE)
		{
			$str = str_replace("\t", ' ', $str);
		}

		/*
		 * Capture converted string for later comparison
		 */
		$converted_string = $str;

		// Remove Strings that are never allowed
		$str = $this->_do_never_allowed($str);

		/*
		 * Makes PHP tags safe
		 *
		 * Note: XML tags are inadvertently replaced too:
		 *
		 * <?xml
		 *
		 * But it doesn't seem to pose a problem.
		 */
		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
		 *
		 * 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 < $wordlen; $i++)
			{
				$temp .= substr($word, $i, 1)."\s*";
			}

			// We only want to do this when it is followed by a non-word character
			// That way valid stuff like "dealer to" does not become "dealerto"
			$str = preg_replace_callback('#('.substr($temp, 0, -3).')(\W)#is', array($this, '_compact_exploded_words'), $str);
		}

		/*
		 * Remove disallowed Javascript in links or img tags
		 * We used to do some version comparisons and use of stripos for PHP5,
		 * but it is dog slow compared to these simplified non-capturing
		 * preg_match(), especially if the pattern exists in the string
		 */
		do
		{
			$original = $str;

			if (preg_match("/<a/i", $str))
			{
				$str = preg_replace_callback("#<a\s+([^>]*?)(>|$)#si", array($this, '_js_link_removal'), $str);
			}

			if (preg_match("/<img/i", $str))
			{
				$str = preg_replace_callback("#<img\s+([^>]*?)(\s?/?>|$)#si", array($this, '_js_img_removal'), $str);
			}

			if (preg_match("/script/i", $str) OR preg_match("/xss/i", $str))
			{
				$str = preg_replace("#<(/*)(script|xss)(.*?)\>#si", '[removed]', $str);
			}
		}
		while($original != $str);

		unset($original);

		// Remove evil attributes such as style, onclick and xmlns
		$str = $this->_remove_evil_attributes($str, $is_image);

		/*
		 * Sanitize naughty HTML elements
		 *
		 * If a tag containing any of the words in the list
		 * below is found, the tag gets converted to entities.
		 *
		 * 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';
		$str = preg_replace_callback('#<(/*\s*)('.$naughty.')([^><]*)([><]*)#is', array($this, '_sanitize_naughty_html'), $str);

		/*
		 * Sanitize naughty scripting elements
		 *
		 * Similar to above, only instead of looking for
		 * tags it looks for PHP and JavaScript commands
		 * that are disallowed.  Rather than removing the
		 * code, it simply converts the parenthesis to entities
		 * rendering the code un-executable.
		 *
		 * For example:	eval('some code')
		 * Becomes:		eval('some code')
		 */
		$str = preg_replace('#(alert|cmd|passthru|eval|exec|expression|system|fopen|fsockopen|file|file_get_contents|readfile|unlink)(\s*)\((.*?)\)#si', "\\1\\2(\\3)", $str);


		// Final clean up
		// This adds a bit of extra precaution in case
		// something got through the above filters
		$str = $this->_do_never_allowed($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;
	}

	//保护URL的随机哈希值
	public function xss_hash()
	{
		if ($this->_xss_hash == '')
		{
			mt_srand();
			$this->_xss_hash = md5(time() + mt_rand(0, 1999999999));
		}

		return $this->_xss_hash;
	}

	//HTML实体解码
	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('~&#x(0*[0-9a-f]{2,5})~ei', 'chr(hexdec("\\1"))', $str);
		return preg_replace('~&#([0-9]{2,4})~e', 'chr(\\1)', $str);
	}

	//文件名称安全
	public function sanitize_filename($str, $relative_path = FALSE)
	{
		$bad = array(
			"../",
			"<!--",
			"-->",
			"<",
			">",
			"'",
			'"',
			'&',
			'$',
			'#',
			'{',
			'}',
			'[',
			']',
			'=',
			';',
			'?',
			"%20",
			"%22",
			"%3c",		// <
			"%253c",	// <
			"%3e",		// >
			"%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));
	}

	//移除字符间的空格
	protected function _compact_exploded_words($matches)
	{
		return preg_replace('/\s+/s', '', $matches[1]).$matches[2];
	}

	//删除HTML标签里的恶意属性
	protected function _remove_evil_attributes($str, $is_image)
	{
		// All javascript event handlers (e.g. onload, onclick, onmouseover), style, and xmlns
		$evil_attributes = array('on\w*', 'style', 'xmlns', 'formaction');

		if ($is_image === TRUE)
		{
			/*
			 * Adobe Photoshop puts XML metadata into JFIF images, 
			 * including namespacing, so we have to allow this for images.
			 */
			unset($evil_attributes[array_search('xmlns', $evil_attributes)]);
		}

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

			// find occurrences of illegal attribute strings without quotes
			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 attribute strings with quotes (042 and 047 are octal quotes)
			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
			if (count($attribs) > 0)
			{
				$str = preg_replace("/<(\/?[^><]+?)([^A-Za-z<>\-])(.*?)(".implode('|', $attribs).")(.*?)([\s><])([><]*)/i", '<$1 $3$5$6$7', $str, -1, $count);
			}

		} while ($count);

		return $str;
	}

	//净化HTML
	protected function _sanitize_naughty_html($matches)
	{
		// encode opening brace
		$str = '<'.$matches[1].$matches[2].$matches[3];

		// encode captured opening or closing brace to prevent recursive vectors
		$str .= str_replace(array('>', '<'), array('>', '<'),
							$matches[4]);

		return $str;
	}

	//过滤超链接中的js
	protected function _js_link_removal($match)
	{
		return str_replace(
			$match[1],
			preg_replace(
				'#href=.*?(alert\(|alert&\#40;|javascript\:|livescript\:|mocha\:|charset\=|window\.|document\.|\.cookie|<script|<xss|data\s*:)#si',
				'',
				$this->_filter_attributes(str_replace(array('<', '>'), '', $match[1]))
			),
			$match[0]
		);
	}

	//过滤图片链接中的js
	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|<xss|base64\s*,)#si',
				'',
				$this->_filter_attributes(str_replace(array('<', '>'), '', $match[1]))
			),
			$match[0]
		);
	}

	//
	protected function _convert_attribute($match)
	{
		return str_replace(array('>', '<', '\\'), array('>', '<', '\\\\'), $match[0]);
	}

	//过滤html标签属性
	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实体解码
	protected function _decode_entity($match)
	{
		return $this->entity_decode($match[0], strtoupper(config_item('charset')));
	}

	//验证url
	protected function _validate_entities($str)
	{
		/*
		 * Protect GET variables in URLs
		 */

		 // 901119URL5918AMP18930PROTECT8198

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

		/*
		 * Validate standard character entities
		 *
		 * Add a semicolon if missing.  We do this to enable
		 * the conversion of entities to ASCII later.
		 *
		 */
		$str = preg_replace('#(&\#?[0-9a-z]{2,})([\x00-\x20])*;?#i', "\\1;\\2", $str);

		/*
		 * Validate UTF16 two byte encoding (x00)
		 *
		 * Just as above, adds a semicolon if missing.
		 *
		 */
		$str = preg_replace('#(&\#x?)([0-9A-F]+);?#i',"\\1\\2;",$str);

		/*
		 * Un-Protect GET variables in URLs
		 */
		$str = str_replace($this->xss_hash(), '&', $str);

		return $str;
	}

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

	/**
	 * Do Never Allowed
	 *
	 * 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;
	}

	//设置防csrf攻击的哈希值
	protected function _csrf_set_hash()
	{
		if ($this->_csrf_hash == '')
		{
			// If the cookie exists we will use it's value.
			// We don't necessarily want to regenerate it with
			// each page load since a page could contain embedded
			// sub-pages causing this feature to fail
			if (isset($_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;
	}

}