input.html

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        <div class='alert alert-success'>
            我們開始分析core/Input.php。<br/>
            它會先針對使用者傳入的值進行處理、確保系統安全。
        </div>

        <!-- You also need to add some content to highlight, but that is covered elsewhere. -->
        <pre class="brush: 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		https://codeigniter.com/user_guide/license.html
 * @link		https://codeigniter.com
 * @since		Version 1.0
 * @filesource
 */

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

/**
 * Input Class
 *
 * Pre-processes global input data for security
 *
 * @package		CodeIgniter
 * @subpackage	Libraries
 * @category	Input
 * @author		ExpressionEngine Dev Team
 * @link		https://codeigniter.com/user_guide/libraries/input.html
 */
class CI_Input {

	/**
	 * IP address of the current user
	 *
	 * @var string
	 */
	var $ip_address				= FALSE;
	/**
	 * user agent (web browser) being used by the current user
	 *
	 * @var string
	 */
	var $user_agent				= FALSE;
	/**
	 * If FALSE, then $_GET will be set to an empty array
	 *
	 * @var bool
	 */
	var $_allow_get_array		= TRUE;
	/**
	 * If TRUE, then newlines are standardized
	 *
	 * @var bool
	 */
	var $_standardize_newlines	= TRUE;
	/**
	 * Determines whether the XSS filter is always active when GET, POST or COOKIE data is encountered
	 * Set automatically based on config setting
	 *
	 * @var bool
	 */
	var $_enable_xss			= FALSE;
	/**
	 * Enables a CSRF cookie token to be set.
	 * Set automatically based on config setting
	 *
	 * @var bool
	 */
	var $_enable_csrf			= FALSE;
	/**
	 * List of all HTTP request headers
	 *
	 * @var array
	 */
	protected $headers			= array();

	/**
	 * Constructor
	 *
	 * Sets whether to globally enable the XSS processing
	 * and whether to allow the $_GET array
	 *
	 * @return	void
	 */
	public function __construct()
	{
		log_message('debug', "Input Class Initialized");

		$this->_allow_get_array	= (config_item('allow_get_array') === TRUE);
		$this->_enable_xss		= (config_item('global_xss_filtering') === TRUE);
		$this->_enable_csrf		= (config_item('csrf_protection') === TRUE);

		global $SEC;
		$this->security =& $SEC;

		// Do we need the UTF-8 class?
		if (UTF8_ENABLED === TRUE)
		{
			global $UNI;
			$this->uni =& $UNI;
		}

		// Sanitize global arrays
		$this->_sanitize_globals();
	}

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

	/**
	 * Fetch from array
	 *
	 * This is a helper function to retrieve values from global arrays
	 *
	 * @access	private
	 * @param	array
	 * @param	string
	 * @param	bool
	 * @return	string
	 */
	function _fetch_from_array(&$array, $index = '', $xss_clean = FALSE)
	{
		if ( ! isset($array[$index]))
		{
			return FALSE;
		}

		if ($xss_clean === TRUE)
		{
			return $this->security->xss_clean($array[$index]);
		}

		return $array[$index];
	}
</pre>

        <div class='alert alert-success'>
            整個Input類別的一大重點。<br/>
            在CI中，要取得使用者輸入值，都是$this->input->get或是$this->input->post之類的。<br/>
            這些函式基本上都是去呼叫這個_fetch_from_array函式，允許你將$_GET、$_POST變數經由xss_clean處理之後回傳。<br/>
            注意：xss_clean函數做的檢查非常多，主要是防止<a href='https://www.owasp.org/index.php/XSS_Filter_Evasion_Cheat_Sheet'>這份列表</a>上的攻擊行為。
        </div>

        <!-- You also need to add some content to highlight, but that is covered elsewhere. -->
        <pre class="brush: php">


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

	/**
	* Fetch an item from the GET array
	*
	* @access	public
	* @param	string
	* @param	bool
	* @return	string
	*/
	function get($index = NULL, $xss_clean = FALSE)
	{
		// Check if a field has been provided
		if ($index === NULL AND ! empty($_GET))
		{
			$get = array();

			// loop through the full _GET array
			foreach (array_keys($_GET) as $key)
			{
				$get[$key] = $this->_fetch_from_array($_GET, $key, $xss_clean);
			}
			return $get;
		}

		return $this->_fetch_from_array($_GET, $index, $xss_clean);
	}

</pre>

        <div class='alert alert-success'>
            與直接使用$_GET的唯一不同，在於第二個參數傳入TRUE可以進行xss過濾。
        </div>

        <!-- You also need to add some content to highlight, but that is covered elsewhere. -->
        <pre class="brush: php">


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

	/**
	* Fetch an item from the POST array
	*
	* @access	public
	* @param	string
	* @param	bool
	* @return	string
	*/
	function post($index = NULL, $xss_clean = FALSE)
	{
		// Check if a field has been provided
		if ($index === NULL AND ! empty($_POST))
		{
			$post = array();

			// Loop through the full _POST array and return it
			foreach (array_keys($_POST) as $key)
			{
				$post[$key] = $this->_fetch_from_array($_POST, $key, $xss_clean);
			}
			return $post;
		}

		return $this->_fetch_from_array($_POST, $index, $xss_clean);
	}

</pre>

        <div class='alert alert-success'>
            與直接使用$_POST的唯一不同，在於第二個參數傳入TRUE可以進行xss過濾。
        </div>

        <!-- You also need to add some content to highlight, but that is covered elsewhere. -->
        <pre class="brush: php">


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

	/**
	* Fetch an item from either the GET array or the POST
	*
	* @access	public
	* @param	string	The index key
	* @param	bool	XSS cleaning
	* @return	string
	*/
	function get_post($index = '', $xss_clean = FALSE)
	{
		if ( ! isset($_POST[$index]) )
		{
			return $this->get($index, $xss_clean);
		}
		else
		{
			return $this->post($index, $xss_clean);
		}
	}

</pre>

        <div class='alert alert-success'>
            PHP內建的$_REQUEST變數讓懶人可以直接拿$_GET, $_POST, $_COOKIE變數的值。<br/>
            這個函數怎麼不連$_COOKIE的值一起抓？不是很懶？囧。

        </div>

        <!-- You also need to add some content to highlight, but that is covered elsewhere. -->
        <pre class="brush: php">


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

	/**
	* Fetch an item from the COOKIE array
	*
	* @access	public
	* @param	string
	* @param	bool
	* @return	string
	*/
	function cookie($index = '', $xss_clean = FALSE)
	{
		return $this->_fetch_from_array($_COOKIE, $index, $xss_clean);
	}

</pre>

        <div class='alert alert-success'>
            與直接使用$_COOKIE的唯一不同，在於第二個參數傳入TRUE可以進行xss過濾。
        </div>

        <!-- You also need to add some content to highlight, but that is covered elsewhere. -->
        <pre class="brush: php">


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

	/**
	* Set cookie
	*
	* Accepts six parameter, or you can submit an associative
	* array in the first parameter containing all the values.
	*
	* @access	public
	* @param	mixed
	* @param	string	the value of the cookie
	* @param	string	the number of seconds until expiration
	* @param	string	the cookie domain.  Usually:  .yourdomain.com
	* @param	string	the cookie path
	* @param	string	the cookie prefix
	* @param	bool	true makes the cookie secure
	* @return	void
	*/
	function set_cookie($name = '', $value = '', $expire = '', $domain = '', $path = '/', $prefix = '', $secure = FALSE)
	{
		if (is_array($name))
		{
			// always leave 'name' in last place, as the loop will break otherwise, due to $$item
			foreach (array('value', 'expire', 'domain', 'path', 'prefix', 'secure', 'name') as $item)
			{
				if (isset($name[$item]))
				{
					$$item = $name[$item];
				}
			}
		}

		if ($prefix == '' AND config_item('cookie_prefix') != '')
		{
			$prefix = config_item('cookie_prefix');
		}
		if ($domain == '' AND config_item('cookie_domain') != '')
		{
			$domain = config_item('cookie_domain');
		}
		if ($path == '/' AND config_item('cookie_path') != '/')
		{
			$path = config_item('cookie_path');
		}
		if ($secure == FALSE AND config_item('cookie_secure') != FALSE)
		{
			$secure = config_item('cookie_secure');
		}

		if ( ! is_numeric($expire))
		{
			$expire = time() - 86500;
		}
		else
		{
			$expire = ($expire > 0) ? time() + $expire : 0;
		}

		setcookie($prefix.$name, $value, $expire, $path, $domain, $secure);
	}

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

	/**
	* Fetch an item from the SERVER array
	*
	* @access	public
	* @param	string
	* @param	bool
	* @return	string
	*/
	function server($index = '', $xss_clean = FALSE)
	{
		return $this->_fetch_from_array($_SERVER, $index, $xss_clean);
	}
</pre>

        <div class='alert alert-success'>
            $_SERVER變數一樣用_fetch_from_array包過一次，主要好處是它們會確認並檢視這些項目是否已被設定並且在未設定時回傳 false。<br/>
            這讓你可以方便地使用資料而不必預先測試它們是否存在。
        </div>
        <div class='alert alert-danger'>
            $_SERVER變數的值都是伺服器產生、與使用者無關。所以完全不需要xss過濾。<br/>
            雖然用_fetch_from_array包過，但$xss_clean參數其實沒意義。
        </div>

        <!-- You also need to add some content to highlight, but that is covered elsewhere. -->
        <pre class="brush: php">


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

	/**
	* Fetch the IP Address
	*
	* @return	string
	*/
	public function ip_address()
	{
		if ($this->ip_address !== FALSE)
		{
			return $this->ip_address;
		}

		$proxy_ips = config_item('proxy_ips');
		if ( ! empty($proxy_ips))
		{
			$proxy_ips = explode(',', str_replace(' ', '', $proxy_ips));
			foreach (array('HTTP_X_FORWARDED_FOR', 'HTTP_CLIENT_IP', 'HTTP_X_CLIENT_IP', 'HTTP_X_CLUSTER_CLIENT_IP') as $header)
			{
				if (($spoof = $this->server($header)) !== FALSE)
				{
					// Some proxies typically list the whole chain of IP
					// addresses through which the client has reached us.
					// e.g. client_ip, proxy_ip1, proxy_ip2, etc.
					if (strpos($spoof, ',') !== FALSE)
					{
						$spoof = explode(',', $spoof, 2);
						$spoof = $spoof[0];
					}

					if ( ! $this->valid_ip($spoof))
					{
						$spoof = FALSE;
					}
					else
					{
						break;
					}
				}
			}

			$this->ip_address = ($spoof !== FALSE && in_array($_SERVER['REMOTE_ADDR'], $proxy_ips, TRUE))
				? $spoof : $_SERVER['REMOTE_ADDR'];
		}
		else
		{
			$this->ip_address = $_SERVER['REMOTE_ADDR'];
		}

		if ( ! $this->valid_ip($this->ip_address))
		{
			$this->ip_address = '0.0.0.0';
		}

		return $this->ip_address;
	}

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

	/**
	* Validate IP Address
	*
	* @access	public
	* @param	string
	* @param	string	ipv4 or ipv6
	* @return	bool
	*/
	public function valid_ip($ip, $which = '')
	{
		$which = strtolower($which);

		// First check if filter_var is available
		if (is_callable('filter_var'))
		{
			switch ($which) {
				case 'ipv4':
					$flag = FILTER_FLAG_IPV4;
					break;
				case 'ipv6':
					$flag = FILTER_FLAG_IPV6;
					break;
				default:
					$flag = '';
					break;
			}

			return (bool) filter_var($ip, FILTER_VALIDATE_IP, $flag);
		}

		if ($which !== 'ipv6' && $which !== 'ipv4')
		{
			if (strpos($ip, ':') !== FALSE)
			{
				$which = 'ipv6';
			}
			elseif (strpos($ip, '.') !== FALSE)
			{
				$which = 'ipv4';
			}
			else
			{
				return FALSE;
			}
		}

		$func = '_valid_'.$which;
		return $this->$func($ip);
	}

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

	/**
	* Validate IPv4 Address
	*
	* Updated version suggested by Geert De Deckere
	*
	* @access	protected
	* @param	string
	* @return	bool
	*/
	protected function _valid_ipv4($ip)
	{
		$ip_segments = explode('.', $ip);

		// Always 4 segments needed
		if (count($ip_segments) !== 4)
		{
			return FALSE;
		}
		// IP can not start with 0
		if ($ip_segments[0][0] == '0')
		{
			return FALSE;
		}

		// Check each segment
		foreach ($ip_segments as $segment)
		{
			// IP segments must be digits and can not be
			// longer than 3 digits or greater then 255
			if ($segment == '' OR preg_match("/[^0-9]/", $segment) OR $segment > 255 OR strlen($segment) > 3)
			{
				return FALSE;
			}
		}

		return TRUE;
	}

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

	/**
	* Validate IPv6 Address
	*
	* @access	protected
	* @param	string
	* @return	bool
	*/
	protected function _valid_ipv6($str)
	{
		// 8 groups, separated by :
		// 0-ffff per group
		// one set of consecutive 0 groups can be collapsed to ::

		$groups = 8;
		$collapsed = FALSE;

		$chunks = array_filter(
			preg_split('/(:{1,2})/', $str, NULL, PREG_SPLIT_DELIM_CAPTURE)
		);

		// Rule out easy nonsense
		if (current($chunks) == ':' OR end($chunks) == ':')
		{
			return FALSE;
		}

		// PHP supports IPv4-mapped IPv6 addresses, so we'll expect those as well
		if (strpos(end($chunks), '.') !== FALSE)
		{
			$ipv4 = array_pop($chunks);

			if ( ! $this->_valid_ipv4($ipv4))
			{
				return FALSE;
			}

			$groups--;
		}

		while ($seg = array_pop($chunks))
		{
			if ($seg[0] == ':')
			{
				if (--$groups == 0)
				{
					return FALSE;	// too many groups
				}

				if (strlen($seg) > 2)
				{
					return FALSE;	// long separator
				}

				if ($seg == '::')
				{
					if ($collapsed)
					{
						return FALSE;	// multiple collapsed
					}

					$collapsed = TRUE;
				}
			}
			elseif (preg_match("/[^0-9a-f]/i", $seg) OR strlen($seg) > 4)
			{
				return FALSE; // invalid segment
			}
		}

		return $collapsed OR $groups == 1;
	}

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

	/**
	* User Agent
	*
	* @access	public
	* @return	string
	*/
	function user_agent()
	{
		if ($this->user_agent !== FALSE)
		{
			return $this->user_agent;
		}

		$this->user_agent = ( ! isset($_SERVER['HTTP_USER_AGENT'])) ? FALSE : $_SERVER['HTTP_USER_AGENT'];

		return $this->user_agent;
	}

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

	/**
	* Sanitize Globals
	*
	* This function does the following:
	*
	* Unsets $_GET data (if query strings are not enabled)
	*
	* Unsets all globals if register_globals is enabled
	*
	* Standardizes newline characters to \n
	*
	* @access	private
	* @return	void
	*/
	function _sanitize_globals()
	{
		// It would be "wrong" to unset any of these GLOBALS.
		$protected = array('_SERVER', '_GET', '_POST', '_FILES', '_REQUEST',
							'_SESSION', '_ENV', 'GLOBALS', 'HTTP_RAW_POST_DATA',
							'system_folder', 'application_folder', 'BM', 'EXT',
							'CFG', 'URI', 'RTR', 'OUT', 'IN');

		// Unset globals for securiy.
		// This is effectively the same as register_globals = off
		foreach (array($_GET, $_POST, $_COOKIE) as $global)
		{
			if ( ! is_array($global))
			{
				if ( ! in_array($global, $protected))
				{
					global $$global;
					$$global = NULL;
				}
			}
			else
			{
				foreach ($global as $key => $val)
				{
					if ( ! in_array($key, $protected))
					{
						global $$key;
						$$key = NULL;
					}
				}
			}
		}

		// Is $_GET data allowed? If not we'll set the $_GET to an empty array
		if ($this->_allow_get_array == FALSE)
		{
			$_GET = array();
		}
		else
		{
			if (is_array($_GET) AND count($_GET) > 0)
			{
				foreach ($_GET as $key => $val)
				{
					$_GET[$this->_clean_input_keys($key)] = $this->_clean_input_data($val);
				}
			}
		}

		// Clean $_POST Data
		if (is_array($_POST) AND count($_POST) > 0)
		{
			foreach ($_POST as $key => $val)
			{
				$_POST[$this->_clean_input_keys($key)] = $this->_clean_input_data($val);
			}
		}

		// Clean $_COOKIE Data
		if (is_array($_COOKIE) AND count($_COOKIE) > 0)
		{
			// Also get rid of specially treated cookies that might be set by a server
			// or silly application, that are of no use to a CI application anyway
			// but that when present will trip our 'Disallowed Key Characters' alarm
			// https://www.ietf.org/rfc/rfc2109.txt
			// note that the key names below are single quoted strings, and are not PHP variables
			unset($_COOKIE['$Version']);
			unset($_COOKIE['$Path']);
			unset($_COOKIE['$Domain']);

			foreach ($_COOKIE as $key => $val)
			{
				$_COOKIE[$this->_clean_input_keys($key)] = $this->_clean_input_data($val);
			}
		}

		// Sanitize PHP_SELF
		$_SERVER['PHP_SELF'] = strip_tags($_SERVER['PHP_SELF']);


		// CSRF Protection check on HTTP requests
		if ($this->_enable_csrf == TRUE && ! $this->is_cli_request())
		{
			$this->security->csrf_verify();
		}

		log_message('debug', "Global POST and COOKIE data sanitized");
	}

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

	/**
	* Clean Input Data
	*
	* This is a helper function. It escapes data and
	* standardizes newline characters to \n
	*
	* @access	private
	* @param	string
	* @return	string
	*/
	function _clean_input_data($str)
	{
		if (is_array($str))
		{
			$new_array = array();
			foreach ($str as $key => $val)
			{
				$new_array[$this->_clean_input_keys($key)] = $this->_clean_input_data($val);
			}
			return $new_array;
		}

		/* We strip slashes if magic quotes is on to keep things consistent

		   NOTE: In PHP 5.4 get_magic_quotes_gpc() will always return 0 and
			 it will probably not exist in future versions at all.
		*/
		if ( ! is_php('5.4') && get_magic_quotes_gpc())
		{
			$str = stripslashes($str);
		}

		// Clean UTF-8 if supported
		if (UTF8_ENABLED === TRUE)
		{
			$str = $this->uni->clean_string($str);
		}

		// Remove control characters
		$str = remove_invisible_characters($str);

		// Should we filter the input data?
		if ($this->_enable_xss === TRUE)
		{
			$str = $this->security->xss_clean($str);
		}

		// Standardize newlines if needed
		if ($this->_standardize_newlines == TRUE)
		{
			if (strpos($str, "\r") !== FALSE)
			{
				$str = str_replace(array("\r\n", "\r", "\r\n\n"), PHP_EOL, $str);
			}
		}

		return $str;
	}

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

	/**
	* Clean Keys
	*
	* This is a helper function. To prevent malicious users
	* from trying to exploit keys we make sure that keys are
	* only named with alpha-numeric text and a few other items.
	*
	* @access	private
	* @param	string
	* @return	string
	*/
	function _clean_input_keys($str)
	{
		if ( ! preg_match("/^[a-z0-9:_\/-]+$/i", $str))
		{
			exit('Disallowed Key Characters.');
		}

		// Clean UTF-8 if supported
		if (UTF8_ENABLED === TRUE)
		{
			$str = $this->uni->clean_string($str);
		}

		return $str;
	}

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

	/**
	 * Request Headers
	 *
	 * In Apache, you can simply call apache_request_headers(), however for
	 * people running other webservers the function is undefined.
	 *
	 * @param	bool XSS cleaning
	 *
	 * @return array
	 */
	public function request_headers($xss_clean = FALSE)
	{
		// Look at Apache go!
		if (function_exists('apache_request_headers'))
		{
			$headers = apache_request_headers();
		}
		else
		{
			$headers['Content-Type'] = (isset($_SERVER['CONTENT_TYPE'])) ? $_SERVER['CONTENT_TYPE'] : @getenv('CONTENT_TYPE');

			foreach ($_SERVER as $key => $val)
			{
				if (strncmp($key, 'HTTP_', 5) === 0)
				{
					$headers[substr($key, 5)] = $this->_fetch_from_array($_SERVER, $key, $xss_clean);
				}
			}
		}

		// take SOME_HEADER and turn it into Some-Header
		foreach ($headers as $key => $val)
		{
			$key = str_replace('_', ' ', strtolower($key));
			$key = str_replace(' ', '-', ucwords($key));

			$this->headers[$key] = $val;
		}

		return $this->headers;
	}

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

	/**
	 * Get Request Header
	 *
	 * Returns the value of a single member of the headers class member
	 *
	 * @param 	string		array key for $this->headers
	 * @param	boolean		XSS Clean or not
	 * @return 	mixed		FALSE on failure, string on success
	 */
	public function get_request_header($index, $xss_clean = FALSE)
	{
		if (empty($this->headers))
		{
			$this->request_headers();
		}

		if ( ! isset($this->headers[$index]))
		{
			return FALSE;
		}

		if ($xss_clean === TRUE)
		{
			return $this->security->xss_clean($this->headers[$index]);
		}

		return $this->headers[$index];
	}

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

	/**
	 * Is ajax Request?
	 *
	 * Test to see if a request contains the HTTP_X_REQUESTED_WITH header
	 *
	 * @return 	boolean
	 */
	public function is_ajax_request()
	{
		return ($this->server('HTTP_X_REQUESTED_WITH') === 'XMLHttpRequest');
	}

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

	/**
	 * Is cli Request?
	 *
	 * Test to see if a request was made from the command line
	 *
	 * @return 	bool
	 */
	public function is_cli_request()
	{
		return (php_sapi_name() === 'cli' OR defined('STDIN'));
	}

}

/* End of file Input.php */
/* Location: ./system/core/Input.php */
          
          </pre>

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