我們開始分析core/Security.php。
主要就是大量的字串處理。
/**
* 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
*
* @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
*
* @var string
* @access protected
*/
protected $_xss_hash = '';
/**
* Random Hash for Cross Site Request Forgery Protection Cookie
*
* @var string
* @access protected
*/
protected $_csrf_hash = '';
/**
* Expiration time for Cross Site Request Forgery Protection Cookie
* Defaults to two hours (in seconds)
*
* @var int
* @access protected
*/
protected $_csrf_expire = 7200;
/**
* Token name for Cross Site Request Forgery Protection Cookie
*
* @var string
* @access protected
*/
protected $_csrf_token_name = 'ci_csrf_token';
/**
* Cookie name for Cross Site Request Forgery Protection Cookie
*
* @var string
* @access protected
*/
protected $_csrf_cookie_name = 'ci_csrf_token';
/**
* List of never allowed strings
*
* @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]',
'' => '-->',
' '<![CDATA[',
'' => '<comment>'
);
/* never allowed, regex replacement */
/**
* List of never allowed regex replacement
*
* @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?
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
$this->_csrf_set_hash();
}
log_message('debug', "Security Class Initialized");
}
// --------------------------------------------------------------------
/**
* Verify Cross Site Request Forgery Protection
*
* @return object
*/
public function csrf_verify()
{
// If it's not a POST request we will set the CSRF cookie
if (strtoupper($_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;
}
// --------------------------------------------------------------------
/**
* Set Cross Site Request Forgery Protection Cookie
*
* @return object
*/
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;
}
// --------------------------------------------------------------------
/**
* Show CSRF Error
*
* @return void
*/
public function csrf_show_error()
{
show_error('The action you have requested is not allowed.');
}
將錯誤訊息包成一個函數。需要修改訊息內容可以統一修改。
// --------------------------------------------------------------------
/**
* Get CSRF Hash
*
* Getter Method
*
* @return string self::_csrf_hash
*/
public function get_csrf_hash()
{
return $this->_csrf_hash;
}
// --------------------------------------------------------------------
/**
* Get CSRF Token Name
*
* Getter Method
*
* @return string self::csrf_token_name
*/
public function get_csrf_token_name()
{
return $this->_csrf_token_name;
}
// --------------------------------------------------------------------
/**
* XSS Clean
*
* Sanitizes data so that Cross Site Scripting Hacks can be
* prevented. This function does a fair amount of work but
* it is extremely thorough, designed to prevent even the
* most obscure XSS attempts. Nothing is ever 100% foolproof,
* of course, but I haven't been able to get anything passed
* the filter.
*
* Note: This function should only be used to deal with data
* upon submission. It's not something that should
* be used for general runtime processing.
*
* This function was based in part on some code and ideas I
* got from Bitflux: http://channel.bitflux.ch/wiki/XSS_Prevention
*
* To help develop this script I used this great list of
* vulnerabilities along with a few other hacks I've
* harvested from examining vulnerabilities in other programs:
* http://ha.ckers.org/xss.html
*
* @param mixed string or array
* @param bool
* @return string
*/
public function xss_clean($str, $is_image = FALSE)
{
/*
* Is the string an array?
*
*/
if (is_array($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:
*
* Google
*
* 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:
*
* '), 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 = $str;
if (preg_match("/]*?)(>|$)#si", array($this, '_js_link_removal'), $str);
}
if (preg_match("/![]()
]*?)(\s?/?>|$)#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:
CSRF防禦所比對token的內容。只是用md5函數與rand函數產生的亂數。
同一個頁面可能有多個表單，所以若是token的cookie有被設定，並且token內容是一個長度32的16進位字串（那串[0-9a-f]{32}正規表示就是在檢查這個），則不再重新產生。
注意這個函數的重點在set而不是get，雖然有多個return敘述，但return的內容都是先設定再回傳。
查閱類別內呼叫這個函數的地方，都沒有使用變數紀錄函數的回傳值。
}
/* End of file Security.php */
/* Location: ./system/libraries/Security.php */