CI框架安全类Security.php源码分析

之前我们分析了CI框架的session类session.php，本文我们继续分析CI框架的安全类security.php文件，方便我们更详细的了解CI框架，从而更熟练的应用CI框架

CI安全类提供了全局防御CSRF攻击和XSS攻击策略，只需要在配置文件开启即可：

$config['csrf_protection'] = TRUE;
$config['global_xss_filtering'] = TRUE;

并提供了实用方法：

$this->security->xss_clean($data);//第二个参数为TRUE，验证图片安全
$this->security->sanitize_filename()//过滤文件名

CI也提供了安全函数：

xss_clean()//xss过滤
sanitize_filename()//净化文件名
do_hash()//md5或sha加密
strip_image_tags() //删除图片标签的不必要字符
encode_php_tags()//把PHP脚本标签强制转成实体对象

<?php if ( ! defined('BASEPATH')) exit('No direct script access allowed');
/**
 * 安全类
 */
class CI_Security {
 //url的随机hash值
 protected $_xss_hash   = '';
 //防csrf攻击的cookie标记的哈希值  
 protected $_csrf_hash   = '';
 //防csrf cookie过期时间
 protected $_csrf_expire   = 7200;
 //防csrf的cookie名称
 protected $_csrf_token_name  = 'ci_csrf_token';
 //防csrf的token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数组
 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()
 {
  // CSRF保护是否开启
  if (config_item('csrf_protection') === TRUE)
  {
   // CSRF配置
   foreach (array('csrf_expire', 'csrf_token_name', 'csrf_cookie_name') as $key)
   {
    if (FALSE !== ($val = config_item($key)))
    {
     $this->{'_'.$key} = $val;
    }
   }
   // _csrf_cookie_name加上cookie前缀
   if (config_item('cookie_prefix'))
   {
    $this->_csrf_cookie_name = config_item('cookie_prefix').$this->_csrf_cookie_name;
   }
   // 设置csrf的hash值
   $this->_csrf_set_hash();
  }
  log_message('debug', "Security Class Initialized");
 }
 // --------------------------------------------------------------------
 /**
  * Verify Cross Site Request Forgery Protection
  *
  * @return object
  */
 public function csrf_verify()
 {
  // 如果不是post请求，则设置csrf的cookie值
  if (strtoupper($_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]))
  {
   $this->csrf_show_error();
  }
  // token匹配吗
  if ($_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csrf的cookie值
  */
 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;
 }
 //csrf保存
 public function csrf_show_error()
 {
  show_error('The action you have requested is not allowed.');
 }
 //获取csrf的hash值
 public function get_csrf_hash()
 {
  return $this->_csrf_hash;
 }
 //获取csrf的token值
 public function get_csrf_token_name()
 {
  return $this->_csrf_token_name;
 }
 /**
  * XSS 过滤
  */
 public function xss_clean($str, $is_image = FALSE)
 {
  //是否是数组
  if (is_array($str))
  {
   while (list($key) = each($str))
   {
    $str[$key] = $this->xss_clean($str[$key]);
   }
   return $str;
  }
  //去掉可见字符串
  $str = remove_invisible_characters($str);
  // 验证实体url
  $str = $this->_validate_entities($str);
  /*
   * URL 解码
   *
   * 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 $str;
 }
 // --------------------------------------------------------------------
 //保护url的随机hash值
 public function xss_hash()
 {
  if ($this->_xss_hash == '')
  {
   mt_srand();
   $this->_xss_hash = md5(time() + mt_rand(0, 1999999999));
  }
  return $this->_xss_hash;
 }
 // --------------------------------------------------------------------
 /**
  * html实体转码
  */
 public function entity_decode($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)', $str);
 }
 // --------------------------------------------------------------------
 //过滤文件名，保证文件名安全
 public function sanitize_filename($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, '', $str));
 }
 //压缩单词如j a v a s c r i p t成javascript
 protected function _compact_exploded_words($matches)
 {
  return preg_replace('/\s+/s', '', $matches[1]).$matches[2];
 }
 // --------------------------------------------------------------------
 /*
  * 去掉一些危害的html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 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], '/');
   }
   // 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], '/');
   }
   // 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$2 $4$6$7$8', $str, -1, $count);
   }
  } while ($count);
  return $str;
 }
 // --------------------------------------------------------------------
 /**
  * 净化html,补齐未关闭的标签
  */
 protected function _sanitize_naughty_html($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]))
   ),
   $match[0]
  );
 }
 // --------------------------------------------------------------------
 /**
  * 转换属性，将一些字符转换成实体
  */
 protected function _convert_attribute($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 $out;
 }
 // --------------------------------------------------------------------
 //html实体转码
 protected function _decode_entity($match)
 {
  return $this->entity_decode($match[0], strtoupper(config_item('charset')));
 }
 // --------------------------------------------------------------------
 /**
  * 验证url实体
  */
 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 $str;
 }
 // ----------------------------------------------------------------------
 //过滤不允许出现的字符串
 protected function _do_never_allowed($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 $str;
 }
 // --------------------------------------------------------------------
 //设置csrf的hash值
 protected function _csrf_set_hash()
 {
  if ($this->_csrf_hash == '')
  {
   // 如果_csrf_cookie_name存在，直接作为csrf hash值
   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];
   }
                        //否则随机一个md5字符串
   return $this->_csrf_hash = md5(uniqid(rand(), TRUE));
  }
  return $this->_csrf_hash;
 }
}