CI框架安全类Security.php源码分析

            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：
[U]复制代码[/U] 代码如下:
$config['csrf_protection'] = TRUE;
$config['global_xss_filtering'] = TRUE;
并提供了实用方法：
[U]复制代码[/U] 代码如下:
$this->security->xss_clean($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
[U]复制代码[/U] 代码如下:
'[removed]',
  'document.write' => '[removed]',
  '.parentNode'  => '[removed]',
  '.innerHTML'  => '[removed]',
  'window.location' => '[removed]',
  '-moz-binding'  => '[removed]',
  ' ''    => '-->',
  ' ''   => ''
);
//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:
   *
   * [url=http://%77%77%77%2E%67%6F%6F%67%6C%65%2E%63%6F%6D">GoogleGoogle
   *
   * 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);
  $str = preg_replace_callback("/|_do_never_allowed($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); $i ]*?)(>|$)#si", array($this, '_js_link_removal'), $str);
   }
   if (preg_match("/]*?)(\s?/?>|$)#si", array($this, '_js_'), $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
  $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:
   * Becomes:
   */
  $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 $str;
}
// --------------------------------------------------------------------
//保护url的随机hash值
public function xss_hash()
{
  if ($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("[url=file://\\1"))']\\1"))'[/url], $str);
  return preg_replace('~&([0-9]{2,4})~e', 'chr([url=file://\\1)']\\1)'[/url], $str);
}
// --------------------------------------------------------------------
//过滤文件名，保证文件名安全
public function sanitize_filename($str, $relative_path = FALSE)
{
  $bad = array(
   "../",
   "",
   "",
   "'",
   '"',
   '&',
   '$',
   '#',
   '{',
   '}',
   '[',
   ']',
   '=',
   ';',
   '?',
   "%20",
   "%22",
   "%3c",  //
   "%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]*?)([url=file://\\2)/is']\\2)/is'[/url], $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('/(\-])(.*?)('.implode('|', $attribs).')(.*?)([\s>', '', '_filter_attributes(str_replace(array(''), '', $match[1]))
   ),
   $match[0]
  );
}
// --------------------------------------------------------------------
/**
  * 过滤图片链接中的js
  */
protected function _js_($match)
{
  return str_replace(
   $match[1],
   preg_replace(
    '#src=.*?(alert\(|alert&\#40;|javascript\:|livescript\:|mocha\:|charset\=|window\.|document\.|\.cookie|_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('>', '', '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;
}
}
            
            
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