CI framework security class Security.php source code analysis, cisecurity.php_PHP tutorial

CI framework security class Security.php source code analysis, cisecurity.php

The CI security class provides a global defense strategy against CSRF attacks and XSS attacks. You only need to enable it in the configuration file:

Copy code The code is as follows:

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

And provides practical methods:

Copy code The code is as follows:

$this->security->xss_clean($data);//The second parameter is TRUE to verify the security of the image
$this->security->sanitize_filename()//Filter file name

CI also provides security functions:

xss_clean()//xss filtering
sanitize_filename()//Sanitize file name
do_hash()//md5 or sha encryption
strip_image_tags() //Remove unnecessary characters of image tags
encode_php_tags()//Force PHP script tags into entity objects

Copy code The code is as follows:

/**
* Security category
​*/
class CI_Security {
//Random hash value of url
protected $_xss_hash = '';
//Hash value of cookie tag to prevent CSRF attacks
protected $_csrf_hash = '';
//Anti-csrf cookie expiration time
protected $_csrf_expire = 7200;
//Csrf-proof cookie name
protected $_csrf_token_name = 'ci_csrf_token';
//Anti-csrf token name
protected $_csrf_cookie_name = 'ci_csrf_token';
//Array of strings that are not allowed
protected $_never_allowed_str = array(
'document.cookie' => '[removed]',
'document.write' => '[removed]',
'.parentNode' => '[removed]',
'.innerHTML' => '[removed]',
'window.location' => '[removed]',
'-moz-binding' => '[removed]',
'' => '-->',
' ' '' => ''
);
//Array of regular expressions that are not allowed
protected $_never_allowed_regex = array(
'javascripts*:',
'expressions*((|()', // CSS and IE
'vbscripts*:', // IE, surprise!
'Redirects+302',
"(["'])?datas*:[^\1]*?base64[^\1]*?,[^\1]*?\1?"
);
//Constructor
public function __construct()
{
// Whether CSRF protection is enabled
if (config_item('csrf_protection') === TRUE)
{
// CSRF configuration
foreach (array('csrf_expire', 'csrf_token_name', 'csrf_cookie_name') as $key)
{
If (FALSE !== ($val = config_item($key)))
{
$this->{'_'.$key} = $val;
}
}
// _csrf_cookie_name plus cookie prefix
If (config_item('cookie_prefix'))
{
$this->_csrf_cookie_name = config_item('cookie_prefix').$this->_csrf_cookie_name;
}
//Set the hash value of csrf
$this->_csrf_set_hash();
}
log_message('debug', "Security Class Initialized");
}
//------------------------------------------------ ------------------
/**
  * Verify Cross Site Request Forgery Protection
  *
  * @return object
 */
public function csrf_verify()
{
// If it is not a post request, set the cookie value of csrf
if (strtoupper($_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]))
{
$this->csrf_show_error();
}
//Does the token match
if ($_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 the cookie value of csrf
​*/
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 $this->_csrf_token_name;
 }
 /**
* XSS filtering
​*/
 public function xss_clean($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:
   *
   * 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);
  $str = preg_replace_callback("/|<|$)/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:
   *
   *    *
   * 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('/   }
  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("/    {
    $str = preg_replace_callback("#]*?)(>|$)#si", array($this, '_js_link_removal'), $str);
   }
   if (preg_match("/    {
    $str = preg_replace_callback("#]*?)(s?/?>|$)#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:
   * 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';
  $str = preg_replace_callback('#<(/*s*)('.$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 $this->_xss_hash;
 }
 // --------------------------------------------------------------------
 /**
* html entity transcoding
​*/
 public function entity_decode($str, $charset='UTF-8')
 {
  if (stristr($str, '&') === FALSE)
  {
   return $str;
  }
  $str = html_entity_decode($str, ENT_COMPAT, $charset);
  $str = preg_replace('~(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
  $evil_attributes = array('onw*', 'style', 'xmlns', 'formaction');
  if ($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*(