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：
复制代码代码如下:
$config["csrf_protection"] = TRUE;
$config["global_xss_filtering"] = TRUE;

并提供了实用方法：
复制代码代码如下:
$this->security->xss_clean（$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
复制代码代码如下:
<?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（
  "javascripts*:",
  "expressions*（（|(）", // CSS and IE
  "vbscripts*:", // IE, surprise！
  "Redirects+302",
  "（[""]）?datas*:[^\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, " "）！== FALSE）
  {
   $str = str_replace（" ", " ", $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））
   {
    $str = preg_replace_callback（"#<as+（[^>]*?）（>|$）#si", array（$this, "_js_link_removal"）, $str）;
   }
   if （preg_match（"/<img/i", $str））
   {
    $str = preg_replace_callback（"#<imgs+（[^>]*?）（s?/?>|$）#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
  $evil_attributes = array（"onw*", "style", "xmlns", "formaction"）;
  if （$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*（42|47）（[^\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(|javascript:|livescript:|mocha:|charset=|window.|document.|.cookie|<script|<xss|datas*:）#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(|javascript:|livescript:|mocha:|charset=|window.|document.|.cookie|<script|<xss|base64s*,）#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*（42|47）（[^\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;
}
}