<?php
/**
* Security class
*
* Note: adapted for RosarioSIS.
* - Renamed to Security.
* - CSRF code removed.
* - Constructor $charset param optional.
* - Allow evil 'style' attribute for TinyMCE.
* - Add static self::remove_invisible_characters() function.
*
* MarkDown input sanitize:
* @example $_REQUEST['values']['textarea'] = DBEscapeString( SanitizeMarkDown( $_POST['values']['textarea'] ) );
*
* @since 2.9
* @since 7.6.1 Fix #307 XSS update CodeIgniter Security class.
*
* @package CodeIgniter 3.1.11
* @subpackage Libraries
* @category Security
* @author EllisLab Dev Team
* @link https://codeigniter.com/userguide3/libraries/security.html
*/
class Security {
/**
* List of sanitize filename strings
*
* @var array
*/
public $filename_bad_chars = array(
'../', '<!--', '-->', '<', '>',
"'", '"', '&', '$', '#',
'{', '}', '[', ']', '=',
';', '?', '%20', '%22',
'%3c', // <
'%253c', // <
'%3e', // >
'%0e', // >
'%28', // (
'%29', // )
'%2528', // (
'%26', // &
'%24', // $
'%3f', // ?
'%3b', // ;
'%3d' // =
);
/**
* Character set
*
* Will be overridden by the constructor.
*
* @var string
*/
public $charset = 'UTF-8';
/**
* XSS Hash
*
* Random Hash for protecting URLs.
*
* @var string
*/
protected $_xss_hash;
/**
* List of never allowed strings
*
* @var array
*/
protected $_never_allowed_str = array(
'document.cookie' => '[removed]',
'(document).cookie' => '[removed]',
'document.write' => '[removed]',
'(document).write' => '[removed]',
'.parentNode' => '[removed]',
'.innerHTML' => '[removed]',
'-moz-binding' => '[removed]',
'<!--' => '<!--',
'-->' => '-->',
'<![CDATA[' => '<![CDATA[',
'<comment>' => '<comment>',
'<%' => '<%'
);
/**
* List of never allowed regex replacements
*
* @var array
*/
protected $_never_allowed_regex = array(
'javascript\s*:',
'(\(?document\)?|\(?window\)?(\.document)?)\.(location|on\w*)',
'expression\s*(\(|&\#40;)', // CSS and IE
'vbscript\s*:', // IE, surprise!
'wscript\s*:', // IE
'jscript\s*:', // IE
'vbs\s*:', // IE
'Redirect\s+30\d',
"([\"'])?data\s*:[^\\1]*?base64[^\\1]*?,[^\\1]*?\\1?"
);
/**
* Class constructor
*
* @return void
*/
public function __construct($charset = NULL)
{
if ( $charset )
{
$this->charset = $charset;
}
}
// --------------------------------------------------------------------
/**
* XSS Clean
*
* Sanitizes data so that Cross Site Scripting Hacks can be
* prevented. This method 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: Should only be used to deal with data upon submission.
* It's not something that should be used for general
* runtime processing.
*
* @link http://channel.bitflux.ch/wiki/XSS_Prevention
* Based in part on some code and ideas from Bitflux.
*
* @link http://ha.ckers.org/xss.html
* 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.
*
* @param string|string[] $str Input data
* @param bool $is_image Whether the input is an image
* @return string
*/
public function xss_clean($str, $is_image = FALSE)
{
// Is the string an array?
if (is_array($str))
{
foreach ($str as $key => &$value)
{
$str[$key] = $this->xss_clean($value);
}
return $str;
}
// Remove Invisible Characters
$str = self::remove_invisible_characters($str);
/*
* URL Decode
*
* 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
*/
if (stripos($str, '%') !== false)
{
do
{
$oldstr = $str;
$str = rawurldecode($str);
// FJ fix SQL error invalid byte sequence for encoding "UTF8": 0xde 0x20.
// @link https://www.php.net/manual/en/function.rawurldecode.php#114205
// @link https://github.com/bcit-ci/CodeIgniter/issues/5125#issuecomment-1119494853
// Regex fix: check *number* first, then number or letter a-f.
// $str = preg_replace_callback('#%(?:\s*[0-9a-f]){2,}#i', array($this, '_urldecodespaces'), $str);
$str = preg_replace_callback('#%(?:\s*[0-9]\s*[0-9a-f])#i', array($this, '_urldecodespaces'), $str);
}
while ($oldstr !== $str);
unset($oldstr);
}
/*
* 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.
*/
$str = preg_replace_callback("/[^a-z0-9>]+[a-z0-9]+=([\'\"]).*?\\1/si", array($this, '_convert_attribute'), $str);
$str = preg_replace_callback('/<\w+.*/si', array($this, '_decode_entity'), $str);
// Remove Invisible Characters Again!
$str = self::remove_invisible_characters($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.
*/
$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.
*/
$words = array(
'javascript', 'expression', 'vbscript', 'jscript', 'wscript',
'vbs', 'script', 'base64', 'applet', 'alert', 'document',
'write', 'cookie', 'window', 'confirm', 'prompt', 'eval'
);
foreach ($words as $word)
{
$word = implode('\s*', str_split($word)).'\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"
$str = preg_replace_callback('#('.substr($word, 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(),
* but it is dog slow compared to these simplified non-capturing
* preg_match(), especially if the pattern exists in the string
*
* Note: It was reported that not only space characters, but all in
* the following pattern can be parsed as separators between a tag name
* and its attributes: [\d\s"\'`;,\/\=\(\x00\x0B\x09\x0C]
* ... however, self::remove_invisible_characters() above already strips the
* hex-encoded ones, so we'll skip them below.
*/
do
{
$original = $str;
if (preg_match('/<a/i', $str))
{
$str = preg_replace_callback('#<a(?:rea)?[^a-z0-9>]+([^>]*?)(?:>|$)#si', array($this, '_js_link_removal'), $str);
}
if (preg_match('/<img/i', $str))
{
$str = preg_replace_callback('#<img[^a-z0-9]+([^>]*?)(?:\s?/?>|$)#si', array($this, '_js_img_removal'), $str);
}
if (preg_match('/script|xss/i', $str))
{
$str = preg_replace('#</*(?:script|xss).*?>#si', '[removed]', $str);
}
}
while ($original !== $str);
unset($original);
/*
* 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>
*/
$pattern = '#'
.'<((?<slash>/*\s*)((?<tagName>[a-z0-9]+)(?=[^a-z0-9]|$)|.+)' // tag start and name, followed by a non-tag character
.'[^\s\042\047a-z0-9>/=]*' // a valid attribute character immediately after the tag would count as a separator
// optional attributes
.'(?<attributes>(?:[\s\042\047/=]*' // non-attribute characters, excluding > (tag close) for obvious reasons
.'[^\s\042\047>/=]+' // attribute characters
// optional attribute-value
.'(?:\s*=' // attribute-value separator
.'(?:[^\s\042\047=><`]+|\s*\042[^\042]*\042|\s*\047[^\047]*\047|\s*(?U:[^\s\042\047=><`]*))' // single, double or non-quoted value
.')?' // end optional attribute-value group
.')*)' // end optional attributes group
.'[^>]*)(?<closeTag>\>)?#isS';
// Note: It would be nice to optimize this for speed, BUT
// only matching the naughty elements here results in
// false positives and in turn - vulnerabilities!
do
{
$old_str = $str;
$str = preg_replace_callback($pattern, array($this, '_sanitize_naughty_html'), $str);
}
while ($old_str !== $str);
unset($old_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|prompt|confirm|cmd|passthru|eval|exec|expression|system|fopen|fsockopen|file|file_get_contents|readfile|unlink)(\s*)\((.*?)\)#si',
'\\1\\2(\\3)',
$str
);
// Same thing, but for "tag functions" (e.g. eval`some code`)
// See https://github.com/bcit-ci/CodeIgniter/issues/5420
$str = preg_replace(
'#(alert|prompt|confirm|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);
}
return $str;
}
// --------------------------------------------------------------------
/**
* XSS Hash
*
* Generates the XSS hash if needed and returns it.
*
* @see CI_Security::$_xss_hash
* @return string XSS hash
*/
public function xss_hash()
{
if ($this->_xss_hash === NULL)
{
$rand = $this->get_random_bytes(16);
$this->_xss_hash = ($rand === FALSE)
? md5(uniqid(mt_rand(), TRUE))
: bin2hex($rand);
}
return $this->_xss_hash;
}
// --------------------------------------------------------------------
/**
* Get random bytes
*
* @param int $length Output length
* @return string
*/
public function get_random_bytes($length)
{
if (empty($length) OR ! ctype_digit((string) $length))
{
return FALSE;
}
if (function_exists('random_bytes'))
{
try
{
// The cast is required to avoid TypeError
return random_bytes((int) $length);
}
catch (Exception $e)
{
// If random_bytes() can't do the job, we can't either ...
// There's no point in using fallbacks.
log_message('error', $e->getMessage());
return FALSE;
}
}
// Unfortunately, none of the following PRNGs is guaranteed to exist ...
if (defined('MCRYPT_DEV_URANDOM') && ($output = mcrypt_create_iv($length, MCRYPT_DEV_URANDOM)) !== FALSE)
{
return $output;
}
if (is_readable('/dev/urandom') && ($fp = fopen('/dev/urandom', 'rb')) !== FALSE)
{
// Try not to waste entropy ...
stream_set_chunk_size($fp, $length);
$output = fread($fp, $length);
fclose($fp);
if ($output !== FALSE)
{
return $output;
}
}
if (function_exists('openssl_random_pseudo_bytes'))
{
return openssl_random_pseudo_bytes($length);
}
return FALSE;
}
// --------------------------------------------------------------------
/**
* HTML Entities Decode
*
* A replacement for html_entity_decode()
*
* The reason we are not using html_entity_decode() by itself is because
* while it is not technically correct to leave out the semicolon
* at the end of an entity most browsers will still interpret the entity
* correctly. html_entity_decode() does not convert entities without
* semicolons, so we are left with our own little solution here. Bummer.
*
* @link https://secure.php.net/html-entity-decode
*
* @param string $str Input
* @param string $charset Character set
* @return string
*/
public function entity_decode($str, $charset = NULL)
{
if (strpos($str, '&') === FALSE)
{
return $str;
}
static $_entities;
isset($charset) OR $charset = $this->charset;
isset($_entities) OR $_entities = array_map('strtolower', get_html_translation_table(HTML_ENTITIES, ENT_COMPAT | ENT_HTML5, $charset));
do
{
$str_compare = $str;
// Decode standard entities, avoiding false positives
if (preg_match_all('/&[a-z]{2,}(?![a-z;])/i', $str, $matches))
{
$replace = array();
$matches = array_unique(array_map('strtolower', $matches[0]));
foreach ($matches as &$match)
{
if (($char = array_search($match.';', $_entities, TRUE)) !== FALSE)
{
$replace[$match] = $char;
}
}
$str = str_replace(array_keys($replace), array_values($replace), $str);
}
// Decode numeric & UTF16 two byte entities
$str = html_entity_decode(
preg_replace('/(&#(?:x0*[0-9a-f]{2,5}(?![0-9a-f;])|(?:0*\d{2,4}(?![0-9;]))))/iS', '$1;', $str),
ENT_COMPAT | ENT_HTML5,
$charset
);
}
while ($str_compare !== $str);
return $str;
}
// --------------------------------------------------------------------
/**
* Sanitize Filename
*
* @param string $str Input file name
* @param bool $relative_path Whether to preserve paths
* @return string
*/
public function sanitize_filename($str, $relative_path = FALSE)
{
$bad = $this->filename_bad_chars;
if ( ! $relative_path)
{
$bad[] = './';
$bad[] = '/';
}
$str = self::remove_invisible_characters($str, FALSE);
do
{
$old = $str;
$str = str_replace($bad, '', $str);
}
while ($old !== $str);
return stripslashes($str);
}
// ----------------------------------------------------------------
/**
* Strip Image Tags
*
* @param string $str
* @return string
*/
public function strip_image_tags($str)
{
return preg_replace(
array(
'#<img[\s/]+.*?src\s*=\s*(["\'])([^\\1]+?)\\1.*?\>#i',
'#<img[\s/]+.*?src\s*=\s*?(([^\s"\'=<>`]+)).*?\>#i'
),
'\\2',
$str
);
}
// ----------------------------------------------------------------
/**
* URL-decode taking spaces into account
*
* @see https://github.com/bcit-ci/CodeIgniter/issues/4877
* @param array $matches
* @return string
*/
protected function _urldecodespaces($matches)
{
$input = $matches[0];
$nospaces = preg_replace('#\s+#', '', $input);
return ($nospaces === $input)
? $input
: rawurldecode($nospaces);
}
// ----------------------------------------------------------------
/**
* Compact Exploded Words
*
* Callback method for xss_clean() to remove whitespace from
* things like 'j a v a s c r i p t'.
*
* @used-by CI_Security::xss_clean()
* @param array $matches
* @return string
*/
protected function _compact_exploded_words($matches)
{
return preg_replace('/\s+/s', '', $matches[1]).$matches[2];
}
// --------------------------------------------------------------------
/**
* Sanitize Naughty HTML
*
* Callback method for xss_clean() to remove naughty HTML elements.
*
* @used-by CI_Security::xss_clean()
* @param array $matches
* @return string
*/
protected function _sanitize_naughty_html($matches)
{
static $naughty_tags = array(
'alert', 'area', 'prompt', 'confirm', 'applet', 'audio', 'basefont', 'base', 'behavior', 'bgsound',
'blink', 'body', 'embed', 'expression', 'form', 'frameset', 'frame', 'head', 'html', 'ilayer',
'iframe', 'input', 'button', 'select', 'isindex', 'layer', 'link', 'meta', 'keygen', 'object',
'plaintext', 'style', 'script', 'textarea', 'title', 'math', 'video', 'svg', 'xml', 'xss'
);
// FJ Allow evil 'style' attribute for TinyMCE.
// @link https://security.stackexchange.com/questions/60712/is-xss-through-style-attribute-possible-in-modern-browsers
/*static $evil_attributes = array(
'on\w+', 'style', 'xmlns', 'formaction', 'form', 'xlink:href', 'FSCommand', 'seekSegmentTime'
);*/
static $evil_attributes = array(
'on\w+', 'xmlns', 'formaction', 'form', 'xlink:href', 'FSCommand', 'seekSegmentTime'
);
// First, escape unclosed tags
if (empty($matches['closeTag']))
{
return '<'.$matches[1];
}
// Is the element that we caught naughty? If so, escape it
elseif (in_array(strtolower($matches['tagName']), $naughty_tags, TRUE))
{
return '<'.$matches[1].'>';
}
// For other tags, see if their attributes are "evil" and strip those
elseif (isset($matches['attributes']))
{
// We'll store the already filtered attributes here
$attributes = array();
// Attribute-catching pattern
$attributes_pattern = '#'
.'(?<name>[^\s\042\047>/=]+)' // attribute characters
// optional attribute-value
.'(?:\s*=(?<value>[^\s\042\047=><`]+|\s*\042[^\042]*\042|\s*\047[^\047]*\047|\s*(?U:[^\s\042\047=><`]*)))' // attribute-value separator
.'#i';
// Blacklist pattern for evil attribute names
$is_evil_pattern = '#^('.implode('|', $evil_attributes).')$#i';
// Each iteration filters a single attribute
do
{
// Strip any non-alpha characters that may precede an attribute.
// Browsers often parse these incorrectly and that has been a
// of numerous XSS issues we've had.
$matches['attributes'] = preg_replace('#^[^a-z]+#i', '', $matches['attributes']);
if ( ! preg_match($attributes_pattern, $matches['attributes'], $attribute, PREG_OFFSET_CAPTURE))
{
// No (valid) attribute found? Discard everything else inside the tag
break;
}
if (
// Is it indeed an "evil" attribute?
preg_match($is_evil_pattern, $attribute['name'][0])
// Or does it have an equals sign, but no value and not quoted? Strip that too!
OR (trim($attribute['value'][0]) === '')
)
{
$attributes[] = 'xss=removed';
}
else
{
$attributes[] = $attribute[0][0];
}
$matches['attributes'] = substr($matches['attributes'], $attribute[0][1] + strlen($attribute[0][0]));
}
while ($matches['attributes'] !== '');
$attributes = empty($attributes)
? ''
: ' '.implode(' ', $attributes);
return '<'.$matches['slash'].$matches['tagName'].$attributes.'>';
}
return $matches[0];
}
// --------------------------------------------------------------------
/**
* JS Link Removal
*
* Callback method for xss_clean() to sanitize links.
*
* This limits the PCRE backtracks, making it more performance friendly
* and prevents PREG_BACKTRACK_LIMIT_ERROR from being triggered in
* PHP 5.2+ on link-heavy strings.
*
* @used-by CI_Security::xss_clean()
* @param array $match
* @return string
*/
protected function _js_link_removal($match)
{
return str_replace(
$match[1],
preg_replace(
'#href=.*?(?:(?:alert|prompt|confirm)(?:\(|&\#40;|`|&\#96;)|javascript:|livescript:|mocha:|charset=|window\.|\(?document\)?\.|\.cookie|<script|<xss|d\s*a\s*t\s*a\s*:)#si',
'',
$this->_filter_attributes($match[1])
),
$match[0]
);
}
// --------------------------------------------------------------------
/**
* JS Image Removal
*
* Callback method for xss_clean() to sanitize image tags.
*
* This limits the PCRE backtracks, making it more performance friendly
* and prevents PREG_BACKTRACK_LIMIT_ERROR from being triggered in
* PHP 5.2+ on image tag heavy strings.
*
* @used-by CI_Security::xss_clean()
* @param array $match
* @return string
*/
protected function _js_img_removal($match)
{
return str_replace(
$match[1],
preg_replace(
'#src=.*?(?:(?:alert|prompt|confirm|eval)(?:\(|&\#40;|`|&\#96;)|javascript:|livescript:|mocha:|charset=|window\.|\(?document\)?\.|\.cookie|<script|<xss|base64\s*,)#si',
'',
$this->_filter_attributes($match[1])
),
$match[0]
);
}
// --------------------------------------------------------------------
/**
* Attribute Conversion
*
* @used-by CI_Security::xss_clean()
* @param array $match
* @return string
*/
protected function _convert_attribute($match)
{
return str_replace(array('>', '<', '\\'), array('>', '<', '\\\\'), $match[0]);
}
// --------------------------------------------------------------------
/**
* Filter Attributes
*
* Filters tag attributes for consistency and safety.
*
* @used-by CI_Security::_js_img_removal()
* @used-by CI_Security::_js_link_removal()
* @param string $str
* @return string
*/
protected function _filter_attributes($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 Entity Decode Callback
*
* @used-by CI_Security::xss_clean()
* @param array $match
* @return string
*/
protected function _decode_entity($match)
{
// Protect GET variables in URLs
// 901119URL5918AMP18930PROTECT8198
$match = preg_replace('|\&([a-z\_0-9\-]+)\=([a-z\_0-9\-/]+)|i', $this->xss_hash().'\\1=\\2', $match[0]);
// Decode, then un-protect URL GET vars
return str_replace(
$this->xss_hash(),
'&',
$this->entity_decode($match, $this->charset)
);
}
// --------------------------------------------------------------------
/**
* Do Never Allowed
*
* @used-by CI_Security::xss_clean()
* @param string
* @return string
*/
protected function _do_never_allowed($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 $str;
}
/**
* Remove Invisible Characters
*
* This prevents sandwiching null characters
* between ascii characters, like Java\0script.
*
* @access public
* @param string
* @return string
*/
protected static function remove_invisible_characters($str, $url_encoded = TRUE)
{
$non_displayables = array();
// every control character except newline (dec 10)
// carriage return (dec 13), and horizontal tab (dec 09)
if ($url_encoded)
{
$non_displayables[] = '/%0[0-8bcef]/'; // url encoded 00-08, 11, 12, 14, 15
$non_displayables[] = '/%1[0-9a-f]/'; // url encoded 16-31
}
$non_displayables[] = '/[\x00-\x08\x0B\x0C\x0E-\x1F\x7F]+/S'; // 00-08, 11, 12, 14-31, 127
do
{
$str = preg_replace($non_displayables, '', $str, -1, $count);
}
while ($count);
return $str;
}
}