Security::_remove_evil_attributes() - Code Metrics - Inspection of "Add security helper" - Distilleries/Expendable - Measure and Improve Code Quality continuously with Scrutinizer

Completed
Push — master ( c8c0f9...82094b )

by Maxime
created 2016-07-04 12:02 UTC
Security::_remove_evil_attributes() B

↳ Parent: Security
Complexity

Conditions	4
Paths	4
Size

Total Lines	32
Code Lines	14
Duplication

Lines	0
Ratio	0 %
Code Coverage

Tests	0
CRAP Score	20
Importance

Changes	1
Bugs	0	Features	1
Metric	Value
c	1
b	0
f	1
dl	0
loc	32
ccs	0
cts	24
cp	0
rs	8.5806
cc	4
eloc	14
nc	4
nop	3
crap	20
<?php
/**
 * Created by PhpStorm.
 * User: mfrancois
 * Date: 04/07/2016
 * Time: 11:32
 */

namespace Distilleries\Expendable\Helpers;


class Security
{


    /**
     * Random Hash for protecting URLs
     *
     * @var string
     * @access protected
     */
    protected $_xss_hash			= '';

    /**
     * List of never allowed strings
     *
     * @var array
     * @access protected
     */
    protected $_never_allowed_str = array(
        'document.cookie'	=> '[removed]',
        'document.write'	=> '[removed]',
        '.parentNode'		=> '[removed]',
        '.innerHTML'		=> '[removed]',
        'window.location'	=> '[removed]',
        '-moz-binding'		=> '[removed]',
        '<!--'				=> '&lt;!--',
        '-->'				=> '--&gt;',
        '<![CDATA['			=> '&lt;![CDATA[',
        '<comment>'			=> '&lt;comment&gt;'
    );

    /* never allowed, regex replacement */
    /**
     * List of never allowed regex replacement
     *
     * @var array
     * @access protected
     */
    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?"
    );


    /**
     * XSS Clean
     *
     * Sanitizes data so that Cross Site Scripting Hacks can be
     * prevented.  This function 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: This function should only be used to deal with data
     * upon submission.  It's not something that should
     * be used for general runtime processing.
     *
     * This function was based in part on some code and ideas I
     * got from Bitflux: http://channel.bitflux.ch/wiki/XSS_Prevention
     *
     * 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:
     * http://ha.ckers.org/xss.html
     *
     * @param    mixed    string or array
     * @return    string
     */
    public function xss_clean($str, $is_image = FALSE, $evilAttribute = TRUE)
    {
        /*
           * Is the string an array?
           *
           */
        if (is_array($str))
        {
            while (list($key) = each($str))
            {
                $str[$key] = $this->xss_clean($str[$key], $is_image, $evilAttribute);
            }
            return $str;
        }

        /*
           * Remove Invisible Characters
           */
        $str = $this->remove_invisible_characters($str);

        // Validate Entities in URLs
        $str = $this->_validate_entities($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
           *
           */
        $str = rawurldecode($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 = $this->remove_invisible_characters($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', "&lt;?\\1", $str);
        }
        else
        {
            $str = str_replace(array('<?', '?' . '>'), array('&lt;?', '?&gt;'), $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',
            '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))
// Logical operators have lower precedence:
$f = false or true;

// is executed like this:
($f = false) or true;


// Boolean operators have higher precedence:
$f = false || true;

// is executed like this:
$f = (false || true);
            {
                $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, $evilAttribute);

        /*
           * 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: &lt;blink&gt;
           */
        $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&#40;'some code'&#41;
           */
        $str = preg_replace('#(alert|cmd|passthru|eval|exec|expression|system|fopen|fsockopen|file|file_get_contents|readfile|unlink)(\s*)\((.*?)\)#si', "\\1\\2&#40;\\3&#41;", $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;
        }

        return $str;
    }

    // --------------------------------------------------------------------

    /*
      * Remove Evil HTML Attributes (like evenhandlers and style)
      *
      * It removes the evil attribute and either:
      * 	- Everything up until a space
      *		For example, everything between the pipes:
      *		<a |style=document.write('hello');alert('world');| class=link>
      * 	- Everything inside the quotes
      *		For example, everything between the pipes:
      *		<a |style="document.write('hello'); alert('world');"| class="link">
      *
      * @param string $str The string to check
      * @param boolean $is_image TRUE if this is an image
      * @return string The string with the evil attributes removed
      */
    protected function _remove_evil_attributes($str, $is_image, $evilAttribute)
    {
        // All javascript event handlers (e.g. onload, onclick, onmouseover), style, and xmlns
        if ($evilAttribute)
        {
            $evil_attributes = array('on\w*', 'style', 'xmlns');
        }
        else
        {
            $evil_attributes = array('on\w*', 'xmlns');
        }

        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
        {
            $str = preg_replace(
                "#<(/?[^><]+?)([^A-Za-z\-])(" . implode('|', $evil_attributes) . ")(\s*=\s*)([\"][^>]*?[\"]|[\'][^>]*?[\']|[^>]*?)([\s><])([><]*)#i",
                "<$1$6",
                $str, -1, $count
            );
        } while ($count);
0   == false // true
0   == null  // true
123 == false // false
123 == null  // false

// It is often better to use strict comparison
0 === false // false
0 === null  // false

        return $str;
    }



    // --------------------------------------------------------------------

    /**
     * HTML Entities Decode
     *
     * This function is 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.
     *
     * @param	string
     * @param	string
     * @return	string
     */
    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);
    }

    // --------------------------------------------------------------------

    /**
     * Filename Security
     *
     * @param	string
     * @param 	bool
     * @return	string
     */
    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 = $this->remove_invisible_characters($str, FALSE);
        return stripslashes(str_replace($bad, '', $str));
    }

    // ----------------------------------------------------------------

    /**
     * Compact Exploded Words
     *
     * Callback function for xss_clean() to remove whitespace from
     * things like j a v a s c r i p t
     *
     * @param	type
     * @return	type
     */
    protected function _compact_exploded_words($matches)
    {
        return preg_replace('/\s+/s', '', $matches[1]).$matches[2];
    }

    // --------------------------------------------------------------------

    /**
     * Sanitize Naughty HTML
     *
     * Callback function for xss_clean() to remove naughty HTML elements
     *
     * @param	array
     * @return	string
     */
    protected function _sanitize_naughty_html($matches)
    {
        // encode opening brace
        $str = '&lt;'.$matches[1].$matches[2].$matches[3];

        // encode captured opening or closing brace to prevent recursive vectors
        $str .= str_replace(array('>', '<'), array('&gt;', '&lt;'),
            $matches[4]);

        return $str;
    }

    // --------------------------------------------------------------------

    /**
     * JS Link Removal
     *
     * Callback function 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
     *
     * @param	array
     * @return	string
     */
    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]
        );
    }

    // --------------------------------------------------------------------

    /**
     * JS Image Removal
     *
     * Callback function 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
     *
     * @param	array
     * @return	string
     */
    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]
        );
    }

    // --------------------------------------------------------------------

    /**
     * Attribute Conversion
     *
     * Used as a callback for XSS Clean
     *
     * @param	array
     * @return	string
     */
    protected function _convert_attribute($match)
    {
        return str_replace(array('>', '<', '\\'), array('&gt;', '&lt;', '\\\\'), $match[0]);
    }

    // --------------------------------------------------------------------

    /**
     * Filter Attributes
     *
     * Filters tag attributes for consistency and safety
     *
     * @param	string
     * @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 as a callback for XSS Clean
     *
     * @param	array
     * @return	string
     */
    protected function _decode_entity($match)
    {
        return $this->entity_decode($match[0], strtoupper(config_item('charset')));
    }

    // --------------------------------------------------------------------

    /**
     * Validate URL entities
     *
     * Called by xss_clean()
     *
     * @param 	string
     * @return 	string
     */
    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);


        return $str;
    }

    // ----------------------------------------------------------------------

    /**
     * Do Never Allowed
     *
     * A utility function for 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;
    }


    protected 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);
0   == false // true
0   == null  // true
123 == false // false
123 == null  // false

// It is often better to use strict comparison
0 === false // false
0 === null  // false

        return $str;
    }

    /**
     * Random Hash for protecting URLs
     *
     * @return	string
     */
    public function xss_hash()
    {
        if ($this->_xss_hash == '')
        {
            mt_srand();
            $this->_xss_hash = md5(time() + mt_rand(0, 1999999999));
        }

        return $this->_xss_hash;
    }


}
Distilleries / Expendable

Push — master ( c8c0f9...82094b )

Security::_remove_evil_attributes() B

Complexity

Size

Duplication

Code Coverage

Importance

Logical Operators are used for Control-Flow

Duplication Side-by-Side

Filter issues like
