0

Hi Everyone. A real noob question here, Sorry in advance.

I have found a php function online -

public function ft_xss($str, $charset = 'ISO-8859-1') {
    /*
    * Remove Null Characters
    *
    * This prevents sandwiching null characters
    * between ascii characters, like Java\0script.
    *
    */
    $str = preg_replace('/\0+/', '', $str);
    $str = preg_replace('/(\\\\0)+/', '', $str);

From reading the script, It helps to sanitize against SQL & XSS injection attacks by cleaning user input.
My noob question would be how to use it?

I have the following variable in my php -

$name = $_POST['name'] = filter_var($_POST['name'], FILTER_SANITIZE_STRING);

How can I run the class over my variables ?

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Last Post by everton.retweets
0

Do you have your own class?

If not, remove the public from it and just do the following:

ft_xss($str)

Where $str is the string you want to pass.

Its difficult to say though, since you've only provided half of the function and therefore cannot determine the return type.

0

Hi, Thanks for your reply...
I have done what you said, but I am still getting the error
Call to undefined function ft_xss()...
Here is the full function

define('EPSILON', 1.0e-8);

/**
 * CLASS DEFINITION
 *
 * This class can be used to sanitize user inputs and prevent
 * most of known vulnerabilities
 * it requires at least PHP 5.0
 *
 * @package Filtreatment
 */
class Filtreatment {

public $minval = 0;
public $maxval = 0;
public $error = '';

/**
 * CONSTRUCTOR
 *
 * do some settings at init
 *
 * @param none
 * @return void
 */
function __construct() {
    if ( get_magic_quotes_gpc() ) {
        if ( !defined('MAGICQUOTES') ) define ('MAGICQUOTES', TRUE);
    } else {
        if ( !defined('MAGICQUOTES') ) define ('MAGICQUOTES', FALSE);
    }
}

//-----------------------------------------------------------------------------
/**
 * CHECKS FOR AN INTEGER
 * 
 * if the $minval and|or $maxval are set, a comparison will be performed
 * 
 * NOTE: because the function can return 0 also as a valid result, check with === the return value
 * @param int $input - what to check/transform
 * @return int|bool
 */
public function ft_integer($input) {
    $input_c    = (int)$input;
    $mnval      = (int)$this->minval;
    $mxval      = (int)$this->maxval;

    if ( !$mnval && !$mxval ) {
        return $input_c;
    } else if ( $mnval && $mxval ) {
        // check if they are in order (min <  max)
        if ( $mnval > $mxval ) {
            $temp   = $mnval;
            $mnval  = $mxval;
            $mxval  = $temp;
        }

        // and then check if the value is between these values
        return (($input >= $mnval) && ($input <= $mxval)) ? $input_c : FALSE;
    } else { 
        // only one value set
        if ( $mnval ) return (($input >= $mnval) ? $input_c : FALSE );
        if ( $mxval ) return (($input <= $mxval) ? $input_c : FALSE );
    }

}


//-----------------------------------------------------------------------------
/**
 * CHECKS FOR A FLOAT
 * 
 * if the $minval and|or $maxval are set, a comparison will be performed
 * 
 * @param int $input - what to check/transform
 * @return int|bool
 */
public function ft_float($input) {
    $input_c    = (float)$input;
    $mnval      = (float)$this->minval;
    $mxval      = (float)$this->maxval;

    if ( !$mnval && !$mxval ) {
        return $input_c;
    } else if ( $mnval && $mxval ) {
        // check if they are in order (min <  max)
        if ( $this->ft_realcmp($mnval, $mxval) > 0 ) {
            $temp   = $mnval;
            $mnval  = $mxval;
            $mxval  = $temp;
        }

        // and then check if the value is between these values
        $lt = $this->ft_realcmp($input, $mxval); //-1 or 0 for true
        if ( $lt === -1 || $lt === 0 ) $lt = $input_c; else $lt = FALSE;

        $gt = $this->ft_realcmp($input, $mnval); //1 or 0 for true
        if ( $gt === 1 || $gt === 0 ) $gt = TRUE; else $gt = FALSE;

        return (( $lt && $gt ) ? $input_c : FALSE);
    } else { 
        // only one value set
        if ( $mnval ) {
            $gt = $this->ft_realcmp($input, $mnval); //1 or 0 for true
            return ( $gt === 1 || $gt === 0 ) ? $input_c : FALSE;
        }

        if ( $mxval ) {
            $lt = $this->ft_realcmp($input, $mxval); //-1 or 0 for true
            return ( $lt === -1 || $lt === 0 ) ? $input_c : FALSE;
        }
    }

}

//-----------------------------------------------------------------------------
/**
 * VALIDATES A DATE
 * 
 * must be in YYYY-MM-DD format
 * 
 * @param string $str - date in requested format
 * @return string|bool - the string itselfs only for valid date
 */
public function ft_validdate($str) {
    if ( preg_match("/^([0-9]{4})-([0-9]{1,2})-([0-9]{1,2})$/", $str) ) {
        $arr = split("-",$str);   // splitting the array
        $yy = $arr[0];            // first element of the array is year
        $mm = $arr[1];            // second element is month
        $dd = $arr[2];            // third element is days
        return ( checkdate($mm, $dd, $yy) ? $str : FALSE );
    } else {
        return FALSE;
    }
}

//-----------------------------------------------------------------------------
/**
 * VALIDATES AN EMAIL
 * 
 * implies RFC 2822
 * 
 * @param string $str - email to validate
 * @return string|bool - the string itselfs only for valid email
 */
public function ft_email($email) {
    if (MAGICQUOTES) {
        $value = stripslashes($email);
    }

    // check for @ symbol and maximum allowed lengths
    if (!ereg("^[^@]{1,64}@[^@]{1,255}$", $email)) { return FALSE; }

    // split for sections
    $email_array = explode("@", $email);
    $local_array = explode(".", $email_array[0]);

    for ($i = 0; $i < sizeof($local_array); $i++) {
        if ( !ereg("^(([A-Za-z0-9!#$%&'*+/=?^_`{|}~-][A-Za-z0-9!#$%&'*+/=?^_`{|}~\.-]{0,63})|(\"[^(\\|\")]{0,62}\"))$", $local_array[$i]) ) {
             return FALSE;
        }
    }

    if (!ereg("^\[?[0-9\.]+\]?$", $email_array[1])) { 
    // verify if domain is IP. If not, it must be a valid domain name 
        $domain_array = explode(".", $email_array[1]);
        if (sizeof($domain_array) < 2) { return FALSE; }

        for ($i = 0; $i < sizeof($domain_array); $i++) {
            if (!ereg("^(([A-Za-z0-9][A-Za-z0-9-]{0,61}[A-Za-z0-9])|([A-Za-z0-9]+))$", $domain_array[$i])) { 
                return false; 
            }   
        }
    } // if 

    return $email;
}

//-----------------------------------------------------------------------------
/**
 * PREPARES THE INPUT FOR DATABASE
 * 
 * works with mysql/postgresql
 * NOTE: mysql_real_escape_string() requires that a valid mysql connection (mysql_connect()) exists to work
 * 
 * @param string $value - email to validate
 * @param string $db_type - allow two constants MYSQL | PGSQL
 * @return string|bool $value sanitized value
 */
public function ft_dbsql($value, $db_type = 'MYSQL') {
   if (MAGICQUOTES) {
        $value = stripslashes($value);
    }

    // Quote if not a number or a numeric string
    if (!is_numeric($value)) {
        switch ($db_type) {
            case 'MYSQL': $value = "'" . mysql_real_escape_string($value) . "'"; break;
            case 'PGSQL': $value = "'" . pg_escape_string($value) . "'"; break;
        }
    }

    return $value;
}


//-----------------------------------------------------------------------------
/**
 * WORKS ON A STRING WITH REGEX EXPRESSION
 * 
 * checks a string for specified characters
 * 
 * @param string $value - variable to sanitize
 * @param string $regex - is in a special form detailed below:
 * it contains ONLY allowed characters, ANY other characters making invalid string
 * it must NOT contain begin/end delimitators  /[... ]/
 * eg: 0-9, 0-9A-Za-z, AERS
 * @param int $cv - 1 or 2
 * @return string|bool return string if check succeed ($cv = 1) or string with replaced chars 

 */
public function ft_strregex($value, $regex, $cv = 1) {
    $s = TRUE; //var control
    $regexfull = "/[^" . $regex . "]/";

    // function of $cv might be a clean up operation, or just verifying
    switch ($cv) {
        // verify the string
        case '1': 
            $s = ( preg_match($regexfull, $value) ? FALSE : TRUE ); 
        break;

        // cleanup the string
        case '2':
            $value = preg_replace($regexfull,'',$value);
        break;

        // if $cv is not specified or it's wrong
        default: if ( preg_match($regexfull, $value) ) $s = FALSE;
    }

    return ( $s ? $value : FALSE );
}



//-----------------------------------------------------------------------------
/**
 * CLEANS AGAINST XSS
 * 
 * NOTE all credits goes to codeigniter.com
 * @param string $str - string to check
 * @param string $charset - character set (default ISO-8859-1)
 * @return string|bool $value sanitized string
 */
public function ft_xss($str, $charset = 'ISO-8859-1') {
    /*
    * Remove Null Characters
    *
    * This prevents sandwiching null characters
    * between ascii characters, like Java\0script.
    *
    */
    $str = preg_replace('/\0+/', '', $str);
    $str = preg_replace('/(\\\\0)+/', '', $str);

    /*
    * Validate standard character entities
    *
    * Add a semicolon if missing.  We do this to enable
    * the conversion of entities to ASCII later.
    *
    */
    $str = preg_replace('#(&\#*\w+)[\x00-\x20]+;#u',"\\1;",$str);

    /*
    * Validate UTF16 two byte encoding (x00)
    *
    * Just as above, adds a semicolon if missing.
    *
    */
    $str = preg_replace('#(&\#x*)([0-9A-F]+);*#iu',"\\1\\2;",$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: Normally urldecode() would be easier but it removes plus signs
    *
    */  
    $str = preg_replace("/%u0([a-z0-9]{3})/i", "&#x\\1;", $str);
    $str = preg_replace("/%([a-z0-9]{2})/i", "&#x\\1;", $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.
    *
    */
    if (preg_match_all("/<(.+?)>/si", $str, $matches)) {     
        for ($i = 0; $i < count($matches['0']); $i++) {
            $str = str_replace($matches['1'][$i],
                html_entity_decode($matches['1'][$i], ENT_COMPAT, $charset), $str);
        }
    }

    /*
    * Convert all tabs to spaces
    *
    * This prevents strings like this: ja   vascript
    * Note: we deal with spaces between characters later.
    *
    */      
    $str = preg_replace("#\t+#", " ", $str);

    /*
    * Makes PHP tags safe
    *
    *  Note: XML tags are inadvertently replaced too:
    *
    *   <?xml
    *
    * But it doesn't seem to pose a problem.
    *
    */      
    $str = str_replace(array('<?php', '<?PHP', '<?', '?>'),  array('&lt;?php', '&lt;?PHP', '&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.
    *
    */      
    $words = array('javascript', 'vbscript', 'script', 'applet', 'alert', 'document', 'write', 'cookie', 'window');
    foreach ($words as $word) {
        $temp = '';
        for ($i = 0; $i < strlen($word); $i++) {
            $temp .= substr($word, $i, 1)."\s*";
        }

        $temp = substr($temp, 0, -3);
        $str = preg_replace('#'.$temp.'#s', $word, $str);
        $str = preg_replace('#'.ucfirst($temp).'#s', ucfirst($word), $str);
    }

    /*
    * Remove disallowed Javascript in links or img tags
    */      
    $str = preg_replace("#<a.+?href=.*?(alert\(|alert&\#40;|javascript\:|window\.|document\.|\.cookie|<script|<xss).*?\>.*?</a>#si", "", $str);
            $str = preg_replace("#<img.+?src=.*?(alert\(|alert&\#40;|javascript\:|window\.|document\.|\.cookie|<script|<xss).*?\>#si","", $str);
    $str = preg_replace("#<(script|xss).*?\>#si", "", $str);

    /*
    * Remove JavaScript Event Handlers
    *
    * Note: This code is a little blunt.  It removes
    * the event handler and anything up to the closing >,
    * but it's unlikely to be a problem.
    *
    */      
    $str = preg_replace('#(<[^>]+.*?)(onblur|onchange|onclick|onfocus|onload|onmouseover|onmouseup|onmousedown|onselect|onsubmit|onunload|onkeypress|onkeydown|onkeyup|onresize)[^>]*>#iU',"\\1>",$str);

    /*
    * 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;
    *
    */      
    $str = preg_replace('#<(/*\s*)(alert|applet|basefont|base|behavior|bgsound|blink|body|embed|expression|form|frameset|frame|head|html|ilayer|iframe|input|layer|link|meta|object|plaintext|style|script|textarea|title|xml|xss)([^>]*)>#is', "&lt;\\1\\2\\3&gt;", $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|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
    *
    */  

    $bad = array(
            'document.cookie'   => '',
            'document.write'    => '',
            'window.location'   => '',
            "javascript\s*:"    => '',
            "Redirect\s+302"    => '',
            '<!--'           => '&lt;!--',
            '-->'           => '--&gt;'
    );

    foreach ($bad as $key => $val)  {
            $str = preg_replace("#".$key."#i", $val, $str);
    }

    return $str;

}

//-----------------------------------------------------------------------------
/**
 * DISPLAY ERRORS
 * 
 * @param int $mode - if 1 then echo the string; if 2 then echo the string
 * @return void
 */
public function display_error($mode = 1) {
    $errstr = ( $this->error ) ? $this->error : '';
    if ( $mode == 1 ) {
        echo '<br />' .$this->ft_xss($errstr) . '<br />';
    } else {
        return $this->ft_xss($errstr);
    }
}


//-----------------------------------------------------------------------------
/**
 * REAL COMPARASION BETWEEN FLOATS
 * 
 * 0 - for ==, 1 for r1 > r2, -1 for r1 '<' r2
 *
 * @param float $r1
 * @param float $r2
 * @return int 
 */
private function ft_realcmp($r1, $r2) {
    $diff = $r1 - $r2;

    if ( abs($diff) < EPSILON ) return 0;
    else return $diff < 0 ? -1 : 1;
}


//-----------------------------------------------------------------------------
} // class
0

No, this is a class. Classes are different, you have to create an object of this class in order to call this method. Are you wanting to use multiple methods from this class? If not, here, try this:

<?php

function ft_xss($str, $charset = 'ISO-8859-1') {
    /*
    * Remove Null Characters
    *
    * This prevents sandwiching null characters
    * between ascii characters, like Java\0script.
    *
    */
    $str = preg_replace('/\0+/', '', $str);
    $str = preg_replace('/(\\\\0)+/', '', $str);

    /*
    * Validate standard character entities
    *
    * Add a semicolon if missing.  We do this to enable
    * the conversion of entities to ASCII later.
    *
    */
    $str = preg_replace('#(&\#*\w+)[\x00-\x20]+;#u',"\\1;",$str);

    /*
    * Validate UTF16 two byte encoding (x00)
    *
    * Just as above, adds a semicolon if missing.
    *
    */
    $str = preg_replace('#(&\#x*)([0-9A-F]+);*#iu',"\\1\\2;",$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: Normally urldecode() would be easier but it removes plus signs
    *
    */  
    $str = preg_replace("/%u0([a-z0-9]{3})/i", "&#x\\1;", $str);
    $str = preg_replace("/%([a-z0-9]{2})/i", "&#x\\1;", $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.
    *
    */
    if (preg_match_all("/<(.+?)>/si", $str, $matches)) {     
        for ($i = 0; $i < count($matches['0']); $i++) {
            $str = str_replace($matches['1'][$i],
                html_entity_decode($matches['1'][$i], ENT_COMPAT, $charset), $str);
        }
    }

    /*
    * Convert all tabs to spaces
    *
    * This prevents strings like this: ja   vascript
    * Note: we deal with spaces between characters later.
    *
    */      
    $str = preg_replace("#\t+#", " ", $str);

    /*
    * Makes PHP tags safe
    *
    *  Note: XML tags are inadvertently replaced too:
    *
    *   <?xml
    *
    * But it doesn't seem to pose a problem.
    *
    */      
    $str = str_replace(array('<?php', '<?PHP', '<?', '?>'),  array('&lt;?php', '&lt;?PHP', '&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.
    *
    */      
    $words = array('javascript', 'vbscript', 'script', 'applet', 'alert', 'document', 'write', 'cookie', 'window');
    foreach ($words as $word) {
        $temp = '';
        for ($i = 0; $i < strlen($word); $i++) {
            $temp .= substr($word, $i, 1)."\s*";
        }

        $temp = substr($temp, 0, -3);
        $str = preg_replace('#'.$temp.'#s', $word, $str);
        $str = preg_replace('#'.ucfirst($temp).'#s', ucfirst($word), $str);
    }

    /*
    * Remove disallowed Javascript in links or img tags
    */      
    $str = preg_replace("#<a.+?href=.*?(alert\(|alert&\#40;|javascript\:|window\.|document\.|\.cookie|<script|<xss).*?\>.*?</a>#si", "", $str);
            $str = preg_replace("#<img.+?src=.*?(alert\(|alert&\#40;|javascript\:|window\.|document\.|\.cookie|<script|<xss).*?\>#si","", $str);
    $str = preg_replace("#<(script|xss).*?\>#si", "", $str);

    /*
    * Remove JavaScript Event Handlers
    *
    * Note: This code is a little blunt.  It removes
    * the event handler and anything up to the closing >,
    * but it's unlikely to be a problem.
    *
    */      
    $str = preg_replace('#(<[^>]+.*?)(onblur|onchange|onclick|onfocus|onload|onmouseover|onmouseup|onmousedown|onselect|onsubmit|onunload|onkeypress|onkeydown|onkeyup|onresize)[^>]*>#iU',"\\1>",$str);

    /*
    * 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;
    *
    */      
    $str = preg_replace('#<(/*\s*)(alert|applet|basefont|base|behavior|bgsound|blink|body|embed|expression|form|frameset|frame|head|html|ilayer|iframe|input|layer|link|meta|object|plaintext|style|script|textarea|title|xml|xss)([^>]*)>#is', "&lt;\\1\\2\\3&gt;", $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|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
    *
    */  

    $bad = array(
            'document.cookie'   => '',
            'document.write'    => '',
            'window.location'   => '',
            "javascript\s*:"    => '',
            "Redirect\s+302"    => '',
            '<!--'           => '&lt;!--',
            '-->'           => '--&gt;'
    );

    foreach ($bad as $key => $val)  {
            $str = preg_replace("#".$key."#i", $val, $str);
    }

    return $str;

}

    $str = (string) "Hello<?php world";

    $str2 = ft_xss($str);

    var_dump($str2);
?>
0

Hi, I am trying to use the $str to help protect against user input.

I have added this file in as an include - and I now see
string(19) "Hello<?php world" at the top of the page...

0

Yes.. Since in the example I gave you: var_dump($str2); will print out the result from the function.

If for example, I did this:

    $str = (string) "<script> alert('sff'); </script>";
    $str2 = ft_xss($str);

    echo $str2;

The output would show the "<script>...</script>" because that's what its' been told to do.

So, in your case it would be this:

// Let's look at an example:

$username = $_POST['username']; // posted from a text field.

$validated_username = ft_xss($username);

unset($username); // not needed.

Does this make sense?

0

I have just ran this again without any problems, but my username in the database is still being stored as J A/M+E\'A_B-o\n/d

I thought this will have cleaned the input...to JAMESBOND

I guess im mssing the point here somewhere !!!
So frustrating...

0

For that, you will need to use regex, and somehow remove the the characters from the username. Or, don't allow for such characters to be entered in the first place.

This function you want limits the chances of XSS by stripping the HTML/JS code from the string.

What is it you're trying to do exactly?

0

With your example - I dont understand the unset($username); // not needed.

Would that remove the username var?

I am tryingt o understand two things -
1> How validate a string to allow only letters or numbers.
2> Protect against xss and sql injecting attacks.

There must be an esier way to validate a string and remove none characters from the input...

0

To answer your questions:

With your example - I dont understand the unset($username); // not needed.

Would that remove the username var?

No, since we would store the username in validated_username after we have done the validation.

2) You could use the following:

<?php

    function validateString($str) {

        return $newString = preg_replace('/[^a-z0-9]/i', '', $str);
    }

    $username = "J/A/M/E/S_B/O-N-D";

    echo validateString($username);

    // output: JAMESBOND

The problem with this is: Let's suppose I have a database of usernames, and, each username has to be unique. If the username: "Jamesbond" is taken, and, therefore, someone enters "james_bond" then this function will remove the "_" and if the right measures aren't in place will create another username with this. You could, use the following function which will remove all of the special characters AND then check it against the database.

Protect against xss and sql injecting attacks.

The function ^^ does a pretty good job when it comes to this, of course, it does all depend on how you are handing your SQL queries.. BUT, this function does strip the string against any HTML/JS which could potentially cause XSS.

Does this help?

0

Excellent answers - I will certainly be using this methodology in my web applications, thanks for your time...

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