mysql_real_escape

add a note User Contributed Notes

PhatFingers
21-Oct-2006 05:40


I concur with icydee.  It's important that SQL Injection is prevented on the server side.  A person (or software) doing SQL Injection on your site will often post to your page from one of his own making.  For example, you may present a page like the following on http://examplesite.com/ that sanitizes all data before submitting.



<html>

<head><script type="text/javascript" src="validation.js" /></head>

<body>

  <form method="POST" action="/login.php">

  Name: <input type="text" name="the_acount" value="" /><br/>

  Password: <input type="password" name="pwd" value="" /><br/>

  <input type="submit" name="action" value="Submit" onClick="Sanitize()"/>

</body>

</html>



Your attacker views the source code and makes his own login page on his local hard drive.  It doesn't have to look like or even load from your page as long as he posts the form data to your site using your expected parameters.



<html><body>

  <form method="POST" action="http://examplesite.com/login.php">

  <input type="hidden" name="the_acount" value="1'; drop table users; select 1 where name='" /><br/>

  Password: <input type="hidden" name="pwd" value="Oh, was I supposed to be hashed?" /><br/>

  <input type="submit" name="action" value="Submit" />

</body></html>

johniskew at web-imagineer dot com
20-Oct-2006 10:06


I think instead of just using the quote_smart function to quote whatever the user gives you, you should ideally specify whether you are looking for a string or a number.  For example if you have a user script and are using a sql statement like this, where username is a char or varchar field:

$sql="SELECT id FROM user_table WHERE user_name=".quote_smart($_POST['userName']);



if the user submits 12345 for example, you get:

SELECT id FROM user_table WHERE user_name=12345



Your DB 1) Must convert the 12345 to a string (not a huge deal) 2) Probably cannot use any index you have on that column (could be a bigger deal with a sizeable table)



So i think something more along the lines of:

function quote_smart($val,$valType) and handle the input based on $valType (being either string or numeric)

vbaspcppguy at gmail dot com
17-Oct-2006 08:26


After reading through all the different versions I came up with this:



function quote_smart($value)

{

    if( is_array($value) ) { 

        return array_map("quote_smart", $value);

    } else {

        if( get_magic_quotes_gpc() ) {

            $value = stripslashes($value);

        }

        if( $value == '' ) {

            $value = 'NULL';

        } if( !is_numeric($value) || $value[0] == '0' ) {

            $value = "'".mysql_real_escape_string($value)."'";

        }

        return $value;

    }

}



This version is a little slower but it will recursively handle arrays.

icydee
07-Oct-2006 05:48


codures seems to have missed the point. Even doing client side hashing does not remove the need for server side injection protection in all cases. His example only protects against injection in the password field but does not protect against attacks using the 'the_acount' field.



$password_from_db = sql_query( SELECT password FROM users WHERE user = $_POST["the_acount"] );

IVIaniac
03-Oct-2006 11:37


To aide in the simplicity of things, I try and validate the information before it is even queried to the MySQL server.



For example. With usernames and passwords, I check for spaces. And ; signs. If either of these are in there, then the login request is ignored, since I do not allow either during registration.



So a simple attack like:

1 or 1=1



Isn't even sent. Instead a "Please check username / password and try again" message is displayed. I display the same message when the query is ignored as I do when an invalid login is parsed. As to not "challenge" the attacker. Make them think simply it was an invalide username/password, rather than a big deal like



die("Hacking attempt!!!");



You could very easily implement logging to keep track of malicious IP's and what-not as well.

codures at email dot ro
26-Sep-2006 04:59


In order to avoid SQL injection the most efficient way is to encrypt the password on the client side using javascript hashing algorithm ( a modified MD5, or other ) that accepts a randomly generated sequence of characters every time the user displays the page ( body onBlur = "generate_random_sequence" ). In this way the hash will be different every time the user logs on ( to avoid packet sniffing ).



On the server side all you need to do is to



$password_from_db = sql_query( SELECT password FROM users WHERE user = $_POST["the_acount"] );



$srvsidehash = Algorithm( $password_from_db, $_POST["client_side_generated_sequence"]);



if $_POST["password_hashed"] = $srvsidehash then

  the_acount had supplied a correct password;all ok;

 else

   Die(' use_id or password error');



The difficult part is to reproduce the javascript algorithm on the server side.



Sorry for not posting some real code.

10-Sep-2006 01:22


Would this be better?



functions quote_smart($value) {

    if(is_array($value)) {

        if(get_magic_quotes_gpc()) {

            $value=array_map("stripslashes",$value);

            }

        if(!array_map("is_number",$value)) {

            $value=array_map("mysql_real_escape_string",$value);

            }

        }

    else {

        if(get_magic_quotes_gpc()) {

            $value=stripslashes($value);

            }

        if(!is_number($value)) {

            $value="'" . mysql_real_escape_string($value) . "'";

            }

        }

    return $value;

    }

brian dot folts at gmail dot com
07-Sep-2006 12:25


mysql_real_escape_string is a bit annoying when you need to do it over an array.



function mysql_real_escape_array($t){

    return array_map("mysql_real_escape_string",$t);

}



this one just mysql_real_escape's the whole array.



ex) $_POST=mysql_real_escape_array($_POST);



and then you dont have to worry about forgetting to do this.

FPawlak2 at gmail dot com
04-Sep-2006 09:31


To: eddypearson at gmail dot com



If thing that, this is better:



<?

$_POST  = array_map('mysql_real_escape_string', $_POST);

?>



or



<?

$_SESSION  = array_map('mysql_real_escape_string', $_SESSION);

?>

tomfmason at spammerssuck dot com
05-Aug-2006 07:36


<?php 

include ('includes/db.php');

array_pop($_POST); 

if ( get_magic_quotes_gpc() ) { 

    $_POST= array_map('stripslashes', $_POST); 

} 

$username= mysql_real_escape_string(trim($_POST['username'])); 

$password= mysql_real_escape_string(trim($_POST['password']));

$mdpwd= md5($password); 



$sql= sprintf("SELECT COUNT(*) AS login_match FROM `users` WHERE `username` = '%s' AND `password`= '%s'", $username, $mdpwd); 

$res= mysql_query($sql) or die(mysql_error()); 

$login_match= mysql_result($res, 0, 'login_match'); 



if ( $login_match == 1 ) { 

    //logged in

} else { 

    // not logged in 

}

?>

eddypearson at gmail dot com
28-Jul-2006 10:28


A quick function to mysql_real_escape_string every value in array (Think $_SESSION and $_POST guys).

This may be simple, and to some bloody obvious, but its useful little function, and I could find one on this page so:



function CleanArray($array) {

foreach ($array as $key => $value) {

$array[$key] = mysql_real_escape_string($value);

}

return $array;

}

djogopatrao at gmail dot com
21-Jul-2006 03:39


According to the newsforge refered to by Picky, it is adviseable to run PREPAREd statements in order to avoid injection. Plus, I created a table that stores pre-defined prepared statements and a procedure that runs that query. That way it's possible to control more tighly what's to be queried.



Example in mysql5 lingo:



create sys_queries (

      name varchar(100), # query ID

      mysql_statement text, #

      primary key( name )

);



insert into sys_queries set name='search_users', 'SELECT * FROM users WHERE concat( username, name, email ) REGEXP ?';



delim $$

create sp_perform_query( _name varchar(100), _search_term varchar(255) )

begin

        DECLARE _stat TEXT DEFAULT NULL;

        SELECT mysql_statement INTO _stat FROM sys_queries WHERE name = _name;

        IF _stat IS NOT NULL THEN

                SET @a = _stat;

                SET @b = _search_term;

                PREPARE s FROM @a;

                EXECUTE s USING @b;

        END IF;

end;

$$

delim ;



in PHP5, use mysqli to call the procedure, first arg is the query name, second, the search arg. Still don't know a good way to pass multiple arguments to mysql, so please let me know.

kael dot shipman at DONTSPAMIT! dot gmail dot com
19-Jul-2006 04:19


It seems to me that you could avoid many hassels by loading valid database values into an array at the beginning of the script, then instead of using user input to query the database directly, use it to query the array you've created. For example:



<?php

//you still have to query safely, so always use cleanup functions like eric256's

$categories = sql_query("select catName from categories where pageID = ?",$_GET['pageID']);

while ($cts = @mysql_fetch_row($categories)) {

 //making $cts both the name and the value of the array variable makes it easier to check for in the future.

 //obviously, this naming system wouldn't work for a multidimensional array

 $cat_ar[$cts[0]] = $cts[0];

}

...



//user selects sorting criteria

//this would be from a query string like '?cats[]=cha&cats[]=fah&cats[]=lah&cats[]=badValue...', etc.

$cats = $_GET['cats'];



//verify that values exist in database before building sorting query

foreach($cats as $c) {

 if ($cat_ar[$c]) { //instead of in_array(); maybe I'm just lazy... (see above note)

  $cats1[] = "'".mysql_real_escape_string($c)."'";

 }

}

$cats = $cats1;

//$cats now contains the filtered and escaped values of the query string



$cat_query = '&& (category_name = \''.implode(' || category_name = \'',$cats).'\')';

//build a sql query insert

//$cat_query is now "&& (category_name = 'cha' || category_name = 'fah' || category_name = 'lah')" - badValue has been removed

//since all values have already been verified and escaped, you can simply use them in a query

//however, since $pageID hasn't been cleaned for this query, you still have to use your cleaning function

$items = sql_query("SELECT * FROM items i, categories c WHERE i.catID = c.catID && pageID = ? $cat_query", $pageID);

nicolas
31-May-2006 04:38


Note that mysql_real_escape_string doesn't prepend backslashes to \x00, \n, \r, and and \x1a as mentionned in the documentation, but actually replaces the character with a MySQL acceptable representation for queries (e.g. \n is replaced with the '\n' litteral). (\, ', and " are escaped as documented) This doesn't change how you should use this function, but I think it's good to know.

Aidan Kehoe <php-manual at parhasard dot net>
20-Apr-2006 05:52


eric256 at gmail dot com: the PEAR DB API provides exactly that. See http://pear.php.net/manual/en/package.database.db.intro-query.php

eric256 at gmail dot com
09-Apr-2006 11:27


Hey,

Since SQL injection is such a fear it is beyond me as to why this hasn't been included yet.   I set this function up to take a query with ?'s in it and replace those with the correctly quoted values.  I don't do the "smart quoteing" i quote it in the SQL because i like to see the quotes there.



<?php

function db_query($query) {

  $args  = func_get_args();

  $query = array_shift($args);

  $query = str_replace("?", "%s", $query);

  $args  = array_map('mysql_real_escape_string', $args);

  array_unshift($args,$query);

  $query = call_user_func_array('sprintf',$args);

  $result = mysql_query($query) or die('Query failed: ' . mysql_error());

  return $result;

}

?>



call it like



<?php

$results = db_query("SELECT * FROM users WHERE username='?' AND password = PASSWORD('?');", $username,$password);

?>

This automagicaly quotes them and executes the query for you and also dies if there is an error in the query.

php at iain dot nl
14-Mar-2006 10:45


@ keith dot lawrence at jpmh dot co dot uk:



But an empty string is not per defenition NULL... usually you look for NULLable columns in your database on special occasions, so I think it's best to keep that apart...

keith dot lawrence at jpmh dot co dot uk
13-Mar-2006 07:23


Here's my version, this replaces empty strings with NULLs instead of using a quoted empty string which was causing a sql error when adding empty values to an integer column which allows nulls. Your mileage may vary.



<?php

function quote_smart($value)    {

    if (get_magic_quotes_gpc()) $value = stripslashes($value);

    if($value == '') $value = 'NULL';

    else if (!is_numeric($value) || $value[0] == '0') $value = "'" . mysql_real_escape_string($value) . "'"; //Quote if not integer

    return $value;

}

?>

php at iain dot nl
12-Mar-2006 05:59


It's quite easy to stop the problem of 0666 returning as 666 in the example of quote_smart. Look at this:



<?php

// Quote variable to make safe

function quote_smart($value) {

   // Stripslashes

   if (get_magic_quotes_gpc()) {

       $value = stripslashes($value);

   }

   // Quote if not integer

   if (!is_numeric($value) || $value[0] == '0') {

       $value = "'" . mysql_real_escape_string($value) . "'";

   }

   return $value;

}

?>



It now checks if there is a leading zero, and then it should be treated als a text, instead as a numerical value. Just an easy workaround.

huuanito at hotmail dot com
28-Feb-2006 03:36


just tried on php 4.4.2  the quote_smart example works just fine with 0666 it comes back as 0666 and 00 comes back as 00.  a single 0 gets lost however but I don't see that as a problem, unless of course you want that as your password. quote_smart works for me.

cedric over blog com
07-Feb-2006 12:20


as already said : 

the example is wrong !

If your password is 0666 quote_smart will return : 666

23-Jan-2006 11:03


Here's why pmioni is wrong:



http://shiflett.org/archive/184

matthew at exanimo dot com
13-Aug-2005 10:34


Note that to use quote_smart(), you have to connect to the database via mysql_connect().  Otherwise, mysql_real_escape_string() will have no way of knowing what database you want to use.



If you want to use the OO approach or mysqli_connect(), you're going to have to rewrite quote_smart() to accept a MySQL connection, which it would then pass to mysql_real_escape_string().



This is a pretty lackluster solution, though, for anyone concerned with abstraction.

david
07-Apr-2005 11:25


The problem with this function returning an empty string instead of an escaped string seems to be related to the mysql lib versions installed on the server. On 3 servers, each with php 4.3.10, I had no problems on 2 of them, but got the empty string on the 3rd. The 2 that worked had versions 4.1.x and 4.0.x of mysql. The 3rd that did not work had 3.23.x



The failure also only occurred when I did not have a mysql connection set up before running the escape function. If I did DB::connect (using the PEAR DB object) before running the function, it worked, even if I didn't pass in the connection id. If I ran the function before DB::connect, then I got an empty string.



So, if you are getting an empty string, check your mysql lib version and check where you are connecting to the db in relation to calling the escape function in your code.

S. W.
11-Feb-2005 02:48


For a "best practices" approach to handling user input, one should always include enforcement of input length limitations.  This will avoid potential attacks based on *very* large values being inserted, some of which may not be foiled just by escaping a string.  (Length limits imposed via your form may be bypassed by submitting from a page or tool created by the attacker.)  As a cursory example:



<?php

$maxNameLen = 25;

$limitedName = substr($_POST['username'],0,$maxNameLen);

$safeUsername = mysql_real_escape_string($limitedName);

?>



Note that you'll need to take care to truncate the correct (raw) value and not something that has already been processed.  Otherwise, you're exposing the potential attack data to more potential points of failure, plus valid input may grow in length with escape processing and be incorrectly truncated.

boris-pieper AT t-online DOT de
22-Jan-2005 06:36


well, smth like that



<?php



function escape_string ($string,$dbcon=false) {

   if(version_compare(phpversion(),"4.3.0")=="-1") {

     mysql_escape_string($string);

   } elseif ($dbcon) {

     mysql_real_escape_string($string,$dbcon);

   } else { return false; }

}



?>

manderson at dsrglobal dot com
16-Jan-2005 01:36


The quote_smart() function in the "Best Practice" section does not quote any value which is all numeric. This will drop all zero's from the the lefthand side of a string. While this is intended to simplify the query string when storing numeric values this has a negative effect when trying to store strings which just so happen to be all digits. For instance some zip codes have one or more zero's on the lefthand side, and an MD5 hash may contain all numeric characters and the lefthand characters can be zero's. In these cases the lefthand zero's will be dropped.



I would simply drop the is_numeric() check. There's no reason to not quote numeric values.



<?php



// bad query created using the quote_smart() function

$qs = "UPDATE tbl SET zipcode=" . quote_smart('01234');

// UPDATE tbl SET zipcode=1234



// acceptable query created after dropping the is_numeric() check

$qs = "UPDATE tbl SET number=" . quote_smart('01234');

// UPDATE tbl SET number='01234'



?>

ludvig dot ericson at gmail dot com
01-Jan-2005 10:18


A case where you do not need to escape is when you are about to compare the UI (User Input) with a database through MD5 hashes, infact if you do, the password stored in the database will not match the one in the request.

I had a living  hell trying to solve this in my earlier days, so I just wanted to enligthen any other newbies,



<?php

$try_pass=md5($_POST['u_pass']);

?>



is sufficient escaping.



Cheers

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mysql_real_escape_string

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