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mysql_real_escape_string

(PHP 4 >= 4.3.0, PHP 5)

mysql_real_escape_stringЭкранирует специальные символы в строках для использования в выражениях SQL

Описание

string mysql_real_escape_string ( string $unescaped_string [, resource $link_identifier ] )

Экранирует специальные символы в unescaped_string , принимая во внимание кодировку соединения, таким образом, что результат можно безопасно использовать в SQL-запросе в функци mysql_query(). Если вставляются бинарные данные, то к ним так же необходимо применять эту функцию.

mysql_real_escape_string() вызывает библиотечную функцмю MySQL mysql_real_escape_string, которая добавляет обратную косую черту к следующим символам: \x00, \n, \r, \, ', " and \x1a.

Эта функция должна всегда (за несколькими исключениями) использоваться для того, чтобы обезопасить данные, вставляемые в запрос перед отправкой его в MySQL.

Список параметров

unescaped_string

Строка, которая должна быть экранирована.

link_identifier

The MySQL connection. If the link identifier is not specified, the last link opened by mysql_connect() is assumed. If no such link is found, it will try to create one as if mysql_connect() was called with no arguments. If by chance no connection is found or established, an E_WARNING level error is generated.

Возвращаемые значения

Возвращает строку, в которой экранированы все необходимые символы, или FALSE в случае ошибки.

Примеры

Пример #1 Простой пример использования mysql_real_escape_string()

<?php
// Connect
$link mysql_connect('mysql_host''mysql_user''mysql_password')
    OR die(
mysql_error());

// Query
$query sprintf("SELECT * FROM users WHERE user='%s' AND password='%s'",
            
mysql_real_escape_string($user),
            
mysql_real_escape_string($password));
?>

Пример #2 Пример взлома с использованием SQL Injection

<?php
// посылаем запрос, чтобы проверить имя и пароль пользователя
$query "SELECT * FROM users WHERE user='{$_POST['username']}' AND password='{$_POST['password']}'";
mysql_query($query);

// Мы не никак проверили переменную $_POST['password'], 
// а она может содержать совсем не то, что мы ожидали. Например:
$_POST['username'] = 'aidan';
$_POST['password'] = "' OR ''='";

// посмотрим, какой запрос будет отправлен в MySQL:
echo $query;
?>

Запрос, который будет отправлен в MySQL:

SELECT * FROM users WHERE name='aidan' AND password='' OR ''=''

Это позволит кому угодно войти в систему без пароля.

Пример #3 Лучший вариант составления запроса

Применение mysql_real_escape_string() к каждой переменной, вставляемой в запрос, предотвращает SQL Injection. Нижеследующий код является наилучшим вариантом составления запросов и не зависит от установки Magic Quotes.

<?php
// Функция экранирования переменных
function quote_smart($value)
{
    
// если magic_quotes_gpc включена - используем stripslashes
    
if (get_magic_quotes_gpc()) {
        
$value stripslashes($value);
    }
    
// Если переменная - число, то экранировать её не нужно
    // если нет - то окружем её кавычками, и экранируем
    
if (!is_numeric($value)) {
        
$value "'" mysql_real_escape_string($value) . "'";
    }
    return 
$value;
}

// Соединяемся
$link mysql_connect('mysql_host''mysql_user''mysql_password')
    OR die(
mysql_error());

// Составляем безопасный запрос
$query sprintf("SELECT * FROM users WHERE user=%s AND password=%s",
            
quote_smart($_POST['username']),
            
quote_smart($_POST['password']));

mysql_query($query);
?>

Запрос, составленный таким образом, будет выполнен без ошибок, и взлом с помощью SQL Injection окажется невозможен.

Примечания

Замечание: Функцию mysql_real_escape_string() можно использовать только после того, как установлено соединение с MySQL. В противном случае возникнет ошибка уровня E_WARNING, а функция возвратит FALSE. Если link_identifier не указан, используется последнее открытое соединение.

Замечание: Если magic_quotes_gpc включены, то сначала данные следует обработать функцией stripslashes(). Если mysql_real_escape_string() применяется к данным, которые уже были прослешены, то в результате слеши в данных будут удваиваться.

Замечание: Если не пользоваться этой функцией, то запрос становится уязвимым для взлома с помощью SQL Injection.

Замечание: mysql_real_escape_string() не экранирует символы % и _. Эти знаки являются масками групп символов в операторах MySQL LIKE, GRANT или REVOKE.

Смотрите также


User Contributed Notes
mysql_real_escape_string
adelbenzarti at yahoo dot fr
19-Jun-2010 10:05
The function mysql_real_escape_string helps the developer to insert data without having troubles in the process or having risks of SQL Injection.
You can develop a similar function :
<?php
       
function escape($str)
        {
               
$search=array("\\","\0","\n","\r","\x1a","'",'"');
               
$replace=array("\\\\","\\0","\\n","\\r","\Z","\'",'\"');
                return
str_replace($search,$replace,$str);
        }
?>
manixrock -~- gmail ~-~ com
16-May-2010 11:07
I've come up with an easy way to more easily escape things in an sql query. The simpler things are, the lower the chance that you'll forget to escape something. I use a helper class:

<?php
class MysqlStringEscaper
{
    function
__get($value)
    {
        return
mysql_real_escape_string($value);
    }
}
$str = new MysqlStringEscaper;
?>

then whenever I run a query I can simply do:

<?php
mysql_query
("SELECT * FROM users WHERE name LIKE '{$str->$name}' LIMIT 10");
?>

This way it's easy to see what the variable is escaped as (other instances like $int or $list could be implemented), it's inline and it only changes the variable when it's inserted into the query.
hikmet1023 at hotmail dot com
25-Mar-2010 09:29
about DATA LENGTH and mysql_real_escape_string

i have just experienced that this function does not harm the data length at all. It seems to use the escaped string during insertion but still insert the UNESCAPED string:

I have tried INSERTing 50 char long string ( containing characters to be escaped) into 50 char long datafield. I could SELECT the data without any loss and i didnt need to UNESCAPE it! So the data comes ready cooked, just serve it to where you need to...

AND BEFORE GOING MAD typing, saving, changing for long hours:

as documented above, do not forget to stripslashes(yourstring) if you have to.

And as documented at mysql manuals: do not use SET NAMES, use mysql_set_charset
gustavo639 at gmail dot com
25-Feb-2010 03:17
I use:

<?php
public static function escaparParametros(){
       
$numParametros = func_num_args();
       
$parametros = func_get_args();

        for (
$i = 0; $i < $numParametros; $i++){
           
$parametros[$i] = mysql_real_escape_string($parametros[$i]);
        }

        return
$parametros;
    }
?>
root at aeze dot ru
24-Feb-2010 05:42
Here my simple but very effective function for safe mysql queries.

<?php
/**
* USAGE: mysql_safe( string $query [, array $params ] )
* $query - SQL query WITHOUT any user-entered parameters. Replace parameters with "?"
*     e.g. $query = "SELECT date from history WHERE login = ?"
* $params - array of parameters
*
* Example:
*    mysql_safe( "SELECT secret FROM db WHERE login = ?", array($login) );    # one parameter
*    mysql_safe( "SELECT secret FROM db WHERE login = ? AND password = ?", array($login, $password) );    # multiple parameters
* That will result safe query to MySQL with escaped $login and $password.
**/
function mysql_safe($query,$params=false) {
    if (
$params) {
        foreach (
$params as &$v) { $v = mysql_real_escape_string($v); }    # Escaping parameters
        # str_replace - replacing ? -> %s. %s is ugly in raw sql query
        # vsprintf - replacing all %s to parameters
       
$sql_query = vsprintf( str_replace("?","'%s'",$query), $params );   
       
$sql_query = mysql_query($sql_query);    # Perfoming escaped query
   
} else {
       
$sql_query = mysql_query($query);    # If no params...
   
}

    return (
$sql_query);
}
?>
presto dot dk at gmail dot com
28-Jan-2010 03:05
If you want to make sure that the ID you're using to do a query is a number, use sprint() of (int) or intval(), but don't use mysql_real_escape_string.

There is no difference between ISO-8859-1's number 10 and UTF-8's number 10.
strata_ranger at hotmail dot com
08-Dec-2009 07:17
There's an interesting quirk in the example #2 about SQL injection:  AND takes priority over OR, so the injected query actually executes as WHERE (user='aidan' AND password='') OR ''='', so instead of returning a database record corresponding to an arbitrary username (in this case 'aidan'), it would actually return ALL database records.  In no particular order.  So an attacker might be able to log in as any account, but not necessarily with any control over which account it is.

Of course a potential attacker could simply modify their parameters to target specific users of interest:

<?php

// E.g. attacker's values
$_POST['username'] = '';
$_POST['password'] = "' OR user = 'administrator' AND '' = '";

// Malformed query
$query = "SELECT * FROM users WHERE user='$_POST[username]' AND password='$_POST[password]'";

echo
$query;

// The query sent to MySQL would read:
// SELECT * FROM users WHERE user='' AND password='' OR user='administrator' AND ''='';
// which would allow anyone to gain access to the account named 'administrator'

?>
alan_a_williams [at] hotmail [dot] com
19-Aug-2009 11:17
Just a little something I like to use....

$_GET = array_map('trim', $_GET);
$_POST = array_map('trim', $_POST);
$_COOKIE = array_map('trim', $_COOKIE);
$_REQUEST = array_map('trim', $_REQUEST);
if(get_magic_quotes_gpc()):
    $_GET = array_map('stripslashes', $_GET);
    $_POST = array_map('stripslashes', $_POST);
    $_COOKIE = array_map('stripslashes', $_COOKIE);
    $_REQUEST = array_map('stripslashes', $_REQUEST);
endif;
$_GET = array_map('mysql_real_escape_string', $_GET);
$_POST = array_map('mysql_real_escape_string', $_POST);
$_COOKIE = array_map('mysql_real_escape_string', $_COOKIE);
$_REQUEST = array_map('mysql_real_escape_string', $_REQUEST);

Seems to do the trick ALOT of the time, but I'm going to be honest, it can be a [EDITED] sometimes >_>
Anonymous
02-Aug-2009 10:45
I use the following code in my database connection include file (which is of course called at the start of every page that needs to do some SQL)...
Therefore, all POST and GET vars are automatically escaped before being used anywhere in SQL statements.

<?php
 
//This stops SQL Injection in POST vars
 
foreach ($_POST as $key => $value) {
   
$_POST[$key] = mysql_real_escape_string($value);
  }

 
//This stops SQL Injection in GET vars
 
foreach ($_GET as $key => $value) {
   
$_GET[$key] = mysql_real_escape_string($value);
  }
?>
plgs at ozemail dot com dot au
27-Jul-2009 08:05
Don't forget that if you're using Mysqli (ie, the "improved" Mysql extension) then you need to use the corresponding mysqli function mysqli_real_escape_string().  The parameter order is also different.
Anonymous
13-Jul-2009 03:30
It is because you swapped $key and $item:

Just change this:
<?php
 
function mysql_safe ( $item, $key, $type )
 
?>

To:

<?php
       
function mysql_safe ( $key, $item, $type )
?>

And it will work as expected.
isaacs dot brian dot c at gmail dot com
12-Jul-2009 06:06
I had wanted to see the merits of dynamically and "automatically" applying mysql_real_escape_string() to $_GET and $_POST as arrays rather than manually each time I would type up a query. I used array_walk_recursive() to call my function "mysql_safe" to apply mysql_real_escape_string() to each key of the $_GET and $_POST arrays.

My function is part of a class, and it is called each time I connect to the database to perform a query:

<?php
class MyClass {
        function
mysql_safe ( $key, $item, $type )
        {
            switch(
$type )
            {           
                case
'get':
                    if(
count( $_GET ) > 0 )
                    {
                       
$_GET[$item] = mysql_real_escape_string( $key );
                    }
                break;
                case
'post':
                    if(
count( $_POST ) > 0 )
                    {
                       
$_POST[$item] = mysql_real_escape_string( $key );
                    }
                break;
            }
        }
       
        function
safe_get ( )
        {
           
#Flag to only run function once           
           
if( $this->get_flag == true ) { return true; }

           
array_walk_recursive( $_GET, array( $this, 'mysql_safe' ), 'get' );
           
array_walk_recursive( $_POST, array( $this, 'mysql_safe' ), 'post' );
           
           
$this->get_flag = true;
        }
}
?>

However, after using this function, I find that it does indeed work, it also creates new $_GET and $_POST values in which $item and $key are swapped. So I end up with $_GET[$item] = $key, as well as $_GET[$key] = $item. I have not yet determined if this is due to the actual coding itself, or my particular method of implementation.

[EDIT BY danbrown AT php DOT net: Contains a bugfix by "Anonymous" on 13-JUL-09 to reorder the user function parameters.]
info at saturnprods dot com
13-Jun-2009 07:37
I always use this function so I don't have to retype over and over the mysql_real_escape_string function.

<?php
function safe($value){
   return
mysql_real_escape_string($value);
}
?>

Then, when I am using my code, I simply use:

<?php
$name
= safe($_POST["name"]);
$password = safe($_POST["password"]);
?>
kendsnyder at gmail dot com
25-Mar-2009 09:07
<?php

// Here is a simple named binding function for queries that makes SQL more readable:
// $sql = "SELECT * FROM users WHERE user = :user AND password = :password";
// mysql_bind($sql, array('user' => $user, 'password' => $password));
// mysql_query($sql);

function mysql_bind(&$sql, $vals) {
    foreach (
$vals as $name => $val) {
       
$sql = str_replace(":$name", "'" . mysql_real_escape_string($val) . "'", $sql);
    }
}

?>
Bastiaan Welmers
24-Mar-2008 07:46
This function won't help you when inserting binary data, to me it will get mallformed into the database. Probably UTF-8 combinations will be translated by this function or somewhere else when inserting data when running mysql in UTF-8 mode.

A better way to insert binary data is to transfer it to hexadecimal notation like this example:

<?php
$string
= $_REQUEST['string'];
$binary = file_get_contents($_FILE['file']['tmp_name']);

$string = mysql_real_escape_string($string);
$binary_hex = bin2hex($binary);

$query = "INSERT INTO `table` (`key`, `string`, `binary`, `other`) VALUES (NULL, '$string', 0x$binary_hex, '$other')";

?>
Anonymous
03-Mar-2008 06:57
My escape function:

Automatically adds quotes (unless $quotes is false), but only for strings. Null values are converted to mysql keyword "null", booleans are converted to 1 or 0, and numbers are left alone. Also can escape a single variable or recursively escape an array of unlimited depth.

<?php
function db_escape($values, $quotes = true) {
    if (
is_array($values)) {
        foreach (
$values as $key => $value) {
           
$values[$key] = db_escape($value, $quotes);
        }
    }
    else if (
$values === null) {
       
$values = 'NULL';
    }
    else if (
is_bool($values)) {
       
$values = $values ? 1 : 0;
    }
    else if (!
is_numeric($values)) {
       
$values = mysql_real_escape_string($values);
        if (
$quotes) {
           
$values = '"' . $values . '"';
        }
    }
    return
$values;
}
?>
matthijs at yourmediafactory dot com
27-Dec-2007 09:49
In response to Michael D - DigitalGemstones.com:

Check the example again: sprintf(%d) already does the int conversion for you, so it's both perfectly save as well as more elegant than manually casting.
user at NOSPAM dot example dot com
28-Aug-2007 12:16
if you're doing a mysql wildcard query with
LIKE, GRANT, or REVOKE
you may use addcslashes to escape the string:

<?php
$param
= mysql_real_escape_string($param);
$param = addcslashes($param, '%_');
?>
brian dot folts at gmail dot com
06-Sep-2006 04:25
mysql_real_escape_string is a bit annoying when you need to do it over an array.

<?php
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) <?php $_POST=mysql_real_escape_array($_POST); ?>

and then you dont have to worry about forgetting to do this.
kael dot shipman at DONTSPAMIT! dot gmail dot com
18-Jul-2006 08:19
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
30-May-2006 08:38
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.
 

 
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