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mysql_real_escape_string — Maskiert spezielle Zeichen innerhalb eines Strings für die Verwendung in einer SQL-Anweisung
Maskiert spezielle Zeichen im unescaped_string unter Berücksichtigung des aktuellen Zeichensatzes der Verbindung, so dass das Ergebnis ohne Probleme in mysql_query() verwendet werden kann. Wenn Sie Binärdaten einfügen wollen, müssen Sie die Funktion auf jeden Fall verwenden.
mysql_real_escape_string() ruft die Funktion mysql_real_escape_string der MySQL-Bibliothek auf, die folgende Zeichen mit einem Backslash ('\') versieht: \x00, \n, \r, \, ', " und \x1a.
Die Funktion muss immer (mit wenigen Ausnahmen) verwendet werden, um Daten abzusichern, bevor sie per Query an MySQL übermittelt werden.
Der zu maskierende String.
Die MySQL-Verbindung. Wird die Verbindungskennung nicht angegeben, wird die letzte durch mysql_connect() geöffnete Verbindung angenommen. Falls keine solche Verbindung gefunden wird, wird versucht, eine Verbindung aufzubauen, wie es beim Aufruf von mysql_connect() ohne Angabe von Argumenten der Fall wäre. Falls zufällig keine Verbindung gefunden oder aufgebaut werden kann, wird eine Warnung der Stufe E_WARNING erzeugt.
Gibt einen maskierten String oder im Fehlerfall FALSE zurück.
Beispiel #1 Einfaches mysql_real_escape_string()-Beispiel
<?php
// Verbindung herstellen
$link = mysql_connect('mysql_host', 'mysql_user', 'mysql_password')
OR die(mysql_error());
// Anfrage erstellen
$query = sprintf("SELECT * FROM users WHERE user='%s' AND password='%s'",
mysql_real_escape_string($user),
mysql_real_escape_string($password));
?>
Beispiel #2 Ein beispielhafter SQL Injection Angriff
<?php
// Datenbankabfrage zur Ueberpruefung der Logindaten
$query = "SELECT * FROM users WHERE user='{$_POST['username']}' AND password='{$_POST['password']}'";
mysql_query($query);
// Wir haben $_POST['password'] nicht geprueft, es koennte also alles darin
// stehen, was der User will. Zum Beispiel:
$_POST['username'] = 'aidan';
$_POST['password'] = "' OR ''='";
// Das bedeutet, der an MySQL gesendete Query wuerde sein:
echo $query;
?>
Die Abfrage, die an MySQL übermittelt wird:
SELECT * FROM users WHERE user='aidan' AND password='' OR ''=''
Dies würde jedermann erlauben, sich ohne valides Passwort einzuloggen.
Hinweis:
Sie müssen eine Verbindung zu MySQL geöffnet haben, bevor Sie mysql_real_escape_string() verwenden, ansonsten erhalten Sie einen Fehler vom Typ E_WARNING und der Rückgabewert wird zu FALSE. Ist link_identifier nicht angegeben, wird die letzte MySQL-Verbindung verwendet.
Hinweis:
Ist magic_quotes_gpc aktiviert, wenden Sie zuerst stripslashes() auf die Daten an. Das Bearbeiten bereits in irgend einer Form maskierter Daten durch mysql_real_escape_string führt ansonsten dazu, dass bereits Maskiertes doppelt maskiert wird.
Hinweis:
Wenn die Funktion nicht verwendet wird, um die Daten zu maskieren, ist der Query anfällig für SQL Injection Angriffe.
Hinweis: mysql_real_escape_string() maskiert weder % noch _. Diese Zeichen werden in MySQL als Platzhalter interpretiert, wenn sie mit LIKE, GRANT oder REVOKE kombiniert werden.
Just a little function which mimics the original mysql_real_escape_string but which doesn't need an active mysql connection. Could be implemented as a static function in a database class. Hope it helps someone.
<?php
function mysql_escape_mimic($inp) {
if(is_array($inp))
return array_map(__METHOD__, $inp);
if(!empty($inp) && is_string($inp)) {
return str_replace(array('\\', "\0", "\n", "\r", "'", '"', "\x1a"), array('\\\\', '\\0', '\\n', '\\r', "\\'", '\\"', '\\Z'), $inp);
}
return $inp;
}
?>
calling this function twice, or on a string for which quotes have already been escaped, causes the quotes to be escaped twice.An example is where we have to check for magic_quotes_gpc before calling mysql_escape_string to sanitize the inputs.
The following function can be used to escape singe and double quotes in a string with out the risk of escaping quotes twice.This function escapes a quote, only if it hasn't already been escaped.
<?php
function safe_string_escape($str)
{
$len=strlen($str);
$escapeCount=0;
$targetString='';
for($offset=0;$offset<$len;$offset++) {
switch($c=$str{$offset}) {
case "'":
// Escapes this quote only if its not preceded by an unescaped backslash
if($escapeCount % 2 == 0) $targetString.="\\";
$escapeCount=0;
$targetString.=$c;
break;
case '"':
// Escapes this quote only if its not preceded by an unescaped backslash
if($escapeCount % 2 == 0) $targetString.="\\";
$escapeCount=0;
$targetString.=$c;
break;
case '\\':
$escapeCount++;
$targetString.=$c;
break;
default:
$escapeCount=0;
$targetString.=$c;
}
}
return $targetString;
}
echo safe_string_escape("asda'sda\'dsad\"sadasd'");
?>
above code echoes
asda\'sda\'dsad\"sadasd\'
You can see that the second single quote wasnt escaped again..
You should use mysql_real_escape_string only before inserting the data into your table, otherwise you could just use this function :
function reverse_escape($str)
{
$search=array("\\\\","\\0","\\n","\\r","\Z","\'",'\"');
$replace=array("\\","\0","\n","\r","\x1a","'",'"');
return str_replace($search,$replace,$str);
}
You can also use the escape function in a manner as shown in the snapshot out of my own browsertools class:
<?php
//
// MySQL Database connection
//
public function mysqlConnect($host, $user, $password, $database) {
$this->mysql = mysql_connect($host, $user, $password);
if (!$this->mysql) die(mysql_error());
mysql_select_db($database, $this->mysql);
}
//
// MySQL Query
// usage:
// $query such as "SELECT * FROM users WHERE nick = '%s' AND pass = '%s'"
// where %s are the placeholders for the parameters
// call:
// $__->mysqlQuery( $query, arg0, arg1, arg2, ... )
// description:
// The parameters given to the function are escaped through mysql_real_escape_string(),
// merged with the query and then given to the mysql_query function.
// returns:
// Array of lines returned by the MySQL Database
//
public function mysqlQuery($query) {
$numParams = func_num_args();
$params = func_get_args();
if ($numParams > 1) {
for ($i = 1; $i < $numParams; $i++){
$params[$i] = mysql_real_escape_string($params[$i]);
}
$query = call_user_func_array('sprintf', $params);
}
$this->result = mysql_query($query, $this->mysql);
if (!$this->result) die(mysql_error());
$ret = array();
while ($row = mysql_fetch_assoc($this->result)) {
$ret[] = $row;
}
mysql_free_result($this->result);
return $ret;
}
?>
Also don't forget to escape $_COOKIE array before quering the database. In firefox you can edit cookies and insert and inject harmful sql queries.
<?php
foreach ($_COOKIE as $key => $value) {
if(get_magic_quotes_gpc()) $_COOKIE[$key]=stripslashes($value);
$_COOKIE[$key] = mysql_real_escape_string($value);
}
?>
The function mysql_real_escape_string helps the developer to insert data without having troubles in the process or having risks of SQL Injection.
You can develop a similar function :
<?php
function escape($str)
{
$search=array("\\","\0","\n","\r","\x1a","'",'"');
$replace=array("\\\\","\\0","\\n","\\r","\Z","\'",'\"');
return str_replace($search,$replace,$str);
}
?>
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.
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
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;
}
?>
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);
}
?>
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.
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'
?>
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', $_REQUEST);
Seems to do the trick ALOT of the time, but I'm going to be honest, it can be a [EDITED] sometimes >_>
I use the following code in my database connection include file (which is of course called at the start of every page that needs to do some SQL)...
Therefore, all POST and GET vars are automatically escaped before being used anywhere in SQL statements.
<?php
//This stops SQL Injection in POST vars
foreach ($_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);
}
?>
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.
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.
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] = $item. I have not yet determined if this is due to the actual coding itself, or my particular method of implementation.
[EDIT BY danbrown AT php DOT net: Contains a bugfix by "Anonymous" on 13-JUL-09 to reorder the user function parameters.]
I always use this function so I don't have to retype over and over the mysql_real_escape_string function.
<?php
function safe($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"]);
?>
<?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);
}
}
?>
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')";
?>
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;
}
?>
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.
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, '%_');
?>
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.
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);
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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