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;
}
?>
mysql_real_escape_string
(PHP 4 >= 4.3.0, PHP 5)
mysql_real_escape_string — Maskiert spezielle Zeichen innerhalb einer Zeichenkette für die Verwendung in einer SQL-Anweisung
Warnung
Diese Erweiterung ist seit PHP 5.5.0 als veraltet markiert und wurde in PHP 7.0.0 entfernt. Verwenden Sie stattdessen die Erweiterungen MySQLi oder PDO_MySQL. Weitere Informationen bietet der Ratgeber MySQL: Auswahl einer API. Alternativen zu dieser Funktion umfassen:
Beschreibung
Maskiert spezielle Zeichen in 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 (mit wenigen Ausnahmen) immer verwendet werden, um Daten abzusichern, bevor sie per Abrage an MySQL übermittelt werden.
Achtung
Sicherheit: Der Standardzeichensatz
Der Zeichensatz muss entweder auf Ebene des Servers oder mittels der API-Funktion mysql_set_charset() gesetzt werden, damit dieser mysql_real_escape_string() beeinflusst. Siehe das Grundlagenkapitel zum Thema Zeichensätze für mehr Informationen.
Parameter-Liste
-
unescaped_string -
Die zu maskierende Zeichenkette.
-
link_identifier -
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_WARNINGerzeugt.
Rückgabewerte
Gibt eine maskierte Zeichenkette zurück oder im Fehlerfall false.
Fehler/Exceptions
Wird diese Funktion ohne MySQL-Verbindung ausgeführt, werden ebenfalls
PHP-Fehler der Stufe E_WARNUNG ausgelöst. Diese
Funktion sollte nur mit einer gültigen MySQL-Verbindung verwendet werden.
Beispiele
Beispiel #1 Einfaches mysql_real_escape_string()-Beispiel
<?php
// Verbindung herstellen
$link = mysql_connect('mysql_host', 'mysql_user', 'mysql_password')
OR die(mysql_error());
// Abfrage erstellen
$query = sprintf("SELECT * FROM users WHERE user='%s' AND password='%s'",
mysql_real_escape_string($user),
mysql_real_escape_string($password));
?>
Beispiel #2 mysql_real_escape_string() benötigt eine Verbindung
Diese Beispiel verdeutlicht, was geschieht, wenn beim Aufruf dieser Funktion keine MySQL-Verbindung vorhanden ist.
<?php
// Wir sind nicht mit MySQL verbunden
$lastname = "O'Reilly";
$_lastname = mysql_real_escape_string($lastname);
$query = "SELECT * FROM actors WHERE last_name = '$_lastname'";
var_dump($_lastname);
var_dump($query);
?>Das oben gezeigte Beispiel erzeugt eine ähnliche Ausgabe wie:
Warning: mysql_real_escape_string(): No such file or directory in /this/test/script.php on line 5 Warning: mysql_real_escape_string(): A link to the server could not be established in /this/test/script.php on line 5 bool(false) string(41) "SELECT * FROM actors WHERE last_name = ''"
Beispiel #3 Ein beispielhafter SQL-Injection-Angriff
<?php
// Wir haben $_POST['password'] nicht überprüft, es könnte
// jeder beliebiger Wert sein, den der Benutzer will!
$_POST['username'] = 'aidan';
$_POST['password'] = "' OR ''='";
// Datenbankabfrage zur Ueberpruefung der Logindaten
$query = "SELECT * FROM users WHERE user='{$_POST['username']}' AND password='{$_POST['password']}'";
mysql_query($query);
// 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 jedem erlauben, sich ohne valides Passwort einzuloggen.
Anmerkungen
Hinweis:
Sie müssen eine Verbindung zu MySQL geöffnet haben, bevor Sie mysql_real_escape_string() verwenden, ansonsten erhalten Sie einen Fehler vom Typ
E_WARNINGund der Rückgabewert wird zufalse. Istlink_identifiernicht angegeben, wird die letzte MySQL-Verbindung verwendet.
Hinweis:
Wenn die Funktion nicht verwendet wird, um die Daten zu maskieren, ist die Abfrage anfällig für SQL-Injection-Angriffe.
Hinweis: mysql_real_escape_string() maskiert weder
%noch_. Diese Zeichen werden in MySQL als Platzhalter interpretiert, wenn sie mitLIKE,GRANToderREVOKEkombiniert werden.
Siehe auch
- mysql_set_charset() - Setzt den Verbindungszeichensatz
- mysql_client_encoding() - Liefert den Namen des Zeichensatzes
add a note
User Contributed Notes 10 notes
feedr ¶
14 years ago
Walter Tross ¶
12 years ago
For further information:
http://dev.mysql.com/doc/refman/5.5/en/mysql-real-escape-string.html
(replace your MySQL version in the URL)
nicolas ¶
18 years ago
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.
sam at numbsafari dot com ¶
12 years ago
No discussion of escaping is complete without telling everyone that you should basically never use external input to generate interpreted code. This goes for SQL statements, or anything you would call any sort of "eval" function on.
So, instead of using this terribly broken function, use parametric prepared statements instead.
Honestly, using user provided data to compose SQL statements should be considered professional negligence and you should be held accountable by your employer or client for not using parametric prepared statements.
What does that mean?
It means instead of building a SQL statement like this:
"INSERT INTO X (A) VALUES(".$_POST["a"].")"
You should use mysqli's prepare() function (http://php.net/manual/en/mysqli.prepare.php) to execute a statement that looks like this:
"INSERT INTO X (A) VALUES(?)"
NB: This doesn't mean you should never generate dynamic SQL statements. What it means is that you should never use user-provided data to generate those statements. Any user-provided data should be passed through as parameters to the statement after it has been prepared.
So, for example, if you are building up a little framework and want to do an insert to a table based on the request URI, it's in your best interest to not take the $_SERVER['REQUEST_URI'] value (or any part of it) and directly concatenate that with your query. Instead, you should parse out the portion of the $_SERVER['REQUEST_URI'] value that you want, and map that through some kind of function or associative array to a non-user provided value. If the mapping produces no value, you know that something is wrong with the user provided data.
Failing to follow this has been the cause of a number of SQL-injection problems in the Ruby On Rails framework, even though it uses parametric prepared statements. This is how GitHub was hacked at one point. So, no language is immune to this problem. That's why this is a general best practice and not something specific to PHP and why you should REALLY adopt it.
Also, you should still do some kind of validation of the data provided by users, even when using parametric prepared statements. This is because that user-provided data will often become part of some generated HTML, and you want to ensure that the user provided data isn't going to cause security problems in the browser.
rohankumar dot 1524 at gmail dot com ¶
3 years ago
There is requirement for old projects which are using `mysql_escape_string`, and upgrading the PHP version to 7 and above. Basically this happens in maintenance projects where we don't know how many files the functions are used in application. We can use [mysqli.real-escape-string][1] for the function:
If you have a typical connection file like `conn.php`
$conn = new mysqli($host, $user, $password, $db);
// may be few more lines to handle the $conn
if (!function_exists('mysql_escape_string')) {
function mysql_escape_string($sting){ // if mysql_escape_string not available
return $conn->real_escape_string($string); // escape using the $conn instance
}
}
[1]: https://www.php.net/manual/en/mysqli.real-escape-string.php
strata_ranger at hotmail dot com ¶
15 years ago
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'
?>
plgs at ozemail dot com dot au ¶
15 years ago
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.
Aljo ¶
7 years ago
@feedr
I elaborated his note as following:
$string = "asda\0sd\x1aas\\\\\\\\dasd\'asdasd\na\'\'sdasdad";
$array1 = array('\\\\\\\\', '\0', '\n', '\r', "'", '"', '\x1a');
$array2 = array('\\\\\\\\\\\\\\\\', '\\\0', '\\\n', '\\\r', "\\\'", '\\\"', '\\\Z');
echo($string);
echo(PHP_EOL);
for( $i=0; $i<count($array1); $i++ ) {
if ($i==0)
$p = '/(?<!\\\\)'.$array1[$i].'(?!\\\\)/';
else
$p = '/(?<!\\\\)'.$array1[$i].'/';
echo($i);
echo($p);
echo( $array2[$i]);
$string = preg_replace($p, $array2[$i], $string);
echo("\t");
echo($string);
echo(PHP_EOL);
}
echo(PHP_EOL);
echo($string);
jonnie ¶
7 years ago
To Quote Sam at Numb Safari
[ "No discussion of escaping is complete without telling everyone that you should basically never use external input to generate interpreted code. This goes for SQL statements, or anything you would call any sort of "eval" function on.
So, instead of using this terribly broken function, use parametric prepared statements instead.
Honestly, using user provided data to compose SQL statements should be considered professional negligence and you should be held accountable by your employer or client for not using parametric prepared statements." ]
Sam is right........
However I do not think it is sensible to stop all sanitising and simply pass the task on to parametric prepared statements.
A particular developer working in a particular situation will always know more about valid input (specific to that context).
If you ask a user to pass in a value you have already given them and you know that all such values start AB****** and the string should be of length 7 or 11 but never any other length then you have the basis of a good pre-sanitiser - different allowable lengths of a string might indicate legacy data.
I would never want to simply pass the rubbish that a malicious user may have passed in through a form to the parametric prepared statements, I would always want to do my own sanity checks first and in some cases these may err on the side of caution and simply choose to abort the Database op completely.
That way my DB does not get clogged up with unsafe statements made safe - it simply does not get clogged up which is better.
Security in layers - sanitisation and validation should still be considered in every situation BEFORE using prepared statements.
In addition as far as I can read into the official doc
==============================================
"Escaping and SQL injection
Bound variables are sent to the server separately from the query and thus cannot interfere with it. The server uses these values directly at the point of execution, after the statement template is parsed. Bound parameters do not need to be escaped as they are never substituted into the query string directly"
That suggests to me that danger is avoided in the internals by alternative handling not by nullification.
This means that a large project with incomplete conversion to prepared statements, legacy code in different parts of an organisation or servers talking to one another could all pass on the bad news from an immune location or situation to one that is not immune.
As long as the sanitisation is competently performed without incurring additional risks then personally I would stick with certain layers of sanitisation and then call the prepared statements.
presto dot dk at gmail dot com ¶
14 years ago
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.
