PHP Security considerations, a quick reference for the newbies.

Buzz — Thu, 20 Mar 2008 09:57:17 +0000

To often I get passed code to review that quite frankly is so full of holes it wouldn’t make an adequate sieve…

So in this quick blog I outline a few simple and easily implemented steps to ensure as you start out in the world of PHP, your first site isn’t hacked within 5 minutes, leaving you a whimpering wrek …

PHP DON’T EXAMPLE 1:

Passing RAW globals to mysql!

i.e.

1 2	$sql = "SELECT * FROM users WHERE email='.$_GET['email']."' and password='".$_GET['password']"';"; $result = mysql_query($sql);

So what is wrong with the above? SQL INJECTION welcome to a world where people want to break your website, simply because they can …

I am not going to add more description, just click through to the wiki pedia entry linked above …

To avoid this PHP comes with two functions mysql_escape_string() and mysql_real_escape_string()

An example taken from the mysql_real_escape_string() page:

Example#2 An example SQL Injection Attack

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<?php
// Query database to check if there are any matching users
$query = "SELECT * FROM users WHERE user='{$_POST['username']}' AND password='{$_POST['password']}'";
mysql_query($query);

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// We didn't check $_POST['password'], it could be anything the user wanted! For example:
$_POST['username'] = 'aidan';
$_POST['password'] = "' OR ''='";// This means the query sent to MySQL would be:
echo $query;
?>

The query sent to MySQL:

1	`SELECT * FROM users WHERE user='aidan' AND password='' OR ''=''`

This would allow anyone to log in without a valid password.

So in summary READ the mysql_real_escape_string() page, and even if you don't implement the "best practice" example on that page PLEASE make sure you at least escape $_SESSION $_GET $_POST inputs with a mysql escape function!

Saiweb » injection

PHP Security considerations, a quick reference for the newbies.