@(#)Mordred Labs advisory - Integer overflow in PHP str_repeat() function

[Sir Mordred <mordred () s-mail com>]

//@(#) Mordred Security Labs advisory 

Release date: April 1, 2003 
Name: Integer overflow in PHP str_repeat() function
Versions affected: all versions 
Risk: average
Author: Sir Mordred (mordred () s-mail com) 

I. Description: 

PHP is a widely-used general-purpose scripting language that is
especially suited for Web development and can be embedded into HTML.
Please visit http://www.php.net for more information about PHP.

II. Details: 

The function str_repeat(string input, int multiplier) returns input
repeated multiplier times.

The implementation of this function suffers from a simple integer overflow
caused by 
a very long second argument and could allow a local/remote attacker in the
worst case to gain control over the web server.

The following short script will illustrate this vulnerability:

$ cat t.php
<?php 
    str_repeat(str_repeat("A", 0x2000), 0x40000000);
?>

III. Platforms tested

Linux 2.4 with Apache 1.3.27 / PHP 4.3.1

IV. Vendor response

Vendor has been contacted.


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