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

From: Sir Mordred (mordreds-mail.com)
Date: Tue Apr 01 2003 - 06:29:57 CST

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//(#) 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 (mordreds-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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