@(#)Mordred Labs advisory - Integer overflow in PHP memory allocator

[Sir Mordred]

//@(#) Mordred Security Labs advisory

Release date: March 26, 2003
Name: Integer overflow in PHP memory allocator
Versions affected: < 4.3.2
Risk: very high
Author: Sir Mordred (mordred@s-mail.com, http://mslabs.iwebland.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:

In PHP emalloc() function implements the error safe wrapper around malloc().
Unfortunately this function suffers from an integer overflow and
considering the fact that emalloc() is used in many places around PHP
source code, it may lead to many serious security issues.

Here i will describe only a couple of minor issues in a PHP sockets
extension.
This extension is turned off by default and to enable it you should compile
PHP
with --enable-sockets option.

* Issue 1 - Integer sign error in PHP socket_recv() function

Requesting the following short script will cause a httpd child to die with
the error message - child pid <pidnum> exit signal Segmentation fault (11)

$ cat t1.php

<?php
$buf = "";
socket_recv(socket_create(AF_INET, SOCK_STREAM, 0), $buf, -3, 0);
?>

* Issue 2 - Integer sign error in PHP socket_recvfrom() function

Requesting the following script will also cause a httpd child to die.

$ cat t2.php

<?php
$buf = "";
$name = "";
socket_recvfrom(socket_create(AF_INET, SOCK_STREAM, 0), $buf, -3, 0,
$name);
?>


III. Platforms tested

Linux 2.4 with Apache 1.3.27 / PHP 4.3.1

III. Vendor response

PHP developers notified, 4.3.2 will fix this issues.

IV. Last words

There has been response in which we were strongly advised to lower risk
level of this advisory to low or even very low, as long as we can't come up
with an example of using emalloc(userinput) in PHP source code...
We think that this is a provocative crap, and leave the risk level
untouched.



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