Re: Re: CVE Request + Advisory: PHP str_repeat() sign mismatch based memory corruption

[Dennis <shr3kst3r () gmail com>]

At companies that host php for customers and use apparmor to jail the
customers, this type of attack would allow a customer to possibly take off
their apparmor hat and gain elevated privileges.  That is, being able to
execute arbitrary code outside of the php runtime in the context of the
apache process would allow the attacker to call change_hat().

- D

On Mon, May 18, 2015 at 5:43 PM, Stanislav Malyshev <smalyshev () gmail com>
wrote:

> Hi!
>
> > About code execution, I haven't had the chance to focus on actual
> > exploitation yet (I surely will in the near future), but as you can see
> > from the original report (https://bugs.php.net/bug.php?id=69403), I
> > pointed out several cases in which working on a so-crafted zval would
> > lead to invalid memory access (with user controlled values as well), so
> > I am pretty confident it is achievable.
>
> These examples all seem to require specific code (like
> 'md5(str_repeat("a", 4294967294-1));') to be run. The probability that
> applications would contain this specific code with str_repeat argument
> controlled by remote user seems to be pretty low. However, if you can
> show exploiting this on a code of an application that is not specially
> crafted to demonstrate this issue, or at least resembles code that is
> likely to be deployed in a real application, I will gladly change my
> opinion.
>
> --
> Stas Malyshev
> smalyshev () gmail com