Re: CVE Request: PEAR Installer 1.9.1 <= - Symlink Attack

[Helgi Þormar Þorbjörnsson <helgith () gmail com>]

Hi, 
On 1 Mar 2011, at 09:11, Pierre Joye wrote:

> hi,
>
> 2011/2/28 Dan Rosenberg <dan.j.rosenberg () gmail com>:
> > I'm not familiar with this code or any of the context surrounding this
> > fix, but it appears to be an incomplete fix.  Checking for existence
> > of a symlink and then opening the resource leaves open a window during
> > which a legitimate file can be replaced with a symlink.
>
> Not sure it is fixable, or maybe using a lock on the symbolic link
> while fetching its target (to be tested to be sure that such locks
> cannot be overridden from shell).

I assume you are referring to the parts for REST.php in the patch in question?
At a second look, that part could do with improvements; I wrote up a function which takes TOCTOU into consideration.
I'll have that patch done by the end of the day.

For other situations I am using tempnam() (via the System class) as those files are only temporary and were being 
extracted from compressed archives; The predictability of their end destination where the centre part of the reported 
security problem.

- Helgi