bugtraq - Re: /proc filesystem allows bypassing directory permissions on Linux

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Message-ID: <alpine.LSU.2.00.0910271128140.6581@hermes-1.csi.cam.ac.uk>
Date: Tue, 27 Oct 2009 11:29:44 +0000
From: Tony Finch <dot@...at.at>
To: Matthew Dempsky <matthew@...psky.org>
Cc: pavel@....cz, bugtraq@...urityfocus.com
Subject: Re: /proc filesystem allows bypassing directory permissions on
 Linux

On Mon, 26 Oct 2009, Matthew Dempsky wrote:
> On Mon, Oct 26, 2009 at 9:01 AM, Tony Finch <dot@...at.at> wrote:
> >
> > Attacker uses openat() to open and modify the "private" file.
>
> At least with Linux 2.6.18, you still need +x permission on the
> directory to access its contents using openat(2).

According to POSIX, if you open the directory with O_SEARCH then openat()
does not re-check search (+x) permissions.

Tony.
-- 
f.anthony.n.finch  <dot@...at.at>  http://dotat.at/
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