From: Davide Brini <dave_br@...1278...>
Date: Fri, 16 Apr 2010 11:02:34 +0100
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Subject: Re: [Openvpn-devel] [PATCH] Harden create_temp_filename()
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On Friday 16 Apr 2010 10:35:54 Gert Doering wrote:

> On Fri, Apr 16, 2010 at 11:16:32AM +0200, David Sommerseth wrote:
> > I'll look more into this, as the only advantage is that if open() with
> > O_EXCL|O_CREAT fails if the file exists, it should be used instead.
> 
> Unfortunately, this won't help against symlink attacks directed to
> non-existant files (like "-> /etc/nologin").
> 
> It *will* protect against symlink attacks to existing files (overwriting
> /etc/passwd or something similarily nasty).

"If O_EXCL and O_CREAT are set, and path names a symbolic link, open() shall 
fail and set errno to [EEXIST], regardless of the contents of the symbolic 
link."

Seems to me that it will fail in any case (or at least it should). I may be 
misunderstanding what you mean though.

-- 
D.