full-disclosure - Re: Symlink vulnerabilities

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Date: Thu, 27 Oct 2011 20:11:55 +0000
From: halfdog <me@...fdog.net>
To: Andrew Farmer <andfarm@...il.com>
Cc: full-disclosure@...ts.grok.org.uk, Valdis.Kletnieks@...edu
Subject: Re: Symlink vulnerabilities

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Andrew Farmer wrote:
> On 2011-10-27, at 07:48, Valdis.Kletnieks@...edu wrote:
>> The other thing that people need to remember is that there's no
>> race condition that's so small that you can't hit it.  If there's
>> a race condition, it *can* be won.
> 
> And systems like inotify make filesystem races trivial to win. I
> wouldn't be surprised if you could win this particular race
> reliably by watching for the files bzexe drops and acting
> immediately when they show up.

You might want to try out my tool from
http://www.halfdog.net/Security/2010/FilesystemRecursionAndSymlinks/
from the references section at end of the page. With appropriate
watchcount parameter, it won every race against each backup system
tested back then. As to my knowledge, only tar was fixed so far.
Running it against cpio even triggers buffer overflow, so direct root
escalation might be possible.

I haven't done proof for MS-Systems, does someone have interest in a
joint venture?

hd

- -- 
http://www.halfdog.net/
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