full-disclosure - Re: Linux Local Root -- CVE-2012-0056 -- Detailed Write-up

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Date: Mon, 23 Jan 2012 09:22:19 +0000
From: halfdog <me@...fdog.net>
To: "Jason A. Donenfeld" <Jason@...c4.com>
Cc: full-disclosure@...ts.grok.org.uk
Subject: Re: Linux Local Root -- CVE-2012-0056 -- Detailed
 Write-up

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Hello Jason,

Jason A. Donenfeld wrote:
> Hey Mark,
> 
> For the longest time /proc/pid/mem writing was ifdef'd out. Then
> for the 2.6.39 kernel release, they deemed that the work they'd
> been doing to make the writing interface secure was strong enough,
> so they included the ability to write [1]. So versions before
> 2.6.39 are not vulnerable, and after it (until 3.3, I guess) are.
> Hope this clarifies.

Nice writeup. They should have known to comment out is bad thing, they
already received exploit demo 2011 when fixing CVE-2011-1020

http://www.halfdog.net/Security/2011/SuidBinariesAndProcInterface/

If /procc/[pid]/mem would be writeable on standard linux kernels, this
program should give local root privilege escalation (SeekHelper.c),
e.g. ./SeekHelper /proc/self/mem 8048000 /usr/bin/sudoedit -p xxx
/etc/sudoers with a crafted address and promt payload. Currently
something else is still blocking in kernel, could be fs/proc/base.c

hd


> Jason
> 
> [1]
> http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=198214a7
>
>
> 
On Mon, Jan 23, 2012 at 04:09, mark cunningham
> <markcunninghamemail@...il.com>  wrote:
>> Hey great write up on the exploit, sorry for contacting you off
>> list. From your post I gather it's only 2.6.39 that's vulnerable
>> right? http://security-tracker.debian.org/tracker/CVE-2012-0056
>> is showing that lower versions are "fixed" and just "not
>> vulerable" and I coulnd't get it to work with kernel 2.6.32, but
>> figured maybe there was a chance it still worked for all of 2.6
>> as i see linus has commited it to 2.6
>> 
>> Mark
>> 
>> On Sun, Jan 22, 2012 at 6:19 PM, Jason A.
>> Donenfeld<Jason@...c4.com>  wrote:
>>> Hey Everyone,
>>> 
>>> I did a detailed write-up on exploiting CVE-2012-0056 that some
>>> of y'all might appreciate. Pretty fun bug to play with --
>>> dup2ing all over the place for the prize of getting to write
>>> arbitrary process memory into su :-).
>>> 
>>> The write up is available on my blog here:
>>> http://blog.zx2c4.com/749 . Enjoy.
>>> 
>>> Jason
>>> 
>>> _______________________________________________ Full-Disclosure
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> 
> _______________________________________________ Full-Disclosure -
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- -- 
http://www.halfdog.net/
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