linux-kernel - Re: [patch] Add basic sanity checks to the syscall execution patch

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Date:	Fri, 05 Sep 2008 14:00:38 +0200
From:	pageexec@...email.hu
To:	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Ingo Molnar <mingo@...e.hu>
CC:	Andi Kleen <andi@...stfloor.org>,
	Arjan van de Ven <arjan@...radead.org>,
	linux-kernel@...r.kernel.org, tglx@...x.de, hpa@...or.com
Subject: Re: [patch] Add basic sanity checks to the syscall execution patch

On 5 Sep 2008 at 13:42, Ingo Molnar wrote:
> The other, more fundamental problem that nobody has mentioned so far is 
> that the check returns -ENOSYS and thus makes rootkit attacks _more 
> robust_ and hence more likely!
> 
> The far better solution would be to insert uncertainty into the picture: 
> some sort of low-frequency watchdog [runs once a second or so] that 
> tries to hide itself from the general kernel scope as much as possible, 
> perhaps as ELF-PIC code at some randomized location, triggered by some 
> frequently used and opaque kernel facility that an attacker can not 
> afford to block or fully filter, and which would just check integrity 
> periodically and with little cost.

there's that adage about history being repeated by those not knowing it ;)
for details see the series based around bypassing Vista's PatchGuard at:

  http://uninformed.org/?v=3
  http://uninformed.org/?v=6
  http://uninformed.org/?v=8

> A good benchmark for such a silent alarm facility would be whether an 
> experienced kernel developer could reliably tell it via a kgdb session 
> and full access to memory and system symbols that such a silent alarm is 
> running on a box. If he cannot do it reliably then there's probably no 
> good way for an attacker either.

i believe the above mentioned papers prove that it's not a good benchmark ;)

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