From: Richard Weinberger <richard@nod.at>
To: Pavel Machek <pavel@ucw.cz>
Cc: Jiri Kosina <jkosina@suse.cz>, Kees Cook <keescook@chromium.org>,
LKML <linux-kernel@vger.kernel.org>,
"linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
David Rientjes <rientjes@google.com>,
Aaron Tomlin <atomlin@redhat.com>,
DaeSeok Youn <daeseok.youn@gmail.com>,
Thomas Gleixner <tglx@linutronix.de>,
vdavydov@parallels.com, Rik van Riel <riel@redhat.com>,
Oleg Nesterov <oleg@redhat.com>,
Andrew Morton <akpm@linux-foundation.org>,
Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@redhat.com>, Al Viro <viro@zeniv.linux.org.uk>,
Andy Lutomirski <luto@amacapital.net>,
Brad Spengler <spender@grsecurity.net>
Subject: Re: [PATCH] [RFC] Deter exploit bruteforcing
Date: Sun, 04 Jan 2015 00:07:18 +0100 [thread overview]
Message-ID: <54A87626.4070302@nod.at> (raw)
In-Reply-To: <20150103230140.GA2964@amd>
Am 04.01.2015 um 00:01 schrieb Pavel Machek:
> On Sat 2015-01-03 23:44:18, Richard Weinberger wrote:
>> Am 03.01.2015 um 23:36 schrieb Pavel Machek:
>>>
>>>>>> No. This is not what this patch does.
>>>>>>
>>>>>>> But changing glibc to do sleep(30); abort(); instead of abort(); to
>>>>>>> slow down bruteforcing of canaries makes some kind of sense... and
>>>>>>> should be ok by default.
>>>>>>
>>>>>> As I saidn only focusing one the specific stack canary case is not enough.
>>>>>
>>>>> Ok, so I am now saying "adding random delays to the kernel, hoping
>>>>> they slow attacker down" is bad idea. Feel free to add my NAK to the
>>>>> patch.
>>>>
>>>> The patch does not add random delays nor is hope involved.
>>>>
>>>> It has a very clear purpose, it makes brute force attacks to forking
>>>> services unattractive.
>>>> Exploits often use the fact that after fork() the child has the same memory
>>>> as the parent and therefore an attacker can start fruitful brute force attacks
>>>> to brute stack canaries, offsets, etc. as the new child will always have mostly
>>>> the same memory layout as before.
>>>>
>>>> But I'll happily add your NAK to this series.
>>>
>>> Please do.
>>>
>>>>> If really neccessary, "kill_me_slowly()" syscall would be acceptable,
>>>>> but it seems just sleep(); abort(); combination is enough.
>>>>
>>>> The goal of the patch is not to protect only against brute forcing the stack canary.
>>>> It should protect against all kind of brute forcing using forking services.
>>>>
>>>>> glibc should cover 99% cases where this matters, please just fix glibc,
>>>>> others will follow.
>>>>
>>>> There are a lot of systems out there without glibc.
>>>
>>> Only "interesting" systems that are without glibc are androids, and
>>> they usually run very old kernels.
>>>
>>> If you implement sleep() in glibc, distros will enable it and you'll
>>> protect all the desktop users.
>>>
>>> If you implement it in kernel, it will not be compatible-enough to be
>>> enabled by default, and you'll be protecting special "high security"
>>> distros at most.
>>>
>>>> And many applications make system calls without going though any libc wrapper.
>>>> Hey, we want also protect esoteric distros like http://sta.li. :-)
>>>
>>> No, we don't. We want to maximize number of protected users. And
>>> patching glibc does that. (And then you can patch bionic. And then the
>>> small players will follow).
>>
>> And what about static linked programs or programs which do not use a libc wrapper
>> for system calls?
>> Say, any program written in go?
>
> And what about my Atari 800XL?
If it runs Linux it can be protected.
> How many such programs are on common distributions? <1%
>
> How many systems will your kernel hack leave unprotected? >70%
>
> (Plus, reasonable languages like go should not really allow classical
> buffer overflows, and yes, you'll get protection if you statically
> link against glibc. And AFAICT this has nothing to do with syscalls,
> and everything to do with abort() implementation.).
Go does not use libc at all.
Anyway, you've stated your point.
I'm for a generic solution and not for one which works only for some systems.
Thanks,
//richard
next prev parent reply other threads:[~2015-01-03 23:07 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-12-24 21:39 [PATCH] [RFC] Deter exploit bruteforcing Richard Weinberger
2014-12-30 18:40 ` Kees Cook
2014-12-30 18:49 ` Andy Lutomirski
2014-12-30 18:50 ` Richard Weinberger
2015-01-02 5:11 ` Pavel Machek
2015-01-02 11:00 ` Richard Weinberger
2015-01-02 19:46 ` Pavel Machek
2015-01-02 21:40 ` Richard Weinberger
2015-01-02 22:29 ` Pavel Machek
2015-01-02 22:32 ` Jiri Kosina
2015-01-02 22:46 ` Pavel Machek
2015-01-02 22:49 ` Jiri Kosina
2015-01-02 22:53 ` Jiri Kosina
2015-01-02 22:54 ` Pavel Machek
2015-01-02 23:00 ` Richard Weinberger
2015-01-02 23:08 ` Pavel Machek
2015-01-03 9:45 ` Richard Weinberger
2015-01-03 22:36 ` Pavel Machek
2015-01-03 22:44 ` Richard Weinberger
2015-01-03 23:01 ` Pavel Machek
2015-01-03 23:07 ` Richard Weinberger [this message]
2015-01-03 23:06 ` Andy Lutomirski
2015-01-03 23:19 ` Richard Weinberger
2015-01-05 22:56 ` Kees Cook
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