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From: "Mickaël Salaün" <mic@digikod.net>
To: Pavel Machek <pavel@ucw.cz>,
	"Madhavan T. Venkataraman" <madvenka@linux.microsoft.com>
Cc: kernel-hardening@lists.openwall.com, linux-api@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org,
	linux-fsdevel@vger.kernel.org, linux-integrity@vger.kernel.org,
	linux-kernel@vger.kernel.org,
	linux-security-module@vger.kernel.org, oleg@redhat.com,
	x86@kernel.org, luto@kernel.org, David.Laight@ACULAB.COM,
	fweimer@redhat.com, mark.rutland@arm.com
Subject: Re: [PATCH v2 0/4] [RFC] Implement Trampoline File Descriptor
Date: Thu, 24 Sep 2020 18:44:26 +0200	[thread overview]
Message-ID: <c5ddf0c2-962a-f93a-e666-1c6f64482d97@digikod.net> (raw)
In-Reply-To: <20200923205156.GA12034@duo.ucw.cz>


On 23/09/2020 22:51, Pavel Machek wrote:
> Hi!
> 
>>>> Scenario 2
>>>> ----------
>>>>
>>>> We know what code we need in advance. User trampolines are a good example of
>>>> this. It is possible to define such code statically with some help from the
>>>> kernel.
>>>>
>>>> This RFC addresses (2). (1) needs a general purpose trusted code generator
>>>> and is out of scope for this RFC.
>>>
>>> This is slightly less crazy talk than introduction talking about holes
>>> in W^X. But it is very, very far from normal Unix system, where you
>>> have selection of interpretters to run your malware on (sh, python,
>>> awk, emacs, ...) and often you can even compile malware from sources. 
>>>
>>> And as you noted, we don't have "a general purpose trusted code
>>> generator" for our systems.
>>>
>>> I believe you should simply delete confusing "introduction" and
>>> provide details of super-secure system where your patches would be
>>> useful, instead.
>>
>> This RFC talks about converting dynamic code (which cannot be authenticated)
>> to static code that can be authenticated using signature verification. That
>> is the scope of this RFC.
>>
>> If I have not been clear before, by dynamic code, I mean machine code that is
>> dynamic in nature. Scripts are beyond the scope of this RFC.
>>
>> Also, malware compiled from sources is not dynamic code. That is orthogonal
>> to this RFC. If such malware has a valid signature that the kernel permits its
>> execution, we have a systemic problem.
>>
>> I am not saying that script authentication or compiled malware are not problems.
>> I am just saying that this RFC is not trying to solve all of the security problems.
>> It is trying to define one way to convert dynamic code to static code to address
>> one class of problems.
> 
> Well, you don't have to solve all problems at once.
> 
> But solutions have to exist, and AFAIK in this case they don't. You
> are armoring doors, but ignoring open windows.

FYI, script execution is being addressed (for the kernel part) by this
patch series:
https://lore.kernel.org/lkml/20200924153228.387737-1-mic@digikod.net/

> 
> Or very probably you are thinking about something different than
> normal desktop distros (Debian 10). Because on my systems, I have
> python, gdb and gcc...

It doesn't make sense for a tailored security system to leave all these
tools available to an attacker.

> 
> It would be nice to specify what other pieces need to be present for
> this to make sense -- because it makes no sense on Debian 10.

Not all kernel features make sense for a generic/undefined usage,
especially specific security mechanisms (e.g. SELinux, Smack, Tomoyo,
SafeSetID, LoadPin, IMA, IPE, secure/trusted boot, lockdown, etc.), but
they can still be definitely useful.

> 
> Best regards,
> 									Pavel
> 

  parent reply	other threads:[~2020-09-24 16:45 UTC|newest]

Thread overview: 50+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <210d7cd762d5307c2aa1676705b392bd445f1baa>
2020-09-16 15:08 ` madvenka
2020-09-16 15:08   ` [PATCH v2 1/4] [RFC] fs/trampfd: Implement the trampoline file descriptor API madvenka
2020-09-16 15:08   ` [PATCH v2 2/4] [RFC] x86/trampfd: Provide support for the trampoline file descriptor madvenka
2020-09-16 15:08   ` [PATCH v2 3/4] [RFC] arm64/trampfd: " madvenka
2020-09-16 15:08   ` [PATCH v2 4/4] [RFC] arm/trampfd: " madvenka
2020-09-17  1:04   ` [PATCH v2 0/4] [RFC] Implement Trampoline File Descriptor Florian Weimer
2020-09-17 15:36     ` Madhavan T. Venkataraman
2020-09-17 15:57       ` Madhavan T. Venkataraman
2020-09-17 16:01         ` Florian Weimer
2020-09-23  1:46       ` Arvind Sankar
2020-09-23  9:11         ` Arvind Sankar
2020-09-23 19:17           ` Madhavan T. Venkataraman
2020-09-23 19:51             ` Arvind Sankar
2020-09-23 23:51               ` Madhavan T. Venkataraman
2020-09-24 20:23               ` Madhavan T. Venkataraman
2020-09-24 20:52                 ` Florian Weimer
2020-09-25 22:22                   ` Madhavan T. Venkataraman
2020-09-27 18:25                     ` Madhavan T. Venkataraman
2020-09-24 22:13                 ` Pavel Machek
2020-09-24 23:43                 ` Arvind Sankar
2020-09-25 22:44                   ` Madhavan T. Venkataraman
2020-09-26 15:55                     ` Arvind Sankar
2020-09-27 17:59                       ` Madhavan T. Venkataraman
2020-09-22 21:53 ` madvenka
2020-09-22 21:53   ` [PATCH v2 1/4] [RFC] fs/trampfd: Implement the trampoline file descriptor API madvenka
2020-09-22 21:53   ` [PATCH v2 2/4] [RFC] x86/trampfd: Provide support for the trampoline file descriptor madvenka
2020-09-22 21:53   ` [PATCH v2 3/4] [RFC] arm64/trampfd: " madvenka
2020-09-22 21:53   ` [PATCH v2 4/4] [RFC] arm/trampfd: " madvenka
2020-09-22 21:54   ` [PATCH v2 0/4] [RFC] Implement Trampoline File Descriptor Madhavan T. Venkataraman
2020-09-23  8:14   ` Pavel Machek
2020-09-23  9:14     ` Solar Designer
2020-09-23 14:11       ` Solar Designer
2020-09-23 15:18         ` Pavel Machek
2020-09-23 18:00           ` Solar Designer
2020-09-23 18:21             ` Solar Designer
2020-09-23 14:39       ` Florian Weimer
2020-09-23 18:09         ` Andy Lutomirski
2020-09-23 18:11         ` Solar Designer
2020-09-23 18:49           ` Arvind Sankar
2020-09-23 23:53         ` Madhavan T. Venkataraman
2020-09-23 19:41       ` Madhavan T. Venkataraman
2020-09-23 18:10     ` James Morris
2020-09-23 18:32     ` Madhavan T. Venkataraman
2020-09-23  8:42   ` Pavel Machek
2020-09-23 18:56     ` Madhavan T. Venkataraman
2020-09-23 20:51       ` Pavel Machek
2020-09-23 23:04         ` Madhavan T. Venkataraman
2020-09-24 16:44         ` Mickaël Salaün [this message]
2020-09-24 22:05           ` Pavel Machek
2020-09-25 10:12             ` Mickaël Salaün

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