linux-kernel - Re: [KERNEL] Re: Kernel 4.3 breaks security in systems using capabilities

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Message-ID: <20151109172340.GF3714@ikki.ethgen.ch>
Date:	Mon, 9 Nov 2015 18:23:43 +0100
From:	Klaus Ethgen <Klaus+lkml@...gen.de>
To:	Austin S Hemmelgarn <ahferroin7@...il.com>
Cc:	"Serge E. Hallyn" <serge@...lyn.com>,
	Theodore Ts'o <tytso@....edu>,
	Andy Lutomirski <luto@...capital.net>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Richard Weinberger <richard.weinberger@...il.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Christoph Lameter <cl@...ux.com>,
	Andy Lutomirski <luto@...nel.org>,
	Serge Hallyn <serge.hallyn@...ntu.com>,
	Kees Cook <keescook@...omium.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [KERNEL] Re: Kernel 4.3 breaks security in systems using
 capabilities

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Am Mo den  9. Nov 2015 um 17:28 schrieb Austin S Hemmelgarn:
> >Having some scripts in the process is definitively a nightmare to
> >control. That should be prevented wherever possible. And usually it is
> >as the scripts might be used for computing some values that are used
> >later in privileged stuff.
> It's still unavoidable in a number of cases.  It's easy to re-write scripts
> to fit any local configuration.  It's not anywhere near as easy to re-write
> a compiled program to account for any local configuration.

I would not only say that it is avoidable, it is the worst that can
happen.

Usually a shell is calling a binary to do the real work. So it should
even never ever needed to have some raised privileges for the shell.

> >Good example are all that userspace python tools that throw all that
> >stack traces around the users ears (I don't know if that saying exists
> >in English...) instead of giving proper error messages.
> This is debatable.  While the app should be giving a user friendly error
> message, getting a stack-trace and the exception name (and the exceptions
> are usually sanely named) is still far better than just getting something
> like 'Segmentation Fault', or just returning the error in the return code.
> There is no added security from not providing the stack-trace because there
> is no data leaked by it (it contains no information about the contents of
> variables, and function names and included libraries can easily be seen by
> just looking at the python program itself).

My pointing to that python problem is not about security then about how
lazy some developer are. And lazyness and security is nothing that can
go together.

> >By the way, guys, can we start to _not_ add every one in this discussion
> >to the Cc? Currently I get every mail twice. One from the list and one
> >from Cc. I still leave all Ccs intact with this mail but I would prefer
> >to just reply to the list. If anybody is not reading the list and would
> >like to get the mail, please insist.
> If you're getting duplicates with the same Message-ID header, then your
> mail-server is (arguably) broken.

I do not know any mailserver that cares about message-ids. Even more,
which one is the original one if they differ in body? (as they do for
example in this list.)

It it even more broken as some (surely broken) MUAs reuse message ids.

> It should be delivering exactly one copy of a message with a given
> Message-ID: header (this is really a de-facto standard,

I wouldn't say so.

> GMail, Yahoo, and most other mail-providers do this, as does
> Exchange.

I would say, they are broken as they suppress users data.

> Postfix does not, but it's pretty easy to work around with some
> filtering and procmail).

Well, pestfix dos it right here. A MTA has to transport the mails and
never ever suppress some.

But lets keep that stuff offlist, it is OT. I will go ahead with group
reply.

Regards
   Klaus
- -- 
Klaus Ethgen                              http://www.ethgen.ch/
pub  4096R/4E20AF1C 2011-05-16   Klaus Ethgen <Klaus@...gen.ch>
Fingerprint: 85D4 CA42 952C 949B 1753  62B3 79D0 B06F 4E20 AF1C
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