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From: Roman Zippel <zippel@linux-m68k.org>
To: David Howells <dhowells@redhat.com>
Cc: torvalds@osdl.org, akpm@osdl.org, herbert.xu@redhat.com,
	linux-kernel@vger.kernel.org, davej@redhat.com,
	arjan@infradead.org, linux-crypto@vger.kernel.org
Subject: Re: [PATCH 0/6] MODSIGN: Kernel module signing
Date: Thu, 15 Feb 2007 19:33:52 +0100 (CET)	[thread overview]
Message-ID: <Pine.LNX.4.64.0702151901380.14458@scrub.home> (raw)
In-Reply-To: <32081.1171560770@redhat.com>

Hi,

On Thu, 15 Feb 2007, David Howells wrote:

> > This is really the weak point - it offers no advantage over an equivalent 
> > implementation in user space (e.g. in the module tools). So why has to be 
> > done in the kernel?
> 
> Because the init_module() system call is the common point of module submission
> to the kernel, not any particular userspace program.  There is no requirement
> for userspace to load a module by invoking a module tools program or library,
> and so userspace can bypass the checks entirely by just calling init_module().
> Assume for a moment that you can't trust userspace...  (Obviously, if you can't
> trust the kernel then you're already stuffed.)

All the security stuff in the kernel should provide the necessary means to 
restrict this system call.

> It is possible to protect /dev/mem and /dev/kmem or make them unavailable and
> it is possible to protect the kernel's memory whilst it is running (provided
> you don't have nommu or broken hardware and you don't let userspace concoct any
> DMA request it likes) which mostly closes those other vectors I mentioned.
> This isn't something I intended to look at with this patch.  Those are separate
> holes.

Exactly and as long as there are these holes, these patches are only 
kernel bloat. The simple verification can also be done in userspace and 
module signing offers no real security.
What real value do these patches provide, that can't be reached via other 
means? Who else than distributions would be interested in this? Pretty 
much any use you initially mentioned can be done in simpler ways, e.g. 
anyone afraid of modules simply disables module loading completely.

bye, Roman

  reply	other threads:[~2007-02-15 18:34 UTC|newest]

Thread overview: 35+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2007-02-14 19:09 David Howells
2007-02-14 19:09 ` [PATCH 2/6] MODSIGN: In-kernel crypto extensions David Howells
2007-02-14 19:09 ` [PATCH 3/6] MODSIGN: Add indications of module ELF types David Howells
2007-02-14 19:09 ` [PATCH 4/6] MODSIGN: Module ELF verifier David Howells
2007-02-14 19:10 ` [PATCH 5/6] MODSIGN: Module signature checker and key manager David Howells
2007-02-14 19:10 ` [PATCH 6/6] MODSIGN: Apply signature checking to modules on module load David Howells
2007-02-14 19:26 ` [PATCH 0/6] MODSIGN: Kernel module signing Linus Torvalds
2007-02-14 19:40 ` David Howells
2007-02-14 21:32   ` Michael Halcrow
2007-02-14 21:59   ` David Howells
2007-02-14 22:21     ` Michael Halcrow
2007-02-15 21:31   ` Indan Zupancic
2007-02-15  3:41 ` Andrew Morton
2007-02-15  4:13   ` Dave Jones
2007-02-15  5:35     ` Andreas Gruenbacher
2007-02-15  5:45       ` Dave Jones
2007-02-15  6:14         ` Andreas Gruenbacher
2007-02-15  6:22           ` Dave Jones
2007-02-15 20:34           ` Valdis.Kletnieks
2007-02-15 22:12             ` Andreas Gruenbacher
2007-02-16  0:15               ` Olaf Kirch
2007-02-15 22:10           ` Pavel Machek
2007-02-15 20:55     ` Valdis.Kletnieks
2007-02-15 21:32       ` Adrian Bunk
2007-02-15 22:12         ` Valdis.Kletnieks
2007-02-15 14:35 ` Roman Zippel
2007-02-15 17:32 ` David Howells
2007-02-15 18:33   ` Roman Zippel [this message]
2007-02-15 20:01     ` David Lang
2007-02-15 21:01       ` Roman Zippel
2007-02-15 21:03 ` Adrian Bunk
2007-02-15 22:13 ` Pavel Machek
2007-02-16 20:21   ` Dave Jones
2007-02-16 20:27     ` Arjan van de Ven
     [not found] <7OPWh-470-9@gated-at.bofh.it>
     [not found] ` <7OxPF-16i-7@gated-at.bofh.it>
     [not found]   ` <7OSKA-8A-17@gated-at.bofh.it>
     [not found]     ` <7OTGJ-1G5-23@gated-at.bofh.it>
2007-02-16 15:38       ` Bodo Eggert

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