linux-kernel - Re: [GIT PULL] Asymmetric keys and module signing

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Date:	Thu, 27 Sep 2012 09:42:59 +0930
From:	Rusty Russell <rusty@...tcorp.com.au>
To:	David Howells <dhowells@...hat.com>
Cc:	dhowells@...hat.com, herbert@...dor.hengli.com.au,
	pjones@...hat.com, jwboyer@...hat.com,
	linux-crypto@...r.kernel.org,
	linux-security-module@...r.kernel.org,
	linux-kernel@...r.kernel.org, keyrings@...ux-nfs.org
Subject: Re: [GIT PULL] Asymmetric keys and module signing

David Howells <dhowells@...hat.com> writes:

> Rusty Russell <rusty@...tcorp.com.au> wrote:
>
>> We do a very simple search for a particular string appended to the module
>> (which is cache-hot and about to be SHA'd anyway).  There's both a config
>> option and a boot parameter which control whether we accept (and taint) or
>> fail with unsigned modules.
>
> I've adjusted your patch description to this:
>
>     We do a very simple search for a particular string appended to the module
>     (which is cache-hot and about to be SHA'd anyway).  There's both a config
>     option and a boot parameter which control whether we accept or fail with
>     unsigned modules and modules that are signed with an unknown key.
>
>     If module signing is enabled, the kernel will be tainted if a module is
>     accepted that is unsigned or has a signature for which we don't have the
>     key.
>
> I think it's worth mentioning the policy for unknown keys and worth making
> clear under what circumstances we mean the kernel to be tainted.

Great!  I checked your Kconfig help, too, which is states it clearly:

config MODULE_SIG_FORCE
	bool "Require modules to be validly signed"
	depends on MODULE_SIG
	help
	  Reject unsigned modules or signed modules for which we don't have a
	  key.  Without this, such modules will simply taint the kernel.


Which is really nice, since the kernel Kconfig help messages tend to
suck.

Thanks,
Rusty.
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