linux-kernel - Re: Should we automatically generate a module signing key at all?

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Date:	Tue, 19 May 2015 10:58:06 -0700
From:	Andy Lutomirski <luto@...capital.net>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Andy Lutomirski <luto@...nel.org>,
	David Howells <dhowells@...hat.com>,
	Michal Marek <mmarek@...e.cz>,
	David Woodhouse <dwmw2@...radead.org>,
	Abelardo Ricart III <aricart@...nix.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Sedat Dilek <sedat.dilek@...il.com>, keyrings@...ux-nfs.org,
	Rusty Russell <rusty@...tcorp.com.au>,
	LSM List <linux-security-module@...r.kernel.org>,
	Borislav Petkov <bp@...en8.de>, Jiri Kosina <jkosina@...e.cz>
Subject: Re: Should we automatically generate a module signing key at all?

On Tue, May 19, 2015 at 10:44 AM, Linus Torvalds
<torvalds@...ux-foundation.org> wrote:
> On Mon, May 18, 2015 at 5:51 PM, Andy Lutomirski <luto@...nel.org> wrote:
>>
>> I think we should get rid of the idea of automatically generated signing
>> keys entirely.  Instead I think we should generate, at build time, a list of
>> all the module hashes and link that into vmlinux.
>
> Ugh. I think that would be a mistake. It doesn't add any new security
> (it's 100% equivalent to just using a throw-away key), and it adds new
> complexity and a new ordering dependency.
>
> Yes, yes, "throwing away the key" is a somewhat gray area, and just
> unlinking the key-file without any secure erase in theory makes it
> recoverable. In practice, though, it is fine. If you have an attacker
> that has raw access to your disk and almost infinite resources, they
> have easier ways to make your life miserable.

Throwing away the key is outright impossible in some contexts.

https://wiki.debian.org/ReproducibleBuilds

--Andy
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