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

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Message-ID: <31154.1431965087@warthog.procyon.org.uk>
Date:	Mon, 18 May 2015 17:04:47 +0100
From:	David Howells <dhowells@...hat.com>
To:	mmarek@...e.cz, dwmw2@...radead.org
cc:	dhowells@...hat.com,
	Linus Torvalds <torvalds@...ux-foundation.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>
Subject: Should we automatically generate a module signing key at all?

Hi Michal, Dave,

Should we automatically generate a module signing key at all since that has
the possibility of accidentally overwriting a key that the builder has placed
in the tree?

Should we instead provide a script:

	./scripts/generate-key

That generates a key if run and make it so that the build fails if you turn on
module signing and there's no key.

The script could then be parameterised, eg:

	./scripts/generate-key -n dhowells@...hat.com -k rsa2048 -d sha256 \
		-o ./my-signing-key.priv -x ./my-signing-key.x509 \
		-p "correct horse battery staple"

Yes, this might throw randconfig into a strop but that can be dealt with by:

 (1) Requiring anyone who runs randconfig to provide a key first just in case.

 (2) Marking the CONFIG_MODULE_SIG_ALL option to be ignored by randconfig - it
     only applies during installation anyway.

 (3) Accept that module *installation* will fail due to a lack of private key
     and just handle a complete lack of X.509 certs in the source and build
     dirs when assembling system_certificates.S.

David
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