Re: [RFC v2 7/7] modsig: build rules and scripts to generate keys andsign modules

[Josh Boyer]

On Wed, Aug 15, 2012 at 2:43 PM, Dmitry Kasatkin
<dmitry.kasatkin@xxxxxxxxx> wrote:
> This patch adds build rules and scripts to generate keys and sign modules.
>
> Two scripts has been added. genkey.sh is used to generate private and
> public keys. ksign.sh is used to sign kernel modules. Both scripts
> use only standard utilites from coreutils and additionally requires
> openssl tool for RSA keys creation and signing.
>
> The patch modifies 'modules_install' target and adds two new targets to
> the main kernel Makefile.
>
> 1. signed_modules_install
> This target creates an ephemeral key pair, signs the kernel modules with
> the private key, destroys the private key, and embeds the public key in
> the kernel. (Thanks to Dave Hansen for the target name.)

This requires CONFIG_INTEGRITY_MODULES to be enabled to actually do
anything useful with the signed modules, correct?

>
> 2. modules_install
> When CONFIG_INTEGRITY_MODULES is enabled, this target uses an existing
> private key to sign kernel modules.

If the answer to the above question is yes, then why can't we stick
with a single modules_install command for signing?  It would seem to me
that calling signed_modules_install could use an existing key or
generate an ephemeral key in the absence of one and install the signed
modules, and modules_install would simply install unsigned modules.

Or, alternatively, just make modules_install sign or not sign depending
on whether CONFIG_INTEGRITY_MODULES is enabled.  I don't see why you
would overload a target or create two different ones when both depend
on that option.

Could you explain the reasoning behind that a bit more?

josh
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