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SubjectRe: [RFC][PATCH 1/2] modsig: add support to sign kernel modules using ephemeral keys
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On Tue, 2012-12-04 at 18:14 +0000, David Howells wrote:
> Rusty Russell <rusty@rustcorp.com.au> wrote:
>
> > > +PHONY += _newmodpubkey_
> > > +_newmodpubkey_:
> > > + @rm -f $(MODSECKEY) $(MODPUBKEY)
> > > + $(Q)$(MAKE) -W kernel/modsign_pubkey.o
>
> Please don't do this. It can muck up the dependencies as make thinks it has
> already done this file at this point. Also, rebuilding bzImage yet again
> wouldn't be the best. We already do it a number of times. Further, if
> vmlinux is already installed when you rebuild, you may confuse gdb if the
> debuginfo then no longer matches vmlinux.

> You have to expose the private key *anyway* - so how much does this actually
> gain you? Especially with a one-shot transient key.

The issue is creating a new keypair is tied to modsign_pubkey. This
patch forces the creation of a new keypair, by removing the existing
one, compiles modsign_pubkey.o, and rebuilds the bzImage, and only then
signs the kernel modules and removes the private key. The benefits of
defining a separate target to generate a keypair are described in the
patch description.

Mimi



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