Re: [PATCH 00/23] Crypto keys and module signing

[Kasatkin, Dmitry]

On Sun, Jun 10, 2012 at 8:47 AM, Rusty Russell <rusty@xxxxxxxxxxxxxxx> wrote:
> On Tue, 05 Jun 2012 14:35:56 +0100, David Howells <dhowells@xxxxxxxxxx> wrote:
>> Rusty Russell <rusty@xxxxxxxxxxxxxxx> wrote:
>>
>> > > If you prefer to have userspace extract the module signature and pass it in
>> > > uargs, here's a tree that will do that:
>> > >
>> > > Â http://git.kernel.org/?p=linux/kernel/git/dhowells/linux-modsign.git;a=shortlog;h=refs/heads/modsign-uarg
>> >
>> > OK, there's merit in this approach: it certainly moves the argument
>> > about how to encode the signature out of my backyard :)
>>
>> Not really. ÂThe signature still has to be created by the kernel build. ÂIt's
>> just that you no longer have to care about the trade off when it comes to
>> parsing it.
>
> Yes, exactly.
>
>> > Should we just bite the bullet and create a new syscall:
>> >
>> > SYSCALL_DEFINE5(init_module2, void __user *, umod,
>> > Â Â Â Â Â Â unsigned long, len, const char __user *, uargs,
>> > Â Â Â Â Â Â Â Â unsigned int, siglen, const char __user *, sig)
>> >
>> > But I'm easily swayed if you prefer the current approach.
>>
>> "The current approach" being to attach signature to the blob? ÂOr to pass the
>> signature separately but in the uargs?
>
> The former.
>
>> I would very much prefer to keep the signature in the blob and have the kernel
>> extract it as there's no particular need for it to be detached - even if you
>> are using IMA.
>>
>> However, I don't think an extra syscall would hurt particularly - except that
>> it uses up more space in the syscall table... ÂIt would, however, be smaller
>> in the signature verification department as the signature neither needs
>> decoding from uargs nor extracting from the blob.
>
> Good. ÂLet's have init_module2(), and let userspace decide where to get
> the signature from.
>

Nice.

> Thanks,
> Rusty.
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