On Wed, 2012-09-05 at 09:59 +0930, Rusty Russell wrote:
> "Kasatkin, Dmitry" <dmitry.kasat...@intel.com> writes:
> > Hi,
> >
> > Please read bellow...
> >
> > On Tue, Sep 4, 2012 at 8:55 AM, Rusty Russell <ru...@rustcorp.com.au> wrote:
> >> OK, I took a look at the module.c parts of David and Dmitry's patchsets,
> >> and didn't really like either, but I stole parts of David's to make
> >> this.
> >>
> >> So, here's the module.c part of module signing. I hope you two got time
> >> to discuss the signature format details? Mimi suggested a scheme where
> >> the private key would never be saved on disk (even temporarily), but I
> >> didn't see patches. Frankly it's something we can do later; let's aim
> >> at getting the format right for the next merge window.
> >
> > In our patches key is stored on the disc in encrypted format...
>
> Oh, I missed that twist. Thanks for the explanation.
>
> On consideration, I prefer signing to be the final part of the "modules"
> target rather than modules_install. I run the latter as root, and that
> is wrong for doing any code generation.
Agreed, but keep in mind that 'modules_install' could subsequently strip
the module.
Mimi
> >> + for (i = 0; i < *len - (sizeof(MODULE_SIG_STRING)-1); i++) {
> >> + /* Our memcmp is dumb, speed it up a little. */
> >> + if (((char *)mod)[i] != MODULE_SIG_STRING[0])
> >> + continue;
> >> + if (memcmp(mod, MODULE_SIG_STRING,
> >> strlen(MODULE_SIG_STRING)))
> >
> > should be (mod+i)?
>
> Yes, indeed. Thanks, fixed.
>
> >> + continue;
> >> +
> >> + sig = mod + i + strlen(MODULE_SIG_STRING);
> >> + siglen = *len - i - strlen(MODULE_SIG_STRING);
> >> + *len = i;
> >> + break;
> >> + }
> >
> > In general please clarify why do you need such parsing at all?
> > Why not to have MODULE_SIG_STRING as a last octets of the module and
> > have signature length field before?
> > Then it is easy to get the signature and rest of the module?
> > That will be super fast...
> >
> > Please clarify.
>
> Ignore performance, it's just not an issue here. So the simplest code
> wins.
>
> And it's also simpler to sign a module this way.
>
> (echo '~Module signature appended~'; gpg --sign ....) >> mod.ko
>
> Cheers,
> Rusty.
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