"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.
>> + 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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