Messages in this thread | | | Subject | Re: [PATCH 0/4] KEYS: validate key trust with owner and builtin keys only | From | Mimi Zohar <> | Date | Tue, 10 Jun 2014 10:53:41 -0400 |
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On Tue, 2014-06-10 at 09:29 -0400, Josh Boyer wrote: > On Tue, Jun 10, 2014 at 04:21:36PM +0300, Dmitry Kasatkin wrote: > > On 10/06/14 15:52, Mimi Zohar wrote: > > > On Tue, 2014-06-10 at 08:20 -0400, Josh Boyer wrote: > > >> On Tue, Jun 10, 2014 at 11:48:14AM +0300, Dmitry Kasatkin wrote: > > >>> Also I want to discuss here Fedora UEFI patches as they are the reason for > > >>> the these original patchset. > > >>> > > >>> http://pkgs.fedoraproject.org/cgit/kernel.git/tree/modsign-uefi.patch > > >>> > > >>> They provide functionality to specify MokIgnoreDb variable to limit loading of > > >>> UEFI keys only from MOK List, while ignoring DB. This is certainly a good > > >>> functionality. But once MODULE_SIG_UEFI is enabled, it looks there is no way > > >>> to prevent loading keys from UEFI at all. And this might not be a good default > > >>> functionality. Someone might want not allow loading of keys from UEFI unless > > >>> kernel parameter is specified to allow it without recompiling the kernel > > >>> and disabling MODULE_SIG_UEFI. > > >>> > > >>> Josh, why such design decision was made? > > >> IIRC, it's because kernel parameters can be added programmatically from a > > >> remote user if they gain root access. Having a kernel parameter to > > >> disable a key piece of secure boot isn't all that great. We disable > > >> other kernel parameters like acpi_rspd as well. > > > In this case, there shouldn't be a problem as the kernel parameters > > > would further limit the keys usage. > > > > > > Mimi > > > > Josh probably means that it can be removed and restriction is lifted.. > > And after reboot, all keys come to the keyring.. > > Right. Or if we went with your suggestion of the default being "do not > load UEFI keys", then they could conversely add the parameter instead. > This might not be an immediate threat to the SB attack vector itself > (thought it could be if I thought about it harder), but it's certainly > a change in system behavior that would catch a user unaware.
Agreed, it could catch the user unaware of the change, but always allowing all the UEFI keys, is not a better alternative. Perhaps, requiring the option, would at least prevent the user from being unaware of the change.
Mimi
> At any rate, I'm likely not the best person to weigh in on this aspect. > Matthew has certainly done more thinking about these kinds of problems. > > josh
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