On Fri, 21 Jul 2023 at 14:01, James Bottomley <James.Bottomley@xxxxxxxxxxxxxxxxxxxxx> wrote: > > On Fri, 2023-07-21 at 13:40 +0100, Luca Boccassi wrote: > > On Fri, 21 Jul 2023 at 12:24, James Bottomley > > <James.Bottomley@xxxxxxxxxxxxxxxxxxxxx> wrote: > > > > > > On Fri, 2023-07-21 at 09:55 +0100, Luca Boccassi wrote: > > > > On Fri, 21 Jul 2023 at 02:49, Eric Snowberg > > > > <eric.snowberg@xxxxxxxxxx> wrote: > > > > > > On Jul 20, 2023, at 1:16 PM, Luca Boccassi <bluca@xxxxxxxxxx> > > > > > > wrote: > > > > > > On Thu, 20 Jul 2023 at 18:11, Eric Snowberg > > > > > > <eric.snowberg@xxxxxxxxxx> wrote: > > > [...] > > > > > > > I agree with James in the previous thread; adding the SBAT > > > > > > > section to the kernel should be handled by the signing > > > > > > > tools. It really doesn't need to be included in the > > > > > > > mainline kernel code. I also agree with the sentiment that > > > > > > > mainline and the > > > > > > > stable branches should not have SBAT versions attached > > > > > > > to them. These are things distros should be responsible for > > > > > > > including in their kernel if they want to have SBAT > > > > > > > support. > > > > > > > > > > > > Why would 'signing tools' handle that? It's just a text-based > > > > > > PE section, it doesn't require access to private key > > > > > > materials to be handled, nor it has any relationship with > > > > > > signing. > > > > > > > > > > There is a relationship, the sbat information within the signed > > > > > file can be used for revocation in lieu of revoking the hash or > > > > > signing certificate at a later time. > > > > > > > > No, it is completely disjoint. In fact, the kernel doesn't even > > > > have to be signed at all, but it still _must_ have a .sbat > > > > section when it is used in a UKI. > > > > > > Just a minute, this is wrong. I was talking to Peter after all of > > > this blew up about how we handle signed kernels with no sbat (since > > > we need that still to work for developers who sign their own > > > kernels). I thought he was planning to require an sbat section for > > > all EFI binaries, but he says that's not true. The current way > > > shim does the sbat check is that if the section doesn't exist the > > > binary is processed as having an empty sbat section (i.e. no sbat > > > level checking will be done because there's no named sbat level for > > > anything and it will just work) and they're planning to keep it > > > that way so that a signed but no sbat kernel will always "just > > > work" without any special key handling in shim. So if we're > > > planning to keep this no-sbat case in discrete kernels, even when > > > the shim verifier checks sbat, the UKI kernel will need to work for > > > this case as well. > > > > Are you sure that's not just about local signing? > > Well, my job is to be concerned about how individuals who want to own > their own keys, either in MoK or db, participate in this, so I am > mostly thinking about local signing. Whatever we decide, there must be > a local workflow pathway. Sure but for local signing via MoK that's obviously fine, as one gets to keep the pieces. AFAIK it's a different flow in Shim whether something is authorized by MoK, DB or the built-in cert, so having different policies built-in for those different cases should be doable. Actually at the moment even if Shim loads the image, if it gets authorized by DB .sbat isn't checked at all. > > IE, MoK vs embedded cert auth flow? As far as I know, the plan for > > the 3rd party CA flow is to eventually (very eventually) require it. > > I might have missed some development ofc. > > There is a thought to get sbat adopted by UEFI to solve the dbx > problem, but if that were to happen, UEFI will likely be extremely > concerned about backward compatibility (and as you have remarked, they > and the OEMs adopt at a glacial pace), so, even if they eventually > adopt it, I can't foresee them mandating refusing to execute signed EFI > binaries with no sbat. I'll pretty much stake cash on the compromise > being that for the foreseeable future no sbat gets revoked by dbx and > the plan will be a gradual shift towards sbat ... but all this is > contingent on UEFI adoption in the first place, which isn't a given. > There are also unsolved problems around sbat, like how the master sbat > lists are kept and how they're delivered which must be solved before a > UEFI proposal could be made. I meant Shim + 3rd party CA flow here. UEFI SB 2.0 is so far ahead I'm pretty sure a good chunk of the folks currently talking about it will be retired by the time it actually exist ;-)
