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Other long term problemsOther long term problemsPosted Jun 7, 2012 10:37 UTC (Thu) by neiljerram (subscriber, #12005)In reply to: Other long term problems by pjones Parent article: Fedora, secure boot, and an insecure future > Any malware which can compromise the bios can install whatever secure boot keys it wants and tell the OS everything is hunky dory. No, that's not the case. It has to be quite a bit craftier than just that. Huh? The OP simply said "malware ... can ..."; they didn't say anything about how "crafty" it needed to be to do that. How does your response relate to what the OP said? The spec requires that most code runs in a mode of operation in which the flash which houses the keys has write enable physically disabled. Again, how does that relate? By saying "most" you are allowing that some code runs without key-writing disabled - and clearly this must the case, or else it would be impossible ever to update the keys! So your post does not refute the previous one, or illuminate it. If anything it corroborates it, but strangely using language that sounds like a refutation.
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Other long term problems Posted Jun 7, 2012 16:16 UTC (Thu) by raven667 (subscriber, #5198) [Link]
My guess is that neither of the posters have the slightest idea of what they are talking about.
Other long term problems Posted Jun 8, 2012 1:00 UTC (Fri) by pretter (guest, #84918) [Link]
My guess is that you didn't even do a simple search on the posters' names.
http://fedoraproject.org/wiki/User:Pjones and http://fedoraproject.org/wiki/User:Pjones/Features/Secure... would be a good start.
Other long term problems Posted Jun 8, 2012 8:49 UTC (Fri) by neiljerram (subscriber, #12005) [Link]
I didn't need to do a search to infer that pjones is someone who has been deployed by RH to defend Matthew's plan. A few days ago, pjones wasn't even an LWN subscriber.
This whole thing smells really bad to me. At least two standard ploys have been used here that are usually more associated with politics (in the bad sense of that word).
1. Deploying extra people, previously not well known in the LWN forum, to defend a position by the preponderance of their comments.
2. Saying that we don't need to worry because it's only a proposal at this stage, and nothing is set in stone. (Obviously (1) it is a done deal already, or else all the RH people would be more open in their responses, and (2) when the initial attention and discussion has died down, the proposal will be set in stone.)
Secondly there's the ethical point, that RH have chosen overall to give aid to a Microsoft-inspired and Microsoft-favouring system, and to make themselves hostage to that, instead of unequivocally fighting against that.
Finally there are technical details that just don't seem to make sense, and where the "answers" given in these comments are inadequate and far below LWN's usual level of technical communication.
All in all, I'm afraid it's difficult for me to believe that there isn't an ulterior motive.
Other long term problems Posted Jun 8, 2012 16:30 UTC (Fri) by raven667 (subscriber, #5198) [Link]
> Secondly there's the ethical point, that RH have chosen overall to give aid to a Microsoft-inspired and Microsoft-favouring system, and to make themselves hostage to that, instead of unequivocally fighting against that.
You make it sound like treason, which is a ridiculous concept when applied to this case. Working with standards that MS also works with and has influence over is not an "ethical" challenge. Fedora and mjg59 have already stated their constraints, they are willing to work on secure boot on systems where key management is available to the end user (even if it isn't as user-friendly as they would like) and are not working on secure boot for systems which are boot locked, without key management (Win8 ARM).
> All in all, I'm afraid it's difficult for me to believe that there isn't an ulterior motive.
This isn't a matter of faith, it's a matter of reading the very open dialog that exists. The fact that you see ulterior motives probably reveals more about your own thought process than illuminates the discussion.
Other long term problems Posted Jun 11, 2012 11:51 UTC (Mon) by nix (subscriber, #2304) [Link] A few days ago, pjones wasn't even an LWN subscriber.pjones subscriber ID: 31722 (and he's a guest, so he's not using RH's block subscription -- I assume they have one). Another subscriber ID in the same thread: 84918. By extension, unless holes in the ID are being filled in, pjones has been reading LWN for a while. I'm concerned about this problem too. As I see it there are two possibilities. Either updating keys and adding revocations is prohibited except in a special mode, in which case malware authors will copy whatever that mode is (if necessary by having kernel-mode code loiter and spy on an update in progress to observe variable parameters, before elevating themselves from kernel-mode to BIOS compromise), or updating keys is prohibited but adding revocations is not, in which case malware authors have an instant free DoS attack vector. It is possible that, given a completely compromise-free kernel, malware could never run in kernel mode to spy on a key update -- but firstly a compromise-free kernel is a pipe-dream and secondly malware that couldn't even get to kernel mode could never compromise the BIOS in the first place. So as far as I can see, as long as key updates or revocations are possible under software control at all this whole thing adds no security, adds a lot of inconvenience, and allows MS to prohibit other OSes from running on their ARM devices. (Which is the real point of all this.) Now perhaps key updates and revocations cannot be scripted, and can only be triggered from the BIOS (which means Windows updates cannot provide revocations for insecure keys but can only ask the user to do it). Desktop PCs might be safe, but server-class PCs are not, because they generally allow remote access to their BIOSes using technologies like IPMI. So on such a network malware on *another* machine can watch for a server to start rebooting, add its own key pre-emptively, then later infect it and replace its firmware. In general non-scriptable updates hugely annoy IT staff in large organizations anyway because they mean some poor sap has to walk around physically from desk to desk. So I bet the thing ends up scriptable across all machines, which eliminates its security advantages. Non-scriptable updates would mean that no keys ever got revoked on most desktop devices. So either this thing adds security only until the first key revocation (non-scriptable case) or it adds security only until the bad guys learn how to use a debugger, i.e. not at all (scriptable case). So I guess I still can't see the point of all this.
Other long term problems Posted Jun 11, 2012 12:21 UTC (Mon) by neiljerram (subscriber, #12005) [Link] A few days ago, pjones wasn't even an LWN subscriber.pjones subscriber ID: 31722 (and he's a guest, so he's not using RH's block subscription -- I assume they have one). Another subscriber ID in the same thread: 84918. True, but I thought I saw, a few (or several, now) days ago, "pjones (guest)". But I could be wrong about that, and in any case it's a somewhat distasteful point to make, so please consider that withdrawn. Regarding everything else you wrote: I agree, and thanks for expounding it so clearly.
Other long term problems Posted Jun 11, 2012 19:13 UTC (Mon) by raven667 (subscriber, #5198) [Link]
> It is possible that ...
> Now perhaps key updates and revocation ...
> So I guess I still can't see the point of all this.
This is an actual written standard with actual implementations, your assumptions are questions and those questions have answers. Instead of spilling a lot of ink with possibles and maybes it would be worthwhile to see how this stuff actually works.
Other long term problems Posted Jun 11, 2012 22:03 UTC (Mon) by nix (subscriber, #2304) [Link]
That's true. I didn't think of it until after posting, and I don't really want to wade into the EFI swamp right now anyway.
Other long term problems Posted Jun 11, 2012 23:12 UTC (Mon) by mjg59 (subscriber, #23239) [Link]
There's three levels of key in this. The first is the platform key, or Pk. Below that are the Key Exchange Keys (KEK). Finally there's the actual signature keys, db (for whitelisted keys and hashes) and dbx (for blacklisted ones). KEK updates have to be signed with Pk, and Pk will generally be under the control of the hardware vendor. db and dbx updates can be signed with either Pk or any key present in KEK. So in order to add keys to the white or blacklists, you need to have the private half of a key already.
Most users aren't going to have any of these private keys, so Microsoft mandate that it be possible to enter a "custom mode". The semantics of this aren't well defined, so it's valid for an implementation to manage it either by offering a firmware UI interface to enrol keys directly or to simply let the user delete all the existing keys which results in the system transitioning back to setup mode.
If you have unauthenticated management interfaces on your network then you obviously deserve to lose.
Other long term problems Posted Jun 12, 2012 7:10 UTC (Tue) by nix (subscriber, #2304) [Link] So in order to add keys to the white or blacklists, you need to have the private half of a key already.Aha, that makes sense. (And, again, had I done fifteen minutes of research rather than fifteen minutes' bloviating, I could probably have figured this out myself. So thanks for the information! :) ) I have horrible visions of vendors' getting the setup mode wrong such that the Pk is changed instead, breaking future updates -- but incompetent though most BIOS vendors are, I suppose the Pk is probably burned into the hardware and unchangeable even by an idiot BIOS. I must say the thought of BIOS vendors writing anything at all to do with crypto fills me with trepidation. I'm somewhat surprised that PCs can even boot reliably, with the boot process under the control of people as bad at writing code as BIOS vendors... adding extra complexity to this, particularly extra complexity designed to fail in the direction of not booting, seems seriously unwise to me.
Other long term problems Posted Jun 12, 2012 7:13 UTC (Tue) by mjg59 (subscriber, #23239) [Link]
The crypto code itself is just openssl, and the interface on top is part of Tiano. So, thankfully, there's a single reference codebase for all of this.
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