Re: [coreboot] T450S + Coreboot

[Nico Huber]

Hi Mike,

On 30.08.2018 15:51, Mike Banon wrote:
  The fact that
it's closed source and not user-controlled (Even if you had
 the sources, you can't modify them and update it to your custom ME
 version) is where the problem actually is. There *might* be a backdoor
 hidden somewhere in there, or maybe there isn't, nobody knows.
 
 I agree with your statement above. But, please look on this question
 from the end user's perspective, who might be not a software
 developer. Imagine that you have a choice between two
 similar-by-performance coreboot-supported laptops: according to
 cpubenchmark's passmark, Lenovo G505S's AMD A10-5750M = 3342 points
 (from 886 samples) while Librem 15's Intel i7-6500U = 4429 points
 (from 3345 samples), so the CPU performance difference is just 1/3 (
 and at the fresh test results there might be little to none, since the
 Intel-only Meltdown vulnerability requires a patch which eats up to
 30% performance depending on the workload, and there are also some
 other Intel-specific "performance-eating" vulnerabilities, the most
 serious of which - TLBleed / T1TF - may soon require the disabling of
 HyperThreading at all the Intel CPUs, see [1] and [2] )
You are comparing worst case scenarios of one CPU that would be
considered secure by current research and one that hasn't been
researched as much. That alone doesn't make much sense. Also, why
do you assume that one runs untrusted code on his laptop? If one
doesn't, he also doesn't need performance eating mitigations for
these vulnerabilities. You probably need to do more research about
what Meltdown and the Spectre vulnerabilities are and what they
imply.

  Your
comparison of saying the ME is a backdoor is like saying that a
 webcam is a spying device because it can capture images of you! [...]
 The fact that the webcam schematics isn't open means that it could
 still have a small wifi or GSM chip embedded inside
 
 Yes, but I could easily put a tape over that webcam, disconnect and
 remove a webcam module from the laptop's case (or even make a custom
 DIY kill-switch). Same for a microphone - could be easily desoldered
 (and maybe soldered back but through a kill-switch). And for the
 speakers: according to the recent researches the speakers could act as
 a microphone - see [3] - so Librem 15 should have a kill-switch for
 the speakers as well. Meanwhile you can't throw away ME the same easy
 way.
Your are talking past each other. That you can put some tape over a
webcam doesn't answer the question if you should call it a spying
device. What if you buy a webcam to use it as webcam? is it a spying
device?

  
  you yourself said earlier, when talking about the
AtomBIOS
 that "it could be disassembled quite well with AtomDis -
 https://github.com/mikebdp2/AtomDis - reducing any security concerns
 regarding this blob to a minimum.", well, the ME can be disassembled
 with any x86 disassembler, so why can't you also say that "reduces any
 security concerns regarding the ME to a minimum".
 
 Actually this AtomBIOS blob is not required to run this laptop, only
 to initialize its' display. It is possible to turn this laptop into a
 miniPC/server and still use its' hardware without this blob, although
 it wouldn't be exactly a laptop after that. But if we would consider
 this blob as required: here is a quality of disassembly I'm getting
 with AtomDis - https://pastebin.com/xKW9FV58 . All the command tables
 and data tables are named and in many cases it could be understood
 what some particular piece of code is doing even after a quick glance.
 Are you sure that your ME blob x86 disassembly is providing a similar
 or higher level of transparency? Perhaps it is this level of
 transparency which allowed to 95% complete the development of the
 opensource AtomBIOS alternative called OpenAtom ( I think the
 development efforts have stopped partially because no-one have noticed
 any backdoors after completing the 95% and it became much less
 interesting to complete the remaining 5% , [4] )
Can you point me to these 95%? What I see in the repository is rather
1% (I only see a replay). Maybe I'm just looking at the wrong files.
Regarding the disassembly, I don't understand shit in there (and I've
written display init code myself).

  Actually it might be a good idea for Purism to at
least consider the
 switch to AMD Ryzen CPUs. Yes, unlike the 15h/early16h gen AMD CPUs,
 their new Ryzen CPUs contain the PSP, Platform Security Processor -
 which is also a management engine. But it is significantly younger
 than Intel ME (Skylake's ME is already generation 11), so PSP should
 have less sophisticated protections and it should be easier to
 "jailbreak" this "young PSP" rather than "modern ME". Early
ME
 implementations were also weak, after all, and I expect "young PSP" to
 be weak also.
I agree that Purism should evaluate AMD options. Actually I assume,
they do. Saying that a younger version is less sophisticated seems odd
though, as the vulnerabilities in ME11 didn't exist earlier. Also,
investing in a platform that you would have to "jailbreak" is wrong.
You'd be giving them money for something you don't want.

  Also, those AMD CPUs do not suffer from the
 recently-discovered Intel-specific vulnerabilities and their
 performance-degrading patches will not be required. Finally, AMD had a
 good collaboration history with coreboot (although this collaboration
 is not active currently, it might be renewed if there will be enough
 mutual interest) - and I believe AMD at least will not be as hostile
 towards your opensource/reverse-engineering efforts as Intel is
 currently. If any of these statements seems reasonable to you, please
 think of trying to make your Purism company to at least consider this
 AMD switch.
Again, that AMD CPUs don't suffer as much from the research of Intel
CPUs as Intel CPUs seems clear. You are assuming that there are less
problems in AMD CPUs. I assume that there is less research on AMD CPUs.

Maybe AMD is not hostile against reverse engineering. But you seem to
forget that they don't provide any documentation at all atm (for fam17h/
Ryzen) to write firmware. If you want to get coreboot running on Ryzen,
you better start collecting funds, maybe $500k for a kick off?

Nico

  "disable Intel hyperthreading" :
 [1] - https://news.ycombinator.com/item?id=17829790
 [2] - https://marc.info/?l=openbsd-tech&m=153504937925732&w=2
 speaker as a microphone:
 [3] -
https://security.stackexchange.com/questions/154343/can-a-speaker-be-used-a…
 [4] - https://mail.coreboot.org/pipermail/coreboot/2018-January/085979.html