[edk2-devel] [GSoC proposal] Secure Image Loader

Tue Apr 13 18:08:49 UTC 2021

Hi Nate,

Yes.  A FixedAtBuild PCD or a FeatureFlag PCD is one way.  However, that approach does add some risk to the existing PE/COFF loader functionality.

My suggestion was to add a new library instance as a peer to the existing library instance.

I believe Marvin is also suggesting some changes to the PE/COFF Library Class APIs, which would be more challenging to support old and news.  

I agree with Andrew that the proposed changes to the PE/COFF Library Class need to be reviewed to see if there is a path to support old and new.

Mike

> -----Original Message-----
> From: Desimone, Nathaniel L <nathaniel.l.desimone at intel.com>
> Sent: Tuesday, April 13, 2021 11:05 AM
> To: Marvin Häuser <mhaeuser at posteo.de>
> Cc: Kinney, Michael D <michael.d.kinney at intel.com>; devel at edk2.groups.io; Laszlo Ersek <lersek at redhat.com>; Andrew Fish
> <afish at apple.com>
> Subject: RE: [edk2-devel] [GSoC proposal] Secure Image Loader
> 
> Hi Marvin,
> 
> What Mike and I were thinking is having a FixedAtBuildPcd which chooses whether to use the new loader or the old loader at
> compile time. We were also thinking the same thing of shimming the old loader into the new interface. I completely agree
> with you that it is unlikely the new loader is "broken"... it is more likely that broken images exist out in the world
> somewhere and that we won't know that they are broken until someone tries to build their system's firmware with the new
> loader included. Once the broken images are found, it can take some time to get them fixed. A lot of times they come from
> outside vendors and the source code for those binaries is not readily available. Because of that, there may be a need to
> fallback to the old loader in the interim period while a fixed binary is being acquired.
> 
> This could become very difficult for OpROMs on PCIe add-in cards since they are stored on a separate device rom and most
> of the time are completely non-upgradable. We should think about how we can handle the case where we find an old graphics
> or network card built in 2014 that has a UEFI OpROM that contains a broken PE/COFF header which cannot be fixed.
> 
> Thanks,
> Nate
> 
> -----Original Message-----
> From: Marvin Häuser <mhaeuser at posteo.de>
> Sent: Tuesday, April 13, 2021 12:32 AM
> To: Desimone, Nathaniel L <nathaniel.l.desimone at intel.com>
> Cc: Kinney, Michael D <michael.d.kinney at intel.com>; devel at edk2.groups.io; Laszlo Ersek <lersek at redhat.com>; Andrew Fish
> <afish at apple.com>
> Subject: Re: [edk2-devel] [GSoC proposal] Secure Image Loader
> 
> Hey Mike,
> Hey Nate,
> 
> I'm not 100 % sure I get what you mean. The interfaces of the two solutions are not compatible (however I could write
> wrapper code to shim the old into the new I suppose?), so on-the-fly switching between the two would be inconvenient. I do
> plan to keep the old library around and guard it with the deprecated interfaces macro, for out-of-tree code, however. The
> new library interfaces will probably be something like PeCoffLib2, PeCoffDebugLib2, maybe more.
> 
> I'm also not sure what on-the-fly switching would accomplish, as testing with the old loader allows broken images to be
> loaded, i.e. just because something "works" with the old code but not the new, it doesn't mean that the new code is
> broken.
> 
> Instead of debugging with two libraries, I rather want to make sure this thing is rock-solid before even sending out the
> patches. For this I would like to build a small EFI file database to parse and load from userland, checking for image
> acceptance and memory safety. This would include several versions of Windows and macOS bootloaders, Option ROMs (NVIDIA
> and AMD GOP, iPXE), tools (memtest), and so on. If you have anything you want to have especially tested, please let me
> know.
> 
> Best regards,
> Marvin
> 
> 13.04.2021 02:56:22 Desimone, Nathaniel L <nathaniel.l.desimone at intel.com>:
> 
> > Hi Marvin,
> >
> > I agree with Mike K that having both the new strict loader and the old loader co-exist for some time may be the best
> option. That will give the ecosystem time to test the new loader and correct any issues that arise from its introduction.
> >
> > Best Regards,
> > Nate
> >
> > -----Original Message-----
> > From: Kinney, Michael D <michael.d.kinney at intel.com>
> > Sent: Monday, April 12, 2021 5:20 PM
> > To: Marvin Häuser <mhaeuser at posteo.de>; devel at edk2.groups.io;
> > Desimone, Nathaniel L <nathaniel.l.desimone at intel.com>; Laszlo Ersek
> > <lersek at redhat.com>; Andrew Fish <afish at apple.com>; Kinney, Michael D
> > <michael.d.kinney at intel.com>
> > Subject: RE: [edk2-devel] [GSoC proposal] Secure Image Loader
> >
> > Hi Marvin,
> >
> > If it has not already been considered, one option is to submit a new instance of the PE/COFF Library, so both the
> existing one and the new one are available to the ecosystem.
> >
> > This allows you to be successful in submitting code outlined in your proposal and gives the ecosystem time to evaluate
> and decide when/if to switch from the old to the new.
> >
> > Mike
> >
> >> -----Original Message-----
> >> From: Marvin Häuser <mhaeuser at posteo.de>
> >> Sent: Monday, April 12, 2021 10:22 AM
> >> To: devel at edk2.groups.io; Desimone, Nathaniel L
> >> <nathaniel.l.desimone at intel.com>; Laszlo Ersek <lersek at redhat.com>;
> >> Andrew Fish <afish at apple.com>; Kinney, Michael D
> >> <michael.d.kinney at intel.com>
> >> Subject: Re: [edk2-devel] [GSoC proposal] Secure Image Loader
> >>
> >> Good day Nate,
> >>
> >> As you seem to be mostly in charge of the GSoC side of things, I
> >> direct this at you, but of course everyone is welcome to comment.
> >>
> >> I think I finished my first round of investigations just in time for
> >> the deadline. You can find a list of BZs attached[1]. Please note
> >> that
> >> 1) some are declared security issues and may not be publicly
> >> accessible, and 2) that this list is far from complete. I only added
> >> items that are
> >> a) not implicitly fixed by "simply" deploying the new Image Loader
> >> (*some* important prerequisites are listed), and b) I am confident
> >> are actual issues (or things to consider) I believe to know how to approach.
> >>
> >> I have taken notes about more things, e.g. the existence of the
> >> security architectural protocols, which I could not find a rationale
> >> for. I can prepare something for this matter, but it really needs an
> >> active discussion with some of the core people. I'm not sure delayed
> >> e-mail discussion is going to be enough, but there is an official IRC
> >> I suppose. :) I hope we can work something out for this.
> >>
> >> I also hope this makes it clearer why I don't believe that we need to
> >> "fill" 10 weeks, but rather the opposite. This is not a matter of
> >> replacing a library instance, but the whole surrounding ecosystem
> >> needs to follow for the changes to make sense. And as I tried to make
> >> clear in my discussion with Michael Brown, I am not keen on
> >> preserving backwards-compatibility with platform code (i.e. PEI, DXE,
> >> things we consider "internal"), as most of it should be controlled by
> >> EDK II already. This of course does *not* include user code (OROMs,
> >> bootloaders, ...), for which I want to provide the *option* to lock
> >> some of them out for security, but with sane defaults that will
> >> ensure good compatibility.
> >>
> >> I'd like to thank Michael Brown for his cooperation and support,
> >> because we recently landed changes in iPXE to allow for the strictest
> >> image format and permission constraints currently possible[2].
> >>
> >> I will have to rework the submitted proposal to reflect the new
> >> knowledge. To be honest, seeing how the BZs kept rolling in, I am not
> >> convinced an amazing amount of mainlining can be accomplished during
> >> the
> >> 10 weeks. It may have to suffice to have a publicly accessible
> >> prototype (e.g. OVMF) and a subset of the planned patches on the list.
> >> I hope you can manage to provide some feedback before the deadline passes tomorrow.
> >>
> >> Thank you in advance!
> >>
> >> Best regards,
> >> Marvin
> >>
> >> [1]
> >> https://bugzilla.tianocore.org/show_bug.cgi?id=3315
> >> https://bugzilla.tianocore.org/show_bug.cgi?id=3316
> >> https://bugzilla.tianocore.org/show_bug.cgi?id=3317
> >> https://bugzilla.tianocore.org/show_bug.cgi?id=3318
> >> https://bugzilla.tianocore.org/show_bug.cgi?id=3319
> >> https://bugzilla.tianocore.org/show_bug.cgi?id=3320
> >> https://bugzilla.tianocore.org/show_bug.cgi?id=3321
> >> https://bugzilla.tianocore.org/show_bug.cgi?id=3322
> >> https://bugzilla.tianocore.org/show_bug.cgi?id=3323
> >> https://bugzilla.tianocore.org/show_bug.cgi?id=3324
> >> https://bugzilla.tianocore.org/show_bug.cgi?id=3326
> >> https://bugzilla.tianocore.org/show_bug.cgi?id=3327
> >> https://bugzilla.tianocore.org/show_bug.cgi?id=3328
> >> https://bugzilla.tianocore.org/show_bug.cgi?id=3329
> >> https://bugzilla.tianocore.org/show_bug.cgi?id=3330
> >> https://bugzilla.tianocore.org/show_bug.cgi?id=3331
> >>
> >> [2] https://github.com/ipxe/ipxe/pull/313
> >>
> >> On 06.04.21 11:41, Nate DeSimone wrote:
> >>> Hi Marvin,
> >>>
> >>> Great to meet you and welcome back! Glad you hear you are
> >>> interested! Completing a formal verification of a PE/COFF
> >> loader is certainly impressive. Was this done with some sort of
> >> automated theorem proving? It would seem a rather arduous task doing
> >> an inductive proof for an algorithm like that by hand! I completely agree with you that getting a formally verified
> PE/COFF loader into mainline is undoubtably valuable and would pay security dividends for years to come.
> >>>
> >>> Admittedly, this is an area of computer science that I don't have a
> >>> great deal of experience with. The furthest I have
> >> gone on this topic is writing out proofs for simple algorithms on
> >> exams in my Algorithms class in college. Regardless you have a much
> >> better idea of what the current status is of the work that you and
> >> Vitaly have done. I guess my only question is do you think there is
> >> sufficient work remaining to fill the 10 week GSoC development window? Certainly we can use some of that time to
> perform the code reviews you mention and write up formal ECRs for the UEFI spec changes that you believe are needed.
> >>>
> >>> Thank you for sending the application and alerting us to the great
> >>> work you and Vitaly have done! I'll read your paper
> >> more closely and come back with any questions I still have.
> >>>
> >>> With Best Regards,
> >>> Nate
> >>>
> >>>> -----Original Message-----
> >>>> From: devel at edk2.groups.io <devel at edk2.groups.io> On Behalf Of
> >>>> Marvin Häuser
> >>>> Sent: Sunday, April 4, 2021 4:02 PM
> >>>> To: devel at edk2.groups.io; Laszlo Ersek <lersek at redhat.com>; Andrew
> >>>> Fish <afish at apple.com>; Kinney, Michael D
> >>>> <michael.d.kinney at intel.com>
> >>>> Subject: [edk2-devel] [GSoC proposal] Secure Image Loader
> >>>>
> >>>> Good day everyone,
> >>>>
> >>>> I'll keep the introduction brief because I've been around for a
> >>>> while now. :) I'm Marvin Häuser, a third-year Computer Science
> >>>> student from TU Kaiserslautern, Germany. Late last year, my
> >>>> colleague Vitaly from ISP RAS and me introduced a formally verified
> >>>> Image Loader for UEFI usage at ISP RAS Open[1] due to various
> >>>> defects we outlined in the corresponding paper. Thank you once again Laszlo for your *incredible* review work on the
> publication part.
> >>>>
> >>>> I now want to make an effort to mainline it, preferably as part of
> >>>> the current Google Summer of Code event. To be clear, my internship
> >>>> at ISP RAS has concluded, and while Vitaly will be available for
> >>>> design discussion, he has other priorities at the moment and the
> >>>> practical part will be on me. I have previously submitted a proposal via the GSoC website for your review.
> >>>>
> >>>> There are many things to consider:
> >>>> 1. The Image Loader is a core component, and there needs to be a
> >>>> significant level of quality and security assurance.
> >>>> 2. Being consumed by many packages, the proposed patch set will
> >>>> take a lot of time to review and integrate.
> >>>> 3. During my initial exploration, I discovered defective PPIs and protocols (e.g.
> >>>> returning data with no corresponding size) originating from the
> >>>> UEFI PI and UEFI specifications. Changes need to be discussed,
> >>>> settled on, and submitted to the UEFI Forum.
> >>>> 4. Some UEFI APIs like the Security Architecture protocols are
> >>>> inconveniently abstract, see 5.
> >>>> 5. Some of the current code does not use the existing context, or
> >>>> accesses it outside of the exposed APIs. The control flow of the
> >>>> dispatchers may need to be adapted to make the context available to appropriate APIs.
> >>>>
> >>>> But obviously there are not only unpleasant considerations:
> >>>> A. The Image Loader is mostly formally verified, and only very few
> >>>> changes will be required from the last proven state. This gives a
> >>>> lot of trust in its correctness and safety.
> >>>> B. All outlined defects that are of critical nature have been fixed successfully.
> >>>> C. The Image Loader has been tested with real-world code loading
> >>>> real-world OSes on thousands of machines in the past few months,
> >>>> including rejecting malformed images (configurable by PCD).
> >>>> D. The new APIs will centralise everything PE, reducing code
> >>>> duplication and potentially unsafe operations.
> >>>> E. Centralising and reduced parse duplication may improve overall
> >>>> boot performance.
> >>>> F. The code has been coverage-tested to not contain dead code.
> >>>> G. The code has been fuzz-tested including sanitizers to not invoke
> >>>> undefined behaviour.
> >>>> H. I already managed to identify a malformed image in OVMF with its
> >>>> help (incorrectly reported section alignment of an Intel IPXE
> >>>> driver). A fix will be submitted shortly.
> >>>> I. I plan to support PE section permissions, allowing for read-only
> >>>> data segments when enabled.
> >>>>
> >>>> There are likely more points for both lists, but I hope this gives
> >>>> a decent starting point for discussion. What are your thoughts on
> >>>> the matter? I strongly encourage everyone to read the section
> >>>> regarding defects of our publication[2] to better understand the
> >>>> motivation. The vague points above can of course be elaborated in due time, as you see fit.
> >>>>
> >>>> Thank you for your time!
> >>>>
> >>>> Best regards,
> >>>> Marvin
> >>>>
> >>>>
> >>>> [1] https://github.com/mhaeuser/ISPRASOpen-SecurePE
> >>>> [2] https://arxiv.org/pdf/2012.05471.pdf
> >>>>
> >>>>
> >>>>
> >>>>
> >>>
> >>>
> >>> 
> >>>
> >>>

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