[HN Gopher] First in-the-wild UEFI bootkit bypassing UEFI Secure...
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First in-the-wild UEFI bootkit bypassing UEFI Secure Boot
Author : miles
Score : 151 points
Date : 2023-03-01 17:59 UTC (5 hours ago)
(HTM) web link (www.welivesecurity.com)
(TXT) w3m dump (www.welivesecurity.com)
| AaronFriel wrote:
| Amusingly, this exploit titled BlackLotus priced at $5,000 is
| cheaper than its likely namesake, the Magic: the Gathering card
| Black Lotus.
|
| The cheapest Black Lotus cards are around $10k[1], an artist
| proof, signed Black Lotus may be worth around $800,000[2].
|
| [1]
| https://www.tcgplayer.com/search/magic/product?productLineNa...
|
| [2] https://www.rollingstone.com/product-
| recommendations/lifesty...
| AdmiralAsshat wrote:
| Well, sure. I mean, one of these things just lets you hijack
| the boot process of a fully-patched operating system. The other
| one lets you add _three mana_ to your mana pool at no cost!
|
| It's really no contest.
| AaronFriel wrote:
| You're right. One is a necessary tool for the most skilled
| actors to use against their greatest threats; the other is
| merely another vector for exploiting trusted computing
| primitives.
| megous wrote:
| So the revocation list is distributed by BIOS updates? If yes,
| then secure boot seems like a joke for most consumers.
| mjg59 wrote:
| No, revocation lists can be updated from the OS and are freely
| available from https://uefi.org/revocationlistfile
| megous wrote:
| So the OS just doesn't do it automatically?
| skozharinov wrote:
| It does. Windows ships them as part of security updates,
| Linux distributions can use fwupd.
| mjg59 wrote:
| As noted in the other comment, Linux (if running fwupd) and
| Windows support doing it automatically, but the files are
| made public so other operating systems and distributions
| can also implement that.
| [deleted]
| WhackyIdeas wrote:
| I would love to take a look at these underground hacker places to
| see what goes on and what to watch our for... I'm guessing it's
| all dark web stuff though. Are any of these forums available on
| the clear net?
| cassianoleal wrote:
| The "dark web" is one download away [0].
|
| [0] https://www.torproject.org/download/
| [deleted]
| [deleted]
| mjg59 wrote:
| This is kind of weird in that it's exploiting a vulnerability in
| the Windows bootloader, but once exploited it's pivoting to using
| shim+grub (edit: apparently it's not actually grub, it's their
| own bootloader that's just called grubx64.efi because that's what
| shim boots by default). There's no absolute requirement to do
| this, but it's presumably easier to implement their full payload
| in grub rather than getting it all running in the context of the
| Windows bootloader. This means it probably doesn't work on the
| Secured Core PCs that only ship with support for the Windows
| signing key (but also it can't be used to attack Linux systems
| that remove trust in the Windows key).
|
| This pivot means that the keys measured into PCR 7 of the TPM
| will change, which breaks the Bitlocker policy, which is
| presumably why stage 1 disables Bitlocker before exploiting the
| bootloader. This means it's also detectable using Remote
| Attestation (I think Microsoft's Device Health Attestation ought
| to notice, but haven't verified it), which is nice for all 3 of
| the people who've rolled that out.
|
| In terms of why the known vulnerable bootloaders weren't already
| revoked - I have no inside knowledge here, but my guess would be
| the impact on users with existing install media (including
| factory restore images). We've revoked a bunch of vulnerable
| Linux bootloaders, but the level of pain involved in revoking a
| Windows one is almost certainly way higher.
| AshamedCaptain wrote:
| > We've revoked a bunch of vulnerable Linux bootloaders, but
| the level of pain involved in revoking a Windows one is almost
| certainly way higher.
|
| Revoking other OSes install media en-masse is fine, but not
| Windows ?
| michaelt wrote:
| I wouldn't be surprised if 50% of Linux users already have
| Secure Boot disabled - and probably 98% of Linux users have
| the wherewithal to get into the BIOS and disable it if they
| needed to. And doing so has negligible downsides, as almost
| nobody on Linux has been fool enough to make use of the TPM.
| JohnFen wrote:
| I keep it disabled on all my machines. I can secure my
| machine using whole disk encryption, and secure boot is
| just a royal pain in the butt.
|
| I recognize that I am decreasing my security a bit, but
| that tradeoff is worth it to me.
| candiddevmike wrote:
| TPM support on Linux (for drive encryption) is getting
| better with tools like clevis. Additionally, systemd can do
| a ton of cool things with TPM, and projects like dm-verity
| can make linux's boot process more locked down than
| Windows.
|
| I personally will always use a passphrase for device
| encryption.
| throwaway742 wrote:
| Disabling it is always one of the first things I do with a
| new system even if it is running windows. It's probably not
| rational, but I hate the whole concept of a TPM.
| cryptonector wrote:
| > [...] almost nobody on Linux has been fool enough to make
| use of the TPM.
|
| Can you elaborate as to what is foolish about using a TPM?
| ghostpepper wrote:
| Not the OP but just anecdotally, last time I looked into
| enabling secure boot on my X1 Carbon there was an
| advisory from Lenovo that enrolling your own keys made it
| possible to brick the machine
|
| https://wiki.archlinux.org/title/Lenovo_ThinkPad_X1_Carbo
| n_(...
| mjg59 wrote:
| That's related to Secure Boot, not the TPM
| privacyking wrote:
| That's only if you fail to enroll the Lenovo hardware
| firmware images
| mjg59 wrote:
| Oh, I think the vulnerable Windows images should also be
| revoked, but pretending that the damage caused is equivalent
| isn't realistic. Systems have shipped with factory restore
| partitions that still contain old bootloaders - this
| revocation update would stop all of those working, which is
| going to be a significant support burden for all those
| manufacturers.
| LoganDark wrote:
| You can't exactly swap out the bootloader on Windows install
| media. You can on Linux because it's a modular component of
| the system, but on Windows the entire OS + kernel +
| bootloader is a single image.
| [deleted]
| Sunspark wrote:
| Linux users tend to be their own support. Windows users are
| commercial support which is $.
| amluto wrote:
| I continue to dislike the PCR 7 mechanism. Remote attestation,
| etc should have a means to accept or reject specific
| bootloaders, not just their signing keys.
|
| </grump>
| mjg59 wrote:
| That information is still in PCR 4, the reason for just
| encoding the policy and signing key in PCR 7 is that it
| remains stable even if you update the bootloader.
| [deleted]
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(page generated 2023-03-01 23:00 UTC)