
Mac OS High Sierra automatically checks EFI firmware each week - mbgaxyz
https://eclecticlight.co/2017/09/24/high-sierra-automatically-checks-efi-firmware-each-week/
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cynix
If the EFI firmware has been modified by a rootkit, surely it'll try to hide
itself and present "valid" firmware data to the OS, and thus avoiding
detection by this tool, right?

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amluto
A TPM can be used to avoid this -- the firmware can update PCRs with its own
hash early enough that malware can't run.

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magnat
Surely a firmware rootkit can prevent eficheck from accessing TPM altogether
or force the program to report everything is OK. If eficheck is not unsealing
secrets stored in TPM, what would be benefits of checking PCRs?

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bdonlan
That depends - it's possible to have a first stage bootloader in mask or OTP
ROM that hashes the firmware before passing off control. No idea if Macs do
this though.

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magnat
Why bother with providing userland tool then? If you have complete chain of
trust, the tool can just MsgBox("Everything's OK") because you wouldn't be
able to boot OS if EFI didn't pass the check. If you don't have a chain of
trust, the tool can be easily tampered with by the rootkit. Either way - it
serves no real security purpose other than perhaps reassuring user or
detecting obsolete, existing rootkits.

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c0nsumer
I'd really like to know the mechanism used for this. Currently Apple has
issues with macOS firmware updates done on networks with proxies.

Specifically, the Touchbar updates have no concept of proxies and will cause
the machine to appear to hang for a while (~20 minutes, IIRC) on boot when
they can't directly phone home. This is a big problem on some large corporate
networks.

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digitalsushi
i work at a fortune 50, had a mac mini that got borked... they said "will this
fit in your backpack? can you sneak it home to fix it?" yup, sure could. kinda
sad.

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AgentEpsilon
Personally, I use rEFInd to manage my MBP's OS installs. I know that it
installs itself to the EFI partition, but would that cause this service to
identify an insecure/corrupted/whatever EFI?

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kogir
rEFInd is just an EFI application. It doesn't replace the system EFI firmware
(which runs before, launches, and provides services to rEFInd).

As to whether or not this tool will flag it, I suppose you'll find out shorty
after installing High Sierra.

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crishoj
This feature was the subject of a talk at Ekoparty:
[https://www.ekoparty.org/charla.php?id=798](https://www.ekoparty.org/charla.php?id=798)

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misterdata
macOS Sierra already periodically checks the firmware for Thunderbolt Ethernet
adapters:

/usr/libexec/firmwarecheckers/ethcheck/ethcheck:

usage: ethcheck: [ --save -b <eth nvram bin output file> ] [ --integrity-check
[ -b <eth nvram bin input file> ] ] [ --show-hashes [ -b <eth nvram bin input
file> ] ] [ --cleanup -b <eth nvram bin input/output file> [ --send-change-in-
firmware enable/disable] [ --version]

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cmurf
So the firmware could be compromised for up to a week, allowing a malicious
3rd party that long to exfiltrate whatever they want? If the problem of fake
firmware is real, why not check it at every boot? Why not implement both UEFI
Secure Boot, and also Measured Boot?

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burntrelish1273
HIDS/HIPS has always been problematic because of chicken-and-egg
rootkitability (ie a rooted box scanning itself is tantamount to worthless),
also clean image scanning has been extremely inconvenient. It would make more
sense to have an secure OS in ROM that runs at boot and at various times which
bypasses the installed OS and drivers, and can scan firmwares, microcode on
various buses and critical files. Basically, hardware TripWire, but with an
authoritative signatures database. And certainly, UEFI Secure/Measured Boot is
complementary for defense-in-depth.

Also, it would be helpful if PCIe, HDMI, USB, Thunderbolt, etc. drivers ask
permission of the user before automatically connecting devices inserted into
PCs... basically a peripheral "firewall." There are too many buses that are
happy to give up the FSB and PCIe-side without authorization. Hell, it would
be even better if buses used some sort of minimal-but-essential PKI and
encryption.

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colejohnson66
> It would make more sense to have an secure OS in ROM that runs at boot and
> at various times which bypasses the installed OS and drivers, and can scan
> firmwares, microcode on various buses and critical files.

Isn’t that what Intel ME is? The only difference being we don’t know what
exactly it does?

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geuis
What are the potential impacts to the hackintosh community? I haven’t powered
up my old one in a while and it’s tremedously out of date.

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gervase
Since this appears to be strictly a notification for now, I expect Hackintosh
users will see the message once, choose "Don't Send", and never see it again.
According to the article, once you've made your choice, that choice is
remembered between reboots.

Long term, I could potentially see this being modified to pop up every time on
startup, as a "We know what you're doing, and we don't like it" signal to the
Hackintosh users out there. However, that seems like kind of a dick move for
such a small (and passionate) fraction of your market.

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lostlogin
Tried to use iMessage on a hackintosh recently. Don’t do this, and don’t let
anyone you know do it. Watching your services get switched off in a cascade is
rather awful.

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vogon_laureate
Did you generate a valid serial number / model combo first?

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lostlogin
It wasn’t my machine but I think that had been done. It thought it was a nice
new iMac.

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ballenf
I wonder if there'll be any transparency around the database of known 'good'
firmwares? For example, could a state actor force inclusion of a 'bad'
firmware in the list? That's rhetorical, but the question is wouldn't it be
better if end users could have visibility into the list of valid hashes? A
count of the prevelance of each hash would pretty quickly highlight any with
only a handful of appearances in the wild.

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youdontknowtho
I'm a little surprised by how little chest thumping there is about apple
collecting telemetry like this. I expected this to be full of people saying
that you should only use tails and tor from a faraday cage.

Pleasantly surprised.

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Operyl
Uh. It’s not heavily sensitive information, has a show details button, and
honors user choices. Why would there be any anger?

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youdontknowtho
because people aren't rational about this subject. on this site their are
people with intense maximalist positions on privacy. they can be kind of
shrill.

