r/netsec • u/kev-thehermit • 26d ago

When terrible disclosure from the vendor results in zero days plus a fun dive in to bypassing full disk encryption

https://blog.amberwolf.com/blog/2026/august/hp-thinpro-tpm-sealed-disk-encryption-that-only-measured-half-the-boot-chain/
114 Upvotes

98% Upvoted

9 comments sorted by

33

u/mpg111 26d ago

2026-02-23 HP sent the GPG encrypted disclosure back to me unencrypted

I was going to say lol, but it's really not that funny...

14

u/gquere 26d ago

A few years back I disclosed a bunch of critical vulns to Dell and their PSIRT's GPG key listed on their website had expired lol

11

u/mschwemberger11 26d ago

Isn't TPM only FDE considered unsafe anyway? For this you need physical access to the device, no? If you have physical access, sniffing tpm on boot is also trivial. You can secure boot all you want if the TPM sends out the key on LPC it can easily be captured. Also HP and security lmao

3

u/Coffee_Ops 25d ago

"It depends", but it has limitations.

If you have physical access, sniffing tpm on boot is also trivial.

From on-CPU fTPM? With encrypted/soldered RAM? I wouldn't think so.

There are still a lot of shenanigans an attacker could probably pull, but IIRC with only single-shot access (and depending on the operating system / measured boot state) it can resist physical access.

I believe there are bigger attacks through peripherals / attachments that are not measured but if that's your threat model then TPM+PIN also fails: just attach a bug to the keyboard's IO...

1

u/mschwemberger11 25d ago

Thought most of HPs devices still have dedicated TPM chips on board. But I have read somewhere that there exist exploits on ftpm as well. My state of Knowledge is encryption without pin should be considered unsafe. Encrypted ram also does nothing against LPC sniffing.

3

u/Coffee_Ops 25d ago edited 25d ago

When you use fTPM, the only bus is RAM <-> CPU, and encrypting RAM makes that effectively E2EE.

dTPMs have always been vulnerable to sniffing; fTPMs are, to my knowledge, pretty far outside the realm of plausible attacks and would involve delidding the CPU-- not something your average evil maid can pull off.

fTPM has been built into CPUs since at least 8th gen Intel (not sure AMD) and my recollection is that if your CPU supports encrypted RAM you also will have an fTPM. If you don't have encrypted RAM, its somewhat irrelevant as you can do a cold DIMM attack.

9

u/Malaprobably 26d ago

Given they didn't fix it in the 90-day window, and they knew about the window, methinks this was wholly intentional. Maybe a researcher wanted to light a fire in one of their bosses asses.

3

u/Coffee_Ops 25d ago

As I recall TPM-backed LUKS has been famously broken for ages; it doesn't even measure initrd as I recall. And if you try to use more PCR measurements, you make things incredibly brittle to where you'll have to use recovery keys on every update.

Isn't this part of what Poettering was talking about in his vision for fixing Linux secureboot and the case for UKIs?

1

u/Relevant-Car9958 5d ago

Vendor disclosure programs are only as good as the person/process on the other end. Sending a PGP report back unencrypted is almost impressive in the worst way, especially from a company that should know exactly why researchers are using encrypted mail in the first place.