TPM GPIO fail: How bad OEM firmware ruins Intel TPM security (opens in new tab)

Funnily enough, in TPM 2.0 there's way around MITM attacks like that - you can establish encrypted connection between TPM and CPU, which outside first-time configuration (which should happen in controlled environment anyway) should provide reasonable roadblock to successful MITM attack.

But CPU-side software needs to use it, and without default well-known keys...

BUS interposers are trivially defeated with encrypted sessions and a PIN.

Bitlocker is traditionally the implementation susceptible for this attack, but for that I'll just defer to Chris Fenner.

https://www.dlp.rip/tpm-genie

> Of course, that doesn't mean you're protected against attackers who have physical access to the machine; they can simply install a keylogger.

How would that attack work if someone stole my Ryzen powered laptop with full disk encryption, TPM2.0 and secure boot with firmware password enabled?

and by recent, TPM was external last in gen 8 of intels, so this attack works on cpus released last in October 2017. That's almost 7 years ago. Most organizations have a 3-5 year replacement schedule.

Discrete (i.e., chip) TPMs (dTPMs) are slow. They are way too slow to use as HSMs.

Firmware TPMs (fTPMs) are faster, but I doubt they're really fast enough to use as an HSM.

There are TPM APIs for Java, so you can do this, but it's not surprising that the Java keystore providers lack builtin support because of the performance issues.

Ideally fTPMs should come with EKcerts and platform certificates and they would be very fast and as secure as (more so than) dTPMs. Then using fTPMs as HSMs might take off.

Totally off-topic: You could always write a JNI shim to a C/C++-compatible API, if you know what OS it's running on.

I know it's awful, but probably not as awful as a hardcoded passphrase.

its meant for secureboot, but i suppose the rest of the platform, built usually by other ppl than ones who designed the TPM, needs to also implement it correctly. an d as this article shows, this is not an easy feat. (this attack seems silly but it's really clever tbh. good inspired idea likely based in lots of domain expertise). - if you can protect the boot-chain with secureboot, what you can do for your private key, what for example AV vendors do, is have a (efi?)driver that contains the certificate, which is a boot-driver protected by secure-boot. - for windows this might require Microsoft cooperation to assign you a driver level so other stuff can't disable it (otherwise it's still tricky and possible to get around your protections likely). (windows -> process protection light / telam drivers). Optionally you could also have the certificate provided by an EFI applcation somehow that's signed / secured by secureboot. (could drop it on disk somewhere, efi partition is easily accessible...).

If the chain is protected by the tpm, this method if implemented correctly through the whole chain should protect your cert and pkey.

that being said _should_ is the keyword,. i dont think any platform really managed to escape all attacks, though a lot in this area do need hw access (the tweezers previously implemented by the author :)).

It's used to establish a root of trust. If your operating system is modified, it fails to validate and the TPM doesn't release the secrets. If your BIOS is modified, it fails to validate and the TPM doesn't release the secrets. If your CPU is modified, it can tell the TPM what it wants to hear and get the secrets even if the BIOS or OS is modified.

For some people, this is a useful increase in security. Those people set up their own TPM according to their own rules. For the rest of us, who had one forced on us by Microsoft, it's just more anti-right-to-repair.

Each TPM having an unique certificate, you may use that to trace a specific machine to a specific user. Game developers could use that to ban (toxic) players from an online service, for example.

Real world example of a use of TPMs (outside of bootloaders) that has a positive effect on users: https://blog.chromium.org/2024/04/fighting-cookie-theft-usin...

What about systemd credentials?

Not the only uses, but certainly all of the widespread implementations of trusted hardware just haven't been able to avoid that temptation of privileging the manufacturer while securing against the user themselves. Every little hole is another setback that keeps the designers/implementers working on this layer instead of starting to tighten the noose on the next one.

TPMs are a cryptographic coprocessor with added platform state attestation functionality. That can for example be used locally for secure secret storage that is only available in certain platform states, or remotely to certify the state of a device trying to access a corporate network.

Of course TPMs can be (ab)used for DRM, but the same property in general to many ideas in cryptography. We still don't say AES or RSA are tools designed to restrict your rights.

In reality TPMs are almost always used to (attempt to) protect the user's data over restricting them.

I would argue that the discrete chip variation of them aren't very good at this (and even less good at DRM), but a lousy implementation doesn't mean the concept is bad. (As Foxboron mentioned earlier in this thread, discrete TPMs can still act as reasonably good "discounted" SmartCards, but they are bad at platforms state attestation.)

In fact I would have much preferred if the industry embraced the measured boot idea more instead of mainly pushing stricter verified boot schemes.

Such an entrant exists. It's called Libreboot.

But this page is a no-tweezer hack; by reprogramming the GPIO pin that drives the reset; this is software only so more of a problem.

I have to believe there are hardware engineers out there who know locking people out of their devices is essentially bad, and so they leave in those tweezer based attacks on purpose.

Although, designing against physical attacks is very difficult, so I guess there’s no need to imagine a good-hearted conspiracy of conscientious hardware folks.

No.

But on essentially all existing UEFI systems you can trivially overwrite the "db" keystore in flash and install anything you please.

Also most (all?) UEFI systems are not locked to Windows and allow customizing the keystore via the firmware console interface anyhow.

The CPUs and OSs (other than Windows 11) support operation without any TPM.

So either the pin is configurable, or you've wasted a pin that could otherwise be used for decorating the motherboard with RGB LEDs.

Also, the pin layout has to be standardized by the socket specification (eg "LGA 2011"), which may have to retain compatibility for a decade or more. This strongly favors defining reconfigurable over fixed-function pins.